Macro-Scale Geometric Voids to Alter Stress Wave Propagation in Solids

Abstract Structural discontinuities, such as voids or inclusions in otherwise uniform, solid materials have previously been successfully implemented to alter the propagation of various types of waves through a range of materials and structures. Much of this work has focused on micro-scale features and low energy waves. The disruption of waves carrying larger amounts of energy currently relies mainly on large material deformation, typically with a layer of the structure becoming permanently damaged in order to protect other portions. However, the ability to disrupt, alter, direct, and control higher energy waves without significant damage to the material or structure can be desirable. Microscale features can disperse wave fronts, scattering their energy and reducing the potentially damaging effects of the concentrated loads carried in these waves. However, the control of the distribution of these microscale features throughout the material and structure can be difficult, limiting the ability to use these materials to control the dispersion of the wave energy or direct it to more desirable regions in the structure. Macro-scale features can be more easily formed into patterns and arrangements which can be designed for specific wave-controlling or directing properties. Additionally, materials and structures with macro-scale discontinuities can result in a greater change in energy per inclusion and a greater spatial range of their effects throughout the domain of the material. Therefore, they have the potential to be used to address input waves of higher energy. The use of macro-scale features may provide added manufacturing-based benefits, particularly with the more widespread development and use of advanced manufacturing methods, such as additive manufacturing. This study examines the feasibility of the use of arrays of macro-scale features to direct and control input stress waves. The effect of the shape and arrangement of macro-scale geometric features is studied under a range of orders of magnitudes of the incident stress wave. Methods are developed in this work to predict the propagation of the stress waves through the material and to quantitatively assess the effects of these included arrays of structural, geometric discontinuities. The results of this study are used to evaluate the feasibility of the use of these geometric macro-scale arrays to control the propagation of stress waves in structures while limiting gross material deformation and damage to the overall structure.