Aging of carbon fiber/bis-maleimide composites in oxidative conditions

Bis-maleimide (BMI) resins are widely applied, particularly in polymer-matrix composites for heat-resistant fields, due to their excellent thermal and mechanical properties. The thermal resistance is crucial for the applications of carbon fiber reinforced BMI composites in aerospace fields. The thermo-oxidative aging and its effects on the mechanical properties of carbon fiber reinforced BMI composites were investigated by scanning electron microscopy (SEM) with the combination of flexural strength test and inter-laminar shear strength (ILSS) test at 150°C. The results indicated that the mechanical properties of carbon fiber/BMI composites were affected significantly by testing temperature. SEM results showed that the good adhesion of fiber and matrix resulted in the better mechanical properties. However, some amorphous area of BMI resin were motivated for the internal energy increased at high temperature (150°C). Therefore, the matrix resin showed viscoelastic behavior that resulted in the remarkable dependence of mechanical properties of the composites on temperature, which led directly to the lower flexural strength and ILSS at 150°C.