The mechanical and acoustic properties of two-dimensional pentamode metamaterials with different structural parameters

Abstract

The effective mechanical and acoustic properties of two-dimensional pentamode metamaterials (PMs) with different structural parameters are investigated in this paper. It is found that with varying structural parameters, the effective bulk modulus and density remain constant as the same as those of water, while the figure of merit, i.e., the ratio of the bulk modulus to the shear modulus (B/G) gradually increases due to the decrease of the shear modulus. However, full wave simulations reveal that with the increase of B/G, the acoustic scattering becomes more and more intense, which indicates that the acoustic properties of pentamode metamaterials gradually deviate from those of water. These anomalous acoustic behaviors are proposed to arise from the existence of the bending modes in pentamode microstructures. Our results show that for pentamode metamaterials, the mechanical properties cannot be simply translated to their acoustic properties, and the structural parameters affect the mechanical and acoustic properties in much different ways.

Intertwined microlattices greatly enhance the performance of mechanical metamaterials

“…Mechanical metamaterials may exhibit unique properties, such as ultralight weight, high stiffness approaching the theoretical limit, and increased strength [5][6][7][8][9]. In addition, material structures showing unconventional properties, such as negative Poisson's ratio [10,11], negative thermal expansion coefficient [12], and bulk modulus tailored independently of the mass density [13,14], have been designed to control wave propagation through materials, create bandgaps, and induce certain deformation behaviors, such as pure torsional deformation [15]. Various designs have also been proposed to control the deformation of structures [16][17][18][19] and to develop functional shock absorbers [20,21] and actuators [22,23].…”

Broadband focusing of underwater sound using a transparent pentamode lens

“…Although bending modes exist at low frequency range, they do not cause much scattering due to sufficient shear modulus which prevents the structure from flexure. [31] We expect the lens to be capable of focusing underwater sound over a broadband from 10 kHz to 40 kHz.…”

Feasibility Analysis of Dispersion Curves in Calculating Equivalent Parameters of Honeycomb Pentamode Metamaterials

“…At present, a lot of research has been done on the theoretical calculation of honeycomb material equivalent parameters [7][8][9]. However, in order to achieve the application effect of strong anisotropy of pentamode materials, it is often necessary to improve the anisotropy of honeycomb materials [10,11], which increases the difficulty of calculating the theoretical equivalent parameters. Dispersion curves calculate the equivalent parameters by directly extracting the phase velocity, neglecting the complexity of the internal structure of the material,.If dispersion curves can be used to calculate the equivalent parameters of two-dimensional honeycomb materials, it will facilitate the design of two-dimensional five-mode materials based on cellular materials.…”