Recent advances in slow crack growth modeling of polyethylene materials

Abstract

Slow crack growth (SCG) is a time-dependent quasi-brittle type of failure that polyethylene (PE) materials exhibit under low stress levels. The interplay between the crack and its plastic zone dictates complex damage behavior of continuous and discontinuous SCG. Under a continuum mechanics approach, SCG can even remain a commonality in PE mechano-chemical degradation (MCD). Therefore, a deep understanding of SCG is critical since it’s the controlling mechanism for most field failures and consequently the formalism of PE lifetime prediction models. In this work, a comprehensive review of the recent advances on PE SCG modeling is presented. PE SCG and MCD macro and micro mechanisms are explained. The evaluation test methods of SCG are discussed. Owing to PE continuous and discontinuous SCG modes, using the parameters of conventional Fracture Mechanics, e.g., stress intensity factor, J-integral, or crack opening displacement, may be considered only within their applicable range. The crack-layer (CL) theory was found capable in accounting for PE SCG kinetics and thermodynamics including its two fracture modes. The theory framework along with several applications are demonstrated. Hence, the main objective of the manuscript is to provide a thorough review of SCG in PE materials to give a direction to making reliability assessments more predictive.

Keywords

• Review
• Slow crack growth
• Mechano-chemical degradation
• Polyethylene materials
• Micromechanism
• Testing