Experimental and numerical investigation of double lap adhesively bonded joints composed of KFRP and SDRP subjected to compressive loads

Experimental and numerical investigation of double lap adhesively bonded joints composed of KFRP and SDRP subjected to compressive loads | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Experimental and numerical investigation of double lap adhesively bonded joints composed of KFRP and SDRP subjected to compressive loads Adole Michael Adole, Iorwuese Anum, Umar Abdullahi, Namala Amuga Keftin This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-5836800/v1 This work is licensed under a CC BY 4.0 License Status: Under Revision Version 1 posted 2 You are reading this latest preprint version Abstract Natural fiber-based polymeric composites are widely used in a wide range of engineering applications, therefore a complete understanding of the behavior of these materials' adhesively bonded joints is required to ensure their efficiency, safety, and dependability. The single lap joint has garnered a lot of attention, but the double lap joint arrangement has received very little attention. This study aims to look into the bond performance of Kenaf Fiber Reinforced Polymer (KFRP) and Sawdust Reinforced Polymer (SDRP) utilizing the Double Lap Joint (DLJ) arrangement. To accomplish this, the kenaf fiber-polyester adherend was manufactured in a unidirectional pattern with a fiber weight fraction of 40%, while the sawdust-polyester adherend was made in a random pattern with a fiber weight fraction of 20%. The DLS joints were made with various joint geometrics, polyester adhesive as the bond material, and direct vertical compression load was applied. Finite element modelling was used to check and validate the laboratory data. It was discovered that increasing the lap length improves the load support capability of the adhesive joints while decreasing joint shear strength. The finite element results were consistent with the laboratory data, and the utilization of KFRP and SDRP in bonded adhesive assemblies showed promise for structural applications. Kenaf fiber sawdust polyester adhesive bio-composites adhesive bonded joint FEM Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 Figure 14 Figure 15 Figure 16 Figure 17 Figure 18 Figure 19 Figure 20 Figure 21 Figure 22 Figure 23 Figure 24 Figure 25 Figure 26 Figure 27 1 Introduction Due to the widespread use of fiber-reinforced polymer composite materials in various engineering fields, particularly civil structures, traditional mechanical joints are gradually being replaced by adhesively bonded joints due to their higher connection efficiency, more uniform stress fields, corrosion resistance, and lower weight increase [ 1 , 2 ]. Adhesively bonded joints not only provide a smoother surface for structural purposes but also improve fatigue life [ 3 ]. Therefore, adhesively bonded joints are increasingly utilized due to their advantages over mechanical fastening joints. Load transfer between composite parts is more uniformly performed across a larger area, and fastening holes and fasteners, which represent a factor of stress concentration and weight increase in the structures, are not required [ 4 , 5 ]. On the other hand, adhesively bonded joints have some disadvantages. They are difficult to disassemble for inspection, and the bonding strength is sensitive to environmental factors such as temperature and humidity. In addition, these joints require surface treatment of the adherends to strengthen the adhesive bonding. Accordingly, extensive and systematic studies on the failure and strength of composite bonded joints are needed for safe and reliable designs [ 6 ]. Secondly, the progressive weight transfer between adherends and the rotation of adherents in the presence of asymmetric load cause stress concentrations to form at adhesive joints along the geometry. One of the geometries most impacted in this situation is the single-lap joint arrangement, which bends under load because of asymmetry and causes high peel stresses at the over-lap ends. The double-lap joint and other geometries are less affected by peel strains [ 7 ]. The key components that affect the integrity of adhesive joints—parent adherend thickness, adhesive thickness, bonding length, bonding width, surface preparation, and geometric modifications that reduce stress concentrations—have been extensively studied [ 8 , 9 , 10 , 11 , 12 ]. On the other hand, because of their many appealing qualities, including their low cost and density, natural fiber composites have drawn interest and uses, including in the building sector [ 7 ]. To ascertain if it is feasible to link cured sections of a structure, repair them, or attach components during the construction process (for instance, because of challenging geometries), it is crucial to look into adhesive couplings between these materials. For several reasons, including lower density, less machine wear during fabrication, fewer health risks, biodegradability, availability from natural sources, and most importantly, lower cost. Natural fibers like kenaf, wood, sisal, flax henequen, jute, coconut, and palm are currently being considered as a replacement for synthetic fibers like glass, aramid, and carbon in composites [ 13 , 14 , 15 ]. Additionally, because natural fibers bend during manufacture rather than break, they offer greater design versatility. However, they have a high moisture absorption rate and low wettability for particular resins [ 8 ]. By preventing moisture absorption, mercerization can help with this issue by strengthening the fiber-matrix bonding relationship and increasing the amount of cellulose visible on the natural fiber surface [ 16 ]. Kenaf as a natural fiber, is becoming more and more prevalent because of environmental concerns and its exceptional qualities in composites, and this is shown in numerous studies [ 16 , 17 , 18 , 19 ]. Kenaf was determined to be significantly more abundant and competitively priced in the appropriate form compared to other types of natural fiber materials [ 20 , 21 ]. Kenaf was designated as commercial kenaf because of its potential as a raw material for a wide range of goods in the manufacturing and industrial sectors [ 20 , 21 ]. Above all, kenaf, like most other bio-fibers, has excellent mechanical properties, can be recycled easily, and has a low price and low density [ 22 , 23 ]. Kenaf is a very effective plant that requires minimal energy, nutrients, or chemical fertilizer to grow rapidly. Additionally, Kenaf is renowned for using less planting space and emitting more biomass per acre than any other forest tree [ 20 ]. Integration of particulate filler/flour in the form of particles of silica, alumina, solid and hollow glass particles, wood flours/chips, and carbon black in the polymer matrix leads to numerous beneficial properties. For example, impact strength, increased stiffness, reduced density, and cost reduction. Because of these characteristics, particulate composites are appropriate for use in areas where weight is desired, such as civil infrastructure. It is observed from the literature that most particulate materials are produced from non-renewable materials like synthetic materials. That is why [ 9 ] pointed out that bio-based products like wood flour can be utilized in sandwich adhesively bonded joint panels as an alternative to conventional materials, the authors argue that because synthetic materials emit carbon dioxide during their formation, they are non-renewable and non-recyclable and should be discouraged. Wood flour, on the other hand, has been the most popular choice for Wood Polymer Composite (WPC) manufacture owing to its low cost, ease of processing, and aspect ratios [ 10 ]. As waste from different wood processing activities, wood flours are typically sourced from forest product companies [ 11 ]. In a related manner, [ 15 ] stated that to broaden the advancement of bio-inspired composite materials, it is intriguing to study the blend of bio-composite adherend accompanied by a wood-based adherend to have a completely bio-sourced sandwich adhesively bonded panel. The final product will be appealing in terms of waste management; the panel can be composted after it is eventually no longer in use. It is also crucial to fully comprehend the strength and failure mechanisms of adhesively bonded joints between these materials to expand the utilization of natural fiber-reinforced composites through trustworthy design approaches. To effectively forecast the behavior of adhesive joints, numerical methods like the Finite Element Method (FEM) are necessary since the increasing complexity of joint design makes it difficult or impossible to solve adhesive joint problems using analytical approaches [ 27 ]. [ 28 ] studied double lap adhesively bonded joints and GFRP single lap supported joints: joint strength, peel stresses, and failure mechanisms. The load-displacement response and joint strength of the double lap joints were compared to those supported single lap joints to illustrate their better strength characteristics. It has been demonstrated that the joint strength improves with overlap length, but decreases with adhesive layer thickness, and is essentially independent of adhesive type. The researchers found that the double lap joints had a higher load-carrying capacity than the supported single lap joints. The influence of adherend width and overlap length on the strength performance of adhesively bonded lap joints was examined by [ 29 ]. The results showed that the bond overlap enhanced the bonded joints' displacement capacity and load-carrying capability. However, the load-carrying and displacement capacity figures were further improved by increasing the width instead of the overlap length. The peel stresses generated at the borders of the overlap length were reduced by increasing width relative to overlap, which was also observed for joints with the same bond area. Only a few papers in the literature have looked at the mechanical behaviour of adhesively bonded composite-to-composite joints. To the best of our knowledge, there is no literature on the influence of joint geometry on the characterization of strength performance of dissimilar natural fiber composite, which is the motivation for this study. The compressive strength of KFRP-to-SDRP bonded double lap joints with varying overlaps and adherend widths was tested in this research, subsequently, the compressive load-displacement curves were displayed, then failure modes and shear stress were investigated. The experimental results were then compared to the results of a finite element analysis, after that, a stress distribution in the various joints was performed 2 Methods Kenaf fiber, sawdust, and polyester polymers were the main materials utilized in this research. The kenaf fiber was sourced from the National Kenaf and Tobacco Board (NKTB), Malaysia. The sawdust was obtained from Seow Kok Hwa Enterprises SDN. BHD, a sawmill located at Kota Tinggi in Johor, Malaysia, while the unsaturated polyester polymer with the brand name polyester 2597APT waxed was supplied by Wee Tee Tong Chemical PTE LTD from Singapore. The catalyst used was under the brand name Esterox MEKP also supplied by Wee Tee Tong Chemical PTE LTD from Singapore. Before usage, the kenaf fiber and sawdust were treated and processed, then stored in a cold, dry environment. 2.1Manufacturing process 2.1.1 Fabrication of kenaf fiber reinforced composite (KFRP) adherend Before fabricating the KFRP panel, the treated kenaf fiber bundles were combed with an iron comb and cut to lengths of 295 mm. Then the quantity to be utilized was calculated and weighed according to the density and volume fraction of kenaf fiber and polyester resin. 40% of the kenaf fiber was used. A mild steel mold with a dimension of 295 mm x 210 mm x 6 mm was used. A transparent plastic veil was laid into the cavity and the mold was polished with a releasing agent. A mold-releasing agent was used inside the mold for ease of removal of the final product. Consequently, using a mechanical mixer, polyester 2597APT waxed was mixed with Methyl Ethyl Ketone Peroxide (MEKP) which was the catalyst used in a ratio of 100:1 as specified by the manufacturer. The cut and combed unidirectional fibers were laid, and aligned layer by layer in the mold. Then, the mixture of polyester 2597APT waxed and MEKP was gently poured on the fiber while ensuring evenly distribution with the aid of a roller for ease and good penetration of the resin. After that, a 22 kg mild steel lid cover was gently placed on the mold and clamped to the workbench on which the mold was resting. At room temperature, the specimen was allowed to cure for 24 hours. After the curing time, the specimen panel was de-molded and post-cured in an oven at 70o C for 6 hours. Then, the panel was removed from the oven after the curing period, cleaned, and stored. Finally, the panels were machined to conform to any specimen size or shape as specified by ASTM using a bench saw and a hand-grinding machine. Some of the processes are shown in Fig. 1 . The specimens for the unidirectional longitudinal tensile test are shown in Fig. 1 (b). 2.1.2 Fabrication of sawdust reinforced composite (SDRP) adherend The SDRP panel was fabricated in a random arrangement utilizing the hand lay-up method. Before fabrication, the treated sawdust was comminuted into powder form using a Los Angeles ball mill. The sawdust in powder form was then sieved through a mesh size of 150 µm with a mechanical shaker. The required quantity of sawdust, polyester 2597APT waxed and MEKP was calculated. 20% of the sawdust volume fraction was utilized. The same procedure used for making the KFRP was employed, except that the sawdust, polyester 2597APT waxed and the MEKP were mixed continuously in a bowl with a mechanical mixer until uniformity was achieved before the mixture was poured into a mold measuring 295mm x 210mm x 8mm. The thickness varied in the various tests conducted. The top mold or die, weighing 22 kg, was then gently placed on the mold, and the mixture was allowed to cure for 24 hours at room temperature. The panel was de-molded and post-cured in an oven at 70oC for 6 hours. Subsequently, the panel was machined to conform to the ASTM standards for each test. Some of the processes are shown in Fig. 2 . 2.1.3 Fabrication of KFRP and SDRP double lap adhesive joints The lap shear joint is the most often used joint type to examine the bonding properties of structural adhesive connections; the Double Lap Shear (DLS) was used to study the adhesive joint performance in this study since it reduces bending moments. Using the hand layup process, the kenaf fiber/polyester composite (KFRP) was self-made. The materials used for KFRP fabrication are; Kenaf fiber, polyester matrix, and MEKP as a catalyst. For unidirectional KFRP fabrication, a 40% mass fraction was used. The sawdust/polyester composite was created by randomly arranging the layup by hand. Sawdust, polyester matrix, and methyl ethyl ketone peroxide (MEKP) are the components utilized. 20% of the sawdust's mass fraction was used to fabricate the SDRP. The two KFRP adherends joined with the two SDRP adherends and underwent compressive testing. The total displacement of the joint was measured. The adhesive connection had a thickness of 0.2 mm. At least three identical samples were analyzed for every case. Several failure mechanisms were observed. Using a stainless wire insert approach, the thickness of the adhesive is held consistent across all joints. The adherends are aligned with care to generate symmetrical joints. The surfaces of the KFRP and SDRP adherends were completely abraded with sandpaper before bonding to improve the adhesive bond's efficacy. It was critical to thoroughly clean all bonding surfaces. Abrading the KFRP and SDRP adherends will get rid of any possible impurity in the bond. This was accomplished by carefully cleaning the surfaces with white tissue paper and then using acetone, an organic solvent that is commercially accessible. The cleaning substance was sprayed on the abraded surfaces and then wiped away using white tissue paper. When the cleaning was finished, the adherends had reference points marked on them to help in the alignment when clamping the specimens to the workbench as shown in Fig. 3 . Polyester adhesive was used as the joint material. Specimens were clamped for 24 hours on the work table to cure. To create a solid, long-lasting bond, the adhesive bond must be post-cured in an oven. The specimens were heated for two hours to 70°C in a standard laboratory oven, as seen in Fig. 4 . The oven was turned off after that time, and the specimens were removed and allowed to cool for 24 hours. This procedure of gently cooling the joints eliminates the formation of residual stresses and guarantees that the cure is complete. Using a scraper, all extra glue on the joints was scraped away, leaving a flat, smooth, level glue coating. 3 Mechanical testing procedure 3.1 Tensile test of the KFRP adherend The tensile test was carried out in compliance with ASTM D3039/D3039-14 test standard [ 30 ]. Five coupons were fashioned out from the cured unidirectional panel in the longitudinal direction. The standard recommended a dimension of 250 mm long by 25 mm wide. The thickness for all the coupons was held at 6 mm. The longitudinal and transverse strains were measured with two stain gauges attached at the middle of the gauge area of each coupon. The test was carried out with UTM (Shimadzu) with a load cell capacity of 250KN. The coupons were continuously loaded with a steady crosshead speed of 2 mm/min until failure. The tensile strength was obtained by dividing the load all over the area of the coupon, while the tensile modulus was calculated from the slope of the initial portion of the tensile stress-strain relation curve. The Poisson ratio was obtained by dividing the transverse strain by the longitudinal strain. The tensile test setup is shown in Fig. 5 (a), while the average stress-strain relation curve is presented in Fig. 5 (b). 3.2 Tensile test of the SDRP adherend The tensile test on the SDRP core material was performed in compliance with ASTM 638 − 14 standard test (ASTM, 2014) [ 31 ]. The coupons were prepared in the form of a dog-bone shape. To manufacture the required dog-bone shape, 5 coupons were fashioned out of the SDRP panel by grinding it to the required shape. The width of the coupon at the gauge length was lessened to 25 mm and a thickness of 8 mm. Then the coupon was mounted on the 250 KN capacity UTM(Schimadzu). An extensometer of 50 mm gauge length was attached to the center of the gauge length of the coupon to record the strain. A constant crosshead speed of 1 mm/min was used to apply the tensile load. The tensile strength was obtained by dividing the load by the area, while the tensile modulus was computed from the initial slope of the stress-strain expression curve. Figure 6 (a) shows the tensile test set-up and Fig. 6 (b) shows the average stress-strain curve. 3.3 Testing methods of KFRP and SDRP double lap adhesive joint The testing method, material testing system, and relevant apparatus for joint investigation were carried out based on ASTMD905-03 (ASTM,1999) [ 32 ], which is the accepted test procedure for adhesive bond strength characteristics in shear by compression loading, and a study conducted by [ 33 ]. A universal testing machine (Tinius Olsen) with an in-store capacity of 3000 kN was used. This test was carried out at room temperature under displacement control at a constant head-speed loading rate of 1.27 mm/min up to failure. Figure 3 displays the schematic diagrams for the KFRP adherend and SDRP adherend double lap joint tests conducted in the lab. Four different overlap lengths with three different lap widths were tested according to similar research conducted by [ 33 ]. An average of three replicas was tested for each of the configurations. The test was undertaken by placing a sample on a steel plate placed on the Tinius Olsen testing machine and applying direct compression load as shown in Fig. 7 . The data were recorded every 0.5 seconds. The force was measured and also the axial displacement was measured by the stroke. The following equation was used to determine the high shear stress that the specimens experienced in the joint area during compression loading: $$\:{\tau\:}=\frac{\:{P}_{max}}{2A}$$ 1 where, \(\:\tau\:\) is the shear bond strength, \(\:P\) is the failure load, and \(\:A\) is the area of the bonded region of the DLS Joint FE Modeling. 