Damage in Rubber-Toughened Polymers – Modeling and Experiments

The superior ductility and toughness of rubber-toughened polymers relies on microscale deformation and damage mechanisms such as void growth, shear yielding and crazing. In the present work, a micromechanical model for the inelastic deformation behavior of rubber toughened polymers is developed which focuses on the effect of crazing, i.e. the formation of localized cohesive zones of fibrillated material. It is assumed that the formation and growth of multiple crazes in the brittle matrix between dispersed rubber particles – refered to as distributed crazing – is the major source of overall inelastic strain. This notion is cast into a homogenized material model that explicitely accounts for microstructural parameters such as the volume fraction and size of the rubber particles. The model is implemented as a user subroutine in LS-Dyna. Tensile tests under different loading conditions on Acrylonitrile-Butadiene-Styrene (ABS), a representative of rubber-toughened polymers, are used to determine the material parameters of the constitutive model. Numerical simulations as well as experiments are conducted on a Single-Edge-Notched-Tensile (SENT) specimen in order to validate the model and to study the inelastic deformation and fracture behaviour of ABS. The suitability of the model is analyzed by comparing numerical and experimental results.