Experimental Investigation of Tensile and Buckling Behavior of FDM-Fabricated ABS and PLA Lattice Structures with Varying Unit Cell Geometries

Experimental Investigation of Tensile and Buckling Behavior of FDM-Fabricated ABS and PLA Lattice Structures with Varying Unit Cell Geometries | 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 Investigation of Tensile and Buckling Behavior of FDM-Fabricated ABS and PLA Lattice Structures with Varying Unit Cell Geometries BURAK ŞAHİN This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8345845/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Lattice structures produced via additive manufacturing (AM) have attracted substantial interest in aerospace, biomedical and automotive industries due to their superior strength-to-weight ratio and energy absorption ability. However, these cellular structures are inherently prone to buckling under compressive loading because of their open-cell geometries and slender struts. Buckling not only initiates premature structural failure but also severely limits the load-bearing capability and reliability of such structures in critical applications. While previous research has extensively explored tensile and compressive behavior, systematic and comparative investigation into the buckling performance of polymer based AM lattices remains scarce. This study addresses this gap by experimentally evaluating both tensile and buckling responses of lattice structures fabricated from ABS (Acrylonitrile Butadiene Styrene) and PLA (Polylactic Acid) using Fused Deposition Modeling (FDM). Three different unit cell geometries of square, hexagonal and octagonal with two strut thicknesses (0.5 mm and 1.0 mm) were investigated to understand the combined effects of lattice structure, material and strut thickness. The results reveal that both tensile strength and buckling resistance are significantly influenced by strut thickness and material type. PLA demonstrated superior performance over ABS particularly in terms of critical buckling loads with the most pronounced improvements observed in hexagonal lattices due to their stretch-dominated structure. These findings underscore the critical role of buckling in determining the structural integrity of AM lattice designs and offer essential insights for optimizing geometry and material selection to enhance stability and reliability in load-bearing applications. Lattice structure buckling tensile loading additive manufacturing ABS PLA 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 Highlights Lattice structures Buckling behavior of lattice structures Tensile behavior of lattice structures Unit cell design Strut thickness Mechanical performance of lattice structures Comparison of tensile and buckling for strut thickness of lattice structures Comparison of tensile and buckling load for ABS and PLA lattice structures Comparison of tensile and buckling load of square, hexagon and octagon for lattice structures 1. Introduction Lattice structures having porous type forms has aroused huge attention and been used for several fields of aerospace, automotive, medical due to potentials of energy absorption, performance enhancement and efficiency increase. Lattice structures are also preferred in several industries due to their high strength to weight ratio and high energy absorbing ability [ 1 ]. These structures are in cellular type forms which are difficult and almost impossible to produce by conventional manufacturing methods. Lattice structures of 2.5D (Fig. 1 a) and 3D (Fig. 1 b) are generated in construction by interlinking components of unit cells (Fig. 1 c) combining beams, trusses, walls and plates. However, despite their advantages, lattice structures are inherently susceptible to buckling due to their slender struts and open-cell geometries. Buckling is a leading cause of structural instability in these systems, particularly under compressive or axial loads, and can result in premature failure, reduced load-bearing capacity, and compromised energy absorption. Therefore, understanding the buckling behavior of lattice structures is crucial in optimizing their design and ensuring safe and reliable performance in practical applications. Lattice structures have found opportunity to be produced from metallic or plastic materials by additive manufacturing (AM) which leads to energy, material and time saving [ 2 , 3 ]. Additive manufacturing gives chance to produce the prototypes before mass production and end-use (net shape) products without using too many tools and high amount of waste material [ 4 ]. The main advantage of additive manufacturing is to produce complex geometries which can not be manufactured or can be manufactured difficultly by substractive methods. Due to these advantages, lattice structures which can be possible to produce by AM is used for several industries including aerospace applications. Similar to other engineering structures exposed to compressive loads, buckling causes instability problems which can be source of catastrophic failures for lattice structures due to their thin layered design. Majority of previous works [ 5 – 13 ] were focused on tensile and compressive behavior of lattice structures. The effects of the printing defects on mechanical properties of additively manufactured were also studied by some authors [ 14 – 16 ]. There were also several studies [ 17 – 21 ] were conducted for investigation of additive manufacturing process parameters. On the other hand, buckling behavior of lattice structures was surprisingly neglected by the researchers. Cerardi et al. [ 8 ] conducted FEA and experimental studies (tensile tests to determine stiffness and tensile strength) for lattice structures of polyamide with different porosity percentage (40%-80%) produced by laser sintering technologies. Ductile behavior was observed for all specimens due to porous form during tensile tests. In the study reported by Chacón et al. [ 22 ], PLA specimens manufactured by fused deposition modeling (FDM) in different orientations such as upright, flat and on edge were tested to evaluate the effects of build orientation on strength and stiffness values of 3D printed parts. Higher strength and stiffness values were obtained for flat and on edge orientations compared to upright one by conducting tensile and 3 point bending tests. Previous two orientations show ductile behavior whereas upright one has brittle manner in fracture. This study shows the importance of printing orientations on anisotropic behavior of 3D printed specimens. Li et al. [ 9 ] carried out a study to investigate mechanical behaviours of aircraft’s U shaped bearing ring formed with X, Kagoma, pyramid unit structure additively fabricated from aluminum alloy by numerical and experimental methods. Their comparative study found that 30% mass per unit volume reduction by applying lattice structure design compared to honeycomb structure. The behaviour of stainless steel cellular structures under uniaxial compression load was searched experimentally by Li et al. [ 10 ]. Local plastic stress-strain around joints of lattice unit cells and self contact of struts during compression tests was observed. Their findings indicated that the unit cell structure is significant for overall stiffness, strength and energy absoption of lattice structures. In the study of Al Rifaie et al.[ 11 ], compression behavior of 3D printed body center cubic (BCC) and BCC with vertical struts added to all nodes lattices made from ABS were investigated. Higher compressive load carrying capacity was obtained for lattice with vertical struts. Qin et al. [ 12 ] studied the effects of addition inorganic calcium carbonate (CaCO3) and calcium phosphate (TCP) fillers into PLA matrix on the compressive load bearing and energy absorption capacities for additively manufactured cubic and triply periodic minimal surfaces-diamond (TPMS-D) lattices. Below addition of 20% of infillers increases the tensile strength of PLA but more cause to decrease. %10 addition yields in best compressive load carrying capacity and energy absorption. Few authors [ 2 , 23 – 26 ] studied the buckling behaviours of lattice structures. Dong and Fan [ 23 ] made experimental and numerical research to determine buckling load and energy absorption of hexagonal lattice thin tube made from AISI 316 L by loading in X, Y and Z directions. Mean crushing force was determined by numerical work and experiments for several wall thicknesses. Dong et al. [ 24 ] conducted a study to investigate the buckling behavior of meta lattice structure for different center angles of 0 to 120°. Three different printed specimens of PLA were tested for compressive, buckling and crushing behaviors. Energy values for bending and membrane were determined analytically and experimentally with a difference of 12%. Nazir et al. [ 2 ] made experimental and numerical research to evaluate critical buckling load of cubic, inclined cubic, vertical inclined and octet truss lattice columns. Buckling and post buckling were taken into consideration for various lattice structures. They found that inclined structures have higher resistance against instability due to compressive loads. In the study conducted by Babacan and Şeremet [ 26 ], face centered cubic with exterior and interior vertical struts for Co-Cr alloys designed and manufactured using selective laser melting were tested under uniaxial compressive loading. Local buckling and densification were observed during compression tests for lattice structures. Authors stated that 17% higher load carrying capacity under compressive loads was obtained in face centered cubic lattice structure with vertical struts. Lattice structures with their cellular and porous form offer significant advantages such as high strength-to-weight ratio, enhanced energy absorption, and efficient mechanical performance features that are highly desirable in aerospace, automotive and biomedical engineering applications. However, their structural efficiency is often constrained by their less resistance against buckling due to the slender struts and open-cell configurations intrinsic to their design. As stated earlier, buckling is a leading cause of instability in lattice structures, making its characteristics crucial for understanding and ensuring their structural integrity. With the advancement of additive manufacturing technologies, the fabrication of such complex geometries has become increasingly feasible, emphasizing the need for a thorough understanding of their buckling behavior to ensure reliability in practical applications. In this regard, optimizing design parameters such as unit cell geometry, strut thickness and material type is essential for enhancing structural stability and preventing early onset of buckling under compressive loading. This study constitutes the first paper of an extensive research effort aimed at determining key mechanical performance parameters of lattice structures and exploring their suitability in advanced engineering applications. A particular focus was placed on experimentally investigating the buckling behavior of lattice structures manufactured from ABS and PLA having square, hexagonal and octagonal unit cell geometries. Critical buckling loads were determined under axial compression and tests were extended beyond the initial buckling point to evaluate the post-buckling response. These findings establish a fundamental framework for understanding the influence of geometrical configurations and material properties on the buckling resistance of lattice structures, thereby contributing to the development of design strategies that ensure their safe and reliable performance in load-bearing applications. In the first part of this study, tensile tests were carried out on lattice structures composed of square, hexagonal and octagonal unit cell geometries manufactured from ABS and PLA materials to investigate the effects of cell geometry and material type on tensile performance. In the second part, experimental buckling tests were conducted on the same lattice configurations under axial compressive loading to evaluate their critical buckling loads and post-buckling behavior. The results obtained from both mechanical tests aim to provide a comprehensive understanding of the structural response of lattice structures and serve as a foundation for future design and application. 