Transient displacements of a composite medium with defects due to a surface pulse

This paper considers the transient dynamic response of a composite medium with arbitrary shaped voids. A boundary integral equation method is used to compute the displacement histories due to a loading pulse applied to the surface of a composite medium. The present methodology can also be used to study the response of a medium with near-surface cracks and elastic impurities. Numerical solutions are presented for graphite/epoxy, glass/epoxy and isotropic media. The influence of the degree of anisotropy of a medium, orientation and geometry of a void, time history of the loading pulse and the interaction between multiple voids are examined. It is found that the near-field displacements of a damaged medium differ substantially from an undamaged medium. The results reported here can be used for qualitative and quantitative nondestructive evaluations and also for computing the acoustic material signature of a composite medium with defects. The present results are also useful in the validation of inverse solution algorithms developed for material characterization.