Estimation of Defect Parameters in Quasi-Isotropic Composite Materials using Infrared Thermography

Estimation of defect size and depth in composite structures is a relevant problem as the aerospace and wind energy industries are increasingly using composites. The determination of defect depth and size is important in order to perform repairs and assess the integrity of the structure. The problem has been previously studied using simple 1D heat conduction models. Unfortunately, 1D heat conduction based models are generally inadequate in predicting heat flow around defects, especially in composites. In this study, a novel heat conduction model is proposed to model heat flow around defects accounting for 3D heat conduction in quasi-isotropic anisotropic materials. The proposed approach is used to quantitatively determine the defect depth and size. The validity of the model is established using experiments performed on a quasi-isotropic CFRP specimen with rectangular flat-bottom defects present at different depths.