Volume changes in glassy polymers |
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Authors: | A D Drozdov |
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Institution: | (1) Institute for Industrial Mathematics, 4/24 Yehuda Hanachtom Street, Beersheba, 84249 Israel, IL |
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Abstract: | Summary Constitutive equations are derived for compressible glassy polymers at non-isothermal loading with finite strains. The model
is based on the theory of temporary networks in its version of adaptive links concept. The stress–strain relations are applied
to the analysis of uniaxial extension of a viscoelastic bar. Explicit formulas are developed for time-dependent Young's modulus
and Poisson's ratio of the bar at small strains. Results of numerical simulation are compared with experimental data for polycarbonate,
polyethylene, and poly(methyl methacrylate). It is demonstrated that (i) longitudinal stresses do not affect the specific
free volume in the region of linear viscoelasticity at strains up to about 0.2%, and cause substantial changes in the free
volume in the region of nonlinear viscoelasticity at strains about 1.0%; (ii) in the latter case, the increment of the free-volume
fraction is proportional to the increase in the specific volume.
Received 3 April 1998; accepted for publication 22 June 1998 |
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Keywords: | viscoelasticity glassy polymers constitutive equations volume relaxation Poisson's ratio |
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