Mechanical characterization of graphite/epoxy nanocomposites by multi-scale analysis

Mechanical properties of nanocomposites consisting of epoxy matrix reinforced with randomly oriented graphite platelets were studied by the Mori-Tanaka approach in conjunction with molecular mechanics. Elastic constants of graphite nanoplatelets, which are the inclusion phase in the micromechanical model, were calculated based on their molecular force field. The calculated elastic constants compared well with both experimental data and other published theoretical predictions. The results of the Mori-Tanaka micromechanical analysis, using the graphite platelet moduli calculated by molecular mechanics, were found to be insensitive to the variation of out-of-plane modulus E-3 and Poisson's ratio v(13). However, the nanocomposite modulus is sensitive to the in-plane modulus E, and out-of-plane shear modulus G(13) of the graphite platelets and less sensitive to the in-plane Poisson's ratio v(12) for its small range of variation under consideration. The calculations confirm that the modulus of the nanocomposites studied here is strongly dependent on the aspect ratio of the reinforcing particles, but not on their size. The predicted moduli compare favorably with experimental results of several nanocomposites with graphite particles of various aspect ratios and sizes. (c) 2007 Elsevier Ltd. All rights reserved.