Optimizing In-Situ Adhesive Bonding for Multi-Material Additive Manufacturing: Mechanistic Comparison of Solvent-Assisted and Thermal Methods for ABS-PLA Joints

Optimizing In-Situ Adhesive Bonding for Multi-Material Additive Manufacturing: Mechanistic Comparison of Solvent-Assisted and Thermal Methods for ABS-PLA Joints | 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 Optimizing In-Situ Adhesive Bonding for Multi-Material Additive Manufacturing: Mechanistic Comparison of Solvent-Assisted and Thermal Methods for ABS-PLA Joints Mohammad Hadi Zahmatkeshan, Farid Reza Biglari, Bijan Mollaei Dariani This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8130352/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 The robust joining of dissimilar polymers, such as acrylonitrile butadiene styrene (ABS) with polylactic acid (PLA) is essential to promote multi-material additive manufacturing (AM). This work systematically compares acetone assisted solvent bonding at 25 and 75°C to direct thermal bonding at 100–160°C for ABS-PLA lap-shear joints, by use of ABS as an in-situ adhesive and according to ISO 4587, as standard. The optimal thermal bonding temperature was 140°C as it yielded the highest shear strength of 2.2.96 ± 0.02 MPa, which was a 92% improvement compared to acetone bond temperature of 25°C (1.54 ± 0.02 MPa) and one-way ANOVA showed that there are trends that differ significantly between conditions (p < 0.001).There was a mechanistic shift between the brittle adhesive failure in solvent-bonded joints to the ductile cohesive failure in thermally-bonded joints by temperature-enhanced molecular interdiffusion (zone widths up to 0.475 mm at 160°C). The use of scanning electron microscopy proved the occurrence of filament tear, plastic deformation and degradation in the specimens after heating (e.g., void density was about 23.6% at 160 C), whereas finite element analysis provided confirmation of stress distributions and mechanisms of failure. Such results offer the basis to optimize joining parameters towards reliable, repairable and sustainable multi-material AM structure via efficient, high-performance approach. Multi-Material Additive Manufacturing ABS-PLA Bonding Lap-Shear Strength ISO 4587 Thermal Bonding Polymer Interdiffusion Finite Element Analysis Cohesive Failure Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 1. Introduction Multi-material additive manufacturing (AM), with a focus on fused deposition modeling (FDM), can be used to produce functionally graded parts where multiple polymers with different properties are combined to make parts with complementary properties [ 1 , 2 ]. An example of such synergy is PLA and ABS: PLA has high stiffness and is biodegradable and easy to process, whereas ABS is impact resistant, ductile, with higher glass transition temperature(T_g ≈ 105°C) [ 3 , 4 ]. These hybrids can be used for applications such as custom prosthetics, lightweight automobile parts, and electronics [ 5 ]. Nonetheless, thermodynamic and chemical incompatibilities, such as the non-polar nature of the ABS and the polar ester groups in the PLA, lead to the poor strength of the ABS-PLA interfaces and limitation in diffusion of the molecules [ 6 ]. Different thermal properties (T_g,PLA ≈ 60°C vs. T_g,ABS ≈ 105°C) also results in residual stresses and delamination on cooling stage [ 7 ]. Solvent bonding, using agents like acetone, dissolves surfaces to promote entanglement but is limited for dissimilar pairs due to selective solubility. Acetone effectively targets ABS but minimally affects PLA, resulting in asymmetric and weak interfaces [ 8 , 9 ]. Thermal bonding applies heat and pressure to enable chain reptation and interdiffusion above Tg, according to reptation theory [ 10 ], but precise care is needed to avoid "cold" welds or degradation [ 11 ]. There is a lack of systematic comparisons of the methods for ABS-PLA, often focusing on single techniques or in-print adhesion rather than post fabrication joining [ 12 , 13 ]. Few studies integrate mechanical testing with microstructural and computational analyses to unfold failure mechanisms, and benchmarking using standards such as ISO 4587 is rare, specifically for sustainability aspects such as reparability [ 14 , 15 ]. Previous publications report shear strengths less than 2 MPa, without any optimization towards ductility or degradation threshold [ 16 ]. This study bridges these gaps by performing a comparison between chemical bonding (25°C and 75°C) and thermal bonding (100 to 160°C) of ABS-PLA lapshear joints, in accordance with ISO 4587.Using mechanical testing, SEM fractography, and FEA, we show a transition from adhesive to cohesive failure, with peak shear strengths of 3.31 ± 0.02 MPa at 160°C and an optimal 2.96 ± 0.02 MPa at 140°C, representing a 92% increase, nearly doubling the performance of acetone bonding at 25°C. This mechanistic framework is new in the literature, supporting reliable multi-material AM for sustainable reparability and recycling [ 17 ]. 2. Materials and Methods 2.1 Materials The materials used in this research were commercial filaments of white polylactic acid (PLA) and black acrylonitrile butadiene styrene (ABS), namely, eSUN PLA + and eSUN ABS + grades, with a 1.75 mm nominal diameter, which were selected due to their contrasting colors to clearly observe fracture interface examination during post-testing characterization [ 4 ]. The acetone-assisted bonding was conducted using high-purity acetone (≥ 99.5%) because it has been shown to perform well in dissolving ABS and allow controlled means for investigation of the selective solubility effects on PLA interfaces. 2.2 Specimen Preparation and Joint Fabrication Tensile lap-shear test specimens were designed and manufactured strictly in accordance with ISO 4587 standard, which offers a standardized method of examining the tensile lap-shear strength of rigid-to-rigid bonded assemblies [ 14 ]. The printed adherends were manufactured through a fused deposition modeling (FDM) printer, namely the Creality Ender 3 Pro model, to achieve uniform quality and quasi-isotropic mechanical properties necessary to make reliable mechanical comparisons. Printing parameters were optimized and kept consistent between speciemens, including; a layer height of 0.2 mm, 100% infill density, to minimize anisotropy effects[ 26 ], nozzle and bed temperatures set to 210°C and 60°C respectively in the case of PLA, nozzle temperature of 240°C in the case of ABS, and a constant print speed of 50 mm/s. These settings were selected due to previous optimization studies in order to maintain a balance between print quality, material flow, and interlayer adhesion, to reduce variability in the baseline adherend properties that are expected to affect the joint performance. The size of the overlap region was meticulously controlled as the ISO 4587 standard, a 12.5 mm width and an overlap length of 25 mm was created (Fig. 1 -a). It should be noted that maintaining experimental consistency in dissimilar polymer systems, where misalignment can significantly amplify interfacial weaknesses [ 11 ]. Two key bonding techniques were evaluated for structured comparison of solvent-based and thermal approaches: solvent aided bonding using acetone and thermal aided bonding using a heat blower. For each type of bonding condition, five specimens (N = 5) were produced as a replicate to provide sufficient statistical power, to detect differences in shear strength, and consider inevitable variability of FDM-printed materials in line with guidelines of experimental design for mechanical testing [ 18 ]. 2.2.1 Acetone-Assisted Bonding ABS-PLA lap-shear joints were prepared using acetone as a solvent-based adhesive at two distinct temperatures to investigate the influence of thermal assistance on solvent efficacy. At ambient temperature (25°C), a controlled volume of 50 µL of acetone was applied evenly to the surface of the ABS adherend in the overlap region, after which the PLA adherend was immediately brought into contact with the wetted ABS surface using the custom jig; a constant pressure of 50 kPa was then applied for 60 seconds to promote initial adhesion,[ 25 ] followed by curing at 25°C for a minimum of 24 hours to allow complete solvent evaporation and bond solidification. Under the higher temperature condition (75°C), the procedure followed the same steps, only that the ABS surface was moistened with acetone but the bonding process was carried out in an oven maintained at 75°C, a temperature strategically controlled beyond the glass transition temperature (T_g of PLA ≈ 60°C), but below that of ABS (≈ 105°C), so as to investigate the effects of softening the PLA without affecting the integrity of ABS [ 27 ]; the 50 kPa pressure with the same duration were applied, with initial solvent evaporation occurring, followed by the standard 24-hour curing at 25°C. 2.2.2 Heat Blower-Assisted Bonding To determine the temperature range for the heat blower-assisted bonding method at which the ABS-PLA lap-shear joints could be formed adequately, a range of four and gradually increasing temperatures was used 100°C, 120°C, 140°C, and 160°C to see the thermal optimal molecular interdiffusion and monitor whether any degradation can occur. As shown in Fig. 1 -b, a Steinel HG 2320 E heat blower was applied with a precision nozzle to apply localized heat directly to the overlap area but not excessive heat to the surrounding, thus ensuring controlled application of energy to the overlap region. The temperature at the joint interface was real-time measured and controlled using Fluke 62max + infrared laser thermometer, which preformed non-contact sensing via dual laser beams, with an accuracy within ± 1.5°C to minimize thermal gradients and enable fine tune temperature control, addressing limitations in previous studies of thermal bonding that introduce variable results and low strengths due to inconsistent heating temperatures [ 19 ]. As soon as the desired temperature was attained and stabilized for 30 seconds, the constant pressure of 50 kPa was applied via the custom jig, and the joint was allowed to cool naturally to ambient temperature. The exact duration of heat application and pressure applied was calibrated through trial runs to have the optimum interdiffusion without the risk of the materials deforming or a significant thermal degradation, especially at higher temperatures nearing the melting point of PLA (≈ 190°C). 