Enhanced impact protection performance of mechanical metamaterials via multistable properties

Mechanical metamaterials offer a promising strategy for impact protection. Leveraging elastic deformation, multistable structures can reversibly store impact energy and mitigate damage. Here, we exploit the programmable multistability of negative-stiffness structures to tailor local stiffness, thereby promoting energy scattering and reflection and substantially enhancing protective performance. Theoretical analysis and large-scale simulations identify optimal configurations that maximize impact energy dissipation through reflection and scattering. This work provides the first systematic demonstration of employing programmable multistability in mechanical metamaterials to suppress impact wave energy, offering new design principles for advanced protective structures. It is worth emphasizing that although exemplified with curved-beam units, the findings are broadly applicable to other multistable structures.