The Effect of Silicone Modification on the Thermo-Oxidative Degradation and Mechanical Property Retention of CFRP Laminates

The mechanical properties of CFRP laminates degrade significantly in extreme thermal environments above the onset temperature of thermo-oxidative degradation of the matrix. This study investigates the thermo-oxidative damage evolution and mechanical degradation mechanisms of CFRP laminates with silicone-modified epoxy (SME) and neat epoxy (EP) through thermogravimetric analysis, multi-scenario thermo-oxidative degradation tests, tensile/compressive measurements and multi-scale SEM observations. The results show that silicone modification reduces the peak mass loss rate from approximately 10 to 6 %·min−1; at 350 °C for 3 h, the mass loss of SME-based CFRP is about 42.3% lower than that of EP-based CFRP. Strengths under all loading configurations decay monotonically with degradation severity, with the strength of SME-based laminates exceeding that of the EP counterparts by up to 139.7% under the most severe condition. The C–Si–O hybrid network suppresses matrix degradation and fiber–matrix debonding, delaying crack initiation and propagation, thereby markedly enhancing the thermo-oxidative damage tolerance of the composites. This work provides data support for damage-tolerance design and safety assessment of composite structures in extreme thermal environments.