Role of graphene oxide surface chemistry on the improvement of the interlaminar mechanical properties of resin infusion processed epoxy‐carbon fiber composites

The present study deals with the influence of graphene oxide functional groups on their ability to reinforce an epoxy resin when forming carbon fiber composites. Composites were processed through the direct vacuum infusion of the doped resin into carbon fiber fabrics. We used graphene oxide nanosheets with two different chemical characters: as‐produced graphene oxide, with a high oxygen content and acid character, and a simple ammonia base‐washed graphene oxide, which to a great extent removes the oxidative debris or highly oxidized fulvic‐like entities, resulting in an average lower oxygen content and cleaner surface sheets than as‐produced graphene oxide. Base‐washed graphene oxide performed considerably better in both tensile and mode‐I interlaminar properties of carbon fiber composites. The fracture energy required for the onset of mode I interlaminar fracture toughness was enhanced 31% when using as‐produced graphene oxide and 60% when using base‐washed graphene oxide by adding 0.2 wt% only. More interestingly, base‐washed graphene oxide produces a higher delamination resistance along the entire range of crack growth. The effect of adding graphene oxide with a cleaner surface and lower oxygen surface chemistry allows direct chemical bonding matrix‐graphene when the resin is curing, promoting a better interface fiber‐resin and consequently, improving the reinforcement efficiency. POLYM. COMPOS., 39:E2116–E2124, 2018. © 2017 Society of Plastics Engineers