Damage initiation and propagation mechanisms of 3-D angle-interlock woven composites under thermo-oxidative aging.

The thermo-oxidative aging behavior of carbon/matrix composite material reinforced with 3D angle-interlock woven perform (3DAWC) was investigated experimentally and numerically. The aim is to explore the damage mechanism of thermo-oxidative aging through micro-CT 3-D reconstruction. We found that the interface between adjacent orthogonal yarns is favorable sites for crack onset. Cracks extend horizontally from four free outer surfaces to the interior of the sample. The propagation of the crack is continuously hindered by the undulating warp tows. Crack volume and maximum crack depth are positively correlated with aging day. Realistic finite element models of 3DAWC are constructed according to CT slices to detect the influence of yarn architecture on the sensitivity to damage mechanism. The results show that diamond-shaped weft is the stress concentration areas caused by a temperature drop and the shrinkage of the nearby resin region is more serious. The finite element model can predict the most likely location of the crack initiation. [ABSTRACT FROM AUTHOR]