Investigation of Graphene Reinforcement Effect on Young's Modulus of Cross-Linked Epoxy Nanocomposites by a New Heuristic Protocol

Abstract

Using a new heuristic procedure, the influence of graphene reinforcement on Young's modulus of crosslinked epoxy was analyzed. Graphene reinforcement was investigated for 1%, 2%, 3%, and 4% weight ratios. Graphene sheet edges were functionalized with hydrogen atoms and were placed middle of simulation cells. Simulation cell sizes were determined such that the graphene sheets were non-periodic. Thus, the edge effects of graphene sheets could be observed in dynamic simulations. The heuristic protocol is used for the crosslinking process of epoxy. It is less sophisticated than the multi-step iterative approach and is utilized for various components. It also updates higher-order covalent bond and partial charge terms in real-time to prevent inaccurate chemical couplings caused by ignoring angle-based covalent terms. Crosslinked epoxy structures were created by 80% with this new heuristic protocol as a matrix structure. To analyze the multiple variations with the same amount of molecules in each weight ratio, each simulation cell was built as three individual samples, and the standard deviation values were calculated. Young's modulus of the nanocomposite system was then calculated using a constant-strain energy minimization approach. The inter-atomic and intra-atomic interactions were described using the Molecular Potentials for Atomistic Simulation Studies (COMPASS) force field. As expected, the Young Modulus of epoxy resin increased with the addition of graphene reinforcement. This increase in Young's modulus was calculated by 6% for 1% graphene reinforcement, 10% for 2% graphene reinforcement, 14% for 3% graphene reinforcement, and 16% for 4% graphene reinforcement. As the graphene reinforcement ratio increases, the increase in Young's modulus tends to diminish. It's also worth noting that the MD simulation results in this work were in close agreement with the experimental results published in the literature. Both qualitative and quantitative numerical results show the effect of the abovementioned parameters. They will provide gain energy and time for prior synthesizing the new materials and serve as benchmark solutions for future comparisons of numerical and experimental results.