2.3 Mechanical Testing The tensile lapshear tests used to evaluate mechanical performance of the bonded joints, carried out in accordance with ISO 4587 standard to ensure comparability with international benchmarks [ 14 ]. The tests were conducted on the universal testing machine (SANTAM STM-20 in Fig. 1 -c) with a 20 kN load cell. Tests were conducted at a fixed rate of head displacement of 5 mm/min until complete specimen failure with continuously recorded load-displacement data to record full stress-strain response. Based on these data, the ultimate shear stress ( \(\:{\tau\:}_{ult}\) ) was calculated by dividing the maximum load ( \(\:{F}_{max}\) ) by the nominal overlap area ( \(\:{A}_{overlap}\) ), using the formula [ 29 ]: $$\:{\tau\:}_{ult}=\frac{{F}_{max}}{{A}_{overlap}}$$ Plots of stress versus strain were generated thereafter to provide detailed insights into the elastic modulus, yield behavior, and plastic deformation characteristics of the joints under shear loading. Table 1 Dimensions and parameters for the adhesive joint test specimen according to ISO 4587. Parameter Symbol Value (mm) Specimen width 1 25 ± 0.25 Bonded area length 2 12.5 ± 0.25 Length gripped in jaws 3 37.5 Length of each arm 4 100 ± 0.25 2.4 Microstructural Characterization After mechanical testing, microstructural characterization was performed on the intact (pre-test) and fractured (post-test) specimens to understand the mechanism of failure, such as adhesive failure at the interface, cohesive failure within the ABS or PLA bulk or mixed-mode. This analysis evaluated surface morphology for evidence of filament tearing, plastic deformation, or thermal effects, and allowed the correlations with shear strength and stress-strain behavior. Each bonding condition was represented by 4 specimens (acetone-assisted at 25°C; thermal at 120°C, 140°C, and 160°C).with 3 for pre-test imaging to assess initial bond formation and 2 for post-test imaging to evaluate failure evolution. Specimens were selected as per ISO 4587 compliant mechanical results to exemplify weak (acetone) and strong (optimal thermal) bonds. Specimens were sputter-coated with a thin layer of gold-palladium to help conductivity, and avoid charging artifact [ 20 ]. AIS2300C scanning electron microscope (Amirkabir University) under high vacuum mode with 10–15 kV acceleration voltage, secondary electron (SE) detectors for topography, and backscattered electron (BSE) detectors for compositional contrast. Multiple magnifications were used: 50–100× for overviews; 1000–5000× for details like fibrils or voids. images focused on the overlap region to document features such as fibril formation, interface sharpness, voids and cracks, surface roughness, material transfer, and raster patterns. Images were processed and quantified using Fiji (version 1.53). Fibril length and density for ductile deformation, surface roughness (Ra via profile plots) [ 24 ], width of diffusion zone, and the degree of material transfer using area fraction analysis were among the metrics used. These quantitative results granted the possibility to make direct comparisons between the pre and post-test states and reinforced mechanistic correlations with mechanical data. 2.5 Finite Element Analysis (FEA) Simulation To support the experimental findings with predictive accuracy, finite element modelling was conducted using ABAQUS software (version 2023) [ 22 ]. According to the experimental model, a detailed 3D model of the ISO 4587 lapshear joint was created, which accurately replicated the experimental geometry in every detail, including the overlap region and adherend dimensions. The literature values and additional data from performed tensile tests of bulk printed samples were used to provide the material properties of ABS and PLA for Young's modulus, Poisson's ratio, yield strength, and ultimate tensile strength to support model fidelity [ 4 ]. The ABS and PLA interface was modeled using a cohesive zone element approach and then the tie constraints and surface-to-surface contact with friction were used to model the realistic failure and bonding progression. Boundary conditions modeled on the test setup used with the first end of the joint encastered in all degrees of freedom, and a tensile displacement load applied at a rate of 5 mm/min crosshead speed. Meshing used a locally refined C3D8R brick element in the mesh vulnerable overlap area to capture stress intensities and deformations precisely and a smoother mesh elsewhere in less stressed regions to save computation time. Main aims of the simulations were to visualize distributions of von Mises stresses in the joint, predict initiation and propagation of failure and provide computational validation of the mechanical properties observed experimentally, including stress transfer resulting in cohesive failure in thermally bonded samples. 2.6 Statistical Analysis Finally, statistical analysis was used on the quantitative data in order to assess differences between the bonding conditions. Descriptive statistics, such as means and standard deviations of peak shear stress and strain at failure, were computed for each group. A one-way analysis of variance (ANOVA) was utilized to compare the means of shear strengths of the different bonding conditions, assuming normality and homogeneity of variances, that was checked prior to the analysis using Shapiro- Wilk and Levene tests, respectively [ 18 ]. In case ANOVA showed significant effects, Tukey Honestly Significant Difference ( HSD ) post-hoc testing was performed to determine any specific pairwise differences. Also, Regression analysis was used on the heat blower-assisted bonding records to model linear relationships between bonding temperature and ultimate shear strength, so the effects of temperature and the optimal temperature range were quantified. All analysis was carried out in SPSS software with a significance level set at α = 0.05 [ 23 ]. 3. Results The bonding method and temperature significantly affected mechanical response of ABS-PLA lapshear joints, as indicated in Figure 2 with shear stress-strain curves. Acetone assisted bonding temperatures 25°C and 75°C demonstrated comparatively low peak shear strengths 1.54 ± 0.02 MPa and 2.31 ± 0.02 MPa, respectively, and moderate strains at failure: 3.08 ± 0.02% and 4.71 ± 0.02%.The failure was sudden, and this suggests a brittle interface. Thermal bonding by contrast had a significant increase in shear strength with peak strengths increasing to 3.31 ± 0.02 MPa at 160°C compared to 2.44 ± 0.02 MPa at 100°C . Ductility fluctuated, drop in strain at 100°C, 3.06 ± 0.02%, in comparison to 75°C, suggesting a stiffer interface at this transition temperature. The best balance between strength and ductility was recorded at 120°C and 140°C with shear strengths of 2.61 ± 0.03 MPa and 2.96 ± 0.02 MPa and strains at failure of 3.57 ± 0.04% and 3.61 ± 0.03%, respectively. The highest shear strength, 3.31 ± 0.02 MPa and strain 4.74 ± 0.03% were recorded at a temperature of 160°C. though SEM analysis (as discussed below) indicates the onset of thermal degradation along with this behavior as shown in Figure 4-d. No anomalies or outliers were evident across replicates, also there was a steady increase in values with temperature increase, with a low coefficient of variation (CV <1.2%), demonstrating a high degree of experimental reproducibility. Table 2. Descriptive Statistics for Shear Stress (MPa) and Strain at Failure (%) Across Bonding Conditions (N=5 Replicates per Group). Bonding Method Temp (°C) Mean Stress (MPa) SD Stress (MPa) Min Stress (MPa) Max Stress (MPa) CV Stress (%) Mean Strain (%) SD Strain (%) Min Strain (%) Max Strain (%) CV Strain (%) Acetone 25 1.54 0.02 1.51 1.56 1.24 3.08 0.02 3.05 3.11 0.75 Acetone 75 2.31 0.02 2.29 2.34 0.82 4.71 0.02 4.69 4.75 0.49 Thermal 100 2.44 0.02 2.41 2.46 0.78 3.06 0.02 3.02 3.08 0.75 Thermal 120 2.61 0.03 2.58 2.64 0.96 3.57 0.04 3.52 3.62 1.15 Thermal 140 2.96 0.02 2.93 2.99 0.78 3.61 0.03 3.58 3.65 0.80 Thermal 160 3.314 0.023 3.29 3.35 0.69 4.736 0.025 4.70 4.76 0.53 Table 3 presents the results of the one way ANOVA, which indicate statistically noteworthy differences in all groups for both stress and strain ( p < 0.001). Post hoc analysis (Table 4) confirmed that all thermal bonding conditions were superior to both acetone conditions, as all pairwise comparisons of stress were significant. Regarding strain, Thermal 120°C and 140°C with p=0.999, did not exhibit significant differences in ductility; all other pairs did. Regression analysis of thermal groups (Table 5) also modeled temperature effects, showing a strong linear increase in stress (R² = 0.995, p < 0.001) but having a non-significant, weak trend for strain (R² = 0.629, p = 0.109) Table 3. One-Way ANOVA Results for (a) Shear Stress and (b) Strain at Failure (6 Groups, N=5 per Group, Total N=30). (a): One-Way ANOVA for Shear Stress Source DF Sum of Squares (SS) Mean Square (MS) F-value p-value Between Groups 5 15.852 3.170 3254.92 <0.001 Within Groups 24 0.023 0.001 N/A N/A Total 29 15.875 0.548 N/A N/A (b): One-Way ANOVA for Strain at Failure Source DF Sum of Squares (SS) Mean Square (MS) F-value p-value Between Groups 5 12.927 2.585 1090.68 <0.001 Within Groups 24 0.057 0.002 N/A N/A Total 29 12.984 0.448 N/A N/A Table 4. Selected Pairwise Comparisons from Tukey's HSD Post-Hoc Test (α=0.05; Following Significant ANOVA). (a) Shear Stress Group 1 Group 2 Mean Difference (MPa) Adjusted p-value Significant? Acetone 25°C Acetone 75°C -0.776 <0.001 Yes Acetone 25°C Thermal 140°C -1.422 <0.001 Yes Acetone 25°C Thermal 160°C -1.776 <0.001 Yes Thermal 100°C Thermal 160°C -0.876 <0.001 Yes Thermal 120°C Thermal 140°C -0.350 <0.001 Yes Thermal 140°C Thermal 160°C -0.354 <0.001 Yes (b) Strain at Failure Group 1 Group 2 Mean Difference (%) Adjusted p-value Significant? Acetone 25°C Acetone 75°C -1.636 <0.001 Yes Acetone 25°C Thermal 160°C -1.658 <0.001 Yes Thermal 100°C Thermal 160°C -1.680 <0.001 Yes Thermal 120°C Thermal 140°C -0.048 0.999 No Thermal 140°C Thermal 160°C -1.122 <0.001 Yes Acetone 75°C Thermal 100°C 1.658 <0.001 Yes Table 5. Linear Regression Results Modeling Temperature Effects on Mean Shear Stress and Strain (Thermal Groups Only, 100–160°C). Dependent Variable Slope (per °C) Intercept R² F-value p-value Equation Shear Stress (MPa) 0.015 0.854 0.995 596.32 <0.001 Stress = 0.015 * Temp + 0.854 Strain (%) 0.009 2.058 0.629 5.08 0.109 Strain = 0.009 * Temp + 2.058 3.1 Fractography and Failure Mechanisms Fractographic analysis performed according to the method described in Section 2.4 offered information on the failure mechanisms behind the mechanical performance patterns reflected in the shear stress-strain curves (Figure 2) and statistical summaries (Tables 2-5). This analysis showed a shift between brittle adhesive failure in acetone assisted bonding and ductile cohesive failure in thermal bonding, with thermal degradation observed at higher temperatures. with pre-fracture cross-sections to assess initial microstructure in the bonding area and post-fracture views to evaluate fracture modes. Quantitative measurements were performed on the upper PLA side to measure interdiffusion to avoid artifacts on the lower side of thermal specimens due to degradation. Pre-fracture SEM cross-sections (Figure 4) illustrated the effect of bonding method on microstructure in the bonding zone. In acetone-assisted bonding at 25°C, the surface morphology after bonding was smooth with no measurable interdiffusion and only molten surface sticking, potentially reflecting little molecular mixing since only specific components of ABS were dissolved (Figure 4a). The thermal bonding exhibited progressive interdiffusion: at 120°C, a zone of 0.393 mm (393 µm) on bonding area with moderate lower surface degradation (low voids 26.2%; Figure 4b), and at 160°C, a wider zone of 0.475 mm (475 µm) on bonding area but severe lower degradation (void density ~23.6%, Ra ≈ 6 µm; Figure 4c), and Figure 4d indicative of heat-induced effects such as partial melting. These pre-fracture images showed a layered cylindrical filament with raster patterns of ±45° and inter-filament voids, more connected in thermal states. The macroscopic appearance of post-fracture (Figure 3) verifies the brittle vs. ductile evidence: the acetone bonding in 25°C showed clean separation (brittle adhesive failure Ra≈4; Figure 3a), and the 140°C thermal bonded extensively tore and raster pull-out (ductile cohesive failure Ra ≈7 µm; Figures 3b). It was supported by high-magnification details, thermal samples also presented fibrillated structures with microvoids and corresponded to higher strengths and strains [28](For example: 3.314 MPa and 4.736% at 160°C). These results provide a mechanistic understanding of the ANOVA-confirmed differences (p 140°C) due to degradation. The analysis highlights the impact of temperature that promotes cohesive failure and provides a guideline to optimize multi-material in AM joints. 