UC San Diego

Over the past decades, metamaterials—whose engineered internal architecture grants unusual or extraordinary macroscopic response—have garnered increasing attention from researchers as the desire to shape material behavior beyond natural limitations (e.g., chemistry) arises within several areas of materials science and engineering. The bulk of reported acoustic metamaterial architectures are passive such that their properties and functions are fixed at fabrication. Nevertheless, a tuning capacity is desirable to expand the range of response, in general, and to allow for adaptation in the face of changing service requirements. Despite the diversity of proposed tuning strategies, most target the stiffness parameter alone, leaving the inertial and dissipative properties unaffected. In this presentation, we present a novel implementation of (geometric) bi-stability and kinematic amplification to independently tune the value and distribution of the effective mass, stiffness, and viscous damping within acoustic metamaterials, which impacts the dynamic response. Through analytical and numerical investigations of a 1D system, we show that the corresponding frequency band structure depends on the specific configurations of bi-stable elements within the unit cell. As the number of bi-stable elements per unit cell increases, so to do the number of unique dynamic responses to which to tailor the system. The proposed strategy significantly expands the property set available for tuning acoustic metamaterial performance post-fabrication.