Numerical Simulation of the Viscohyperelastic Behaviour of PET near the Glass Transition Temperature

The presentation deals with the non linear strongly elastic and viscous behaviour of poly ethylene terephthalate near the glass transition temperature and biaxially stretched at high strain rates representative of the injection stretch blow moulding process. A non linear visco-hyperelastic model identified from the experimental results of the equi-biaxial tension test is implemented into a finite element code developed in the Matlab environment. The thermal behaviour modelling, identification and simulation has also been managed. The model was used to simulate the 2D plane stress case and then was applied to a 2D axi-symmetric case. Both simulations are compared with equi biaxial testing. The final goal of this work is to perform the free blowing simulation to compare with experimental data. Therefore, we should solve an iterative procedure for a thermo-mechanical equation. At each time step, the proposed visco-hyperelastic model is used for the mechanical part, and a classical heat transfer equation is discretized for the thermal part. All mechanical parameters are reactualized from the temperature field.