3.2 Finite Element Analysis and Experimental Correlation The FEA simulation outcomes (Figure 5a) indicated that the von Mises stresses were high at the boundary of overlap region as expected in failure initiation locations in a lap joint. The simulated failure mode (Figure 5b) was very similar to those observed in experiments, when stress transfer caused delamination and raster pull-out of the FDM structure. Such high consistency between the simulation and SEM evidence confirms the conclusion that, with optimal thermal bonding (e.g., 140°C with 2.96 ± 0.02 MPa strength), the interface is no longer the weakest link; rather, the failure will spread in the bulk microstructure, as evidenced in the ANOVA differences (Table 3). 3.3 Summary of Mechanistic Transition The combined mechanical, fractographic and computational investigations indicate a clear change in mechanism in the change of adhesive versus cohesive failure as the bonding process changes from acetone-assisted bonding to thermal bonding. The acetone bonding provides a poor, brittle interface because of a combination of incompatible solubility and limited interdiffusion, restricting joint performance to surface adhesion. In contrast, thermal bonding at 120°C and 140°C forces the polymer chains to reptate, binding and entangling, producing a strong interpenetrated network that promotes ductile failure in the adherends. Although 160°C reaches the maximum of interdiffusion and mechanical properties, but SEM observed degradation underscores the need for temperature optimization to avoid excessive heating. Such transition between the dependence of bonding conditions on both shear strength and ductility (covered in Section 3) provides a very basic insight to customize bonding conditions in multi-material AM, a tradeoff between interfacial strength and material integrity. 4. Discussion Findings of the study show the obvious advantages of thermal bonding of ABS-PLA joints in comparison with the acetone-assisted method, because of shifting from brittle adhesive failure to ductile cohesive failure, reflected in Section 3 and fractographic patterns (Section 3.1 ). The poor performance of acetone bonding is attributed to its selective dissolution of ABS and inability to affect PLA, leaving a weak interface relying on van der Waals forces which leads to clean separation without filament deformation (Fig. 3 a). This is consistent with the lower shear strengths at 25°C and 75°C where failure is abrupt and at interface.Thermal bonding, however, provides the thermal energy required to allow chain mobility above glass transition temperatures of the polymers, so interdiffusion and entrenchment occur at the interface. At 120,140°C, this gives cohesive failure that tears filament, raster-pulls out, and forms microvoids (Figs. 3 b and 4 b-c), effectively spreading the stress over the FDM microstructure as supported by FEA simulations that exhibit adherend limited failure. The linear relationship between shear strength and temperature (Section 3 ) indicates the progressive improvement through increased molecular mixing, whereas weaker strain correlation might be associated with competing degradation at 160°C, where the peak performance (3.31 ± 0.02 MPa strength, 4.74 ± 0.03% strain) overlaps SEM visualized voids and roughness (Fig. 4 d-e). This puts 140°C as the best compromise, to get a good combination of strength and ductility without causing excessive thermal damages. These findings exhibit great reproducibility (CV < 1.2%; Table 2 ), adding to the previous studies about polymer welding in AM, in that the temperature level at which cohesive bonding occurs in dissimilar thermoplastics was quantified. Also, suggest concrete advantages to sustainable manufacturing, including easy repairability and recycling of multimaterial components, and put limits on the potential of high temperatures associated with embrittlement or degradation. All this information can be used to make a strong AM assembly, and engineers can even interconnect bonding settings with manufacturing parameters. 5. Conclusion This work gives a thorough framework of the joining of dissimilar thermoplastics that is, ABS and PLA. Tables show that thermal bonding is far better than our ambient solvent bonding, with an acceptable process temperature of 140°C resulting in a robust shear strength of 2.96 ± 0.02 MPa a two-fold improvement over acetone at 25°C (1.54 ± 0.02 MPa). The results using ANOVA (p < 0.001; Table 3 ) and post-hoc tests (Table 4 ) reinforce the above distinctions and regression (Table 5 ) also indicates a linear push towards performance with temperature. The main process lying behind such improvements is a switch of failure mode from weak adhesive to a strong cohesive. Fluctuations in the mechanical properties of these polymers were observed to be associated with this temperature dependent compositional change brought about by temperature-resistant intersubstratal molecular interdiffusion across the polymer interface, which was authenticated via an interventional approach that integrated monitoring of mechanical properties, microstructural analysis using SEM, and predictive modeling through computational calculations.In the end, the research presents a mechanistically and experimentally oriented route towards reliable, high-performance multimaterial polymeric assemblies and applies the technique to additive manufacturing, taking the technology a step closer to its full potential as a mass production technology. A better resolution of the effects and considerations of bonding pressure, duration and the long-term life of such joints should also be explored in the future through cyclic loading and in deleterious environments. Declarations Author Contribution M.H.Z. conceived the initial research idea, designed and performed all experimental work including specimen preparation, mechanical testing, and SEM characterization, conducted the FEA simulations, analyzed the data and performed statistical analysis, and wrote the original draft of the manuscript. F.R.B. supervised the research project, secured resources and funding, and critically revised the manuscript for important intellectual content. B.M.D. provided supervision on mechanical testing methodology and ISO 4587 standard implementation, contributed to the interpretation of failure mechanisms, and reviewed and edited the manuscript.All authors discussed the results, provided critical feedback, and approved the final version of the manuscript for submission. 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Author Field A (2013) Discovering statistics using IBM SPSS statistics, 4th edn. Sage Kovan V, Altan G, Topal ES et al Surface roughness effect on the 3D printed butt joints strength. In Proceedings of the 8th International Scientific Conference BALTTRIB 2015 (pp. 117–121) Delda RNM, Tuazon BJ, Dizon JRC (2020) Assessment of interfacial adhesion of adhesively bonded 3D-printed thermoplastics. Mater Sci Forum 1005:157–165 Kovan V, Altan G, Topal ES Effect of layer thickness and print orientation on strength of 3D printed and adhesively bonded single lap joints. J Mech Sci Technol, 31 (5), 2197–2201 Kariz M, Kuzman MK, Sernek M Adhesive bonding of 3D-printed ABS parts and wood. J Adhes Sci Technol, 31 (15), 1683–1690 Spaggiari A, Denti F Mechanical strength of adhesively bonded joints using polymeric additive manufacturing. Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science, 234 (2), 1–9 Cavalcanti DKK, Banea MD, Queiroz HFM Mechanical characterization of bonded joints made of additive manufactured adherends. Annals Dunarea de Jos Univ Galati Fascicle XII Weld Equip Technol, 30 , 27–33 Additional Declarations No competing interests reported. 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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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-8130352","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":554669535,"identity":"fb2b5f63-420f-4eb1-9149-bfb761334ab4","order_by":0,"name":"Mohammad Hadi Zahmatkeshan","email":"","orcid":"","institution":"Amirkabir University of Technology","correspondingAuthor":false,"prefix":"","firstName":"Mohammad","middleName":"Hadi","lastName":"Zahmatkeshan","suffix":""},{"id":554669536,"identity":"9e69f425-2dae-4784-91fc-e7b8e44b4695","order_by":1,"name":"Farid Reza Biglari","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAz0lEQVRIiWNgGAWjYBACA2YGxgMMDBJyMAEeYrQwgLQYMzAwE6uFAayFIbEBqoUwMGdnv3Dg5x6L9P4Z+QcYftQwyJg3ENBi2cxTcLDnmUTujBvJDIw9xxh4ZA4QcthhnoQDPAckchuAWhh4Gxh4JAg5DKTl4J8DEunyIFv+EqeF/cBhoC0JBkAtzETZAvQLw2GZAxKGG888Njgsc0yCsBZz/uMPH745UCcvdzwRyKixsSeoBRh3BnDmAWCcEtbAwMD+gBhVo2AUjIJRMJIBAJfUO2ZXc/fMAAAAAElFTkSuQmCC","orcid":"","institution":"Amirkabir University of Technology","correspondingAuthor":true,"prefix":"","firstName":"Farid","middleName":"Reza","lastName":"Biglari","suffix":""},{"id":554669537,"identity":"e1f9f0a7-1c9b-408e-83de-d5710e12def1","order_by":2,"name":"Bijan Mollaei Dariani","email":"","orcid":"","institution":"Amirkabir University of Technology","correspondingAuthor":false,"prefix":"","firstName":"Bijan","middleName":"Mollaei","lastName":"Dariani","suffix":""}],"badges":[],"createdAt":"2025-11-17 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09:22:54","extension":"xml","order_by":15,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":95752,"visible":true,"origin":"","legend":"","description":"","filename":"48b90b5d2f264175b4d7e40286710fdb1structuring.xml","url":"https://assets-eu.researchsquare.com/files/rs-8130352/v1/e49252a9d16568a0b4a979b3.xml"},{"id":97511777,"identity":"9db23d2a-c627-4a5c-bb50-86dd6e1391d7","added_by":"auto","created_at":"2025-12-05 09:22:54","extension":"html","order_by":16,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":102171,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-8130352/v1/3dada8b517a6c78c6361020c.html"},{"id":97511763,"identity":"6fd7bbcc-f301-4bab-99a2-d8a3d0a42398","added_by":"auto","created_at":"2025-12-05 09:22:54","extension":"jpeg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":604072,"visible":true,"origin":"","legend":"\u003cp\u003eExperimental methodology for ABS-PLA joint fabrication and testing. (a) Schematic of the ISO 4587 lap-shear specimen geometry, detailed in Table 1. (b) Heat blower-assisted bonding process, with localized heat application to the joint interface on the FDM printer bed. (c) Tensile testing setup on the SANTAM SMT-20 universal testing machine, with a bonded specimen mounted in the grips under load.\u003c/p\u003e","description":"","filename":"floatimage1.