Dissipative elastic metamaterials for broadband wave mitigation at subwavelength scale

In this paper, an elastic metamaterial with multiple dissipative resonators is presented for broadband wave mitigation by properly utilizing interactions from resonant motions and viscoelastic effects of the constitutive material. The working mechanism of the metamaterial to suppress broadband waves is clearly revealed in a dissipative mass-in-mass lattice system through both negative effective mass density and effective metadamping coefficient. Based on the novel metadamping mechanism, a microstructure design of the dissipative metamaterial made of multi-layered viscoelastic continuum media is first proposed for efficient attenuation of a transient blast wave. It is found that the extremely broadband waves can be almost completely mitigated with metamaterials at subwavelength scale. The results of the study could be used in developing new multifunctional composite materials to suppress the shock or blast waves which may cause severe local damage to engineering structures. Metamaterials are engineered structural materials that possess unique dynamic effective properties, not commonly found in nature. In recent years, a great deal of theoretical, numerical and experimental research has been conducted on electromagnetic metamaterials with novel applications such as electromagnetic absorbers, negative refractive indices, cloaking and superlensing [1–3]. Because of the analogy between electromagnetic waves and acoustic waves, acoustic metamaterials hold the potential to perform similar novel functions with acoustic waves as those found in electromagnetic metamaterials [4–9]. The key idea and principal component in microstructure design of acoustic metama-terials is to introduce subwavelength locally resonant inclusions, or, resonators. Due to the subwavelength feature, acoustic meta-materials can be modeled as effective continuum media with frequency dependent effective mass densities and/or bulk moduli. The realm of elastic metamaterial research is a relatively new field that also presents exciting and novel applications related to manipulation of elastic (longitudinal and transverse) waves and plate guided waves. The label Elastic MetaMaterials (EMMs) refers to a class of periodic structural materials, consisting of a solid-phase host and arrays of internal resonators, which are capable of affecting the propagation of elastic waves. For most configurations , the resonators typically consist of structural elements with highly contrasting elastic properties. For example, the very first EMM archetype was realized by embedding rubber-coated lead spheres in an epoxy matrix to capture dipolar resonances [10]; an anomalous bandgap (400–600 Hz) was observed with this architecture even for small spherical inclusions (5 mm radius) at subwavelength scale. By using a mass-in-mass lattice system to represent an EMM, it was found that the negative effective …