Experimental Investigation of an Active Sub-micron Acoustic Sensor Using Bandgap Materials

Abstract

Acoustic bandgap (ABG) crystals are made of a periodic array of inclusions/scatterers embedded in a homogenous material. ABG crystals can be thought of as the mechanical analogues of semiconductors. In a semiconductor the electronic bandgap arises as the result of a periodic array in electronic potentials. In an ABG crystal a sonic bandgap arises as the result of a periodic array of differing acoustic impedances. We suggest that acoustic bandgap crystals can be used as sensors to detect and quantify submicron damage in substrates by monitoring changes in their acoustic response. More interestingly, is the scalability of the proposed sensors as acoustic bandgaps can be observed in both low-audible frequencies (e.g. seismic waves) and terahertz frequencies (e.g. phonon waves). This article presents the ability of an ABG sensor made of an epoxy matrix loaded with Tungsten scatterers to detect and quantify submicron damage in composite material substrates adhered to the ABG sensor. A finite element simulation, coupled with acoustic wave analysis using finite difference in time domain, is used to present the ability of ABG crystals to be employed as submicron sensors.