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8130352/v1/da32454ee0b32ee36bf6664e.jpeg"},{"id":97511764,"identity":"013c4bca-a1b5-4b71-b531-d3d4b966bf81","added_by":"auto","created_at":"2025-12-05 09:22:54","extension":"jpeg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":66989,"visible":true,"origin":"","legend":"\u003cp\u003eRepresentative shear stress-strain curves for ABS-PLA lap-shear joints under different bonding conditions. Curves illustrate the transition from lower strength and ductility in acetone-assisted bonding (25°C and 75°C) to higher performance in thermal bonding (100°C, 120°C, 140°C, 160°C). The 140°C condition shows an optimal balance of strength (2.96 ± 0.02 MPa) and strain (3.61 ± 0.03%), with data averaged from N=5 replicates per condition.\u003c/p\u003e","description":"","filename":"floatimage2.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8130352/v1/92d50aa8b1efdb397b533997.jpeg"},{"id":97671235,"identity":"a24405cd-f3cd-46ea-8454-ab878e2cedba","added_by":"auto","created_at":"2025-12-08 09:32:12","extension":"jpeg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":787003,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eMacroscopic views of failure modes in ABS-PLA joints. (a) Adhesive failure in an acetone-bonded specimen (25°C), showing clean interfacial separation(Ra≈4) (b) Cohesive failure in a thermally bonded specimen (140°C), exhibiting extensive tearing and plastic deformation within the bulk material(Ra ≈7 µm).\u003c/em\u003e\u003c/p\u003e","description":"","filename":"floatimage4.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8130352/v1/31aa4f29aca1d5d60d754815.jpeg"},{"id":97670939,"identity":"3f0dbc0c-4d8c-4338-bcb3-fc7a6781a52a","added_by":"auto","created_at":"2025-12-08 09:31:33","extension":"jpeg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":1277282,"visible":true,"origin":"","legend":"\u003cp\u003eScanning electron microscopy (SEM) micrographs of ABS-PLA joint fracture surfaces and cross-sections.Images represent key conditions (160°C, 120°C, and 25°C acetone) with quantified interdiffusion of PLA-ABS. (a) Smooth, featureless interface in acetone-bonded sample (25°C), indicating adhesive failure with no interdiffusion and only molten surface sticking(void density ~34.5%). (b) Extensive filament tearing and plastic deformation in thermally bonded sample at 120°C, with interdiffusion zone of 0.393 mm (393 µm) and degraded lower surface. (c) High-magnification view of fibrillated structures and microvoids at 160°C, with interdiffusion zone of 0.475 mm (475 µm) but severe lower degradation (void density ~23.6%), suggesting heat deformation.d) thermal Degaradation at 160°C. Images were obtained using AIS2300C SEM at Amirkabir University.\u003c/p\u003e","description":"","filename":"floatimage5.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8130352/v1/cdffc0e147d1f00a909cc72a.jpeg"},{"id":97671785,"identity":"59b757da-1e03-4847-b2fd-8ebb7685ab9d","added_by":"auto","created_at":"2025-12-08 09:33:05","extension":"jpeg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":446898,"visible":true,"origin":"","legend":"\u003cp\u003eFinite element analysis (FEA) simulations of ABS-PLA lap-shear joints using ABAQUS. (a) Von Mises stress distribution under tensile load, showing concentrations (red/yellow regions) at the overlap edges, predicting failure initiation sites. (b) Simulated failure mode, illustrating deformation, raster pull-out, and cohesive tearing that closely matches experimental observations in thermally bonded samples (e.g., at 140°C). Simulations validate the transition to ductile failure observed in the data (e.g., 3.61 ± 0.03% strain).\u003c/p\u003e","description":"","filename":"floatimage6.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-8130352/v1/2b82db36b63bd59657c695b2.jpeg"},{"id":97671520,"identity":"f35d46aa-6c61-4bbc-b6bf-3a59ff6f18ad","added_by":"auto","created_at":"2025-12-08 09:32:41","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":91405,"visible":true,"origin":"","legend":"\u003cp\u003eScatter plots of all individual replicates (N=5 per condition) for (a) shear stress and (b) strain at failure vs. temperature, with acetone in red circles (dashed fit) and thermal in blue triangles (solid fit). Separate regressions highlight trends within each method (acetone: lower slopes; thermal: stronger positive relationships, R²=0.995 for stress). This visualization supports the significant differences from ANOVA (Table 3) and post-hoc tests (Table 4).\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-8130352/v1/bc73767685877bc278c0f8ae.png"},{"id":98946195,"identity":"24f1ff5f-57d7-4148-a231-c1d84d157604","added_by":"auto","created_at":"2025-12-24 12:25:24","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":3998489,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8130352/v1/e96b5d95-956d-412e-b050-0f68e0519402.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Optimizing In-Situ Adhesive Bonding for Multi-Material Additive Manufacturing: Mechanistic Comparison of Solvent-Assisted and Thermal Methods for ABS-PLA Joints","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eMulti-material additive manufacturing (AM), with a focus on fused deposition modeling (FDM), can be used to produce functionally graded parts where multiple polymers with different properties are combined to make parts with complementary properties [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. An example of such synergy is PLA and ABS: PLA has high stiffness and is biodegradable and easy to process, whereas ABS is impact resistant, ductile, with higher glass transition temperature(T_g\u0026thinsp;\u0026asymp;\u0026thinsp;105\u0026deg;C) [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. These hybrids can be used for applications such as custom prosthetics, lightweight automobile parts, and electronics [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eNonetheless, thermodynamic and chemical incompatibilities, such as the non-polar nature of the ABS and the polar ester groups in the PLA, lead to the poor strength of the ABS-PLA interfaces and limitation in diffusion of the molecules [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. Different thermal properties (T_g,PLA\u0026thinsp;\u0026asymp;\u0026thinsp;60\u0026deg;C vs. T_g,ABS\u0026thinsp;\u0026asymp;\u0026thinsp;105\u0026deg;C) also results in residual stresses and delamination on cooling stage [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eSolvent bonding, using agents like acetone, dissolves surfaces to promote entanglement but is limited for dissimilar pairs due to selective solubility. Acetone effectively targets ABS but minimally affects PLA, resulting in asymmetric and weak interfaces [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e, \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. Thermal bonding applies heat and pressure to enable chain reptation and interdiffusion above Tg, according to reptation theory [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e], but precise care is needed to avoid \"cold\" welds or degradation [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eThere is a lack of systematic comparisons of the methods for ABS-PLA, often focusing on single techniques or in-print adhesion rather than post fabrication joining [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. Few studies integrate mechanical testing with microstructural and computational analyses to unfold failure mechanisms, and benchmarking using standards such as ISO 4587 is rare, specifically for sustainability aspects such as reparability [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. Previous publications report shear strengths less than 2 MPa, without any optimization towards ductility or degradation threshold [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eThis study bridges these gaps by performing a comparison between chemical bonding (25\u0026deg;C and 75\u0026deg;C) and thermal bonding (100 to 160\u0026deg;C) of ABS-PLA lapshear joints, in accordance with ISO 4587.Using mechanical testing, SEM fractography, and FEA, we show a transition from adhesive to cohesive failure, with peak shear strengths of 3.31\u0026thinsp;\u0026plusmn;\u0026thinsp;0.02 MPa at 160\u0026deg;C and an optimal 2.96\u0026thinsp;\u0026plusmn;\u0026thinsp;0.02 MPa at 140\u0026deg;C, representing a 92% increase, nearly doubling the performance of acetone bonding at 25\u0026deg;C. This mechanistic framework is new in the literature, supporting reliable multi-material AM for sustainable reparability and recycling [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e].\u003c/p\u003e"},{"header":"2. Materials and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003e2.1 Materials\u003c/h2\u003e\u003cp\u003eThe materials used in this research were commercial filaments of white polylactic acid (PLA) and black acrylonitrile butadiene styrene (ABS), namely, eSUN PLA\u0026thinsp;+\u0026thinsp;and eSUN ABS\u0026thinsp;+\u0026thinsp;grades, with a 1.75 mm nominal diameter, which were selected due to their contrasting colors to clearly observe fracture interface examination during post-testing characterization [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. The acetone-assisted bonding was conducted using high-purity acetone (\u0026ge;\u0026thinsp;99.5%) because it has been shown to perform well in dissolving ABS and allow controlled means for investigation of the selective solubility effects on PLA interfaces.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\u003ch2\u003e2.2 Specimen Preparation and Joint Fabrication\u003c/h2\u003e\u003cp\u003eTensile lap-shear test specimens were designed and manufactured strictly in accordance with ISO 4587 standard, which offers a standardized method of examining the tensile lap-shear strength of rigid-to-rigid bonded assemblies [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. The printed adherends were manufactured through a fused deposition modeling (FDM) printer, namely the Creality Ender 3 Pro model, to achieve uniform quality and quasi-isotropic mechanical properties necessary to make reliable mechanical comparisons.\u003c/p\u003e\u003cp\u003ePrinting parameters were optimized and kept consistent between speciemens, including; a layer height of 0.2 mm, 100% infill density, to minimize anisotropy effects[\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e], nozzle and bed temperatures set to 210\u0026deg;C and 60\u0026deg;C respectively in the case of PLA, nozzle temperature of 240\u0026deg;C in the case of ABS, and a constant print speed of 50 mm/s.\u003c/p\u003e\u003cp\u003eThese settings were selected due to previous optimization studies in order to maintain a balance between print quality, material flow, and interlayer adhesion, to reduce variability in the baseline adherend properties that are expected to affect the joint performance. The size of the overlap region was meticulously controlled as the ISO 4587 standard, a 12.5 mm width and an overlap length of 25 mm was created (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e-a). It should be noted that maintaining experimental consistency in dissimilar polymer systems, where misalignment can significantly amplify interfacial weaknesses [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eTwo key bonding techniques were evaluated for structured comparison of solvent-based and thermal approaches: solvent aided bonding using acetone and thermal aided bonding using a heat blower. For each type of bonding condition, five specimens (N\u0026thinsp;=\u0026thinsp;5) were produced as a replicate to provide sufficient statistical power, to detect differences in shear strength, and consider inevitable variability of FDM-printed materials in line with guidelines of experimental design for mechanical testing [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e].