Numerical design of a caustic tank with regard to service life under consideration of ecological aspects
Long glass fibre reinforced thermoplastics (LFT) have a high potential for lightweight construction. As the tensile strength and impact strength of the material increase with increasing fibre length, significant material savings can often be achieved compared to conventional short-fibre reinforced materials. The thermoplastic foam injection moulding (TFI) with a physical blowing agent also enables a more fibre-friendly process control of LFT, which results in improved properties of the moulded parts. In addition, TSG offers greater geometrical freedom, allowing, for example, thicker rib designs and lower base wall thicknesses to achieve a load-compliant part design. These potential savings can be identified by using digital methods for a holistic view of the process.
In the public funded project DIGILaugBeh, IKV investigated the advantages of foam injection moulding with a physical blowing agent when processing LFT and developed corresponding design guidelines. In cooperation with project partners from industry and university, the simulation of foamed LFT was improved by implementing models for the calculation of fibre curvature in Moldflow. As a result, an improved moulded part design of the component could be achieved.
© BSH Hausgeräte GmbHIn the practical tests at IKV, in the first step the influence of plasticisation on the fibre length and viscosity of LFT was investigated for physical foam injection moulding. It was then compared to those of conventionally processed LFT. Longer fibres were found for TFI, particularly above the critical fibre length. The next step was to develop design guidelines for moulded parts made from foamed LFT.
Finally, these findings were transferred to the rear tray of a caustic tank in a washing machine and the guidelines were verified in scale-up tests. As part of the tests, the TFI-produced parts were compared with conventionally injection moulded and the series components. The use of TFI resulted in material savings of seven per cent with the same rigidity. At the same time, shrinkage and warpage were reduced and greater freedom in the design of the moulded part was achieved thanks to the improved dimensional accuracy.
Project data and funding
We would like to thank the BMWE for funding the project (funding code 03LB3044E) and the project partners for their cooperation.
Project duration: 01.01.2022 – 31.03.2025
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