Patent Description:
Ceramic matrix composites (CMC) can be formed by infiltrating a preform with a matrix material such as by chemical vapor infiltration to form the matrix. Ceramic matrix composites have high temperature capability and are light weight, and are an attractive material for various applications in which high temperature durability and light weight are desired. Based on these and other features, there remains a desire and need for alternate methods and materials for ceramic matrix composites.

<CIT> discloses a composite threaded member having a helical composite portion externally bonded to a core portion.

A method of making a ceramic matrix composite is disclosed. According to the method, a first preform comprising fibers is formed, and a second preform including a helical surface portion is inserted into the first preform. The first preform with the inserted second preform is infiltrated with a matrix material comprising a ceramic to form the ceramic matrix composite.

The first preform may comprise a three-dimensional woven fiber preform or a stacked fiber layup.

The first preform may comprise a stacked layup of fibers including a Z-axis perpendicular to layers in the stacked layup, and the second preform may be inserted with a helical axis of said helical surface portion arranged parallel to the Z-axis.

The method may further comprise rotating the second preform about an axis of the helix in a rotational direction that promotes advancement of the helical surface through the first preform.

Axial movement of the second preform with said insertion may be equal to axial distance traveled by said helical surface portion in response to said rotation.

The helical surface portion may include a portion arranged as a screw.

The helical surface portion may include a helical portion arranged as a spring.

The second preform may be inserted into the first preform with the helical portion arranged as a spring being under tension, or under compression, or under neutral compression/tension.

The method may further comprise compressing the first preform and inserted second preform.

Compression of the inserted second preform may include a helical compression of the portion of the second preform arranged as a spring.

The second preform may comprise ceramic fibers and an organic polymer resin, and the method may include pyrolyzing the organic polymer resin after compression and before infiltrating the matrix material.

The method may further comprise compressing the first preform before infiltrating the matrix material.

The second preform may comprise ceramic fibers and an organic polymer resin, and the method may include pyrolyzing the organic polymer resin before infiltrating the matrix material.

The method may further include applying an interface coating to the first preform, or to the second preform, or to the first preform and the second preform before infiltrating the matrix material.

Infiltrating can comprise chemical vapor infiltration, atomic layer deposition, polymer infiltration and pyrolysis, and/or melt infiltration.

A ceramic matrix composite is also disclosed. The ceramic matrix composite includes a first portion including a matrix comprising a ceramic, and a reinforcement including fibers derived from the first preform in the matrix. A second portion including a helical surface portion interface with the first portion is disposed within the first portion.

The second portion may comprise a matrix comprising a ceramic, and a reinforcement comprising fibers in said matrix, said fibers derived from a second preform.

Also disclosed is a gas turbine engine component including a ceramic matrix composite that includes a first portion including a matrix comprising a ceramic, and a reinforcement including fibers derived from the first preform in the matrix. A second portion including a helical surface portion interface with the first portion is disposed within the first portion.

A ceramic matrix composite ("CMC") can be made by infiltrating a preform using matrix material such as by chemical vapor infiltration. The fiber preform contributes beneficial mechanical properties to the composite by providing reinforcement for a matrix material. Mechanical properties of interest include but are not limited to interlaminar shear strength ("ILS") and interlaminar tensile strength ("ITS"). CMC's can be used for high-temperature applications (e.g., <NUM> (<NUM> °F) and above), and may be designated as ultra-high temperature ceramic matrix composites ("UHT-CMC"). Exemplary CMC materials can include silicon-containing, or oxide containing matrix and reinforcing materials. Some examples of CMCs include, but are not limited to, materials having a matrix and reinforcing fibers comprising non-oxide silicon-based materials such as silicon carbide, silicon nitride, silicon oxycarbides, silicon oxynitrides, silicides, and mixtures thereof. Examples include, but are not limited to, CMCs with a silicon carbide matrix and silicon carbide fiber; silicon nitride matrix and silicon carbide fiber; and silicon carbide/silicon nitride matrix mixture and silicon carbide fiber. Furthermore, CMCs can have a matrix and reinforcing fibers including oxide ceramics. Specifically, the oxide-oxide CMCs may include a matrix and reinforcing fibers comprising oxide-based materials such as aluminum oxide (Al<NUM>O<NUM>), silicon dioxide (SiO<NUM>), yttrium aluminum garnet (YAG), aluminosilicates, or mixtures comprising any of the foregoing. Aluminosilicates can include crystalline materials such as mullite (3Al<NUM>O<NUM> 2SiO<NUM>), as well as glassy aluminosilicates. Other ceramic composite materials in addition to or in combination with silicon or oxygen may be used, including carbon, carbides (e.g., zirconium carbide, hafnium carbide, boron carbide), nitrides, or other ceramic materials, alone or in combinations including any of the materials noted above.

