NDTE using pulse thermography: Numerical modeling of composite subsurface defects

The ability to predict subsurface defect information in composite materials through a non-invasive, efficient inspection protocol is fast becoming a vital research area. In numerically modeling the thermographic process associated with an infrared (IR) technique we can afford inspectors the ability to predict subsurface defect information associated with a specific material configuration. The research involved in this study looks specifically at the finite element modeling (FEM) of delaminations in a composite flat plate setup. To date the modeling of delaminations has been restricted to only two dimensional (2D) numerical representations and associated primarily with rear faced detection. The results of this research, however, clearly show that the rear faced detection technique has limitations in defect depth prediction and the 2D approximation associated with this technique ignores a paramount effect in the form of lateral thermal diffusion. It is also made clear that the representation of experimental flat plate models with flat bottomed holes, under pulse phase thermographic inspection, in simulating delaminations is misguided.