Retained Hygrothermal State Compression Damage Behavior Investigation of Carbon Fiber Reinforced Composites

This paper establishes a composite material damage analysis strategy that retains the hygrothermal state to investigate the damage behavior and mechanical performance characteristics of composite materials in hygrothermal environments. Initially, mass diffusion and heat conduction are equivalently considered, and a hygrothermal state predefined model is developed using a combination of sequential and fully coupled approaches. Then the hygrothermal stress field is extracted as the initial state of the compression process, and a compression progressive damage analysis is conducted using the VUMAT subroutine. Additionally, the accelerated hygrothermal aging experiments are conducted to investigate moisture absorption behavior and moisture diffusion coefficients. Then the quasi-static compression tests are carried out on the specimens before and after aging, with failure processes recorded using Digital Image Correlation (DIC). Experimental and simulation results reveal that hygrothermal conditions lead to matrix cracking and debonding from the fiber surface, generating an uneven stress field internally. This results in earlier occurrence and increased severity of delamination during the compression process. The dominant failure modes include wedge splitting and longitudinal cracking. The compressive strength, failure strain, and elastic modulus of the specimens decrease after aging. The analysis strategy developed in this paper effectively reflects the hygrothermal state during compression, aligning more closely with the actual physical processes.