Degradation Behavior and Failure Mechanism of <scp>T800</scp> Carbon Fiber Reinforced Polymer in the Simulated Polar Multi‐Factor Coupled Environment

ABSTRACT This study systematically investigates the aging behavior of T800 carbon fiber reinforced polymer composite under a multi‐factor coupled environment simulating the Polar marine environments, integrating moisture absorption, freezing–thawing cycles, cryogenic exposure, and ultraviolet irradiation. The coupled environmental exposure reveals pronounced and differentiated degradation in tensile, compressive, flexural, and shear properties. The results demonstrate that moisture absorption combined with freezing–thawing cycling induces matrix plasticization and interfacial debonding, while ultraviolet irradiation further accelerates resin degradation and defect accumulation. Based on the coupled aging response, a regression‐based model is established to correlate mechanical degradation with aging cycles, enabling lifetime prediction of composites in Polar environments. This work provides a more realistic framework for evaluating the long‐term durability and reliability of composite materials under extreme service conditions.