Compressive creep of virgin HDPE using equivalent strain energy density method

This paper presents a predictive model for compressive creep behavior of high-density polyethylene (HDPE) commonly used to manufacture polymeric piling and geosynthetics. Accelerated methods to predict the tensile creep of polymers are already available. In this paper, a method to predict the compressive creep of viscoelastic polymers is proposed based on the equivalence of strain energy density (SED) between conventional constant-stress creep tests and strain-controlled stress-strain (ramp loading at different constant strain rates) tests. There is good agreement between the creep behaviors obtained from conventional tests and SED predictions when two stress-strain experiments with strain rates differing by two or more orders of magnitude are used. SED was also used as a basis for predicting the onset of tertiary creep. Finally, onset of tertiary creep was used for rational selection of the ultimate strength of viscoelastic materials, whose strength is inversely proportional to duration of loading.