Metamaterial Beams with Negative Stiffness Absorbers and Rotation: Band-Gap Behavior and Band-Gap Merging

Two novel configurations of metamaterial beams, i.e., a monatomic and a diatomic one, are proposed in this paper through a proper combination of negative stiffness absorbers (NSAs) and rotation of flexural beams amplified by outriggers. The advantage of using the rotation rather than transversal deformation of the host beam in achieving low-frequency band gap is recognized. Then, the behavior of the rotational unit cell with NSAs are systematically investigated by concerning the influences of parameters including the negative stiffness ratio, the outrigger length, and the damping ratio. Moreover, the damping magnification effect of NSAs provides substantial damping ratios for the passband. In this way, a wider band gap can be achieved through the band-gap merging effect for the proposed diatomic configuration, where the passband between the two band gaps is capable of mitigating the waves owing to the damping magnification effect of NSAs.