Damage mechanism characterisation of plain weave ceramic matrix composites under in-plane shear using in-situ X-ray micro-CT and deep-learning-based image segmentation

This paper investigates the microstructure and damage evolution of plain weave ceramic matrix composites under in-plane shear using the in-situ X-ray computed tomography approach. The actual microstructure and damage evolution of material under several successive loading levels have been revealed precisely. A deeplearning-based image segmentation method has been employed to accurately identify material damages, including matrix cracks, delamination, fibre pull-outs and interface debonding. Besides, three-dimensional visual characterisation and quantitative analysis of damage have been carried out to gain a better understanding on the failure mechanisms. For longitudinal tows under shear, the cracks propagate along the loading direction and cause the splitting and sliding failure of tow; For transverse tows under shear, they undergo coupling effects of shear and tension, which results in kink band damage with fibre bridging mechanism. Finally, the connection of longitudinal tow splitting and transverse tow kinking leads to the catastrophic fracture of CMCs under in-plane shear.