2. Materials and Methods In this study, lattice structures were designed with three different unit cell geometries: square, hexagonal and octagonal (Fig. 2 a). The lattice specimens were constructed by repeating and interlinking unit cells consisting of struts arranged in regular patterns. Two thermoplastic materials commonly used in additive manufacturing were selected for the fabrication process: ABS and PLA (Fig. 2 b and 2 c). These materials were chosen due to their distinct mechanical characteristics and widespread application in lightweight structural components. The lattice specimens were produced using a fused deposition modeling (FDM) 3D printer. For each geometry and material combination, two different strut thicknesses (0.5 mm and 1.0 mm) were implemented to investigate the influence of relative density on mechanical behavior. The printing parameters were kept constant throughout the production process to minimize variability: nozzle temperature of 220°C for PLA and 240°C for ABS, and bed temperature of 60°C. After fabrication, the specimens were visually inspected to ensure dimensional consistency and to check for defects such as delamination or voids. Mechanical behavior of the lattice structures was evaluated through both tensile and buckling tests, carried out in a sequential experiments. Initially, uniaxial tensile tests were conducted to determine the tensile strength, elongation and stiffness of the different lattice configurations. All tests were performed at room temperature using a universal testing machine (Shimadzu AGS-X 50 kN). The crosshead displacement rate was set to 2 mm/min and displacement data were recorded continuously until final failure. To ensure reliability and repeatability of the results, a minimum of three specimens were tested for each configuration. Following the tensile testing, buckling experiments were conducted under axial compressive loading to evaluate the critical buckling load and post-buckling behavior of the specimens. The same testing machine was utilized by fitting with compression platens to ensure uniform load application. A constant displacement rate of 1.0 mm/min was applied until substantial lateral deformation or structural collapse occurred. 3. Results and Discussion The primary objective of this study is to experimentally investigate the tensile and buckling behavior of beams incorporating 2.5D lattice structures fabricated via additive manufacturing. In this context, detailed results from both tensile and axial compression tests are presented and discussed in detail. The tensile performance and buckling behavior of lattice structures were evaluated for different unit cell geometries of square, hexagonal and octagonal produced using ABS and PLA materials. For each geometry-material combination, specimens with two different strut thicknesses (0.5 mm and 1.0 mm) were tested to assess the influence of unit cell configuration and relative density on critical buckling load, ultimate tensile strength, stiffness and elongation. 3.1 Tensile Test Results Tensile test specimens (Fig. 2 a) along with lattice structures composed of square, hexagonal and octagonal unit cells having two distinct strut thicknesses (0.5 mm and 1.0 mm) were designed in compliance with ISO 527-4:2023(E) and fabricated using the Fused Deposition Modeling (FDM) technique. Both ABS (Fig. 2 b) and PLA (Fig. 2 c) materials were used for additive manufacturing to evaluate the mechanical properties of the lattice structures. Tensile tests were performed using a Shimadzu AGS-X universal testing machine with a 50 kN load capacity at a constant crosshead speed of 2 mm/min by following procedures similar to those reported in previous studies [ 2 , 13 , 25 ]. Tensile load versus elongation curves for lattice test specimens with unit cells fabricated from ABS and PLA are shown in Figs. 3a–3b (square), 3c–3d (hexagon) and 3e–3f (octagon). For ABS square lattice specimens (Fig. 3a), the ultimate tensile load increased from 383.65 N to 593.07 N as the strut thickness was increased from 0.5 mm to 1.0 mm. This trend is consistent with the findings reported by Torrado and Roberson [ 28 ], highlighting the importance of optimized geometry in enhancing the tensile properties of FDM-printed ABS structures. Square-based unit cells are particularly known by their moderate stiffness and strength compared to other lattice geometries. A similar trend was observed in PLA specimens (Fig. 3b), where the load bearing capacity increased from 673.29 N to 1124.16 N as the strut dimension increased from 0.5 mm to 1.0 mm. This significant enhancement in mechanical performance is attributed to the increased cross-sectional area, structural stiffness, load bearing capacity and load distribution capabilities under tensile loading. PLA exhibited a substantially higher maximum tensile load (673.29 N) compared to ABS (383.65 N), showing a 75.5% improvement in load-bearing capacity for 0.5 mm strut thickness. Similarly, PLA again outperformed ABS with a maximum tensile load of 1124.16 N versus 593.07 N, corresponding to an 89.5% increase for 1.0 mm strut thickness (Fig. 4). These findings confirm that PLA provides superior tensile performance relative to ABS for square lattice structures regardless of the strut dimension. As expected, the maximum tensile load increases by depending on strut dimension increase regardless of material type. The difference between maximum tensile load values of ABS and PLA was observed for both strut dimensions (0.5 mm and 1.0 mm). PLA lattice beams exhibited higher maximum tensile loads and greater elongation values compared to ABS at both strut dimensions. PLA has inherently superior mechanical characteristics in the lattice geometries due to its higher rigidity and better layer adhesion in FDM printing. Although PLA is known to exhibit brittle behavior, the results indicate that its stiffness advantage plays a dominant role in load-bearing performance for the lattice structures. As seen in Figs. 3a and 3b, both ABS and PLA specimens exhibit a sudden drop in load following the ultimate strength point, a characteristic response associated with brittle fracture mechanisms. Compared to ABS, PLA exhibits higher toughness as an evidence of its greater load-bearing capacity and elongation before failure. Tensile load versus elongation curves were presented for hexagonal lattice structures with two strut dimensions of 0.5 mm and 1.0 mm produced for ABS and PLA respectively in Fig. 3c and 3d. Hexagonal lattices offer a distinct mechanical response due to their stretch-dominated architecture which influences both stiffness and failure modes compared to square lattice. For the ABS hexagonal lattice structure, the increase in strut thickness from 0.5 mm to 1.0 mm resulted in a substantial improvement in tensile performance. The specimen with 0.5 mm struts exhibited a maximum tensile load of 248.05 N, whereas the 1.0 mm counterpart reached 747.22 N. Depending on strut thickness increase, corresponding increase in ultimate load is 200% approximately. This improvement can be regarded to the greater cross-sectional area and the improved structural stability provided by the thicker struts. For PLA, the maximum tensile load increased from 368.67 N (0.5 mm) to 1245.10 N (1.0 mm) with an increase of 237.73% (Fig. 4b). Compared to ABS specimens, PLA hexagonal lattices (0.5 mm) exhibited significantly higher tensile load. The energy absorption in hexagonal lattice allow PLA to reach higher tensile limits before brittle fracture initiates. Furthermore, this structure reduces stress concentrations typically associated with crack initiation in brittle polymers. In accordance with literature, stretch-dominated structures such as hexagon lattice tend to exhibit more efficient load transfer across the structure especially when fabricated with sufficient strut thickness. Hexagonal lattices provide improved toughness under tensile loading due to their inherent geometric redundancy compared to square lattice [ 29 ]. Figure 3e and 3f show the tensile load–elongation response of 3D-printed octagonal lattice structures using ABS (Fig. 3e) and PLA (Fig. 3f) with two strut thicknesses: 0.5 mm and 1.0 mm. For ABS specimens, the increase in strut thickness from 0.5 mm to 1.0 mm led to a significant improvement in load bearing capacity. The specimen with 0.5 mm struts reached a maximum load of 395.81 N, whereas the 1.0 mm counterpart achieved 636.86 N corresponding to 60.9% increase in ultimate tensile load. PLA octagonal lattices demonstrated similar enhancements observed for ABS lattices. The peak tensile load rose from 587.78 N (0.5 mm) to 1076.52 N (1.0 mm), representing an 83.15% increase in load-bearing capacity. The enhanced performance with increased strut thickness is consistent with the role of relative density (the ratio of the density of the lattice structure to that of the base material) and the contribution of strut cross-sectional area to improved load transfer and structural stiffness in lattice structures. Additionally, the octagonal geometry offers a hybrid mechanical behavior between bending-dominated and stretch-dominated structures with notable trends in both materials depending on strut thickness. Particularly, compared to square cells, the octagonal unit cell design provides more complex load paths resulting gradual failure behavior and improved energy dissipation capacity, especially when struts are sufficiently thick to avoid local buckling. Across all configurations, PLA exhibited higher ultimate tensile loads than ABS, which can be due to its greater stiffness and higher Young’s modulus under quasi-static loading (Fig. 4). When comparing geometries within the same material, octagonal lattices outperformed square lattices but were slightly less effective than hexagonal lattices in terms of ultimate tensile load. This observation supports the classification of octagonal structures show hybrid mechanical behavior between bending-dominated and stretch-dominated structures. According to a reference work [ 29 ], these types of geometries exhibit intermediate mechanical responses by combining the ductility of bending-dominated designs (like squares) and the strength of stretch-dominated designs (like hexagons). Figure 4 shows the combined effect of material type, unit cell geometry, and strut thickness on the ultimate tensile performance of lattice structures. Across all geometries and materials, increasing the strut thickness from 0.5 mm to 1.0 mm resulted in a significant increase in maximum tensile load. This trend is consistent with previous findings [ 29 ], where enhanced cross-sectional area directly contributes to increased load-bearing capacity due to reduced stress concentrations and improved stiffness. 