3.4 Numerical modelling of double lab shear joint The double lap adhesive joints were numerically modeled using the finite element method. The 3D finite element models were performed using the commercial finite element package ABAQUS/Standard to analyze the stress distribution and strength of the joints. The KFRP adherend, SDRP adherend, and polyester adhesive as the joint material constitute the three components of the double lap shear joint models. Models were created in ABAQUS/Standard with the same geometric dimensions, boundary conditions, and applied load as those tested in the laboratory. Table 1. presents the lengths, widths, and joint thicknesses for all the double lap shear joints modeled. Figure 8 shows the actual model of joint A1. Table 1 Joint geometric configuration for double lap joints Joint NO. Bond overlap (mm) Bond width (mm) Joint thickness (mm) No. of Specimens A1 10 25 0.2 3 A2 15 25 0.2 3 A3 20 25 0.2 3 A4 25 25 0.2 3 B1 10 35 0.2 3 B2 15 35 0.2 3 B3 20 35 0.2 3 B4 25 35 0.2 3 C1 10 50 0.2 3 C2 15 50 0.2 3 C3 20 50 0.2 3 C4 25 50 0.2 3 To simulate the response within the adhesive joint, which is substantially thinner than the KFRP and SDRP adherents, the algorithm uses fracture mechanics, i.e. the energy required to form new surfaces. As a result, the cohesive elements, of the traction-separation law were evaluated. Figure 9 displays the traction-separation law in ABAQUS. Shear stress and peel stress in the joint might cause cohesive failure. The program employs fracture mechanics, or the energy needed to produce new surfaces, to mimic the response within the adhesive joint, which is far thinner than the KFRP and SDRP adherends. Consequently, the traction-separation law was assessed for the cohesive parts. Cohesive failure may result from the joint's shear and peel stresses. Consequently, the Quadratic Traction Damage Initiation Criterion (QUADSCRT), a mixed-mode failure criterion, was used for this investigation. The four traction-separation law damage initiation criteria of ABAQUS were used to create the mixed-mode failure criterion known as QUADSCRT. The maximum nominal stress criterion, maximum nominal strain criterion, quadratic nominal stress criterion, and quadratic nominal strain criterion are the four criteria. The material response is calculated using nominal stress to critical stress ratios for both damage criteria. \(\:{T}_{n}^{0}\) , \(\:{T}_{s}^{0}\) , \(\:{T}_{t}^{0}\) represents the critical nominal stresses where \(\:{T}_{n}\) , \(\:{T}_{s}\) , \(\:{T}_{t}\) represent current nominal stress values in pure normal mode, first shear and second shear directions, respectively. Table 2 Mechanical properties of composites [ 35 , 36 ] Property Kenaf fiber Composite Sawdust Composite Unit \(\:{\rho\:}_{f}\) 1.28 1.25 g/cm 3 E 1 21257.80 2157 MPa E 2 2864.45 2157 MPa E 3 2864.45 2157 MPa Nuf12 0.32 0.37 Nuf13 0.32 0.37 Nuf23 0.34 0.37 G 12 1736.83 787 MPa G 13 1736.83 787 MPa G 23 1068.82 787 MPa Table 3 Characteristics of the 2597APT polyester glue used in the simulation Property Value \(\:\rho\:\) (g/cm 3 ) 1.232 E m (MPa) 2079 G m (MPa) 776 V m = V 23 0.34 X m (MPa) 38 \(\:{t}_{n}^{0}\) (MPa) 54.76 \(\:{t}_{s}^{0}\) (MPa) 20.5 \(\:{t}_{t}^{0}\) (MPa) 20.5 \(\:{G}_{IC}\) (N/mm) 38 \(\:{G}_{IIC}\) (N/mm) 38 \(\:{G}_{IIIC}\) (N/mm) 38 The adhesive layer and the joint's substrates were meshed using different meshes, which were joined by tie restrictions. Translational and rotational motion, along with all other active degrees of freedom, were restricted by applying equal nodes on both sides of the connection. Finer meshes are employed because of the tension concentration in the region around the adhesive layer. Due to the stress concentration surrounding the adhesive layer, finer meshes are used. To save computation time, coarse mesh is used for locations far from the adhesive layer. As a result, the adhesive layer was made up of an 8-node three-dimensional cohesive element (COH3D8), while the KFRP and SDRP adherents were made up of 8-node linear three-dimensional hexahedral elements with decreased integration (C3D8R) as shown in Fig. 10. In general, the KFRP adherend surface with larger stiffness is considered to be the master surface. The constraint ties the SDRP adherend surface as a slave surface. The master surface has the same motion by constraining each node on the slave surface. There was no damage to the KFRP adherend-adhesive and SDRP adherend-adhesive interfaces. As a result, for the aforementioned interfaces, a perfect bond was assumed. Figure 10 shows a typical example of the model meshes. Model A1 shown in Fig. 10 has a total number of 42225 elements with 69758 nodes. Model A2 has 42525 elements with 70070 nodes while model A3 has 54925 elements with 73986 nodes. Model A4 has a total number of 55975 elements with 75078 nodes. Model B1 has a total number of 77805 elements with 89532 nodes. Model B2 has a total number of 77980 elements with 89712 nodes. Others are model B3 with 80955 elements and 92952 nodes, model B4 has a total number of 84945 elements and 97236 nodes. Model C1 has a total number of 103750 elements with 118269 nodes. Model C2 has a total number of 104000 elements and 118524 nodes. Model C3 has a total number of 104600 elements with 119138 nodes and finally, model C4 with a total of 120700 elements and 137088 nodes. The same boundary conditions were applied to all the models of the double lab joints correlating to the fixture of the specimen tested in the laboratory. The surface of the bottom ends of the models was fixed using the ‘‘’ ENCASTRE’’ option in ABAQUS with all degrees of freedom of the bottom surface constraint: (Ux = Uy = Uz = URx = URy = URz = 0). The FE models' boundary conditions, applied loads, and geometrical dimensions matched those of the experiments exactly. Except Uy ≠ 0, all degrees of freedom at the top is thus (Ux = Uz = URx = URy = URz = 0). Static and quasi-static analytic problems have been solved with ABAQUS/Standard solver. Nonlinear difficulties including geometric nonlinearity, material nonlinearity, and nonlinear boundary conditions are frequent and can make computations take a long time or even not converge. The combined failure analysis will be a huge challenge for the ABAQUS/Standard solver due to the complex material nonlinearity. The ABAQUS/Explicit solver has already been utilized for very efficient modelling of composite structural failures under quasi-static loads, despite its widespread application in transient response analysis [ 37 ]. The boundary condition and loading condition applied to the joints is shown in Fig. 11. 4 Results and discussion 4.1 Influence of joint parameters on joint strength and load-displacement response Specimens were divided into three groups with four overlap lengths: 10 mm, 15 mm, 20 mm, and 25 mm, to evaluate the effect of overlap length on the load-displacement response of double lap joints. The bond widths of the three groups examined were 25 mm, 35 mm, and 50 mm, respectively. Figures 12 , 13 , and 14 show the typical load-displacement curves for different overlap lengths with widths of 25 mm, 35 mm, and 50 mm, respectively. It is evident that the load-displacement curves for the majority of the joints exhibit nearly linear behavior at first, but this linearity was lost in the middle and then returned before failure. The curve abruptly fell when the joint's ultimate load capacity was achieved, signifying an abrupt failure. Three specimens were assessed for each group, and the figures display the load-displacement curve of the specimen whose load was closest to the average value. The figures show that increasing the overlap length in polyester adhesively bonded double lap shear joints increased their load-bearing and displacement capacity. From Table 4 , it was discovered that as the overlap length was increased, the double lap shear joints provided a higher equivalent stiffness. Furthermore, the rate at which the joints' equivalent stiffness increases as overlap length increases are 20.59%, 29.41%, 50.88% for a bond width of 25 mm, 2.65%, 13.42%, 24.39% for a bond width of 35 mm and 1.19%, 11.94%, 20.75% for bond width 50 mm respectively. Therefore, as the overlap increases, the corresponding stiffness rate tends to increase as well. Figure 15 displayed the lap shear strength as a function of bond width and overlap length. The applied load is distributed over a larger bond area, increasing the load. The increase rate of failure load with increasing overlap length is 29.95%, 47.86%, 75.21% for bond width 25 mm, 42.58%, 71.37%, 107.05% for bond width 35 mm, and 40.18%, 80.02%, and 117.83% for bond width of 50 mm respectively. However, as the overlap length of the joint increases, the connection between overlap length and joint shear strength displays an inverse relationship shown in Fig. 15 . This could be due to nonuniform stress distribution across the bond region, and increasing the overlap length reduces the center area of the joint where lower amounts of stress are sustained. The joint shear strengths with increasing overlap length saw a decrease of 13.43%, 26.00%, and 29.85% for bond width of 25 mm, 4.94%, 14.30%, 17.08% for bond width of 35 mm and 6.65%, 10.03%, 12.97% for bond width of 50 mm respectively from the baseline. A Similar pattern was obtained by [ 9 , 38 , 39 ]. The statistical determination for the overview of the KFRP-SDRP shear joint test results is presented in Table 4 . Because the coefficient of variation for almost all the joints tested is less than 10%, the failure load, shear strength, displacement at failure load, and joint equivalent stiffness, the results from the three samples for each joint tested could be considered statistically acceptable. Table 4 An overview of the KFRP-SDRP shear joint test results Joints No. Specimen Failure load (kN) Displacement at Failure load (mm) Shear strength (MPa) Joint equivalent stiffness (kN/mm) 10-25-1 5.416 1.670 10.832 3.243 A1 10-25-2 5.652 1.8902 11.304 2.990 10-25-3 6.440 1.8500 12.880 3.481 Mean 5.836 1.8034 11.672 3.238 Std. Dev. 0.536224 0.117263 1.072448 0.245538 Coeff. Of Var. (%) 9.188 6.502 9.188 7.583 A2 Specimen Failure load (kN) Displacement at Failure load (mm) Shear strength (MPa) Joint equivalent stiffness (kN/mm) 15-25-1 8.1490 1.9102 11.600 4.266 15-25-2 7.1964 1.8272 9.595 3.938 15-25-3 7.600 1.9200 10.133 3.958 Mean 7.648467 1.8858 10.44267 4.054 Std. Dev. 0.478146 0.050985 1.037751 0.18387 Coeff. Of Var. (%) 6.251 2.704 9.938 4.536 A3 Specimen Failure load (kN) Displacement at Failure load (mm) Shear strength (MPa) Joint equivalent stiffness (kN/mm) 20-25-1 8.700 2.1511 8.700 4.044 20-25-2 8.338 2.049 8.338 4.069 20-25-3 8.181 2.062 8.181 3.968 Mean 8.406333 2.087367 8.406333 4.027 Std. Dev. 0.266162 0.055576 0.266162 0.052602 Coeff. Of Var. (%) 3.166 2.662 3.166 1.306 A4 Specimen Failure load (kN) Displacement at Failure load (mm) Shear strength (MPa) Joint equivalent stiffness (kN/mm) 25-25-1 10.701 2.1803 8.561 4.908 25-25-2 9.527 2.2064 7.622 4.318 25-25-3 9.7178 2.0820 7.774 4.668 Mean 9.981933 2.156233 7.985667 4.631333 Std. Dev. 0.629995 0.065599 0.504016 0.296704 Coeff. Of Var. (%) 6.311 3.042 6.311 6.406 B1 Specimen Failure load (kN) Displacement at Failure load (mm) Shear strength (MPa) Joint equivalent stiffness (kN/mm) 10-35-1 7.220 1.6713 10.314 4.320 10-35-2 7.110 1.6702 10.157 4.257 10-35-3 6.092 1.6008 8.703 3.805 Mean 6.807333 1.647433 9.724667 4.127333 Std. Dev. 0.621934 0.040389 0.888265 0.280921 Coeff. Of Var. (%) 9.136 2.452 9.134 6.806 B2 Specimen Failure load (kN) Displacement at Failure load (mm) Shear strength (MPa) Joint equivalent stiffness (kN/mm) 15-35-1 9.260 1.7400 8.819 5.322 15-35-2 9.080 1.7700 8.648 5.130 15-55-3 8.160 1.8200 7.771 4.484 Mean 8.833333 1.776667 8.412667 4.978667 Std. Dev. 0.590028 0.040415 0.562239 0.439019 Coeff. Of Var. (%) 6.679 2.274 6.683 8.818 B3 Specimen Failure load (kN) Displacement at Failure load (mm) Shear strength (MPa) Joint equivalent stiffness (kN/mm) 20-35-1 10.3012 1.8001 7.358 5.723 20-35-2 12.6012 1.9000 9.001 6.632 20-35-3 12.1000 2.0599 8.643 5.875 Mean 11.66747 1.92 8.334 6.076667 Std. Dev. 1.209468 0.13105 0.863987 0.486901 Coeff. Of Var. (%) 10.366 6.826 10.367 8.013 B4 Specimen Failure load (kN) Displacement at Failure load (mm) Shear strength (MPa) Joint equivalent stiffness (kN/mm) 25-35-1 14.7702 1.8605 8.440 7.939 25-35-2 14.6021 1.9002 8.344 7.685 25-35-3 12.8013 1.9401 7.315 6.598 Mean 14.05787 1.900267 8.033 7.407333 Std. Dev. 1.09146 0.0398 0.623656 0.712316 Coeff. Of Var. (%) 7.764 2.094 7.764 9.616 C1 Specimen Failure load (kN) Displacement at Failure load (mm) Shear strength (MPa) Joint equivalent stiffness (kN/mm) 10-50-1 9.240 1.8312 9.240 5.046 10-50-2 8.671 1.8311 8.671 4.585 10-50-3 8.382 1.6553 8.382 5.064 Mean 8.764333 1.772533 8.764333 4.898333 Std. Dev. 0.436548 0.101527 0.436548 0.271504 Coeff. Of Var. (%) 4.981 5.728 4.981 5.543 C2 Specimen Failure load (kN) Displacement at Failure load (mm) Shear strength (MPa) Joint equivalent stiffness (kN/mm) 15-50-1 13.680 1.8003 9.120 7.599 15-50-2 12.240 1.8702 8.160 6.545 15-50-3 11.330 1.7902 7.553 6.329 Mean 12.41667 1.820233 8.277667 6.824333 Std. Dev. 1.184919 0.043566 0.790099 0.679518 Coeff. Of Var. (%) 9.542 2.393 9.545 9.957 C3 Specimen Failure load (kN) Displacement at Failure load (mm) Shear strength (MPa) Joint equivalent stiffness (kN/mm) 20-50-1 17.201 1.9400 8.600 8.86649485 20-50-2 15.650 2.0402 7.826 7.67081659 20-50-3 15.049 1.9140 7.525 7.862591 Mean 15.96667 1.964733 7.983667 8.133301 Std. Dev. 1.110398 0.066636 0.554572 0.642164 Coeff. Of Var. (%) 6.954 3.378 6.946 7.8958 C4 Specimen Failure load (kN) Displacement at Failure load (mm) Shear strength (MPa) Joint equivalent stiffness (kN/mm) 25-50-1 19.601 2.0701 7.840 8.30926 25-50-2 17.601 2.0301 7.048 7.70898 25-50-3 20.702 2.400 8.281 8.6254 Mean 19.30133 2.166733 7.723 8.214547 Std. Dev. 1.572069 0.203002 0.624771 0.465494 Coeff. Of Var. (%) 8.145 9.369 8.089 5.667 Figure 16 depicts the ultimate failure load as a function of overlap length and bond width to illustrate further the impact of overlaps on the failure load and lap shear strength. The area under the load-displacement responses was used to compute the corresponding energy absorption for all joints, and the results are reported in Fig. 17 . Regarding energy absorption, a pattern resembling the failure load in Fig. 16 is discernible across the different configurations. The Figs. 16 and 17 demonstrate how the load-bearing capacity and energy absorption capacity of polyester adhesively bonded double lap shear joints increased with an increase in overlap length and bond width. Similar results pattern was obtained by [ 38 , 39 , 40 ]. 4.2 Failure mechaisms of double lap shear joints The failure mechanisms of all the double lap joints occurred suddenly with no obvious sign or prior warnings. It was also observed that most of the specimens of the double lap joints failed in a brittle and sudden manner. Three failure modes were noticed for all the specimens tested under compression loading. There are (i) adhesive failure, this mode of failure occurs wherever the joint fails at the border amid the adhesive and the sandwich adherents; (ii) cohesive failure, this mode of failure happens inside the adhesive where the adhesive fractured; and (iii) adherend failure, this mode of failure occurred where the sandwich adherend fractured or failed. The failure mode for the double lap shear joints was dominated by cohesive failure with a few accompanying fiber pull-outs. An adhesive failure was noticed for specimens A1, and B2 in Fig. 18 ( a) and Fig. 19 (b), while cohesive failure was observed in A2, A3, A4, B1, B3, B4, C1, C2, and C3 in Fig. 18 (b), (c) and (d), and Fig. 19 (a), (c) and (d), and Fig. 20 (a), (b), and (c) respectively. The failure of sandwich adherend was observed as the other mode of failure for the specimen in C4 (Fig. 20 (d). The failure behavior was influenced by the chemical bond created at the interface between a polymer adhesive and the sandwich adherents when the adhesive was cured. Adhesive failure occurred in A1 and B2 which suggested the formation of a weak chemical bond at the interface, a type of failure that is undesirable when a strong bond is anticipated. On the other hand, cohesive failure was noticed in A2, A3, A4, B1, B3, B4, C1, C2, and C3 which indicated a good chemical bond at the interface of the sandwich adherents and the polymer adhesive. A good adhesive bond is considered cohesive by most quality control criteria [ 41 ]. A more desirable mode of failure is the one observed in C4, which is called adherend failure. Here the sandwich joint not only ensures that the joint's maximum capacity is utilized, but also that the adherents and the polymer glue have a very strong relationship. 4.3 Validation of FE models The experimental load-displacement curves were compared with the simulated load-displacement plots for each joint as a function of overlap length and bond width. The simulated joints have the following dimensions: A1(10 mm x 25 mm), A2(15 mm x 25 mm), A3(20 mm x 25 mm), A4(25 mm x 25 mm), B1(10 mm x 35 mm), B2(15 mm x 35 mm), B3(20 mm x 35 mm), B4(25 mm x 35 mm), C1(10 mm x 50 mm), C2(15 mm x 50 mm), C3(20 mm x 50 mm) and C4(25 mm x 50 mm) are shown in Fig. 21 (a), (b), (c), (d), Fig. 22 (a), (b), (c), (d), and Fig. 23 (a), (b), (c), (d) respectively. The load on the curves increased nonlinearly with increasing displacement until failure occurred for Joints A1, A2, A4, B1, B2, B3, B4, C2, C3, and C4, while joints A3 and C1 had almost linear curves until failure. It was also observed that most of the curves started linearly in progression which was lost mid-way and retained before failure. This may be due elastic-plastic behavior of the brittle adhesive material used. After the ultimate load was reached, the load-carrying capacity of all the joints dropped to zero, and the curve presented as a falling strength line. It was observed that the simulated failure load was slightly higher than the experimentally measured load for all the joint configurations. This phenomenon may not be far from manufacturing variability and instrumentational error. Despite these, it could be seen in terms of stiffness, ultimate load-bearing capacity, failure mechanism, and post-failure regime, the numerical curves correspond well with the experimental ones. Table 5 shows the comparison of the numerical analysis with the experimental results. It can be observed that the numerical analysis and the experimental data were in good agreement. This phenomenon demonstrates the usefulness of the cohesive element in the numerical analysis of joints. One of the mechanical metrics used to evaluate the plastic deformation and fracture mechanisms of composite materials is the Mises equivalent stress. For lap shear joint models of joints A1 (10 mm x 25 mm), A2 (15 mm x 25 mm), A3 (20 mm x 25 mm), and A4 (25 mm x 25 mm), Fig. 24 displays the von Mises stress distribution contour plots. That of joints B1(10 mm x 35 mm), B2(15 mm x 35 mm), B3(20 mm x 35 mm) and B4(25 mm x 35 mm) are presented in Fig. 25 and joints C1(10 mm x 50 mm), C2(15 mm x 50 mm), C3(20 mm x 50 mm) and C4(25 mm x 50 mm) are shown in Fig. 26 respectively. For all of the joints, the highest stress occurred at the overlap edges, generating a concentration that initiates the damage, leading to cohesive crack development and fracture in the adhesive bond, according to the plots. The zone of maximum von Mises equivalent stress in the layer increases with increasing bonded area and load, indicating progressive bond failure as found experimentally. In addition, the majority of the joints showed the beginnings of failure in the bonded area, with slightly varied colors indicating some plastic deformation. The stress concentration near the borders of the bonded area, where the peel stress and shear stress are highest, explains this. Table 5 Numerical analysis and experimental average failure loads and displacement of joints Joints No Experimental failure load, F EXP (failure mode) Numerical failure load, F NUM Failure load, F NUM / F EXP Experimental average displacement at failure load, F EXP Numerical displacement at failure load, F NUM (N) (N) (N) (mm) (mm) A1 5.84 (Adhesive) 6.71 1.15 1.80 1.83 A2 7.68 (Cohesive) 8.53 1.12 1.86 1.88 A3 8.41 (Cohesive) 9.11 1.08 2.09 2.08 A4 10.00 (Cohesive) 11.25 1.13 2.16 2.1 B1 6.81 (Cohesive) 7.43 1.09 1.78 1.84 B2 8.83 (Cohesive) 10.08 1.14 1.92 2.09 B3 11.67 (Cohesive) 12.78 1.10 1.90 2.1 B4 14.10 (Cohesive) 15.28 1.10 1.77 2.19 C1 8.76 (Cohesive) 9.64 1.10 1.72 1.85 C2 12.42 (Cohesive) 13.96 1.12 1.82 2.12 C3 15.96 (Cohesive) 17.17 1.08 1.95 2.18 C4 19.30 (Adherend) 20.84 1.08 2.17 2.25 4.4 Adhesive layer stress distribution at various overlap lengths Figure 26 shows the stress distributions in double lap adhesive joint with KFRP adherend and SDRP adherend while using polyester 2597APT waxed as joint material under compression load. With a constant bond width of 25 mm, the shear stress (S13) and peel stress (S33) that concentrate over the overlap lengths of 10 mm, 15 mm, 20 mm, and 25 mm are simulated from ABAQUS FEM and explained. Widths of 35 mm and 50 mm were not considered in this section due to similar results. Figure 27 (a) shows the parabolic shear stress distribution curves for all the overlap lengths, seemingly, high stress levels appear to be concentrated near the two extremities of the overlaps, with lesser stress concentration in the center. The peak stress at the edge ends explains why failure always starts at the bonded region's end. As the overlap length rises, the overall shear stress level, including the peak shear stress at the end parts, decreases. This explains why the failure load increases in proportion to the overlap. On the other hand, shear stress decreases are not proportional to overlap length. The rate of reduction of the shear stress peak at the ends is not constant, but it decreases steadily as the overlap length grows. This explains why, as overlap length grows, joint strength decreases. A similar occurrence was reported in [ 42 ]. Figure 27 (b) shows the peel stress distribution curves over the entire overlap lengths. When overlap length increases, the maximum peel stress in the glue decreases and the distribution of stress tends to be uniform over the entire overlap length, except in the region at the edge end. This decrease in the peel stress which formed at the end of the overlap length enhanced the joint's load-bearing capacity. The absolute values of the maximum and minimum peel stress at the end of the edges were the same with both positive and negative values. A similar phenomenon was reported in [ 43 ]. The findings show that the stress distribution patterns in KFRP and SDRP double lap joints may be precisely described by the developed FEM. 5 conclusions Double lap adhesively bonded joints made of KFRP and SDRP under compressive loads were investigated through experimental and numerical analysis. The results are summarized as follows: The load-displacement curves as a function of overlap lengths for most of the joints show almost linear behaviour from the beginning but linearity was lost mid-way and regained before failure. The failure load is exactly proportionate to the overlap length. However, the shear bond strength is inversely proportionate to the overlap length. Also, the impact of bond width on the load-displacement curves increased slightly nonlinear with displacement for most of the curves with noticeable changes in stiffness. Three failure modes that were identified from the adhesive joint tests are: adhesive failure, cohesive failure, and adherend failure. However, cohesive failure dominates all the failure modes. The ultimate failure load is proportional to the bond width here as well, although the bond shear strength is not. It was observed that by increasing overlap length and the bond width increased the load-carrying capacity and displacement capacity of the adhesively bonded joints. In the case of the total energy absorbed amongst the various joint types, a tendency comparable to that of the ultimate failure load was seen, as well as an increase in joint stiffness. The load-displacement response and stress distribution in adhesively