Evaluation of the defects in the underload polymers using shearography method by thermal excitation

Laser interferometry is one of the novel methods for performing nondestructive testing for composites and polymer materials. In this method, probable defects are investigated by measuring the very small surface displacement gradients. One of the major advantages of this method is the examination of a wide range of body surfaces simultaneously. Despite the major advantages of this method in performing non-destructive industrial tests, especially for composites and polymer materials, the implementation of this method requires identifying effective parameters and how to select and control them in order to achieve optimal results. Among the effective parameters in this method, the shear amount and loading value can be mentioned. In this paper, after introducing the principles of laser interferometry, the quantitative effect of these parameters on the detection of plate defects in polymer materials has been investigated. For this purpose, after examining the proper operation of the shearography system, samples of polymer with different size of plate defects are tested. By discussing the results, the appropriate load value and proper shear amount for determining the defects would be investigated. Investigations show that the best results are obtained when the shear amont is within the range of the defect size of the plate.