Dramatic bandwidth enhancement in nonlinear metastructures via bistable attachments

Abstract

We report amplitude-dependent substantial enhancement of the frequency bandwidth in locally resonant metamaterial-based finite structures (metastructures) via bistable attachments. The bistable magnetoelastic beam attachments of the unit cells exhibit linear intrawell, nonlinear intrawell, and nonlinear interwell oscillations for low, moderate, and sufficiently high intensity excitations, respectively. As a result, the overall metastructure leverages linear locally resonant bandgaps under low amplitudes and nonlinear attenuation due to wideband chaotic vibrations of the bistable attachments under large amplitudes. The concept was first demonstrated through a linear mass-spring chain with bistable attachments in a numerical case study. Experimental results and validations are then presented for a base-excited cantilever beam hosting seven bistable unit cells. Transition from linear locally resonant bandgaps to nonlinear attenuation is observed, and the amplitude-dependent bandwidth enhancement is shown. The bandwidth offered by nonlinear interwell oscillations is substantially wider than the linear locally resonant bandgap that is limited by the added mass.