Non-destructive Inspection of Subsurface Cracks in Carbon-fiber and Glass-fiber Reinforced Polymeric Materials Using Digital Shearography Method

Digital Shearography is one of the new methods of non-destructive testing based on the laser beam which is used to measure the surface displacement derivatives. In this method, relying on the interference of two laser waves reflected from the object surface, the displacement gradient of the deformed sample can be measured directly. So that it is possible to evaluate the industrial parts in a non-contact and full-field way with a high speed and accuracy. One of the significant advantages of this method is the ability to detect subsurface defects in various materials, including composites. In this paper, samples with subsurface cracks made of composite materials reinforced with glass fibers and carbon fibers have been inspected by Digital Shearography testing. Also, the optimal values ​​of each main parameter such as shear distance and loading size for each material have been obtained using the Taguchi experiment design. The results show that for each type of material there is an optimal amount of loading amount and shear distance, which if applied, the best test results are obtained.