Application of holographic interferometry in the detection of flaws in composite plates

Abstract

The use of holographic interferometry in the detection of sub-surface flaws in structural components offers certain advantages, including the ability to obtain full-field inspection without the necessity for physical contact. However, the resulting fringe patterns obtained must be carefully analyzed in order to derive meaningful interpretations. In this paper, the technique of holographic interferometry was applied to the assessment of defects in glass fibre-reinforced composite and aluminum plates. Circular plate specimens were clamped along the boundaries and an incremental pressure was applied between two exposures to obtain holograms. The defects, in the form of locally thinned regions, cause perturbations in the fringe patterns. Analysis of the experimental fringe patterns was compared with predictions from finite element and analytical models. The results show good agreement, implying that it is possible to both qualitatively and quantitatively assess the severity and extent of flaws in composite plates.