New Materials for Next-Generation Commercial Transports (1996) / Chapter Skim
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2 Structural Concepts
2 Structural Concepts
Pages 11-25
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From page 11... ...
Therefore, FAA participation early in the design cycle in which new material, structural concepts, and manufacturing methods are being considered will illuminate the appropriate certification and safety-of-flight issues at the point at which the most effective solutions can be applied. The evaluations required to qualify a new material and show that manufacturing processes are robust enough to commit to production include: · Preliminary evaluations: initial evaluation of static mechanical properties?
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From page 12... ...
Innovation in structural design will take advantage of new low-cost processes, reduced part counts, and consolidated processing steps. Innovative structural concepts that enable low-cost processing methods, including integral stiffening, concepts, net-shape processing (e.g., metal casting and resin transfer molding of composites)
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From page 13... ...
MATERIALS,PROCESSES,ANDSTRUCTURALCONCEPTS a' C a_ I= an in 1 ~ N In ~7 as ~ ~C _ ~ AS U)
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From page 15... ...
New structural concepts will evolve as a result of requirements associated with these applications. This chapter describes design and technology issues for innovative structural concepts, as well as key design issues in the development of advanced metallic fuselage, composite wing, and composite fuselage components.
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From page 16... ...
Integrally stiffened components can be produced from metallic alloys as well as polymeric composites. Metallic alloys are fabricated into integrally stiffened components using machining and chemical milling or net-shape (or nearnet-shape)
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From page 17... ...
New concepts for machining of contoured panels and core-facesheet stabilization methods may be effective in reducing the cost of producing sandwich panel constructions. Optimization codes for durability and damage tolerance: Improved analytical codes for durability, damage tolerance, and weight optimization with a capability for incorporating thermal and acoustical properties of sandwich constructions would provide added confidence in structural designs and could be used to develop material property goals for lona-term research.
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From page 18... ...
With all this success, however, most airframe primary structure manufactured in the United States and Europe consist of mechanically fastened aluminum skin/stringer construction. Historically, welded structures for primary applications were not considered to be weight competitive and had poor fatigue behavior.
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From page 19... ...
The improved fatigue performance is attributed to load transfer from the metal layers to the stronger, unbroken fibers that bridge the advancing crack and restrain further opening. Potential aircraft applications envisioned for hybrid laminates include lower wing skins, fuselage skins, tear straps, and empennage structures.
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From page 20... ...
Repair and maintenance procedures must be developed and proven for large-scale laminate components. Smart Materials and Structures Smart, or adaptive, materials and structures are a recent concept that is still rapidly evolving and offers significant benefits in a range of applications including, aircraft design and performance.
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From page 21... ...
Design, fabrication, and testing of an advanced metallic fuselage structure is needed to validate reduced manufacturing costs and improved structural efficiency for new candidate materials and innovative design concepts. In general, cost savings derive from reducing labor-intensive processes and lowering part count for major assemblies.
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From page 22... ...
Emerging manufacturing technologies for composite fuselage structures are presented in figure 2-3. As can be seen in the figure, development emphasis is being placed on automated techniques such as advanced tow placement for skin fabrication, textile preform and RTM (resin transfer molding)
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From page 23... ...
Post-Buc ed Hoop Tension and Structure ~(Damage tolerance) Post-lmpact Strength Ground \ Handling Major Load Redistnbubon Equipment from Keel Bearn Damage FIGURE 2-2 Structural design drivers for a composite fuselage.
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From page 24... ...
In addition, hybrid laminates can be produced using standard metal fabrication processes and have improved resistance to absorbed moisture and impact damage compared with polymer-matrix composites. Potential aircraft applications envisioned for hybrid laminates include lower wing skins, fuselage skins, tear straps, empennage structures and applications involving acoustic fatigue.
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From page 25... ...
commi~co does not believe Phi systems involving Dive medals will be av~l~le, practical, Ed sufficiently low in cost to enable ~plic~iop on noxt-genoradon common 23 aircraft. Howovor, the sensing- and sign~-procossing c~abUides could be ~ad~ far home moni~ng of smacks or mc~uIomont of service environments conditions.
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