From tortoise exoskeletons to engineering: Innovating high-impact bio-composites with rigid-flexible grid structures

To address the inherent brittleness and low mechanical strength of natural fiber-reinforced polymer composites (NFPCs), this study proposes a bionic rigid-flexible composite inspired by the multi-layered architecture of turtle exoskeletons. Through co-extrusion processing, we engineered an innovative bio-composite (BPC-CFMP-F) by strategically integrating a continuous carbon fabric mesh prepreg and elastic cast film (MSF) into bamboo fiber/polyethylene matrices, replicating biological structural synergy. Compared to the unreinforced controls, BPC-CFMP-F exhibited a significant increase in peak impact force resistance by up to 108.7%, while maintaining superior structural integrity under various impact energies, as evidenced by significantly reduced damage areas and indentation depths. Remarkably, post-impact flexural strength surpassed pre-impact values of control specimens, indicating superior damage tolerance. Finite element simulations revealed stress distribution patterns and failure mechanisms aligning with experimental observations, validating the design rationale. This convergence of experimental and simulated data validates the effectiveness and our biomimetic design and its potential to revolutionize the application scope of NFPCs. By incorporating a rigid-flexible configuration inspired by natural resilience, we pave new avenues for enhancing traditional NFPCs, making them suitable for high-demand applications where enhanced load-bearing capacity and impact resistance are crucial, particularly in critical sectors such as automotive, rail transit, and marine engineering.