3.2 Buckling Test Results Similar to tensile test specimens, each group of buckling test specimens include three different lattice structures of square, hexagon and octagon having strut thickness values of 0.5 mm and 1.0 mm were prepared as shown in Fig. 5 . Buckling tests were conducted for beams under fixed-fixed end condition by using Shimadzu AGS-X 50 kN. In this study, the specimens with a strut thickness of 0.5 mm are designated as S1, S2, and S3, while those with a strut thickness of 1.0 mm are referred to as S7, S8 and S9. The progressive damage mechanisms of the first square unit cell lattice specimens with a 0.5 mm strut thickness for both ABS and PLA which were subjected to buckling tests are illustrated step by step in Fig. 6 . Figure 6 a represents the specimen S1 (ABS) before loading. Initial buckling was observed in one of the unit cells of the lattice structure marking the onset of structural instability (Fig. 6 b). As the compressive load increased, the unit cell began to fold (Fig. 6 c), and this deformation gradually progressed throughout the structure (Fig. 6 d). The folding process was completed resulting in significant structural distortion as illustrated in Fig. 6 e. By further loading, the collapse of the folded unit cells led to the formation of cracks indicating the start of material failure (Fig. 6 f and 6 g). Although the estimation of maximum (critical) load at buckling initiation is sufficient for the scope of this research, the compressive load was further increased to observe post buckling behavior of lattice structure under compressive load up to the complete structural failure. Specimens S7, S8 and S9 (with 1.0 mm strut thickness) are shown in their pre-test condition in Figs. 7 a.1, 7a.3, and 7a.7 respectively. The onset of buckling is illustrated in Figs. 7 a.4 and 7a.8, while the subsequent folding of unit cells is depicted in Figs. 7 a.2, 7a.6, 7a.9 and 7a.10. The buckling tests for PLA square unit cell lattice specimens commenced with sample S1 as shown in Fig. 7 b. Initial buckling within the lattice structure was observed indicating the onset of instability (Fig. 7 b.2). As the compressive load increased, progressive folding of the unit cells occurred as illustrated in Figs. 7 b.3 and 7b.4. Similar deformation patterns and damage progression were observed for specimens S2 and S3. For specimen of S2, folding and structural distortion are presented in Figs. 7 b.5, 7b.6 and 7b.7, while the sequence of buckling and folding stages for S3 is depicted in Figs. 7 b.8 through 7b.10. The buckling behavior of specimens S7, S8 and S9 (PLA) is illustrated in Fig. 7 c. The initiation of buckling in the unit cell structures was identified for specimens S7, S8 and S9 in Figs. 7 c.1-7c.3, 7c.5–7c.6, and 7c.8 respectively. Following the initial buckling, progressive folding of the unit cells was observed, as shown in Fig. 7 c.4 for S7, Fig. 7 c.7 for S8, and Fig. 7 c.10 for S9. The buckling load–deformation curves for square unit cell lattice specimens with strut thicknesses of 0.5 mm and 1.0 mm for ABS and PLA were obtained and are presented in Figs. 8a and 8b respectively. Understandably, increasing the strut thickness from 0.5 mm to 1.0 mm in ABS specimens leads to enhanced structural stability under buckling. The 0.5 mm of ABS specimens exhibit pronounced lateral deformation and early onset of localized buckling. In contrast, 1.0 mm strut thickness ABS specimens (Fig. 7 a) display a more uniform load-bearing response with delayed and less severe buckling features. This observation is in strong agreement with the findings of Choy et al. [ 30 ], who demonstrated that increasing the strut diameter in lattice structures significantly enhanced compressive stiffness and shifted the failure mode from abrupt shear collapse to a more gradual and layer-wise deformation. These results suggest that the beneficial effects of increased strut thickness on structural stability are not only pronounced in metallic lattices but are also valid for polymer-based lattice structures fabricated by additive manufacturing methods such as Fused Deposition Modeling (FDM). Similar to ABS, PLA lattice structures with 1.0 mm struts exhibit superior buckling resistance compared to their 0.5 mm strut thickness as observed in Fig. 7 b and 7 c. Additionally, a comparison between the ABS and PLA suggests that PLA specimens generally maintain their structural integrity better than ABS particularly at higher strut thicknesses. The buckling load versus deformation results for square unit cell lattice structures reveal a clear influence of both material type and strut thickness on structural stability under compressive loading (Fig. 8). ABS and PLA specimens having strut thickness of 0.5 mm demonstrated critical loads of 200.70 N and 408.85 N respectively. This indicates that PLA exhibits slightly higher buckling resistance than ABS at smaller strut dimensions due to its moderate stiffness and energy absorption characteristics. Interestingly, while the critical buckling load for ABS remained nearly unchanged at 408.85 N when the strut thickness increased to 1.0 mm, PLA showed a substantial enhancement in performance. The PLA specimen with 1.0 mm struts achieved a significantly higher buckling load of 695.78 N, representing a 70% increase compared to its 0.5 mm counterpart. This result suggests that PLA benefits more notably from increased structural rigidity when the cross-sectional area is enlarged. The findings highlight that PLA outperforms ABS at higher strut thicknesses in terms of buckling resistance for square lattice geometries, likely due to its higher elastic modulus and improved layer adhesion during the additive manufacturing process. Figures 9 illustrates the buckling behavior of hexagonal unit cell lattice structures for ABS and PLA materials having strut thicknesses of 0.5 mm and 1.0 mm. The thinner ABS specimens (0.5 mm) were firstly buckled under compressive load (Fig. 9 a.1, 9a.3 and 9a.5) and then folding of buckled unit cell emerged as square one (Fig. 9 a.2, 9a.4 and 9a.6). In addition, specimens with strut thickness of 1.0 mm (S7-S8-S9) were tested; buckling started (Fig. 9 b.1, 9b.3 and 9b.5) and progressed (Fig. 9 b.2, 9b.4 and 9b.6). The 0.5 mm strut thickness specimens exhibit obvious lateral deflections and buckling modes at relatively low compressive loads. This behavior is particularly evident in both ABS and PLA indicating that thinner struts lack sufficient rigidity to sustain higher loads without premature instability (Fig. 9 a). In contrast, the 1.0 mm thick specimens (Fig. 9 b) demonstrate a significantly delayed onset of buckling characterized by less severe lateral displacement. This is consistent with the increased moment of inertia and axial stiffness imparted by the thicker struts, which shows improved buckling resistance in lattice structures with increased strut diameter. Buckling load curves are presented for hexagon unit cell specimens of ABS and PLA with 0.5 mm thickness (S1-S2-S3) and 1.0 mm (S7-S8-S9) in Fig. 10. The mechanical response curves given in Fig. 10 further substantiate visual observations for steps of buckling occurance seen in Fig. 9 a and 9 b. Buckling behavior for both materials across thickness variations are seen in Fig. 10. For ABS, the 0.5 mm specimens reached the critical buckling load of approximately 110 N, while the 1.0 mm struts had around 270 N. In the case of PLA, thicker struts had the critical buckling load of approximately 600 N which is significantly higher than their thinner specimens having only about 200 N. As expected from analytical axial buckling formulations, increasing thickness improves critical buckling load in elastic buckling significantly for polymer lattice structures. Results show that increasing strut thickness from 0.5 to 1.0 mm nearly doubled the buckling load for ABS and tripled it for PLA. Notably, PLA consistently outperformed ABS, which correlates with its higher modulus and strength in FDM printed structures. The relatively higher buckling capacity of PLA is attributable to its greater stiffness and tensile strength compared to ABS, as also highlighted in prior studies [ 5 , 31 ]. After hexagon unit cell collapse, lattice structure continues to carry load under the effect of the post buckling for 1.0 mm thick specimens. This increase is not very effective for thinner specimens compared to thicker ones due to fracture of unit cell during folding and disengagement of cell wall from the unit cell. Overall, the results clearly demonstrate that both material selection and strut thickness critically influence the buckling performance of hexagonal lattice structures. Increasing the strut diameter not only enhances load-bearing capacity but also postpones the onset of instability, contributing to improved structural reliability. These observations are in agreement with the established Euler buckling theory and recent experimental work on architected lattice metamaterials. Gibson & Ashby’s model predicts buckling strength dependency on relative density and strut slenderness, which our results support [ 29 ]. Völlmecke et al. [ 32 ] showed hexagonal lattices primarily fail via vertical-ligament elastic buckling, which matches our observed buckling morphology. Joseph et al. [ 33 ] demonstrated that both process parameters and base material (ABS/PLA) significantly influence compressive stiffness and buckling. In addition to square and hexagon, octagon lattice specimens having 0.5 mm and 1.0 mm strut thickness for both ABS and PLA were also tested under compressive load to determine buckling behaviour (Fig. 11 a and 11 b). Each series (S1–S3 for 0.5 mm, S7–S9 for 1.0 mm) demonstrates a clear progression in structural stability depending on material and strut thickness. Similar to hexagonal lattices, the deformation behavior under axial compression is strongly dependent on both geometry and material type. Figure 11 a.1-11a.6 show that ABS specimens with 0.5 mm struts experience substantial lateral deformation and buckling as in case of the typical of slender structures with low bending stiffness. PLA specimens (Fig. 11 a.7–12) show relatively linear profiles in the pre-buckling stage and collapse more abruptly in later stages likely due to PLA lattice specimens’ higher stiffness but lower ductility. Specimens with thicker struts (1.0 mm) exhibit higher resistance to buckling (Fig. 11 b). Their failure occurs at greater loads and the PLA specimens show more brittle and sudden failure in agreement with findings in Dawoud et al. and Tymrak et al. [ 5 , 31 ], where PLA outperforms ABS in stiffness but not in deformation capacity. The visual post-buckling modes are consistent with studies on cellular solids, where increased strut thickness shifts the buckling mechanism from elastic instability to material yielding or fracture [ 29 ]. This qualitative interpretation is further supported by the quantitative results presented in Fig. 12. ABS octagonal lattices with 0.5 mm strut thickness reached a critical buckling load of around 110 N, while increasing the strut thickness to 1.0 mm raised the critical buckling load to 260 N approximately before exhibiting a gradual decline in the post-buckling region. Compared to ABS specimens, PLA octagonal lattices demonstrated significantly higher critical buckling loads of 220 N and 700 N for 0.5 mm and 1.0 mm strut thickness respectively. This substantial increase is attributed to PLA’s higher stiffness and elastic modulus. 