An efficient high-throughput grafting procedure for enhancing carbon fiber-to-matrix interactions in composites

It is widely acknowledged that the integrity of the fiber-to-matrix interface inherent to carbon fiber reinforced composites has scope for improvement. One promising and highly-researched strategy is the use of surface manipulation of carbon fibers to enhance their mechanical performance under shear. The complexity of commonly used surface treatments, such as plasma and oxidative etching, Requires modification of existing manufacturing infrastructure and thus their broad adoption in a manufacturing context has been limited. Herein we show that simply impregnating the carbon fibers with aryl diazonium salts and subjecting them to external stimuli, such as mild heating (100 °C), can induce surface modification which can deliver improvements of up to 150% in interfacial shear strength (IFSS) in epoxy resins. Interrogation of the fiber-to-matrix interface using molecular dynamics simulations suggests that the surface grafted molecules imparts a ‘dragging effect’ though the polymer phase and that the surface concentration of these compounds is critical to enhancing IFSS. This process obviates the practical limitations of current functionalization procedures for carbon fibers and requires infrastructure that is already routinely available on fiber manufacturing lines.