JEC COMPOSITES MAGAZINE - Issue #52 - October 2009 - 48

FEATURE g…/… Automated mass production of fibre-reinforced components shown that both the one-electrode-gripper and the twoelectrode-gripper designed and constructed at the Fraunhofer IPT (see Figure 4) were functionally suitable for handling carbon-fibre-reinforced and glass-fibre-reinforced semi-finished products. Automation an effective sealing system were listed. Based on this catalogue and the current state of the art, new sealing systems were conceived for each half of the tools. The materials’ ability to provide the required properties was checked. Concepts were developed to improve the sealing systems. Different combinations of materials are being used with the objective of minimizing both the contamination of the sealing system and friction between sealing system and opposite surface. The design of the groove opposite the sealing geometry proved to be of key importance. The gap must be wide enough to put the sealing system under sufficient pressure, but not too wide to avoid leaving an open gap that may attract contamination. A specific test facility was designed and constructed to check whether a given sealing system was capable of meeting all the requirements (Figure 6). To allow the testers to have a clear view of the sealing surface and the effect at the shearing edges of the tool, a transparent framework was produced and installed (see Figure 6). In analyses under vacuum, a sealing system optimized for contamination and friction was qualified. Tool technology research In a second research project, the Fraunhofer IPT is optimizing the tool technology to meet the mass production requirements of fibrereinforced products. The ultimate objective of this project is to shorten the hardening and cross-linking processes, while reducing cleaning and maintenance times. For this purpose, the first stage of research is dedicated to experiments with electromagnetic induction as a means to shortening the heating and cooling periods during component hardening and cross-linking. Electromagnetic induction is capable of heating suitable metals (those that respond to inductive heating) extremely quickly and energy-efficiently. The plan is to apply thin, inductively-heatable layers to moulding tools made from different, non-inductively-heatable materials. These layers will be placed very close to the components ensuring that, due to their low mass, they respond very quickly to the application of heat and cool down at an equal speed. These experiments require an induction generator that was funded by the DFG and has already been purchased. The machine was selected on the basis of specific power and performance calculations. The energy generated by the new machine will be applied to the tool by an inductor that was specifically developed, designed and constructed for this purpose. The inductor was designed as a surface inductor and will enable the engineers to design a rapid sequence of thermal variation processes inside the tool. At the same time, finite element analyses of inductive heating were conducted for various materials and the influence of different process parameters was tested. So far, the approach chosen by the Fraunhofer IPT has generated extremely useful results, and it should accelerate the hardening and cross-linking processes of fibre-reinforced components significantly. Fig. 6: Test facility with modular test equipment. Conclusion Handling process automation, shorter cycle times below 10 minutes – achieved through shorter tool warm up and cool down periods – and reduced cleaning and maintenance requirements significantly contributed to reducing the massproduction costs of fibre-reinforced plastic components, while achieving high industrial quality and good mechanical properties due to a fibre volume content above 50%. This research is paving the way for the introduction of fibre-reinforced components into the world of cost-effective mass production, a welcome development in consideration of these components’ excellent technical properties and eco-friendliness. Contacts: martin.steyer@ipt.fraunhofer.de markus.dubratz@ipt.fraunhofer.de adrian.schuette@ipt.fraunhofer.de christian.wenzel@ipt.fraunhofer.de christian.brecher@ipt.fraunhofer.de Acknowledgments We would like to thank the Deutsche Forschungsgemeinschaft (DFG) for supporting and funding the FOR860 working group of researchers. Fig. 5: FE analysis of the temperature allocation inside the cross-section of the tool as a function of frequency. The influence of the frequency produced by the induction generator on the temperature allocation of the tool is shown in figure 5. A high frequency leads to a significant temperature gradient in the cross-section of the tool. This influence is caused in the skin-effect. The higher the frequency, the lower the depth of penetration into the material. This effect is also used to heat up tool surfaces near the part to be moulded very quickly. To shorten cleaning and maintenance operations and intervals, the currently-available sealing systems were also analyzed in the first stage of the research project. As an initial step, the requirements of jec composites magazine / No52 October 2009

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JEC COMPOSITES MAGAZINE - Issue #52 - October 2009

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