Patent Description:
Ceramic matrix composites (CMCs) generally comprise a ceramic fiber reinforcement material embedded in a ceramic matrix material. The reinforcement material may be discontinuous short fibers that are randomly dispersed in the matrix material or continuous fibers or fiber bundles oriented within the matrix material. The reinforcement material serves as the load-bearing constituent of the CMC in the event of a matrix crack. In turn, the ceramic matrix protects the reinforcement material, maintains the orientation of its fibers, and serves to dissipate loads to the reinforcement material. Silicon-based CMCs, such as silicon carbide (SiC) as the matrix and/or reinforcement material, have become of particular interest in high-temperature applications due to their high temperature capabilities, such as for use in components of gas turbines, including aircraft gas turbine engines and land-based gas turbine engines. SiC fibers have also been used as a reinforcement material for a variety of other ceramic matrix materials, including TiC, Si3N4, and Al2O3.

Continuous fiber reinforced ceramic composites (CFCC) are a particular type of CMC that offers light weight, high strength, and high stiffness for a variety of high temperature load-bearing applications, such as in shrouds, combustor liners, vanes (nozzles), blades (buckets), and other high-temperature components of gas turbines. A notable example of a CFCC material developed by the General Electric Company under the name HiPerComp® contains continuous SiC fibers in a matrix of SiC and elemental silicon or a silicon alloy.

Various techniques may be employed in the fabrication of CMCs, including chemical vapor infiltration (CVI), wet drum winding, lay-up, lamination, pyrolysis, and melt infiltration (MI). These fabrication techniques have been used in combination with tooling or dies to produce near-net-shape articles through processes that include the application of heat and chemical processes at various processing stages. Examples of such processes, particularly for SiC/Si-SiC (fiber/matrix) CFCC materials, are disclosed in <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>,<CIT>, and<CIT>, and <CIT>.

One process of manufacturing CMCs entails the use of CMC prepregs, which are typically sheet-like structures comprising the reinforcement fibers impregnated with a slurry that contains a precursor of the matrix material and one or more organic binders. The prepreg must undergo processing (e.g., firing) to convert the precursor to the desired ceramic matrix material. Prepregs for CFCC materials frequently comprise a two-dimensional fiber array comprising a single layer of aligned tows (bundles of individual filaments) impregnated with a matrix precursor to create a generally two-dimensional lamina. Multiple plies of the resulting prepregs are then stacked and debulked to form a laminate preform, a process referred to as "lay-up. " The prepregs are typically, but not necessarily, arranged so that tows of adjacent prepregs are oriented transverse (e.g., perpendicular) to each other, providing greater strength in the laminar plane of the preform (corresponding to the principal (load-bearing) directions of the final CMC article). As an example, <FIG> represents a surface region of a CMC article <NUM> including multiple laminae <NUM>, each the result of individual prepreg tapes or sheets. As also shown in <FIG>, each lamina <NUM> contains a ceramic reinforcement made up of unidirectionally-aligned fibers <NUM> encased in a ceramic matrix <NUM> formed by conversion of the ceramic matrix precursor (e.g., after firing).

As illustrated in <FIG>, one process utilized in making prepreg CMC preforms includes a winding technique to form the fibers <NUM> (individual filaments or tows) into a unidirectional prepreg tape, which is then used for the lay-up of the composite preform. As represented in <FIG>, some winding techniques involve coating the fibers <NUM>. The fibers <NUM> are coated for several purposes, such as to protect them during composite processing, to modify fiber-matrix interface strength and to promote or prevent mechanical and/or chemical bonding of the fiber and matrix. A number of different techniques have been developed for applying coatings to ceramic fiber, such as slurry-dipping, sol-gel, sputtering and chemical vapor deposition (CVD). Of these techniques, CVD may be considered as being most successful in producing impervious coatings of uniform thickness and controlled composition. In a typical CVD process, the fibers and reactants are heated to an elevated temperature where coating precursors decompose and deposit as the coating.

Continuous fiber coating processes have been preferred for composites processed by the winding technique. In a continuous coating process, as shown in <FIG>, fiber <NUM> is continuously passed through a CVD reactor <NUM> containing coating precursors <NUM> to form the coated fiber <NUM>. As also shown in <FIG>, a continuous fiber coating process may involve running a single fiber tow or filament <NUM> through the CVD reactor <NUM> at a time. The coating may be conducted at low pressure, and the fiber <NUM> may be transported through the reactor <NUM> at a slow speed, to insure uniform coating on the coated fiber <NUM>. Such a CVD coating process suffers from a significant amount of broken fibers, and "loose" fibers when a fiber tow is coated (i.e., "fuzz"), which degrades throughput or yield of the process. Although such a fiber coating process may provide an effective coated fiber <NUM>, there remains a need for further improvements to CVD coat fibers <NUM> with higher productivity.

