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Numerical Simulation of the Thermodependant Viscohyperelastic Behavior of Polyethylene Terephthalate Near the Glass Transition Temperature: Prediction of the Self-Heating During Biaxial Tension Test

LUO, Yun-Mei; CHEVALIER, Luc; UTHEZA, Françoise; MONTEIRO, Eric
Fonte: Wiley Publicador: Wiley
Relevância na Pesquisa
The poly ethylene terephthalate near the glass transition temperature highlights a strongly non linear elastic and viscous behaviour when biaxially stretched at high strain rates representative of the injection stretch blow moulding process. A non linear visco-hyperelastic model, where characteristics are coupled to the temperature, has already been identified from equi-biaxial tension experimental results. The weak form of the mechanical part of the model is presented and implemented into a finite element code developed in the Matlab environment and validated by comparing numerical simulation of equibiaxial testing with the analytical solution in the isothermal case. Considering the thermal aspects, an experimental study, where PETsheets are heated using infrared (IR for short) lamps is also presented. The modeling of the IR radiation of the sheet helps to identify the thermal properties of the PET. The thermal model is then implemented in the finite element code, coupled to the 2D viscoelasticmodel. A discussion ismade to justify the accuracy of the assumption made on homogeneity of the temperature field through the thickness. The simulation of the 2D plane stress equibiaxial test shows the important influence of the thermal aspects and the coupled thermo-mechanical software is used to quantify the selfheating phenomenon in the case of the biaxial elongations of PET sheets at high strain rates. POLYM. ENG. SCI....

Simulation of the stretch blow moulding process: from the modelling of the microstructure evolution to the end-use elastic properties of polyethylene terephthalate bottles

Fonte: Springer Publicador: Springer
Relevância na Pesquisa
The original publication is available at www.springerlink.com; The whole stretch blow-moulding process of PET bottles is simulated at the usual process temperature in order to predict the elastic end-use properties of the bottles. An anisotropic viscoplastic constitutive law, coupled with microscopic variables, is dentified from uniaxial tensile tests performed at different strain rates and temperatures. The microstructure evolution is characterised by crystallinity measurements from interrupted tests and frozen samples. For each specimen tested, the Young modulus is measured at room temperature. Numerical simulations of the blow moulding process are run using the C-NEM method. A micromechanical modelling is post-processed after the simulation to predict the elastic properties. Predictions of Young modulus distributions in bottles are in agreement with the ones measured on blow-moulded bottles.