Fatigue crack detection of CFRP composite pressure vessel using mechanoluminescent sensor

A novel technique has been developed to observe the stress distribution with the mechanoluminescent (ML) sensor. The ML materials are able to convert mechanical action to light intensity directly. Dynamic stress distributions on surfaces of various structures are visualized as patterns of light intensity by ML paint whiich is composed of ML micro-particles and binders. In this study, the ML sensor was applied to the CFRP composite pressure vessel surface and fatigue tests were performed by the pressurization repeatedly. By observing the ML pattern, we successfully detected fatigue cracks of pressure vessel before breaking. We utilized principal component analysis (PCA) for ML time series images. By comparing the first component of PCA results, a singular ML pattern was observed and fatigue crack position was successfully identified.