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Research Papers

Constitutive Modeling of Damage Evolution in Semicrystalline Polyethylene

[+] Author and Article Information
José A. Alvarado-Contreras

Machine Design and Modeling Group, School of Mechanical Engineering, University of the Andes, Mérida 5101, Venezuelaajose@ula.ve

Maria A. Polak

Department of Civil and Environmental Engineering, University of Waterloo, Waterloo, ON N2L 3G1, Canadapolak@cee.uwaterloo.ca

Alexander Penlidis

Institute for Polymer Research, Department of Chemical Engineering, University of Waterloo, Waterloo, ON N2L 3G1, Canadapenlidis@cape.uwaterloo.ca

J. Eng. Mater. Technol 132(4), 041009 (Sep 29, 2010) (13 pages) doi:10.1115/1.4002367 History: Received December 22, 2009; Revised July 25, 2010; Published September 29, 2010; Online September 29, 2010

In this article, the description of a novel damage-coupled constitutive formulation for the mechanical behavior of semicrystalline polyethylene is presented. The model attempts to describe the deformation and degradation processes in polyethylene considering the interplay between the amorphous and crystalline phases and following a continuum damage mechanics approach from a microstructural viewpoint. For the amorphous phase, the model is developed within a thermodynamic framework able to describe the features of the material behavior. Amorphous phase hardening is considered into the model and associated with the molecular configurations arising during the deformation process. The equation governing damage evolution is obtained by choosing a particular form based on internal energy and entropy. For the crystalline phase, the proposed model considers the deformation mechanisms by the theory of crystallographic slip and incorporates the effects of intracrystalline debonding and fragmentation. The model generated within this framework is used to simulate uniaxial tension and simple shear of high density polyethylene. The predicted stress-strain behavior and texture evolution are compared with experimental results and numerical simulations obtained from the literature. By incorporating a damage mechanics approach, the proposed model predicts the progressive loss of material stiffness attributed to the crystal fragmentation and molecular debonding of the crystal-amorphous interfaces.

Copyright © 2010 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic representation of a polymer chain

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Figure 2

The eight-chain network model in (left) the unstretched and (right) stretched configurations

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Figure 3

Idealized deformation mechanisms in amorphous polyethylene

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Figure 4

Amorphous phase damage evolution for two different damage parameter sets

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Figure 5

An orthorhombic polyethylene crystal

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Figure 6

Schematic illustration of a two-phase composite inclusion

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Figure 7

Equivalent stress versus equivalent strain (see Eq. 60) behavior of semicrsytalline polyethylene under uniaxial tension

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Figure 8

Deformation rate ratio (Da/Dc) versus equivalent strain for the uniaxial tension case

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Figure 9

Equivalent stress ratio (σa/σc) versus equivalent strain for the uniaxial tension case

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Figure 10

Slip system maximum damage versus equivalent strain for the uniaxial tension case

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Figure 11

Amorphous phase maximum damage versus equivalent strain for the uniaxial tension case

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Figure 17

Slip system maximum damage versus equivalent strain for the simple shear case

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Figure 18

Predicted amorphous phase maximum damage versus equivalent strain for the simple shear case

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Figure 19

Pole figures of the (001) and (100) lattice directions and of the morphological textures at the equivalent strains of 1.04, 1.73, and 2.05 for the simple shear case

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Figure 20

Experimental pole figures of the (001) and (100) lattice directions at the equivalent strains of 1.04, 1.73, and 2.48 for the simple shear case

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Figure 21

Pole figures of the (001) and (100) lattice directions and of the morphological textures at an equivalent strain of 2.0, as predicted by the viscoplastic model (14), for the simple shear case

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Figure 22

Pole figures of the (001) and (100) lattice directions at equivalent strains of 1.04 and 1.73, as predicted by the viscoplastic model (58), for the simple shear case

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Figure 16

Equivalent stress versus equivalent strain behavior of semicrystalline polyethylene under simple shear

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Figure 15

Pole figures of the (001) and (100) lattice directions at the equivalent strains of 0.8 and 2.1, as predicted by the viscoplastic model (58), for the uniaxial tension case

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Figure 14

Pole figures of the (001) and (100) lattice directions and of the morphological texture at an equivalent strain of 1.0, as predicted by the viscoplastic model (19), for the uniaxial tension case

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Figure 13

Experimental pole figures of the (001) and (100) lattice directions at an equivalent strain of 2.1 for the uniaxial tension case

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Figure 12

Pole figures of the (001) and (100) lattice directions and of the morphological textures at the equivalent strains of 0.5, 1.0, and 1.95 for the uniaxial tension case

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