Study of wave propagation through porous lattices with buckling instabilities in an aqueous environment

Abstract

Elastic lattices with cylindrical air-filled voids may undergo significant topology changes when deformed due to the buckling instabilities of the thin elastic ligaments between voids. Such phononic crystals are of interest to, for example, achieve auxetic behavior and create tunable stop bands that vary as a function of the deformation. Most studies reported in the literature by others focus on lattices made of soft elastomers, and the resulting nonlinear deformation or elastic wave propagation due to low-frequency vibrations in air. The current research focuses on transitioning these previously studied concepts on buckling lattices to an aqueous environment. Initial investigations presented here are for 3-D printed lattices comprised of rigid plastic and deformed by leveraging shape memory effects that result in softening and hardening of materials under heating and cooling, respectively. The use of rigid plastic addresses inherent difficulties that arise with soft elastomers, including high loss, fabrication at scales of interest, and appropriate frequency range for wave propagation. The present work focuses on numerical simulations and experimental measurements of wave propagation through finite, plastic lattices with air-filled voids in water. [Work Supported by the Office of Naval Research.]