bonded joints can be predicted using cohesive elements. When the failure loads derived from the experiments and numerical studies are compared, it can be observed that the experimental and numerical results are consistent. As the overlap length increased, the shear stress and the peel stress at the peak decreased on both edges and stress distribution was relatively much uniform. A considerable stress gradient is present near the overlap's ends, and the stress non-uniformity is made worse by a longer overlap length. The high-stress zone shifts from the end to the center of the bondline as the load increases, and the peel and shear stresses at the overlap edges are noticeably higher than those in the central region before the damage started in the adhesive. The shear in the central region is larger than the shear around the overlap edges because adhesive breakdown appears first close to the overlap edges. The findings from the experimental and numerical studies were consistent with each other. To better characterize the behavior of the materials under various situations and time scales, more research is needed, such as exposing the KFRP-SDRP adhesively joint to high temperatures and environmental conditions for long-term durability. This could aid in further research into the sustainability and long-term performance of bio-composite joints. Lastly, Video microscopy may be better integrated into the analysis of bond line behavior in KFRP and SDRP sandwich double lap joints so that data can be reliably recorded and utilized as another method of assessing crack initiation strain in the adhesive layer. List of abbreviations KFRP Kenaf fiber reinforced polymer SDRP Sawdust reinforced polymer DLJ Double lap joint DLS Double lap shear WPC Wood polymer composite FE Finite element FEM Finite element method GFRP Glass Fiber Reinforced Polymer NKTB National kenaf and tobacco board MEKP Methyl Ethyl Ketone Peroxide ASTM America society for testing materials UD Unidirectional UTM Universal testing machine MPa Megapascal KN Kilonewton Mm Millimeters QUADSCRT Quadratic traction damage initiation criterion τ Shear P Load A Area ρ f Density of kenal fiber composite E1= E2= E3 Young moduli G12 = G13= G23 Shear moduli Nuf12= Nuf13= Nuf23 Poisson ratios p Density of Polyester Polymer E m Young modulus of polyester polymer Gm Shear modulus of polyester polymer Vm Poisson ratio of polyester polymer Declarations Availability of data The dataset used and analyzed during the current study are available from the corresponding author upon reasonable request. competing interests The authors declared that none potentials conflicts of interests or personal relationships could have affected the research we did for this study. Ethics, consent to participate Not applicable Consent to publish Not applicable Funding The authors declare that they have not received any funding for this research work . Authors’ contribution AMA: Conceptualization, methodology and original draft writing and review. IA: Methodology, writing and review. UA: Writing and review. NAK: Supervision and editing. All authors read and approved the final manuscript Acknowledgement The authors gracefully acknowledged the project supported by Ministry of Higher Education Malaysia. References Ramakrishnan KR, Sarlin E, Kanerva M, Hokka M. “Experimental study of adhesively bonded natural fibre composite – steel hybrid laminates,” Compos. Part C Open Access , vol. 5, p. 100157, Jul. 2021, doi: 10.1016/J.JCOMC.2021.100157. Ozankaya G. et al. , “Prediction of lap shear strength of GNP and TiO2/epoxy nanocomposite adhesives,” Nanotechnol. Rev. , vol. 12, no. 1, 2023, doi: 10.1515/ntrev-2023-0134. Li H, Xu S, Zhang Z, Song C. “Experimental and numerical investigation on the corrosion effects on the bonding behavior between CFRP and steel,” Compos. Struct. , vol. 259, p. 113465, Mar. 2021, doi: 10.1016/J.COMPSTRUCT.2020.113465. Ceren Yildirim MY, Hasan Ulus, Bertan Beylergil, Abdulrahman Al-Nadhari, Serra Topal, “Tailoring adherend surfaces for enhanced bonding in CF/PEKK composites: Comparative analysis of atmospheric plasma activation and conventional treatments,” Compos. Part A Appl. Sci. Manuf. , vol. 180, no. 108101, 2024, doi: https://doi.org/10.1016/j.compositesa.2024.108101. Halil Burak Kaybal HU. “Comparative analysis of thermoplastic and thermoset adhesives performance and the influence on failure analysis in jointed elium-based composite structures,” pp. 3474–3492, 2023. Marchione P, Munafo F. “Effect of thermal aging on the mechanical performance of timber-timber single-lap adhesive joints,” Int. J. Adhes. Adhes. , vol. 108, no. 102883., 2021, doi: https://doi.org/10.1016/j.ijadhadh.2021.102883. Campilho RDSG, Moura DC, Gonçalves DJSJ, Da Silva FMG, Banea MD,. Da Silva LFM. “Fracture toughness determination of adhesive and co-cured joints in natural fibre composites,” Compos. Part B Eng. , vol. 50, pp. 120–126, Jul. 2013, doi: 10.1016/J.COMPOSITESB.2013.01.025. Delzendehrooy Ayatollahi FMR, Akhavan-Safar A, da Silva LFM. “Strength improvement of adhesively bonded single lap joints with date palm fibers: Effect of type, size, treatment method and density of fibers,” Compos. Part B Eng. , vol. 188, p. 107874, May 2020, doi: 10.1016/J.COMPOSITESB.2020.107874. Russian O, Belarbi KSA, Dawood M. “Effect of surface preparation technique on bond behavior of CFRP-steeldouble-lap joints: Experimental and numerical studies,” Compos. Struct. , vol. 255, no. 113048, pp. 1–13, 2021. Song MG, et al. , “Effect of manufacturing methods on the shear strength of composite single-lap bonded joints,” Compos. Struct. , vol. 92, no. 9, pp. 2194–2202, Aug. 2010, doi: 10.1016/J.COMPSTRUCT.2009.08.041. Yang G, Yang T, Yuan W, Du Y. “The influence of surface treatment on the tensile properties of carbon fiber-reinforced epoxy composites-bonded joints,” Compos. Part B Eng. , vol. 160, pp. 446–456, Mar. 2019, doi: 10.1016/J.COMPOSITESB.2018.12.095. Anaç N. “The Effect of Organic Fillers on the Mechanical Strength of the,” 2023. Adole MA, Yatim JM, Abubakar SR, Azzmi NM. “Potentials of Wood Fibre Reinforced Polymeric Composites,” J. Polym. Sci. Technol. , vol. 3, no. 1, pp. 19–31, 2018. Adole MA, Yatim JM, Abubakar SR, Othman A, Mizal NA. “Kenaf Fibre and Its Bio-Based Composites: A Conspectus,” Pertanika J. Sci. Technol. , vol. 27, no. 1, pp. 297–329, 2019. Khakpour H, Ayatollahi MR, Akhavan-Safar A, da Silva LFM. “Mechanical properties of structural adhesives enhanced with natural date palm tree fibers: Effects of length, density and fiber type,” Compos. Struct. , vol. 237, p. 111950, Apr. 2020, doi: 10.1016/J.COMPSTRUCT.2020.111950. Aiza Jaafar CN, Zainol IN, Ishak S, Ilyas RA, Sapuan SM. “Effects of the Liquid Natural Rubber (LNR) on Mechanical Properties and Microstructure of Epoxy/Silica/Kenaf Hybrid Composite for Potential Automotive Applications,” J. Mater. Res. Technol. , vol. 12, pp. 1026–1038, May 2021, doi: 10.1016/j.jmrt.2021.03.020. Bharath Raman N, , Ramnath Vijaya VR, Manoharan B. “Kenaf Fibre Reinforced Composites: A Review.,” ARPN J. Eng. Appl. Sci. , vol. 10, no. 13, pp. 5483–5485, 2015. Khan A. et al. , “Extraction and characterization of vetiver grass (Chrysopogon zizanioides) and kenaf fiber (Hibiscus cannabinus) as reinforcement materials for epoxy based composite structures,” J. Mater. Res. Technol. , vol. 9, no. 1, pp. 773–778, Jan. 2020, doi: 10.1016/J.JMRT.2019.11.017. Mahjoub R, Yatim JM, Mohd Sam AR, Hashemi SH. “Tensile properties of kenaf fiber due to various conditions of chemical fiber surface modifications,” Constr. Build. Mater. , vol. 55, pp. 103–113, Mar. 2014, doi: 10.1016/J.CONBUILDMAT.2014.01.036. Abidin NMZ. et al. , “The evaluation of the mechanical properties of glass, kenaf, and honeycomb fiber-reinforced composite,” Rev. Adv. Mater. Sci. , vol. 62, no. 1, 2023, doi: 10.1515/rams-2022-0299. Uzoma AE, Nwaeche CF, Al-Amin M, Muniru OS, Olatunji O, Nzeh SO. “Development of Interior and Exterior Automotive Plastics Parts Using Kenaf Fiber Reinforced Polymer Composite,” Eng , vol. 4, no. 2, pp. 1698–1710, 2023, doi: 10.3390/eng4020096. Mitchelle AJ. “Composites of commercial wood pulp fibres and cement,” Appita , vol. 33, no. 6, pp. 461–463, 1986. Nashino T, Hireo K, Kotera M, Nakamae K, Inagaki K. “Kenaf reinforced biodegradable composite.,” Compos. Sci. Technol. , vol. 63, no. 9, pp. 1281–1286, 2003. Karaduman Y, Onal L. “Flexural behavior of commingled jute/polypropylene nonwoven fabric reinforced sandwich composites,” Compos. Part B Eng. , vol. 93, pp. 12–25, May 2016, doi: 10.1016/J.COMPOSITESB.2016.02.055. Madyan OA, Wang Y, Corker J, Zhou Y, Du G, Fan M. “Classification of wood fibre geometry and its behaviour in wood poly(lactic acid) composites,” Compos. Part A Appl. Sci. Manuf. , vol. 133, p. 105871, Jun. 2020, doi: 10.1016/j.compositesa.2020.105871. Ichazo M, Albano C, González J, Perera R, Candal M. “Polypropylene/wood flour composites: treatments and properties,” Compos. Struct. , vol. 54, no. 2–3, pp. 207–214, Nov. 2001, doi: 10.1016/S0263-8223(01)00089-7. Ramalho LDC, Campilho RDSG, Belinha J, da Silva LFM. “Static strength prediction of adhesive joints: A review,” Int. J. Adhes. Adhes. , vol. 96, no. 102451, pp. 1–18, 2020. Lee BH, Kim HJ, Yui WR. “Fabrication of long and discontinuous natural fiber reinforced polypropylene bio-composites and their properties,” Fibers Polym. , vol. 10, no. 1, pp. 83–90, 2009. Gültekin K, Akpinar S, Özel A. “The effect of the adherend width on the strength of adhesively bonded single-lap joint: Experimental and numerical analysis,” Compos. Part B Eng. , vol. 60, pp. 736–745, Apr. 2014, doi: 10.1016/J.COMPOSITESB.2014.01.022. ASTM, “Standard test method for tensile properties of polymer matrix composite materials,” in ASTM D3039/D 3039M. , 2014. ASTM, “Standard test method for tensile properties of plastics,” in ASTM International. Designation: D. 638, 1-13 , 2014. American Society for Testing and Materials, “ASTM D 905, Standard Test Method for Strength Properties of Adhesive Bonds in Shear by Compression Loading,” Assembly , vol. 04, no. Reapproved, pp. 7–10, 1999. Ferdous W, Manalo A, Aravinthan T. “Bond behaviour of composite sandwich panel and epoxy polymer matrix: Taguchi design of experiments and theoretical predictions,” Constr. Build. Mater. , vol. 145, pp. 76–87, Aug. 2017, doi: 10.1016/J.CONBUILDMAT.2017.03.244. Barbosa NGC, Campilho RDSG, Silva FJG, Moreira RDF. “Comparison of different adhesively‑bonded joint types for mechanical structures,” Appl. Adhes. Sci. , vol. 6, no. 15, pp. 1–19, 2018. ADOLE AM. “Effect of Fiber Orientation on the Tensile Properties of Kenaf Fiber Reinforced Polyester Composite,” J. Environ. Sci. , vol. 23, no. 2, pp. 12–23, 2024. Adole AM. “Influence of Fiber Loading on the Tensile and Physical Properties of Sawdust Reinforced Unsaturated Polyester Composite,” J. Environ. Des. , vol. 20, no. 2, pp. 17–23, 2024. Sun CL, Li CY, Tie Y, Hou, Duan Y. “Experimental and numerical investigations of adhesively bonded CFRP single-lap joints subjected to tensile loads,” Int. J. Adhes. Ahesives , vol. 95, no. 102402, pp. 1–14, 2019. Kanani A. Y. Hou, X. Laidlaw R, Ye J. “The effect of joint configuration on the strength and stress distributions of dissimilar adhesively bonded joints,” Eng. Struct. , vol. 226, no. 111322, pp. 1–11, 2021. Hartsfield M. et al. , “Dissimilar material joining of densified superwood to aluminum by adhesive bonding,” Int. J. Adv. Manuf. Technol. , vol. 131, no. 1, pp. 425–436, 2024, doi: 10.1007/s00170-024-13155-0. Russian O, Khan S, Belarbi A, Dawood M. “Effect of surface preparation technique on bond behavior of CFRP-steel double-lap joints: Experimental and numerical studies,” Compos. Struct. , vol. 255, p. 113048, Jan. 2021, doi: 10.1016/J.COMPSTRUCT.2020.113048. Katsiropoulos CV, Chamos AN, Tserpes KL, Pantelakis SG. “Fracture Aerospace, toughness and shear behaviour of composite bonded joints based on a novel Adhesive,” Compos. Part B Eng. , vol. 43, no. 3, pp. 24–248, 2012. Velayutham S, Sugiman S, Ahmad H, Jaini ZM. “Shear Strength of Adhesively Bonded Joint with Toughened Epoxy Mussel Powder,” Int. J. Integr. Eng. , vol. 16, no. 1, pp. 201–212, 2024, doi: 10.30880/ijie.2024.16.01.016. ARABAĞ DK, TEKKANAT MA. ANAÇ N. KOÇAR O. “Investigation of adhesive bonding strength of wood added PLA materials,” Mobilya ve Ahşap Malzeme Araştırmaları Derg. , vol. 6, no. 1, pp. 26–38, 2023, doi: 10.33725/mamad.1304449. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Under Revision Version 1 posted Submission checks completed at journal 29 Apr, 2025 First submitted to journal 16 Apr, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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Adole","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA+UlEQVRIie3Pv4rCMBzA8V/4QV30ukYEfYWUgtxBD1+lR9b6CkehUBf/rHa6t8jckuGWA1chi9PN7WQVDy45Jwdb3Q7Mdwgk5EPyA7DZ/mUhyQEoA8RiV+q902kncCYdh3trQ/A2Agzc7njQNQdtxJ3xPK+iZ99FYIPgKEZPCKSsouuEfn2HRSbouJ9A6E+XyksRsJ+Jhme2EZM9QQMmIefTuSKaONhrICNDfjSZSBLLl7matBJmCNEfY4gkgVq9tRLPzLIQ1KfSQbKIFU81bZxl+MmL3UG8e6vVZl/XJ/X6MUuKsmoa/yKS/q3xrfdNp3su22w226P0CwhqUrwty1oeAAAAAElFTkSuQmCC","orcid":"","institution":"Modibbo Adama University","correspondingAuthor":true,"prefix":"","firstName":"Adole","middleName":"Michael","lastName":"Adole","suffix":""},{"id":449700345,"identity":"e79222ea-1641-4b34-9507-b2ef3e2fa69f","order_by":1,"name":"Iorwuese Anum","email":"","orcid":"","institution":"Modibbo Adama University","correspondingAuthor":false,"prefix":"","firstName":"Iorwuese","middleName":"","lastName":"Anum","suffix":""},{"id":449700346,"identity":"2314cc7d-b142-4752-b79f-f3adda2af642","order_by":2,"name":"Umar Abdullahi","email":"","orcid":"","institution":"Modibbo Adama University","correspondingAuthor":false,"prefix":"","firstName":"Umar","middleName":"","lastName":"Abdullahi","suffix":""},{"id":449700347,"identity":"07133603-c59d-453d-affb-22903b10a09a","order_by":3,"name":"Namala Amuga Keftin","email":"","orcid":"","institution":"Modibbo Adama University","correspondingAuthor":false,"prefix":"","firstName":"Namala","middleName":"Amuga","lastName":"Keftin","suffix":""}],"badges":[],"createdAt":"2025-01-15 19:08:11","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-5836800/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-5836800/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":81806070,"identity":"66dad0e0-d047-4b95-bd94-3af2876dfd04","added_by":"auto","created_at":"2025-05-02 07:22:13","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":365532,"visible":true,"origin":"","legend":"\u003cp\u003eUD kenaf fiber aligned in mold for fabrication (a) and KFRP composite laminates (b)\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-5836800/v1/2a55c083447d9ddff306cb3d.png"},{"id":81806071,"identity":"ed47ad2f-77e7-4b09-b0c8-4008f6019089","added_by":"auto","created_at":"2025-05-02 07:22:13","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":175732,"visible":true,"origin":"","legend":"\u003cp\u003eMild steel mold (a) and particulate SDRP composite (b)\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-5836800/v1/457f85aae87d096dd3a3cb6f.png"},{"id":81805829,"identity":"15619fd7-0890-49cc-8b6c-ea058d746d76","added_by":"auto","created_at":"2025-05-02 07:14:13","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":499399,"visible":true,"origin":"","legend":"\u003cp\u003eSamples clamped to work bench\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-5836800/v1/0ff43b48165c8d9d887b35d0.png"},{"id":81805830,"identity":"eee1a215-609d-4364-b9fd-525d764487fd","added_by":"auto","created_at":"2025-05-02 07:14:13","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":411204,"visible":true,"origin":"","legend":"\u003cp\u003ePost-curing of samples\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-5836800/v1/9dde585897dc878766f974cb.png"},{"id":81805114,"identity":"e6c9e4bd-e1b5-4f62-ac03-e49a99e16abf","added_by":"auto","created_at":"2025-05-02 07:06:13","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":198105,"visible":true,"origin":"","legend":"\u003cp\u003eTensile test set-up of KFRP adherend (a) and Tensile stress-strain curve of KFRP adherend (b).\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-5836800/v1/724ab8dc13a497d9d52b694c.png"},{"id":81805116,"identity":"da18c5ff-b021-4d24-8195-86abd05d42c1","added_by":"auto","created_at":"2025-05-02 07:06:13","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":257226,"visible":true,"origin":"","legend":"\u003cp\u003eTensile test set-up of SDRP adherend (a) and Tensile stress-strain curve of SDRP adherend (b).\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-5836800/v1/dafb3429c0febf28e1c82438.png"},{"id":81806749,"identity":"ca690549-58cf-42c2-8c7c-60c6802cb19f","added_by":"auto","created_at":"2025-05-02 07:30:13","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":284961,"visible":true,"origin":"","legend":"\u003cp\u003eDouble lap shear joint dimensions and geometrical arrangement, 2D view (a) and 3D view (b), Double lap shear joint setup\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-5836800/v1/dfa4f89765fc5060195c4be1.png"},{"id":81805110,"identity":"974298a6-79ce-4bbe-9ef6-fa1d565c9043","added_by":"auto","created_at":"2025-05-02 07:06:13","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":52582,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Double lap shear joint finite element model, (b) model displaying the joint's adhesive layer\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-5836800/v1/11e0ce9e967fe32aea010a79.png"},{"id":81805837,"identity":"4291a98e-8838-4d87-8161-dbe993511c5b","added_by":"auto","created_at":"2025-05-02 07:14:14","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":29391,"visible":true,"origin":"","legend":"\u003cp\u003eTraction-separation cohesive law with the exponential damage evolution [34]\u003c/p\u003e","description":"","filename":"9.png","url":"https://assets-eu.researchsquare.com/files/rs-5836800/v1/3a6303c3ac1b5a8f7c95f28c.png"},{"id":81805128,"identity":"ed0e66c8-53f4-4a74-94a3-254dbdb3ac91","added_by":"auto","created_at":"2025-05-02 07:06:13","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":162635,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Double lap joint finite element mesh, (b) mesh model displaying the joint's adhesive layer\u003c/p\u003e","description":"","filename":"10.png","url":"https://assets-eu.researchsquare.com/files/rs-5836800/v1/c541299009320c8ff6a92de1.png"},{"id":81805127,"identity":"2a0e4b61-37d6-4135-8821-18b766fe0e86","added_by":"auto","created_at":"2025-05-02 07:06:13","extension":"png","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":108472,"visible":true,"origin":"","legend":"\u003cp\u003eModels of double lap shear joints with boundary and loading conditions\u003c/p\u003e","description":"","filename":"11.png","url":"https://assets-eu.researchsquare.com/files/rs-5836800/v1/e0dc118da486a5589b3b792b.png"},{"id":81805123,"identity":"d1ea11bd-2ffe-44b0-a240-3706df185c83","added_by":"auto","created_at":"2025-05-02 07:06:13","extension":"png","order_by":12,"title":"Figure 12","display":"","copyAsset":false,"role":"figure","size":28964,"visible":true,"origin":"","legend":"\u003cp\u003ePlots of experimental load and displacement for specimens with different overlap lengths in relation to bond width of 25 mm\u003c/p\u003e","description":"","filename":"12.png","url":"https://assets-eu.researchsquare.com/files/rs-5836800/v1/755fdbe877087f509b115436.png"},{"id":81805833,"identity":"904d47d1-b3af-4286-a595-27bef1013ea1","added_by":"auto","created_at":"2025-05-02 07:14:13","extension":"png","order_by":13,"title":"Figure 13","display":"","copyAsset":false,"role":"figure","size":29602,"visible":true,"origin":"","legend":"\u003cp\u003ePlots of experimental load and displacement for specimens with different overlap lengths in relation to bond width of 35 mm\u003c/p\u003e","description":"","filename":"13.png","url":"https://assets-eu.researchsquare.com/files/rs-5836800/v1/29adb58679c772dac78a0609.png"},{"id":81805124,"identity":"22400a33-2f63-4be3-b5da-eb56f505f353","added_by":"auto","created_at":"2025-05-02 07:06:13","extension":"png","order_by":14,"title":"Figure 14","display":"","copyAsset":false,"role":"figure","size":26224,"visible":true,"origin":"","legend":"\u003cp\u003ePlots of experimental load and displacement for specimens with different overlap lengths in relation to bond width 50 mm\u003c/p\u003e","description":"","filename":"14.png","url":"https://assets-eu.researchsquare.com/files/rs-5836800/v1/0071233df1eb77531abde076.png"},{"id":81805120,"identity":"492bea5f-2a4f-4223-a72c-f1abc58e80bc","added_by":"auto","created_at":"2025-05-02 07:06:13","extension":"png","order_by":15,"title":"Figure 15","display":"","copyAsset":false,"role":"figure","size":30897,"visible":true,"origin":"","legend":"\u003cp\u003eShear strength of the experimental shear joints as a function of bond width and overlap length\u003c/p\u003e","description":"","filename":"15.png","url":"https://assets-eu.researchsquare.com/files/rs-5836800/v1/3e5823597d0e48baf930cb7a.png"},{"id":81805119,"identity":"2ad0c5f8-7346-41f1-902f-eac9788bb33b","added_by":"auto","created_at":"2025-05-02 07:06:13","extension":"png","order_by":16,"title":"Figure 16","display":"","copyAsset":false,"role":"figure","size":14564,"visible":true,"origin":"","legend":"\u003cp\u003eShear joints' ultimate load as a relation to bond width and overlap length\u003c/p\u003e","description":"","filename":"16.png","url":"https://assets-eu.researchsquare.com/files/rs-5836800/v1/631b430bc9526fab78a5e360.png"},{"id":81805122,"identity":"b0d9dd6b-767b-4b49-9e6a-28c0b7a1dde4","added_by":"auto","created_at":"2025-05-02 07:06:13","extension":"png","order_by":17,"title":"Figure 17","display":"","copyAsset":false,"role":"figure","size":25086,"visible":true,"origin":"","legend":"\u003cp\u003eShear joint energy absorption capacity as a relation to bond width and overlap length\u003c/p\u003e","description":"","filename":"17.png","url":"https://assets-eu.researchsquare.com/files/rs-5836800/v1/bdddc8f0d17e224cca463fda.png"},{"id":81805836,"identity":"000dbcf0-2af0-4ca7-8a8b-ed2bbc754cb2","added_by":"auto","created_at":"2025-05-02 07:14:13","extension":"png","order_by":18,"title":"Figure 18","display":"","copyAsset":false,"role":"figure","size":550722,"visible":true,"origin":"","legend":"\u003cp\u003eFailure mechanisms for joint A1, A2, A3 and A4\u003c/p\u003e","description":"","filename":"18.png","url":"https://assets-eu.researchsquare.com/files/rs-5836800/v1/4ef57c4890ad46795a5cf68e.png"},{"id":81805121,"identity":"82b273e7-9853-417c-8291-6ed9083e8c4f","added_by":"auto","created_at":"2025-05-02 07:06:13","extension":"png","order_by":19,"title":"Figure 19","display":"","copyAsset":false,"role":"figure","size":598664,"visible":true,"origin":"","legend":"\u003cp\u003eFailure mechanisms for joint B1, B2, B3 and B4\u003c/p\u003e","description":"","filename":"19.png","url":"https://assets-eu.researchsquare.com/files/rs-5836800/v1/6d5426ea3b4012e1abf78e5f.png"},{"id":81805131,"identity":"f7bde8a1-dc62-4b51-a883-f72dd004f738","added_by":"auto","created_at":"2025-05-02 07:06:14","extension":"png","order_by":20,"title":"Figure 20","display":"","copyAsset":false,"role":"figure","size":545661,"visible":true,"origin":"","legend":"\u003cp\u003eFailure mechanisms for joint C1, C2, C3 and C4\u003c/p\u003e","description":"","filename":"20.png","url":"https://assets-eu.researchsquare.com/files/rs-5836800/v1/4add76daa09db092d7af7f50.png"},{"id":81805838,"identity":"e8f54353-2bd8-40be-8234-9c80a5a4b023","added_by":"auto","created_at":"2025-05-02 07:14:14","extension":"png","order_by":21,"title":"Figure 21","display":"","copyAsset":false,"role":"figure","size":83504,"visible":true,"origin":"","legend":"\u003cp\u003eComparison of the shear joint types through experimentation and numerical analysis, (a) A1, (b) A2, (c) A3, and (d) A4.