Characterization of the viscoelastic-plastic properties of UPVC by instrumented sharp indentation

The yielding behavior of glassy polymers may be sensitive to the hydrostatic pressure and also be influenced by the strain rate. Thus, the yield strength is a function of hydrostatic pressure and strain rate instead of a constant. In this paper, using dimensional analysis and finite element simulations, we established a method to estimate the yield strength of glassy polymers by instrumented indentation. Together with the method for determining shear creep compliance proposed in our previous work, the viscoelastic-plastic properties of glassy polymers can be extracted from a single indentation load-depth curve. Applications were illustrated on unplasticized polyvinyl chloride (UPVC). The shear creep compliance and yield strength of UPVC were successfully determined by a single indentation test. Using these parameters, the true stress-strain curves of UPVC under different strain rates were approximately predicted according to a linear viscoelastic-perfectly plastic constitutive description.