Finite element simulation of thermoforming processes for polymer sheets

The problem of modelling and the finite element simulation of thermoforming processes for polymeric sheets at various temperatures and for different loading regimes is addressed. In particular, the vacuum forming process for sheets at temperatures of approximately 200°C and the Niebling process for sheets at temperature of 100°C with high pressure loading are both described. Discussion is given to the assumptions made concerning the behaviour of the polymers and the physical happenings in the process in order that realistic models of the inflation part of each process may be produced. Stress–strain curves produced from experimental testing of BAYFOL® at various strain rates and temperatures are presented. A model for the elastic–plastic deformation of BAYFOL® is described and is used within the finite element framework to simulate the inflation part of the Niebling process. Numerical results for the deformation of sheets into a mould in the Niebling context are presented.