The survival of a rover on the Moon depends on various factors, especially its ability to resist the cold lunar night, during which the surface temperature drops to -200°C for 14 days. To ensure a sufficient temperature inside the rover, it must be made of a structure offering high thermal insulation. For that purpose, the PEEKbot project proposes to use thermoplastic composites sandwich panels, which provides high structural integrity and the required thermal properties. These suggested structures are composed of a 3D-printed honeycomb core and two high-performance thermoplastic composite facesheets, which are assembled using thermoplastic welding techniques.
In the present work, induction welding is selected. This method relies on the application of a magnetic field to generate directly at the joining interface thanks to a susceptor material. Magnetic susceptors, in which heat is dissipated by hysteresis losses, are selected for the assembly of the sandwich panels. They are made of dispersed ferromagnetic particles in a thermoplastic polymer. The first step is to determine the crucial properties of the material and define a material selection methodology to select ferromagnetic particles based on the thermoplastic polymer and the available induction welding setup. Then, using the proposed methodology, Nickel particles are selected to prepare susceptor with poly-ether-ether-imide, a high-performance thermoplastic polymer. Characterization of the susceptors shows their satisfying heating properties and confirms that they can be used for induction welding.
The induction welding experimental setup is then adapted to the assembly of sandwich panels. The addition of a vacuum bag in which the sample is placed allows for the application of a constant and homogeneous pressure throughout the process. Samples are welded with this updated method, using the previously developed magnetic susceptor films. The welds conducted with optimal process parameters exhibit a skin/core strength larger than the tensile strength of the 3D-printed core. Then, susceptor films are replaced with a layer of susceptor directly printed on the honeycomb core, localizing the heat dissipation on the top of the cell walls. A complete characterization, from the 3D-printing filament of susceptor to the sandwich panels welded using this material concludes that this induction welding method is feasible, which is promising for future applications.
Finally, the vacuum induction welding method is transferred to the assembly of sandwich panels made of carbon fibres reinforced sandwich facesheets, which do not require the use of a susceptor as heat can be generated directly in the material. Modelling of the induction heating of the laminates is confirmed by experimental measurements, and sandwich panels are welded by induction. Once again, maximum skin/core strength is higher than the 3Dprinted core strength, which confirms that the vacuum induction welding method works correctly, and that it can be adapted to different materials and heating mechanisms.
| Date | 17 Jul 2024 |
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| Original language | American English |
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| Awarding Institution | - École de technologie supérieure
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| Supervisor | Martine Dubé (Supervisor), Jason Robert Tavares (Co-supervisor) & Christer Johansson (Co-supervisor) |
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Martin, R. G. (Author),
Dubé, M. (Supervisor), Tavares, J. R. (Co-supervisor) & Johansson, C. (Co-supervisor),
17 Jul 2024Student thesis: Doctoral thesis › Doctorate in Engineering: Engineering