Reactive Molecular Dynamics Simulation of Epoxy for the Full Cross-Linking Process

Epoxy resins are used extensively in composite materials for a wide range of engineering applications, including structural components of aircraft and spacecraft. The processing of fiber-reinforced epoxy composite structures requires carefully selected heating and cooling cycles to fully cure the resin and form strong cross-linked networks. To fully optimize the processing parameters for effective epoxy monomer cross-linking and final product integrity, the evolution of mechanical properties of epoxies during processing must be comprehensively understood. Because the full experimental characterization of these properties as a function of degree of cure is difficult and time-consuming, efficient computational predictive tools are needed. The objective of this research is to develop an experimentally validated Molecular Dynamics (MD) modeling method, which incorporates a reactive force field, to accurately predict the thermo-mechanical properties of an epoxy resin as a function of the degree of cure. Experimental rheometric and mechanical testing are used to validate an MD model, which is subsequently used to predict mass density, shrinkage, elastic properties, and yield strength as a function of the degree of cure. The results indicate that each of the physical and mechanical properties evolve uniquely during the cross-linking process. These results are important for future processing modeling efforts.