Carbon matrix composite

Carbon Composites. Cermet friction materials tend to be heavy, thus making the brake system less energy-efficient. Compared with cermets, carbon (or graphite) is a thermally stable material of low density and reasonably high specific heat. A combination of these properties makes carbon attractive as a brake material and several companies are manufacturing carbon fiber—reinforced carbon-matrix composites, which ate used primarily for aircraft brakes and race cats (16). Carbon composites usually consist of three types of carbon carbon in the fibrous form (see Carbon fibers), carbon resulting from the controlled pyrolysis of the resin (usually phenoHc-based), and carbon from chemical vapor deposition (CVD) filling the pores (16). 

Carbon-matrix composites, 26 751 Carbon microbeads, phenolic resins in,... 

Hatta, H., Aoki, T., Kogo, Y., Yarii, T., (1999), High-temperature oxidation behavior of SiC-coated carbon fiber-reinforced carbon matrix composites , Composites Part A, 30, 515-520. 

Carbon matrices are more suitable than polymers ones for applications at temperatures of 250 to 600°C. Above 600°C they are, however, (as are the C-fibers as such) only utilizable in inert atmospheres. C-fiber reinforced carbon matrix composites are particularly used in aircraft brakes, in fusion reactors and as a substitute for monolithic graphite. In addition they are utilized in the medical sector (implants), in furnace construction (heaters) and in energy conversion (heat exchangers). The market for carbon fiber/carbon matrix composites in 1993 was estimated to be ca. 250 t. 

The forced flow-thermal gradient CVI process (FCVI) has been shown to permit the rapid consolidation of SiC matrix composites. Recently, the FCVI process has been extended to the fabrication of carbon fiber-carbon matrix composites. Using 2D carbon cloth preforms, composite disks 0.8 cm thick have been fabricated in less than three hours a small fraction of the time required for either the resin/pitch or conventional CVI processing. Further, the FCVI process facilitates the incorporation of oxidation inhibitors within the carbon matrix and may permit obtaining a preferred crystallographic orientation that yields the high thermal conductivity required for thermal management applications. 

Figure 6-18. Processes for fabrication of carbon fiber-carbon matrix composites.

Figure 6-26. Polarized light micrograph showing carbon fiber-carbon matrix composite prepared by the FCVI process. The 7-pm diameter fibers serve as a scale.

E. Tani, K. Shobu, and K. Kishi, Two-dimensional-woven-carbon-fiber-reinforced Silicon Carbide/Carbon Matrix Composites Produced by Reaction Bonding, J. Am. Ceram. Soc., 82 [5] 1355-57(1999). 

Another type of classification can be done on the basis of filler or reinforcing agent used namely polymer matrix composites (PMCs), metal matrix composites (MMCs), ceramic matrix composites (CMCs), carbon-carbon matrix composites (CCCs), intermetallic... 

V. I. Trefilov, Ceramic- and Carbon-Matrix Composites, Chapman Hall (1995). 

A. E. Rutkovskij, P. D. Sarkisov, A. A. Ivashin and V. V. Budov, Glass-Ceramic-Based Composites, in Ceramic- and Carbon-Matrix Composites, V. I. Trefilov ed.. Chapman and Hall, London (1995) 255-285. 

Boron nitride derived from the borazine oligomer has been successfully used to replace the carbonaceous matrix in carbon fiber/carbon matrix composites (C/C) [15,18]. The carbon fiber/boron nitride matrix composites (C/BN) exhibit improved oxidation resistance over the C/C. Excellent mechanical strength and toughness have also been observed in the C/BN. As shown in Figure 2.16, both the flexural strength and modulus of pitch carbon fiber/BN specimens actually increase with extended heat treatment [18]. 

Composites usually consist of a reinforcing material embedded in various matrices (binder). The elfective method to increase the strength and to improve the overall properties of composites is to incorporate dispersed phases into the matrix which can be an either polymer or engineering materials such as ceramics or metals. Hence, metal matrix composites (MMCs), ceramic matrix composites (CMCs) and polymer matrix composites (PMCs) are obtained. Besides, hybrid composites, metal/ceramic/polymer composites and carbon matrix composites can also be obtained. MMC and CMC composites are developed to withstand high temperature applications. MMCs are also used in heat dissipation/electronic transmission applications due to the conductive nature of metals (electrically and thermally). 

Carbon matrix composites are composed of a carbon matrix into which reinforcing carbon fibres are embedded. They are commonly referred to as carbon-carbon (C-Q composites. Fibres in the C-C composites can be either continuous or discontinuous. 

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

Gunawan N, Seraphin S, Structural and compositional characterization of carbon fiber carbon matrix composites, Microscopy Research and Technique, 38(5), 544, 1997. 

Tani OE, Shobu K, Kishi K, Umebayashi S, Two-dimensional-woven-carbon-fibre-reinforced sihcon carbide /carbon matrix composites produced by reaction bonding, J Am Ceramic Soc, 82(5), 1355 1357, 1999. 

Tzeng SS, Lin WC, Mechanical behavior of two-dimensional carbon fiber fabrics reinforced carbon matrix composites. Key Eng Mater, 145(1,2), 877-882, 1998. 

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