As illustrated in <FIG>, a winding technique may also form the coated fiber <NUM> (a filament or tow) into a unidirectional prepreg tape by impregnating the coated fiber <NUM> with a matrix precursor <NUM>. For example, a wet drum winding processes for impregnating the coated ceramic fiber <NUM> may entail pulling the ceramic fiber <NUM> through a bath <NUM> of a matrix precursor slurry mixture that includes suitable matrix precursor materials, organic binders, and solvents, as shown in <FIG>. The resulting precursor-impregnated fiber <NUM> is then wound around a drum <NUM> to form a planar unidirectional prepreg tape. Before contacting the drum <NUM>, the precursor-impregnated fiber <NUM> is typically pulled through an orifice to control the amount of slurry picked up. By indexing the drum <NUM> (and/or the bath <NUM> and orifice), the precursor-impregnated fiber <NUM> is laid down at a constant pitch to yield a continuous, planar unidirectional prepreg tape. Prior to being wound with the precursor-impregnated fiber <NUM>, the drum <NUM> may be wrapped with a release sheet so that the resulting prepreg tape can be more easily removed from the drum <NUM>. While on the drum <NUM>, the prepreg tape may be allowed to air dry by allowing the solvents to evaporate. Alternatively, the tape may be cut from the drum <NUM>, laid flat, and allowed to air dry.

Prepreg tapes produced by such a wet drum winding processes may have a surface roughness, or waviness, corresponding to the pitch of the fiber <NUM> on the drum <NUM>. There may also be variability in the distribution of fiber and matrix across the tape because of the pitch. Furthermore, because the fiber is under tension during the winding process, the impregnated fiber <NUM> may tend to be pulled down onto the drum surface, yielding a prepreg tape that has proportionally more fiber at the surface of the tape contacting the drum <NUM> and proportionally more matrix precursor at the surface of the tape facing away from the drum <NUM>.

Such a wet drum winding process can also suffer from a significant amount of broken fibers, and loosely adhering fibers <NUM> (i.e., "fuzz") when a tow is utilized, that can break off and cause blockage of the orifice. Consequently, drum winding operations may require constant operator supervision so that such blockages can be removed as they occur.

Another complication of a drum winding processes may revolve around necessity to completely impregnate (i.e., wet out) the fiber <NUM> with the slurry <NUM> during the winding process, which requires that the fiber <NUM> spend a sufficient amount of time submersed in the slurry <NUM>. This submersion time, which can be about five seconds for certain processes, may place a limit on the speed with which the fiber <NUM> can be drawn through the slurry <NUM> bath. Consequently the time necessary to drum wind a <NUM> meter fiber <NUM> tow can be relatively lengthy.

Accordingly, alternative methods and apparatus for coating and/or impregnating ceramic fiber (to form prepregs) for producing CMCs with improved yield or throughput are desirable.

<CIT> describes a method of forming a CMC.

<CIT> describes a process of producing a silicon carbide reinforced composite.

In one aspect, the present disclosure provides for a method of processing ceramic fiber for the manufacture of a ceramic matrix composite (CMC) article. The method includes providing at least one frame including a planar array of unidirectional ceramic fibers extending across a void thereof. The method includes depositing a coating on the ceramic fibers of the least one frame via a chemical vapor deposition (CVD) process. The method includes impregnating the coated ceramic fibers of the at least one frame with a slurry including a ceramic matrix precursor composition to form at least one CMC prepreg tape, wherein impregnating the coated ceramic fibers includes removing the coated ceramic fibers from at least a portion of the at least one frame and impregnating the removed coated ceramic fibers with the slurry.

In some embodiments, the CVD process may include positioning the at least one frame within a CVD reactor, and the CVD process may be a batch CVD process. In some embodiments, providing the at least one frame may include coupling the ceramic fibers to at least one frame. In some embodiments, at least one of the ceramic fibers may include a ceramic fiber tow. In some embodiments, at least one of the ceramic fibers may include non-bundled ceramic filament. In some embodiments, the ceramic fibers may include at least one continuous ceramic fiber that extends across the void a plurality of times. In some embodiments, the ceramic fibers may include at least one discrete ceramic fiber that extends once across the void.

In some embodiments, the ceramic fibers may be substantially SiC. In some embodiments, the coating may include at least one layer including boron nitride, silicon-doped boron nitride, carbon, silicon carbide or silicon nitride.

These and other objects, features and advantages of this disclosure will become apparent from the following detailed description of the various aspects of the disclosure taken in conjunction with the accompanying drawings.

Any examples of parameters are not exclusive of other parameters of the disclosed embodiments. Components, aspects, features, configurations, arrangements, uses and the like described, illustrated or otherwise disclosed herein with respect to any particular embodiment may similarly be applied to any other embodiment disclosed herein.

<FIG> illustrate an exemplary ceramic fiber processing apparatus <NUM> (not part of the invention) according to the present disclosure. The apparatus <NUM> may facilitate or provide for the processing of ceramic fiber for the manufacture of a ceramic matrix composite (CMC) article. For example, the apparatus <NUM> may facilitate the coating of ceramic fiber via a batch process and/or the formation of a prepreg tape (e.g., infiltration) from coated ceramic fiber via a batch process. Alternatively, a plurality of the apparatuses <NUM> may be coupled together, or each apparatus <NUM> may form a portion or a segment of larger structure, that facilitates the coating of ceramic fiber via a continuous process and/or the formation of a prepreg tape including coated ceramic fiber via a continuous process.

