Multiscale simulation of fullerene reinforced composite structures: From molecular dynamics to finite element continuum mechanics

Abstract

The aim of the present study is to propose a multiscale computational technique for the prediction of the elastic mechanical properties of nanoreinforced composites. The proposed method utilizes a molecular dynamics (MD) based numerical scheme to capture the mechanical behaviour of the nanocomposite at nanoscale and then a classical continuum mechanics (CM) analysis based on the finite element method (FEM) to characterise the microscopic performance of the nanofilled composite material. The material under investigation is polyamide 12 (PA 12) randomly reinforced with fullerenes C60. At the first stage of the analysis, in order to capture the atomistic interfacial effects between C60 and PA 12, a very small cubic unit cell containing a C60 molecule, centrally positioned and surrounded by PA 12 molecular chains, is simulated via MD. Inter- and intra-molecular atomic interactions are described by using the Condensed Phase Optimized Molecular Potential for Atomistic Simulation Studies (COMPASS). According to the elastic properties data arisen by the MD simulations, an equivalent finite element volume with the same size as the unit cell is developed. At the second stage, a CM micromechanical representative volume element (RVE) of the C60 reinforced PA 12 is developed via FEM. The matrix phase of the RVE is discretised by using solid finite elements which represent the PA 12 mechanical behaviour while each C60 location is meshed with equivalent solid finite elements. Several multiscale simulations are performed to study the effect of the nanofiller volume fraction on the mechanical properties of the C60 reinforced PA 12 composite. Comparisons with other corresponding experimental results are attempted, where possible, to test the performance of the proposed method.