Mechanical Properties of Epoxy Composites Reinforced Using a Carbon Fiber Film Type Coated with Carboxyl Graphene via an Economical Electrophoretic Deposition Technique

Carbon fiber-reinforced polymer composites (CFRPs) show high specific strength and stiffness compared with other fiber-reinforced polymer composites. However, these composites are most likely to fail at the interface/interphase of fiber and epoxy owing to minimal interaction between the epoxy and the fiber due to the chemically inert nature of the carbon fiber (CF) surface. Many CF surface modification techniques have been reported to increase the interfacial strength. Moreover, in some cases, incorporation of graphene fillers on the CF surface is an effective way to enhance the interfacial adhesion strength between CF and epoxy. Electrophoretic deposition is an effective technique to deposit graphene nanofillers on the CF fabric. In the current study, a novel combination of carboxyl-functionalized graphene (G-COOH) and magnesium nitrate hexahydrate (Mg(NO3)2·6H2O) has been chosen for preparing colloidal solution to deposit G-COOH on carbon fibers. This colloidal solution facilitates the adsorption of more Mg2+ ions on the large number of active carboxyl functional groups present at the edges of G-COOH platelets and develops a positive charge on them. These platelets get deposited on the cathodic electrode (i.e., carbon fiber fabric) with higher electrophoretic mobility during EPD. Hence, a uniform film-type layer of G-COOH platelets has been deposited with reduced EPD process parameters such as weight concentration of G-COOH platelets in suspension solution (g/L), deposition time, and voltage compared to other studies. The surface morphology of G-COOH platelet deposition on carbon fiber fabric has been examined using scanning electron microscopy (SEM). Surface characteristics of CFs have been studied using energy-dispersive X-ray spectroscopy (EDS) area mapping, FTIR, and Raman spectroscopy. Four layers of pristine and G-COOH platelet-deposited carbon fiber fabrics have been used to manufacture the final composites through the vacuum-assisted resin transfer molding (VARTM) technique. An increase in interphase thickness of the G-COOH CF composite over the pristine carbon fiber (PCF) composite was observed through carbon elemental EDS line scanning. The G-COOH-deposited CF composite showed enhancement in tensile strength and strain but reduction in flexural properties compared to PCF composites. This is due to the higher prevalence of void formation in the G-COOH-deposited composite.