As shown in <FIG>, the processing apparatus <NUM> includes a frame <NUM> that forms a void <NUM>, and a plurality of ceramic fibers <NUM> extending across the void <NUM>. Each of the plurality of ceramic fibers <NUM> extend across the void <NUM> and are positioned within the void <NUM> (entirely or partially). In this way, the void <NUM> may expose the ceramic fibers <NUM>. The ceramic fibers <NUM> may be at least portions of individual ceramic filaments or strands, ceramic fiber tows, or a combination of individual filaments and tows. It will be appreciated that a "ceramic fiber tow" or simply a "tow," as used herein, refers to a bundle of a plurality of individual ceramic filaments or loose strands. The filaments of a tow may be randomly intermingled or arranged in a pattern, and/or may be continuous or noncontinuous. For example, a tow may include broken filaments or filament segments. As another example, the filaments of a tow may be substantially parallel, twisted or otherwise arranged. A tow may act substantially in the same manner as a single or individual filament. It will also be appreciated that an "individual ceramic filament," or simply an "individual filament," as used herein, refers to a singular or non-bundled elongate ceramic member.

The ceramic fibers <NUM> each extend substantially in a first direction across the void <NUM>, such as from a first portion <NUM> to a second portion <NUM> of the frame. In this way, the ceramic fibers <NUM> are unidirectional (e.g., for the formation of a unidirectional CMC prepreg tape and/or a unidirectional CMC article, as is known in the art). The ceramic fibers <NUM> may include relatively minor directional variations as they extend across the void <NUM>, but the ceramic fibers <NUM> are unidirectional such that they extend substantially in the first direction and do not cross-over each other. Similarly, the ceramic fibers <NUM> may include minor directional variations, but the ceramic fibers <NUM> are unidirectional such that they extend substantially along the first direction and/or substantially parallel to one another, as a whole. If the ceramic fibers <NUM> include at least one tow, the at least one tow, as a whole, may be unidirectional (extend along the first direction) and/or the ceramic filaments making up the tow may be unidirectional. In some other embodiments, the ceramic filaments of a tow of the ceramic fibers <NUM> may extend in differing directions than the first direction (i.e., are non-unidirectional, such as twisted or woven filaments), but tow, as a whole, may extend substantially in the first direction such that the ceramic fibers <NUM> across the void <NUM> are unidirectional.

As shown in <FIG>, the unidirectional ceramic fibers <NUM> extending across the void <NUM> of the frame <NUM> form a planar array. The unidirectional ceramic fibers <NUM> are substantially arranged or positioned along a plane across the void <NUM>. In this way, the processing apparatus <NUM> may include a substantially planar array of substantially unidirectional ceramic fibers <NUM> extending across the void <NUM> of the frame <NUM>. The planar arrangement of the ceramic fibers <NUM> may include relatively minor variations or outliers, but the ceramic fibers <NUM> may, as a whole, be arranged along a plane. For example, as explained further below at least one of the ceramic fibers <NUM> may include a plurality of individual ceramic filaments, such as a tow (as shown in <FIG>). In some such embodiments, while the individual ceramic filaments may be off-plane (at least with respect to each other), the ceramic fibers <NUM>, as a whole, may be substantially arranged on a plane such that the ceramic fibers <NUM> across the void <NUM> form, as a whole, a substantially planar array (and the ceramic fibers <NUM> are unidirectional).

The unidirectional ceramic fibers <NUM> forming the planar array may be spaced from each other, as a whole, as shown in <FIG>. The spacing of the ceramic fibers <NUM> may be particularly configured to expose a maximum amount of the exterior surface of the fibers <NUM> (e.g., the filaments making a tow) to ensure formation of a coating thereon, as explained further below. As another example, the spacing of the ceramic fibers <NUM> may be particularly configured in consideration of the material of the ceramic fibers <NUM> for the formation of a prepreg therefrom (as explained further below) and/or a desired performance or application of a CMC ultimately formed from the ceramic fibers <NUM>, as explained further below. The frames <NUM> disclosed herein may provide for effective and consistent ceramic fiber <NUM> arrangement at relatively low tensions thereof, which facilitates maximum coating coverage and/or fiber arrangement during impregnation. It is noted, however, that the ceramic fibers <NUM> may include some minor variations in arrangement (e.g., filament breakage) that results in uneven spacing and/or abutting or intersecting of some of the fibers <NUM>. As a whole, however, the ceramic fibers <NUM> may be spaced from one another. In some embodiments, the unidirectional ceramic fibers <NUM> (whether tows or single filaments), as a whole, may be substantially evenly spaced throughout the planar array, or the spacing may vary. If the ceramic fiber portions <NUM> are tows, the frame <NUM> may be configured such that the ceramic filaments making up each tow are spaced from each other. In such embodiments, the spacing of adjacent tows (i.e., the spacing between adjacent ceramic filaments of adjacent tows) may be spaced about the same distance as the spacing of the individual filaments of the tows. In some embodiments, the ceramic fibers <NUM> may be positioned and spaced from each other such that the density and arrangement of filaments thereof is substantially uniform throughout the width and/or length and/or thickness of the planar array.

