Use of laser spot thermography for the non-destructive imaging of thermal fatigue microcracking of a coated ceramic matrix composite

In this paper, an environmental barrier coating (EBC), which has undergone thermal cycling under spatiotemporal gradients, is inspected using active thermography. The technique considered herein is known as laser spot thermography. This study deals with the detection of a very thin crack network of unknown orientation. A numerical analysis is presented to investigate the sensitivity of experimental parameters on the detection. Image processing using a Laplacian operator combined with histogram equalisation to mitigate optical defects is then proposed to construct a cartography that is similar to scanning electron microscopy (SEM) observations despite the very adverse conditions.