Ceramic Fibers and Coatings Advanced Materials for the Twenty-First Century (1998) / Chapter Skim
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1 Introduction
1 Introduction
Pages 6-11
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From page 6... ...
The committee also has expertise in ceramic fiber economics, including cost analysis and the determination of the commercial potential of advanced materials. To accomplish the overall objective of identifying research directions to meet the material property requirements of advanced fibers and coatings for high-temperature ceramic composites, the committee took the following steps: · characterized the current state of the art in high temperature fibers and interface materials and identi 6 fled current domestic and foreign capabilities (both R&D and production capabilities)
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From page 7... ...
Embrittlement is most severe with cyclic loading beyond the proportional limit, whereupon matrix cracking occurs because oxygen that ingresses through the matrix cracks reacts locally with the fibers and fiber coatings to form oxide products. These reaction products suppress the internal friction mechanisms that otherwise impart toughness.
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From page 8... ...
Ceramic matrix composites (CMCs) are an attractive alternative because they maintain the refractory properties of monolithic ceramics and do not exhibit a catastrophic failure mode.
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From page 9... ...
Creep FIGURE 1-6 Single filament of boron nitride-coated Nippon Carbon Nicalon_ non-oxide ceramic fiber. Non-oxide fibers discussed in this report include polycrystalline SiC fibers and multiphase (amorphous or crystalline)
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From page 10... ...
With the recent development of oxide fibers with improved creep resistance, progress has been made on interface control in oxide systems. Initial approaches to fiber coatings for oxide composite systems (beyond the carbon and boron nitride approaches borrowed from the non-oxide composites)
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From page 11... ...
, an appropriate goal is the development of fiber bundles with failure strains that exceed 0.6 percent throughout the relevant temperature range for a specific application. These failure strains dictate a preference for low-modulus fibers, although overall stiffness requirements establish a minimum acceptable modulus for the fibers.
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