Analyses of viscoelastic solid polymers undergoing degradation

Abstract

In this paper we study the three-dimensional response of isotropic viscoelastic solid-like polymers undergoing degradation due to mechanical stimuli. A single integral model is used to describe the time-dependent behaviors of polymers under general loading histories. The degradation is associated to excessive deformations in the polymers as strains continuously increase when the mechanical stimuli are prescribed, and therefore we consider a degradation threshold in terms of strains. The degradation part of the deformations is unrecoverable, and upon removal of the prescribed external stimuli, the accumulation of the degradation strains lead to residual strains. We also systematically present material parameter characterization from available experimental data under various loading histories, i.e., ramp loading with different constant rates, creep-recovery under different stresses, and relaxation under several strains. We analyze viscoelastic-degradation response of two polymers, namely polyethylene and polyoxymethylene under uniaxial tensile tests. Longer duration of loading can lead to increase in the degradation of materials due to the substantial increase in the deformations. The single integral model is capable in predicting the time-dependent responses of the polymers under various loading histories and capturing the recovery and residual strains at different stages of degradations.

Analysis of the variable‐order fractional viscoelastic modeling with application to polymer materials

“…The comparison results for four VO functions are shown in Figure 11. In addition, from a mechanical point of view, the mechanical evolution law of polymer materials will become apparently softer as it is degraded during the process of creep and recovery 52 . As illustrated in Section 3, the rising tendency of fractional order from 0 to 1 represents the property transition of materials from elastic solid to a viscous fluid.…”

A viscoelastic-viscoplastic model for a thermoplastic and sensitivity of its rheological parameters to the strain-rate

“…This dependence is physically explained by their structure in macromolecular chains whose mobility, entanglement, branching and crosslinking are the main factors at the origin of the viscous aspect [9]. Taking into account these microscopic factors makes it possible to better understand the macroscopic response and contributes to the establishment of relevant behavior models [10]. On the other hand, it is very difficult to account the influence of all the physical mechanisms in the behavior laws, from which the application of the phenomenological models .…”