UC San Diego

Stress-wave propagation in solids can be controlled through imposing a gradual change of anisotropy in the material elasticity tensor. In this study, a transversely isotropic material is incorporated with a smoothly varying axis of anisotropy. It is shown that if this axis initially coincides with the stress wave vector, then the energy of the plane waves would closely follow this gradually changing material direction. A fiber-reinforced composite is used to induce the required anisotropy, and to experimentally demonstrate the management of stress- wave energy in a desired trajectory. The interface between two strongly anisotropic materials has a great influence on the stress wave scattering and can play a potential role in managing stress-waves in anisotropic and heterogeneous composites. Wave reflection and transmission at the interface of two elastic media has been thoroughly studied in the literature. In this study, we apply the theory of wave propagation to the interface of transversely isotropic materials, where the group velocity and wave-energy flow are usually close to the preferred direction of maximum stiffness. It is established that the anisotropy orientation of two interfacing materials can be exploited to control and manage stress wave energy by design; for example, the energy of an incident pressure wave can be guided to a desirable direction; the scattered longitudinal wave can be evanescent (non-propagating); and finally the energy content of stress-waves can be transferred from pressure into shear wave energy, which is prone to dissipation. Multilayered structures consisting of strongly anisotropic layers can be exploited to efficiently manage the stress wave propagation in solids by providing multiple interfaces that play key roles in transmission and reflection of pressure and shear waves. We have developed a computational platform to efficiently evaluate the transmitted and reflected stress-waves in pressure and shear modes based on the anisotropy orientation of layers and the incident wave vector direction. We demonstrate that a multilayered structure can be tailored to effectively transform the energy of incident pressure wave into shear wave energy. Furthermore, by integrating a layer of shear-dissipative material, the resulting shear-wave energy can be dissipated within the viscoelastic layer