Effects of thermo-oxidative aging on flexural properties of carbon fiber fabric reinforced polymer matrix composites

In order to explore the reinforced structure effects on the flexural strength of carbon fiber reinforced polymer matrix composites (CF-PMCs) after thermal-oxidative aging, the thermal-oxidative aging properties of 3D four-directional braided carbon fiber/epoxy composites (3D braided composites for short) and laminated plain weave carbon fabric/epoxy composites (laminated composites for short) were studied. The samples before and after thermos-oxidative aging were analyzed by means of FTIR, aging mass loss, bending test and SEM. The results indicate that the oxidation chain scissions of matrix resin and the degradation of the bonding force of fiber/matrix interface caused by thermal-oxidative aging are the reasons for the decrease of the flexural strength and flexural modulus of the two kinds of composites. Flexural strength is more easily affected by thermal-oxidative aging than flexural modulus. Under the same thermal-oxidative aging conditions, the thermal-oxidative aging mass loss of laminated composites is larger than that of 3D braided composites, but the flexural strength and flexural modulus retention rates of the 3D braided composites are greater than those of laminated composites. After age at 140 ℃ for 1 200 h, the flexural strength and flexural modulus retention rates of laminated composites are 74.7% and 88.3%, respectively, and those of corresponding 3D braided composites are 79.4% and 91.5%, respectively. Therefore, adopting 3D braided preform as the reinforcement of CF-PMCs is an effective way to improve the thermo-oxidative stability.