Microstructural designs of plate-type elastic metamaterial and their potential applications: a review

Abstract

Elastic metamaterials are of growing interest due to their unique effective properties and wave manipulation abilities. Unlike phononic crystals based on the Bragg scattering mechanism, elastic metamaterials (EMMs) are based on the locally resonant (LR) mechanism and can fully control elastic waves at a subwavelength scale. Microstructural designs of EMMs in plate-like structures have attracted a great deal of attention. In this paper, the recent advances in the microstructural designs of LRbased EMM plates are reviewed. Their potential applications in the fields of low frequency guided wave attenuation, wave manipulation and energy trapping at a subwavelength scale, and structural health monitoring are discussed.Keywords: metamaterial; composite; structural dynamics; nondestructive evaluation; structural health monitoring IntroductionThe research on metamaterials has grasped a lot of attentions recently. With artificially designed microstructures, metamaterial has the ability to achieve bizarre but very useful dynamic material properties. Initially, the strangeness of metamaterial was discovered when researchers investigated its effective electromagnetic (EM) properties at certain frequency ranges where the EM metamaterial behaves as if it has negative permittivity [1] and/or negative permeability [2]. Later on, similar unnatural phenomena were found in acoustic metamaterials which have negative mass density (NMD) [3] and/or negative bulk modulus (NBM) [4]. Anisotropic mass density was also achieved in non-resonant acoustic metamaterials containing fluid components [5,6,7]. Unlike the essential similarity between the governing equations in EM metamaterials and those in acoustic metamaterials, applying the concept of metamaterial in solids is more complex [8]. This is mainly due to the inherent coupling between longitudinal and shear wave modes and wave mode conversion. However, driven by the curiosity as well as the promising applications in mechanical and aerospace engineering, researchers have become more and more interested in the abnormal effective material properties of elastic metamaterials (EMMs). Many EMM-based devices have been proposed for promising applications with elastic wave controls and manipulations such as: elastic wave flat-lens focusing [9], EMM waveguides [10], EMM cloaking [11], and sub-wavelength imaging [12].

Labyrinthine Acoustic Metamaterials with Space-Coiling Channels for Low-Frequency Sound Control

“…Hence, these modes do not represent standing localized waves, rather they are propagating waves with very small (and often negative) group velocities. They may be analogous to slow modes inside phononic band gaps for elastic waves [30,31]. The mechanism of the slow mode excitation in acoustics and their dynamics will be investigated in more detail in future work.…”

Dynamic Simulation of a Metamaterial Beam Consisting of Tunable Shape Memory Material Absorbers

“…Usually, the materials with a periodic distribution of elastic constant or mass density are known as phononic crystals. With analogy to photonic crystal, it is found that when an elastic wave propagates through phononic crystal or an elastic composite with a periodic structure, a similar stopband or bandgap is formed in its transmission [4][5][6].…”

Scattering of flexural waves from an N-beam resonator in a thin plate

“…The resulting periodic systems, composed of local resonators, are sometimes named as platonic [4] or elastic metamaterials. [17] In the range of working frequencies, the wavelength is much larger than the lattice constant, hence metamaterials are often characterized by frequency related effective parameters just like they were homogeneous. [15,18] Subsequently, various kinds of negative index metamaterials were proposed and designed by means of local resonance mechanism, which paves the way to some intriguing phenomena, like negative refraction and perfect lensing.…”

“…[19] For a comprehensive report, the reader is addressed to the review article by Zhu and coworkers. [17] This work presents an analytical formulation for the scattering of flexural waves from a single structured circular hole consisting of a circular plate that is connected to the background plate with N rectangular beams. These type of resonators, which are named as N -beam resonators, have been already employed to predict directional wave motion [24] and superlensing.…”