On the importance of the dilatational component of the stress state in the uniaxial yield-like behavior of rate-dependent polymers: C. Bauwens-Crowet revisited

Abstract

The effect of the dilatational stress component on the yield-like behavior of rate-dependent polymers is examined via the example of PMMA. Starting with uniaxial data published in 1973 by C. Bauwens-Crowet and describing the dependence of yield (maximum) stress in compression and in tension, the then offered reduction or “shift” scheme is reviewed, in particular the fact that tension and compression data lead to different data reductions. Following the argument that mechanically induced dilatation can affect the time dependence of polymeric deformation processes much like temperature affects temporal scaling, the same data is then subjected to an analysis based on volumetric changes accompanying mechanical loading. It is found that such a treatment unifies the compression and tension data into a single master curve to the extent that temperature and loads from the two deformation modes are congruous and exhibit no more data scatter than the presentation of the original data reduction. Moreover, the time–temperature shift properties for this newly reduced yield-like behavior then follows also the same rules and properties as do viscoelastic mechanical properties acquired under small deformations.