Study on the Hygrothermal Aging Properties of Degradable Epoxy Resin‐Based <scp>CFRP</scp>

ABSTRACT The durability of degradable carbon fiber reinforced polymer (CFRP) under hygrothermal conditions is critical for its practical applications. In this study, a biological diglycidyl ether pentaerythritol vanillin dimer (DEPVD) epoxy resin casting and its CFRP were investigated. The effects of hygrothermal aging (60°C, 80% RH, 90 days) on moisture uptake, mechanical performance, and thermal behavior were systematically examined. It was found that the water absorption response of the degradable epoxy resin casting and CFRP represented the initial Fick's diffusion response and a followed long‐term deterioration response. The saturated moisture content of the resin casting is 2.30%, while that of the CFRP is 0.50%. After hydrothermal aging, the tensile and shear strength of CFRP decreased by 4.0% and 9.2% respectively. The glass transition temperature increased by 3.2% in the degradable epoxy casting but decreased by 6.77% in the CFRP. Dynamic viscoelastic behavior exhibited nonlinear variation. Microscopic analysis revealed interfacial delamination caused by water intrusion, which disrupted hydrogen bonds and induced hydrolysis, leading to overall performance degradation. These findings provide experimental basis and mechanism support for the application of degradable epoxy resin‐based CFRP in actual service environments.