\u003c/p\u003e","description":"","filename":"21.png","url":"https://assets-eu.researchsquare.com/files/rs-5836800/v1/c9c06c018a502f2df9f8c163.png"},{"id":81805129,"identity":"2c912ed8-8ab5-4afe-b4f8-8ce2877738bb","added_by":"auto","created_at":"2025-05-02 07:06:14","extension":"png","order_by":22,"title":"Figure 22","display":"","copyAsset":false,"role":"figure","size":125472,"visible":true,"origin":"","legend":"\u003cp\u003eComparison of the shear joint types by experimentation and numerical analysis, (a) B1, (b) B2, (c) B3, and (d) B4.\u003c/p\u003e","description":"","filename":"22.png","url":"https://assets-eu.researchsquare.com/files/rs-5836800/v1/1ba86a9940280c6baca0daeb.png"},{"id":81805125,"identity":"cdcbfd76-312c-47ad-8968-60c5033d93c7","added_by":"auto","created_at":"2025-05-02 07:06:13","extension":"png","order_by":23,"title":"Figure 23","display":"","copyAsset":false,"role":"figure","size":124391,"visible":true,"origin":"","legend":"\u003cp\u003eComparison of the shear joint types by experimentation and numerical analysis, (a) C1, (b) C2, (c) C3, and (d) C4.\u003c/p\u003e","description":"","filename":"23.png","url":"https://assets-eu.researchsquare.com/files/rs-5836800/v1/ca07abcb01b84972298c11e2.png"},{"id":81805835,"identity":"5288c8eb-d74a-44a2-b0f1-8fdc7eaf2ec5","added_by":"auto","created_at":"2025-05-02 07:14:13","extension":"png","order_by":24,"title":"Figure 24","display":"","copyAsset":false,"role":"figure","size":322218,"visible":true,"origin":"","legend":"\u003cp\u003ePlots illustrating the equivalent stress contours for the shear joint types A1, B2, C3, and D, respectively\u003c/p\u003e","description":"","filename":"24.png","url":"https://assets-eu.researchsquare.com/files/rs-5836800/v1/0585a097247c8806671a6aab.png"},{"id":81805134,"identity":"1d051a62-1cdc-466b-ab54-f8ba00e3dd84","added_by":"auto","created_at":"2025-05-02 07:06:14","extension":"png","order_by":25,"title":"Figure 25","display":"","copyAsset":false,"role":"figure","size":308740,"visible":true,"origin":"","legend":"\u003cp\u003ePlots illustrating equivalent stress contours for the shear joint types A1, B2, C3, and D, respectively\u003c/p\u003e","description":"","filename":"25.png","url":"https://assets-eu.researchsquare.com/files/rs-5836800/v1/a2c3172ceb4f92304ef4e664.png"},{"id":81805132,"identity":"4441e8f8-6a89-4a6e-89d4-db2767c80880","added_by":"auto","created_at":"2025-05-02 07:06:14","extension":"png","order_by":26,"title":"Figure 26","display":"","copyAsset":false,"role":"figure","size":354166,"visible":true,"origin":"","legend":"\u003cp\u003ePlots illustrating the equivalent stress contours for the shear joint types A1, B2, C3, and D, respectively\u003c/p\u003e","description":"","filename":"26.png","url":"https://assets-eu.researchsquare.com/files/rs-5836800/v1/d7eeae47acbb7fbd6e3a3a49.png"},{"id":81805136,"identity":"f143eca5-8d0a-4e30-9481-19056a170479","added_by":"auto","created_at":"2025-05-02 07:06:14","extension":"png","order_by":27,"title":"Figure 27","display":"","copyAsset":false,"role":"figure","size":159520,"visible":true,"origin":"","legend":"\u003cp\u003eDistributions of adhesive stress for shear joints with varying overlap lengths along the bondline: Shear stress (a) and peel stress (b)\u003c/p\u003e","description":"","filename":"27.png","url":"https://assets-eu.researchsquare.com/files/rs-5836800/v1/e569628490a246d7fc7f7a1a.png"},{"id":81807035,"identity":"e53f2b59-434f-4581-8f0c-d6fd43259a88","added_by":"auto","created_at":"2025-05-02 07:38:17","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":8381381,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5836800/v1/955552b1-cd4c-47e1-baf0-f46d449291b2.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Experimental and numerical investigation of double lap adhesively bonded joints composed of KFRP and SDRP subjected to compressive loads","fulltext":[{"header":"1 Introduction","content":"\u003cp\u003eDue to the widespread use of fiber-reinforced polymer composite materials in various engineering fields, particularly civil structures, traditional mechanical joints are gradually being replaced by adhesively bonded joints due to their higher connection efficiency, more uniform stress fields, corrosion resistance, and lower weight increase [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Adhesively bonded joints not only provide a smoother surface for structural purposes but also improve fatigue life [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eTherefore, adhesively bonded joints are increasingly utilized due to their advantages over mechanical fastening joints. Load transfer between composite parts is more uniformly performed across a larger area, and fastening holes and fasteners, which represent a factor of stress concentration and weight increase in the structures, are not required [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. On the other hand, adhesively bonded joints have some disadvantages. They are difficult to disassemble for inspection, and the bonding strength is sensitive to environmental factors such as temperature and humidity. In addition, these joints require surface treatment of the adherends to strengthen the adhesive bonding. Accordingly, extensive and systematic studies on the failure and strength of composite bonded joints are needed for safe and reliable designs [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eSecondly, the progressive weight transfer between adherends and the rotation of adherents in the presence of asymmetric load cause stress concentrations to form at adhesive joints along the geometry. One of the geometries most impacted in this situation is the single-lap joint arrangement, which bends under load because of asymmetry and causes high peel stresses at the over-lap ends. The double-lap joint and other geometries are less affected by peel strains [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. The key components that affect the integrity of adhesive joints\u0026mdash;parent adherend thickness, adhesive thickness, bonding length, bonding width, surface preparation, and geometric modifications that reduce stress concentrations\u0026mdash;have been extensively studied [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eOn the other hand, because of their many appealing qualities, including their low cost and density, natural fiber composites have drawn interest and uses, including in the building sector [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. To ascertain if it is feasible to link cured sections of a structure, repair them, or attach components during the construction process (for instance, because of challenging geometries), it is crucial to look into adhesive couplings between these materials. For several reasons, including lower density, less machine wear during fabrication, fewer health risks, biodegradability, availability from natural sources, and most importantly, lower cost. Natural fibers like kenaf, wood, sisal, flax henequen, jute, coconut, and palm are currently being considered as a replacement for synthetic fibers like glass, aramid, and carbon in composites [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eAdditionally, because natural fibers bend during manufacture rather than break, they offer greater design versatility. However, they have a high moisture absorption rate and low wettability for particular resins [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. By preventing moisture absorption, mercerization can help with this issue by strengthening the fiber-matrix bonding relationship and increasing the amount of cellulose visible on the natural fiber surface [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. Kenaf as a natural fiber, is becoming more and more prevalent because of environmental concerns and its exceptional qualities in composites, and this is shown in numerous studies [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eKenaf was determined to be significantly more abundant and competitively priced in the appropriate form compared to other types of natural fiber materials [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. Kenaf was designated as commercial kenaf because of its potential as a raw material for a wide range of goods in the manufacturing and industrial sectors [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. Above all, kenaf, like most other bio-fibers, has excellent mechanical properties, can be recycled easily, and has a low price and low density [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e, \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eKenaf is a very effective plant that requires minimal energy, nutrients, or chemical fertilizer to grow rapidly. Additionally, Kenaf is renowned for using less planting space and emitting more biomass per acre than any other forest tree [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. Integration of particulate filler/flour in the form of particles of silica, alumina, solid and hollow glass particles, wood flours/chips, and carbon black in the polymer matrix leads to numerous beneficial properties. For example, impact strength, increased stiffness, reduced density, and cost reduction. Because of these characteristics, particulate composites are appropriate for use in areas where weight is desired, such as civil infrastructure. It is observed from the literature that most particulate materials are produced from non-renewable materials like synthetic materials.\u003c/p\u003e \u003cp\u003eThat is why [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e] pointed out that bio-based products like wood flour can be utilized in sandwich adhesively bonded joint panels as an alternative to conventional materials, the authors argue that because synthetic materials emit carbon dioxide during their formation, they are non-renewable and non-recyclable and should be discouraged. Wood flour, on the other hand, has been the most popular choice for Wood Polymer Composite (WPC) manufacture owing to its low cost, ease of processing, and aspect ratios [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. As waste from different wood processing activities, wood flours are typically sourced from forest product companies [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIn a related manner, [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e] stated that to broaden the advancement of bio-inspired composite materials, it is intriguing to study the blend of bio-composite adherend accompanied by a wood-based adherend to have a completely bio-sourced sandwich adhesively bonded panel. The final product will be appealing in terms of waste management; the panel can be composted after it is eventually no longer in use.\u003c/p\u003e \u003cp\u003eIt is also crucial to fully comprehend the strength and failure mechanisms of adhesively bonded joints between these materials to expand the utilization of natural fiber-reinforced composites through trustworthy design approaches. To effectively forecast the behavior of adhesive joints, numerical methods like the Finite Element Method (FEM) are necessary since the increasing complexity of joint design makes it difficult or impossible to solve adhesive joint problems using analytical approaches [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e].\u003c/p\u003e \u003cp\u003e[\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e] studied double lap adhesively bonded joints and GFRP single lap supported joints: joint strength, peel stresses, and failure mechanisms. The load-displacement response and joint strength of the double lap joints were compared to those supported single lap joints to illustrate their better strength characteristics. It has been demonstrated that the joint strength improves with overlap length, but decreases with adhesive layer thickness, and is essentially independent of adhesive type. The researchers found that the double lap joints had a higher load-carrying capacity than the supported single lap joints.\u003c/p\u003e \u003cp\u003eThe influence of adherend width and overlap length on the strength performance of adhesively bonded lap joints was examined by [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]. The results showed that the bond overlap enhanced the bonded joints' displacement capacity and load-carrying capability. However, the load-carrying and displacement capacity figures were further improved by increasing the width instead of the overlap length. The peel stresses generated at the borders of the overlap length were reduced by increasing width relative to overlap, which was also observed for joints with the same bond area.\u003c/p\u003e \u003cp\u003eOnly a few papers in the literature have looked at the mechanical behaviour of adhesively bonded composite-to-composite joints. To the best of our knowledge, there is no literature on the influence of joint geometry on the characterization of strength performance of dissimilar natural fiber composite, which is the motivation for this study. The compressive strength of KFRP-to-SDRP bonded double lap joints with varying overlaps and adherend widths was tested in this research, subsequently, the compressive load-displacement curves were displayed, then failure modes and shear stress were investigated. The experimental results were then compared to the results of a finite element analysis, after that, a stress distribution in the various joints was performed\u003c/p\u003e"},{"header":"2 Methods","content":"\u003cp\u003eKenaf fiber, sawdust, and polyester polymers were the main materials utilized in this research. The kenaf fiber was sourced from the National Kenaf and Tobacco Board (NKTB), Malaysia. The sawdust was obtained from Seow Kok Hwa Enterprises SDN. BHD, a sawmill located at Kota Tinggi in Johor, Malaysia, while the unsaturated polyester polymer with the brand name polyester 2597APT waxed was supplied by Wee Tee Tong Chemical PTE LTD from Singapore. The catalyst used was under the brand name Esterox MEKP also supplied by Wee Tee Tong Chemical PTE LTD from Singapore. Before usage, the kenaf fiber and sawdust were treated and processed, then stored in a cold, dry environment.\u003c/p\u003e \u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1Manufacturing process\u003c/h2\u003e \u003cdiv id=\"Sec4\" class=\"Section3\"\u003e \u003ch2\u003e2.1.1 Fabrication of kenaf fiber reinforced composite (KFRP) adherend\u003c/h2\u003e \u003cp\u003eBefore fabricating the KFRP panel, the treated kenaf fiber bundles were combed with an iron comb and cut to lengths of 295 mm. Then the quantity to be utilized was calculated and weighed according to the density and volume fraction of kenaf fiber and polyester resin. 40% of the kenaf fiber was used. A mild steel mold with a dimension of 295 mm x 210 mm x 6 mm was used. A transparent plastic veil was laid into the cavity and the mold was polished with a releasing agent. A mold-releasing agent was used inside the mold for ease of removal of the final product. Consequently, using a mechanical mixer, polyester 2597APT waxed was mixed with Methyl Ethyl Ketone Peroxide (MEKP) which was the catalyst used in a ratio of 100:1 as specified by the manufacturer. The cut and combed unidirectional fibers were laid, and aligned layer by layer in the mold. Then, the mixture of polyester 2597APT waxed and MEKP was gently poured on the fiber while ensuring evenly distribution with the aid of a roller for ease and good penetration of the resin. After that, a 22 kg mild steel lid cover was gently placed on the mold and clamped to the workbench on which the mold was resting. At room temperature, the specimen was allowed to cure for 24 hours. After the curing time, the specimen panel was de-molded and post-cured in an oven at 70o C for 6 hours. Then, the panel was removed from the oven after the curing period, cleaned, and stored. Finally, the panels were machined to conform to any specimen size or shape as specified by ASTM using a bench saw and a hand-grinding machine. Some of the processes are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. The specimens for the unidirectional longitudinal tensile test are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e (b).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section3\"\u003e \u003ch2\u003e2.1.2 Fabrication of sawdust reinforced composite (SDRP) adherend\u003c/h2\u003e \u003cp\u003eThe SDRP panel was fabricated in a random arrangement utilizing the hand lay-up method. Before fabrication, the treated sawdust was comminuted into powder form using a Los Angeles ball mill. The sawdust in powder form was then sieved through a mesh size of 150 \u0026micro;m with a mechanical shaker. The required quantity of sawdust, polyester 2597APT waxed and MEKP was calculated. 20% of the sawdust volume fraction was utilized. The same procedure used for making the KFRP was employed, except that the sawdust, polyester 2597APT waxed and the MEKP were mixed continuously in a bowl with a mechanical mixer until uniformity was achieved before the mixture was poured into a mold measuring 295mm x 210mm x 8mm. The thickness varied in the various tests conducted. The top mold or die, weighing 22 kg, was then gently placed on the mold, and the mixture was allowed to cure for 24 hours at room temperature. The panel was de-molded and post-cured in an oven at 70oC for 6 hours. Subsequently, the panel was machined to conform to the ASTM standards for each test. Some of the processes are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section3\"\u003e \u003ch2\u003e2.1.3 Fabrication of KFRP and SDRP double lap adhesive joints\u003c/h2\u003e \u003cp\u003eThe lap shear joint is the most often used joint type to examine the bonding properties of structural adhesive connections; the Double Lap Shear (DLS) was used to study the adhesive joint performance in this study since it reduces bending moments. Using the hand layup process, the kenaf fiber/polyester composite (KFRP) was self-made. The materials used for KFRP fabrication are; Kenaf fiber, polyester matrix, and MEKP as a catalyst. For unidirectional KFRP fabrication, a 40% mass fraction was used. The sawdust/polyester composite was created by randomly arranging the layup by hand. Sawdust, polyester matrix, and methyl ethyl ketone peroxide (MEKP) are the components utilized. 20% of the sawdust's mass fraction was used to fabricate the SDRP.\u003c/p\u003e \u003cp\u003eThe two KFRP adherends joined with the two SDRP adherends and underwent compressive testing. The total displacement of the joint was measured. The adhesive connection had a thickness of 0.2 mm. At least three identical samples were analyzed for every case. Several failure mechanisms were observed. Using a stainless wire insert approach, the thickness of the adhesive is held consistent across all joints. The adherends are aligned with care to generate symmetrical joints. The surfaces of the KFRP and SDRP adherends were completely abraded with sandpaper before bonding to improve the adhesive bond's efficacy. It was critical to thoroughly clean all bonding surfaces. Abrading the KFRP and SDRP adherends will get rid of any possible impurity in the bond. This was accomplished by carefully cleaning the surfaces with white tissue paper and then using acetone, an organic solvent that is commercially accessible. The cleaning substance was sprayed on the abraded surfaces and then wiped away using white tissue paper. When the cleaning was finished, the adherends had reference points marked on them to help in the alignment when clamping the specimens to the workbench as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. Polyester adhesive was used as the joint material. Specimens were clamped for 24 hours on the work table to cure. To create a solid, long-lasting bond, the adhesive bond must be post-cured in an oven. The specimens were heated for two hours to 70\u0026deg;C in a standard laboratory oven, as seen in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e. The oven was turned off after that time, and the specimens were removed and allowed to cool for 24 hours. This procedure of gently cooling the joints eliminates the formation of residual stresses and guarantees that the cure is complete. Using a scraper, all extra glue on the joints was scraped away, leaving a flat, smooth, level glue coating.