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Hybrid joints with metallic SLM structures
Design and production engineering measures for additive surface structuring of metallic components to optimise the composite properties of thermally joined metal-FRP hybrid joints
Project duration
From: 01.01.2021 To: 31.03.2023Description
In this project, the influence of different metals, the production-related surface roughness in the SLM process, as well as the targeted introduction of surface structures on the achievable joint strengths of plastic-metal direct joints was investigated. Furthermore, different plastics were used with unreinforced polycarbonate, as well as with polyamide and polypropylene organic sheets. The joints were made using hot plate or infrared direct joining.
The results showed that the strength development is less due to adhesive bonding but more due to form closure with the surface structures. The specific increase of roughness or porosity had only little influence on the joint strength, whereas too high porosity reduced the strength. It is therefore recommended to use standard parameters for SLM specimens with high strength.
The investigation of the additive surface structuring of the metal showed that for joints with most plastics, a structure height of 0.5 mm, a structure width of 0.6 mm and a structure spacing of 1.2 mm resulted in the highest joint strengths. However, the results differ with organic sheet due to the high fibre content. Here, the structures must not be too wide and must also have a certain minimum spacing so that the glass fibre bundles can interact with the structure.
The structure geometry was also varied, with head tension being the most critical loading direction. A mushroom structure showed the best head tensile strengths for PA organic sheet and polycarbonate of up to 25 MPa. This was due to a sufficiently dimensioned undercut.
The joints proved to be resistant to accelerated ageing due to temperature storage, thermal shock and climate change tests.
Acknowledgements
The IGF project 21417 N of the Research Association FSKZ e.V. is funded by the Federal Ministry of Economics and Climate Protection (BMWK) via the German Federation of Industrial Research Associations (AiF) within the framework of the Programme for the Promotion of Industrial Cooperative Research (IGF) on the basis of a resolution of the German Bundestag.
The entire research results can be found in a comprehensive research report after completion of the project, which can be ordered from the SKZ.
