Abstract
Pentamode metamaterials have been receiving an increasing amount of interest due to their water-like properties. In this paper, a two-dimensional composite pentamode metamaterial of rectangular unit cell is proposed. The unit cells can be classified into two groups, one with uniform arms and the other with non-uniform arms. Phononic band structures of the unit cells were calculated to derive their properties. The unit cells can be pentamode metamaterials that permit acoustic wave travelling or have a total band gap that impedes acoustic wave propagation by varying the structures. The influences of geometric parameters and materials of the composed elements on the effective velocities and anisotropy were analyzed. The metamaterials can be used for acoustic wave control under water. Simulations of materials with different unit cells were conducted to verify the calculated properties of the unit cells. The research provides theoretical support for applications of the pentamode metamaterials.
Highlights
Acoustic metamaterials (AMs) [1] are rationally designed materials that can manipulate and control acoustic waves in ways that are impossible for conventional materials
The structures of the rectangular unit cell can be modified by breaking the identity the composed arms
The phononic band structures of some unit cells revealed that there exist pentamode bands where only compressional waves are supported
Summary
Acoustic metamaterials (AMs) [1] are rationally designed materials that can manipulate and control acoustic waves in ways that are impossible for conventional materials. The PMs with different unit cells [7,8,9], different cross-section shapes [10], asymmetric arms [11,12], composite materials [13,14,15], or structures [16,17] were studied for their improved properties. The unit cells were studied with different structure parameters for their effective properties and water-like characteristics [21,22,23]. PMs negative effective density [37] or negative effective bulk modulus [38] It can be have water-like properties that permit broadband propagation of acoustic waves without realized by embedding spherical cavities [39] or hard spheres [40] in soft medium.
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