\u003c/p\u003e\u003cdiv id=\"Sec5\" class=\"Section3\"\u003e\u003ch2\u003e2.2.1 Acetone-Assisted Bonding\u003c/h2\u003e\u003cp\u003eABS-PLA lap-shear joints were prepared using acetone as a solvent-based adhesive at two distinct temperatures to investigate the influence of thermal assistance on solvent efficacy. At ambient temperature (25\u0026deg;C), a controlled volume of 50 \u0026micro;L of acetone was applied evenly to the surface of the ABS adherend in the overlap region, after which the PLA adherend was immediately brought into contact with the wetted ABS surface using the custom jig; a constant pressure of 50 kPa was then applied for 60 seconds to promote initial adhesion,[\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e] followed by curing at 25\u0026deg;C for a minimum of 24 hours to allow complete solvent evaporation and bond solidification. Under the higher temperature condition (75\u0026deg;C), the procedure followed the same steps, only that the ABS surface was moistened with acetone but the bonding process was carried out in an oven maintained at 75\u0026deg;C, a temperature strategically controlled beyond the glass transition temperature (T_g of PLA\u0026thinsp;\u0026asymp;\u0026thinsp;60\u0026deg;C), but below that of ABS (\u0026asymp;\u0026thinsp;105\u0026deg;C), so as to investigate the effects of softening the PLA without affecting the integrity of ABS [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]; the 50 kPa pressure with the same duration were applied, with initial solvent evaporation occurring, followed by the standard 24-hour curing at 25\u0026deg;C.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec6\" class=\"Section3\"\u003e\u003ch2\u003e2.2.2 Heat Blower-Assisted Bonding\u003c/h2\u003e\u003cp\u003eTo determine the temperature range for the heat blower-assisted bonding method at which the ABS-PLA lap-shear joints could be formed adequately, a range of four and gradually increasing temperatures was used 100\u0026deg;C, 120\u0026deg;C, 140\u0026deg;C, and 160\u0026deg;C to see the thermal optimal molecular interdiffusion and monitor whether any degradation can occur. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e-b, a Steinel HG 2320 E heat blower was applied with a precision nozzle to apply localized heat directly to the overlap area but not excessive heat to the surrounding, thus ensuring controlled application of energy to the overlap region. The temperature at the joint interface was real-time measured and controlled using Fluke 62max\u0026thinsp;+\u0026thinsp;infrared laser thermometer, which preformed non-contact sensing via dual laser beams, with an accuracy within \u0026plusmn;\u0026thinsp;1.5\u0026deg;C to minimize thermal gradients and enable fine tune temperature control, addressing limitations in previous studies of thermal bonding that introduce variable results and low strengths due to inconsistent heating temperatures [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. As soon as the desired temperature was attained and stabilized for 30 seconds, the constant pressure of 50 kPa was applied via the custom jig, and the joint was allowed to cool naturally to ambient temperature. The exact duration of heat application and pressure applied was calibrated through trial runs to have the optimum interdiffusion without the risk of the materials deforming or a significant thermal degradation, especially at higher temperatures nearing the melting point of PLA (\u0026asymp;\u0026thinsp;190\u0026deg;C).\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\u003ch2\u003e2.3 Mechanical Testing\u003c/h2\u003e\u003cp\u003eThe tensile lapshear tests used to evaluate mechanical performance of the bonded joints, carried out in accordance with ISO 4587 standard to ensure comparability with international benchmarks [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. The tests were conducted on the universal testing machine (SANTAM STM-20 in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e-c) with a 20 kN load cell. Tests were conducted at a fixed rate of head displacement of 5 mm/min until complete specimen failure with continuously recorded load-displacement data to record full stress-strain response. Based on these data, the ultimate shear stress (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\tau\\:}_{ult}\\)\u003c/span\u003e\u003c/span\u003e) was calculated by dividing the maximum load (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{F}_{max}\\)\u003c/span\u003e\u003c/span\u003e) by the nominal overlap area (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{A}_{overlap}\\)\u003c/span\u003e\u003c/span\u003e), using the formula [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]:\u003cdiv id=\"Equa\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equa\" name=\"EquationSource\"\u003e\n$$\\:{\\tau\\:}_{ult}=\\frac{{F}_{max}}{{A}_{overlap}}$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003ePlots of stress versus strain were generated thereafter to provide detailed insights into the elastic modulus, yield behavior, and plastic deformation characteristics of the joints under shear loading.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eDimensions and parameters for the adhesive joint test specimen according to ISO 4587.\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"3\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eParameter\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eSymbol\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eValue (mm)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSpecimen width\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e25\u0026thinsp;\u0026plusmn;\u0026thinsp;0.25\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBonded area length\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e12.5\u0026thinsp;\u0026plusmn;\u0026thinsp;0.25\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eLength gripped in jaws\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e37.5\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eLength of each arm\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e100\u0026thinsp;\u0026plusmn;\u0026thinsp;0.25\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\u003ch2\u003e2.4 Microstructural Characterization\u003c/h2\u003e\u003cp\u003eAfter mechanical testing, microstructural characterization was performed on the intact (pre-test) and fractured (post-test) specimens to understand the mechanism of failure, such as adhesive failure at the interface, cohesive failure within the ABS or PLA bulk or mixed-mode. This analysis evaluated surface morphology for evidence of filament tearing, plastic deformation, or thermal effects, and allowed the correlations with shear strength and stress-strain behavior. Each bonding condition was represented by 4 specimens (acetone-assisted at 25\u0026deg;C; thermal at 120\u0026deg;C, 140\u0026deg;C, and 160\u0026deg;C).with 3 for pre-test imaging to assess initial bond formation and 2 for post-test imaging to evaluate failure evolution. Specimens were selected as per ISO 4587 compliant mechanical results to exemplify weak (acetone) and strong (optimal thermal) bonds.\u003c/p\u003e\u003cp\u003eSpecimens were sputter-coated with a thin layer of gold-palladium to help conductivity, and avoid charging artifact [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. AIS2300C scanning electron microscope (Amirkabir University) under high vacuum mode with 10\u0026ndash;15 kV acceleration voltage, secondary electron (SE) detectors for topography, and backscattered electron (BSE) detectors for compositional contrast. Multiple magnifications were used: 50\u0026ndash;100\u0026times; for overviews; 1000\u0026ndash;5000\u0026times; for details like fibrils or voids. images focused on the overlap region to document features such as fibril formation, interface sharpness, voids and cracks, surface roughness, material transfer, and raster patterns. Images were processed and quantified using Fiji (version 1.53). Fibril length and density for ductile deformation, surface roughness (Ra via profile plots) [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e], width of diffusion zone, and the degree of material transfer using area fraction analysis were among the metrics used. These quantitative results granted the possibility to make direct comparisons between the pre and post-test states and reinforced mechanistic correlations with mechanical data.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\u003ch2\u003e2.5 Finite Element Analysis (FEA) Simulation\u003c/h2\u003e\u003cp\u003eTo support the experimental findings with predictive accuracy, finite element modelling was conducted using ABAQUS software (version 2023) [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. According to the experimental model, a detailed 3D model of the ISO 4587 lapshear joint was created, which accurately replicated the experimental geometry in every detail, including the overlap region and adherend dimensions. The literature values and additional data from performed tensile tests of bulk printed samples were used to provide the material properties of ABS and PLA for Young's modulus, Poisson's ratio, yield strength, and ultimate tensile strength to support model fidelity [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. The ABS and PLA interface was modeled using a cohesive zone element approach and then the tie constraints and surface-to-surface contact with friction were used to model the realistic failure and bonding progression. Boundary conditions modeled on the test setup used with the first end of the joint encastered in all degrees of freedom, and a tensile displacement load applied at a rate of 5 mm/min crosshead speed.\u003c/p\u003e\u003cp\u003eMeshing used a locally refined C3D8R brick element in the mesh vulnerable overlap area to capture stress intensities and deformations precisely and a smoother mesh elsewhere in less stressed regions to save computation time. Main aims of the simulations were to visualize distributions of von Mises stresses in the joint, predict initiation and propagation of failure and provide computational validation of the mechanical properties observed experimentally, including stress transfer resulting in cohesive failure in thermally bonded samples.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e\u003ch2\u003e2.6 Statistical Analysis\u003c/h2\u003e\u003cp\u003eFinally, statistical analysis was used on the quantitative data in order to assess differences between the bonding conditions. Descriptive statistics, such as means and standard deviations of peak shear stress and strain at failure, were computed for each group. A one-way analysis of variance (ANOVA) was utilized to compare the means of shear strengths of the different bonding conditions, assuming normality and homogeneity of variances, that was checked prior to the analysis using Shapiro- Wilk and Levene tests, respectively [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. In case ANOVA showed significant effects, Tukey Honestly Significant Difference ( HSD ) post-hoc testing was performed to determine any specific pairwise differences. Also, Regression analysis was used on the heat blower-assisted bonding records to model linear relationships between bonding temperature and ultimate shear strength, so the effects of temperature and the optimal temperature range were quantified. All analysis was carried out in SPSS software with a significance level set at α\u0026thinsp;=\u0026thinsp;0.05 [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e].