Numerical modeling of stress corrosion cracking of polymers

Abstract

A unified chemo-mechanical model is developed to simulate stress corrosion cracking (SCC) of high density polyethylene (HDPE) in a chlorinated environment. The model consists of three components, each of which captures a critical aspect of SCC. A chemical kinetics–diffusion model is used to simulate the reactions and migration of chemical substances. The fracture behavior of HDPE is captured by a cohesive crack model, in which the cohesive properties are considered to be dependent on the extent of the chemical degradations. The time-dependent creep behavior of the bulk HDPE material is described by an elastic–viscoplastic constitutive model. This chemo-mechanical model is numerically implemented for finite element (FE) analysis of SCC of HDPE structures. The simulations show two different failure mechanisms depending on the applied stress level: at high stresses, the failure is primarily due to the excessive plastic deformation whereas at low stresses the chemical reactions and diffusion are the dominant factors leading to failure. In addition, examination of detailed crack growth kinetics reveals that at low stress levels the disinfectant concentration has a significant effect on the crack growth behavior through the relative dominance between the chemical reaction and diffusion processes.