At least one of the unidirectional ceramic fibers <NUM> extending across the void <NUM> of the frame <NUM> may be a portion of a ceramic fiber that also includes one or more portion positioned exterior to the void <NUM>. Alternatively, at least one of the ceramic fibers <NUM> may not be a portion of a longer ceramic fiber, and such a ceramic fiber <NUM> may, potentially, be contained entirely across the void <NUM>. The unidirectional ceramic fibers <NUM> extending across the void <NUM> may be formed of separate and distinct ceramic fibers (tow or filament), portions of one or more continuous ceramic fiber (tow or filament), or a combination of separate and distinct ceramic fibers and portions of one or more continuous ceramic fiber. For example, at least some of the ceramic fibers <NUM> passing across or through the void <NUM> may be portions of a continuous ceramic fiber. In this way, the ceramic fibers <NUM> extending across the void <NUM> may be portions of at least one continuous ceramic fiber that extends across the void <NUM> a plurality of times. Each pass or portion of such a continuous ceramic fiber extending across the void <NUM> may be one of the unidirectional ceramic fibers <NUM> of the planar array <NUM>. In some such embodiments, two or more of the passes or portions of the continuous ceramic fiber extending across the void <NUM> (and forming unidirectional ceramic fibers <NUM> of the planar array <NUM>) may be contiguous portions thereof. As another example, at least one of the ceramic fibers <NUM> across the void <NUM> and forming the planar array <NUM> may be at least a portion of a unique or distinct ceramic fiber. The unidirectional ceramic fibers <NUM> extending across the void <NUM> and forming the planar array <NUM> may thereby include at least one discrete ceramic fiber that extends or passes once across the void <NUM>. In this way, two of the ceramic fibers <NUM> extending or passing across the void <NUM> and forming the planar array <NUM> may be at least portions of two separate and distinct ceramic fibers.

The unidirectional ceramic fibers <NUM> of the planar array <NUM> across the void <NUM> of the frame <NUM> may be any ceramic material suitable for the manufacture of CMC prepregs and, ultimately, CMC articles. For example, the ceramic fibers <NUM> may be primarily carbon (C), silicon carbide (SiC), alumina (Al2O3) and/or mullite (Al2O3-SiO2) based fibers. The ceramic fibers <NUM> may contain other elements and/or impurities in addition to the base or primary material, such as C, O, N, Ti, Zr, B, for example. In some embodiments, the apparatus <NUM> may be particularly advantageous for coating silicon carbide fibers (i.e., pure SiC fibers or primarily SiC based fibers) and/or forming a prepreg with such coated silicon carbide fibers. In such embodiments, the apparatus <NUM> may include a planar array <NUM> of unidirectional silicon carbide ceramic fibers <NUM> extending across the void <NUM> of the frame <NUM>.

The frame <NUM> may be of any design, configuration or mechanism that forms a space or void <NUM> and supports the planar array <NUM> of unidirectional ceramic fibers <NUM> across the void <NUM>. The void <NUM> may be of any size or shape for any corresponding size or shape planar array <NUM>. The void <NUM> may be an unobstructed area in which the planar array <NUM> is provided. In some embodiments, the frame <NUM> may be configured such that the area about the void (and thereby also about the planar array <NUM> of unidirectional ceramic fibers <NUM> positioned therein) is open or unobstructed. For example, the frame <NUM> may be configured such that the area above and/or below the planar array <NUM> of unidirectional ceramic fibers <NUM> is unobstructed to allow for unhindered coating of the ceramic fibers <NUM>. As shown in the cross-sectional view in <FIG>, the planar array <NUM> of unidirectional fibers <NUM> may be positioned in a medial portion of the thickness of the void <NUM> and/or frame <NUM>. When a plurality of frames <NUM> are stacked on each other in the thickness direction, the planar arrays <NUM> are there spaced from each other and the void <NUM> remains substantially unobstructed.

The frame <NUM> may support or couple to the planar array <NUM> of unidirectional ceramic fibers <NUM> across the void <NUM> via any mechanism. In some embodiments, the frame <NUM> may be configured to couple to ends or end portions of the ceramic fibers <NUM> and provide a tensile force sufficient to maintain the planar array <NUM> and unidirectional direction of the ceramic fibers <NUM>. In some embodiments, the frame <NUM> may include a tensioning mechanism that is configured to adjust the tension of the ceramic fibers <NUM>. In this way, the tensioning mechanism may be effective to apply a tension to the ceramic fibers <NUM> after the ceramic fibers <NUM> are coupled to the frame <NUM> to form (and maintain) the unidirectional, planar array <NUM> configuration of the ceramic fibers <NUM>. The tension needed to form and/or maintain the planar array <NUM> and unidirectional direction of the ceramic fibers <NUM> may vary depending upon the particular fiber composition, for example.

