LZH Successfully Completes Research Project „LaWocs“
The Laser Zentrum Hannover e.V. (LZH), Hanover, Germany, and seven other partners have successfully completed the research project „LaWocs“. From December 2010 to November 2013, the national and international project partners worked intensely on „Laser transmission welding of thermoplastic composite structures“.
In the last three years, the Eurostars project LaWocs was the first research project to investigate laser based welding of fiber reinforced materials. The goal of the project was to design a project chain from modifying the construction of components to the process, to adapting the material to the process, to optimizing the laser welding process itself.
European cooperation made it possible to consider all aspects of the individual processing steps for fiber composite workpieces in one research project. Within the framework of the three year joint project, new materials were designed, which are both suitable for laser transmission welding, but still maintain good mechanical properties. Additionally, investigations on a better understanding of the welding process for different thermoplastic materials were carried out, and used for the development of the welding parameters. Thus, the project partners ELEMENT, KVE, EPL, TODS, DEVA, TENCATE, FIBRE and the LZH were able, for the first time, to synergetically implement and optimize all the subprocesses in the material and process development and component construction, including material testing.
One of the main goals of the project was the development of a laser based process for welding fiber reinforced composite structures, and belonged to the responsibilities of the scientists in the Composites Group at the LZH. In order to carry out these welding processes, the optical characteristics of thermoplastic materials were used. They are partially transparent in the near infrared spectral range (NIR), and the correct laser radiation can be transmitted through the first welding partner. The laser radiation is then absorbed by the carbon fibers or the soot particles in the second welding partner, and the electromagnetic radiation is transformed into heat. Due to heat conduction between both welding partners, the respective plastics melt, and a welding seam is formed. The Composites Group has developed, among other things, processes for welding low transparency fiber composite materials, including glass fiber reinforced organic plastic sheets based on a polyetherimide (PEI) structure, which can be welded up to a material thickness of 2.4 mm. Furthermore, processes have been developed to weld thermoplastic angles and braces to components made of formed organic plastic sheets.
Laser Zentrum Hannover e.V. (LZH)
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