Bending investigation on carbon fiber/epoxy composites nano-modified by graphene

Abstract

An extreme conditions situation, e.g. pre-salt deep sea exploration, requires new materials with even better performance. Nanotechnology is the new paradigm that can lead to the development of these new super materials. The effect of graphene pileups dispersion into carbon fiber/epoxy composites was investigated experimentally. The dispersion process was based on sonication and high shear mixing. XRD and SEM indicate that although the dispersion process can lead to exfoliated nanostructures, there is a saturation limit for the epoxy system, around 0.5 wt. %. The addition of graphene to carbon/epoxy composites seems to have no influence into stiffness, as the slopes of the stress-strain curves were near constant for all specimen tested. The bending strength, however, was heavily influenced by formation of graphene pileups into epoxy matrix and its dispersion around the carbon fibers. The increase on bending strength from 623.01±70.16 MPa (control samples) to 1259.92±61.73 MPa for 0.5 wt. % graphene addition represents an average improvement of 102%. This can be attributed to changes on failure mechanism, moving from intra-laminar failure to a mix failure mode where inter- and intra-laminar failure are combined in a zigzag pattern. A possible explanation for such behavior is the formation of strong bonds at the fiber/matrix surroundings due to nanostructures formation.