Effects of tougheners and thermo-oxidative aging on bending properties of carbon fiber/bis-maleimide composites

The composites with carbon fiber as the reinforcement, and three toughened bis-maleimide (BMI) resins as matrix were fabricated and then characterized by scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy with combination of the bending test in order to evaluate the thermal stability of these composites undergone thermal-oxidative aging at 150 °C up to 1000 h and to investigate the effect of toughener species on bending properties. The results showed that the BMI toughened by diallyl ether of bisphenol A (DABPA) had higher bending strength and good thermal stability because the DABPA has two reactive points that can increase the crosslinking density of cured BMI matrix via crosslinking reaction. FTIR indicated that three toughened BMI resins had some chemical changes after thermal-oxidative aging at 150 °C for 1000 h, but the morphology of fractured surface by SEM and bending test revealed that these changes showed slight effects on the bending strength and interfacial adhesion between carbon fiber and BMI matrix; the main fracture models of the composites during bending tests were fiber pullout and fiber fracture.