Patent Application
20240376017
The present invention relates to ceramic matrix composites and, more particularly, space filling inserts for use in ceramic matrix composite preforms.
Many ceramic matrix composite (CMC) components for gas turbine engines have regions of variable wall thickness. Some of these regions are too small to form with textile-based plies, but too large to form using individual fiber tows. In such cases, space filling inserts can be used to build upon and prevent large voids in the body of the CMC. As with other locally thickened regions of CMCs, these inserts can often present challenges in achieving a high and/or uniform density through chemical vapor infiltration (CVI) or other infiltration processes.
A method of forming a ceramic matrix composite includes fabricating a space filling insert by assembling the space filling insert from a fibrous ceramic material, placing the space filling insert into a tooling fixture, the tooling fixture having an internal shape complementary to a shape of the insert, and infiltrating the space filling insert with a first ceramic material. The method further includes forming a preform by laying up a plurality of fibrous ceramic plies and inserting the infiltrated space filling insert into a void defined by the plurality of plies. The method further includes infiltrating the preform with a second ceramic material.
A method of fabricating a space filling insert for a ceramic matrix composite includes assembling the space filling insert from a fibrous ceramic material, placing the space filling insert into a tooling fixture, the tooling fixture having an internal shape complementary to a shape of the insert, and infiltrating the space filling insert with a material.
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 prefabricated space filling inserts, sometimes referred to as “noodles,” for incorporation into a CMC preform. More specifically, space filling inserts can be at least partially densified with a matrix prior to incorporation into a preform. This allows for fabrication of CMC components with more uniformly deposited matrixes.
At step 12, insert 20 can be assembled from a fibrous ceramic material. Exemplary materials include two or three-dimensional woven, braided, knitted or non-textile (e.g., unidirectional short/long strand matted, etc.) ceramic (e.g., silicon carbide—SiC) structures. A polymer binder (e.g., polyvinyl alcohol or polyvinyl butyral) can optionally be applied to the ceramic material to rigidize insert 20.
At step 14, insert 20, with or without a binder, can be placed into tooling fixture 22 which can include one or more segments 24. Each segment 24 can be machined such that, when assembled, tooling fixture 22 mirrors the dimensions of the specific preform cavity receiving insert 20. As such, tooling fixture 22 can help mold insert 20 into a more precise shape. Tooling fixture 22 further supports insert 20 during densification, as is discussed in greater detail below. Segments 24 can, accordingly, be formed from graphite, refractory metals, or a carbon-carbon composite, to name a few, non-limiting examples. One or more segments 24 can include infiltration holes (not visible in the plane of
At step 16, insert 20, mounted within tooling fixture 22, can be infiltrated with a ceramic (e.g., SiC) matrix. In one embodiment, matrix formation can be carried out using CVI. During matrix formation, insert 20 is infiltrated by reactant vapors, and a gaseous precursor deposits on the ceramic fibers. Infiltration is carried out until reaching a desired porosity. In one embodiment, insert 20 can be partially infiltrated, such that an amount of open porosity (i.e., above the desired final porosity) is present at the conclusion of step 16. This may be preferable to allow further infiltration of insert 20 once incorporated into a preform, which can improve bonding between insert 20 and the surrounding structure of the preform. A fully infiltrated insert 20 after step 16 can be preferable where very low insert porosity is desired, such as in CMC regions requiring high thermal conductivity and/or high oxidation resistance. Alternative methodologies for matrix formation can include, but are not limited to, one or a combination of melt infiltration (MI) or polymer infiltration and pyrolysis (PIP). In some embodiments, one or several interface coatings of a ceramic material (e.g., of boron nitride—BN) can be deposited prior to formation of the ceramic matrix. In some other embodiments, interface coatings can deposited at step 16, and densification can take place after the coated insert 20 is incorporated into a preform.
At step 18, insert 20 can optionally undergo post-infiltration processing. As shown in
A CMC component formed with the disclosed prefabricated inserts can be incorporated into components for multiple industries such as aerospace, maritime, or industrial, to name a few, non-limiting examples.
The following are non-exclusive descriptions of possible embodiments of the present invention.
A method of forming a ceramic matrix composite includes fabricating a space filling insert by assembling the space filling insert from a fibrous ceramic material, placing the space filling insert into a tooling fixture, the tooling fixture having an internal shape complementary to a shape of the insert, and infiltrating the space filling insert with a first ceramic material. The method further includes forming a preform by laying up a plurality of fibrous ceramic plies and inserting the infiltrated space filling insert into a void defined by the plurality of plies. The method further includes infiltrating the preform with a second ceramic material.
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 steps:
In the above method, at least one of the first ceramic material and the second ceramic material can be a ceramic matrix.
In any of the above methods, the ceramic matrix comprises silicon carbide.
In any of the above methods, at least one of the first ceramic material and the second ceramic material can be a ceramic interface coating.
In any of the above methods, the steps of infiltrating each of the space filling insert and the preform can include one of: chemical vapor infiltration, polymer infiltration and pyrolysis, and melt infiltration.
Any of the above methods can further include prior to placing the space filling insert into the tooling fixture, applying a polymer binder to the space filling insert.
In any of the above methods, the tooling fixture can include a plurality of segments.
In any of the above methods, at least one of the plurality of segments can include infiltration holes.
In any of the above methods, the tooling fixture can be formed from one of graphite, a carbon-carbon composite, and a refractory metal.
Any of the above methods can further include prior to fabricating the space filling insert, ascertaining an expected geometry of the void, and assembling the tooling fixture such that the internal shape substantially matches the expected shape of the void.
A method of fabricating a space filling insert for a ceramic matrix composite includes assembling the space filling insert from a fibrous ceramic material, placing the space filling insert into a tooling fixture, the tooling fixture having an internal shape complementary to a shape of the insert, and infiltrating the space filling insert with a material.
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 steps:
In the above method, the fibrous ceramic material can include silicon carbide.
In any of the above methods, the material can form one of a ceramic interface coating and a ceramic matrix.
In any of the above methods, the ceramic matrix can include silicon carbide.
Any of the above methods can further include prior to placing the space filling insert into the tooling fixture, applying a polymer binder to the space filling insert.
Any of the above methods can further include after infiltrating the space filling insert, removing the space filling insert from the tooling fixture, and trimming the space filling insert.
In any of the above methods, the tooling fixture can include a plurality of segments.
In any of the above methods, at least one of the plurality of segments can include infiltration holes.
In any of the above methods, the tooling fixture can be formed from one of graphite, a carbon-carbon composite, and a refractory metal.
In any of the above methods, the step of infiltrating the space filling insert comprises one of: chemical vapor infiltration, polymer infiltration and pyrolysis, and melt 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 should 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.
