University of Twente Student Theses
Process defects and resulting structure of unidirectional CF/LM-PAEK after induction welding.
Lamers, M.E.G. (2024) Process defects and resulting structure of unidirectional CF/LM-PAEK after induction welding.
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| Abstract: | Thermoplastic composites (TPCs) answer the demand for high-performance and lightweight materials. Their main advantage is their ability to melt, which allows the assembly of complex structures using fusion bonding methods. One of these methods is induction welding. Induction welding is already applied on woven carbon-fibre fabric reinforced TPCs, but the application on unidirectional plies is still limited. The cause lies in the difficulty of defining a robust process window to ensure defect-free welds. This research maps the process-induced defects that can occur in a unidirectional, quasi-isotropic CF/LM-PAEK induction weld. The aim is to better understand the relation between process parameters and final material structure. Several assemblies are welded to characterise the temperature and pressure distributions. The welding temperatures are measured using thermocouples during welding. The pressure distribution is visualised using pressure-sensitive foils. Afterwards, non-destructive inspection is done, followed by microscopic inspection. The highest temperature is reached in the central location at the weld interface and gradually decreases towards all edges. Visual inspection reveals edge effects in the assemblies and indents at the bottom of the high-temperature welds. The in-plane temperature distribution explains the indents. The indent is most apparent where the temperature is the highest. The pressure distribution supports this finding because this appears to be uniform across its application area. Non-destructive inspection showed that the bonded area at the weld interface has a similar shape to the in-plane temperature distribution. Microscopic analysis of the cross-sections of the indents of the weld revealed material flow, especially in the bottom laminate. Some delamination is visible at the thick indent edges seen in the high-temperature welds. The plies in the bottom laminate lying parallel to the welding direction show the greatest thickness differences. On the other hand, plies oriented orthogonal to the welding directions are relatively unaffected. The discussed changes in the material structure are caused by the local heating pattern rather than an inhomogeneous pressure distribution. Applying a cooling system at the bottom of the welded assembly can be considered to avoid the resulting defects. |
| Item Type: | Essay (Master) |
| Faculty: | ET: Engineering Technology |
| Subject: | 51 materials science, 52 mechanical engineering, 58 process technology |
| Programme: | Mechanical Engineering MSc (60439) |
| Link to this item: | https://purl.utwente.nl/essays/100472 |
| Export this item as: | BibTeX EndNote HTML Citation Reference Manager |
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