Current industry practice separates the design of an air vehicle's propulsion system from the design of its airframe. This practice causes many problems and inefficiencies particularly for advanced exhaust nozzle designs. It results in redundant aircraft structure to be insulated and shielded from the engine thermal and acoustic emanations. Perhaps, most importantly, it causes buckling and cracking at the joint interfaces where the thermally induced stresses are reacted. The critical joint interfaces are the co-cured/bonded joints between layers of the dissimilar materials and the mechanical joints between structural components. Northrop Grumman's concept is to modernize the design, analysis, and construction of future high performance aircraft by integrating the exhaust nozzle/exhaust washed structural components into the primary airframe structure through a combination of organic and ceramic matrix composite materials. Designing bolted and bonded joints to carry induced loads efficiently, then, is critical to an integrated structural approach. Northrop Grumman has evolved a variety of approaches to transfer loads, including co-bonding of dissimilar materials and unique joint designs. Ceramic matrix composite/AFR700B bolted and bonded joints have been identified as a critical need, and under Air Force-contracted research, joints have been designed and analyzed and will be fabricated. Sub-element testing, including static and fatigue, will validate the design and analytical methodologies. Durability and maintainability will be validated through testing and nondestructive evaluation. Trade-off analysis performed on the bolted and bonded joints will address structural efficiency, reliability, supportability, and battle damage tolerance.
Attachment of ceramic matrix composites to AFR700B composites for exhaust washed airframe structures
1997
9 Seiten, 12 Bilder, 3 Tabellen
Aufsatz (Konferenz)
Englisch
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