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003c/div\u003e"},{"header":"3 Mechanical testing procedure","content":"\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e3.1 Tensile test of the KFRP adherend\u003c/h2\u003e \u003cp\u003eThe tensile test was carried out in compliance with ASTM D3039/D3039-14 test standard [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]. Five coupons were fashioned out from the cured unidirectional panel in the longitudinal direction. The standard recommended a dimension of 250 mm long by 25 mm wide. The thickness for all the coupons was held at 6 mm. The longitudinal and transverse strains were measured with two stain gauges attached at the middle of the gauge area of each coupon. The test was carried out with UTM (Shimadzu) with a load cell capacity of 250KN. The coupons were continuously loaded with a steady crosshead speed of 2 mm/min until failure. The tensile strength was obtained by dividing the load all over the area of the coupon, while the tensile modulus was calculated from the slope of the initial portion of the tensile stress-strain relation curve. The Poisson ratio was obtained by dividing the transverse strain by the longitudinal strain. The tensile test setup is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e(a), while the average stress-strain relation curve is presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e(b).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003e3.2 Tensile test of the SDRP adherend\u003c/h2\u003e \u003cp\u003eThe tensile test on the SDRP core material was performed in compliance with ASTM 638\u0026thinsp;\u0026minus;\u0026thinsp;14 standard test (ASTM, 2014) [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]. The coupons were prepared in the form of a dog-bone shape. To manufacture the required dog-bone shape, 5 coupons were fashioned out of the SDRP panel by grinding it to the required shape. The width of the coupon at the gauge length was lessened to 25 mm and a thickness of 8 mm. Then the coupon was mounted on the 250 KN capacity UTM(Schimadzu). An extensometer of 50 mm gauge length was attached to the center of the gauge length of the coupon to record the strain. A constant crosshead speed of 1 mm/min was used to apply the tensile load. The tensile strength was obtained by dividing the load by the area, while the tensile modulus was computed from the initial slope of the stress-strain expression curve. Figure\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e(a) shows the tensile test set-up and Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e(b) shows the average stress-strain curve.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003e3.3 Testing methods of KFRP and SDRP double lap adhesive joint\u003c/h2\u003e \u003cp\u003eThe testing method, material testing system, and relevant apparatus for joint investigation were carried out based on ASTMD905-03 (ASTM,1999) [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e], which is the accepted test procedure for adhesive bond strength characteristics in shear by compression loading, and a study conducted by [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e]. A universal testing machine (Tinius Olsen) with an in-store capacity of 3000 kN was used. This test was carried out at room temperature under displacement control at a constant head-speed loading rate of 1.27 mm/min up to failure. Figure\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e displays the schematic diagrams for the KFRP adherend and SDRP adherend double lap joint tests conducted in the lab. Four different overlap lengths with three different lap widths were tested according to similar research conducted by [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e]. An average of three replicas was tested for each of the configurations. The test was undertaken by placing a sample on a steel plate placed on the Tinius Olsen testing machine and applying direct compression load as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e. The data were recorded every 0.5 seconds. The force was measured and also the axial displacement was measured by the stroke.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe following equation was used to determine the high shear stress that the specimens experienced in the joint area during compression loading:\u003cdiv id=\"Equ1\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equ1\" name=\"EquationSource\"\u003e\n$$\\:{\\tau\\:}=\\frac{\\:{P}_{max}}{2A}$$\u003c/div\u003e\u003cdiv class=\"EquationNumber\"\u003e1\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003ewhere,\u003c/p\u003e \u003cp\u003e \u003cspan class=\"InlineEquation\"\u003e \u003cspan class=\"mathinline\"\u003e\\(\\:\\tau\\:\\)\u003c/span\u003e \u003c/span\u003e is the shear bond strength, \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:P\\)\u003c/span\u003e\u003c/span\u003e is the failure load, and \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:A\\)\u003c/span\u003e\u003c/span\u003e is the area of the bonded region of the DLS Joint FE Modeling.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003e3.4 Numerical modelling of double lab shear joint\u003c/h2\u003e \u003cp\u003eThe double lap adhesive joints were numerically modeled using the finite element method. The 3D finite element models were performed using the commercial finite element package ABAQUS/Standard to analyze the stress distribution and strength of the joints. The KFRP adherend, SDRP adherend, and polyester adhesive as the joint material constitute the three components of the double lap shear joint models. Models were created in ABAQUS/Standard with the same geometric dimensions, boundary conditions, and applied load as those tested in the laboratory. Table\u0026nbsp;1. presents the lengths, widths, and joint thicknesses for all the double lap shear joints modeled. Figure\u0026nbsp;8 shows the actual model of joint A1.\u003c/p\u003e \u003cp\u003eTable\u0026nbsp;1 Joint geometric configuration for double lap joints\u003c/p\u003e\u003ctable float=\"No\" id=\"Tabb\" border=\"1\"\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eJoint NO.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBond overlap (mm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eBond width (mm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eJoint thickness (mm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eNo. of Specimens\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eA1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eA2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eA3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eA4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eB1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e35\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eB2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e35\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eB3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e35\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eB4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e35\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eC1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eC2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eC3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e20\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eC4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003cp\u003eTo simulate the response within the adhesive joint, which is substantially thinner than the KFRP and SDRP adherents, the algorithm uses fracture mechanics, i.e. the energy required to form new surfaces. As a result, the cohesive elements, of the traction-separation law were evaluated. Figure\u0026nbsp;9 displays the traction-separation law in ABAQUS. Shear stress and peel stress in the joint might cause cohesive failure. The program employs fracture mechanics, or the energy needed to produce new surfaces, to mimic the response within the adhesive joint, which is far thinner than the KFRP and SDRP adherends. Consequently, the traction-separation law was assessed for the cohesive parts. Cohesive failure may result from the joint's shear and peel stresses. Consequently, the Quadratic Traction Damage Initiation Criterion (QUADSCRT), a mixed-mode failure criterion, was used for this investigation. The four traction-separation law damage initiation criteria of ABAQUS were used to create the mixed-mode failure criterion known as QUADSCRT. The maximum nominal stress criterion, maximum nominal strain criterion, quadratic nominal stress criterion, and quadratic nominal strain criterion are the four criteria. The material response is calculated using nominal stress to critical stress ratios for both damage criteria.\u003c/p\u003e \u003cp\u003e \u003cspan class=\"InlineEquation\"\u003e \u003cspan class=\"mathinline\"\u003e\\(\\:{T}_{n}^{0}\\)\u003c/span\u003e \u003c/span\u003e, \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{T}_{s}^{0}\\)\u003c/span\u003e\u003c/span\u003e, \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{T}_{t}^{0}\\)\u003c/span\u003e\u003c/span\u003e represents the critical nominal stresses where \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{T}_{n}\\)\u003c/span\u003e\u003c/span\u003e, \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{T}_{s}\\)\u003c/span\u003e\u003c/span\u003e, \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{T}_{t}\\)\u003c/span\u003e\u003c/span\u003e represent current nominal stress values in pure normal mode, first shear and second shear directions, respectively.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eMechanical properties of composites [\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e, \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e]\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"1\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eProperty\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eKenaf\u003c/p\u003e \u003cp\u003efiber Composite\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSawdust Composite\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eUnit\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\rho\\:}_{f}\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eg/cm\u003csup\u003e3\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eE\u003c/em\u003e\u003csub\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e21257.80\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2157\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eMPa\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eE\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2864.45\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2157\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eMPa\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eE\u003c/em\u003e\u003csub\u003e\u003cem\u003e3\u003c/em\u003e\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2864.45\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2157\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eMPa\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003csub\u003e\u003cem\u003eNuf12\u003c/em\u003e\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.32\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.37\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003csub\u003e\u003cem\u003eNuf13\u003c/em\u003e\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.32\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.37\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003csub\u003e\u003cem\u003eNuf23\u003c/em\u003e\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.34\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.37\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eG\u003c/em\u003e\u003csub\u003e\u003cem\u003e12\u003c/em\u003e\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1736.83\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e787\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eMPa\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eG\u003c/em\u003e\u003csub\u003e\u003cem\u003e13\u003c/em\u003e\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1736.83\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e787\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eMPa\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eG\u003c/em\u003e\u003csub\u003e\u003cem\u003e23\u003c/em\u003e\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1068.82\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e787\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eMPa\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabd\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eCharacteristics of the 2597APT polyester glue used in the simulation\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"2\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eProperty\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eValue\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\rho\\:\\)\u003c/span\u003e\u003c/span\u003e (g/cm\u003csup\u003e3\u003c/sup\u003e)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.232\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eE\u003c/em\u003e\u003csub\u003e\u003cem\u003em\u003c/em\u003e\u003c/sub\u003e (MPa)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2079\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eG\u003c/em\u003e\u003csub\u003e\u003cem\u003em\u003c/em\u003e\u003c/sub\u003e (MPa)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e776\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eV\u003c/em\u003e\u003csub\u003e\u003cem\u003em =\u003c/em\u003e\u003c/sub\u003e \u003cem\u003eV\u003c/em\u003e\u003csub\u003e\u003cem\u003e23\u003c/em\u003e\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.34\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eX\u003c/em\u003e\u003csub\u003e\u003cem\u003em\u003c/em\u003e\u003c/sub\u003e (MPa)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e38\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{t}_{n}^{0}\\)\u003c/span\u003e\u003c/span\u003e(MPa)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e54.76\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{t}_{s}^{0}\\)\u003c/span\u003e\u003c/span\u003e(MPa)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e20.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{t}_{t}^{0}\\)\u003c/span\u003e\u003c/span\u003e(MPa)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e20.5\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{G}_{IC}\\)\u003c/span\u003e\u003c/span\u003e(N/mm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e38\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{G}_{IIC}\\)\u003c/span\u003e\u003c/span\u003e(N/mm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e38\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{G}_{IIIC}\\)\u003c/span\u003e\u003c/span\u003e(N/mm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e38\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eThe adhesive layer and the joint's substrates were meshed using different meshes, which were joined by tie restrictions. Translational and rotational motion, along with all other active degrees of freedom, were restricted by applying equal nodes on both sides of the connection. Finer meshes are employed because of the tension concentration in the region around the adhesive layer. Due to the stress concentration surrounding the adhesive layer, finer meshes are used. To save computation time, coarse mesh is used for locations far from the adhesive layer. As a result, the adhesive layer was made up of an 8-node three-dimensional cohesive element (COH3D8), while the KFRP and SDRP adherents were made up of 8-node linear three-dimensional hexahedral elements with decreased integration (C3D8R) as shown in Fig.\u0026nbsp;10. In general, the KFRP adherend surface with larger stiffness is considered to be the master surface. The constraint ties the SDRP adherend surface as a slave surface. The master surface has the same motion by constraining each node on the slave surface. There was no damage to the KFRP adherend-adhesive and SDRP adherend-adhesive interfaces. As a result, for the aforementioned interfaces, a perfect bond was assumed. Figure\u0026nbsp;10 shows a typical example of the model meshes. Model A1 shown in Fig.\u0026nbsp;10 has a total number of 42225 elements with 69758 nodes. Model A2 has 42525 elements with 70070 nodes while model A3 has 54925 elements with 73986 nodes. Model A4 has a total number of 55975 elements with 75078 nodes. Model B1 has a total number of 77805 elements with 89532 nodes. Model B2 has a total number of 77980 elements with 89712 nodes. Others are model B3 with 80955 elements and 92952 nodes, model B4 has a total number of 84945 elements and 97236 nodes. Model C1 has a total number of 103750 elements with 118269 nodes. Model C2 has a total number of 104000 elements and 118524 nodes. Model C3 has a total number of 104600 elements with 119138 nodes and finally, model C4 with a total of 120700 elements and 137088 nodes.\u003c/p\u003e \u003cp\u003eThe same boundary conditions were applied to all the models of the double lab joints correlating to the fixture of the specimen tested in the laboratory. The surface of the bottom ends of the models was fixed using the \u0026lsquo;\u0026lsquo;\u0026rsquo; ENCASTRE\u0026rsquo;\u0026rsquo; option in ABAQUS with all degrees of freedom of the bottom surface constraint: (Ux\u0026thinsp;=\u0026thinsp;Uy\u0026thinsp;=\u0026thinsp;Uz\u0026thinsp;=\u0026thinsp;URx\u0026thinsp;=\u0026thinsp;URy\u0026thinsp;=\u0026thinsp;URz\u0026thinsp;=\u0026thinsp;0). The FE models' boundary conditions, applied loads, and geometrical dimensions matched those of the experiments exactly. Except Uy\u0026thinsp;\u0026ne;\u0026thinsp;0, all degrees of freedom at the top is thus (Ux\u0026thinsp;=\u0026thinsp;Uz\u0026thinsp;=\u0026thinsp;URx\u0026thinsp;=\u0026thinsp;URy\u0026thinsp;=\u0026thinsp;URz\u0026thinsp;=\u0026thinsp;0). Static and quasi-static analytic problems have been solved with ABAQUS/Standard solver. Nonlinear difficulties including geometric nonlinearity, material nonlinearity, and nonlinear boundary conditions are frequent and can make computations take a long time or even not converge. The combined failure analysis will be a huge challenge for the ABAQUS/Standard solver due to the complex material nonlinearity. The ABAQUS/Explicit solver has already been utilized for very efficient modelling of composite structural failures under quasi-static loads, despite its widespread application in transient response analysis [\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e]. The boundary condition and loading condition applied to the joints is shown in Fig.\u0026nbsp;11.\u003c/p\u003e "},{"header":"4 Results and discussion","content":"\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e \u003ch2\u003e4.1 Influence of joint parameters on joint strength and load-displacement response\u003c/h2\u003e \u003cp\u003eSpecimens were divided into three groups with four overlap lengths: 10 mm, 15 mm, 20 mm, and 25 mm, to evaluate the effect of overlap length on the load-displacement response of double lap joints. The bond widths of the three groups examined were 25 mm, 35 mm, and 50 mm, respectively. Figures\u0026nbsp;\u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e12\u003c/span\u003e, \u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e13\u003c/span\u003e, and \u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e14\u003c/span\u003e show the typical load-displacement curves for different overlap lengths with widths of 25 mm, 35 mm, and 50 mm, respectively. It is evident that the load-displacement curves for the majority of the joints exhibit nearly linear behavior at first, but this linearity was lost in the middle and then returned before failure. The curve abruptly fell when the joint's ultimate load capacity was achieved, signifying an abrupt failure. Three specimens were assessed for each group, and the figures display the load-displacement curve of the specimen whose load was closest to the average value. The figures show that increasing the overlap length in polyester adhesively bonded double lap shear joints increased their load-bearing and displacement capacity. From Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e4\u003c/span\u003e, it was discovered that as the overlap length was increased, the double lap shear joints provided a higher equivalent stiffness. Furthermore, the rate at which the joints' equivalent stiffness increases as overlap length increases are 20.59%, 29.41%, 50.88% for a bond width of 25 mm, 2.65%, 13.42%, 24.39% for a bond width of 35 mm and 1.19%, 11.94%, 20.75% for bond width 50 mm respectively. Therefore, as the overlap increases, the corresponding stiffness rate tends to increase as well.\u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e15\u003c/span\u003e displayed the lap shear strength as a function of bond width and overlap length. The applied load is distributed over a larger bond area, increasing the load. The increase rate of failure load with increasing overlap length is 29.95%, 47.86%, 75.21% for bond width 25 mm, 42.58%, 71.37%, 107.05% for bond width 35 mm, and 40.18%, 80.02%, and 117.83% for bond width of 50 mm respectively. However, as the overlap length of the joint increases, the connection between overlap length and joint shear strength displays an inverse relationship shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e15\u003c/span\u003e. This could be due to nonuniform stress distribution across the bond region, and increasing the overlap length reduces the center area of the joint where lower amounts of stress are sustained. The joint shear strengths with increasing overlap length saw a decrease of 13.43%, 26.00%, and 29.85% for bond width of 25 mm, 4.94%, 14.30%, 17.08% for bond width of 35 mm and 6.65%, 10.03%, 12.97% for bond width of 50 mm respectively from the baseline. A Similar pattern was obtained by [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e, \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e, \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e]. The statistical determination for the overview of the KFRP-SDRP shear joint test results is presented in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e4\u003c/span\u003e. Because the coefficient of variation for almost all the joints tested is less than 10%, the failure load, shear strength, displacement at failure load, and joint equivalent stiffness, the results from the three samples for each joint tested could be considered statistically acceptable.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eAn overview of the KFRP-SDRP shear joint test results\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eJoints No.