Utility of subsurface longitudinal waves in composite material characterization

Abstract

All sorts of different wave modes can be considered in both composite material inspection and characterization. Commonly accepted techniques include bulk longitudinal and transverse waves in normal and oblique incidence, and such guided waves as plate or surface waves. Unfortunately a combination of all of these possibilities for use in establishing a one sided ultrasonic technique for complete material characterization for certain levels of anisotropy is limited. In this paper the use of subsurface longitudinal waves (SSL), which can be effectively generated at the first critical angle, was explored. The SSL waves used here can be applied to material characteristic analysis to determine certain elastic constants and also for inspection of subsurface defects. Emphasis is placed on the material characterization problem. Experimental and analytical details are included in the paper on a sample problem of graphite epoxy.