Abstract
We report a new class of tunable and switchable acoustic metamaterials comprising resonating units dispersed into an elastic matrix. Each resonator consists of a metallic core connected to the elastomeric matrix through elastic beams, whose buckling is intentionally exploited as a novel and effective approach to control the propagation of elastic waves. We first use numerical analysis to show the evolution of the locally resonant band gap, fully accounting for the effect of nonlinear pre-deformation. Then, we experimentally measure the transmission of vibrations as a function of the applied loading in a finite-size sample and find excellent agreement with our numerical predictions. The proposed concept expands the ability of existing acoustic metamaterials by enabling tunability over a wide range of frequencies. Furthermore, we demonstrate that in our system the deformation can be exploited to turn on or off the band gap, opening avenues for the design of adaptive switches.
Highlights
Each resonator consists of a metallic core connected to the elastomeric matrix through elastic beams, whose buckling is intentionally exploited as a novel and effective approach to control the propagation of elastic waves
Band gaps are generated by Bragg scattering [12], whereas in acoustic metamaterials, localized resonance within the medium is exploited to attenuate the propagation of waves
To fully understand the effect of deformation on the propagation of small amplitude elastic waves in the proposed acoustic metamaterial, we focus on the elastic system shown in Fig. 1
Summary
Pai, Filippo Casadei, Sicong Shan, James C. Effect of the applied deformation on the band structure: Dispersion relations from Bloch-wave analysis for the infinite metamaterial in (a) the undeformed configuration and under uniaxial compressive strain (c) ε 1⁄4 −0.065 and (e) ε 1⁄4 −0.10. We demonstrated both numerically and experimentally that large deformation and local instability can be exploited to effectively control the response of locally resonant acoustic metamaterials This remarkable behavior is achieved by introducing a structural coating comprising an array of elastic and highly deformable beams. Our results indicate that under externally applied load the stiffness of the beams varies significantly due to their buckling, altering the resonant frequency of the unit and providing a wide range of tunability for the band gap (∼30% in frequency).
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