Mechanical properties, thermal stability and microstructure evolution of carbon fiber-reinforced epoxy composites exposed to high-dose γ-rays

Carbon fiber-reinforced composites with superior strength-to-weight and stiffness-to-weight ratio were highly resistant to ionizing radiation, which make them popular in nuclear reactor. There were large doses of γ-radiation in nuclear reactor, which caused damage in composites. In order to investigate effect of high γ-ray absorbed dose on carbon fiber (CF)/epoxy (EP) composite, the doses of 2 MGy, 7 MGy, and 20 MGy were applied in irradiating the samples, and the mechanical properties, thermal stability and microstructural changes of composites were analyzed. The results showed that under the absorbed dose of 2 MGy, the storage modulus, flexural strength and thermal stability of CF/EP composites increased. However, those properties decreased while the dose increased to 7 MGy and further decreased while the dose rise to 20 MGy. The evolution mechanism was understood by analyzing free radical and composition change of CF/EP after irradiation via electron spin resonance and X-ray photoelectron spectroscopy. Irradiation results in bond-breaking such as C–C bond and C–H bond, and also new bond-forming like C–O and CO, which forms competition effects among radiation-induced degradation and cross-linking reaction. •Effect of high-dose irradiation on CF/EP composite was investigated.•Evolution mechanism was understood by EPR, XPS and ultrasonic C-scan.•Irradiation caused scission and cross-linking of resin molecular chains simultaneously.