Thermo-oxidative aging induced multi-scale shrinkage and damage in 3D angle-interlock woven composites

The deterioration of resin and interface in composites deteriorate during high -temperature service, would impact both the thermal stability and overall performance significantly. This paper focused on the experimental characterization of multi -scale damage and resin shrinkage within composites induced by thermo-oxidative aging using Micro -CT, SEM and Confocal Interferometric Microscopy (CIM), and exploring the coupling mechanism between them. The results show that damage distribution and propagation are affected by the hierarchical structure of 3-D angle -interlock fabric. Macro-CIM shows that maximum resin shrinkage depth depends on the resin width and aging time. Resin shrinkage profile evolution demonstrated the accelerating effect of resin crack on shrinkage. Micro-CIM shows that macro yarn cracks form through the accumulation of micro resin cracks in resin -rich areas and fiber/resin interface debonding. The formation of fiber/resin interface crack is tied to the resin shrinkage state, only occurring when the surrounding resin shrinkage slope exceeds a specific threshold value.