As noted above, the frame <NUM> may be of any configuration to form the void <NUM> and may couple with the ceramic fibers <NUM> in any manner to form the unidirectional, planar array <NUM> in the void <NUM>. One example of a configuration of the frame <NUM> is shown in <FIG>. As shown in <FIG> and <FIG>, the frame <NUM> may include an upper frame portion <NUM> and a lower frame portion <NUM>. Each of the upper frame <NUM> and the lower frame portion <NUM> may include a first fiber support member <NUM> and a second fiber support member <NUM>. The void <NUM> of the frame <NUM> may extend between the first fiber support member <NUM> and a second fiber support member <NUM>, as shown in <FIG>. As also shown in <FIG>, the frame <NUM> may include a first spacing member <NUM> and/or a second spacing member <NUM> that extend between the first and second fiber support members <NUM>, <NUM>. The void <NUM> of the frame <NUM> may also extend between the first and second spacing members <NUM>, <NUM>. The first and second fiber support members <NUM>, <NUM> and the first and second spacing members <NUM>, <NUM> may be orientated at right angles with respect to each other such that the frame <NUM> (and, potentially, the void <NUM>) is a rectangular or square shape. The first and second fiber support members <NUM>, <NUM> may act to rigidly affix and space the second fiber support members <NUM>, <NUM>.

End portions of the ceramic fibers <NUM> may be coupled to the first and second fiber support members <NUM>, <NUM> such that the unidirectional, planar array <NUM> extends there between across and/or through the void <NUM>. For example, as shown in <FIG> and <FIG> the end portions of the ceramic fibers <NUM> may be clamped or otherwise secured between the first and second fiber support members <NUM>, <NUM> of the upper portion <NUM> and the first and second fiber support members <NUM>, <NUM> of the lower portion <NUM> of the frame <NUM>, respectively. In this way, the end portions of the ceramic fibers <NUM> may be positioned between the first and second fiber support members <NUM>, <NUM> of the upper portion <NUM> and the first and second fiber support members <NUM>, <NUM> of the lower portion <NUM>, respectively, and the upper <NUM> and lower <NUM> portions may be affixed to each other to secure the ceramic fibers <NUM> to the frame <NUM>. The upper <NUM> and lower <NUM> portions of the frame <NUM> may be selectively coupled or affixed to each other such that after the planar array <NUM> of unidirectional fibers <NUM> is processed (as explained further below), the upper <NUM> and lower <NUM> portions can be selectively separated to release the end portions of the ceramic fibers <NUM> from between the first and second fiber support members <NUM>, <NUM>.

In some embodiments, the frame <NUM> example shown in <FIG> may be formed by a wrapping or winding technique. For example, one or more ceramic fibers may be wrapped or wound a plurality of times over the first and second fiber support members <NUM>, <NUM> of a pair of overlapping or stacked lower portions <NUM>, (or upper portions <NUM>) to form two planar arrays <NUM> of unidirectional fibers <NUM>. In this way, one planar array <NUM> may be formed proximate to a top surface of the "top" lower portion <NUM> of the pair of stacked lower portions <NUM> and another array <NUM> may be formed proximate to a bottom surface of the "bottom" lower portion <NUM> of the pair of stacked lower portions <NUM>. A corresponding upper portion <NUM> (or lower portion <NUM>) may be coupled to each of the stacked lower portions <NUM> to clamp or hold the one or more ceramic fibers between the upper and lower portions <NUM>, <NUM>. Two stacked frames <NUM> each including a planar array <NUM> of unidirectional fibers <NUM> may thereby be formed. Once the stacked frames <NUM> including the ceramic fibers clamped between the upper and lower portions <NUM>, <NUM> thereof are formed, any portions of the ceramic fibers extending between the frames <NUM> may be cut or trimmed to separate the frames <NUM>. Such a winding technique may thereby form a pair of frames <NUM>.

As discussed above, the illustrative frame <NUM> shown in <FIG> is only one potential frame configuration. For example, rather than capturing the end portions of the ceramic fibers <NUM> between an upper portion <NUM> and a lower portion <NUM>, the frame <NUM> may include manually engageable clamps or like fastening mechanisms that are configured to selectively couple (and detach) end portions of the ceramic fibers <NUM> to the frame <NUM>. As another example, end portions of the ceramic fibers <NUM> may be adhered or glued to the frame <NUM>. In another example, the frame <NUM> may include one or more hook, pin, channel, aperture or any other like brace structure that is configured to allow one or more of the ceramic fibers to extend thereabout or therethrough to crisscross or extend in a serpentine fashion across the void <NUM> and form the planar array <NUM> of unidirectional ceramic fibers <NUM>. In such an embodiment, a ceramic fiber may extend across the void <NUM> a first pass along a first direction to a first portion of the frame <NUM> (to form a first ceramic fiber portion <NUM>), extend about or through a brace mechanism at the first end of the frame <NUM>, and extend back across the void <NUM> a second pass that is spaced from the first pass along a second direction that is opposite the first direction to a second portion of the frame <NUM> (to form a second ceramic fiber portion <NUM>). The second portion of the frame <NUM> may also include a brace mechanism to similarly allow the ceramic fiber <NUM> to change directions and extend back across the void <NUM> along the first direction (to form a third ceramic fiber portion <NUM>). The one or more brace mechanism(s) of the frame <NUM> may be configured to space adjacent passes of the ceramic fiber across the void <NUM>, and arrange the passes of the ceramic fiber across the void <NUM> into the planar array <NUM> of unidirectional fibers <NUM>. As noted above however, the frame <NUM> may be of any configuration or design that forms a void <NUM> and provides the planar array <NUM> of unidirectional fibers <NUM> across the void <NUM>.