4. Conclusion and Discussion This experimental investigation comprehensively characterized the mechanical performance of lattice structures fabricated via FDM with emphasis on the effects of unit cell geometry (square, hexagonal, octagonal), material type (ABS and PLA), and strut thickness (0.5 mm and 1.0 mm) under both tensile and compressive (buckling) loading conditions. The key findings of this study demonstrate that increasing the strut thickness from 0.5 mm to 1.0 mm resulted in substantial improvements in the ultimate tensile load across all lattice geometries and materials. PLA specimens consistently exhibited higher tensile strength with the most pronounced enhancements observed in hexagonal lattices compared to ABS. This superior performance is attributed to the stretch-dominated architecture of the hexagonal lattice which facilitates efficient load transfer and energy dissipation. The buckling load capacity of the lattice structures exhibited strong dependence on both material characteristics and strut thickness. Increasing the strut thickness effectively delayed the onset of buckling and minimized post-buckling deformations leading to improved structural stability. PLA outperformed ABS in buckling performance particularly at higher strut thicknesses, due to its higher elastic modulus and improved interlayer bonding resulting from the FDM process. Among the investigated lattice types, hexagonal unit cells showed the highest mechanical efficiency under both tensile and compressive loading conditions owing to their stretch-dominated deformation behavior. Octagonal structures exhibited intermediate characteristics between bending and stretch-dominated responses, whereas square lattices governed primarily by bending deformation and demonstrated comparatively lower mechanical performance. Despite its inherently brittle nature, PLA displayed greater structural stability and outperformed ABS in both tensile and buckling tests. This behavior is in alignment with buckling theory and is supported by recent studies on lattice and cellular structures. In conclusion, this study highlights the critical role of unit cell geometry, material selection and strut thickness in defining the mechanical performance and structural integrity of additively manufactured lattice structures. The results form a framework for the design and optimization of such structures in engineering applications where high tensile strength and buckling resistance are essential. These insights are expected to guide future research in the development of predictive models and the design of high-performance lattice structures for lightweight and load-bearing applications. Declarations Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Funding information This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors. Author Contribution The author was responsible for the conceptualization of the study, experimental design, specimen fabrication, data acquisition, data analysis and interpretation, as well as manuscript preparation and revision. The author approved the final manuscript. Data availability Data will be made available on request. References Voicu AD, Hadăr A, Vlăsceanu D (2021) Benefits of 3D printing technologies for aerospace lattice structures. Sci Bulletin'Mircea cel Batran'Naval Acad, 24(1) Nazir A, Arshad AB, Jeng J-Y (2019) Buckling and post-buckling behavior of uniform and variable-density lattice columns fabricated using additive manufacturing. Materials 12(21):3539 Maconachie T et al (2019) SLM lattice structures: Properties, performance, applications and challenges. Mater Design 183:108137 Khosravani MR et al (2022) Characterization of 3D-printed PLA parts with different raster orientations and printing speeds. 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Compos Adv Mater 30:26349833211003904 Joseph A, Mahesh V, Mahesh V (2023) Effect of loading rates on the in-plane compressive properties of additively manufactured ABS and PLA-based hexagonal honeycomb structures. J Thermoplast Compos Mater 36(3):1113–1134 Additional Declarations No competing interests reported. Supplementary Files additionalfigures.png Cite Share Download PDF Status: Posted Version 1 posted 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. We do this by developing innovative software and high quality services for the global research community. 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4","display":"","copyAsset":false,"role":"figure","size":50442,"visible":true,"origin":"","legend":"\u003cp\u003eMaximum Tensile Load Charts\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-8345845/v1/b71bc6905fa959c61729bb97.png"},{"id":98624652,"identity":"765100d7-e05e-4725-b28a-47ba45b3c05a","added_by":"auto","created_at":"2025-12-19 17:08:37","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":432484,"visible":true,"origin":"","legend":"\u003cp\u003eBuckling Test Specimens of Square, Hexagon and Octagon Unit Cell Lattices of ABS and PLA (Before Test)\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-8345845/v1/2bce383be027d31cb6c00682.png"},{"id":98624244,"identity":"0136fab6-4a13-417b-b760-c392212bc4db","added_by":"auto","created_at":"2025-12-19 17:08:12","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":593806,"visible":true,"origin":"","legend":"\u003cp\u003eBuckling Steps of Square Unit Cell Lattice Specimens of S1 (ABS and PLA)\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-8345845/v1/f9bd6b1b7209cea0393bd0c6.png"},{"id":98625107,"identity":"6d7906ca-12e5-485d-a08b-e2905825c519","added_by":"auto","created_at":"2025-12-19 17:08:56","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":488726,"visible":true,"origin":"","legend":"\u003cp\u003eBuckling Test Specimens of Square Unit Cell Lattice (ABS and PLA)\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-8345845/v1/c856078ada4476fcec0fac57.png"},{"id":98507581,"identity":"9079d001-e03f-453d-83d7-aac30bc6bc19","added_by":"auto","created_at":"2025-12-18 10:58:22","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":46800,"visible":true,"origin":"","legend":"\u003cp\u003eBuckling Load vs Deformation of Square Unit Cell Lattice Specimens (ABS and PLA)\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-8345845/v1/d68ad39b5d6d40933bc47b6a.png"},{"id":98625649,"identity":"1882a6d5-0d83-498a-b6b2-658f72801d9d","added_by":"auto","created_at":"2025-12-19 17:09:15","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":653893,"visible":true,"origin":"","legend":"\u003cp\u003eBuckling Test Specimens of Hexagon Unit Cell Lattice (ABS and PLA)\u003c/p\u003e","description":"","filename":"9.png","url":"https://assets-eu.researchsquare.com/files/rs-8345845/v1/7b8c0f378fabb6e34ad440bf.png"},{"id":98507583,"identity":"209806ec-00d8-4dac-9f22-f9e9547e431a","added_by":"auto","created_at":"2025-12-18 10:58:22","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":52859,"visible":true,"origin":"","legend":"\u003cp\u003eBuckling Load vs Elongation Curves for Hexagon Unit Cell Lattice Specimens (ABS and PLA)\u003c/p\u003e","description":"","filename":"10.png","url":"https://assets-eu.researchsquare.com/files/rs-8345845/v1/f7673674638eac4a69b7d2fc.png"},{"id":98623942,"identity":"264856a0-69d1-4ae6-a435-e555c78547e4","added_by":"auto","created_at":"2025-12-19 17:07:48","extension":"png","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":575713,"visible":true,"origin":"","legend":"\u003cp\u003eBuckling Test Specimens of Octagon Unit Cell Lattice (ABS and PLA)\u003c/p\u003e","description":"","filename":"11.png","url":"https://assets-eu.researchsquare.com/files/rs-8345845/v1/681955358448d747d70c6bfa.png"},{"id":98623990,"identity":"6a16a485-0bde-4df6-8f96-f2b49fff9999","added_by":"auto","created_at":"2025-12-19 17:07:52","extension":"png","order_by":12,"title":"Figure 12","display":"","copyAsset":false,"role":"figure","size":40390,"visible":true,"origin":"","legend":"\u003cp\u003eBuckling Load vs Elongation Curves for Octagon Unit Cell Lattice Specimens (ABS and PLA)\u003c/p\u003e","description":"","filename":"12.png","url":"https://assets-eu.researchsquare.com/files/rs-8345845/v1/ba5459465a76637f5aa8aae1.png"},{"id":98775613,"identity":"f7ed5f41-105a-4577-849d-2419b2ba265e","added_by":"auto","created_at":"2025-12-22 12:20:34","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":4876667,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8345845/v1/979c7320-f7a9-475c-955d-19f69144d22e.pdf"},{"id":98507571,"identity":"3529aed4-c1fd-41aa-8627-e102c1cfb8e4","added_by":"auto","created_at":"2025-12-18 10:58:22","extension":"png","order_by":0,"title":"","display":"","copyAsset":false,"role":"supplement","size":47241,"visible":true,"origin":"","legend":"","description":"","filename":"additionalfigures.png","url":"https://assets-eu.researchsquare.com/files/rs-8345845/v1/d995f6359ea0784ed693b567.png"}],"financialInterests":"No competing interests reported.","formattedTitle":"Experimental Investigation of Tensile and Buckling Behavior of FDM-Fabricated ABS and PLA Lattice Structures with Varying Unit Cell Geometries","fulltext":[{"header":"Highlights","content":"\u003cul\u003e\n \u003cli\u003eLattice structures\u003c/li\u003e\n \u003cli\u003eBuckling behavior of lattice structures\u003c/li\u003e\n \u003cli\u003eTensile behavior of lattice structures\u003c/li\u003e\n \u003cli\u003eUnit cell design\u003c/li\u003e\n \u003cli\u003eStrut thickness\u003c/li\u003e\n \u003cli\u003eMechanical performance of lattice structures\u003c/li\u003e\n \u003cli\u003eComparison of tensile and buckling for strut thickness of lattice structures\u003c/li\u003e\n \u003cli\u003eComparison of tensile and buckling load for ABS and PLA lattice structures\u003c/li\u003e\n \u003cli\u003eComparison of tensile and buckling load of square, hexagon and octagon for lattice structures\u003c/li\u003e\n\u003c/ul\u003e"},{"header":"1. Introduction","content":"\u003cp\u003eLattice structures having porous type forms has aroused huge attention and been used for several fields of aerospace, automotive, medical due to potentials of energy absorption, performance enhancement and efficiency increase. Lattice structures are also preferred in several industries due to their high strength to weight ratio and high energy absorbing ability [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. These structures are in cellular type forms which are difficult and almost impossible to produce by conventional manufacturing methods. Lattice structures of 2.5D (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea) and 3D (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb) are generated in construction by interlinking components of unit cells (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ec) combining beams, trusses, walls and plates. However, despite their advantages, lattice structures are inherently susceptible to buckling due to their slender struts and open-cell geometries. Buckling is a leading cause of structural instability in these systems, particularly under compressive or axial loads, and can result in premature failure, reduced load-bearing capacity, and compromised energy absorption. Therefore, understanding the buckling behavior of lattice structures is crucial in optimizing their design and ensuring safe and reliable performance in practical applications.