Investigation the interphase formation process of carbon fiber/epoxy composites using a multiscale simulation method

A multiscale simulation method is newly developed to investigate the competition and interplay between diffusion and crosslink reactions during the formation process of interphase in carbon fiber/epoxy composite. The simulations are conducted by using fully-atomistic molecular dynamics (MD), coarse-grained dissipative particle dynamics (DPD) and Monte Carlo-like polymerizing models in combination. The distributions of each component molecules and functional groups are predicted as function of time and of distance from the fiber surface, respectively. The concentration profiles indicate a gradient transition region in vicinity of the carbon fiber. The profiles of the unreacted functional groups demonstrate that, nearby the fiber surface, the amount of hardener agent is chemically inadequate to react with epoxide from the resin and the sizing. Therefore, the crosslink density within the interphase transition zone is much lower than that in the matrix bulk. Accordingly, width of the interphase region is estimated, and is consistent with the experimental result.