\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSpecimen\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eFailure load (kN)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eDisplacement at Failure load (mm)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eShear strength\u003c/p\u003e \u003cp\u003e(MPa)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eJoint equivalent stiffness (kN/mm)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10-25-1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e5.416\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.670\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e10.832\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e3.243\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eA1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10-25-2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e5.652\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.8902\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e11.304\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e2.990\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10-25-3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e6.440\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.8500\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e12.880\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e3.481\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMean\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e5.836\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.8034\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e11.672\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e3.238\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eStd. Dev.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.536224\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.117263\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.072448\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.245538\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCoeff. Of Var. (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e9.188\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e6.502\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e9.188\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e7.583\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eA2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSpecimen\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eFailure load (kN)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eDisplacement at Failure load (mm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eShear strength (MPa)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eJoint equivalent stiffness (kN/mm)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e15-25-1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e8.1490\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.9102\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e11.600\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e4.266\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e15-25-2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7.1964\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.8272\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e9.595\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e3.938\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e15-25-3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7.600\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.9200\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e10.133\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e3.958\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMean\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7.648467\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.8858\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e10.44267\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e4.054\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eStd. Dev.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.478146\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.050985\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.037751\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.18387\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCoeff. Of Var. (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e6.251\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.704\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e9.938\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e4.536\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eA3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSpecimen\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eFailure load (kN)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eDisplacement at Failure load (mm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eShear strength (MPa)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eJoint equivalent stiffness (kN/mm)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e20-25-1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e8.700\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.1511\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e8.700\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e4.044\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e20-25-2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e8.338\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.049\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e8.338\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e4.069\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e20-25-3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e8.181\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.062\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e8.181\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e3.968\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMean\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e8.406333\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.087367\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e8.406333\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e4.027\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eStd. Dev.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.266162\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.055576\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.266162\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.052602\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCoeff. Of Var. (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3.166\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.662\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e3.166\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e1.306\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eA4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSpecimen\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eFailure load (kN)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eDisplacement at Failure load (mm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eShear strength (MPa)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eJoint equivalent stiffness (kN/mm)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e25-25-1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e10.701\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.1803\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e8.561\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e4.908\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e25-25-2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e9.527\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.2064\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e7.622\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e4.318\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e25-25-3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e9.7178\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.0820\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e7.774\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e4.668\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMean\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e9.981933\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.156233\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e7.985667\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e4.631333\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eStd. Dev.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.629995\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.065599\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.504016\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.296704\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCoeff. Of Var. (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e6.311\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3.042\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e6.311\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e6.406\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eB1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSpecimen\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eFailure load (kN)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eDisplacement at Failure load (mm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eShear strength (MPa)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eJoint equivalent stiffness (kN/mm)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10-35-1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7.220\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.6713\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e10.314\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e4.320\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10-35-2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7.110\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.6702\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e10.157\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e4.257\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10-35-3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e6.092\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.6008\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e8.703\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e3.805\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMean\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e6.807333\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.647433\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e9.724667\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e4.127333\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eStd. Dev.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.621934\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.040389\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.888265\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.280921\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCoeff. Of Var. (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e9.136\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.452\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e9.134\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e6.806\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eB2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSpecimen\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eFailure load (kN)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eDisplacement at Failure load (mm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eShear strength\u003c/p\u003e \u003cp\u003e(MPa)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eJoint equivalent stiffness (kN/mm)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e15-35-1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e9.260\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.7400\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e8.819\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e5.322\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e15-35-2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e9.080\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.7700\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e8.648\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e5.130\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e15-55-3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e8.160\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.8200\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e7.771\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e4.484\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMean\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e8.833333\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.776667\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e8.412667\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e4.978667\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eStd. Dev.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.590028\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.040415\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.562239\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.439019\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCoeff. Of Var. (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e6.679\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.274\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e6.683\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e8.818\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eB3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSpecimen\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eFailure load (kN)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eDisplacement at Failure load (mm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eShear strength (MPa)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eJoint equivalent stiffness (kN/mm)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e20-35-1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e10.3012\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.8001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e7.358\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e5.723\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e20-35-2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e12.6012\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.9000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e9.001\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e6.632\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e20-35-3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e12.1000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.0599\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e8.643\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e5.875\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMean\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e11.66747\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.92\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e8.334\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e6.076667\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eStd. Dev.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.209468\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.13105\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.863987\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.486901\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCoeff. Of Var. (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e10.366\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e6.826\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e10.367\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e8.013\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eB4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSpecimen\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eFailure load (kN)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eDisplacement at Failure load (mm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eShear strength (MPa)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eJoint equivalent stiffness (kN/mm)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e25-35-1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e14.7702\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.8605\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e8.440\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e7.939\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e25-35-2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e14.6021\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.9002\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e8.344\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e7.685\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e25-35-3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e12.8013\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.9401\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e7.315\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e6.598\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMean\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e14.05787\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.900267\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e8.033\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e7.407333\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eStd. Dev.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.09146\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.0398\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.623656\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.712316\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCoeff. Of Var. (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7.764\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.094\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e7.764\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e9.616\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eC1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSpecimen\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eFailure load (kN)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eDisplacement at Failure load (mm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eShear strength (MPa)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eJoint equivalent stiffness (kN/mm)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10-50-1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e9.240\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.8312\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e9.240\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e5.046\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10-50-2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e8.671\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.8311\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e8.671\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e4.585\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10-50-3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e8.382\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.6553\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e8.382\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e5.064\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMean\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e8.764333\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.772533\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e8.764333\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e4.898333\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eStd. Dev.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0.436548\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.101527\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.436548\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.271504\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCoeff. Of Var. (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4.981\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e5.728\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e4.981\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e5.543\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eC2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSpecimen\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eFailure load (kN)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eDisplacement at Failure load (mm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eShear strength (MPa)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eJoint equivalent stiffness (kN/mm)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e15-50-1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e13.680\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.8003\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e9.120\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e7.599\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e15-50-2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e12.240\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.8702\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e8.160\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e6.545\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e15-50-3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e11.330\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.7902\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e7.553\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e6.329\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMean\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e12.41667\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.820233\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e8.277667\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e6.824333\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eStd. Dev.