Recently, acoustic metamaterials with periodic microstructures (referred as phononic crystals) have attracted considerable attention due to their remarkable properties – such as negative elastic moduli, mass density, and refractive index – stemming from their microstructures. Moreover, the ability of soft metamaterials to sustain large deformations opens rich possibilities for manipulating acoustic characteristics by deformation. Hence, elastic waves can be tuned by constructing microstructures, which can be further actively controlled by external stimuli, e.g., by mechanical loading, magnetic or electric fields.
In this talk, we will start with the discussion of the acoustic properties of the relatively simple homogeneous hyperelastic materials, and then we will turn to the materials with periodic microstructures. First, we will explore the influence of the deformation induced stiffening on the propagation of small-amplitude elastic plane waves. Second, we will show that electroactive homogeneous materials can be utilized to achieve acoustic functionalities such as disentangling of pressure and shear waves by application of an electric field. Next, we will proceed with the analysis of wave propagation in highly deformable layered materials. In particular, we will present the long wave estimates of the phase and group velocities for the waves propagating in finitely deformed layered media. Moreover, we will introduce the material compositions and loading conditions producing wide complete band gaps (i.e. frequency ranges where neither pressure nor shear waves cannot propagate) at low frequency ranges. Finally, we will discuss the anisotropy of elastic wave propagation in finitely deformed fiber-reinforced composites.