Evaluation of upper-scale mechanical parameters of particulate aluminum-based nanocomposites from molecular simulations

This paper focuses on the numerical and analytical determination of the mechanical parameters of aluminum-matrix nanocomposites using atomistic-scale simulations within a multiscale modeling framework. Molecular statics simulations were employed to evaluate the tensile and compressive behavior of Al based composites reinforced with nanosized alumina particles. Two classes of atomistic models were investigated. First, a unit-cell model containing a single Al2O3 monocrystal embedded in an aluminum matrix was used to examine the influence of the volume fraction of the ceramic inclusion on the effective mechanical properties. Second, a polycrystalline RVE model comprising an alumina particle was analyzed to assess the effect of the number of Al grains on effective properties. For each case, the mechanical response was characterized by stress-strain curves, enabling the identification of upper-scale material parameters associated with the elastic regime (bulk, shear and Young's modulus) and the damage stage (ultimate strength, ultimate strain, and failure strain). The isotropized elastic constants evaluated from molecular simulations were compared with classical Voigt-Reuss-Hill bounds to assess their applicability in the elastic regime. Finally, atomistic-scale simulation outputs provided insight into the dominant deformation/damage mechanisms (brittle versus ductile) and fracture modes (transgranular versus intergranular).