Fiber-Reinforced Metal Matrix Composites

Discontinuous fiber MMCs are isotropic and are superior in terms of specific strength, elastic modulus, toughness, and thermal conductivity compared to conventional alloys. They are used for brackets and fittings that are subject to multiaxial loads. The ability to engineer the CTEs of discontinuously reinforced aluminum (DRA) composites makes it possible to save substantial weight by replacing Invar or Kovar in critical design situations where a low GTE material is needed. 

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Strength. Prediction of MMC strength is more compHcated than the prediction of modulus. Consider an aligned fiber-reinforced metal-matrix composite under a load P in the direction of the fibers. This load is distributed between the fiber and the matrix ... 

Fiber-reinforced composites, subcritical damage mechanisms in, 16 188 Fiber-reinforced metal-matrix composites, 16 171... 

Chou. T.W.. Kelly, A. and Okura, A, (1985). Fiber reinforced metal matrix composites. Composites. 16, 187-206... 

Doghri, H., Jansson, S., Leckie, F.A. and Lemaitre (1990). Optimization of interface layers in the design of ceramic fiber reinforced metal matrix composites. NASA CR-185307. 

Jansson. S. and Leekie, F.A. (1992). Reduction of thermal stresses in continuous fiber reinforced metal matrix composites with interface layer. J. Composite Mater. 26, 1474-1486. 

Ceramic-Fiber Reinforced Metal-Matrix Composites (MMCs)... 

Bouix J, Berthet MP, Bosselet F, Favre R, Peronnet M, Viala JC, Vincent C, Vincent H, Interface tailoring in carbon fibers reinforced metal matrix composites. Journal de Physique, IV 7(C6), 191-205, 1997. 

An important milestone in inorganic fiber reinforced metal matrix composite technology was reached recently when Toyota Motor Corporation announced the commercial production and use of the world s first metal matrix composite piston insert for the Toyota 2L Turbo Diesel Engine Car (I7,l8) (Figure 26). The diesel piston insert made from commercial short alumina-siliea fiber-reinforced aluminum matrix composite significantly improves wear, heat resistance and... 

Figure 28 compares the perfomance of alumina-silica fiber-reinforced aluminum matrix composites vith competitive ceramics and imreinforced aluminum alloys. Inorganic fiber reinforced metal matrix composites appear to have the best combination of properties for piston insert applications. 

Fig. 14. Micrograph of a C-fiber reinforced Si3N4 matrix composite prepared by directed metal oxidation. From Johnson [52],...

Metal matrix composites with SiC-reinforcements are obtained by melt-infiltration or powder metallurgical routes like hot-isostatic pressing. SiC-fibers in metal matrix composites are often coated to prevent reaction... 

At manufacturing level, chemical reactions between the matrix and the liber produce an interface zone of different mechanical properties from the two phases producing it [158]. The load of a composite is usually transferred through the interface between the matrix and the fiber, and the toughness of the composite is determined. Karpur et al. measured ultrasonically the shear stiffness coefficient of the interface in fiber reinforced metal matrix and ceramic matrix composites [158]. They claim that the significance of the quantification of the shear stiffness coefficient of the interface is that the clastic property of the interface can be used as a basis for composite life prediction. 

As structural materials for high-temperature components in advanced engines forpower and propulsion, fiber-reinforced ceramic matrix composites (CMC) offer a variety ofperfor-mance advantages overthe best metallic alloys with current stractural capability to 1100°C. 

One approach for fabricating fiber reinforced ceramic matrix composites is the directed oxidation of metals, a process first introduced by Lanxide Corporation [1, 2] and later used successfully to produce turbine engine and aerospace components. Rights to the DIMOX technology, as it was identified, were ultimately acquired by Power Systems Composites, L.L.C., a subsidiary of the Power Systems business of the General Electric Company. 

A.S. Fareed, Ceramic Matrix Composite Fabrication and Processing Directed Metal Oxidation, Handbook on Continuous Fiber Reinforced Ceramic Matrix Composites, ed. R.L. Lehman, S.K. El-Rahaiby Jr and J.B. Wachtman, Jr., ClAC/ACers, 301-324 (1995). 

Diefendorf RJ, Continuous carbon fiber reinforced carbon matrix composites, Reinhart TJ ed.. Engineered Materials Handbook, Vol 1, Metals Park, OH, ASM International, 911, 1987. 

A number of useful reviews detailing composite fabrication have been written [43,116 122]. The general methods for forming carbon fiber reinforced metal matrix... 

Hughes Aircraft [243] patented a graphite fiber reinforced sihca matrix composite, comprising of carbon fibers bonded together in a matrix of sihca, boron phosphate and p-spodumene modified with a minor amount of an alkahne earth metal oxide. The extremely low (nearly zero) coefficient of thermal expansion coupled with the moderate thermal conductivity and low density of the composite make the composite particularly suitable as a substrate material for high energy laser mirrors. 

Farced, A. S., Schiroky, G. H., and Kennedy, C. R. (1993). Development of BN/SiC duplex fiber coatings for fiber-reinforced aluminia matrix composites fabricated by directed metal oxidation. Ceram. Eng. Sci. Proc. 18 794-801. 

Most borides actually form a mixed bor-ia-metal oxide scale and will be discussed in Section 7.7.1.1. However, boron nitride (BN) and boron carbide (B4C) form a pure boria scale. BN has been used for many years as a crucible material in vacuum and is of recent interest as a fiber coating for continuous fiber reinforced ceramic matrix composites. The most common form of BN is a hexagonal, graphite-like structure. This discussion will be confined to oxidation of hexagonal BN. In pure oxygen BN oxidizes as ... 

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