Patent Application
20240344255
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, which can facilitate more even matrix infiltration. Thus, means for creating z-channels in preforms are desirable.
A tooling assembly for debulking a fibrous preform includes a first tooling fixture comprising a plurality of receiving holes, and a second tooling fixture comprising a plurality of pins projecting toward the first tooling fixture, each of the plurality of pins corresponding to and extending towards one of the plurality of receiving holes. The second tooling fixture is engageable with the first tooling fixture to define an inner volume therebetween, the inner volume configured to support the preform during debulking while a compressive force is applied thereto.
A method of preparing a fibrous preform for use in a ceramic matrix composite includes debulking the fibrous preform by supporting the preform with a first tooling fixture, the first tooling fixture including a plurality of receiving holes, engaging a second tooling fixture with the first tooling fixture such that the preform is disposed therebetween, and applying a compressive force to the preform. Engaging the second tooling fixture with the first tooling fixture causes a plurality of pins projecting from the first tooling fixture to extend through a thickness of the preform.
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.
This disclosure presents means for perforating a fibrous ceramic preform prior to densification (e.g., via chemical vapor infiltration—CVI). More specifically, perforation can be performed during a debulking process. Multiple embodiments of combined perforating/debulking tooling can be used to create z-channels through the thickness of the preform, such that separate tooling is advantageously not required. Z-channels facilitate access to the interior of the preform by reactant vapors such that matrix deposits in a more even manner compared to non-perforated preforms.
As shown, tooling assembly 10 includes male (i.e., perforating) tooling fixture 14 and female (i.e., receiving) tooling fixture 16. Male tooling fixture 14 includes multiple pins 18 extending away from backplate 20. Pins 18 can be arranged as an array of rows and columns and can have uniform or varied lengths with respect to other pins 18, as is discussed below with respect to
In one example, a non-debulked or partially debulked preform 12 can be placed within tooling assembly 10, and a mechanical compressive force exerted on preform 12 as fixtures 14 and 16 are secured together. This can at least nominally reduce the thickness of preform 12. In another example, a vacuum can be generated within inner volume 26 to compress and debulk preform 12. In yet another example, a combination of mechanical and vacuum pressure can be used to debulk preform 12. In any case, z-channels are formed during debulking by pins 18. Pins 18 are inserted in such manner as to maximize the pushing away of individual fibers of perform 12, and to minimize the breaking of such fibers. Accordingly, formation of z-channels with pins 18 during debulking can be less destructive than methods such as laser drilling, as well as needling processes that occur in dedicated steps, requiring additional handling of preform 12.
Tooling assembly 110 operates substantially similarly to tooling assembly 10, applying a mechanical compressive force, and/or supporting preform 112 while a vacuum is applied. Tooling assembly 110 can be all or partially formed from metal, hardened polymer material, or ceramic. Like pins 18A and 18B, pins 118 can be monolithically formed with backplate 120 or removably attached thereto (e.g., via mounting bosses). Pins 118 can be the same material as backplate 120, or a different material. Pins 118 can further be mostly cylindrical with a short taper to form a pointed tip.
After debulking, preforms 12, 112 can be removed from respective tooling assemblies 10, 110 to undergo further processing. In some embodiment, preforms 12, 112 can be transferred to graphite tooling assemblies for interface coating (IFC) deposition via CVI and/or densification (i.e., matrix formation) via CVI. Densification is carried out until the resulting CMC has reached the desired residual porosity. In an alternative embodiment, densification can include other methodologies such as, but not limited to, melt infiltration and polymer infiltration and pyrolysis (PIP).
A CMC component formed with the disclosed tooling assemblies can be incorporated into aerospace, maritime, or industrial equipment, to name a few, non-limiting examples.
Discussion of Possible Embodiments
The following are non-exclusive descriptions of possible embodiments of the present invention.
A tooling assembly for debulking a fibrous preform includes a first tooling fixture comprising a plurality of receiving holes, and a second tooling fixture comprising a plurality of pins projecting toward the first tooling fixture, each of the plurality of pins corresponding to and extending towards one of the plurality of receiving holes. The second tooling fixture is engageable with the first tooling fixture to define an inner volume therebetween, the inner volume configured to support the preform during debulking while a compressive force is applied thereto.
The tooling assembly 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 tooling assembly, the second tooling fixture can be further engageable with the first tooling fixture such that the plurality of pins extend through the thickness of the preform and at least partially into respective ones of the plurality of receiving holes.
In any of the above tooling assemblies, a length of each of the plurality of pins can be uniform across the second tooling fixture.
In any of the above tooling assemblies, one pin of the plurality of pins can have a first length, and a second pin of the plurality of pins can have a second length greater than the first length.
In any of the above tooling assemblies, the second tooling fixture can further include a backplate.
In any of the above tooling assemblies, each of the plurality of pins can be removably attached to the backplate via a mounting boss.
In any of the above tooling assemblies, the plurality of pins can be monolithically formed with the backplate.
In any of the above tooling assemblies, the backplate can be formed from a first material, and the plurality of pins can be formed from a second material, the second material being different than the first material.
In any of the above tooling assemblies, each of the backplate and the plurality of pins can be formed from the same material.
In any of the above tooling assemblies, the first tooling fixture and the backplate of the second tooling fixture can be curved.
In any of the above tooling assemblies, the backplate can include a plurality of sections, each of the plurality of sections including a subset of the plurality of pins.
In any of the above tooling assemblies, the first tooling fixture can be a mandrel.
In any of the above tooling assemblies, each of the plurality of pins can be cylindrical with a pointed tip.
A method of preparing a fibrous preform for use in a ceramic matrix composite includes debulking the fibrous preform by supporting the preform with a first tooling fixture, the first tooling fixture including a plurality of receiving holes, engaging a second tooling fixture with the first tooling fixture such that the preform is disposed therebetween, and applying a compressive force to the preform. Engaging the second tooling fixture with the first tooling fixture causes a plurality of pins projecting from the first tooling fixture to extend through a thickness of the preform.
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, engaging the second tooling fixture with the first tooling fixture can further cause the plurality of pins to extend at least partially into respective ones of the plurality of receiving holes.
In any of the above methods, the compressive force can include one or a combination of mechanical pressure and vacuum pressure.
In any of the above methods, debulking can further include after applying the compressive force to the preform, removing the second tooling fixture such that a plurality of z- channels is formed through the thickness of the preform.
Any of the above methods can further include densifying the preform using one or a combination of chemical vapor infiltration, chemical vapor deposition, polymer infiltration and pyrolysis, and melt infiltration.
In any of the above methods, the preform can be formed from silicon carbide.
In any of the above methods, the first tooling fixture, the second tooling fixture, and the preform can be curved.
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.