Referring to <FIG>, a first preform <NUM> is shown according to various embodiments. As shown in <FIG>, the preform <NUM> includes a plurality of fiber tows or plies <NUM>). Each fiber tow or ply <NUM> can include a plurality of individual fibers (e.g., from <NUM> to <NUM> fibers per tow). In various aspects, the fiber tows or plies <NUM> can be arranged in a <NUM>-D tape or a <NUM>-D fabric, and layers of tape or woven or unwoven fabric can be stacked in layup (including stacked layups of <NUM>-D fabrics such as a woven fabric and also stacked layups of <NUM>-D tape or <NUM>-D non-woven fabric) in order to form the preform <NUM>. Alternatively, a <NUM>-D fabric can be woven or otherwise arranged from continuous or noncontinuous fibers. The fibers can include any material typically used in CMC processing, such as carbon, alumina, silicon carbide, silicon nitride-carbide, zirconia, zirconium carbide, boron carbide, glass, or mullite. In some aspects, such as for high-temperature applications like gas turbine engine hot section components, fibers capable of withstanding specified temperatures can be used, including but not limited to ceramic fibers such as silicon carbide, alumina, zirconia, boron carbide, zirconium carbide, hafnium carbide. In some aspects, the fibers can include an interface coating (e.g., a boron nitride coating on a silicon carbide fiber). However, in other aspects the fibers can be bare fibers, in which case the fibers would not include an interface coating.

With reference now to <FIG>, a second preform including a helical surface portion is shown in the form of a helical compression spring <NUM>. Of course, the helical compression spring <NUM> is an example embodiment, and the second preform can include other types of helical surface portions. For example, the helical compression spring <NUM> includes a curvilinear-extending spring member <NUM> that extends along a helical path about an axis <NUM>. The compression spring includes a hollow space at and about the axis <NUM>, but the second preform could be solid at the axis <NUM> or include a solid annulus about the axis <NUM>, with the helical surface portion arranged in the form of a shaft twisting spiral rectangular shaft, or arranged as helical threads extending from a solid linear shaft or annulus. In some aspects, the helical surface portion of the second preform can be arranged to function as a screw. As used herein, the term "screw" refers to the simple machine its operation that converts between linear motion and rotational motion, and between rotational force (i.e., torque) and linear force. The compression spring <NUM> is an example of a screw, and can be inserted into the preform <NUM> by rotating the compression spring <NUM> so that leading tip <NUM> follows a helical path into the preform.

The compression spring <NUM> can be formed from materials to provide a target resiliency for conversion of stress and strain. In some aspects, the compression spring <NUM> can be formed from fibers and an elastomeric or flexible matrix polymer. The matrix polymer can be any type of polymer, including but not limited to epoxy, polyurethane, a polystyrene, polypropylene, polyethylene, etc. The fibers can be any of the fibers disclosed above, and can be the same as or of different composition compared to the fibers used in the first preform. The fibers in the second preform can be chopped and dispersed in the matrix polymer, or they can be extruded as continuous fibers extending co-linearly along the helical extension of the spring member <NUM>.

In some aspects, the compression spring <NUM> can be inserted in a Z-direction into the preform <NUM> as schematically shown in <FIG> (e.g., by screwing in with rotation in the direction of arrow <NUM>). In some aspects, this rotational insertion can provide a technical effect of promoting reduced breakage of fibers during insertion compared to other reinforcement techniques such as z-pinning. In some aspects, the compression spring <NUM> can be inserted into the preform <NUM> so that compression spring is under tension. In some aspects, the compression spring <NUM> can be inserted into the preform <NUM> so that the compression spring is under compression. In some aspects, the compression spring <NUM> can be inserted into the preform <NUM> so that compression spring is under neither compression nor tension (i.e., neutral compression/ tension).

During some aspects of processing (e.g., compression of the preforms prior to and during matrix infiltration and consolidation), the compression spring <NUM> may undergo helical deformation in response to an application of linear stress. As used herein, the term "helical deformation" means changes in the parameters of the helix such as pitch (axial distance corresponding to one complete turn of the helix), arc length, curvature, torsion to accommodate stress applied along the axis <NUM> and resulting deformation of a spring or spring-like structure in response to axial stress. In some aspects, the second preform can utilize an elastomeric matrix polymer to provide a resilient compression spring <NUM>. However, in some aspects, one-way deformation during processing, but absorption of compressive load by a resilient spring including shape recovery may not be needed if the performance of the preform is satisfied by placing reinforcing fibers along the helical insertion path of the second preform. In such cases, the polymer matrix for the second preform need not be elastomeric, but can instead provide a level of flexibility (in combination with the mechanical properties of the fibers in the second preform), that is sufficiently low to maintain its shape during insertion and to prevent deflection of the leading tip <NUM>, and also sufficiently high to tolerate deformation such as in response to compression along the axis <NUM>. <FIG> shows the compression spring <NUM> fully inserted in the Z-direction into the preform <NUM>.

