Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Rod – strand – filament or fiber
Patent
1997-12-17
2000-02-08
Turner, Archene
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Rod, strand, filament or fiber
4273722, 4273761, 4273762, 4274191, 4274192, 4274193, 4274342, 4274546, 4274432, 428375, 428378, 428432, 428697, 428698, 428704, C04B 35628
Patent
active
060226218
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention generally relates to composite articles. In particular, the invention relates to inorganic fibers having a mullite-containing coating and to ceramic matrix composite articles reinforced with said fibers.
BACKGROUND OF THE INVENTION
Fiber-reinforced ceramic matrix composites comprising glass-ceramic matrices are known in the art. Fiber-reinforced ceramic matrix composites are useful as structural elements in high temperature environments such as heat engines. For these and other applications, the materials to be employed must exhibit good strength and toughness at ambient as well as elevated temperatures.
An important problem which has been identified in silicon carbide fiber reinforced ceramic matrix composites, particularly after exposure to temperatures above about 800.degree. C. in an oxidizing environment, is that microcracks can form causing embrittlement. Instead of exhibiting increased toughness and strength after exposure to high temperatures, the materials become brittle and are subject to catastrophic breakage, rather than more gradual failure as is typical of the original material. These physical problems can be attributed, in-part, to the effect of the interface between the silicon carbide fibers and the ceramic matrix composite.
Physical testing of ceramic matrix composites, embrittled during or subsequent to high temperature exposure, shows decreases in fracture toughness through changes in the fracture properties of the material, leading to a degradation of the material. Thus, the predominant fracture mode changes from one characterized by fiber pullout from the matrix to one wherein woody fracture, or ultimately, brittle fracture occurs. Woody fracture surfaces display some crack propagation parallel to the stress axis, indicating localized shear failure without fibrous pullout, while brittle fracture surfaces display merely planar fracture surfaces as the composite exhibits no plastic deformation.
The onset of brittle fracture behavior in these composites typically occurs in conjunction with significant reductions in fracture toughness. One indicator of this reduced toughness is a drop in the extent of strain of sample elongation observed above the so-called microcrack stress point of the material. Among the factors believed to influence fracture toughness are fiber debonding and fiber pullout behavior, including the degree of frictional resistance to fiber pullout from the matrix, as well as crack deflection occurring in the matrix and at the fiber-matrix interface. Modifications to the matrix or fiber reinforcement can significantly aid in the development of composites exhibiting good high temperature fracture toughness and strength.
It is known to provide coatings on reinforcement fibers to be incorporated in composite materials to modify the behavior of the materials therein. For example, boron nitride coatings have been applied to silicon carbide fibers or other fibers that are subsequently incorporated in ceramic matrix materials such as SiO.sub.2, ZrO.sub.2, mullite and cordierite (see e.g., U.S. Pat. No. 4,642,271 (Rice)).
It is established that the interface between fibers and the matrix is critical to the mechanical properties of brittle-matrix composites. In particular, the debonding and frictional characteristics of the interface control the mode of fracture (multiple cracking vs. single crack), and mechanical properties such as fracture toughness. Desired interfacial properties are usually achieved by the incorporation of a coating between the fiber and matrix.
For example, Beall et al., European Patent Application Publication Number 366234 A1, disclose ceramic matrix composite articles comprising a ceramic, glass-ceramic or glass matrix and a fiber reinforcement phase disposed within the matrix. The fiber reinforcement phase consists of amorphous or crystalline inorganic fibers, wherein there is provided, on or in close proximity to the surfaces of the inorganic fibers, a layer of sheet silicate crystals. The layer of sheet silicate cr
REFERENCES:
patent: 4543345 (1985-09-01), Wei
patent: 4642271 (1987-02-01), Rice
patent: 4806428 (1989-02-01), Cooper et al.
patent: 4935387 (1990-06-01), Beall et al.
patent: 5164229 (1992-11-01), Hay
patent: 5227199 (1993-07-01), Hazlebeck et al.
patent: 5652188 (1997-07-01), Chyung et al.
Derwent Publications Ltd., London, GB; AN 79-75925B & JP 54 113 609 (Toshiba Monoflux), Sep. 5, 1979.
Clegg, W. J. et al., "A Simple Way to Make Tough Ceramics", Nature, 347, pp. 455-457, Oct. 1990.
Evans, A. G., "Perspective on the Development of High-Toughness Ceramics", J. Am. Cerm. Soc., 73 [2], pp. 187-206, (1990) (No Month).
Harmer Mark Andrew
Jagota Sujata
McCarron, III Eugene Michael
E. I. Du Pont de Nemours and Company
Turner Archene
LandOfFree
Mullite-containing coatings for inorganic fibers and ceramic mat does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Mullite-containing coatings for inorganic fibers and ceramic mat, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Mullite-containing coatings for inorganic fibers and ceramic mat will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1679385