Numerical Investigations of Internal and Residual Stresses in Aluminium-Polymer Laminate Foils during Stretch Forming

Abstract

Aluminium-polymer laminate foils consisting of the layers PA, Al and PVC are used to manufacture high barrier pharmaceutical packages. These so called cold-formed blister packs are formed by stretch forming at room temperature. As due to the complex material structure the forming process is not yet well understood, the developers of cold-formed blister packaging machines design the punches for forming the cavities bigger than needed for the tablets being packed. Therefore, the aim of this work is to gain insight into the mechanical behavior of the composite during stretch forming. For this, internal and residual stresses in the layers are analyzed with the finite element method. With the help of a micromechanical and a stretch forming model simulations are performed. Furthermore, an analytical solution to calculate the internal and residual stresses during stretch forming the foil is presented. The calculation procedure can be used to determine stresses from surface strains which could be measured in forming experiments.