Multi-scale modeling of cross-linked epoxy nanocomposites

The effect of different sized alumina (Al2O3) nanoparticles on the mechanical properties of thermoset epoxy-based nanocomposites is investigated using molecular dynamic (MD) simulations combined with sequential scale bridging methods. In molecular structures, the cross-linked networking effect of the pure EPON862 (R)-TETA (R) polymer has been independently considered and validated by MD simulations. Based on the validation of pure epoxy structures, nanocomposites' unit cells, consisting of spherical Al2O3 particles and epoxy, have been constructed. In order to investigate the particle size effects, various unit cells having different particle radii but the same volume fraction have been considered and simulated. The mechanical properties of the nanocomposites are calculated using the Parrinello-Rahman fluctuation method to give an enhanced reinforcing effect in smaller particle reinforced cases. Based on the MD simulation results, the sequential bridging method is adopted for efficient estimation of the particle size and epoxy networking effects. An effective interface concept is incorporated as a characteristic phase which can describe the particle size effects. The values calculated from the micromechanics model are in good agreement with those of the molecular dynamics simulations. (C) 2008 Elsevier Ltd. All rights reserved.