Tunable reflection and broadband absorption of flexural waves by adaptive elastic metasurface with piezoelectric shunting circuits

Elastic metasurfaces have attracted lots of attention due to their extraordinary ability in manipulating elastic waves. Among various elastic metasurfaces, the adaptive elastic metasurface (AEM) has more flexibility because of the tunability in function and working frequency band without changing the geometrical configuration. In this paper, we propose an AEM composed of sandwiched plates with mass blocks at their free ends to realize tunable reflection and high-efficiency absorption of flexural waves in broadband. The upper and lower parts of the sandwiched plate are piezoelectric patches individually shunted with a hybrid circuit in series of a resistance and negative capacitance. We solve the reflection coefficient/phase shift of the subunit and the full reflected wave field of the AEM by using the transfer matrix method and coupled-mode theory, respectively. The modulation mechanisms of the phase shift and reflection coefficient are revealed. Especially, the influence of negative effective rigidity on the phase shift is investigated. The moment of inertia generated by the mass block plays a key role in reducing the sensitivity of the phase shift to negative capacitance. Based on the theoretical analyses, the AEMs are designed to realize tunable reflection, switchable asymmetric reflection and high-efficiency absorption. The results obtained from analytical solutions and finite element simulations are consistent with each other. The proposed AEM may have potential applications in vibration control and noise reduction.