Biomimetic cellular face-bridging fiber composites with exceptional strength and toughness

Fiber-reinforced polymer structures are widely used in applications requiring strong, lightweight materials, such as in aerospace and automotive industries. Despite their high stiffness and strength, these materials often suffer from brittle fracture and shaping difficulties. This contrasts with natural lightweight biomaterials, such as bone, bamboo, and wood, which possess complex hierarchical structures that contribute to exceptional mechanical properties through directed self-assembly. Inspired by the hierarchical structure of bamboo, we propose a cellular face-bridging fiber structure and introduce interface entanglement strategy to achieve lightweight, high strength, toughness and impact resistance of the composite material. The resulting composites exhibits a density of 0.87 g/cm³, a specific strength of approximately 200 MPa/(g/cm³), toughness of nearly 244 kJ/m³, and an ultimate tensile elongation surpassing engineering composites and polymers. It also demonstrates good resistance to high-speed ballistic impact, with specific impact energy absorption comparable to traditional impact-resistant materials, such as Kevlar reinforced composites. Multi-scale simulations and experimental analyses reveal that the cellular face-bridging fiber structure, with its physically entanglement interface, enhances strength, toughness, and energy dissipation through fiber breaking, pull-out, interface cracking, and matrix slippage. The composite's thermoplastic processability allows for the fabrication of centimeter-scale structural parts, indicating promising potential for scalable production in lightweight aerospace applications.