A Micromechanics Analysis of Nanoscale Graphite Platelet-Reinforced Epoxy Using Defect Green's Function

摘要

In the modeling of overall property of composites, the effect of particle interaction has been either numerically taken into account within a (representative) volume element of a small number of particles or neglected/ignored in order for efficient solution to a large system of particles. In this study, we apply the point-defect Green's function (GF) to take into account the effect of particle interaction. It is applicable to small volume fractions of particles (within 10 %). The high efficiency of the method enables a simulation of a large system of particles with generally elastic anisotropy, arbitrary shape and composition, and arbitrary spatial distribution. In particular, we apply the method to study the nanoscale graphite platelet reinforced polymers, guided by some preliminary experimental observations. We first verify the method by comparing the prediction with a full-field model in the case of a regular lattice of particles. The comparison has demonstrated that the method is a considerable improvement over the classical Eshelby's method employing the regular GF and thus ignoring the effect of particle interaction. Upon the verification, we apply the method to examine the effect of a number of parameters on the overall composite behavior. The effect of particle interaction is shown to be strongly dependent on particle arrangement due to the strong elastic and geometrical anisotropy in graphite platelets. The strongest effect occurs when the platelets are orientated uniformly and stacked in a simple cubic lattice. However, the (overall) effect becomes trivial when the platelets are randomly orientated, which is expected. The effect of platelet aspect ratio is also studied. Finally, a thin soft layer is inserted between the platelets and the matrix material in order to simulate a partial bonding condition between them. It is shown to play a significant role in determining the overall composite behavior. The present work sets up a base for further large-scale simulations of micro-damages (microcracks, particle debonding, etc.) under interaction, as well as providing insights to further experimentation in graphite platelet nanocomposites.