A preferred composite which is useful at temperatures in excess of about 0.degree. C. comprising a ceramic matrix and 40-60% on volume basis of coated and uncoated fibers embedded in the matrix generally parallel to each other and in a controlled arrangement; the matrix is selected from the group consisting essentially of silicon nitride, silicon carbide and zirconium titanate; the fibers are silicon carbides fibers 5-20 microns thick; the coating on the coated fibers is boron nitride 0.1-0.3 microns thick; cross-section of the composite contains about one half, on volume basis, of uncoated fibers in one band extending from one side edge of the cross-section to the opposite side edge; the composite having unexpectedly improved strength and/or toughness compared to a composite composed of only coated or only uncoated fibers.
An improved elastomer-based connector sheet for use to electrically connect electrode terminals is proposed which comprises, in the form of an integral sheet: (a) a matrix in the form of a sheet made from an electrically insulating rubber having a specified rubber hardness; and (b) a multiplicity of straightly extending wire segments of a metal having a specified volume resistivity and having a diameter in the range from 20 to 90 .mu.m embedded in the matrix of the rubber substantially in parallel each with the others in such a direction that the bias angle formed with the direction perpendicular to the surface of the sheet is in the range from 20.degree. to 60.degree. in such a fashion that each of the wire segments has the ends exposed on the surfaces of the matrix sheet and the distance between the surfaces of adjacent wire segments is at least 10 .mu.m, the distribution density of the ends of the wire segments exposed on the sur-face of the matrix sheet being in the range from 70 to 1000 per mm.sup.2.
A debonding layer is formed on fibers such as silicon carbide fibers by forming a thin film of a metal such as nickel or iron on the silicon carbide fibers and then annealing at a temperature of about 350-550.degree. C. to form a debond layer of a metal silicide and carbon. These fibers having the debond coating can be added to composite forming materials and the mixture treated to form a consolidated composite. A one heating-step method to form a consolidated composite involves inserting the silicon carbide fibers with just the initial metal film coating into the composite forming materials and then heating the mixture to form the debond coating in situ on the fibers and to form the consolidated composite. Preferred heating techniques include high temperature annealing, hot-pressing, or hot isostatic pressing (HIP).
A device is disclosed for forwarding a medium in the form of a gas, liquid, or loose particles. The medium can contain additives and/or contaminants in an aggregate state other than that of the medium itself. The device's major components are form-fit and force-fit together and comprise at least one supporting component along with blade-like components fastened to it. The supporting component is, or the supporting components are, made of a fiber-filled composite. The device is in particular an impeller for a pump, turbine, or similar mechanism. It is characterized in that the supporting component is, or the supporting components are, made of a lattice of essentially continuous fibers of carbon and/or ceramic and of a matrix that contains carbon and in that the fibers are sheathed with silicon carbide resulting from the infiltration of liquid silicon and from its reaction essentially with the carbon in the matrix.
The present invention is a ceramic matrix composite turbine engine component, wherein the component has a region of expected higher interlaminate stress during normal engine operation. The component includes both coated fiber tows and uncoated fiber tows arranged together into a preselected form, wherein the uncoated fiber tows are located at predetermined regions of expected high interlaminate stress. The invention further includes method of manufacturing a CMC such as a composite turbine engine component, wherein the component has a region of expected higher interlaminate stress during engine operation.
An article comprising a ceramic material having a ceramic matrix composite backing adapted for use in a gas turbine engine is provided. The article comprises a structural ceramic material having a hot side facing toward a high temperature environment and a cold side facing away from the high temperature environment; and a ceramic matrix composite composition having a strength greater than the strength of the ceramic material attached to the back of the cold side of the ceramic material, whereby crack initiation and propagation are inhibited by the ceramic matrix composition to a greater degree than by the ceramic material.
