Bioinspired stiff–soft gradient network structure for high-performance impact-resistant elastomers

Traditional impact-resistance materials relying on the combination of supporting materials and energy-dissipation elastomers can effectively reduce shock load, yet the sharp interface between two types of materials causes discontinuous stress transfer and cracking. Here, inspired by the squid beak, we report a type of high impact-resistance gradient elastomers with large-scale modulus gradient with about three orders of magnitude (modulus range of 7 × 10 3 ∼ 7 × 10 6 Pa) and high energy dissipation (loss factor > 0.6) over a wide temperature range by diffusively introducing stiff polymers in a highly damping elastomer with controlled mechanical properties. Under the action of an external force, our gradient elastomers exhibit soft-while-stiff attributes, combining cushioning and support. In drop hammer impact tests, our gradient materials can reduce impact strength by 80 %, significantly better than commercial protective gear. It is worth mentioning that the modulus of the bottom layer matches that of the tissues for better protection.