Development of a Constitutive Model of Polypropylene for Thermoforming

摘要

In this paper the authors outline a constitutive model, implemented within finite element analyses, which was developed for large deformation, high temperature multi-axial stretching of polypropylenes. The model has been generalised to a fully 3-dimensional thermally coupled form. The paper describes how model parameters were characterised using constant width, biaxial and sequential stretching of polypropylenes at elevated temperature using a custom built flexible biaxial stretching machine developed at Queen's University Belfast. The paper presents results of finite element model predictions of material stretching behaviour compared to range of physical experiments. The results presented in the paper confirm that this model is very effective in predicting the complex thermo-mechanical behaviours of polypropylenes at elevated temperatures.