Low-frequency broadband absorption of underwater composite anechoic coating with periodic subwavelength arrays of shunted piezoelectric patches

This paper proposes an underwater semi-active composite anechoic coating with periodic subwavelength piezoelectric arrays to broaden the low-frequency absorption bandwidth and improve the absorption coefficient. Based on the effective medium method, the dual equivalent properties for the volume density and Young's modulus of the equivalent thin-plate interlayer are computed. Then, a complete two-dimensional theoretical model for oblique incidence is established by combining the shunt damping technique and wave propagation theory in layered media. On the premise of strictly satisfying the two preconditions of subwavelength assumption and stratified convergence criteria, the correctness and effectiveness of the present model are confirmed by successively according to the finite element simulation results, experimental data, and theoretical predictions. At last, change regulations of seven critical parameters on the sound absorption characteristics of the present coating are investigated to reveal the multiple energy dissipation mechanisms of the overburden in the whole research frequency band.