Instability induced control of wave propagation in structured composites

The microstructure of a composite material has an essential infl uence on its effective properties, and it can be used to regulate mechanical, chemical, acoustic, adhesive, thermal, electrical, and optical functions of the material. This research focused on purposely deploying the mechanics of instabilities to achieve sudden pattern transformations in the microstructure of a composite, and study the effect of the instability transformation on the overall structural response. Various networked and 3D-structured composites consisting of stiffer plates submerged in a soft elastomeric matrix were studied. Compressing the composites beyond a critical strain led to complex instability and wrinkling patterns in the initially straight plates. The motivation of our study is to elaborate the formation of a system of prescribed periodic scatterers (metamaterials) due to instability, and their effect to interfere wave propagation through the metamaterial structures. Such metamaterials made from elastomers enable large reversible deformation and, as a result, signifi cant changes of the wave propagation properties. Analytical models and numerical simulations were developed to capture various aspects of the instability mechanism and the wave propagation properties. Mechanical experiments were designed to further explore the modeling results. The ability to transform the microstructure in the networked and 3D-structured composite materials can enable switchable and tuneable control of wave propagation to create both band-gaps and waveguides.