\u003c/p\u003e \u003cp\u003eLattice structures have found opportunity to be produced from metallic or plastic materials by additive manufacturing (AM) which leads to energy, material and time saving [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Additive manufacturing gives chance to produce the prototypes before mass production and end-use (net shape) products without using too many tools and high amount of waste material [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe main advantage of additive manufacturing is to produce complex geometries which can not be manufactured or can be manufactured difficultly by substractive methods. Due to these advantages, lattice structures which can be possible to produce by AM is used for several industries including aerospace applications. Similar to other engineering structures exposed to compressive loads, buckling causes instability problems which can be source of catastrophic failures for lattice structures due to their thin layered design.\u003c/p\u003e \u003cp\u003eMajority of previous works [\u003cspan additionalcitationids=\"CR6 CR7 CR8 CR9 CR10 CR11 CR12\" citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e] were focused on tensile and compressive behavior of lattice structures. The effects of the printing defects on mechanical properties of additively manufactured were also studied by some authors [\u003cspan additionalcitationids=\"CR15\" citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. There were also several studies [\u003cspan additionalcitationids=\"CR18 CR19 CR20\" citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e] were conducted for investigation of additive manufacturing process parameters. On the other hand, buckling behavior of lattice structures was surprisingly neglected by the researchers.\u003c/p\u003e \u003cp\u003eCerardi et al. [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e] conducted FEA and experimental studies (tensile tests to determine stiffness and tensile strength) for lattice structures of polyamide with different porosity percentage (40%-80%) produced by laser sintering technologies. Ductile behavior was observed for all specimens due to porous form during tensile tests. In the study reported by Chac\u0026oacute;n et al. [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e], PLA specimens manufactured by fused deposition modeling (FDM) in different orientations such as upright, flat and on edge were tested to evaluate the effects of build orientation on strength and stiffness values of 3D printed parts. Higher strength and stiffness values were obtained for flat and on edge orientations compared to upright one by conducting tensile and 3 point bending tests. Previous two orientations show ductile behavior whereas upright one has brittle manner in fracture. This study shows the importance of printing orientations on anisotropic behavior of 3D printed specimens.\u003c/p\u003e \u003cp\u003eLi et al. [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e] carried out a study to investigate mechanical behaviours of aircraft\u0026rsquo;s U shaped bearing ring formed with X, Kagoma, pyramid unit structure additively fabricated from aluminum alloy by numerical and experimental methods. Their comparative study found that 30% mass per unit volume reduction by applying lattice structure design compared to honeycomb structure. The behaviour of stainless steel cellular structures under uniaxial compression load was searched experimentally by Li et al. [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. Local plastic stress-strain around joints of lattice unit cells and self contact of struts during compression tests was observed. Their findings indicated that the unit cell structure is significant for overall stiffness, strength and energy absoption of lattice structures. In the study of Al Rifaie et al.[\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e], compression behavior of 3D printed body center cubic (BCC) and BCC with vertical struts added to all nodes lattices made from ABS were investigated. Higher compressive load carrying capacity was obtained for lattice with vertical struts. Qin et al. [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e] studied the effects of addition inorganic calcium carbonate (CaCO3) and calcium phosphate (TCP) fillers into PLA matrix on the compressive load bearing and energy absorption capacities for additively manufactured cubic and triply periodic minimal surfaces-diamond (TPMS-D) lattices. Below addition of 20% of infillers increases the tensile strength of PLA but more cause to decrease. %10 addition yields in best compressive load carrying capacity and energy absorption.\u003c/p\u003e \u003cp\u003eFew authors [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan additionalcitationids=\"CR24 CR25\" citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e] studied the buckling behaviours of lattice structures. Dong and Fan [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e] made experimental and numerical research to determine buckling load and energy absorption of hexagonal lattice thin tube made from AISI 316 L by loading in X, Y and Z directions. Mean crushing force was determined by numerical work and experiments for several wall thicknesses. Dong et al. [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e] conducted a study to investigate the buckling behavior of meta lattice structure for different center angles of 0 to 120\u0026deg;. Three different printed specimens of PLA were tested for compressive, buckling and crushing behaviors. Energy values for bending and membrane were determined analytically and experimentally with a difference of 12%. Nazir et al. [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e] made experimental and numerical research to evaluate critical buckling load of cubic, inclined cubic, vertical inclined and octet truss lattice columns. Buckling and post buckling were taken into consideration for various lattice structures. They found that inclined structures have higher resistance against instability due to compressive loads. In the study conducted by Babacan and Şeremet [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e], face centered cubic with exterior and interior vertical struts for Co-Cr alloys designed and manufactured using selective laser melting were tested under uniaxial compressive loading. Local buckling and densification were observed during compression tests for lattice structures. Authors stated that 17% higher load carrying capacity under compressive loads was obtained in face centered cubic lattice structure with vertical struts.\u003c/p\u003e \u003cp\u003eLattice structures with their cellular and porous form offer significant advantages such as high strength-to-weight ratio, enhanced energy absorption, and efficient mechanical performance features that are highly desirable in aerospace, automotive and biomedical engineering applications. However, their structural efficiency is often constrained by their less resistance against buckling due to the slender struts and open-cell configurations intrinsic to their design. As stated earlier, buckling is a leading cause of instability in lattice structures, making its characteristics crucial for understanding and ensuring their structural integrity. With the advancement of additive manufacturing technologies, the fabrication of such complex geometries has become increasingly feasible, emphasizing the need for a thorough understanding of their buckling behavior to ensure reliability in practical applications.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eIn this regard, optimizing design parameters such as unit cell geometry, strut thickness and material type is essential for enhancing structural stability and preventing early onset of buckling under compressive loading.\u003c/p\u003e \u003cp\u003eThis study constitutes the first paper of an extensive research effort aimed at determining key mechanical performance parameters of lattice structures and exploring their suitability in advanced engineering applications. A particular focus was placed on experimentally investigating the buckling behavior of lattice structures manufactured from ABS and PLA having square, hexagonal and octagonal unit cell geometries. Critical buckling loads were determined under axial compression and tests were extended beyond the initial buckling point to evaluate the post-buckling response. These findings establish a fundamental framework for understanding the influence of geometrical configurations and material properties on the buckling resistance of lattice structures, thereby contributing to the development of design strategies that ensure their safe and reliable performance in load-bearing applications.\u003c/p\u003e \u003cp\u003eIn the first part of this study, tensile tests were carried out on lattice structures composed of square, hexagonal and octagonal unit cell geometries manufactured from ABS and PLA materials to investigate the effects of cell geometry and material type on tensile performance. In the second part, experimental buckling tests were conducted on the same lattice configurations under axial compressive loading to evaluate their critical buckling loads and post-buckling behavior. The results obtained from both mechanical tests aim to provide a comprehensive understanding of the structural response of lattice structures and serve as a foundation for future design and application.