Anisotropic viscoelasticity/damage coupled thermodynamic model for transparent polymer

Abstract

Transparent polymer such as PMMA has been used for manufacturing viewport windows of deep-sea manned submersible. This paper develops an anisotropic viscoelasticity/ damage coupled thermodynamic model under finite-deformation framework for creep analysis of PMMA polymer. By introducing the strain equivalence principle with the effective stress concept, a four-order damage tensor that is composed of a two-order damage tensor conjugated to the two-order thermodynamic force, is imposed on the elastic tensors of two springs to describe mechanical degradation of material, and a damage potential function is proposed to derive the rate of two-order damage tensor. After the Drucker-Prager’s type failure criterion is met, damage induces anisotropy, which also accelerates damage evolution conversely. The developed model and numerical algorithm are first used to study the creep behaviors of a dog-done PMMA tensile specimen by comparing with the creep experimental results of material, and then the creep behaviors of the PMMA conical viewport window under constant water pressure by comparing with the creep experimental results of window well.