Functionally graded materials (FGM) have attracted considerable attention in the field of composite materials and rekindled interest in research on composite materials due to their unique mechanical response achieved through material design and optimization. Compared to conventional composites, FGMs offer several advantages and exceptional properties, including improved deformation resistance, improved toughness, lightness properties, and excellent recoverability. This study focused on the production of functionally graded (FG) polymer materials by the additive manufacturing (AM) method. FG structures were produced by the fused deposition modeling (FDM) method using acrylonitrile benzidine styrene (ABS) and polylactic acid (PLA) materials, and tensile tests were performed according to ASTM D638. The effects of different layer thicknesses, volume ratios, and total thicknesses on mechanical behavior were investigated. The tensile standard of materials produced by additive manufacturing introduces geometric differences. Another motivation in this study is to reveal the differences between the results according to the ASTM standard. In addition, tensile tests were carried out by producing single-layer samples at certain volume ratios to create a numerical model with the finite element method to verify the experimental data. As a result of this study, it is presented that the FG structure produced with FDM improves mechanical behavior.

Auxetic re-entrant (RE) unit cell-based honeycombs exhibit a negative Poisson’s ratio (NPR) and possess a greater energy absorption capacity than conventional hexagonal honeycombs. The energy absorption capabilities of these structures can be further enhanced through design modifications. This study explores novel double-cylindrical-shell-based RE unit cell (REC) designs with negative Poisson’s ratios (NPRs), and the impact of material variations on NPR is analyzed in detail. The REC structures have two distinct geometric configurations: narrow REC (REC-N) and wide REC (REC-W). To demonstrate that these new geometries exhibit NPR behavior, samples were produced using additive manufacturing (AM) with materials including polylactic acid (PLA), acrylonitrile butadiene styrene (ABS), and functionally graded (FG) PLA-ABS composites. Compression tests were conducted on the samples, following ASTM-D695-15 standards, to determine the Poisson’s ratios. The experimental results obtained were validated against numerical results for all material combinations. It is demonstrated that the NPR can vary by up to 20% with changes in the REC cell geometry design for the same material combination. It is stated that changes in the material composition can alter the NPR by up to 11%. Therefore, it is shown that both the REC cell design and material variations lead to significant changes in the NPR.

In this study, the crank-arm of the slider-crank mechanism was produced with different raster angles (45°, 90°, 135°) and infill densities (25%, 50%, 75%, 100%). The effect of these parameters on the dynamics of the slider was investigated experimentally and numerically, and compared with a rigid version of the crank-arm. Firstly, analytical, numerical, and experimental results are obtained for the rigid crank-arm, and the results are compared. Secondly, experiments were carried out on the same experimental setup with 12 crank-arm specimens produced using PLA. Finally, experimental results of sliders were statistically analysed with rigid-body mechanism results, and the flexibility of the crank-arms produced with fused filament fabrication was verified through numerical simulations. As the infill density decreased, the flexibility of the crank-arm increased, and the deviations in the results also grew as the energy change due to the deformation increased. The raster angle had no significant effect on the results except for 25% infill density. However, with 25% infill density, the crank-arm with 90° raster angle followed the rigid crank-arm experimental results best. As a result, it has been observed that the crank-arm produced with different printing parameters has a significant effect on the dynamics of the slider.

Functionally graded materials (FGM) have attracted considerable attention in the field of composite materials and rekindled interest in research on composite materials, due to their unique mechanical response achieved through material design and optimization. Compared to conventional composites, FGMs offer several advantages and exceptional properties, including improved deformation resistance, improved toughness, lightness properties, and excellent recoverability. This study focused on the production of functionally graded (FG) polymer materials by additive manufacturing (AM) method. FG structures were produced by the Fused Deposition Modeling (FDM) method using Acrylonitrile benzidine styrene (ABS) and Polylactic acid (PLA) materials and tensile tests were performed according to ASTM D638. The effects of different layer thicknesses, volume ratios, and total thicknesses on mechanical behavior were investigated. In addition, tensile tests were carried out by producing single-layer samples at certain volume ratios to create a numerical model with the Finite element method to verify the experimental data. As a result of this study, it is presented that the FG structure produced with FDM improves mechanical behavior.

Although polylactic acid (PLA) and acrylonitrile–butadiene–styrene (ABS) are among the most widely used polymers in material extrusion, their limited toughness and energy-absorption capacity often restrict the structural performance of 3D-printed functional components. To address the limited comparative understanding of how thermoplastic polyurethane (TPU) modifies the deformation behavior and phase characteristics of these two polymer systems, this study presents a multi-analytical evaluation of TPU-reinforced PLA and ABS blends. To this end, both polymers were blended with TPU at 10–50 wt% and processed into filaments via single-screw extrusion. The resulting filaments were used to fabricate ASTM D638 Type I tensile specimens via material extrusion under matrix-specific, but internally consistent, printing parameters. For each composition, five specimens were tested to obtain representative values of tensile strength, elongation at break, and toughness. In addition to conventional tensile testing, the evolution of strain during deformation was monitored using digital image correlation (DIC), enabling full-field characterization of local deformation behavior. To ensure experimental reliability, specimen masses were carefully controlled, and the datasets were analyzed using MATLAB. Thermal properties were investigated by differential scanning calorimetry (DSC) to determine the influence of TPU on glass transition, melting behavior, and phase mobility, and to relate these thermal characteristics to the mechanical response of the blends. The incorporation of TPU significantly increased ductility and energy absorption in both polymer matrices, although the magnitude of improvement differed. ABS/TPU blends exhibited the highest toughness enhancement, reaching 221.4% at 30 wt% TPU, while PLA/TPU systems showed nearly a twofold increase at 20 wt% TPU. DIC analysis further revealed a transition from localized brittle deformation in neat polymers to more distributed plastic deformation with increasing TPU content. DSC results indicated reduced crystallinity in PLA-rich blends and enhanced segmental mobility in ABS-based systems, consistent with the observed mechanical behavior. Overall, the combined mechanical, optical, and thermal analyses demonstrate that the optimal TPU content is matrix-dependent, providing practical guidelines for tailoring PLA- and ABS-based filaments to achieve a controlled balance between stiffness, ductility, and energy absorption in material extrusion applications.