In <FIG>, the preform <NUM> with the inserted second preform in the form of the compression spring <NUM> is shown disposed between tooling <NUM> and subjected to a compression load in the direction of arrows <NUM>. Compression of a preform before matrix infiltration/consolidation can beneficially promote high fiber volume in final composite, but can cause problems for conventional z-pinning schemes, including but not limited to breaking of fibers, and crimping or other damage to fibers, which can adversely impact the mechanical and performance properties of the composite. However, the compression spring <NUM> accommodates the stress from the compressive load <NUM> with helical deformation including a change in helical pitch with shorter axial distances between each turn of the helix as shown in <FIG>, which can promote reduced susceptibility to breaking of fibers, crimping, or other damage to fibers. A final preform structure after compression, with three compression springs <NUM> inserted into the preform <NUM>, is shown in <FIG>.

Any polymer resin in the second preform (and also any polymer resin in the first preform) can be pyrolyzed thermally decomposed, also known as burn-out, before infiltration of the matrix material. In cases where a fiber matrix interface coating is applied to the preforms, any polymer resin can be thermally decomposed before application of the fiber matrix interface coating. Thermal decomposition of polymer resin can be performed at temperatures of <NUM>-<NUM> in an oxidizing, inert, or vacuum environment.

In some aspects, a fiber/matrix interface coating can optionally be applied before matrix consolidation. In some aspects, a fiber/matrix interface coating can promote reduction in formation or propagation of cracks by allowing the fiber to slide in the interface coating at the fiber-coating interface or by allowing the coated fiber to move in the matrix by sliding at the coating-matrix interface. The choice of material for a fiber/matrix interface coating depends on the materials of the fibers and the matrix. For example, in the case of silicon carbide fibers and a silicon carbide matrix, the fibers may be coated with boron nitride as a fiber/matrix interface coating. A matrix/fiber interface coating can be applied by known means such as chemical vapor infiltration or atomic layer deposition, which can promote a uniform thickness coating and can infiltrate fine spaces in the preform(s).

With any polymers thermally decomposed, and a fiber/matrix interface coating applied (if desired), the preforms are ready for matrix consolidation. Matrix consolidation is typically performed by infiltration of the preforms with a matrix material. For example, in some aspects, the preforms can be treated with chemical vapor infiltration (CVI) in which a gas comprising a matrix material precursor (e.g., CH<NUM>SiCl<NUM>-H<NUM>) in a carrier gas at elevated temperature is infiltrated into the void space in the preforms and consolidates there to form a ceramic matrix material (e.g., SiC). The resultant composite, including fiber tows or plies <NUM> derived from the preform <NUM>, fiber reinforcements derived from second preforms in the form of compression springs <NUM>, and matrix material <NUM> is shown in <FIG>.

The method described herein can be used to prepare a variety of components comprising ceramic matrix composites such as components in the aviation industry, marine industry and energy industry. Exemplary components include components for gas turbine engines, such as in high pressure compressors ("HPC"), fans, boosters, high pressure turbines ("HPT"), and low pressure turbines ("LPT"). More specifically exemplary components include combustion liners, shrouds, nozzles, and blades. In addition to the above-referenced technical effect of reduced fiber breakage, the reinforcement provided to the composite by the second preform can promote additional technical effects, including but not limited to promotion of improved interlaminar shear strength ("ILS") and/or improvement of interlaminar tensile strength ("ILT").

In one disclosed embodiment, the engine <NUM> bypass ratio is greater than about ten (<NUM>:<NUM>), the fan diameter is significantly larger than that of the low pressure compressor <NUM>, and the low pressure turbine <NUM> has a pressure ratio that is greater than about five (<NUM>:<NUM>). The geared architecture <NUM> may be an epicyclic gear train, such as a planetary gear system or other gear system, with a gear reduction ratio of greater than about <NUM> :<NUM>. It should be understood, however, that the above parameters are only exemplary of one embodiment of a geared architecture engine and that the present disclosure is applicable to other gas turbine engines including direct drive turbofans.

The fan section <NUM> of the engine <NUM> is designed for a particular flight conditiontypically cruise at about <NUM> Mach (<NUM>/s) and about <NUM>,<NUM> feet (<NUM>,<NUM> meters). The flight condition of <NUM> Mach (<NUM>/s) and <NUM>,<NUM> ft (<NUM>,<NUM> meters), with the engine at its best fuel consumption--also known as "bucket cruise Thrust Specific Fuel Consumption ('TSFC')"--is the industry standard parameter of lbm of fuel being burned divided by lbf of thrust the engine produces at that minimum point.

Claim 1:
A method of making a ceramic matrix composite, comprising:
forming a first preform (<NUM>) comprising fibers;
inserting a second preform (<NUM>) including a helical surface portion into the first preform (<NUM>); and
infiltrating a matrix material (<NUM>) comprising a ceramic into the first preform (<NUM>) to form the ceramic matrix composite.