New low-frequency broadband metamaterials based on inerter and novel large-linear negative stiffness mechanism

Elastic metamaterials are recently emerging structural-functional materials, which provide a new way for the control of elastic waves. However, the current low-frequency broadband performance is yet to be further improved. Herein, a novel large-linear negative stiffness mechanism is first proposed, which is capable of generating constant negative stiffness; the influences of the relevant structural parameters are discussed, and a design method for this mechanism is also given. Subsequently, a new type of elastic metamaterial is designed by combining the inerter and the proposed negative stiffness mechanism; a parametric programming method with general characteristics is proposed to guide the selection of unit-cell parameters, and it is revealed that only at most one negative stiffness spring is allowed to exist in the system. Finally, the low-frequency broadband characteristics of the metamaterial are investigated. It is found that the proposed metamaterial can produce a basin-like attenuation band, i.e., the attenuation curve at the bottom of the attenuation band is a stable flat line; in a given frequency range, the introduction of negative stiffness can further increase the attenuation strength of the metamaterial basin-like band.