Underwater cylindrical sandwich meta-structures composed of graded semi re-entrant zero Poisson's ratio metamaterials with pre-strained wave propagation properties
Qing Li, Zeping Wang, Xiang Mao, Deqing Yang
Abstract
Zero Poisson's ratio (ZPR) mechanical metamaterials can yield no transverse displacements when unidirectionally compressed, and cylindrical sandwich meta-structures composed of semi re-entrant (SRE) ZPR metamaterials are thus explored for applications on cylindrical shells of underwater equipment or submersible structures. A group of ZPR unit cells with specified pre-strained wave propagation characteristics and adequate load-bearing capabilities is optimally designed based on the periodic boundary condition (PBC) and Bloch's Theorem. The sound transmission and pressure-resistant performance of cylindrical sandwich meta-structures comprising the homogeneous and graded SRE ZPR unit cells are then investigated. The results show that the designed meta-structures can perfectly yield better vibroacoustic attenuation behavior within the specified frequency regions corresponding to the pre-strained band gaps and safely bear the hydrostatic pressure equivalent to 1000 m depth with low weight-bulk ratios. In addition, the functionally graded metamaterial core can boost vibroacoustic performance within broader frequency ranges.