Damage Evolution and Strength Degradation of 3D Angle-Interlock Woven Composites under Cold Shock Temperature Gradients

During high-to-low temperature shock, three-dimensional (3D) angle-interlock woven composites experience significant temperature gradients and deformation incompatibility within the material. Owing to the large mismatch in the coefficients of thermal expansion between carbon fibers and epoxy resin, asynchronous deformation between the constituents generates substantial interfacial shear stresses, leading to interfacial debonding and internal damage accumulation. To investigate the damage evolution mechanism and mechanical performance degradation of the composites under cold shock conditions, three initial temperatures (80 °C, 115 °C, and 150 °C), selected based on the glass transition temperature of the epoxy resin, were combined with liquid nitrogen cooling at −196 °C to establish different cold shock temperature gradients. Micro-computed tomography (Micro-CT) was employed to characterize the internal damage morphology and spatial distribution, while quasi-static compression tests were conducted to evaluate the residual mechanical properties of the composites. The results indicate that cold shock treatment induces pronounced surface cracking along the through-thickness direction, accompanied by progressive internal damage propagation. Furthermore, the residual compressive properties of the composites exhibit a continuous decline with increasing temperature gradient. These findings reveal the influence mechanism of cold shock temperature difference on damage evolution and strength degradation in 3D angle-interlock woven composites and provide a theoretical basis for their application in extreme thermal environments.