Application of the laser shearography in the non-destructive evaluation of the defects in the flat and curved surfaces made of carbon fiber composites

Laser shearing interferometry or Shearography is one of the new optic methods for calculating the very small surface displacement derivatives in order of microns. Shearography can be beneficially used in the non-destructive testing of materials, especially in composites. In this paper, laser shearography is used to detect some kinds of defects like cavities, solid inclusions and matrix cracks in both flat and curved furnaces made of carbon fiber reinforced composites. As the system parameters and loading amount are the most important factors affecting defect detection ability in this technique, the test scenarios including all these factors have been compiled for both flat and curved surfaces. The shearography tests are performed to get the best results of defect detectability in the test specimens. The results show that the best responses are observed with a shear size of one half the approximated defect sizes. The thermal loading range of 3kW and 1kW in the 0.5 and 1 seconds should be used as the best choices in the flat sheet and curved sheet specimens respectively.