Fiber Reinforced Ceramic Matrices

A ceramic is an inorganic non-metallic solid prepared from powdered materials and can loosely be divided into cement, mortar and concrete, glass and glass ceramics, traditional ceramics, and what may be termed advanced (i.e. high performance, technical, engineering, or fine) ceramics. 

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Fig. 14. Failure mechanisms for continuous fiber reinforced ceramic matrices (58).

Evans, A.G. (1989). The mechanical performance of fiber-reinforced ceramic matrix composites. Mater. Sci. Eng. A 107, 227-239. 

As noted earlier, CVl is nsed primarily to form ceramic-fiber-reinforced ceramic matrix composites. The most common of these combinations is SiC fiber/SiC matrix composites. One commercially available product has a two-dimensional 0/90 layup of plain weave fabric and fiber volume fraction of about 40%. This same composite can be fabricated with unidirectional fibers and with 45° architectures. The most commonly used SiC fiber for the preforms is Nicalon , the mechanical properties for which were provided earlier in Section 5.4.2.7. A number of other carbide and nitride fibers are also available, including Si3N4, BN, and TiC. Preform geometries can be tailored to the application in order to maximize strength and toughness in the direction of maximnm stresses. The reactions used to form the matrix are similar to those used in CVD processes (cf. Section 7.2.4) and those described previously in Eq. (3.105). 

Access to phase pure silicon nitride materials via processable precursors is limited to just three approaches. The first, shown in reaction 6, provides one of the first oligomers exploited as a preceramic polymer24,253. This simple polysilazane, containing only Si, N and H, is known to be relatively unstable and will crosslink on its own to give intractable gels. Furthermore, it does not offer the 3Si I4N stoichiometry required for Si3N4. Nonetheless, it is useful as a binder and for fiber-reinforced ceramic matrix composites (CMCs)31. 

F. Hurwitz, Ceramic Fiber-Reinforced Ceramic Matrix Composites, in International Encyclopedia of Composites, Vol. 1, VCH Publishers, New York, NY, 1990, p. 297. 

Again, the above crack kinking and branching criteria are limited to isotropic homogeneous material, which for all practical purposes will include particulate/whisker-filled ceramic matrix composites. No equivalent criterion exists for orthotropic/inhomogeneous material. Limited experimental results show that self-similar crack extension is a rare phenomenon in fracture of fiber-reinforced ceramic matrix composites and thus the kinking and branching criterion, if developed, must necessarily be a three-dimensional one. 

J. Lankford, Dynamic Compressive Fracture in Fiber-Reinforced Ceramic Matrix Composites, Material Science and Engineering, A107, 261-268 (1989). 

Fatigue Behavior of Continuous Fiber-Reinforced Ceramic Matrix Composites... 

The model proposed by Rouby and Reynaud46 represents the first systematic approach for understanding how the microstructural damage governs the fatigue life of continuous fiber-reinforced ceramic matrix composites. This model will be used to explain various aspects of fatigue failure in the remaining portion of this chapter. 

Experimental studies of the influence of stress ratio on elevated temperature fatigue life have been conducted by Suresh71 for whisker-reinforced AI2O3 (see Chapter 7 by Suresh for a discussion of the fatigue behavior of whisker-reinforced ceramics). In this section, the influence of stress ratio on the fatigue life of continuous fiber-reinforced ceramic matrix composites is discussed. 

F. Hild, J.-M. Domergue, F. A. Leckie, and A. G. Evans, Tensile and Flexural Ultimate Strength of Fiber-Reinforced Ceramic-Matrix Composites, to be published. 

H. E. Kautz and R. T. Bhatt, Ultrasonic Velocity Technique for Monitoring Property Changes in Fiber-Reinforced Ceramic Matrix Composites, Cer. Eng. Sci. Proc., 12[7-8], 1139-1151 (1991). 

Bowman, K. J. et al. (Ed.) 1995. Handbook on Continuous Fiber-Reinforced Ceramic Matrix Composites. Am. Ceram. Soc., Westerville, Ohio. 

