On the Effects of Anisotropy in Detecting Flaws of Fibre-Reinforced Composites

Abstract

AbstractHerein, the effect of anisotropy on the thermal response of two carbon fibre-reinforced composite samples (unidirectional and cross-ply) is studied using step-heating thermography. An objective methodology is developed for qualitative and quantitative analyses of flaws using their aspect ratios and signal-to-noise ratio (SNR). The procedure uses principal component analysis, Gaussian filter, and binarisation for marking the candidate flaw locations. After experimenting on different heating/cooling regimes, single-phase cooling was nominated to further the study. It is found that short thermal excitations reveal surface flaws while increasing the heating period improves the visibility of deeper flaws. Anisotropy, due to fibre alignment, affects the aspect ratio of flaws, distorts their shape, and conjoins clustered flaws. In contrast, SNR values seem to be insensitive to anisotropy. The proposed method offers a quick and simple procedure for post-processing thermal images and highlights the implications of anisotropy therein.