As shown illustrated in the flowchart of <FIG>, the apparatus <NUM> of <FIG> may facilitate or provide for a method <NUM> of processing the ceramic fibers <NUM> coupled to the frame <NUM> for the manufacture of CMC articles. For example, the apparatus <NUM> may facilitate coating the ceramic fibers <NUM> in a process <NUM>. As illustrated in <FIG>, a ceramic fiber processing method <NUM> includes providing <NUM> a plurality of frames <NUM> each including the planar array <NUM> of unidirectional ceramic fibers <NUM> extending across a void <NUM> thereof. In some embodiments, providing <NUM> a plurality of frames <NUM> may include coupling the ceramic fibers <NUM> to the plurality of frames <NUM> such that the planar array <NUM> is formed in the void <NUM> thereof. In some other embodiments, providing <NUM> a plurality of frames <NUM> may include obtaining a plurality of pre-manufactured apparatuses <NUM> containing the frames <NUM> with the planar array <NUM> formed in the voids <NUM> thereof.

The ceramic fiber processing method <NUM> further includes depositing <NUM> at least one coating on the ceramic fibers <NUM> of the planar array <NUM> of each of the plurality of frames <NUM> via a chemical vapor deposition (CVD) process, as illustrated in <FIG>. One or more frames <NUM> are positioned within a CVD reactor and processed therein to deposit a coating on the ceramic fibers <NUM> of the planar array <NUM>. The CVD reactor may be any CVD reactor effective to deposit the coating on the ceramic fibers <NUM>. In some embodiments, a plurality of frames <NUM> may be positioned with the CVD reactor and processed to deposit the coating on the ceramic fibers <NUM>. The depositing <NUM> may be performed as a batch process, such as by positioning at least one frame <NUM> in the CVD reactor, performing the deposition, and then removing the at least one frame <NUM> from the CVD reactor. As another example, the depositing <NUM> may be performed as a continuous process, such as by continuously passing at least one frame <NUM> through the CVD reactor. In such a continuous process, the multiple frames <NUM> may be coupled to one another or may be portions of a larger structure, for example, that is continuously passed through the reactor.

<FIG> illustrate the ceramic fibers <NUM> after a coating <NUM> has been deposited thereon via the CVD process <NUM>. As shown in <FIG>, the coating <NUM> may completely cover or overly the exterior surface of the ceramic fibers <NUM> of the planar array <NUM>. In some embodiments, the coating <NUM> may be a single layer of material deposited on the ceramic fibers <NUM>. In other embodiments, the coatings <NUM> may include multiple layers of the same or differing material deposited on the ceramic fibers <NUM>.

The coating <NUM> deposited on the ceramic fibers <NUM> of the planar array <NUM> positioned across the void <NUM> via the CVD process <NUM> may be any coating material utilized to process ceramic fiber for the manufacture of CMC prepregs and/or articles. For example, the coating <NUM> may be a surface modification to the ceramic fibers <NUM> that affects the fiber-matrix interface of a resulting CMC article made from the ceramic fibers <NUM>. This can be accomplished by a coating <NUM> of suitable ceramic material that inhibits the ceramic fibers <NUM> from reacting or bonding with the matrix of the CMC article. The ceramic coating <NUM> may allow the ceramic fibers <NUM> to pull out from the matrix and/or slide along the matrix, thus increasing the fracture toughness of the CMC article. However, a coating <NUM> that provides an additional and/or differing function(s) and/or other coating types (e.g., non-ceramic) may be utilized. In some embodiments, the CVD coating process <NUM> may deposit a coating <NUM> on the ceramic fibers <NUM> of the planar array <NUM> positioned across the void <NUM> including at least one layer including boron nitride, silicon-doped boron nitride, carbon, silicon carbide, silicon nitride or a combination thereof. In some such embodiments, the ceramic fibers <NUM> may be SiC fibers.

As depicted in <FIG>, the ceramic fiber processing method <NUM> further includes impregnating <NUM> the coated <NUM> unidirectional ceramic fibers <NUM> of the planar array <NUM> of one or more frames <NUM> with a slurry <NUM> including a ceramic matrix precursor composition to form one or more CMC prepreg <NUM>. The slurry <NUM> may be introduced to the frame <NUM> such that the slurry <NUM> extends about each of the coated <NUM> ceramic fibers <NUM> of the planar array <NUM>. The coated <NUM> ceramic fibers <NUM> of the planar array <NUM> may thereby be encapsulated or fully contained within the slurry <NUM>. In this way, the slurry <NUM> and the planar array <NUM> of coated <NUM> unidirectional ceramic fibers <NUM> of a frame <NUM> (i.e., the apparatus <NUM> subsequent to CVD coating) form a CMC prepreg tape <NUM>. In an alternative embodiment, the ceramic fiber processing method <NUM> may include removing the planar array <NUM> of coated <NUM> unidirectional ceramic fibers <NUM> from the void <NUM> and/or at least a portion of the frame <NUM> and impregnating <NUM> the at least partially removed coated <NUM> ceramic fibers <NUM> with the slurry <NUM>. In this way the prepregs tape <NUM> may be formed exterior to the void <NUM> of the frame and/or after separation thereof from the frame <NUM>.

