Prediction of Uniaxial Extension, Pure Shear and Equibiaxial Responses in Constant Deformation Rate Experiments from Single Step Stress Relaxation Experiments in Uniaxial Extension

Published

October 16, 2008

Author(s)

J M. Niemiec, G B. McKenna, J Sweeney, I M. Ward

Abstract

In working with non-linear constitutive descriptions for polymer melts, it is often forgotten how difficult it is to obtain the experimental data that are essential to their implementation in other than laboratory level tests. Here we adopt methods that have been successful in the description of rubber-like materials to melt behavior through the formalism of the BKZ (Bernstein, Kearsley and Zapas, 1963) constitutive equation. We show a simple method to obtain the material functions for the BKZ constitutive equation from a single deformation geometry. Single step stress relaxation experiments were carried out in uniaxial extension using a commercial poly(vinyl chloride) (PVC) above the glass transition temperature. From these data, assuming time-strain-temperature separability, we calculate a Valanis-Landel(VL) (Valanis and Landel, 1967) type of strain energy function as the kernel for the BKZ theory. The hybrid VL-BKZ model is then used to calculate the constant rate of deformation response of the PVC in three different deformation geometries: uniaxial extension, equibiaxial extension, and pure shear. The model calculations are compared with experimental results obtained on the same PVC material used previously by Sweeney and Ward(Sweeney and Ward, 1993; 1995).

Citation

Journal of Rheology

Pub Type

Journals

Keywords

BKZ Theory, melt, nonlinear viscoelasticity, polymer, rheology, rubber elasticity, strain energy function, time-strain separability, Valanis-Landel

Citation

Niemiec, J. , McKenna, G. , Sweeney, J. and Ward, I. (2008), Prediction of Uniaxial Extension, Pure Shear and Equibiaxial Responses in Constant Deformation Rate Experiments from Single Step Stress Relaxation Experiments in Uniaxial Extension, Journal of Rheology (Accessed December 30, 2024)