Bioinspired fabrication of 3D-printed composites based on multiscale and interfacial architecture of conch shells

The intricate microstructure of conch shells endows them with high mechanical properties. However, it is challenging to integrate bionic design into engineering materials due to the microscopic visualization and complexity of the shell structure. In this study, interlayer separation was achieved by precisely removing the soft organic tissue, revealing an interface microstructure characterized by convex features and alternating orientations. Notably, this unique microstructure influences angular deflection and tangential displacement when cracks propagate across different macroscopic layers-a phenomenon not previously reported in the literature. To elucidate the energy dissipation and crack propagation mechanisms of the conch shell, quasi-static in situ indentation and in situ impact experiments were conducted. Inspired by the structural characteristics of the conch shell, a microstructure-guided 3D printing strategy was developed to fabricate a polylactic acid (PLA) skeleton. Subsequently, a silicone elastomer was injected into the PLA skeleton under high pressure and solidified, resulting in a rigid-flexible coupled bio-inspired composite with a multi-scale layered structure. The multi-level cross-layered architecture significantly alters the crack propagation path, and the impact toughness of the conch shell-inspired composite improves by 215 % compared to the 3D-printed homogeneous PLA. Furthermore, the introduction of microstructural design between layers enhanced the impact resistance of the composite by an additional 85 %. The fabrication process and structural design principles presented in this study are broadly applicable to the development of high-strength composites using a variety of material systems. STATEMENT OF SIGNIFICANCE: The exceptional mechanical performance of conch shells originates from their multiscale hierarchical architecture and unique interfacial microstructures. This study elucidates their crack-deflection mechanisms and develops an innovative bio-inspired 3D printing strategy for advanced composites. Our approach enables precise control of material heterogeneity and complex geometries, facilitating next-generation impact-resistant materials development. This research establishes a transformative paradigm for engineering lightweight, high-performance impact-resistant materials with potential applications in aerospace systems, ballistic armor, and protective gear design.