Multi-Scale Analysis to Characterize Mechanical Properties of Nanoparticle/Polymer Composites

Abstract

Sequential multi-scale analysis to characterize the size effect of nanoparticle on the mechanical properties of nanoparticle/polymer composites is developed and verified through molecular dynamics simulation and continuum micro mechanics model. This study focuses on the construction of the nanoscale information transfering scheme to validate continuum micro scale model for convenient analysis and design of nano-structured composite systems with efficiency and accuracy. In order to obtain the nano-scale effect of nanoparticle in detail, two sets of nanocomposites having dilute and non-dilute distributions of nanoparticles. In each set, totally five different unit cells with different particle size and same volume fractions were prepared and simulated using molecular dynamics approach. Spherical silica nanoparticle and amorphous polyimide were chosen as reinforcement particulate fiber and matrix respectively and Parrinello-Rahman fluctuation method was used to obtain mechanical properties of each systems. In accordance with the volume fraction of each sets, both dilute multi-scale mechanics(DMM) and non-dilute multi-scale mechanics(NDMM) models are developed incorporating the effective interface as the resultant phase of particle size effects. Postulating that the Young’s modulus and shear modulus of the interface as functions of particle radius, monotonous decaying functions to represent shear modulus and Young’s modulus were obtained from least square approximation. As a result, it was found that as the particle size decreases, reinforcing effect of the nanoparticle increases and our developed micro mechanics methodology exactly reflect the size effect of nanoparticle. In order to verify the present multi-scale methods, elastic properties of various volume fraction cases obtained from multi-scale solutions are compared with molecular dynamics simulations results. In addition, the applicability of DMM and NDMM methods at different compositions are investigated.