The apparatus <NUM> may facilitate forming prepreg tape <NUM> (with coated ceramic fiber <NUM>) in a batch process, such as by impregnating <NUM> a plurality of planar arrays <NUM> of coated <NUM> unidirectional ceramic fibers <NUM> with the slurry <NUM> as a batch, or the planar arrays <NUM> may be impregnated <NUM> one at a time. As another example, the impregnating <NUM> may be performed as a continuous process, such as by continuously passing a plurality of frames <NUM> through a slurry <NUM> bath or otherwise continuously impregnating <NUM> a series or plurality of frames <NUM>. In such a continuous process, the multiple frames <NUM> may be coupled to one another or may be portions of a larger structure, for example, that is continuously impregnated <NUM> via a slurry <NUM> impregnating mechanism or process(es).

Once the planar array <NUM> of coated <NUM> unidirectional ceramic fibers <NUM> is impregnated with the slurry <NUM>, the resulting prepreg <NUM> may be allowed to dry/set up and/or otherwise processed into a more easily handled form. Thereafter, the prepreg <NUM> may be removed from the frame <NUM> (if the prepreg <NUM> is formed in the frame <NUM>). For example, the prepreg <NUM> may be decoupled from the frame <NUM> via the same mechanism previously utilized to couple the pre-coated and/or pre-impregnated ceramic fiber <NUM> to the frame <NUM>. In some embodiments, the prepreg <NUM> may include portions of uncoated and/or non-impregnated ceramic fiber <NUM> extending from portion including coated and impregnated ceramic fiber <NUM>. In such an embodiment, the uncoated and/or non-impregnated ceramic fiber <NUM> may be trimmed or otherwise removed from the coated and impregnated ceramic fiber <NUM> portion of the prepreg <NUM>.

The slurry <NUM> may include any ceramic matrix precursor composition effective to form a CMC prepreg <NUM> and, ultimately, a CMC article. For example, the CMC prepreg <NUM> may be utilized to make a CMC article through a melt infiltration (MI) process, a chemical vapor infiltration (CVI) process, or any other process(es). The slurry <NUM> may be composition particularly suited to SiC ceramic fibers <NUM>. In some embodiments, the slurry <NUM> may include an oxide-based ceramic matrix precursor composition. In some embodiments, the slurry <NUM> may include at least one of SiC, TiC, TiB, TiB2, ZrC, HfC, TaC, NbC, ZrSiC, TiSiC, C, Y2O3, ZrO2, Si3N4, Al2O3, ZrO2, SiO2, TiO2 and combinations thereof. For example, the ceramic fibers <NUM> may be SiC fibers and the slurry may be a SiC ceramic matrix precursor composition to form a SiC-SiC CMC article from the prepreg <NUM>.

<FIG> also illustrate the coated ceramic fibers <NUM> after being impregnated <NUM> with the slurry <NUM>. As shown in the cross-sectional view of <FIG>, a solid base plate <NUM> may be coupled to the frame <NUM> such that a side of the void <NUM> is substantially sealed. In some embodiments, at least an interior surface of the base plate <NUM> is adjacent the ceramic fibers <NUM>, and such interior surface may be substantially planar. At least the interior surface of the base plate <NUM> may thereby extend substantially parallel to the planar array <NUM> of the ceramic fibers <NUM>. The frame <NUM> may be configured such that an area of the void <NUM> above the base plate <NUM> in a thickness direction is also substantially sealed. The thickness direction may extend substantially normal to the planar array <NUM>. The frame <NUM> and the base plate <NUM> may thereby enclose a portion of the void <NUM> to form a well or receptacle capable of holding the slurry <NUM> therein. Slurry <NUM> can thereby be introduced into the void <NUM> and contained therein by the frame <NUM> and the base plate <NUM>. As another example, the base plate <NUM> may be aligned with or positioned above the frame <NUM> and adjacent to the planar array <NUM> such that the base plate provides for tape casting of the planar array <NUM> with slurry <NUM> to form prepreg tape. The base plate <NUM> a may be otherwise configured to provide for tape casting of the planar array <NUM> with the slurry <NUM> to form to form prepreg tape.

