Reusable metamaterial via inelastic instability for energy absorption

This study investigated negative stiffness (NS) structures, which are promising metamaterials that can potentially be useful in the energy absorption field. However, low specific energy absorption restricts their implementation in engineering applications. In this paper, a reusable metal structure is proposed. This structure can dissipate energy through plastic deformation and exhibits NS behavior through inelastic instability. Its mechanical properties were investigated by conducting compression tests and simulations. The influence of the geometric parameters on energy absorption was revealed using an experimentally verified numerical model. The repeatability of the structure was investigated through cyclic compression, and the impact of the structural dimensions on repeatability was preliminarily investigated. Moreover, annealing treatment was conducted to improve repeatability. Based on the interlocking assembly method, a 3D NS structure is proposed and fabricated. The results obtained by this study reveal that the specific energy absorption of the proposed structure is larger than that of most traditional NS structures, and its energy absorption efficiency is high. Additionally, the structure is highly repeatable but its repeatability declines as its dimensions increase. Although repeatability can be substantially improved with annealing treatment, the mechanical performance deteriorates.