Procedure for detecting the shape and size of defects on metallic substrates under composite repairs using shearography

This paper presents a numerical-experimental procedure to characterize through-holes with arbitrary shapes present on metallic substrates under composite material sleeves using pulsed laser shearography and dynamic excitation combined to the finite element method. The so-called fitting process consists of matching experimental and numerical results in order to determine the shape and dimensions of the holes under the composite repair, or even quantify defects between layers of the composite laminate. The results show that the technique is capable of characterizing, in the worst case, the geometry of a hole with 83% accuracy and its respective area with a maximum error of approximately 20%. The advantageous results achieved in this research show that the fitting process can be very useful for real applications in the oil and petroleum industry.