»ComMUnion« develops industrial processes for hybrid lightweight construction

by David Fleschen

Today, applications in mobility and transport increasingly require lightweight components to save weight and thus energy and resources. Hybrid components made of steel, locally functionalized by fiber composite plastics, combine this high mechanical strength with optimum mass. The demand for large-scale manufacturing processes that can cost-effectively produce such components is growing. In the EU research project »ComMUnion«, the two Fraunhofer institutes for production technology IPT and laser technology ILT, together with 14 other partners from industry and research, are developing such industrial processes for hybrid lightweight construction of metal and fiber composite plastics for the automotive and aerospace industries.

The new hybrid manufacturing process relies on a combination of laser structuring and laser-assisted tape laying: For this, the metal components are first pre-processed with the laser and provided with a specially developed and precisely defined rough surface structure. Due to the structuring, the lightweight construction elements, which are to serve for reinforcement later, can be mechanically added to the steel component without the need for further means of connection.

The reinforcements made of thermoplastic fiber-reinforced plastic, which are specifically adapted to the expected loads, are applied to the component by the automated tape-laying method. For this purpose, the laser heats the applied fiber-reinforced tapes locally on the metal immediately before the joining zone, so that the matrix material melts. It thereby penetrates into the surface structures and causes the tapes with the embedded fibers to adhere to the roughened surface of the steel component.

The combination of these two laser processes, for structuring and for heating, has its advantages precisely if the mechanical properties of the component are to be locally improved without the component weight significantly increasing. The process is particularly suitable for mass production because after the thermoplastic tapes have been deposited, no further post-processing steps are needed to consolidate the material. The precise, local heating also reduces the distortion and the residual stresses when joining the two different materials. The structuring with the laser, used by the Fraunhofer ILT, is not subject to any tool wear and can be used reproducibly and precisely on the metal component.

To demonstrate the suitability of the process in the form of a "proof-of-concept", the research partners have now produced a first demonstrator component made of high-strength steel and fiber-reinforced plastic: Based on a hybrid lightweight side skirts, a body component for the automotive industry, the two Fraunhofer Researchers Kira van der Straeten from the Fraunhofer ILT and Tido Peters from the Fraunhofer IPT tested and documented the functionality of the process combination as part of the ComMUnion project.

The project partners will present the component to the trade visitors at the JEC World lightweight exhibition in Paris from 12 to 14 March at the »Composites in Action Area« on stand 5D17.

The ComMunion project receives funding from the European Union's Horizon 2020 Research and Innovation Program under grant agreement no. 680,567th.

Source: Fraunhofer-Institut für Produktionstechnologie IPT, Photo: Fotolia

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