Identification des propriétés élastiques orthotropes par couplage « expérimentation – simulation numérique » : application aux fonds de bouteilles soufflées en PET

Validation of stretched blown bottles of polyethylene terephthalate (PET) by using numerical simulation is an important industrial goal. This necessitates the identification of the PET material characteristics. Because the biaxial elongation of macromolecules induces great modifications of the mechanical properties of the material, it is difficult to manage an accurate simulation: properties are not well known in the base or neck region of the bottles. The aim of the work presented here is to provide an identification tool for the orthotropic elastic properties in the 3D regions of PET bottles of soda waters. A stereo correlation tool has been developed in order to build digital 3D surface. By comparing the initial surface with the same surface when the bottle is under pressure, it is possible to evaluate the membrane strains at each point of the petaloid surface. Coupled with a finite element simulation managed on the same bases, these results allow the identification of the induced mechanical properties. Two bases, one with large valleys (VL) between the five feet and one with small valleys (VS) which highlight very different behavior when bottles are submitted to internal pressure. The deformation of the VL base presents non-linearities that are discussed in the last section of the paper