Numerical analysis of notch-tip fields in rubber-modified epoxies

Abstract

In this work, the near-tip fields in notched specimens of pressure-sensitive nonporous and porous materials are investigated by finite element analysis. The specimen geometry and material properties are adopted from the corresponding experiments on rubber-modified epoxies. The Drucker-Prager yield criterion is first used to describe the yielding of nonporous materials. The yielding behavior of porous materials is based on a generalized Gurson yield criterion. The yield criterion for porous materials accounts for both the matrix material pressure sensitivity and the macroscopic pressure sensitivity due to porosity. Modifications are made on the yield criterion under negative mean stresses in order to account for the specific loading and geometry of the specimen. The computational results are compared with observed experimental cavitation zones and intense shear zones near the notch tip in specimens. Moreover, the near-tip fields and crack initiation sites ahead of the notch tip related to the volume fraction of rubber particles are investigated. The computational results suggest that the lowering of the mean stress ahead of the tip in rubber-modified epoxies with higher volume fractions of rubber changes the fracture mode from being controlled by high mean stresses at the elastic-plastic boundary to being controlled by large plastic strains closer to the notch tip.