In one example, the planar array <NUM> may be spaced above the base plate <NUM> but below a top surface of the frame <NUM> in the thickness direction, as shown in <FIG>. The well formed by the frame <NUM> and the base plate <NUM> may thereby contain the planar array <NUM>. Enough slurry <NUM> may be introduced into the void <NUM> such that the slurry <NUM> extends below the ceramic fibers <NUM>, between the ceramic fibers <NUM>, and above the ceramic fibers <NUM>. However, as explained above, a well may or may not be formed by the base plate <NUM>. The thickness of the prepreg tape <NUM> formed by the apparatus <NUM> may be controlled, in part, by the space between the base plate <NUM> and the ceramic fibers <NUM> and the amount of slurry <NUM> extending over the top of the ceramic fibers <NUM>. In some embodiments, the apparatus <NUM> may be configured such that the planar array <NUM> of ceramic fibers <NUM> is evenly spaced above the base plate <NUM> and below the top surface of the frame <NUM> in the thickness direction, for example, as shown in <FIG>. In such an embodiment, the slurry <NUM> may be introduced into and substantially fill the void <NUM>. The top surface of the frame <NUM> may be used as a knifing or screening reference to form a prepreg <NUM> with an equal amount of matrix precursor above and below the planar array <NUM> of ceramic fibers <NUM>. In other embodiments, the planar array <NUM> of ceramic fibers <NUM> may not be spaced below the top surface of the frame <NUM> and/or the top surface of the frame <NUM> may not be used a knifing or screening reference.

While one illustrative frame <NUM> embodiment is shown in <FIG> for impregnating <NUM> the planar array <NUM> of coated <NUM> unidirectional ceramic fibers <NUM> of the frame <NUM> with a ceramic matrix precursor slurry <NUM> to form a CMC prepreg <NUM>, any arrangement or configuration may be utilized that is effective in impregnating <NUM> the planar array <NUM> with the slurry <NUM>. For example, as discussed above at least a portion of the frame <NUM> may be removed from the planar array <NUM> of coated <NUM> unidirectional ceramic fibers <NUM> prior to the impregnating <NUM>. As another example, a second backing plate may be utilized to seal the open side of the void <NUM>, and at least one of the backing plates may include a port for introducing the slurry <NUM> into the sealed void <NUM>.

An example of the apparatuses and methods of processing ceramic fiber disclosed herein was carried out. A pair of graphite frame portions, as discussed below, were configured with substantially planar arrays of unidirectional SiC fibers. The planar arrays of substantially unidirectional SiC fibers were coated with a CVD process, and the coated SiC fibers were impregnated with a SiC-containing slurry to produce a prepreg tape.

The frame portions were about <NUM> inches in length, about <NUM> inches in width, and about <NUM> inches in thickness in outer dimensions. The frame portions formed a void of about <NUM> inches in length, <NUM> inch in width and <NUM> inches in thickness. The two frames were fastened together with pins in a stacked relationship, i.e., an upper frame portion and a lower frame portion were stacked to form a single frame construct. A single length, of approximately <NUM>, of SiC fiber tow was wound around the frame construct such that the tow formed two substantially unidirectional planar arrays oriented lengthwise along the voids. The SiC tows were bundles of approximately <NUM> filaments of approximately <NUM> microns in diameter. The two free ends of the tow were fastened to the frame construct on the spacing members of the frame portions using a carbon glue.

The frame construct with the two substantially unidirectional planar arrays was disposed in a high-temperature, low-pressure CVD reactor as a batch process, and three coatings were deposited sequentially on the fibers of the tow adjacent and across the voids: boron nitride, silicon-doped boron nitride and silicon nitride. The frame construct was subsequently disposed in a high-temperature, atmospheric CVD reactor, and a pyrolytic carbon coating was deposited on the fibers.

The two frame portions of the frame construct were separated after coating of the fibers. The regions of the two fiber arrays that passed over the support members of the frame portions were fastened to the support members, and the fibers were cut at the upper and lower sides of the frame portions at the point where the fibers wound around the length-ends of the frame portions. Each separated individual frame portion was disposed on a metal block that acted as the base plate and defined the space about the coated fiber arrays for infiltration. A sheet of Mylar was disposed between the metal block and the coated fiber arrays. A slurry containing SiC was disposed into the frame portions using a reservoir with an opening to dispense the slurry. The slurry was introduced from one length end of the frame portions to the other length end. The slurry impregnated the coated fiber arrays coupled to the frame portions. The slurry was allowed to dry and thereby form prepreg tapes. The tapes were finally removed from the frame portions.

Claim 1:
A method (<NUM>) of processing ceramic fiber (<NUM>) for the manufacture of a ceramic matrix composite (CMC) article, comprising:
providing (<NUM>) at least one frame (<NUM>) including a planar array (<NUM>) of unidirectional ceramic fibers (<NUM>) extending across a void (<NUM>) thereof; and
depositing (<NUM>) a coating on the ceramic fibers (<NUM>) of the at least one frame (<NUM>) via a chemical vapor deposition (CVD) process; and
impregnating (<NUM>) the coated ceramic fibers (<NUM>) of the at least one frame (<NUM>) with a slurry (<NUM>) including a ceramic matrix precursor composition to form at least one CMC prepreg tape (<NUM>), wherein impregnating (<NUM>) the coated ceramic fibers (<NUM>) includes removing the coated ceramic fibers (<NUM>) from at least a portion of the at least one frame (<NUM>) and impregnating (<NUM>) the removed coated ceramic fibers (<NUM>) with the slurry (<NUM>).