<p>Metamaterials are periodic structures with locally resonating substructures which can control and manipulate wave propagation at the subwavelength scale. On the other hand, phononic crystals (PC) consist of mass/modulus-modulated lattices that are on the order of the wavelength. Both metamaterials and PCs exhibit band gaps (i.e. forbidden waves) featuring from the locally resonating elements and Bragg-scattering, respectively. Their band gap property has been especially exploited for attenuation of elastic/acoustic waves. With the advances in this emerging field, piezoelectric metamaterials and metastructures have gained an increasing research interest due to their potential to control waves without any need for structural modifications and also due to their multifunctional abilities, such as energy harvesting and vibration mitigation. For instance, embedding periodic arrays of piezoelectric patches in elastic waveguides has been proven to be useful for tuning dispersive behavior of the waveguide via external electrical load on the piezoelectric array. For example, researchers studied piezoelectric metamaterials for reconfiguring the wave directivity, tuning the gradient-index lenses and metasurfaces, and controlling band gap mechanism over a wide frequency range for vibration absorption. On the other hand, utilizing the direct piezoelectric effect, multifunctional metamaterials have been enabled. In an effort for broadband harvesting of the low frequency vibration energy, researchers explored piezoelectric patch arrays with heavy masses based on the PC concept and local resonators in the form of piezoelectric cantilever harvesters with tip mass attachment for energy conversion of standing waves. In this paper, our goal is to introduce an electromechanical metastructure (EMM) for harvesting energy from traveling elastic waves and exploit the properties of locally-resonant metamaterials and phononic crystals within the same structure. Specifically, we exploit both locally-resonant and Bragg band gaps to achieve a multifunctional metastructure which is capable for maximum energy conversion and vibration mitigation in a broadband fashion. To this end, we present a new wave-based theoretical framework (i.e., fully coupled electroelastic transfer matrix method) and study the multifunctional harvesting and vibration mitigation performance of the proposed EMM.&nbsp; Our analytical and numerical results show that the proposed metastructure can achieve energy harvesting efficiency up to 95% at the local resonance frequency of 3.18 kHz, while reaching 51% at 5.8 kHz near the upper limit of the Bragg band gap. The broadband vibration mitigation performance based on 50% power attenuation is predicted as 1.8 kHz and 1.1 kHz in the vicinity of the band gaps. The theoretical frameworks and the applicability of the proposed metastructure are also validated using a full-scale experimental setup.</p>

Multifunctional Electromechanical Metastructures for Energy Harvesting and Vibration Mitigation

Paper Proceedings: https://asmedigitalcollection.asme.org/SMASIS/SMASIS2021/volume/85499

ASME 2021 Smart Materials, Adaptive Structures and Intelligent Systems (SMASIS2021)

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