Evaluation of sub-surface cracks in polymer matrix composites with laser interferometric method

Digital shearography is an optical method based on LASER interferometry can be used to determine the displacement gradients of surface of materials. This approach can be used as a tool for non-destructive testing. In this research¡ a method based on digital shearography is provided to estimate the depth and length of sub-surface cracks in glass-epoxy composite plates. Hence¡ the digital shearography of the studied specimen was simulated by Abaqus finite element software and a secondary program written in Matlab; A shearography setup established in order to verify the simulation. Comparing results of simulations to experiments confirmed the accuracy of simulations. Then¡ by design of experiment method¡ shearography of studied specimen with different crack geometry and testing load was simulated and number and density of fringes were extracted in each test. The equations to estimate the depth and length of crack were provided by curve fitting of obtained data. Validation of provided equations with experimental results shows acceptable accuracy of the equations and algorithm used to estimate the depth and length of cracks in composite plates.