Mechanical performance of bio-inspired 3D printed composites for structural applications

This study investigates the flexural behavior of bio-inspired 3D-printed beams for lightweight structural applications. It includes two experimental programs: (i) nacre-inspired sandwich beams (BTL1-BTL6) printed in Stone Fill and PLA/PHA, and (ii) trabecular bone-inspired beams (B1/B2, also denoted ST1/ST2) printed in ASA and Viber’s PLA. Both beam families were manufactured in several pore-density configurations using fused filament fabrication (FFF). To isolate the effect of internal architecture, all specimens shared the same external dimensions. In total, 24 beams were tested under quasi-static three-point bending to evaluate load-displacement response, initial flexural stiffness, energy absorption, and failure mechanisms, supported by nonlinear finite-element modelling. The results show that internal topology strongly governs global flexural behavior. In general, trabecular bone-inspired beams exhibit higher initial stiffness than beetle-elytra-inspired beams, while selected medium- and large-pore configurations provide favorable stiffness-to-mass ratios and improved energy absorption. The bio-composite filament achieves stiffness and peak load comparable to ASA but usually shows more gradual post-peak softening and similar or higher absorbed energy, suggesting better damage redistribution. The numerical models reproduce the initial stiffness and relative trends across beam topologies and materials and reveal stress concentrations at strut junctions and pore edges consistent with observed crack-initiation sites. Finally, a parametric study was conducted to enable systematic geometry control of the ST2 architecture. Web and perforation areas were quantified, equivalent circular descriptors were defined, and the radii of 91 circles were parameterized to generate 100 beam configurations. This framework provides a basis for future design optimization and performance tailoring of trabecular inspired additively manufactured beam components.