Characterization of moisture absorption and flexural performance of functionalized graphene modified carbon fiber composites under low energy impact

Abstract

AbstractComposite failure due to in‐service low energy impact damage and moisture absorption is a major risk for these materials within aerospace, automotive and other engineering sectors. Deterioration in post‐impact flexural properties, and the tendency of thermosets to absorb moisture are some of the few drawbacks of carbon fiber reinforced polymers (CFRPs). Adding graphene into the matrix is theorized to improve mechanical properties and reduce moisture uptake. This study evaluates the diffusion characteristics and flexural properties of carbon fiber/epoxy composites modified with NH2 functionalized graphene (CFRP/graphene nanoparticle [GNPs]) before and after impact under various environmental conditions. Adding GNPs to CFRP decreased the flexural strength and modulus by 24% and 25% respectively before impact. After impact, the flexural strength and modulus decreased by 7.4%–23.6% and 37%–67%, respectively. For both composites after undergoing impact, the residual strength and stiffness were considerably reduced due to delamination and transverse cracking. Samples with graphene inclusion experienced a slower rate of ethanol and water diffusion, for both unimpacted and impacted samples, by 46.4% and 44.8%, respectively. Moisture uptake also reduced the flexural properties of both composites. Scanning electron microscopy revealed good dispersion but poor bonding of graphene to the matrix, which is believed to be the reason for property reduction.