Date of Award
8-16-2024
Document Type
Open Access Thesis
Department
Mechanical Engineering
First Advisor
Paul Ziehl
Abstract
Recent advancements in the aerospace industry, coupled with the anticipated future significance of air travel, have spurred research aimed at increasing manufacturing production and aircraft flying efficiency by implementing new materials and assembly methods. Advanced air mobility (AAM), a subset of the aerospace industry, is anticipated to become a crucial component of the transportation infrastructure in densely populated regions. To meet the expected demand, there is a need for investigations into novel manufacturing and joining methods. This industry necessitates materials that are lightweight, durable, and amenable to high-rate production. One potential avenue under exploration is the utilization of thermoplastic composites. Thermoplastic composites offer high strength-to-weight ratios and can be manufactured efficiently and consistently at high production rates. Moreover, these enable the possibility of fastener-free joining methods, eliminating the need for traditional joining techniques which include fasteners (bolts, rivets, etc.) and/or adhesives which would increase the overall weight and reduce the individual structural integrity by introducing stress concentrations. The objective of this thesis is to build upon existing knowledge of fusion joining with thermoplastic composites and aerospace manufacturing, providing a road map for the induction welding of complex curved aerostructures.
The work presented in this thesis enhances the understanding of the induction welding process by deriving and leveraging coil geometric relationships to benefit the manufacturing of complex curved thermoplastic composite assemblies. Induction welding as a joining process suggests a fusion assembly method with the potential for high-rate and consistent manufacturing. Despite its many desirable manufacturing characteristics, the induction welding process has not yet been fully integrated into the production of larger primary aerostructures like the fuselage or wing structure. This challenge is associated with the complexity of controlling the joining parameters, reproducibility, and predictability of the induction welding process. Predicting temperature contours on thermoplastic composites is a challenging task, and it becomes even more complex when considering complex curved geometries. This thesis takes the fundamental induction welding principles and applies them for a complex curved fuselage demonstrator. A series of induction coil design experiments are conducted to aid in the coil design process. A vacuum bag setup was used with the induction tooling to support the pressure in lieu of a top tool. Overheating on the skin surface was seen at the intersection point of the frames and longerons. Skin deformation along the weld line was reduced by incorporating a fiber glass fabric sheet in the vacuum. However, it is evident that to increase the surface quality more, increasing the bag stiffness as well as improving surface cooling techniques need to be investigated. Partial welding and full interface welding was seen along each stiffener interface. More compliance in the pressure transferring elements is needed due to the complex curvature of the skin. It is concluded that the weld tooling showed promising results both in the design and the induction coils being used. The next step would be to improve the pressure distribution and surface quality along each component.
Rights
© 2024, Andrew Cole Cromer
Recommended Citation
Cromer, A. C.(2024). Towards the Induction Welding of Complex, Curved Thermoplastic Composite Structures. (Master's thesis). Retrieved from https://scholarcommons.sc.edu/etd/7685