Nonlinear elastic metamaterials as pulse shaping devices for shock test applications

Metamaterials (MM) have become a very active research topic in numerous domains of engineering because of their promise to create structures and devices that can control wave propagation in ways that exceed the capabilities of conventional homogeneous and composite materials. Most research on acoustic and elastic MM has been focused on linear behavior. However, linear MM suffer from notable drawbacks, for example, (i) the effective material properties for the application of interest are often limited to narrow frequency bands, and (ii) they have limited usefulness in applications where nonlinearity is unavoidable or essential, e.g., shock testing or high-intensity focused ultrasound. Nonlinearity has therefore been explored to expand the palette of accessible dynamic response of synthetic materials. In this work, we investigate applications for nonlinear elastic MM as pulse shaping materials for shock testing. By using high-resolution finite element methods in concert with direct numerical simulations of reduced-order dynamic models, we examine the propagation of elastic pulses under the influence of various types of nonlinear elastic response and identify means to obtain them. These simulations demonstrate the potential for nonlinear elastic MM to significantly expand the space of accessible excitations for shock testing, using a relatively small number of design parameters.