\u003c/p\u003e"},{"header":"2. Materials and Methods","content":"\u003cp\u003eIn this study, lattice structures were designed with three different unit cell geometries: square, hexagonal and octagonal (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea). The lattice specimens were constructed by repeating and interlinking unit cells consisting of struts arranged in regular patterns. Two thermoplastic materials commonly used in additive manufacturing were selected for the fabrication process: ABS and PLA (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb and \u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ec). These materials were chosen due to their distinct mechanical characteristics and widespread application in lightweight structural components. The lattice specimens were produced using a fused deposition modeling (FDM) 3D printer. For each geometry and material combination, two different strut thicknesses (0.5 mm and 1.0 mm) were implemented to investigate the influence of relative density on mechanical behavior. The printing parameters were kept constant throughout the production process to minimize variability: nozzle temperature of 220\u0026deg;C for PLA and 240\u0026deg;C for ABS, and bed temperature of 60\u0026deg;C. After fabrication, the specimens were visually inspected to ensure dimensional consistency and to check for defects such as delamination or voids. Mechanical behavior of the lattice structures was evaluated through both tensile and buckling tests, carried out in a sequential experiments. Initially, uniaxial tensile tests were conducted to determine the tensile strength, elongation and stiffness of the different lattice configurations. All tests were performed at room temperature using a universal testing machine (Shimadzu AGS-X 50 kN). The crosshead displacement rate was set to 2 mm/min and displacement data were recorded continuously until final failure. To ensure reliability and repeatability of the results, a minimum of three specimens were tested for each configuration. Following the tensile testing, buckling experiments were conducted under axial compressive loading to evaluate the critical buckling load and post-buckling behavior of the specimens. The same testing machine was utilized by fitting with compression platens to ensure uniform load application. A constant displacement rate of 1.0 mm/min was applied until substantial lateral deformation or structural collapse occurred.\u003c/p\u003e"},{"header":"3. Results and Discussion","content":"\u003cp\u003eThe primary objective of this study is to experimentally investigate the tensile and buckling behavior of beams incorporating 2.5D lattice structures fabricated via additive manufacturing. In this context, detailed results from both tensile and axial compression tests are presented and discussed in detail. The tensile performance and buckling behavior of lattice structures were evaluated for different unit cell geometries of square, hexagonal and octagonal produced using ABS and PLA materials. For each geometry-material combination, specimens with two different strut thicknesses (0.5 mm and 1.0 mm) were tested to assess the influence of unit cell configuration and relative density on critical buckling load, ultimate tensile strength, stiffness and elongation.\u003c/p\u003e\n\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\n\u003ch2\u003e\u003cstrong\u003e3.1 Tensile Test Results\u003c/strong\u003e\u003c/h2\u003e\n\u003cp\u003eTensile test specimens (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003ea) along with lattice structures composed of square, hexagonal and octagonal unit cells having two distinct strut thicknesses (0.5 mm and 1.0 mm) were designed in compliance with ISO 527-4:2023(E) and fabricated using the Fused Deposition Modeling (FDM) technique. Both ABS (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003eb) and PLA (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003ec) materials were used for additive manufacturing to evaluate the mechanical properties of the lattice structures. Tensile tests were performed using a Shimadzu AGS-X universal testing machine with a 50 kN load capacity at a constant crosshead speed of 2 mm/min by following procedures similar to those reported in previous studies [\u003cspan class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e13\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e25\u003c/span\u003e].\u003c/p\u003e\n\u003cp\u003eTensile load versus elongation curves for lattice test specimens with unit cells fabricated from ABS and PLA are shown in Figs.\u0026nbsp;3a\u0026ndash;3b (square), 3c\u0026ndash;3d (hexagon) and 3e\u0026ndash;3f (octagon). For ABS square lattice specimens (Fig.\u0026nbsp;3a), the ultimate tensile load increased from 383.65 N to 593.07 N as the strut thickness was increased from 0.5 mm to 1.0 mm. This trend is consistent with the findings reported by Torrado and Roberson [\u003cspan class=\"CitationRef\"\u003e28\u003c/span\u003e], highlighting the importance of optimized geometry in enhancing the tensile properties of FDM-printed ABS structures.\u003c/p\u003e\n\u003cp\u003eSquare-based unit cells are particularly known by their moderate stiffness and strength compared to other lattice geometries. A similar trend was observed in PLA specimens (Fig.\u0026nbsp;3b), where the load bearing capacity increased from 673.29 N to 1124.16 N as the strut dimension increased from 0.5 mm to 1.0 mm. This significant enhancement in mechanical performance is attributed to the increased cross-sectional area, structural stiffness, load bearing capacity and load distribution capabilities under tensile loading. PLA exhibited a substantially higher maximum tensile load (673.29 N) compared to ABS (383.65 N), showing a 75.5% improvement in load-bearing capacity for 0.5 mm strut thickness. Similarly, PLA again outperformed ABS with a maximum tensile load of 1124.16 N versus 593.07 N, corresponding to an 89.5% increase for 1.0 mm strut thickness (Fig.\u0026nbsp;4). These findings confirm that PLA provides superior tensile performance relative to ABS for square lattice structures regardless of the strut dimension. As expected, the maximum tensile load increases by depending on strut dimension increase regardless of material type. The difference between maximum tensile load values of ABS and PLA was observed for both strut dimensions (0.5 mm and 1.0 mm). PLA lattice beams exhibited higher maximum tensile loads and greater elongation values compared to ABS at both strut dimensions. PLA has inherently superior mechanical characteristics in the lattice geometries due to its higher rigidity and better layer adhesion in FDM printing.\u003c/p\u003e\n\u003cp\u003eAlthough PLA is known to exhibit brittle behavior, the results indicate that its stiffness advantage plays a dominant role in load-bearing performance for the lattice structures. As seen in Figs.\u0026nbsp;3a and 3b, both ABS and PLA specimens exhibit a sudden drop in load following the ultimate strength point, a characteristic response associated with brittle fracture mechanisms. Compared to ABS, PLA exhibits higher toughness as an evidence of its greater load-bearing capacity and elongation before failure.\u003c/p\u003e\n\u003cp\u003eTensile load versus elongation curves were presented for hexagonal lattice structures with two strut dimensions of 0.5 mm and 1.0 mm produced for ABS and PLA respectively in Fig.\u0026nbsp;3c and 3d. Hexagonal lattices offer a distinct mechanical response due to their stretch-dominated architecture which influences both stiffness and failure modes compared to square lattice. For the ABS hexagonal lattice structure, the increase in strut thickness from 0.5 mm to 1.0 mm resulted in a substantial improvement in tensile performance. The specimen with 0.5 mm struts exhibited a maximum tensile load of 248.05 N, whereas the 1.0 mm counterpart reached 747.22 N. Depending on strut thickness increase, corresponding increase in ultimate load is 200% approximately. This improvement can be regarded to the greater cross-sectional area and the improved structural stability provided by the thicker struts. For PLA, the maximum tensile load increased from 368.67 N (0.5 mm) to 1245.10 N (1.0 mm) with an increase of 237.73% (Fig.\u0026nbsp;4b). Compared to ABS specimens, PLA hexagonal lattices (0.5 mm) exhibited significantly higher tensile load. The energy absorption in hexagonal lattice allow PLA to reach higher tensile limits before brittle fracture initiates. Furthermore, this structure reduces stress concentrations typically associated with crack initiation in brittle polymers. In accordance with literature, stretch-dominated structures such as hexagon lattice tend to exhibit more efficient load transfer across the structure especially when fabricated with sufficient strut thickness. Hexagonal lattices provide improved toughness under tensile loading due to their inherent geometric redundancy compared to square lattice [\u003cspan class=\"CitationRef\"\u003e29\u003c/span\u003e].\u003c/p\u003e\n\u003cp\u003eFigure 3e and 3f show the tensile load\u0026ndash;elongation response of 3D-printed octagonal lattice structures using ABS (Fig.\u0026nbsp;3e) and PLA (Fig.\u0026nbsp;3f) with two strut thicknesses: 0.5 mm and 1.0 mm. For ABS specimens, the increase in strut thickness from 0.5 mm to 1.0 mm led to a significant improvement in load bearing capacity. The specimen with 0.5 mm struts reached a maximum load of 395.81 N, whereas the 1.0 mm counterpart achieved 636.86 N corresponding to 60.9% increase in ultimate tensile load. PLA octagonal lattices demonstrated similar enhancements observed for ABS lattices. The peak tensile load rose from 587.78 N (0.5 mm) to 1076.52 N (1.0 mm), representing an 83.15% increase in load-bearing capacity. The enhanced performance with increased strut thickness is consistent with the role of relative density (the ratio of the density of the lattice structure to that of the base material) and the contribution of strut cross-sectional area to improved load transfer and structural stiffness in lattice structures. Additionally, the octagonal geometry offers a hybrid mechanical behavior between bending-dominated and stretch-dominated structures with notable trends in both materials depending on strut thickness. Particularly, compared to square cells, the octagonal unit cell design provides more complex load paths resulting gradual failure behavior and improved energy dissipation capacity, especially when struts are sufficiently thick to avoid local buckling.\u003c/p\u003e\n\u003cdiv class=\"BlockQuote\"\u003e\u0026nbsp;\u003c/div\u003e\n\u003cp\u003eAcross all configurations, PLA exhibited higher ultimate tensile loads than ABS, which can be due to its greater stiffness and higher Young\u0026rsquo;s modulus under quasi-static loading (Fig.\u0026nbsp;4). When comparing geometries within the same material, octagonal lattices outperformed square lattices but were slightly less effective than hexagonal lattices in terms of ultimate tensile load. This observation supports the classification of octagonal structures show hybrid mechanical behavior between bending-dominated and stretch-dominated structures. According to a reference work [\u003cspan class=\"CitationRef\"\u003e29\u003c/span\u003e], these types of geometries exhibit intermediate mechanical responses by combining the ductility of bending-dominated designs (like squares) and the strength of stretch-dominated designs (like hexagons).