Patent Application
20240308922
The present invention relates to the fabrication of ceramic matrix composites (CMCs) and, more particularly, to CMCs having improved properties for operating in gas turbine engines.
In the processing of CMCs, there is a need to infiltrate matrix within and around fibrous tows to replace pore volume with dense matrix material. In a woven system, large voids often exist between adjacent tows of a preform. Such voids can become large defects after infiltration of the composite that are detrimental to composite properties. The pore network through a woven system is often highly tortuous for infiltrating reactant vapors, which leads to uneven deposition through the thickness of the preform.
The formation of z-channels can create more direct pathways for reactant gases. However, the metallic needles commonly used to form z-channels can contaminate and/or deform the preform. For example, metallic particles from the needles can remain in the preform after needle removal. Such particles and the preform ceramic material(s) can have dissimilar thermal and mechanical properties, thus their presence in the final CMC can be detrimental. Improved means for perforating preforms are therefore desirable.
A needle array suitable for perforating a fibrous preform includes a backplate and a plurality of needles individually removably attached to and extending away from the backplate. Each of the plurality of needles includes a bundle of ceramic filaments, a metallic sheath surrounding a first end of the bundle abutting the backplate, and a sharpened point on the second end of the bundle, the second end being oppositely disposed from the first end.
A method of forming a needle array suitable for perforating a fibrous preform includes arranging a plurality of ceramic filaments in a length-wise manner to form a bundle, coating the bundle with a reinforcing material, wrapping a sheath around the bundle such that the bundle has a sheathed portion at a first end and an exposed portion at a second end, securing the sheath to the bundle using an adhesive material, and forming a needle tip on the second end of the bundle.
A method of forming a needle suitable for perforating a fibrous preform includes arranging a plurality of ceramic filaments in a length-wise manner to form a bundle, coating the bundle with a reinforcing material, wrapping a sheath around the bundle such that the bundle has a sheathed portion at a first end and an exposed portion at a second end, securing the sheath to the bundle using an adhesive material, and forming a needle tip on the second end of the bundle.
While the above-identified figures set forth one or more embodiments of the present disclosure, other embodiments are also contemplated, as noted in the discussion. In all cases, this disclosure presents the invention by way of representation and not limitation. It should be understood that numerous other modifications and embodiments can be devised by those skilled in the art, which fall within the scope and spirit of the principles of the invention. The figures may not be drawn to scale, and applications and embodiments of the present invention may include features and components not specifically shown in the drawings.
After individual filaments 16 are secured together, bundle 14 can be further reinforced.
Needles 26 are individually removable to such that damaged needles 26 can be easily replaced, or the particular arrangement of needles 26 altered as desired. Generally speaking, only the ceramic, unsheathed portion (i.e., portion not covered by metallic sheath 20) of needle 26 will be inserted into a preform (i.e., preform 10) for z-channel formation. Thus, any contaminants (i.e., ceramic particles from needles 26) remaining in preform 10 after z-channel formation can become part of the final CMC component with little detrimental impact on component properties. Needles 26 formed from ceramic may also be more durable than metallic needles, with a longer useful life.
A CMC component formed with the disclosed perforating means can be incorporated into aerospace, maritime, or industrial equipment, to name a few, non-limiting examples.
The following are non-exclusive descriptions of possible embodiments of the present invention.
A needle array suitable for perforating a fibrous preform includes a backplate and a plurality of needles individually removably attached to and extending away from the backplate. Each of the plurality of needles includes a bundle of ceramic filaments, a metallic sheath surrounding a first end of the bundle abutting the backplate, and a sharpened point on the second end of the bundle, the second end being oppositely disposed from the first end.
The needle array of the preceding paragraph can optionally include, additionally and/or alternatively, any one or more of the following features, configurations and/or additional components:
In the above needle array, each of the ceramic filaments can be formed from one of silicon carbide, silicon nitride, and aluminum oxide.
In any of the above needle arrays, each of the ceramic filaments can further include an interface coating of at least one of boron nitride, silicon carbide, silicon nitride, and pyrolytic carbon.
In any of the above needle arrays, the bundle of ceramic filaments can further include a reinforcing coating including one of epoxy, a ceramic, a polymer-derived ceramic, and a silicon alloy.
In any of the above needle arrays, the metallic sheath can be secured to the bundle of ceramic filaments with an adhesive material.
In any of the above needle arrays, a width of the metallic sheath can be greater than a width of the bundle of ceramic filaments.
A method of forming a needle array suitable for perforating a fibrous preform includes arranging a plurality of ceramic filaments in a length-wise manner to form a bundle, coating the bundle with a reinforcing material, wrapping a sheath around the bundle such that the bundle has a sheathed portion at a first end and an exposed portion at a second end, securing the sheath to the bundle using an adhesive material, and forming a needle tip on the second end of the bundle.
The method of the preceding paragraph can optionally include, additionally and/or alternatively, any one or more of the following features, configurations and/or additional components:
In the above method, forming the needle tip can include placing a rounded bead on the second end.
In any of the above methods, the rounded bead can be formed from one of a silicon carbide precursor and a polymer material.
In any of the above methods, forming the needle tip can include sharpening the second end to form a point.
In any of the above methods, the second end can be sharpened using one of a grinding wheel and a jig.
Any of the above methods can further include attaching each of the plurality of needles to a backplate.
A method of forming a needle suitable for perforating a fibrous preform includes arranging a plurality of ceramic filaments in a length-wise manner to form a bundle, coating the bundle with a reinforcing material, wrapping a sheath around the bundle such that the bundle has a sheathed portion at a first end and an exposed portion at a second end, securing the sheath to the bundle using an adhesive material, and forming a needle tip on the second end of the bundle.
The method of the preceding paragraph can optionally include, additionally and/or alternatively, any one or more of the following features, configurations and/or additional components:
In the above method, forming the needle tip can include placing a rounded bead on the second end.
In any of the above methods, the rounded bead can be formed from one of a silicon carbide precursor and a polymer material.
In any of the above methods, forming the needle tip can include sharpening the second end to form a point.
In any of the above methods, the second end can be sharpened using one of a grinding wheel and a jig.
Any of the above methods can further include attaching the needle to a backplate.
In any of the above methods, the reinforcing coating can include one of epoxy, a ceramic, a polymer-derived ceramic, and a silicon alloy.
Any of the above methods can further include after forming the needle, applying silicon carbide to the needle using chemical vapor infiltration.
While the invention has been described with reference to an exemplary embodiment(s), it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment(s) disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.
