November 11, 2024-Karen Taminger, NASA Langley Research Center
November 11, 2024
4:00 p.m.
Room: Torgersen Hall 2150
Speaker: Karen Taminger, NASA Langley Research Center
Faculty Host: Dr. Rakesh Kapania
"Demonstration of How Manufacturing Innovations Challenge Conventional Structural Design"
Abstract: For more than 100 years, aircraft have been built using riveted aluminum structures. Aside from refining aircraft designs for better aerodynamic efficiency, improving alloys, and automating assembly steps, aluminum fuselage fabrication remains largely unchanged from the early days of aviation. The intent of the lightweight metallic fuselage demonstration undertaken in NASA’s Advanced Air Transport Technology project was to demonstrate advanced forming and joining processes that change the design paradigm to achieve high-rate manufacturing in addition to reducing manufacturing time and cost.
Over the past decade, researchers at NASA Langley Research Center have studied the potential to modify the flow forming process to produce near-net shaped cylinders that are integrally stiffened along the cylinder axis for space launch vehicles. The ability to produce integral stiffeners in a formed cylinder replaced machining thick plate and welding steps to eliminate > 500,000 pounds of machining chips and nearly 0.5 miles of welds to produce one aluminum cryogenic storage tank the size of the Space Shuttle external tank. The flow forming process, called the Integrally Stiffened Cylinder (ISC) process, was successfully demonstrated up to 10 feet diameter, laying the groundwork for the current investigation for metallic fuselage structures.
Using the ISC process as the starting point for reconsidering the design of a metallic fuselage eliminates hundreds of thousands of holes and rivets, significantly reducing assembly time and crack initiation sites in the fuselage structure. However, the ISC process is currently not configured to produce circumferential ring frames for carrying fuselage internal pressure loads. A trade study was performed to assess existing and advanced manufacturing processes, including additive manufacturing, forming, and welding. The approach with the lowest barriers to success while simultaneously improving manufacturing time and cost was to use formed ring frame segments attached to the ISC via Refill Friction Stir Spot Welding (RFSSW). The RFSSW process is five times faster than drilling, reaming, and riveting and provides similar mechanical performance. Finishing the fuselage structure with conventional windows, floor beams, and floor panels can then be accomplished using conventional assembly methods, maximizing reuse of existing capabilities on an aircraft assembly factory floor.
Structural analyses were performed to assess and optimize the skin and stiffener geometric variables, and a cost benefit and manufacturing rate analysis was performed to compare against the current state-of-the-art for single aisle transport class aircraft. The resulting structure offered a weight reduction that rivals current graphite-epoxy composite fuselage structures, with a manufacturing rate close to double current metallic and six times faster than current composite manufacturing practices. Durability and damage tolerance of a single-piece structure still needs to be assessed, but integral airframe structural work in the past revealed geometric features to blunt or turn cracks offering promise that integral structures can meet stringent aircraft durability requirements. Furthermore, aluminum fuselage structures may be inspected and repaired using conventional procedures and technicians. Finally, pursuit of advanced manufacturing processes for future aluminum fuselage structures minimizes waste and the structure is 100% recyclable at the end-of-life for maximum sustainability.
Bio: Ms. Karen Taminger is a Senior Materials Research Engineer at NASA Langley Research Center in the Advanced Materials and Processing Branch. She currently serves as a technical lead for structural efficiency in transport aircraft and has led development of the Electron Beam Freeform Fabrication (EBF3) technology for high-performance, low-cost fabrication of metallic structures for various aerospace applications. She also helped establish new flow forming and other wire additive manufacturing process capabilities at NASA Langley over the past several years. Karen earned her BS in Honors from Virginia Tech in 1989, majoring in Materials Engineering, and her MS degree from Virginia Tech in 1999 in Materials Science and Engineering. She has been employed at NASA Langley Research Center since 1986.