Quasi-All-Directional Negative Stiffness Metamaterials Based on Negative Rotation Stiffness Elements

Most negative stiffness metamaterials exhibit negative stiffness effects in only one direction. Herein, based on the theory of anisotropy, the concept of “negative stiffness” is redefined. A method to determine whether a material has all-directional negative stiffness is proposed. The possibility and difficulty of achieving all-directional negative stiffness are discussed. A new type of negative stiffness metamaterial comprising negative stiffness rotation hinges and rigid trusses is studied. The results show that quasi-all-directional negative stiffness is achievable.