Inverse design of NiTi alloy-based chiral metamaterials with multi-level rotational capabilities for reusable high-performance impact absorption

High-performance impact-absorbing structures that combine exceptional energy absorption capabilities with high reusability represent a significant advancement in protective engineering. In this work, we present the development of three-dimensional (3D) chiral metamaterials and a sophisticated inverse design methodology specifically engineered to achieve tailored impact-absorbing properties. By harnessing the multi-level rotational mechanisms—encompassing localized and global beam rotations, as well as the overall structural rotation—during compression, coupled with the shape memory effect of nickel-titanium (NiTi) alloy, the designed structures demonstrate outstanding reusability in energy absorption. Utilizing the AI-driven approach that integrates machine learning with genetic algorithms, we successfully engineered six distinct structures with plateau stresses ranging from 0.025 MPa to 0.7 MPa. Uniaxial compression tests revealed excellent alignment with finite element analysis (FEA) predictions, exhibiting an average deviation of only 8.75 % from the target stress–strain profiles, thereby validating the robustness and precision of our inverse design methodology. Notably, the structure with a plateau stress of 0.05 MPa achieved an exceptional shape recovery ratio of 97.9 % following 80 % effective compression, underscoring its superior reusability. These findings underscore the transformative potential of 3D chiral metamaterials with multi-level rotational capabilities and their inverse design strategy in advancing the development of reusable, high-performance impact-absorbing structures.