Hybrid ceramic matrix composites

W. A. Cutler, F. W. ZokandF. F. Lange, Mechanical BehaviourofSeveral Hybrid Ceramic-Matrix-Composite Laminates, 7. Am. Ceram. Soc. 79, 1825-1833 (1996). 

S. B. Haug, L. R. Dharani andD. R. Carroll, Fabrication of Hybrid Ceramic Matrix Composites, A/>p/. Comp. Mater. 1, 177-181 (1994). 

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.)... 

K. Igashira, Y. Matsuda, G. Matsubara, A. Imamura, Development of the Advanced Combustor Liner Composed of CMC/GMC Hybrid Composite Material, in High Temperature Ceramic Matrix Composites, W. Krenkel, R. Naslain, H. Schneider, eds., Wiley-VCH, Weinheim, New York, (2001) 789-796. 

FIGURE 10. Hybrid barium magnesium aluminosilicate glass-ceramic matrix composite with Nicalon fibre and SiC-whisker reinforcement. The white dots are SiC whiskers distributed in the glass-ceramic matrix. (Micrograph courtesy of Prof. K. Chawla, University of Alabama at Birmingham, USA). 

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). 

In composites, the matrix can be either polymeric, ceramic or metallic, hence, polymer matrix composites (PMC), ceramic matrix composites (CMC) or metal matrix composites (MMC). Obviously, the latter two structures are used for high temperature applications (>315 °C), where PMC are usually inadequate. In addition, MMC with proper electrical and thermal conductivities are also used in heat dissipation/electronic transmission applications. In addition to the general types of composites, some specific composites can also be of the type ceramic/metal/polymer or carbon matrix (CMC) or even hybrid composites (HC). 

Ceramic Matrix Composites (CMC) performed by a hybrid process is described in this paper. This process is based on (i) the chemical vapor deposition of carbon interphase on the fiber surface, (ii) the introduction of mineral powders inside the multidirectional continuous fiber preform and (Hi) the densification of the matrix by Spark Plasma Sintering (SPS). To prevent carbon fibers and interphase from oxidation in service, a self-healing matrix made of silicon nitride and titanium diboride was processed. A thermal treatment of 3 minutes at 1500 C allows to fully consolidate by SPS the composite without fiber degradation. The ceramic matrix composites obtained have an ultimate bending stress at room temperature around 300 MPa and show a self-healing behaviour in oxidizing conditions. 

J. MagnanL R. Pailler, Y. Le Petitcorps, L. Mailld, A. Guette, J. Marthe, and E. Philippe, Fiber-reinforced ceramic matrix composites processed by a hybrid technique based on chemical vapor infiltration, slurry impregnation and spark plasma sintering, J. Eurt. Ceram. Soc., 33, 181-190... 

Although the uses of ceramic fibres in composite structures lie mainly in ceramic-matrix and metal-matrix composites, where their outstanding chemical and thermal resistance are important, there are a few applications in organic polymers. Their relevant properties are low thermal expansion, low electrical conductivity, low dielectric constant, high stiffness, good compressive strength, and in most cases complete resistance to combustion. On the other hand they are very brittle, hard to process, and mostly considerably more expensive than carbon and para-aramid fibres. They have, for example, been used in hybrid structures with carbon and para-aramid and in electronic circuit boards. The fibres available or potentially available include alumina, combinations of alumina with... 

In the field of composite materials, inorganic-organic hybrid polymers offer great promise as precursors to ceramic matrix materials. In these applications, high purity ceramics are often not necessary and preceramic polymers allow the introduction of inorganic elements such as silicon and boron in quantities which can be directed by polymer structure and stoichiometry. 

Structural materials are usually classified into three groups polymers, metals, and ceramics. Their combinations are composites, which show unique properties. If the matrix has a multiphase stmcture or the reinforcement consists of more than one material, the resulting composite is called hybrid composite. Hybrid composites are at the peak of the pyramid in the hierarchy of structural materials due to their special properties. 

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