Optimised Lightweight Components from Foamed LFT: New Approaches for Part Design and Process Control
Long glass fiber reinforced thermoplastics (LFT) offer enormous potential for lightweight structural engineering. The use of thermoplastic foam injection moulding (TSG) with a motive fluid atmosphere improves mechanical properties, while innovative design guidelines optimize the process design. New research results enable material-efficient and load-compatible components with greater geometrical freedom.
Initial situation / problem:
Long glass fiber reinforced thermoplastics (LFT) have a high lightweight construction potential and enable material savings compared to conventional short fiber compounds. This is due to the
The increase in strength, impact strength and service life can be attributed to the increasing fiber length. However, there are currently no valid, universal design methods for LFT. Physical thermoplastic foam injection molding (TSG) with a foaming fluid atmosphere (ProFoam/KU-FIZZ/IQ Foam/ZiFoam) also enables a more fiber-friendly process control of LFT, which
This results in improved properties of the molded parts. The TSG also enables increased geometrical freedom to be achieved. For example, ribs can be made thicker and base wall thicknesses thinner in order to be able to implement the moulded part design in line with the load. Therefore, by using digital methods and taking a holistic view of the process, savings potential can be realised.
potential can be identified.
Objective:
The aim of the developments at IKV is to investigate the advantages of physical foam injection moulding with a motive fluid atmosphere in the processing of LFT and to develop design guidelines. Furthermore, IKV is working with partners from industry and science to improve the simulation of foamed LFTs and to implement fiber curvature in Moldflow. This is intended to achieve an improved moulded part design of the component.
Solution and results:
In the practical experiments at IKV, the first step is to investigate the influence of plasticisation during physical foam injection moulding on the fibre length and viscosity of LFT and
compared with those of conventionally processed LFT. Longer fibers were detected in the TSG, especially above the critical fiber length. The next step is to develop design guidelines for moulded parts made of foamed LFT. To this end, the influence of the flow path length and the rib design are investigated in order to optimize the effective fibre length in the moulded part. For this purpose, fiber length reduction, fiber agglomeration and fiber orientation along the flow path are investigated at different wall thicknesses. Various rib thickness/wall thickness ratios are investigated in order to achieve optimum properties when designing ribs. Finally, the findings are transferred to the rear tub of a lye tank in a washing machine and the guidelines are checked in scale-up tests. As part of the trials, the advantages of TSG are compared with conventional injection moulding and the series component.
Project data and funding
The research project 03LB3044E of the Chair of Plastics Processing at RWTH Aachen University is funded by the Federal Ministry of Economics and Climate Protection within the framework of the Lightweight Construction Technology Transfer Program (TTP Leichtbau) based on a resolution of the German Bundestag. We would like to thank all institutions and partners.
Project duration:
Project partners
