Evaluations of atomic-resolution strain fields using molecular dynamics simulations combined with corrected smoothed particle hydrodynamics

Deformation analyses of polymeric materials using molecular dynamics (MD) simulations are very useful in evaluating the physical properties based on the atomic features. Generally, the average responses of a system, such as the stress-strain response, are evaluated, but a molecular chain around a solid should deform in an unusual manner in a composite system, such as a solid/polymer system. This may lead to damage and a microscopic inelastic deformation, ultimately affecting the macroscopic behavior of the material. In this study, we propose a technique for use in evaluating the local pseudo-continuum deformation quantities, such as strain and stretch, during MD simulations by introducing deformation analysis via corrected smoothed particle hydrodynamics in a total Lagrangian formulation. Three different types of systems (uniform deformation of an Au crystal, cured resin sandwiched between silica walls, and cured resin containing a nanofiller) are considered, and the unique local deformations in the composite systems are quantitatively evaluated. In particular, local constitutive behavior can be evaluated using this technique, and in the sandwiched system, a high correlation is observed between the local stiffness inhomogeneity and the cohesive failure point. In the filler-containing system, a highly rigid epoxy resin layer is observed around the filler, and local deformation at the poles of the filler is confirmed owing to elongation. The observed trends are consistent with the experimental results. The insights obtained should contribute to the evaluation and understanding of microscopic deformation and damage, which is the beginning of macroscopic failure in a composite material.