\u003c/p\u003e\u003c/div\u003e"},{"header":"3. Results","content":"\u003cp\u003eThe bonding method and temperature significantly affected mechanical response of ABS-PLA lapshear joints, as indicated in Figure 2 with shear stress-strain curves. Acetone assisted bonding temperatures 25\u0026deg;C and 75\u0026deg;C demonstrated comparatively low peak shear strengths 1.54 \u0026plusmn; 0.02 MPa and 2.31 \u0026plusmn; 0.02 MPa, respectively, and moderate strains at failure: 3.08 \u0026plusmn; 0.02% and 4.71 \u0026plusmn; 0.02%.The failure was sudden, and this suggests a brittle interface.\u003c/p\u003e\n\u003cp\u003eThermal bonding by contrast had a significant increase in shear strength with peak strengths increasing to 3.31 \u0026plusmn; 0.02 MPa at 160\u0026deg;C compared to 2.44 \u0026plusmn; 0.02 MPa at 100\u0026deg;C . Ductility fluctuated, drop in strain at 100\u0026deg;C, 3.06 \u0026plusmn; 0.02%, in comparison to 75\u0026deg;C, suggesting a stiffer interface at this transition temperature. The best balance between strength and ductility was recorded at 120\u0026deg;C and 140\u0026deg;C with shear strengths of 2.61 \u0026plusmn; 0.03 MPa and 2.96 \u0026plusmn; 0.02 MPa and strains at failure of 3.57 \u0026plusmn; 0.04% and 3.61 \u0026plusmn; 0.03%, respectively. The highest shear strength, 3.31 \u0026plusmn; 0.02 MPa and strain 4.74 \u0026plusmn; 0.03% were recorded at a temperature of 160\u0026deg;C. though SEM analysis (as discussed below) indicates the onset of thermal degradation along with this behavior as shown in Figure 4-d. No anomalies or outliers were evident across replicates, also there was a steady increase in values with temperature increase, with a low coefficient of variation (CV \u0026lt;1.2%), demonstrating a high degree of experimental reproducibility.\u003c/p\u003e\n\u003cp\u003eTable 2. Descriptive Statistics for Shear Stress (MPa) and Strain at Failure (%) Across Bonding Conditions (N=5 Replicates per Group).\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eBonding Method\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eTemp (\u0026deg;C)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eMean Stress (MPa)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eSD Stress (MPa)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eMin Stress (MPa)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eMax Stress (MPa)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eCV Stress (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eMean Strain (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eSD Strain (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eMin Strain (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eMax Strain (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eCV Strain (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eAcetone\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e25\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e1.54\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e1.51\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e1.56\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e1.24\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e3.08\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e3.05\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e3.11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.75\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eAcetone\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e75\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e2.31\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e2.29\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e2.34\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.82\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e4.71\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e4.69\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e4.75\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.49\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eThermal\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e100\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e2.44\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e2.41\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e2.46\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.78\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e3.06\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e3.02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e3.08\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.75\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eThermal\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e120\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e2.61\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.03\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e2.58\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e2.64\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.96\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e3.57\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.04\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e3.52\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e3.62\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e1.15\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eThermal\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e140\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e2.96\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e2.93\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e2.99\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.78\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e3.61\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.03\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e3.58\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e3.65\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.80\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eThermal\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e160\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e3.314\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.023\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e3.29\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e3.35\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.69\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e4.736\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.025\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e4.70\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e4.76\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.53\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eTable 3 presents the results of the one way ANOVA, which indicate statistically noteworthy differences in all groups for both stress and strain ( p \u0026lt; 0.001). Post hoc analysis (Table 4) confirmed that all thermal bonding conditions were superior to both acetone conditions, as all pairwise comparisons of stress were significant. Regarding strain, Thermal 120\u0026deg;C and 140\u0026deg;C with p=0.999, did not exhibit significant differences in ductility; all other pairs did. Regression analysis of thermal groups (Table 5) also modeled temperature effects, showing a strong linear increase in stress (R\u0026sup2; = 0.995, p \u0026lt; 0.001) but having a non-significant, weak trend for strain (R\u0026sup2; = 0.629, p = 0.109)\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eTable 3. One-Way ANOVA Results for (a) Shear Stress and (b) Strain at Failure (6 Groups, N=5 per Group, Total N=30).\u003c/p\u003e\n\u003cp\u003e(a): One-Way ANOVA for Shear Stress\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eSource\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eDF\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eSum of Squares (SS)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eMean Square (MS)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eF-value\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003ep-value\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eBetween Groups\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e15.852\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e3.170\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e3254.92\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u0026lt;0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eWithin Groups\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e24\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.023\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eN/A\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eN/A\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eTotal\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e29\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e15.875\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.548\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eN/A\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eN/A\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e(b): One-Way ANOVA for Strain at Failure\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eSource\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eDF\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eSum of Squares (SS)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eMean Square (MS)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eF-value\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003ep-value\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eBetween Groups\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e12.927\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e2.585\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e1090.68\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u0026lt;0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eWithin Groups\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e24\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.057\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.002\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eN/A\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eN/A\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eTotal\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e29\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e12.984\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.448\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eN/A\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eN/A\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eTable 4. Selected Pairwise Comparisons from Tukey\u0026apos;s HSD Post-Hoc Test (\u0026alpha;=0.05; Following Significant ANOVA).