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.184919\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.043566\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.790099\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.679518\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCoeff. Of Var. (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e9.542\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.393\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e9.545\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e9.957\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eC3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSpecimen\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eFailure load (kN)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eDisplacement at Failure load (mm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eShear strength (MPa)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eJoint equivalent stiffness (kN/mm)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e20-50-1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e17.201\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.9400\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e8.600\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e8.86649485\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e20-50-2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e15.650\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.0402\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e7.826\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e7.67081659\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e20-50-3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e15.049\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.9140\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e7.525\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e7.862591\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMean\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e15.96667\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.964733\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e7.983667\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e8.133301\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eStd. Dev.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.110398\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.066636\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.554572\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.642164\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCoeff. Of Var. (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e6.954\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3.378\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e6.946\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e7.8958\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eC4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSpecimen\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eFailure load (kN)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eDisplacement at Failure load (mm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eShear strength (MPa)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eJoint equivalent stiffness (kN/mm)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e25-50-1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e19.601\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.0701\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e7.840\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e8.30926\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e25-50-2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e17.601\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.0301\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e7.048\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e7.70898\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e25-50-3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e20.702\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.400\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e8.281\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e8.6254\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMean\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e19.30133\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.166733\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e7.723\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e8.214547\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eStd. Dev.\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.572069\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.203002\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.624771\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.465494\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eCoeff. Of Var. (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e8.145\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e9.369\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e8.089\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e5.667\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig13\" class=\"InternalRef\"\u003e16\u003c/span\u003e depicts the ultimate failure load as a function of overlap length and bond width to illustrate further the impact of overlaps on the failure load and lap shear strength. The area under the load-displacement responses was used to compute the corresponding energy absorption for all joints, and the results are reported in Fig.\u0026nbsp;\u003cspan refid=\"Fig15\" class=\"InternalRef\"\u003e17\u003c/span\u003e. Regarding energy absorption, a pattern resembling the failure load in Fig.\u0026nbsp;\u003cspan refid=\"Fig13\" class=\"InternalRef\"\u003e16\u003c/span\u003e is discernible across the different configurations. The Figs.\u0026nbsp;\u003cspan refid=\"Fig13\" class=\"InternalRef\"\u003e16\u003c/span\u003e and \u003cspan refid=\"Fig15\" class=\"InternalRef\"\u003e17\u003c/span\u003e demonstrate how the load-bearing capacity and energy absorption capacity of polyester adhesively bonded double lap shear joints increased with an increase in overlap length and bond width. Similar results pattern was obtained by [\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e, \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e, \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e].\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003e4.2 Failure mechaisms of double lap shear joints\u003c/h2\u003e \u003cp\u003eThe failure mechanisms of all the double lap joints occurred suddenly with no obvious sign or prior warnings. It was also observed that most of the specimens of the double lap joints failed in a brittle and sudden manner. Three failure modes were noticed for all the specimens tested under compression loading. There are (i) adhesive failure, this mode of failure occurs wherever the joint fails at the border amid the adhesive and the sandwich adherents; (ii) cohesive failure, this mode of failure happens inside the adhesive where the adhesive fractured; and (iii) adherend failure, this mode of failure occurred where the sandwich adherend fractured or failed. The failure mode for the double lap shear joints was dominated by cohesive failure with a few accompanying fiber pull-outs. An adhesive failure was noticed for specimens A1, and B2 in Fig.\u0026nbsp;\u003cspan refid=\"Fig18\" class=\"InternalRef\"\u003e18\u003c/span\u003e ( a) and Fig.\u0026nbsp;\u003cspan refid=\"Fig19\" class=\"InternalRef\"\u003e19\u003c/span\u003e (b), while cohesive failure was observed in A2, A3, A4, B1, B3, B4, C1, C2, and C3 in Fig.\u0026nbsp;\u003cspan refid=\"Fig18\" class=\"InternalRef\"\u003e18\u003c/span\u003e (b), (c) and (d), and Fig.\u0026nbsp;\u003cspan refid=\"Fig19\" class=\"InternalRef\"\u003e19\u003c/span\u003e (a), (c) and (d), and Fig.\u0026nbsp;\u003cspan refid=\"Fig20\" class=\"InternalRef\"\u003e20\u003c/span\u003e (a), (b), and (c) respectively. The failure of sandwich adherend was observed as the other mode of failure for the specimen in C4 (Fig.\u0026nbsp;\u003cspan refid=\"Fig20\" class=\"InternalRef\"\u003e20\u003c/span\u003e (d).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe failure behavior was influenced by the chemical bond created at the interface between a polymer adhesive and the sandwich adherents when the adhesive was cured. Adhesive failure occurred in A1 and B2 which suggested the formation of a weak chemical bond at the interface, a type of failure that is undesirable when a strong bond is anticipated. On the other hand, cohesive failure was noticed in A2, A3, A4, B1, B3, B4, C1, C2, and C3 which indicated a good chemical bond at the interface of the sandwich adherents and the polymer adhesive. A good adhesive bond is considered cohesive by most quality control criteria [\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e]. A more desirable mode of failure is the one observed in C4, which is called adherend failure. Here the sandwich joint not only ensures that the joint's maximum capacity is utilized, but also that the adherents and the polymer glue have a very strong relationship.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec15\" class=\"Section2\"\u003e \u003ch2\u003e4.3 Validation of FE models\u003c/h2\u003e \u003cp\u003eThe experimental load-displacement curves were compared with the simulated load-displacement plots for each joint as a function of overlap length and bond width. The simulated joints have the following dimensions: A1(10 mm x 25 mm), A2(15 mm x 25 mm), A3(20 mm x 25 mm), A4(25 mm x 25 mm), B1(10 mm x 35 mm), B2(15 mm x 35 mm), B3(20 mm x 35 mm), B4(25 mm x 35 mm), C1(10 mm x 50 mm), C2(15 mm x 50 mm), C3(20 mm x 50 mm) and C4(25 mm x 50 mm) are shown in Fig.\u0026nbsp;21 (a), (b), (c), (d), Fig.\u0026nbsp;\u003cspan refid=\"Fig21\" class=\"InternalRef\"\u003e22\u003c/span\u003e (a), (b), (c), (d), and Fig.\u0026nbsp;23 (a), (b), (c), (d) respectively. The load on the curves increased nonlinearly with increasing displacement until failure occurred for Joints A1, A2, A4, B1, B2, B3, B4, C2, C3, and C4, while joints A3 and C1 had almost linear curves until failure. It was also observed that most of the curves started linearly in progression which was lost mid-way and retained before failure. This may be due elastic-plastic behavior of the brittle adhesive material used. After the ultimate load was reached, the load-carrying capacity of all the joints dropped to zero, and the curve presented as a falling strength line. It was observed that the simulated failure load was slightly higher than the experimentally measured load for all the joint configurations. This phenomenon may not be far from manufacturing variability and instrumentational error. Despite these, it could be seen in terms of stiffness, ultimate load-bearing capacity, failure mechanism, and post-failure regime, the numerical curves correspond well with the experimental ones. Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e5\u003c/span\u003e shows the comparison of the numerical analysis with the experimental results. It can be observed that the numerical analysis and the experimental data were in good agreement. This phenomenon demonstrates the usefulness of the cohesive element in the numerical analysis of joints.\u003c/p\u003e \u003cp\u003eOne of the mechanical metrics used to evaluate the plastic deformation and fracture mechanisms of composite materials is the Mises equivalent stress. For lap shear joint models of joints A1 (10 mm x 25 mm), A2 (15 mm x 25 mm), A3 (20 mm x 25 mm), and A4 (25 mm x 25 mm), Fig.\u0026nbsp;24 displays the von Mises stress distribution contour plots. That of joints B1(10 mm x 35 mm), B2(15 mm x 35 mm), B3(20 mm x 35 mm) and B4(25 mm x 35 mm) are presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig22\" class=\"InternalRef\"\u003e25\u003c/span\u003e and joints C1(10 mm x 50 mm), C2(15 mm x 50 mm), C3(20 mm x 50 mm) and C4(25 mm x 50 mm) are shown in Fig.\u0026nbsp;26 respectively. For all of the joints, the highest stress occurred at the overlap edges, generating a concentration that initiates the damage, leading to cohesive crack development and fracture in the adhesive bond, according to the plots. The zone of maximum von Mises equivalent stress in the layer increases with increasing bonded area and load, indicating progressive bond failure as found experimentally. In addition, the majority of the joints showed the beginnings of failure in the bonded area, with slightly varied colors indicating some plastic deformation. The stress concentration near the borders of the bonded area, where the peel stress and shear stress are highest, explains this.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"No\" id=\"Tabk\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 5\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eNumerical analysis and experimental average failure loads and displacement of joints\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e\u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eJoints No\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eExperimental failure load, \u003cem\u003eF\u003c/em\u003e\u003csub\u003e\u003cem\u003eEXP\u003c/em\u003e\u003c/sub\u003e (failure mode)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eNumerical failure load, \u003cem\u003eF\u003c/em\u003e\u003csub\u003e\u003cem\u003eNUM\u003c/em\u003e\u003c/sub\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eFailure load, \u003cem\u003eF\u003c/em\u003e\u003csub\u003e\u003cem\u003eNUM\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e/ F\u003c/em\u003e\u003csub\u003e\u003cem\u003eEXP\u003c/em\u003e\u003c/sub\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eExperimental average displacement at failure load, \u003cem\u003eF\u003c/em\u003e\u003csub\u003e\u003cem\u003eEXP\u003c/em\u003e\u003c/sub\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eNumerical displacement at failure load, \u003cem\u003eF\u003c/em\u003e\u003csub\u003e\u003cem\u003eNUM\u003c/em\u003e\u003c/sub\u003e\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e(N)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e(N)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e(N)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e(mm)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e(mm)\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eA1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e5.84 (Adhesive)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e6.71\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.80\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e1.83\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eA2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e7.68 (Cohesive)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e8.53\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.86\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e1.88\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eA3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e8.41 (Cohesive)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e9.11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.08\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.09\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e2.08\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eA4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e10.00 (Cohesive)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e11.25\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.16\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e2.1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eB1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e6.81 (Cohesive)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e7.43\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.09\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.78\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e1.84\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eB2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e8.83 (Cohesive)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e10.08\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.92\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e2.09\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eB3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e11.67 (Cohesive)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e12.78\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.90\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e2.1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eB4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e14.10 (Cohesive)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e15.28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.77\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e2.19\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eC1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e8.76 (Cohesive)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e9.64\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.72\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e1.85\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eC2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e12.42 (Cohesive)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e13.96\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.82\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e2.12\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eC3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e15.96 (Cohesive)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e17.17\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.08\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e1.95\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e2.18\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eC4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e19.30 (Adherend)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e20.84\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.08\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e2.17\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e2.25\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec16\" class=\"Section2\"\u003e \u003ch2\u003e4.4 Adhesive layer stress distribution at various overlap lengths\u003c/h2\u003e \u003c/div\u003e \u003cdiv id=\"Sec17\" class=\"Section2\"\u003e \u003cp\u003eFigure 26 shows the stress distributions in double lap adhesive joint with KFRP adherend and SDRP adherend while using polyester 2597APT waxed as joint material under compression load. With a constant bond width of 25 mm, the shear stress (S13) and peel stress (S33) that concentrate over the overlap lengths of 10 mm, 15 mm, 20 mm, and 25 mm are simulated from ABAQUS FEM and explained. Widths of 35 mm and 50 mm were not considered in this section due to similar results. Figure\u0026nbsp;27 (a) shows the parabolic shear stress distribution curves for all the overlap lengths, seemingly, high stress levels appear to be concentrated near the two extremities of the overlaps, with lesser stress concentration in the center. The peak stress at the edge ends explains why failure always starts at the bonded region's end. As the overlap length rises, the overall shear stress level, including the peak shear stress at the end parts, decreases. This explains why the failure load increases in proportion to the overlap.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec18\" class=\"Section2\"\u003e \u003cp\u003eOn the other hand, shear stress decreases are not proportional to overlap length. The rate of reduction of the shear stress peak at the ends is not constant, but it decreases steadily as the overlap length grows. This explains why, as overlap length grows, joint strength decreases. A similar occurrence was reported in [\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e]. Figure\u0026nbsp;27 (b) shows the peel stress distribution curves over the entire overlap lengths. When overlap length increases, the maximum peel stress in the glue decreases and the distribution of stress tends to be uniform over the entire overlap length, except in the region at the edge end. This decrease in the peel stress which formed at the end of the overlap length enhanced the joint's load-bearing capacity. The absolute values of the maximum and minimum peel stress at the end of the edges were the same with both positive and negative values. A similar phenomenon was reported in [\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e]. The findings show that the stress distribution patterns in KFRP and SDRP double lap joints may be precisely described by the developed FEM.\u003c/p\u003e"},{"header":"5 conclusions","content":"\u003cp\u003eDouble lap adhesively bonded joints made of KFRP and SDRP under compressive loads were investigated through experimental and numerical analysis. The results are summarized as follows:\u003c/p\u003e \u003cp\u003e \u003col\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eThe load-displacement curves as a function of overlap lengths for most of the joints show almost linear behaviour from the beginning but linearity was lost mid-way and regained before failure.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eThe failure load is exactly proportionate to the overlap length. However, the shear bond strength is inversely proportionate to the overlap length. Also, the impact of bond width on the load-displacement curves increased slightly nonlinear with displacement for most of the curves with noticeable changes in stiffness. Three failure modes that were identified from the adhesive joint tests are: adhesive failure, cohesive failure, and adherend failure. However, cohesive failure dominates all the failure modes.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eThe ultimate failure load is proportional to the bond width here as well, although the bond shear strength is not. It was observed that by increasing overlap length and the bond width increased the load-carrying capacity and displacement capacity of the adhesively bonded joints.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eIn the case of the total energy absorbed amongst the various joint types, a tendency comparable to that of the ultimate failure load was seen, as well as an increase in joint stiffness.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eThe load-displacement response and stress distribution in adhesively bonded joints can be predicted using cohesive elements. When the failure loads derived from the experiments and numerical studies are compared, it can be observed that the experimental and numerical results are consistent. As the overlap length increased, the shear stress and the peel stress at the peak decreased on both edges and stress distribution was relatively much uniform.