\u003c/p\u003e\n\u003cp\u003eFigure 4 shows the combined effect of material type, unit cell geometry, and strut thickness on the ultimate tensile performance of lattice structures. Across all geometries and materials, increasing the strut thickness from 0.5 mm to 1.0 mm resulted in a significant increase in maximum tensile load. This trend is consistent with previous findings [\u003cspan class=\"CitationRef\"\u003e29\u003c/span\u003e], where enhanced cross-sectional area directly contributes to increased load-bearing capacity due to reduced stress concentrations and improved stiffness.\u003c/p\u003e\n\u003cdiv class=\"BlockQuote\"\u003e\u0026nbsp;\u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\n\u003ch2\u003e3.2 Buckling Test Results\u003c/h2\u003e\n\u003cp\u003eSimilar to tensile test specimens, each group of buckling test specimens include three different lattice structures of square, hexagon and octagon having strut thickness values of 0.5 mm and 1.0 mm were prepared as shown in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e5\u003c/span\u003e. Buckling tests were conducted for beams under fixed-fixed end condition by using Shimadzu AGS-X 50 kN. In this study, the specimens with a strut thickness of 0.5 mm are designated as S1, S2, and S3, while those with a strut thickness of 1.0 mm are referred to as S7, S8 and S9. The progressive damage mechanisms of the first square unit cell lattice specimens with a 0.5 mm strut thickness for both ABS and PLA which were subjected to buckling tests are illustrated step by step in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003e. Figure\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003ea represents the specimen S1 (ABS) before loading. Initial buckling was observed in one of the unit cells of the lattice structure marking the onset of structural instability (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003eb). As the compressive load increased, the unit cell began to fold (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003ec), and this deformation gradually progressed throughout the structure (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003ed). The folding process was completed resulting in significant structural distortion as illustrated in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003ee. By further loading, the collapse of the folded unit cells led to the formation of cracks indicating the start of material failure (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003ef and \u003cspan class=\"InternalRef\"\u003e6\u003c/span\u003eg).\u003c/p\u003e\n\u003cp\u003eAlthough the estimation of maximum (critical) load at buckling initiation is sufficient for the scope of this research, the compressive load was further increased to observe post buckling behavior of lattice structure under compressive load up to the complete structural failure. Specimens S7, S8 and S9 (with 1.0 mm strut thickness) are shown in their pre-test condition in Figs.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003ea.1, 7a.3, and 7a.7 respectively. The onset of buckling is illustrated in Figs.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003ea.4 and 7a.8, while the subsequent folding of unit cells is depicted in Figs.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003ea.2, 7a.6, 7a.9 and 7a.10.\u003c/p\u003e\n\u003cp\u003eThe buckling tests for PLA square unit cell lattice specimens commenced with sample S1 as shown in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003eb. Initial buckling within the lattice structure was observed indicating the onset of instability (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003eb.2). As the compressive load increased, progressive folding of the unit cells occurred as illustrated in Figs.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003eb.3 and 7b.4. Similar deformation patterns and damage progression were observed for specimens S2 and S3. For specimen of S2, folding and structural distortion are presented in Figs.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003eb.5, 7b.6 and 7b.7, while the sequence of buckling and folding stages for S3 is depicted in Figs.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003eb.8 through 7b.10. The buckling behavior of specimens S7, S8 and S9 (PLA) is illustrated in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003ec. The initiation of buckling in the unit cell structures was identified for specimens S7, S8 and S9 in Figs.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003ec.1-7c.3, 7c.5\u0026ndash;7c.6, and 7c.8 respectively. Following the initial buckling, progressive folding of the unit cells was observed, as shown in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003ec.4 for S7, Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003ec.7 for S8, and Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003ec.10 for S9.\u003c/p\u003e\n\u003cp\u003eThe buckling load\u0026ndash;deformation curves for square unit cell lattice specimens with strut thicknesses of 0.5 mm and 1.0 mm for ABS and PLA were obtained and are presented in Figs.\u0026nbsp;8a and 8b respectively. Understandably, increasing the strut thickness from 0.5 mm to 1.0 mm in ABS specimens leads to enhanced structural stability under buckling. The 0.5 mm of ABS specimens exhibit pronounced lateral deformation and early onset of localized buckling. In contrast, 1.0 mm strut thickness ABS specimens (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003ea) display a more uniform load-bearing response with delayed and less severe buckling features. This observation is in strong agreement with the findings of Choy et al. [\u003cspan class=\"CitationRef\"\u003e30\u003c/span\u003e], who demonstrated that increasing the strut diameter in lattice structures significantly enhanced compressive stiffness and shifted the failure mode from abrupt shear collapse to a more gradual and layer-wise deformation. These results suggest that the beneficial effects of increased strut thickness on structural stability are not only pronounced in metallic lattices but are also valid for polymer-based lattice structures fabricated by additive manufacturing methods such as Fused Deposition Modeling (FDM). Similar to ABS, PLA lattice structures with 1.0 mm struts exhibit superior buckling resistance compared to their 0.5 mm strut thickness as observed in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003eb and \u003cspan class=\"InternalRef\"\u003e7\u003c/span\u003ec. Additionally, a comparison between the ABS and PLA suggests that PLA specimens generally maintain their structural integrity better than ABS particularly at higher strut thicknesses. The buckling load versus deformation results for square unit cell lattice structures reveal a clear influence of both material type and strut thickness on structural stability under compressive loading (Fig.\u0026nbsp;8). ABS and PLA specimens having strut thickness of 0.5 mm demonstrated critical loads of 200.70 N and 408.85 N respectively. This indicates that PLA exhibits slightly higher buckling resistance than ABS at smaller strut dimensions due to its moderate stiffness and energy absorption characteristics.\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eInterestingly, while the critical buckling load for ABS remained nearly unchanged at 408.85 N when the strut thickness increased to 1.0 mm, PLA showed a substantial enhancement in performance. The PLA specimen with 1.0 mm struts achieved a significantly higher buckling load of 695.78 N, representing a 70% increase compared to its 0.5 mm counterpart. This result suggests that PLA benefits more notably from increased structural rigidity when the cross-sectional area is enlarged. The findings highlight that PLA outperforms ABS at higher strut thicknesses in terms of buckling resistance for square lattice geometries, likely due to its higher elastic modulus and improved layer adhesion during the additive manufacturing process. Figures\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e9\u003c/span\u003e illustrates the buckling behavior of hexagonal unit cell lattice structures for ABS and PLA materials having strut thicknesses of 0.5 mm and 1.0 mm. The thinner ABS specimens (0.5 mm) were firstly buckled under compressive load (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e9\u003c/span\u003ea.1, 9a.3 and 9a.5) and then folding of buckled unit cell emerged as square one (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e9\u003c/span\u003ea.2, 9a.4 and 9a.6). In addition, specimens with strut thickness of 1.0 mm (S7-S8-S9) were tested; buckling started (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e9\u003c/span\u003eb.1, 9b.3 and 9b.5) and progressed (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e9\u003c/span\u003eb.2, 9b.4 and 9b.6). The 0.5 mm strut thickness specimens exhibit obvious lateral deflections and buckling modes at relatively low compressive loads. This behavior is particularly evident in both ABS and PLA indicating that thinner struts lack sufficient rigidity to sustain higher loads without premature instability (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e9\u003c/span\u003ea). In contrast, the 1.0 mm thick specimens (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e9\u003c/span\u003eb) demonstrate a significantly delayed onset of buckling characterized by less severe lateral displacement. This is consistent with the increased moment of inertia and axial stiffness imparted by the thicker struts, which shows improved buckling resistance in lattice structures with increased strut diameter. Buckling load curves are presented for hexagon unit cell specimens of ABS and PLA with 0.5 mm thickness (S1-S2-S3) and 1.0 mm (S7-S8-S9) in Fig.\u0026nbsp;10. The mechanical response curves given in Fig.\u0026nbsp;10 further substantiate visual observations for steps of buckling occurance seen in Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e9\u003c/span\u003ea and \u003cspan class=\"InternalRef\"\u003e9\u003c/span\u003eb. Buckling behavior for both materials across thickness variations are seen in Fig.