Thermal Aging Behavior of Carbon Fiber/Epoxy Composites at High Temperature

To investigate the thermal aging mechanism of carbon fiber/epoxy composites under high temperature (around 110 °C), the present study examined the inter-laminar shear properties and curing degree. Experimental results showed the inter-laminar shear strength of carbon fiber/Epoxy composites firstly increased following with the aging time increase which caused by secondary cure, then reduced for long-term of thermal stresses. Fourier transform infrared spectroscopy analysis revealed that the hydroxy functional groups had a certain growth which confirmed that secondary cure occurred during thermal aging. Electron paramagnanetic resonance results indicated that the increase of the intensity of free-radicals may cause by the chain breaking. Also scanning electron microscopy (SEM) images of fracture surface indicated that carbon fiber and matrix had well combination, which contributed to the better residual shear properties.