Theoretical evaluation of surface oxidation effects on resin dynamics at the carbon fibre-resin interface

Carbon fibre-reinforced plastics are gaining attention as exceptional structural materials. However, analysing the mechanism of the curing reactions at the interface is essential to further enhance their performance and ease of handling. Epoxides and amines react on oxidised fibre surfaces; however, their dynamic behaviour and the impact of the type of oxygen-containing functional groups have not yet been elucidated. Consequently, we utilised all-atom molecular dynamics simulations to model the interface in a simplified manner and theoretically analysed the dynamic behaviour of epoxides and two types of primary amines (symmetric and asymmetric) on graphene surfaces subjected to different oxidation treatments. These results indicate that the presence of an interface reduces the diffusivity of the resin molecules, especially when the surface is modified with epoxy groups. Analysis of the structure of the interface's nearest neighbour by mass-density profile and radial distribution function revealed that a wide range of factors contribute to the reduced diffusivity, including changes in molecular shape and orientation, 7C-7C interactions, and hydrogen bonding. Therefore, this atomic-level phenomenon at the interface may affect the reactivity of the curing reaction and influence the polymer structure.