Tailoring the compressive properties of 3D printed composites using bioinspired micro/macrostructure designs

Delicate hierarchical designs in natural composites are known to significantly enhance mechanical properties while maintaining light weight. By contrast, achieving complex structures with such properties in man-made composites remains a challenge. Recent advances combining 3D printing and shear forces have enabled the efficient and cost-effective fabrication of microstructured hierarchical structures. Inspired by the Bouligand structure in the mantis shrimp, we 3D printed glass microfiber-reinforced composites in porous Bouligand structures with lattice designs to yield lightweight, strong, and energy-absorbing composites. The bulk Bouligand composites exhibited the maximum compressive stress and energy absorption values of 117 MPa and 19 MJ/m³ at a pitch angle θ = 40°. Conversely, the lattice Bouligand composites with 25 and 50% porosity demonstrated superior compressive performance at θ = 90°, outperforming those at θ = 40°. Our investigation revealed the critical role of micro/macrostructure designs in tuning the compressive strength, modulus, and energy absorption. Fracture mechanisms in bulk composites such as crack twisting and crack bridging, were identified as key contributors to the enhanced compressive behavior. While in the Bouligand lattice structure, the crack propagated straight along the radial direction of the strut, and subsequently, crack bridging was generated near the nodes where glass microfibers were pulled out and broken. Numerical simulations further showed the local stress distributions within the lattice under compression, providing additional insights into their mechanical performance. These findings provide a promising design for high compressive strength and energy dissipation in lightweight composites for aerospace, architecture, or defense applications.