Abstract:
Modern-day military fighter aircraft, such as the FA-18 Hornet, the AV-8B Harrier, and the F-117 Stealth, all use significant amounts of high performance carbon fiber-resin composites in their primary structure. The installed cost for composites in these aircraft ranges from $625 to about $1100 per pound. While this is justified from a national defense perspective, other types of commercial air transportation, as well as land transportation vehicles, and other civilian primary structure applications cannot afford these prices. At the other end of the cost spectrum for structural polymeric composites are the Glasshopper railroad hopper car, which uses a filament-wound glass/polyester system at $16 - $25 per pound, and filament-wound GRP drainage pipe at $6 - S12 per pound.
In order to utilize the carbon-fiber systems in large volume structural applications, such as the transportation industry and other areas of the civilian infrastructure, the installed cost must be lowered to less than $50 per pound. If we look at a typical cost breakdown for high performance composite parts in the aerospace industry, we find that fabrication and assembly costs are the largest components. Additionally, carbon fibers are very expensive and contribute to a high material cost. There are three advantageous routes to reducing the cost of carbon fiber-based structural composites to less than $50 per pound. First, the cost of carbon fibers can be reduced significantly. Second, continuous low-cost processes can be developed for producing the final structure. And third, composites can be used as part of a hybrid design in which very inexpensive materials, like concrete, can be incorporated. NDE in the form of sensor technology is vital in all three areas.
In the area of continuous manufacturing of both carbon fibers and the final composite part, NDE/sensor technology plays a vital role. Without it, on-line control is impossible. In carbon fiber production, temperature, oxygen, and force sensors will be useful. In the processes of Continuous Resin Transfer MoldingTM and injected head filament winding, pressure, temperature, force, and chemorheological sensors will be required. All of the final parts will have the advantage of being smart by containing sensors that can monitor structural integrity during the lifetime performance of the park These sensors will be placed in the part during its fabrication and in some cases may well monitor both the vital processing parameters and the part integrity during its lifetime. When sensor technology of the type discussed at this conference is commercialized, we will have overcome the last technical barrier to affordable composite structures.
Source: Proceedings of the 'NDE applied to Process Control of Composite Fabrication' - Conference, 4-5 Oct 1994 St. Louis, Missouri. Publisher and Organizer: Nondestructive Testing Information Analysis Center (NTIAC) Texas Research Institute Austin, Inc. Austin, Texas [http://www.ntiac.com] [Buying the Proceedings]
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