\u003c/p\u003e\n\u003cp\u003e(a) Shear Stress\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eGroup 1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eGroup 2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eMean Difference (MPa)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eAdjusted p-value\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eSignificant?\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eAcetone 25\u0026deg;C\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eAcetone 75\u0026deg;C\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e-0.776\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u0026lt;0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eYes\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eAcetone 25\u0026deg;C\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eThermal 140\u0026deg;C\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e-1.422\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u0026lt;0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eYes\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eAcetone 25\u0026deg;C\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eThermal 160\u0026deg;C\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e-1.776\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u0026lt;0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eYes\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eThermal 100\u0026deg;C\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eThermal 160\u0026deg;C\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e-0.876\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u0026lt;0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eYes\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eThermal 120\u0026deg;C\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eThermal 140\u0026deg;C\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e-0.350\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u0026lt;0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eYes\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eThermal 140\u0026deg;C\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eThermal 160\u0026deg;C\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e-0.354\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u0026lt;0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eYes\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e(b) Strain at Failure\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eGroup 1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eGroup 2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eMean Difference (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eAdjusted p-value\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eSignificant?\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eAcetone 25\u0026deg;C\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eAcetone 75\u0026deg;C\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e-1.636\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u0026lt;0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eYes\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eAcetone 25\u0026deg;C\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eThermal 160\u0026deg;C\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e-1.658\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u0026lt;0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eYes\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eThermal 100\u0026deg;C\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eThermal 160\u0026deg;C\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e-1.680\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u0026lt;0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eYes\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eThermal 120\u0026deg;C\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eThermal 140\u0026deg;C\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e-0.048\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.999\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eNo\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eThermal 140\u0026deg;C\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eThermal 160\u0026deg;C\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e-1.122\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u0026lt;0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eYes\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eAcetone 75\u0026deg;C\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eThermal 100\u0026deg;C\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e1.658\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u0026lt;0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eYes\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eTable 5. Linear Regression Results Modeling Temperature Effects on Mean Shear Stress and Strain (Thermal Groups Only, 100\u0026ndash;160\u0026deg;C).\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"672\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eDependent Variable\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eSlope (per \u0026deg;C)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eIntercept\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eR\u0026sup2;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eF-value\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003ep-value\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eEquation\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eShear Stress (MPa)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.015\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.854\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.995\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e596.32\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u0026lt;0.001\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eStress = 0.015 * Temp + 0.854\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eStrain (%)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.009\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e2.058\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.629\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e5.08\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e0.109\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eStrain = 0.009 * Temp + 2.058\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003cstrong\u003e3.1 Fractography and Failure Mechanisms\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eFractographic analysis performed according to the method described in Section 2.4 offered information on the failure mechanisms behind the mechanical performance patterns reflected in the shear stress-strain curves (Figure 2) and statistical summaries (Tables 2-5). This analysis showed a shift between brittle adhesive failure in acetone assisted bonding and ductile cohesive failure in thermal bonding, with thermal degradation observed at higher temperatures. with pre-fracture cross-sections to assess initial microstructure in the bonding area and post-fracture views to evaluate fracture modes. Quantitative measurements were performed on the upper PLA side to measure interdiffusion to avoid artifacts on the lower side of thermal specimens due to degradation.\u003c/p\u003e\n\u003cp\u003ePre-fracture SEM cross-sections (Figure 4) illustrated the effect of bonding method on microstructure in the bonding zone. In acetone-assisted bonding at 25\u0026deg;C, the surface morphology after bonding was smooth with no measurable interdiffusion and only molten surface sticking, potentially reflecting little molecular mixing since only specific components of ABS were dissolved (Figure 4a). The thermal bonding exhibited progressive interdiffusion: at 120\u0026deg;C, a zone of 0.393 mm (393 \u0026micro;m) on bonding area with moderate lower surface degradation (low voids 26.2%; Figure 4b), and at 160\u0026deg;C, a wider zone of 0.475 mm (475 \u0026micro;m) on bonding area but severe lower degradation (void density ~23.6%, Ra \u0026asymp; 6 \u0026micro;m; Figure 4c), and Figure 4d indicative of heat-induced effects such as partial melting. These pre-fracture images showed a layered cylindrical filament with raster patterns of \u0026plusmn;45\u0026deg; and inter-filament voids, more connected in thermal states.\u003c/p\u003e\n\u003cp\u003eThe macroscopic appearance of post-fracture (Figure 3) verifies the brittle vs. ductile evidence: the acetone bonding in\u0026nbsp;25\u0026deg;C\u0026nbsp;\u0026nbsp;showed clean separation (brittle adhesive failure Ra\u0026asymp;4; Figure 3a), \u0026nbsp;and the\u0026nbsp;140\u0026deg;C thermal bonded\u0026nbsp;extensively tore and raster pull-out (ductile cohesive failure Ra \u0026asymp;7 \u0026micro;m; Figures 3b). It was supported by high-magnification details, thermal samples also presented fibrillated structures with microvoids and corresponded to higher strengths and strains [28](For example:\u0026nbsp;3.314 MPa and 4.736% at 160\u0026deg;C).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThese results provide a mechanistic understanding of the ANOVA-confirmed differences (p \u0026lt; 0.001) across conditions and attribute superior thermal performance to interdiffusion while noting the limit of applicability at higher temperatures (\u0026gt;140\u0026deg;C) due to degradation. The analysis highlights the impact of temperature that promotes cohesive failure and provides a guideline to optimize multi-material in AM joints.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e3.2 Finite Element Analysis and Experimental Correlation\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe FEA simulation outcomes (Figure 5a) indicated that the von Mises stresses were high at the boundary of overlap region as expected in failure initiation locations in a lap joint. The simulated failure mode (Figure 5b) was very similar to those observed in experiments, when stress transfer caused delamination and raster pull-out of the FDM structure. Such high consistency between the simulation and SEM evidence confirms the conclusion that, with optimal thermal bonding (e.g., 140\u0026deg;C with 2.96 \u0026plusmn; 0.02 MPa strength), the interface is no longer the weakest link; rather, the failure will spread in the bulk microstructure, as evidenced in the ANOVA differences (Table 3).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e3.3 Summary of Mechanistic Transition\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe combined mechanical, fractographic and computational investigations indicate a clear change in mechanism in the change of adhesive versus cohesive failure as the bonding process changes from acetone-assisted bonding to thermal bonding. The acetone bonding provides a poor, brittle interface because of a combination of incompatible solubility and limited interdiffusion, restricting joint performance to surface adhesion. In contrast, thermal bonding at 120\u0026deg;C and 140\u0026deg;C forces the polymer chains to reptate, binding and entangling, producing a strong interpenetrated network that promotes ductile failure in the adherends. Although 160\u0026deg;C \u0026nbsp;reaches the maximum of interdiffusion and mechanical properties, but SEM observed degradation underscores the need for temperature optimization to avoid excessive heating. Such transition between the dependence of bonding conditions on both shear strength and ductility (covered in Section 3) provides a very basic insight to customize bonding conditions in multi-material AM, a tradeoff between interfacial strength and material integrity.