The time dependent strain potential function for a polymeric glass

Gregory B. McKenna, Louis J. Zapas

Research output: Contribution to journalArticlepeer-review

6 Scopus citations

Abstract

Torsion and normal force measurements were made during single step stress relaxation experiments on a polymeric glass (PMMA). Isochronal data were analysed using an approach adapted from that developed by Penn and Kearsley1 (for incompressible elastic materials) to determine the derivatives ∂W ∂I1, and ∂W ∂I2 of the time dependent strain potential function. ∂W ∂I1 and ∂W ∂I2 are determined from existing solution to the torsion of an incompressible cylinder. A special solution to the torsion of a compressible cylinder is presented and it is shown that the values of ∂W ∂I1 and ∂W ∂I2 obtained using this solution to analyse the data do not differ greatly from those obtained using the incompressible solution. It is found from both solutions that ∂W ∂I1 is negative and increases towards zero with increasing time and deformation while ∂W ∂I2 is positive, greater in magnitude than ∂W ∂I1 and decreases towards zero with increasing time and deformation. These results were unexpected and a full understanding of their meaning has yet to be reached.

Original languageEnglish
Pages (from-to)543-550
Number of pages8
JournalPolymer
Volume26
Issue number4
DOIs
StatePublished - Apr 1985

Keywords

  • compressible material
  • non-linear viscoelasticity
  • poly(methyl methacrylate)
  • polymer glass
  • strain potential function
  • torsion

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