Progressive Damage Model for Composite Laminates in Hygrothermal Environments

Carbon fiber-reinforced polymer composites are used in a wide variety of applications, and the mechanical properties of these materials are degraded by hygrothermal aging. Hence, a three-dimensional progressive damage model was proposed in this study to help predict the failure of composite structures in hygrothermal environments. Using finite element analysis software, a UMAT subroutine was developed that can predict and analyze the failure mode and damage evolution of composite structures in hygrothermal environments. To verify the performance of the proposed model, moisture absorption and three-point bending tests were carried out on T300/5208 composite specimens exposed to hygrothermal conditions (70 °C and 85% RH) for different durations. The results showed that the saturated moisture absorption rate was approximately 0.56%, and the hygrothermal effects reduced the flexural strength of the T300/5208 composite laminate by 10.3%. Finally, the cross-section and fracture morphology were observed by digital microscope and field emission scanning electron microscope (FSEM), and the mechanism of hygrothermal aging was analyzed.