The use of composite materials in the automotive industry has become increasingly widespread. With this increase in use, techniques for non-destructive testing (NDT) have become more and more important. Various optical NDT inspective methods such as holography, moiré techniques, and shearography have been used for material testing. Among these methods, shearography appears to be most practical. Shearography has a simple optical setup due to its “self-referencing” system, and it is relatively insensitive against rigid-body motions. Measurements of displacement derivatives, and thus strain directly, rather than the displacement itself is achieved through this method. Therefore shearography detects defects in objects by correlating anomalies of strain which are usually easier than correlating the anomalies of the displacement itself, as in holography.
To date shearography has shown potential as a NDT tool for identifying defects in small structures. Applications of this technique in automotive inspection and production have been difficult because a high-powered laser typically needs to be used, which limits its application due to cost, and employee safety. In this presentation, a portable self-contained digital shearographic system using multi-laser diodes for the illumination source will be described. This system demonstrates a way to measure both small and large-scale structures with an economical portable shearographic system. Its application for NDT of composite materials in automotive and aerospace industries will be presented.