Monday, October 13, 2014 3:00 p.m. ECJ 1.202
Dr. Michael R. Haberman
Applied Research Laboratories and
Department of Mechanical Engineering
The University of Texas at Austin
Acoustic metamaterials (AMM) are material systems whose overall performance originates from engineered sub-wavelength structure rather than the inherent material properties of their constituents. This relatively new topic in applied physics has garnered attention in the scientific community because of the potential role in realizing exotic behavior such as acoustic cloaking, negative refraction, and one-way sound transmission. This talk discusses a new AMM that was designed to amplify acoustic absorption and nonlinearity for potential use in new acoustical devices and vibro-acoustic coating materials. The AMM consists of a nearly incompressible viscoelastic matrix material containing a low volume fraction of sub-wavelength metamaterial structures (inclusions) that possess a non-monotonic stress-strain response. A nonlinear multiscale material model is presented that captures the strain-dependent evolution of the stiffness of the homogenized medium. That material model is then used to determine the effective quadratic and cubic parameters of nonlinearity of the AMM. Those parameters of nonlinearity are compared with those of conventional materials and examples of one-dimensional wave distortion effects are provided. The forced nonlinear multiscale dynamics in the AMM is then explored using a modified Rayleigh-Plesset model to highlight the influence of pre-stress and inclusion-scale dynamics on macroscopic energy absorbing capabilities for this AMM.