Abstract
The mechanical behavior of semi-crystalline polymer has been characterized experimentally taking into account the damage occurring in large deformation. The mechanical properties and deformation mechanism are dependent on the applied loading types. Therefore, the influence of the loading history resulted from prior deformation due to the applied loading types executed are studied. To quantify this effect, samples of high density polyethylene were tested under uniaxial tension with several loading paths, monotone, loading/unloading/recovery/reloading and cyclic tests at different strain levels, even at large deformation. The volume strain was determined in real time during the tests by an optical extensometer. The results show clearly that, the mechanical behavior of High Density Polyethylene (HDPE) is significant affected by the strain rate history, but for the cycling recovery and cycling deformation tests, no history loading dependency for the stress and volume strain was found. In order to predict the damaged behavior of semi-crystalline polymer, a constitutive model was developed in which the elasto-viscoelastic-viscoplastic behavior of material and the influence of damage causing volume variation are described. A new thermodynamic potential based on a non-equilibrium thermodynamic approach of irreversible processes was introduced in the developed model. The model was validated for high density polyethylene (HDPE), which showed the ability of the model to reproduce complex loadings paths, and to predict the mechanical behavior based on loading history.