Enhanced mechanical properties at 400 °C of carbon fabric reinforced phthalonitrile composites by high temperature postcure

Phthalonitrile resins have received growing attention due to their superior thermal stability and good structural properties required for high temperature applications in aerospace industry etc. In this work, a newly developed phthalonitrile blend resin with an appropriate viscosity for autoclave processing is employed for manufacturing of high quality void-free thick composite panels using MT300 carbon fabrics. In particular, the effects of postcure temperature are systematically examined on their 400 °C mechanical properties required for high temperature structural applications. Dynamic mechanical analysis reveals that the composite postcured at the high temperature of 375 °C exhibits a high glass transition temperature over 450 °C. Mechanical testing results show that the flexural and compressive strengths at room temperature are lowered by the high temperature postcure, but their counterparts at 400 °C are obviously enhanced by the postcure. Moreover, the 400 °C interlaminar shear strength initially decreases but then increases with increasing the postcure temperature. The char retention in nitrogen at 1000 °C is 89% of its initial weight. Consequently, the newly developed phthalonitrile resin is highly promising for manufacturing of thermal resistant polymeric composites for high temperature application in aerospace industry etc. that need composites to have high temperature capabilities.