Dumbbell-shaped chiral metamaterials for multi-polarized broadband vibration suppression

Abstract

Three-dimensional (3D) mechanical metamaterials provide new insights into broadband vibration suppression. However, their conventional design strategies typically extend two-dimensional (2D) counterparts onto the central region or surfaces of a hexahedral framework to attenuate multi-polarized vibration. This approach yields a wide bandgap. However, it results in very large structural volume and mass. To solve this problem, this study introduces a novel dumbbell-shaped chiral mechanical metamaterial (DCM), which combines a 2D planar frame with dumbbell-shaped resonators. The proposed DCM leverages the inertial amplification effect to perform lightweight vibration suppression, while simultaneously generating an ultra-broad bandgap-12 times wider than that of conventional chiral metamaterial (CCM)-by coupling in-plane resonance with compressive-torsional motions. Furthermore, its twisted variant, TDCM, can perform multi-polarized broadband vibration suppression comparable with that of 3D metamaterials. A dynamic equivalent mass model (DEM) and a 3D equivalent spectral element model (ESEM) are then developed to accurately predict the bandgap range and vibration responses. Afterwards, the vibration attenuation mechanism is analyzed in terms of the spatial distribution of energy in the frequency domain. The obtained results show high consistency with theoretical predictions.