Bio-inspired interface-structure synergy unlocking synchronized helicoidal toughening in stiffness-mismatched hybrid materials

Carbon fiber reinforced polymers (CFRPs) are indispensable to aerospace and marine structures owing to their exceptional specific strength and stiffness. However, their intrinsic brittleness facilitates catastrophic crack propagation and sudden loss of structural integrity. In response, fiber architectural toughening and fiber-metal hybridization have been widely explored to enhance the damage tolerance of CFRP-based structures. However, the synergistic potential of combining these two routes is often severely compromised by premature interfacial failure in stiffness-mismatched systems. To unlock this synergy, we propose a bio-inspired interface-structure synergy (BISS) strategy to activate bio-inspired architectural toughening in stiffness-mismatched Al-CFRP hybrid materials. A helicoidal Bouligand fiber architecture is integrated with a biomimetic, laser-patterned aluminum interface. The resulting interfacial stabilization ensures efficient load transfer, thereby triggering helicoidal crack twisting and promoting plastic energy dissipation in the metallic phase. The BISS-enabled interface enhances interfacial peel strength by 658%, effectively suppressing interface-dominated failure and fully activating the characteristic crack-twisting mechanism of the Bouligand architecture. Consequently, the hybrid system achieves a 44.87% higher energy absorption rate and a 76.56% improvement in damage resistance compared with quasi-isotropic CFRP. Even when compared to standalone Bouligand-based hybrid configurations, the BISS strategy delivers a further 9.66% increase in energy absorption ratio. In addition, CAI tests reveal more than 17% higher residual strength retention, further highlighting the critical role of interfacial enhancement in enabling helicoidal toughening mechanisms. This work provides a new design paradigm for developing damage-tolerant fiber-reinforced hybrid systems through bio-inspired interface-structure integration.