\u0026nbsp;10. For ABS, the 0.5 mm specimens reached the critical buckling load of approximately 110 N, while the 1.0 mm struts had around 270 N. In the case of PLA, thicker struts had the critical buckling load of approximately 600 N which is significantly higher than their thinner specimens having only about 200 N. As expected from analytical axial buckling formulations, increasing thickness improves critical buckling load in elastic buckling significantly for polymer lattice structures. Results show that increasing strut thickness from 0.5 to 1.0 mm nearly doubled the buckling load for ABS and tripled it for PLA. Notably, PLA consistently outperformed ABS, which correlates with its higher modulus and strength in FDM printed structures. The relatively higher buckling capacity of PLA is attributable to its greater stiffness and tensile strength compared to ABS, as also highlighted in prior studies [\u003cspan class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e31\u003c/span\u003e]. After hexagon unit cell collapse, lattice structure continues to carry load under the effect of the post buckling for 1.0 mm thick specimens. This increase is not very effective for thinner specimens compared to thicker ones due to fracture of unit cell during folding and disengagement of cell wall from the unit cell. Overall, the results clearly demonstrate that both material selection and strut thickness critically influence the buckling performance of hexagonal lattice structures. Increasing the strut diameter not only enhances load-bearing capacity but also postpones the onset of instability, contributing to improved structural reliability. These observations are in agreement with the established Euler buckling theory and recent experimental work on architected lattice metamaterials. Gibson \u0026amp; Ashby\u0026rsquo;s model predicts buckling strength dependency on relative density and strut slenderness, which our results support [\u003cspan class=\"CitationRef\"\u003e29\u003c/span\u003e]. V\u0026ouml;llmecke et al. [\u003cspan class=\"CitationRef\"\u003e32\u003c/span\u003e] showed hexagonal lattices primarily fail via vertical-ligament elastic buckling, which matches our observed buckling morphology. Joseph et al. [\u003cspan class=\"CitationRef\"\u003e33\u003c/span\u003e] demonstrated that both process parameters and base material (ABS/PLA) significantly influence compressive stiffness and buckling. In addition to square and hexagon, octagon lattice specimens having 0.5 mm and 1.0 mm strut thickness for both ABS and PLA were also tested under compressive load to determine buckling behaviour (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e11\u003c/span\u003ea and \u003cspan class=\"InternalRef\"\u003e11\u003c/span\u003eb). Each series (S1\u0026ndash;S3 for 0.5 mm, S7\u0026ndash;S9 for 1.0 mm) demonstrates a clear progression in structural stability depending on material and strut thickness. Similar to hexagonal lattices, the deformation behavior under axial compression is strongly dependent on both geometry and material type. Figure\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e11\u003c/span\u003ea.1-11a.6 show that ABS specimens with 0.5 mm struts experience substantial lateral deformation and buckling as in case of the typical of slender structures with low bending stiffness. PLA specimens (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e11\u003c/span\u003ea.7\u0026ndash;12) show relatively linear profiles in the pre-buckling stage and collapse more abruptly in later stages likely due to PLA lattice specimens\u0026rsquo; higher stiffness but lower ductility. Specimens with thicker struts (1.0 mm) exhibit higher resistance to buckling (Fig.\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e11\u003c/span\u003eb). Their failure occurs at greater loads and the PLA specimens show more brittle and sudden failure in agreement with findings in Dawoud et al. and Tymrak et al. [\u003cspan class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan class=\"CitationRef\"\u003e31\u003c/span\u003e], where PLA outperforms ABS in stiffness but not in deformation capacity.\u003c/p\u003e\n\u003cp\u003eThe visual post-buckling modes are consistent with studies on cellular solids, where increased strut thickness shifts the buckling mechanism from elastic instability to material yielding or fracture [\u003cspan class=\"CitationRef\"\u003e29\u003c/span\u003e]. This qualitative interpretation is further supported by the quantitative results presented in Fig.\u0026nbsp;12. ABS octagonal lattices with 0.5 mm strut thickness reached a critical buckling load of around 110 N, while increasing the strut thickness to 1.0 mm raised the critical buckling load to 260 N approximately before exhibiting a gradual decline in the post-buckling region. Compared to ABS specimens, PLA octagonal lattices demonstrated significantly higher critical buckling loads of 220 N and 700 N for 0.5 mm and 1.0 mm strut thickness respectively. This substantial increase is attributed to PLA\u0026rsquo;s higher stiffness and elastic modulus.\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003c/div\u003e"},{"header":"4. Conclusion and Discussion","content":"\u003cp\u003eThis experimental investigation comprehensively characterized the mechanical performance of lattice structures fabricated via FDM with emphasis on the effects of unit cell geometry (square, hexagonal, octagonal), material type (ABS and PLA), and strut thickness (0.5 mm and 1.0 mm) under both tensile and compressive (buckling) loading conditions. The key findings of this study demonstrate that increasing the strut thickness from 0.5 mm to 1.0 mm resulted in substantial improvements in the ultimate tensile load across all lattice geometries and materials. PLA specimens consistently exhibited higher tensile strength with the most pronounced enhancements observed in hexagonal lattices compared to ABS. This superior performance is attributed to the stretch-dominated architecture of the hexagonal lattice which facilitates efficient load transfer and energy dissipation. The buckling load capacity of the lattice structures exhibited strong dependence on both material characteristics and strut thickness. Increasing the strut thickness effectively delayed the onset of buckling and minimized post-buckling deformations leading to improved structural stability. PLA outperformed ABS in buckling performance particularly at higher strut thicknesses, due to its higher elastic modulus and improved interlayer bonding resulting from the FDM process.\u003c/p\u003e \u003cp\u003eAmong the investigated lattice types, hexagonal unit cells showed the highest mechanical efficiency under both tensile and compressive loading conditions owing to their stretch-dominated deformation behavior. Octagonal structures exhibited intermediate characteristics between bending and stretch-dominated responses, whereas square lattices governed primarily by bending deformation and demonstrated comparatively lower mechanical performance.\u003c/p\u003e \u003cp\u003eDespite its inherently brittle nature, PLA displayed greater structural stability and outperformed ABS in both tensile and buckling tests. This behavior is in alignment with buckling theory and is supported by recent studies on lattice and cellular structures.\u003c/p\u003e \u003cp\u003eIn conclusion, this study highlights the critical role of unit cell geometry, material selection and strut thickness in defining the mechanical performance and structural integrity of additively manufactured lattice structures. The results form a framework for the design and optimization of such structures in engineering applications where high tensile strength and buckling resistance are essential. These insights are expected to guide future research in the development of predictive models and the design of high-performance lattice structures for lightweight and load-bearing applications.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e \u003ch2\u003eDeclaration of Competing Interest\u003c/h2\u003e \u003cp\u003eThe authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.\u003c/p\u003e \u003c/p\u003e\u003ch2\u003eFunding information\u003c/h2\u003e \u003cp\u003eThis research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eThe author was responsible for the conceptualization of the study, experimental design, specimen fabrication, data acquisition, data analysis and interpretation, as well as manuscript preparation and revision. The author approved the final manuscript.\u003c/p\u003e\u003ch2\u003eData availability\u003c/h2\u003e \u003cp\u003eData will be made available on request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eVoicu AD, Hadăr A, Vlăsceanu D (2021) Benefits of 3D printing technologies for aerospace lattice structures. Sci Bulletin'Mircea cel Batran'Naval Acad, 24(1)\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eNazir A, Arshad AB, Jeng J-Y (2019) Buckling and post-buckling behavior of uniform and variable-density lattice columns fabricated using additive manufacturing. Materials 12(21):3539\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMaconachie T et al (2019) SLM lattice structures: Properties, performance, applications and challenges. 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Compos Adv Mater 30:26349833211003904\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJoseph A, Mahesh V, Mahesh V (2023) Effect of loading rates on the in-plane compressive properties of additively manufactured ABS and PLA-based hexagonal honeycomb structures. J Thermoplast Compos Mater 36(3):1113\u0026ndash;1134\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Lattice structure, buckling, tensile loading, additive manufacturing, ABS, PLA","lastPublishedDoi":"10.21203/rs.3.rs-8345845/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8345845/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eLattice structures produced via additive manufacturing (AM) have attracted substantial interest in aerospace, biomedical and automotive industries due to their superior strength-to-weight ratio and energy absorption ability. However, these cellular structures are inherently prone to buckling under compressive loading because of their open-cell geometries and slender struts. Buckling not only initiates premature structural failure but also severely limits the load-bearing capability and reliability of such structures in critical applications. While previous research has extensively explored tensile and compressive behavior, systematic and comparative investigation into the buckling performance of polymer based AM lattices remains scarce. This study addresses this gap by experimentally evaluating both tensile and buckling responses of lattice structures fabricated from ABS (Acrylonitrile Butadiene Styrene) and PLA (Polylactic Acid) using Fused Deposition Modeling (FDM). Three different unit cell geometries of square, hexagonal and octagonal with two strut thicknesses (0.5 mm and 1.0 mm) were investigated to understand the combined effects of lattice structure, material and strut thickness. The results reveal that both tensile strength and buckling resistance are significantly influenced by strut thickness and material type. PLA demonstrated superior performance over ABS particularly in terms of critical buckling loads with the most pronounced improvements observed in hexagonal lattices due to their stretch-dominated structure. These findings underscore the critical role of buckling in determining the structural integrity of AM lattice designs and offer essential insights for optimizing geometry and material selection to enhance stability and reliability in load-bearing applications.\u003c/p\u003e","manuscriptTitle":"Experimental Investigation of Tensile and Buckling Behavior of FDM-Fabricated ABS and PLA Lattice Structures with Varying Unit Cell Geometries","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-12-18 10:58:11","doi":"10.21203/rs.3.rs-8345845/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"445eec4d-9319-42f3-a954-066589e10708","owner":[],"postedDate":"December 18th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-12-19T02:08:58+00:00","versionOfRecord":[],"versionCreatedAt":"2025-12-18 10:58:11","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8345845","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8345845","identity":"rs-8345845","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}