Thermoforming process of semicrystalline polymeric sheets: Modeling and finite element simulations

A micromechanically-based elastic-viscoplastic model for the thermoforming process of semicrystalline polymer materials is proposed and implemented in a finite element code. This model takes into account the temperature and strain rate dependence. In this process the applied temperature is taken uniform throughout the sheet and its variation is due only to the adiabatic heating. The simulations are conducted for isotactic polypropylene using the finite element method. The polymer sheet thickness, the orientation of the polymer molecular chains, and the percent crystallinity show an important dependence on the process temperature (polymer softening) and the geometry of the mold. Based on recent experimental results in the literature, amorphization (decrease of crystallinity) is taken into account. Published in Russian in Vysokomolekulyarnye Soedineniya, Ser. A, 2008, Vol. 50, No. 5, pp. 841–849. This article was submitted by the authors in English.