Investigating fracture mechanisms in glassy polymers using coupled particle-continuum simulations

We study the fracture behavior of glassy polymers using a multiscale simulation method that integrates a molecular dynamics (MD) system within a continuum domain. By employing a nonlinear viscoelastic constitutive model in the continuum domain, the MD system undergoes non-uniform deformation with flexible boundaries through interaction with the surrounding continuum. Systems with pre-defined double cracks are subjected to tensile stretch under various geometric constraints and bond breakage criteria. The simulation results show that geometric constraints primarily affect deformation behavior at small strains, but their influence diminishes at larger strains. In the stage of fracture, increased deformation correlates with a narrowing distribution of microscopic structures at molecular scales, such as bond length. This distribution converges across different systems just before fracture, irrespective of ultimate stress, fracture strain, bond breakage criteria, and geometric constraints. This convergence suggests that the distribution of microscopic structures is a fundamental property linked to the fracture behavior of glassy polymers.