Stiffness Response of Topology-Optimized FDM Carbon-Fiber-Reinforced PLA Structures

Additive manufacturing enables the fabrication of lightweight composite structures with complex geometries; however, accurately predicting their structural response remains challenging when topology optimization introduces multiple thin load-bearing members and complex deposition paths. This study evaluated the end-to-end accuracy of a simplified engineering workflow that combines coupon-derived anisotropic material properties, isotropic topology generation, laminate shell analysis, geometry reconstruction, FDM fabrication, and component testing for short-carbon-fiber-reinforced PLA structures. In-plane elastic properties were characterized using ASTM D3039 tensile and ASTM D3518 shear tests and implemented in ANSYS Mechanical and ACP (Pre). Baseline and topology-derived brackets with different retained-mass targets were manufactured and tested under tensile loading. Experimental stiffness was determined using linear regression over the 25–60% range of each specimen’s maximum load, which provided highly linear fits across all specimens. The simulations systematically overpredicted experimental stiffness, with errors of approximately 14–52% for the baseline and minimum-compliance configurations. Mesh refinement and variations in the assumed out-of-plane elastic properties produced changes substantially smaller than the largest simulation–experiment discrepancies. The results therefore quantify the limitations of transferring coupon-calibrated homogeneous properties through a simplified topology-optimization and FDM workflow and show that the observed disagreement cannot be attributed to mesh density or the investigated out-of-plane material assumptions alone. The workflow is best interpreted as a preliminary engineering assessment rather than as validation of a high-fidelity constitutive or component model.