Fracture Analysis of Crosslinked Phenolic Resins byMolecular Dynamics Simulation with Reactive Force Field

Abstract

We performed atomistic molecular dynamics (MD) simulation for fracture analysis of cross-linked phenolic resins under tensile deformation with ReaxFF reactive force field. The MD results showed that material properties in the equilibrium state and linear elastic region are well consistent with experimental values and MD results using classical force field. Stress－strain relationships and changes in chemical bonding information in the large deformation region suggested that selective cleavage of covalent bond between phenolic ring and methylene causes macroscopic fracture of cross-linked structure. The change in three-dimensional structure showed fracture mechanisms that lead to macroscopic destruction by aggregation and inhomogeneous growth of voids due to elongation of molecular chains and breaking of chemical bonds at the void－resin interface. The MD results also indicated that the origin of fracture is not necessarily due to stress concentration in the region of low crosslink density, but is derived from the increase in crosslink density fluctuation induced by tensile deformation.