Figure 5.44b is reprinted from Composites Science and Technology, Vol. 59, F Lamouroux, S Bertrand, R Pailler, R Naslain and M Cataldi, Oxidation-resistant carbon-fiber-reinforced ceramic-matrix composites, pp. 1073-1085,1999, with permission from Elsevier. 

Wider use of fiber-reinforced ceramic matrix composites for high temperature structural applications is hindered by several factors including (1) absence of a low cost, thermally stable fiber, (2) decrease in toughness caused by oxidation of the commonly used carbon and boron nitride fiber-matrix interface coatings, and (3) composite fabrication (consolidation) processes that are expensive or degrade the fiber. This chapter addresses how these shortcomings may be overcome by CVD and chemical vapor infiltration (CVI). Much of this chapter is based on recent experimental research at Georgia Tech. 

Zirconium dioxide, Zr02, displays a variety of desirable properties including hardness, chemical durability and corrosion resistance. It is employed in numerous applications such as coatings for cutting tools, optical filters, thermal barrier coating, interfacial coatings in fiber reinforced ceramic matrix composites, dielectric films in microelectronics [24] and other applications such as mirrors [25] and sensors [26]. 

As fiber is a primary component in continuous fiber reinforced ceramic matrix composites, its characteristic is an important factor that confines the thermal conductivity of the composites. The ideal SiC fiber should be highly crystalline, oxygen-free, and stoichiometric. As shows in Table I,... 

A.S. Farced, C.C. Cropper, and B.R. Rossing, Joining Techniques for Fiber-reinforced Ceramic-matrix Composites, Ceram. Eng. Sci. Proc., 20[4], 61-70 (1999). 

R.M. Rocha, C.A.A. Cairo, M.L.A. Graca, Formation of carbon fiber-reinforced ceramic matrix composites with polysiloxane/silicon derived matrix. Materials Science and Engineering A 437(2006) 268-273... 

These fibers have high tensile strength and heat resistance. In recent years, SiC fibers or their fabrics have been used to prepare fiber-reinforced ceramic-matrix composites. Such composites have high strength and high fracture toughness, even at elevated temperatures [5,6], and are a promising class of... 

Wagner O (1991) Diploma Thesis, University of Bonn, Germany Baldus HP, Passing G, Sporn D, Jansen M, Goring J (1997) Key Eng Mater 127/131 177 DiCarlo JA, Dutta S (1995) Continuous ceramic fibers for ceramic matrix composites. In Lehmann R, El-Rahaiby S, Wachtmann J (eds) Handbook on Continuous Fiber Reinforced Ceramic Matrix Composites. Ceramic Information Analysis Center, Purdue University, IN, p 140... 

FIGURE 18.17 Schematic stress-strain curve for a tough fiber-reinforced ceramic matrix composite. 

J.A. DiCarlo and S. Dutta, Continuous Ceramic Fibers for Ceramic Composites, Handbook On Continuous Fiber Reinforced Ceramic Matrix Composites Eds R. Lebman, S. El-Rahaiby, and J. Wachtman, Jr., CIAC, Purdue University, WestLafayette, Indiana, 1995, p. 137—183. 

J. C. McNulty, F. W. Zok, Application of weakest-link fracture statistics to fiber-reinforced ceramic-matrix composites, 7. Am. Ceram. Soc. 80 1535-1543 (1997). 

J. W. Holmes, J-L. Chermant, Creep behaviour of fiber reinforced ceramic matrix composites, in High Temperature Ceramic Matrix Composites, R. Naslain et al. eds., Woodhead, UK (1993), pp. 633-647. 

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. 

C. A. Nannetti, A. Borello and D. A. de Pinto, C-Fiber Reinforced Ceramic Matrix Composites by a Combination of CVI, PIP and RB, High Temperature Ceramic Matrix Composites (Eds. W. Krenkel, R. Naslain, H. Schneider), WILEY-VCH, Weinheim, Germany (2001), p. 368-374. 

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