Impact behavior of negative stiffness honeycomb materials

Negative stiffness honeycombs are architected metamaterials that utilize elastic buckling to absorb mechanical energy. Relative to conventional honeycomb materials, they offer several advantages, including the ability to recover their initial configuration and offer consistently repeatable mechanical energy absorption. In this paper, fully recoverable negative stiffness honeycombs are fabricated from thermoplastic and metallic parent materials. The honeycombs are subjected to quasistatic and impact loading to demonstrate the predictability and repeatability of their energy absorption characteristics across a variety of loading conditions. Results indicate that these honeycombs offer nearly ideal shock isolation by thresholding the acceleration of an isolated mass at a predetermined level and that this thresholding behavior is highly repeatable as long as the magnitude of the mechanical energy imparted to the system does not exceed the energy absorption capacity of the honeycomb.