University of Twente Student Theses
Resistance de-welding of thermoplastic composites : Next step in sustainable joints
Jong, Maarten Christiaan de (2024) Resistance de-welding of thermoplastic composites : Next step in sustainable joints.
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| Abstract: | Carbon-reinforced thermoplastic composites are increasingly used in the aerospace industry due to their lightweight properties and promising characteristics. These characteristics compromise fast processing times and recyclability enabled by the (re)-meltability of the thermoplastic matrix material [1]. Traditional thermoset composites require lengthy curing processes and cannot be remelted [2]. The thermoplastics’s meltability allows for welding which can achieve fast processing cycles and reduces stress concentrations [3]. However, while significant research has been done on welding techniques, little attention has been given to disassembling these welded joints, a crucial process for maintenance, repair, and recycling in the aerospace industry. This thesis focuses on the disassembly of thermoplastic composites by first reheating the joint interface and applying forces to separate the bonded parts with minimal damage. In this thesis, this dissembling is referred to as ”de-welding”. De-welding is the reverse of the welding process. The de-welding in this thesis focused on resistance heating as the heating method, as it directly heats the joint interface, reducing the heat-affected zone to avoid damage in the composite adherends. Moreover, the heating element remains in the joint, which is advantageous for reprocessing. The main objective of this research was to assess the feasibility of de-welding thermoplastic composites using resistance heating. More specifically, with a woven carbon fiber as the heating element and carbon fiber-reinforced low-melting poly-aryl-ether-ketone (CF/LMPEAK) adherends. The feasibility was evaluated through numerical modeling and experimental tests on two geometries: coupon-sized specimens and larger structural elements. For the latter, an experimental test bench was developed. The predictive numerical model successfully captured the heating behavior by measuring validation. The model also showed that using a heat sink at the boundary of the laminate surfaces and a glass fiber layer significantly affected the through-thickness heating behavior. The results of the couponsized specimens showed that de-welding via resistance heating is a feasible method for lowering the disassembly force. These specimens used a PEI interlayer, enabling processing temperatures below the melt temperature of the LMPEAK adherends and so keeping the adherends intact. When applied to all LMPEAK, larger structural elements, de-welding successfully achieved low disassembly force, no de-consolidation, and an intact heating element. These outcomes were obtained by applying a heat sink, a glass insulator layer, and a relatively short processing time. The specimens were rapidly heated to melt temperatures at the interface, resulting in almost zero-strength remaining. This thesis took the first step in de-welding by resistance heating by showing the feasibility of the process. The heat sinks showed great cooling rates but made the process quite energy-demanded. More research is required to develop this disassembly technique into a qualified manufacturing process in the aviation industry. |
| Item Type: | Essay (Master) |
| Clients: | NLR, Marknesse, Netherlands |
| Faculty: | ET: Engineering Technology |
| Subject: | 52 mechanical engineering |
| Programme: | Mechanical Engineering MSc (60439) |
| Link to this item: | https://purl.utwente.nl/essays/104472 |
| Export this item as: | BibTeX EndNote HTML Citation Reference Manager |
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