\u003c/p\u003e"},{"header":"4. Discussion","content":"\u003cp\u003eFindings of the study show the obvious advantages of thermal bonding of ABS-PLA joints in comparison with the acetone-assisted method, because of shifting from brittle adhesive failure to ductile cohesive failure, reflected in Section \u003cspan refid=\"Sec11\" class=\"InternalRef\"\u003e3\u003c/span\u003e and fractographic patterns (Section \u003cspan refid=\"Sec12\" class=\"InternalRef\"\u003e3.1\u003c/span\u003e). The poor performance of acetone bonding is attributed to its selective dissolution of ABS and inability to affect PLA, leaving a weak interface relying on van der Waals forces which leads to clean separation without filament deformation (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e3\u003c/span\u003ea). This is consistent with the lower shear strengths at 25\u0026deg;C and 75\u0026deg;C where failure is abrupt and at interface.Thermal bonding, however, provides the thermal energy required to allow chain mobility above glass transition temperatures of the polymers, so interdiffusion and entrenchment occur at the interface. At 120,140\u0026deg;C, this gives cohesive failure that tears filament, raster-pulls out, and forms microvoids (Figs.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e3\u003c/span\u003eb and \u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e4\u003c/span\u003eb-c), effectively spreading the stress over the FDM microstructure as supported by FEA simulations that exhibit adherend limited failure. The linear relationship between shear strength and temperature (Section \u003cspan refid=\"Sec11\" class=\"InternalRef\"\u003e3\u003c/span\u003e) indicates the progressive improvement through increased molecular mixing, whereas weaker strain correlation might be associated with competing degradation at 160\u0026deg;C, where the peak performance (3.31\u0026thinsp;\u0026plusmn;\u0026thinsp;0.02 MPa strength, 4.74\u0026thinsp;\u0026plusmn;\u0026thinsp;0.03% strain) overlaps SEM visualized voids and roughness (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e4\u003c/span\u003ed-e). This puts 140\u0026deg;C as the best compromise, to get a good combination of strength and ductility without causing excessive thermal damages.\u003c/p\u003e\u003cp\u003eThese findings exhibit great reproducibility (CV\u0026thinsp;\u0026lt;\u0026thinsp;1.2%; Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e), adding to the previous studies about polymer welding in AM, in that the temperature level at which cohesive bonding occurs in dissimilar thermoplastics was quantified. Also, suggest concrete advantages to sustainable manufacturing, including easy repairability and recycling of multimaterial components, and put limits on the potential of high temperatures associated with embrittlement or degradation. All this information can be used to make a strong AM assembly, and engineers can even interconnect bonding settings with manufacturing parameters.\u003c/p\u003e"},{"header":"5. Conclusion","content":"\u003cp\u003eThis work gives a thorough framework of the joining of dissimilar thermoplastics that is, ABS and PLA. Tables show that thermal bonding is far better than our ambient solvent bonding, with an acceptable process temperature of 140\u0026deg;C resulting in a robust shear strength of 2.96\u0026thinsp;\u0026plusmn;\u0026thinsp;0.02 MPa a two-fold improvement over acetone at 25\u0026deg;C (1.54\u0026thinsp;\u0026plusmn;\u0026thinsp;0.02 MPa). The results using ANOVA (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001; Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e) and post-hoc tests (Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e) reinforce the above distinctions and regression (Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e) also indicates a linear push towards performance with temperature. The main process lying behind such improvements is a switch of failure mode from weak adhesive to a strong cohesive. Fluctuations in the mechanical properties of these polymers were observed to be associated with this temperature dependent compositional change brought about by temperature-resistant intersubstratal molecular interdiffusion across the polymer interface, which was authenticated via an interventional approach that integrated monitoring of mechanical properties, microstructural analysis using SEM, and predictive modeling through computational calculations.In the end, the research presents a mechanistically and experimentally oriented route towards reliable, high-performance multimaterial polymeric assemblies and applies the technique to additive manufacturing, taking the technology a step closer to its full potential as a mass production technology. A better resolution of the effects and considerations of bonding pressure, duration and the long-term life of such joints should also be explored in the future through cyclic loading and in deleterious environments.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eM.H.Z. conceived the initial research idea, designed and performed all experimental work including specimen preparation, mechanical testing, and SEM characterization, conducted the FEA simulations, analyzed the data and performed statistical analysis, and wrote the original draft of the manuscript. F.R.B. supervised the research project, secured resources and funding, and critically revised the manuscript for important intellectual content. B.M.D. provided supervision on mechanical testing methodology and ISO 4587 standard implementation, contributed to the interpretation of failure mechanisms, and reviewed and edited the manuscript.All authors discussed the results, provided critical feedback, and approved the final version of the manuscript for submission.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eThe data supporting the findings of this study, including raw tensile test measurements and simulation outputs from Abaqus, are available from the corresponding authors upon reasonable request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eGibson I, Rosen D, Stucker B, Khorasani M, Rosen D, Stucker B, Khorasani M (2021) Additive manufacturing technologies, vol 17. Springer, Cham, Switzerland, pp 160\u0026ndash;186\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eNgo TD, Kashani A, Imbalzano G, Nguyen KTQ, Hui D (2018) Additive manufacturing (3D printing): A review of materials, methods, applications and challenges. Compos Part B: Eng 143:172\u0026ndash;196\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eFarah S, Anderson DG, Langer R (2016) Physical and mechanical properties of PLA, and their functions in widespread applications\u0026mdash;A comprehensive review. Adv Drug Deliv Rev 107:367\u0026ndash;392\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eTymrak BM, Kreiger M, Pearce JM (2014) Mechanical properties of components fabricated with open-source 3-D printers. Mater Design 58:242\u0026ndash;246\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eDilberoglu UM, Gharehpapagh B, Yaman U, Dolen M (2017) The role of additive manufacturing in the era of Industry 4.0. Procedia Manuf 11:545\u0026ndash;554\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eTiwary VK, Arunkumar P, Kulkarni PM (2020) Micro-particle grafted eco-friendly polymer filaments for 3D printing technology. Materials Today: Proceedings, 28, 1980\u0026ndash;1984\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eKovan V, Altan G, Topal ES (2017) Effect of layer thickness and print orientation on strength of 3D printed and adhesively bonded single lap joints. J Mech Sci Technol 31(5):2197\u0026ndash;2201\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eTuazon BJ, Espino MT, Dizon JRC (2023), June Lap shear strength assessment of acetone welded 3D-printed ABS polymer. In Materials Science Forum (Vol. 1087, pp. 149\u0026ndash;154). 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J Adhes Sci Technol, \u003cem\u003e31\u003c/em\u003e(15), 1683\u0026ndash;1690\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eSpaggiari A, Denti F Mechanical strength of adhesively bonded joints using polymeric additive manufacturing. \u003cem\u003eProceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science, 234\u003c/em\u003e(2), 1\u0026ndash;9\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eCavalcanti DKK, Banea MD, Queiroz HFM Mechanical characterization of bonded joints made of additive manufactured adherends. Annals Dunarea de Jos Univ Galati Fascicle XII Weld Equip Technol, \u003cem\u003e30\u003c/em\u003e, 27\u0026ndash;33\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":"Multi-Material Additive Manufacturing, ABS-PLA Bonding, Lap-Shear Strength, ISO 4587, Thermal Bonding, Polymer Interdiffusion, Finite Element Analysis, Cohesive Failure","lastPublishedDoi":"10.21203/rs.3.rs-8130352/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8130352/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe robust joining of dissimilar polymers, such as acrylonitrile butadiene styrene (ABS) with polylactic acid (PLA) is essential to promote multi-material additive manufacturing (AM). This work systematically compares acetone assisted solvent bonding at 25 and 75\u0026deg;C to direct thermal bonding at 100\u0026ndash;160\u0026deg;C for ABS-PLA lap-shear joints, by use of ABS as an in-situ adhesive and according to ISO 4587, as standard. The optimal thermal bonding temperature was 140\u0026deg;C as it yielded the highest shear strength of 2.2.96\u0026thinsp;\u0026plusmn;\u0026thinsp;0.02 MPa, which was a 92% improvement compared to acetone bond temperature of 25\u0026deg;C (1.54\u0026thinsp;\u0026plusmn;\u0026thinsp;0.02 MPa) and one-way ANOVA showed that there are trends that differ significantly between conditions (p\u0026thinsp;\u0026lt;\u0026thinsp;0.001).There was a mechanistic shift between the brittle adhesive failure in solvent-bonded joints to the ductile cohesive failure in thermally-bonded joints by temperature-enhanced molecular interdiffusion (zone widths up to 0.475 mm at 160\u0026deg;C). The use of scanning electron microscopy proved the occurrence of filament tear, plastic deformation and degradation in the specimens after heating (e.g., void density was about 23.6% at 160 C), whereas finite element analysis provided confirmation of stress distributions and mechanisms of failure. Such results offer the basis to optimize joining parameters towards reliable, repairable and sustainable multi-material AM structure via efficient, high-performance approach.\u003c/p\u003e","manuscriptTitle":"Optimizing In-Situ Adhesive Bonding for Multi-Material Additive Manufacturing: Mechanistic Comparison of Solvent-Assisted and Thermal Methods for ABS-PLA Joints","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-12-05 09:22:49","doi":"10.21203/rs.3.rs-8130352/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":"a023b2b6-0ff4-436b-b20c-b2c0191bc485","owner":[],"postedDate":"December 5th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-12-24T12:24:53+00:00","versionOfRecord":[],"versionCreatedAt":"2025-12-05 09:22:49","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8130352","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8130352","identity":"rs-8130352","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}