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eA considerable stress gradient is present near the overlap's ends, and the stress non-uniformity is made worse by a longer overlap length. The high-stress zone shifts from the end to the center of the bondline as the load increases, and the peel and shear stresses at the overlap edges are noticeably higher than those in the central region before the damage started in the adhesive. The shear in the central region is larger than the shear around the overlap edges because adhesive breakdown appears first close to the overlap edges. The findings from the experimental and numerical studies were consistent with each other.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003cspan\u003e \u003cli\u003e \u003cp\u003eTo better characterize the behavior of the materials under various situations and time scales, more research is needed, such as exposing the KFRP-SDRP adhesively joint to high temperatures and environmental conditions for long-term durability. This could aid in further research into the sustainability and long-term performance of bio-composite joints. Lastly, Video microscopy may be better integrated into the analysis of bond line behavior in KFRP and SDRP sandwich double lap joints so that data can be reliably recorded and utilized as another method of assessing crack initiation strain in the adhesive layer.\u003c/p\u003e \u003c/li\u003e \u003c/span\u003e \u003c/ol\u003e \u003c/p\u003e"},{"header":"List of abbreviations","content":"\u003cp\u003eKFRP \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;Kenaf fiber reinforced polymer\u003c/p\u003e\n\u003cp\u003eSDRP \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;Sawdust reinforced polymer\u003c/p\u003e\n\u003cp\u003eDLJ \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; Double lap joint\u003c/p\u003e\n\u003cp\u003eDLS \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;Double lap shear\u003c/p\u003e\n\u003cp\u003eWPC \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; Wood polymer composite\u003c/p\u003e\n\u003cp\u003eFE \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;\u0026nbsp;\u0026nbsp; Finite element\u003c/p\u003e\n\u003cp\u003eFEM \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;Finite element method\u003c/p\u003e\n\u003cp\u003eGFRP \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;Glass Fiber Reinforced Polymer\u003c/p\u003e\n\u003cp\u003eNKTB \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; National kenaf and tobacco board\u003c/p\u003e\n\u003cp\u003eMEKP \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; Methyl Ethyl Ketone Peroxide\u003c/p\u003e\n\u003cp\u003eASTM \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; America society for testing materials\u003c/p\u003e\n\u003cp\u003eUD \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;Unidirectional\u003c/p\u003e\n\u003cp\u003eUTM \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; Universal testing machine\u003c/p\u003e\n\u003cp\u003eMPa \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;Megapascal\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eKN \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;Kilonewton\u003c/p\u003e\n\u003cp\u003eMm \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; Millimeters\u003c/p\u003e\n\u003cp\u003eQUADSCRT \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;Quadratic traction damage initiation criterion\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u0026tau; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;Shear\u003c/p\u003e\n\u003cp\u003eP \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;Load\u003c/p\u003e\n\u003cp\u003eA \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; Area\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u0026rho;\u003cem\u003e\u003csub\u003ef\u003c/sub\u003e\u003c/em\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; Density of kenal fiber composite\u003c/p\u003e\n\u003cp\u003eE1= E2= E3 \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;Young moduli \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eG12 = G13= G23 \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;Shear moduli\u003c/p\u003e\n\u003cp\u003eNuf12= Nuf13= Nuf23 \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; Poisson ratios\u003c/p\u003e\n\u003cp\u003ep \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;Density of Polyester Polymer\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eE\u003csub\u003em\u003c/sub\u003e\u003c/em\u003e\u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; Young modulus of polyester polymer\u003c/p\u003e\n\u003cp\u003eGm \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;Shear modulus of polyester polymer\u003c/p\u003e\n\u003cp\u003eVm \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;Poisson ratio of polyester polymer\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAvailability of data\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe dataset used and analyzed during the current study are available from the corresponding author upon reasonable request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ecompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declared that none potentials conflicts of interests or personal relationships could have affected the research we did for this study.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics, consent to participate\u0026nbsp;\u003c/strong\u003eNot applicable\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent to publish\u0026nbsp;\u003c/strong\u003eNot applicable\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have not received any funding for this research work\u003cstrong\u003e.\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors’ contribution\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAMA: Conceptualization, methodology and original draft writing and review. \u0026nbsp;IA: Methodology, writing and review. UA: Writing and review. NAK: Supervision and editing. All authors read and approved the final manuscript\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors gracefully acknowledged the project supported by Ministry of Higher Education Malaysia.\u0026nbsp;\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eRamakrishnan KR, Sarlin E, Kanerva M, Hokka M. \u0026ldquo;Experimental study of adhesively bonded natural fibre composite \u0026ndash; steel hybrid laminates,\u0026rdquo; \u003cem\u003eCompos. Part C Open Access\u003c/em\u003e, vol. 5, p. 100157, Jul. 2021, doi: 10.1016/J.JCOMC.2021.100157.\u003c/li\u003e\n\u003cli\u003eOzankaya G. \u003cem\u003eet al.\u003c/em\u003e, \u0026ldquo;Prediction of lap shear strength of GNP and TiO2/epoxy nanocomposite adhesives,\u0026rdquo; \u003cem\u003eNanotechnol. Rev.\u003c/em\u003e, vol. 12, no. 1, 2023, doi: 10.1515/ntrev-2023-0134.\u003c/li\u003e\n\u003cli\u003eLi H, Xu S, Zhang Z, Song C. \u0026ldquo;Experimental and numerical investigation on the corrosion effects on the bonding behavior between CFRP and steel,\u0026rdquo; \u003cem\u003eCompos. Struct.\u003c/em\u003e, vol. 259, p. 113465, Mar. 2021, doi: 10.1016/J.COMPSTRUCT.2020.113465.\u003c/li\u003e\n\u003cli\u003eCeren Yildirim MY, Hasan Ulus, Bertan Beylergil, Abdulrahman Al-Nadhari, Serra Topal, \u0026ldquo;Tailoring adherend surfaces for enhanced bonding in CF/PEKK composites: Comparative analysis of atmospheric plasma activation and conventional treatments,\u0026rdquo; \u003cem\u003eCompos. Part A Appl. Sci. Manuf.\u003c/em\u003e, vol. 180, no. 108101, 2024, doi: https://doi.org/10.1016/j.compositesa.2024.108101.\u003c/li\u003e\n\u003cli\u003eHalil Burak Kaybal HU. \u0026ldquo;Comparative analysis of thermoplastic and thermoset adhesives performance and the influence on failure analysis in jointed elium-based composite structures,\u0026rdquo; pp. 3474\u0026ndash;3492, 2023.\u003c/li\u003e\n\u003cli\u003eMarchione P, Munafo F. \u0026ldquo;Effect of thermal aging on the mechanical performance of timber-timber single-lap adhesive joints,\u0026rdquo; \u003cem\u003eInt. J. Adhes. Adhes.\u003c/em\u003e, vol. 108, no. 102883., 2021, doi: https://doi.org/10.1016/j.ijadhadh.2021.102883.\u003c/li\u003e\n\u003cli\u003eCampilho RDSG, Moura DC, Gon\u0026ccedil;alves DJSJ, Da Silva FMG, Banea MD,. Da Silva LFM. \u0026ldquo;Fracture toughness determination of adhesive and co-cured joints in natural fibre composites,\u0026rdquo; \u003cem\u003eCompos. Part B Eng.\u003c/em\u003e, vol. 50, pp. 120\u0026ndash;126, Jul. 2013, doi: 10.1016/J.COMPOSITESB.2013.01.025.\u003c/li\u003e\n\u003cli\u003eDelzendehrooy Ayatollahi FMR, Akhavan-Safar A, da Silva LFM. \u0026ldquo;Strength improvement of adhesively bonded single lap joints with date palm fibers: Effect of type, size, treatment method and density of fibers,\u0026rdquo; \u003cem\u003eCompos. Part B Eng.\u003c/em\u003e, vol. 188, p. 107874, May 2020, doi: 10.1016/J.COMPOSITESB.2020.107874.\u003c/li\u003e\n\u003cli\u003eRussian O, Belarbi KSA, Dawood M. \u0026ldquo;Effect of surface preparation technique on bond behavior of CFRP-steeldouble-lap joints: Experimental and numerical studies,\u0026rdquo; \u003cem\u003eCompos. Struct.\u003c/em\u003e, vol. 255, no. 113048, pp. 1\u0026ndash;13, 2021.\u003c/li\u003e\n\u003cli\u003eSong MG, \u003cem\u003eet al.\u003c/em\u003e, \u0026ldquo;Effect of manufacturing methods on the shear strength of composite single-lap bonded joints,\u0026rdquo; \u003cem\u003eCompos. Struct.\u003c/em\u003e, vol. 92, no. 9, pp. 2194\u0026ndash;2202, Aug. 2010, doi: 10.1016/J.COMPSTRUCT.2009.08.041.\u003c/li\u003e\n\u003cli\u003eYang G, Yang T, Yuan W, Du Y. \u0026ldquo;The influence of surface treatment on the tensile properties of carbon fiber-reinforced epoxy composites-bonded joints,\u0026rdquo; \u003cem\u003eCompos. Part B Eng.\u003c/em\u003e, vol. 160, pp. 446\u0026ndash;456, Mar. 2019, doi: 10.1016/J.COMPOSITESB.2018.12.095.\u003c/li\u003e\n\u003cli\u003eAna\u0026ccedil; N. \u0026ldquo;The Effect of Organic Fillers on the Mechanical Strength of the,\u0026rdquo; 2023.\u003c/li\u003e\n\u003cli\u003eAdole MA, Yatim JM, Abubakar SR, Azzmi NM. \u0026ldquo;Potentials of Wood Fibre Reinforced Polymeric Composites,\u0026rdquo; \u003cem\u003eJ. Polym. Sci. Technol.\u003c/em\u003e, vol. 3, no. 1, pp. 19\u0026ndash;31, 2018.\u003c/li\u003e\n\u003cli\u003eAdole MA, Yatim JM, Abubakar SR, Othman A, Mizal NA. \u0026ldquo;Kenaf Fibre and Its Bio-Based Composites: A Conspectus,\u0026rdquo; \u003cem\u003ePertanika J. Sci. Technol.\u003c/em\u003e, vol. 27, no. 1, pp. 297\u0026ndash;329, 2019.\u003c/li\u003e\n\u003cli\u003eKhakpour H, Ayatollahi MR, Akhavan-Safar A, da Silva LFM. \u0026ldquo;Mechanical properties of structural adhesives enhanced with natural date palm tree fibers: Effects of length, density and fiber type,\u0026rdquo; \u003cem\u003eCompos. Struct.\u003c/em\u003e, vol. 237, p. 111950, Apr. 2020, doi: 10.1016/J.COMPSTRUCT.2020.111950.\u003c/li\u003e\n\u003cli\u003eAiza Jaafar CN, Zainol IN, Ishak S, Ilyas RA, Sapuan SM. \u0026ldquo;Effects of the Liquid Natural Rubber (LNR) on Mechanical Properties and Microstructure of Epoxy/Silica/Kenaf Hybrid Composite for Potential Automotive Applications,\u0026rdquo; \u003cem\u003eJ. Mater. Res. Technol.\u003c/em\u003e, vol. 12, pp. 1026\u0026ndash;1038, May 2021, doi: 10.1016/j.jmrt.2021.03.020.\u003c/li\u003e\n\u003cli\u003eBharath Raman N, , Ramnath Vijaya VR, Manoharan B. \u0026ldquo;Kenaf Fibre Reinforced Composites: A Review.,\u0026rdquo; \u003cem\u003eARPN J. Eng. Appl. Sci.\u003c/em\u003e, vol. 10, no. 13, pp. 5483\u0026ndash;5485, 2015.\u003c/li\u003e\n\u003cli\u003eKhan A. \u003cem\u003eet al.\u003c/em\u003e, \u0026ldquo;Extraction and characterization of vetiver grass (Chrysopogon zizanioides) and kenaf fiber (Hibiscus cannabinus) as reinforcement materials for epoxy based composite structures,\u0026rdquo; \u003cem\u003eJ. Mater. Res. Technol.\u003c/em\u003e, vol. 9, no. 1, pp. 773\u0026ndash;778, Jan. 2020, doi: 10.1016/J.JMRT.2019.11.017.\u003c/li\u003e\n\u003cli\u003eMahjoub R, Yatim JM, Mohd Sam AR, Hashemi SH. \u0026ldquo;Tensile properties of kenaf fiber due to various conditions of chemical fiber surface modifications,\u0026rdquo; \u003cem\u003eConstr. Build. Mater.\u003c/em\u003e, vol. 55, pp. 103\u0026ndash;113, Mar. 2014, doi: 10.1016/J.CONBUILDMAT.2014.01.036.\u003c/li\u003e\n\u003cli\u003eAbidin NMZ. \u003cem\u003eet al.\u003c/em\u003e, \u0026ldquo;The evaluation of the mechanical properties of glass, kenaf, and honeycomb fiber-reinforced composite,\u0026rdquo; \u003cem\u003eRev. Adv. Mater. Sci.\u003c/em\u003e, vol. 62, no. 1, 2023, doi: 10.1515/rams-2022-0299.\u003c/li\u003e\n\u003cli\u003eUzoma AE, Nwaeche CF, Al-Amin M, Muniru OS, Olatunji O, Nzeh SO. \u0026ldquo;Development of Interior and Exterior Automotive Plastics Parts Using Kenaf Fiber Reinforced Polymer Composite,\u0026rdquo; \u003cem\u003eEng\u003c/em\u003e, vol. 4, no. 2, pp. 1698\u0026ndash;1710, 2023, doi: 10.3390/eng4020096.\u003c/li\u003e\n\u003cli\u003eMitchelle AJ. \u0026ldquo;Composites of commercial wood pulp fibres and cement,\u0026rdquo; \u003cem\u003eAppita\u003c/em\u003e, vol. 33, no. 6, pp. 461\u0026ndash;463, 1986.\u003c/li\u003e\n\u003cli\u003eNashino T, Hireo K, Kotera M, Nakamae K, Inagaki K. \u0026ldquo;Kenaf reinforced biodegradable composite.,\u0026rdquo; \u003cem\u003eCompos. Sci. Technol.\u003c/em\u003e, vol. 63, no. 9, pp. 1281\u0026ndash;1286, 2003.\u003c/li\u003e\n\u003cli\u003eKaraduman Y, Onal L. \u0026ldquo;Flexural behavior of commingled jute/polypropylene nonwoven fabric reinforced sandwich composites,\u0026rdquo; \u003cem\u003eCompos. Part B Eng.\u003c/em\u003e, vol. 93, pp. 12\u0026ndash;25, May 2016, doi: 10.1016/J.COMPOSITESB.2016.02.055.\u003c/li\u003e\n\u003cli\u003eMadyan OA, Wang Y, Corker J, Zhou Y, Du G, Fan M. \u0026ldquo;Classification of wood fibre geometry and its behaviour in wood poly(lactic acid) composites,\u0026rdquo; \u003cem\u003eCompos. Part A Appl. Sci. Manuf.\u003c/em\u003e, vol. 133, p. 105871, Jun. 2020, doi: 10.1016/j.compositesa.2020.105871.\u003c/li\u003e\n\u003cli\u003eIchazo M, Albano C, Gonz\u0026aacute;lez J, Perera R, Candal M. \u0026ldquo;Polypropylene/wood flour composites: treatments and properties,\u0026rdquo; \u003cem\u003eCompos. Struct.\u003c/em\u003e, vol. 54, no. 2\u0026ndash;3, pp. 207\u0026ndash;214, Nov. 2001, doi: 10.1016/S0263-8223(01)00089-7.\u003c/li\u003e\n\u003cli\u003eRamalho LDC, Campilho RDSG, Belinha J, da Silva LFM. \u0026ldquo;Static strength prediction of adhesive joints: A review,\u0026rdquo; \u003cem\u003eInt. J. Adhes. Adhes.\u003c/em\u003e, vol. 96, no. 102451, pp. 1\u0026ndash;18, 2020.\u003c/li\u003e\n\u003cli\u003eLee BH, Kim HJ, Yui WR. \u0026ldquo;Fabrication of long and discontinuous natural fiber reinforced polypropylene bio-composites and their properties,\u0026rdquo; \u003cem\u003eFibers Polym.\u003c/em\u003e, vol. 10, no. 1, pp. 83\u0026ndash;90, 2009.\u003c/li\u003e\n\u003cli\u003eG\u0026uuml;ltekin K, Akpinar S, \u0026Ouml;zel A. \u0026ldquo;The effect of the adherend width on the strength of adhesively bonded single-lap joint: Experimental and numerical analysis,\u0026rdquo; \u003cem\u003eCompos. Part B Eng.\u003c/em\u003e, vol. 60, pp. 736\u0026ndash;745, Apr. 2014, doi: 10.1016/J.COMPOSITESB.2014.01.022.\u003c/li\u003e\n\u003cli\u003eASTM, \u0026ldquo;Standard test method for tensile properties of polymer matrix composite materials,\u0026rdquo; in \u003cem\u003eASTM D3039/D 3039M.\u003c/em\u003e, 2014.\u003c/li\u003e\n\u003cli\u003eASTM, \u0026ldquo;Standard test method for tensile properties of plastics,\u0026rdquo; in \u003cem\u003eASTM International. Designation: D. 638, 1-13\u003c/em\u003e, 2014.\u003c/li\u003e\n\u003cli\u003eAmerican Society for Testing and Materials, \u0026ldquo;ASTM D 905, Standard Test Method for Strength Properties of Adhesive Bonds in Shear by Compression Loading,\u0026rdquo; \u003cem\u003eAssembly\u003c/em\u003e, vol. 04, no. Reapproved, pp. 7\u0026ndash;10, 1999.\u003c/li\u003e\n\u003cli\u003eFerdous W, Manalo A, Aravinthan T. \u0026ldquo;Bond behaviour of composite sandwich panel and epoxy polymer matrix: Taguchi design of experiments and theoretical predictions,\u0026rdquo; \u003cem\u003eConstr. Build. Mater.\u003c/em\u003e, vol. 145, pp. 76\u0026ndash;87, Aug. 2017, doi: 10.1016/J.CONBUILDMAT.2017.03.244.\u003c/li\u003e\n\u003cli\u003eBarbosa NGC, Campilho RDSG, Silva FJG, Moreira RDF. \u0026ldquo;Comparison of different adhesively‑bonded joint types for mechanical structures,\u0026rdquo; \u003cem\u003eAppl. Adhes. Sci.\u003c/em\u003e, vol. 6, no. 15, pp. 1\u0026ndash;19, 2018.\u003c/li\u003e\n\u003cli\u003eADOLE AM. \u0026ldquo;Effect of Fiber Orientation on the Tensile Properties of Kenaf Fiber Reinforced Polyester Composite,\u0026rdquo; \u003cem\u003eJ. Environ. Sci.\u003c/em\u003e, vol. 23, no. 2, pp. 12\u0026ndash;23, 2024.\u003c/li\u003e\n\u003cli\u003eAdole AM. \u0026ldquo;Influence of Fiber Loading on the Tensile and Physical Properties of Sawdust Reinforced Unsaturated Polyester Composite,\u0026rdquo; \u003cem\u003eJ. Environ. Des.\u003c/em\u003e, vol. 20, no. 2, pp. 17\u0026ndash;23, 2024.\u003c/li\u003e\n\u003cli\u003eSun CL, Li CY, Tie Y, Hou, Duan Y. \u0026ldquo;Experimental and numerical investigations of adhesively bonded CFRP single-lap joints subjected to tensile loads,\u0026rdquo; \u003cem\u003eInt. J. Adhes. Ahesives\u003c/em\u003e, vol. 95, no. 102402, pp. 1\u0026ndash;14, 2019.\u003c/li\u003e\n\u003cli\u003eKanani A. Y. Hou, X. Laidlaw R, Ye J. \u0026ldquo;The effect of joint configuration on the strength and stress distributions of dissimilar adhesively bonded joints,\u0026rdquo; \u003cem\u003eEng. Struct.\u003c/em\u003e, vol. 226, no. 111322, pp. 1\u0026ndash;11, 2021.\u003c/li\u003e\n\u003cli\u003eHartsfield M. \u003cem\u003eet al.\u003c/em\u003e, \u0026ldquo;Dissimilar material joining of densified superwood to aluminum by adhesive bonding,\u0026rdquo; \u003cem\u003eInt. J. Adv. Manuf. Technol.\u003c/em\u003e, vol. 131, no. 1, pp. 425\u0026ndash;436, 2024, doi: 10.1007/s00170-024-13155-0.\u003c/li\u003e\n\u003cli\u003eRussian O, Khan S, Belarbi A, Dawood M. \u0026ldquo;Effect of surface preparation technique on bond behavior of CFRP-steel double-lap joints: Experimental and numerical studies,\u0026rdquo; \u003cem\u003eCompos. Struct.\u003c/em\u003e, vol. 255, p. 113048, Jan. 2021, doi: 10.1016/J.COMPSTRUCT.2020.113048.\u003c/li\u003e\n\u003cli\u003eKatsiropoulos CV, Chamos AN, Tserpes KL, Pantelakis SG. \u0026ldquo;Fracture Aerospace, toughness and shear behaviour of composite bonded joints based on a novel Adhesive,\u0026rdquo; \u003cem\u003eCompos. Part B Eng.\u003c/em\u003e, vol. 43, no. 3, pp. 24\u0026ndash;248, 2012.\u003c/li\u003e\n\u003cli\u003eVelayutham S, Sugiman S, Ahmad H, Jaini ZM. \u0026ldquo;Shear Strength of Adhesively Bonded Joint with Toughened Epoxy Mussel Powder,\u0026rdquo; \u003cem\u003eInt. J. Integr. Eng.\u003c/em\u003e, vol. 16, no. 1, pp. 201\u0026ndash;212, 2024, doi: 10.30880/ijie.2024.16.01.016.\u003c/li\u003e\n\u003cli\u003eARABAĞ DK, TEKKANAT MA. ANA\u0026Ccedil; N. KO\u0026Ccedil;AR O. \u0026ldquo;Investigation of adhesive bonding strength of wood added PLA materials,\u0026rdquo; \u003cem\u003eMobilya ve Ahşap Malzeme Araştırmaları Derg.\u003c/em\u003e, vol. 6, no. 1, pp. 26\u0026ndash;38, 2023, doi: 10.33725/mamad.1304449.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"discover-civil-engineering","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [Discover Civil Engineering](https://www.springer.com/journal/44290)","snPcode":"44290","submissionUrl":"https://submission.nature.com/new-submission/44290","title":"Discover Civil Engineering","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Discover Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Kenaf fiber, sawdust, polyester adhesive, bio-composites, adhesive bonded joint, FEM","lastPublishedDoi":"10.21203/rs.3.rs-5836800/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-5836800/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eNatural fiber-based polymeric composites are widely used in a wide range of engineering applications, therefore a complete understanding of the behavior of these materials' adhesively bonded joints is required to ensure their efficiency, safety, and dependability. The single lap joint has garnered a lot of attention, but the double lap joint arrangement has received very little attention. This study aims to look into the bond performance of Kenaf Fiber Reinforced Polymer (KFRP) and Sawdust Reinforced Polymer (SDRP) utilizing the Double Lap Joint (DLJ) arrangement. To accomplish this, the kenaf fiber-polyester adherend was manufactured in a unidirectional pattern with a fiber weight fraction of 40%, while the sawdust-polyester adherend was made in a random pattern with a fiber weight fraction of 20%. The DLS joints were made with various joint geometrics, polyester adhesive as the bond material, and direct vertical compression load was applied. Finite element modelling was used to check and validate the laboratory data. It was discovered that increasing the lap length improves the load support capability of the adhesive joints while decreasing joint shear strength. The finite element results were consistent with the laboratory data, and the utilization of KFRP and SDRP in bonded adhesive assemblies showed promise for structural applications.\u003c/p\u003e","manuscriptTitle":"Experimental and numerical investigation of double lap adhesively bonded joints composed of KFRP and SDRP subjected to compressive loads","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-05-02 07:06:08","doi":"10.21203/rs.3.rs-5836800/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"checksComplete","content":"","date":"2025-04-29T07:37:03+00:00","index":"","fulltext":""},{"type":"submitted","content":"Discover Civil Engineering","date":"2025-04-16T15:14:53+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"discover-civil-engineering","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [Discover Civil Engineering](https://www.springer.com/journal/44290)","snPcode":"44290","submissionUrl":"https://submission.nature.com/new-submission/44290","title":"Discover Civil Engineering","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Discover Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"ecdbfc79-8255-4ea1-9e45-7bc77d5e49c8","owner":[],"postedDate":"May 2nd, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"in-revision","subjectAreas":[],"tags":[],"updatedAt":"2025-05-02T07:06:08+00:00","versionOfRecord":[],"versionCreatedAt":"2025-05-02 07:06:08","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-5836800","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-5836800","identity":"rs-5836800","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}