Molecular Level Modeling of Fiber-Epoxy Interphase with Monolayer Silane

In this study, we are developing Mixed-Mode traction-separation response of fiber-matrix interphase in the presence of monolayer glycidoxypropyltrimethoxy silane (GPS) using all-atom molecular dynamics (MD) simulations. To develop the atomistic model, first we deposit GPS molecules on the silica (fiber) surface at different number densities and react them with the silica surface through condensation reaction. A mixture of Epon828-Jeffamine® D-230 is then put on the silica surface and equilibrated to predict the epoxy-amine diffusion into the monolayer silane using the general AMBER force field. Epoxide-amine curing reaction among the epoxy, silane and amine is modeled using the cross-linking algorithm. The model is then subjected to Mode-I, Mode-II and Mixed-Mode loading with the reactive force field ReaxFF to predict the stress-strain responses and failure loci within the interphase. Strain-rate and GPS bond-density dependent 3D Mixed-Mode traction surface will be developed to bridge length scale in the continuum level micro-mechanics modeling. Detailed structure of the interphase at the atomistic scale at different GPS concentration will be reported. Interphase structure-properties relationship will be established to design interphase from Materials-by-Design perspective.