HOLOGRAPHIC DETECTION OF DEFECTS IN COMPOSITES

Laser holographic interferometry is applied to the detection of impact -induced damage and marcels in graphite-epoxy composites. Real-time an d two-reference-beam interferometry are implemented while the specimen s are thermally strained. For small temperature increases irregular fr inge patterns are observed, indicative of deformation anomalies, and c onsequently, of the presence of defects. For the impacted specimens, c losed-shape fringes begin to form at the impacted areas, and the more damaged the specimen, the sooner their appearance and their extent. Fo r the specimen containing the marcels the fringes appear very wavy. In both cases pseudo three-dimensional images of the deformed surfaces a re obtained which provide a very clear picture of the effect of the de fect.