Fracture of amorphous polymers: A gradient-damage theory

Abstract

© 2020 Elsevier Ltd We have formulated a new gradient-damage theory for the deformation and failure of amorphous polymers. Our theory accounts for inelastic deformation and damage due to crazing, and also due to a network-disentanglement mechanism, with the damage eventually culminating in brittle fracture at small levels of stretch for the former mechanism, or ductile fracture at relatively large levels of stretch for the latter mechanism. Our damage theory depends not only on a damage variable but also its gradient, and this helps to regularize the strain-softening behavior during the damage process to avoid mesh-dependency related issues during finite element simulations. We have numerically implemented our theory in a finite element program, and using this simulation capability we show that the predictions from our theory match (reasonably well) the load–displacement curves – as well as the crack-paths under mixed-mode loading conditions – for polymethylmethacrylate (PMMA) as well as polycarbonate (PC) in several technically relevant geometries reported in the literature. The good correspondence of the results from our numerical simulations and available experimental data indicates that our simulation capability should be of practical utility in the design and analysis of structures made from PMMA and PC under largely tensile dominated stress states, the ones that usually control structural failure.