Simulation of the behaviour of shape memory polymers during the blow moulding process

Abstract

This STI-4 placement lasted 16 weeks at the DLR, Deutsches Zentrum für Luft- und Raumfahrt, the German research centre for aeronautics and aerospace, on the Aachen site. The theme of this internship was to carry out various simulations using Ansys Polyflow, with the aim of validating the behaviour of an extruded blown PA6.6 bottle in the face of heat input and to support a thesis written by Fabian Neumann, my internship tutor. This project focuses on the manufacture of composite parts, and in particular the tools used. The idea is to replace conventional tooling with easily recyclable thermoplastic moulding tools produced by extrusion blow moulding. Targeted thermal activation of the tooling would eliminate stretching of the polymer chains. As a result, the tooling would shrink and the undercuts in the parts could be demoulded. The idea is based on the phenomenon of shape memory. It is this behaviour that we sought to capture through various simulations. For ease of use and in order to validate the simulations with a physical model, the tooling was modelled by a bottle. Extensive studies of the extrusion blow moulding process and its simulation are known in the literature. However, the heating shrinkage process after the blow moulding process has not yet been really studied. In addition to simulations, manufacturing tests were carried out at the IKV, Institut für Kunststoffverarbeitung in Aachen (Institute for Plastics Processing), as well as heat shrinkage tests, in order to obtain physical results. Finally, rheometric measurements were carried out at DLR's Braunschweig site, in order to create a rheological model of PA6.6 and use it in the simulations. The aim is to quantify the stresses created in the material and potentially maximise them in order to optimise the heating shrinkage process.