Carbon matrix composite microstructure

A ceramic matrix composite or CMC is composed of two or more solids, the matrix of which consists of a ceramic material or carbon. The crystalline, ceramic matrix is moulded and/or densified at a temperature of at least 1000 K. To the matrix one ormore solid inorganic substances are added, e.g. in the form of particles or fibres in order to alter the (thermo) mechanical properties of the pure matrix. In the composite s microstructure these additives can still be distinguished by their chemicalcomposition or geometry even after they have undergone a temperature treatment of at least 1000 K. 

Ning, J., Zhang, J., Pan, Y. and Guo, J., Fabrication and mechanical properties of Si02 matrix composites reinforced by carbon nanotube , Materials Science and Engineering, A Structural Materials Properties, Microstructure and Processing, 2003, A357, 392-396. 

FIGURE 12.11 Improvements of the mechanical properties of three-dimensional reinforced CMCs by hybrid infiltration routes (a) R.T. flexural stress-strain plots for a three-dimensional carbon fiber reinforced composite before and after cycles of infiltration (comparison between eight cycles with zirconium propoxide and fonr cycles pins a last infiltration with aluminum-silicon ester (b) plot of the mechanical strength as a fnnction of the final open porosity for composites and matrix of equivalent porosity, before and after infiltration (Reprinted from Colomban, R and Wey, M., Sol-gel control of the matrix net-shape sintering in 3D reinforced ceramic matrix composites, J. Eur. Ceram. Soc., 17, 1475, 1997. With permission from Elsevier) (c) R.T. tensile behavior (d) comparison of the R.T. mechanical strength after thermal treatments at various temperatures. (Reprinted from Colomban, R, Tailoring of the nano/microstructure of heterogeneous ceramics by sol-gel routes, Ceram. Trans., 95, 243, 1998. With permission from The American Ceramic Society.)... 

Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) are used to study the morphology and microstructure of carbon-Ti02 composites. In the case of CNT-Ti02 composites, observations on CNT embedded in Ti02 matrix [111,115] and fine coating of Ti02 on a CNT surface [107,112-114,116,117] are reported. 

P. M. Benson, K. E. Spear and C. G. Pantano, Thermochemical Analysis of Interface Reactions in Carbon-Fiber Reinforced Glass Matrix Composites, in Ceramic Microstructures 86. Role of Interfaces, ed. by J. A. Pask and A. G. Evans, Plenum Press, New York (1987) 415 25. 

Figure 14.8 Effect of deposition conditions on the microstructure of pyrolytic carbon matrix deposition from propane. Source Reprinted with permission from Oh SM, Lee JY, Structure of pyrolytic carbon matrices in carbon-carbon composites, Carbon, 26(6), 763-768, 1988. Copyright 1986, Elsevier.

Benson PM, Spear KE, CG Pantano, Thermochemical analysis of interface reactions in carbon-fiber reinforced glass matrix composites, JA Pask, Evans AG, eds.. Ceramic Microstructures 86 -Role of Interfaces, Plenum Press, New York, 415, 1987. 

Cheng HM, Akiyama S, Kitahara A, Kobayashi K, Zhou BL, Behaviour of carbon-fiber reinforced Al-Si composites after thermal exposure. Mater Sci Technol, 8(3), 275-281, 1992. Friler JB, Argon AS, Cornie JA, Strength and toughness of carbon fiber reinforced aluminum matrix composites. Mater Sci Eng A—Structural Materials Properties Microstructure and... 

Xu Y, Cheng L, Zhang L, Yan D, Mechanical properties and microstructural characteristics of carbon fibre reinforced silicon carbide matrix composites by chemical vapour infiltration, Niihara K, Nakano K, Sekino T, Yasuda E eds.. Ceramic Society of Japan, High Temperature Ceramic Matrix Composites III, Proc 3rd Int Conf, Osaka, Sep 6-9 1998, 73-16, Key Eng Mater, Vol 164-165. 

The SiC-Si matrix composite contains besides SiC fibrous particles some residual non-reacted carbon fibre material. Due to the highly anisotropic microstructure and anisotropy of elastic properties of the carbon fibres their presence gives rise to a high anisotropy of the Young s moduli. At a 22.3% content of carbon fibres the ratio is as high as 45.8% while at... 

At RT, thermal conductivities of carbon fiber composites with high tensile fibers differ from those of high modulus fibers and are much higher than the thermal conductivity of the epoxy matrix. Below 7 K, they become similar within 25% and lower than the thermal conductivity of the epoxy matrix (37,47). The similarity is owing to the fact that at low temperatures only long phonon wavelengths are activated they cannot resolve different graphite microstructures of different carbon fiber types which are dominant at RT (36,43). In most cases, the specific heat of composites is lower than that of the polymeric matrix. 

Fig. 9.1 Top view on two variants of C3 materials. The carbon fibers (a) themselves exhibit a complex inner microstructure that needs carful optimization for strength and stability. The isotropic filler phase (b) should be free of pores and other weak points caused by uneven distribution in the composite body. The ordered graphitic BSU (c) can provide a very strong but still flexible anchoring of the fibers in the isotropic matrix.

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