Mechanical, thermal, and electrical properties of amine- and non-functionalized reduced graphene oxide/epoxy carbon fiber-reinforced polymers

Graphene and its related materials are increasingly applied in fiber-reinforced polymers to tailor their material properties for high performance composites. Yet, the use of graphene derivatives that underwent a plasma functionalization process is not well understood. This study uses 1.50 wt.% of unfunctionalized (rGO) or plasma-treated reduced graphene oxide with amine-functionalities (frGO) in an epoxy matrix to prepare unidirectional pre-impregnated carbon fibers. The material characteristics of the graphene-modified carbon fiber-reinforced polymers (g-CFRP) are compared to the neat carbon fiber-reinforced polymer (CFRP). Both g-CFRP configurations exhibit a higher void content than the neat CFRP. No significant difference between the CFRP and the g-CFRPs is observed with respect to the Young's modulus, glass transition temperature, storage modulus, specific heat capacity, thermal conductivity at room temperature, and in-plane electrical conductivity. Yet, a reduction in ultimate tensile strength of up to -13% is noted. In addition, the apparent interlaminar shear strength and transverse electrical conductivity are increased by up to +12% for the rGO-CFRP and +52% for the frGO-CFRP. This knowledge will support the selection of additives for fiber-reinforced polymers for, for example, lightning strike protection in aircrafts, sensory materials, electromagnetic interference shielding or heat transfer elements.