Method of scale bridging for thermoelasticity of cross-linked epoxy/SiC nanocomposites at a wide range of temperatures

In this study, we propose a sequential multiscale modeling approach to describe the thermoelastic behavior of cross-linked epoxy/silicon carbide (SiC) nanocomposites embedding different radii of nanofiller through molecular dynamics (MD) simulations and a continuum micromechanics constitutive model. In MD simulations, the coefficients of thermal expansion (CTEs), the elastic moduli, and the glass transition temperatures of different nanocomposites having different particle sizes are obtained at temperatures from 250 K to 550 K, the range in which cross-linked epoxy polymers generally experience the glassy-to-rubbery phase transition and consequently, their CTEs and elastic moduli change dramatically. In the equivalent continuum model, an interphase is defined between the particle and the matrix to account for the contribution of the polymer densification in the vicinity of the nanoparticle to the size-dependent CTE and elastic modulus at each temperature. Based on the thermal strain field defined in the micromechanics constitutive model, a physically meaningful description of the thermal expansion behavior of the interphase is obtained to reproduce the MD simulation results from fully continuum-based approaches for nanocomposites in rubbery state as well as in glassy state. Finally, the accuracy of the proposed multiscale approach is confirmed from finite element analysis.