Broadening band gaps in an electromechanical metamaterial rod by resonant electromagnetic shunt and inter-resonator coupling

Band gaps that lead to attenuation of vibration propagation characterize locally resonant metamaterials. However, the band gaps rely on heavy resonators. In this work, we propose an electromechanical metamaterial rod that consists of an elastic rod with periodically attached electromagnetic resonators each composed of a cantilever beam and a magnetic. The magnets of multiple resonators are shunted by a resonant circuit and the stiffness of these resonators can be different. The attenuation constant surface (ACS) plots show that for unit cells of different mechanical resonators and unit cells of identical electromagnetic resonators, multiple band gap coupling phenomena can occur due to multiple local-resonance band gaps and the Bragg-type band gap coalescing, thereby forming a unified band gap much wider than a local-resonance band gap. Furthermore, the transmittance of the finite rod shows that several narrow pass bands can occur due to the slow convergence to the infinite rod. It also shows that the presence of electrical resistance suppresses the narrow pass bands. Consequently, the proposed metamaterial rod can achieve attenuation of vibration propagation in a broader frequency range than conventional metamaterial rods consisting of identical resonators.