Investigation on mechanical properties and damage evolution of thermo-oxidative aged 3D angle-interlock woven composites under quasi-static tension

This paper reports tensile strain distribution and damage evolution of 3D angle-interlock woven composites (3DAWCs) after thermo-oxidative aging from tests and finite element analysis (FEA). It is found that the retention ratio of modulus in warp-directional loading (WP) is lower than that in weft-directional loading (WF) after 32 aging days. Aged samples exhibited reduced failure stress and strain. The surface strain distributions and damage patterns correlated with the woven structure. In WP, transverse cracks start from the resin-rich zone with the length limited to the distance between the warp yarns, followed by longitudinal cracks appearing at the warp-resin interface after loading to higher stress. In WF, only transverse cracks are initiated in the fiber-resin interface on the warp float and then propagate to the surrounding resin-rich zone. The crack initiation time is advanced and the failure strain decreases with the aging day. The FEA results support digital image correlation measurements and demonstrate that surface strain is influenced by the mesostructure in addition to the component's inherent properties.