Reinforcement costs

Table 9.39 Examplesof various types of E-glass fiber reinforcement costs and applications... 

Binary reinforcement Cost effective combination Better balance of stiffness,... 

Thus capital cost considerations reinforce the argument that the nonintegrated sequence with the lowest heat load is that with the lowest total cost. 

Carbon—carbon composites for rocket nozzles or exit cones are usually made by weaving a 3D preform composed of radial, axial, and circumferential carbon or graphite fibers to near net shape, followed by densification to high densities. Because of the high relative volume cost of the process, looms have been designed for semiautomatic fabrication of parts, taking advantage of selective reinforcement placement for optimum thermal performance. 

Hot pressing produces compacts that have superior properties, mainly because of higher density and finer grain size. Closer dimensional tolerances than can be obtained with pressing at room temperature are also possible. Hot pressing is used only where the higher cost can be justified. It has been usehil in producing reactive materials. One use is the combination of P/M and composites to produce hot-pressed parts that are fiber reinforced. 

In aerospace appHcations, low density coupled with other desirable features, such as tailored thermal expansion and conductivity, high stiffness and strength, etc, ate the main drivers. Performance rather than cost is an important item. Inasmuch as continuous fiber-reinforced MMCs deUver superior performance to particle-reinforced composites, the former are ftequendy used in aerospace appHcations. In nonaerospace appHcations, cost and performance are important, ie, an optimum combination of these items is requited. It is thus understandable that particle-reinforced MMCs are increa singly finding appHcations in nonaerospace appHcations. 

Proprietary blend formulations based on polysulfone, polyethersulfone, and polyphenylsulfone are sold commercially by Amoco Corporation to meet various end use requirements. The blends based on polysulfone are sold under the MINDEL trademark. A glass fiber-reinforced blend based on PES is offered under the trade name RADEL AG-360. This offers most of the performance characteristics of 30% glass fiber-reinforced polyethersulfone but at a lower cost. Two blend product lines are offered based on PPSF. These are designated as the RADEL R-4000 and R-7000 series of products. The former is a lower cost alternative to RADEL R PPSF homopolymer offering most of the performance attributes unique to PPSF. The R-7000 series of resins have been formulated for use in aircraft interiors for civil air transport. They exhibit a very high degree of resistance to flammabihty and smoke release. 

Many different thermosetting polymers are used in pultmsion, eg, polyester, vinyl ester, epoxy, and urethane. Reinforcements must be in a continuous form such as rovings, tows, mats, fabrics, and tapes. Glass fibers are the low cost, dominant composition, but aramid and carbon fibers are also used. 

Economic Benefits. The traditional costs of a product include raw materials, processing, overhead, and so forth. Designers and engineers considering potential composite appHcations cannot compare material costs only. Polymer composites, except for inexpensive fillers and small amounts of additives, consist mostly of resin and reinforcement, whose materials costs are usually higher than traditional materials. 

Fillers, eg, clays and whiting, are used to reduce cost or provide special properties. Fillers do not reinforce mbber deposited from latex, excepting to improve abrasion resistance. They are also used to increase viscosity for latex compound spreading suitabiUty. 

Nonfibrous Reinforcements. Because of the higher costs associated with nonasbestos fibers and the performance requirements needed in replacing asbestos, platy minerals such as mica and talc, and metal powders such as iron and copper, are being used as a portion of the total reinforcement package in NAOs. 

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