Modeling of time dependent mechanical behavior of polymers: Comparison between amorphous and semicrystalline polyethylene terephthalate
Résumé
Revisited network theory to account for inelasticity1,2 was used to model behavior of amorphous and semicrystalline PET. Semicrystalline materials were obtained through cold crystallization of the amorphous one making the crystalline microstructure the only difference. The model considers microstructure at a mesoscopic level through the description of an equivalent network evolving with internal state variables. Inelastic phenomena are assumed to result from the evolution of entanglements and of density of weak bond between adjacent chains (van der Walls or H-bond, etc.). The experiment data base included nonmonotonic tensile test coupled with synchronized digital image correlation and infrared measurement device for capturing the time and temperature dependence of the material. Model show a pretty good ability to reproduce time dependent behavior of the two materials. Analysis of the parameters also shows a coherent evolution with the microstructure though this latter is not explicitly accounted for in the model. Further study will make relationship between microstructure and parameters clearer