Mechanical degradation of carbon fiber reinforced polymer composites under coupled multi-factor aging in a simulated polar environment

Carbon fiber-reinforced polymer (CFRP) composites are pivotal to equipment in Polar Regions, yet their long-term durability in this low-temperature marine environment is severely compromised by the synergistic degradation of coupled environmental factors. Traditional single-factor aging studies cannot replicate this complex scenario, leaving a critical gap in service life prediction. An accelerated aging protocol incorporating simultaneous hygrothermal, freeze-thaw, sub-zero freezing, and UV exposure was established to systematically investigate the degradation of T700 and T800 CFRP composite materials under simulated polar environments. Results reveal that failure is fundamentally dominated by the interface variation since matrix-relevant flexural and shear strengths decline drastically (up to 45%), whereas fiber-dominated Izod impact strength remains nearly intact. A synergistic degradation sequence is proposed: the process commences with interfacial stress induced by hygrothermal swelling, followed by damage propagation during freeze-thaw cycles, stress accumulation (locking) during sub-zero freezing, and is accelerated by UV radiation, which generates defects that facilitate moisture ingress. This work provides a scientific basis for material selection, durability prediction, and the design of robust marine composite structures.