Application of shearography in nondestructive testing of composite plates

Abstract

Shearography is an interferometric method which provides a whole-field observation of isoclines which are related to surface strains. Since defects in structures such as cracks and delamination induce strain concentrations when the structures are loaded, shearography reveals defects from anomalies in the interferometric fringes. This paper illustrates the use of shearography for estimating the size and depth of disbonds in glassfibre reinforced plastic plates. Square flaws of known sizes are deliberately created within the plates and the "vacuum stressing" method is used to load the defective plates. Results show that disbonds in the plates can be easily sized from the boundaries of the anomalous fringe patterns, and their depths can also be estimated from the number of fringes which appear within the defective areas. © 1990.