Tensile and flexural strength enhancement in carbon-fiber epoxy composites using a novel and inexpensive method of particle type electrophoretic deposition of carboxyl functionalized graphene on carbon fiber

Abstract

Carbon fiber-reinforced polymer composites are strong, light weight and corrosion-resistant but are prone to fail at the interface of fiber and epoxy due to weak interfacial adhesion between the epoxy and the fiber. Formation of an interphase region with a continuous gradation of properties between fiber and the epoxy can potentially delay failure. Development of a larger interphase can be facilitated by the incorporation of graphene platelets on carbon fiber (CF) surface through various deposition processes. The present investigation utilizes a unique combination of carboxyl functionalized graphene (G-COOH) and magnesium nitrate hexahydrate to create a colloidal solution for the particulate type deposition of G-COOH onto carbon fibers through electrophoretic deposition (EPD). Four layers of EPD deposited carbon fibers have been used to make the composite using vacuum assisted resin transfer molding technique. Tensile and flexural tests have been conducted on the pristine and 0.45 wt.% G-COOH deposited carbon fiber (0.45G-COOH CF) epoxy composite. G-COOH addition leads to thickening of the interphase which has been confirmed through energy-dispersive X-ray spectroscopy line scanning. The tensile and flexural strength properties of the G-COOH deposited composites showed an increase of 62% and 12% respectively. These improvements can be attributed to the uniform deposition of G-COOH particles on the fiber and an increase in interphase thickness. Moreover, the addition of G-COOH in composites resulted in a 38% increase in tensile strain. The fracture surfaces of the failed composites were thoroughly examined through scanning electron microscope (SEM) and they showed that the failure mechanisms in both tension and flexural loading were severely affected by the presence of G-COOH.