Coupled Macro and Micro-Scale Modeling of Polyurethane Foaming Processes

Abstract

Polyurethane foam is used for manufacturing different kinds of products, such as refrigerators, car dashboards or steering wheels. First, we developed a macro-scale simulation tool that is able to predict foam flow in such complex molds. Depending on the location within a product, final properties of polyurethane foams may vary significantly. These properties (e.g. thermal conductivity or impact strength) are strongly dependent on local foam structure. Modeling complex geometries like refrigerators completely on bubble scale is neither possible nor would it be efficient. The computational effort would be enormous. Therefore, we developed a micro-scale model describing bubble growth and the evolution of the foam microstructure in polyurethane foams considering a limited number of bubbles in a representative volume. Finally, we coupled our macro and micro-scale simulation approaches. For that purpose, we introduced tracer particles into our mold filling simulations. We are able to record information about density and temperature changes or varying flow conditions along particle trajectories. This information is then used to set up corresponding simulations on bubble scale. Through this coupling, a basis for studying the evolution of the local foam microstructure in complex geometries is provided. MACROSCOPIC SCALE: MOLD FILLING SIMULATIONSIn this section the mold filling simulation approach is briefly outlined. A detailed description of this approach and some validation examples can be found in [7]. In order to reduce the computational effort, the mold filling problem is reduced to a two-phase flow problem considering an air phase and a pseudo-homogeneous foam phase. The real system consists of an air phase and a foam phase containing small gas bubbles in a polymer phase, see left hand side of Fig.

Critical Buckling Load of Thin-Walled Plastic Cylinders in Axial and Radial Loading: Overview and FEA Case Study

“…Foam-filled components are also more vibration-resistant and therefore often have longer fatigue lives due to improved energy absorbency by the foam [36]. Several studies [37][38][39][40][41][42][43] have explored the production and use of polymer and metal foams for structural applications. In particular, expanding polyurethane foam has been widely used to strengthen static structural components to address a variety of interesting problems.…”