Synergistic enhancement of strength and toughness through meta-biomimetic design: Integrating crossed-lamellar and bouligand microstructures

The development of fiber-reinforced polymer (FRP) composites, striking a balance between high strength and toughness, is a pressing requirement for the contemporary aerospace industry. Regarding the design of microstructures for enhancing strength and toughness, bionic crossed-lamellar and bouligand structures serve as noteworthy examples. However, individual biomimetic microstructures have approached the upper limit of their strengthening and toughening effects. This paper firstly proposed a "Meta-Biomimetic" design concept: hybridizing biological microstructures with defensive functionalities and those with offensive functionalities in mechanical design, aiming to achieve a metamaterial with both offensive and defensive capabilities. Namely this work retains the three-layer cross-lamellar microstructure of conch shells to stimulate subcritical damage for enhanced energy dissipation, while introducing a bouligand microstructure of lobster homarus americanus to increase the high load-bearing capacity at both tension and compression ends. The optimal design for enhancing the strength and toughness is the three-layer crossed-lamellar microstructure modified with a full bouligand structure, which increases strength and toughness simultaneously by more than 500% compared to natural structures. These studies are poised to not only steer the design of FRP microstructures towards enhanced strength and toughness but also furnish a foundation for interdisciplinary research in biomimetics within composite materials.