Patent Description:
A gas turbine engine typically includes at least a compressor section, a combustor section and a turbine section. The compressor section pressurizes air into the combustion section where the air is mixed with fuel and ignited to generate an exhaust gas flow. The exhaust gas flow expands through the turbine section to drive the compressor section and, if the engine is designed for propulsion, a fan section.

The turbine section may include multiple stages of rotatable blades and static vanes. An annular shroud or blade outer air seal may be provided around the blades in close radial proximity to the tips of the blades to reduce the amount of gas flow that escapes around the blades. The shroud typically includes a plurality of arc segments that are circumferentially arranged in an array. The arc segments are exposed to relatively hot gases in the gas flow path and may be configured to receive cooling airflow to cool portions of the shrouds.

<CIT> discloses a seal assembly for a gas turbine engine that has a sealing portion that extends circumferentially between first and second mate faces and an engagement portion along the first mate face.

<CIT> and so cannot be taken into account when considering the inventive step of the claims of the present application, describes a seal assembly for a gas turbine engine that includes a support mountable to an engine static structure. A seal has a sealing portion that extends from an engagement portion. The sealing portion has a sealing face that extends circumferentially between first and second mate faces. An overwrap has one or more plies that follow a perimeter of the engagement portion to define an interface between the retention hooks and the engagement portion.

<CIT> discloses a cylindrical shroud constituted of a plurality of circular arc plate-shaped segments divided in the circumferential direction. Both edges in the main gas direction of each segment are supported with a supporting member fixed to the inner circumference side of a gas turbine casing. Each segment is constituted of ceramic.

<CIT> discloses an airfoil including a main body extending between a leading edge and a trailing edge separated in a chordwise direction and extending between a tip and a root in a spanwise direction. The main body defines a suction side and a pressure side separated in a thickness direction and a plurality of channels extending inwardly from at least one of said suction and pressure sides. A composite cover is attached to the main body.

<CIT> discloses a high temperature seal that may include an interior region comprising a material that swells when exposed to a high temperature environment and at least one projection that is able to be inserted into a slot, and a coating that substantially prevents swelling to coated areas of the interior region.

According to the invention a seal assembly for a gas turbine engine as set out by claim <NUM> is provided.

In a further embodiment of any of the foregoing embodiments, the internal cavity spans circumferentially between the mate faces.

In a further embodiment of any of the foregoing embodiments, the platform insert is dimensioned to extend within the sealing portion between opposed portions of the overwrap.

In a further embodiment of any of the foregoing embodiments, the platform insert comprises a metal material and/or a ceramic material.

In a further embodiment of any of the foregoing embodiments, the at least one intermediate ply comprises a fabric.

In a further embodiment of any of the foregoing embodiments, the fabric is woven.

In a further embodiment of any of the foregoing embodiments, the one or more core plies are triaxially braided.

In a further embodiment of any of the foregoing embodiments, the one or more overwrap plies are biaxially braided.

A further embodiment of any of the foregoing embodiments includes at least one mounting block including an interface portion extending from a mounting portion. The engagement portion includes a pair of openings along respective ones of the mate faces, and the interface portion is dimensioned to be inserted into one of the openings to limit relative movement between the at least one mounting block and the seal.

In a further embodiment of any of the foregoing embodiments, the platform insert is dimensioned to extend between opposed portions of the overwrap that establish leading and trailing edge segments of the sealing portion. The leading and trailing edge segments extend circumferentially between the mate faces. The one or more core and overwrap plies include silicon carbide fibers embedded in a ceramic matrix. The one or more core plies comprise a plurality of core plies that are triaxially braided and include axial tows interlaced with bias tows, and a bias angle of each of the bias tows is between approximately <NUM> degrees and approximately <NUM> degrees, absolute. The one or more overwrap plies comprise a plurality of overwrap plies that are biaxially braided and include a first set of bias tows interlaced with a second set of bias tows, and a bias angle of each of the first and second sets of bias tows is between approximately <NUM> degrees and approximately <NUM> degrees, absolute. The fabric is a <NUM> or <NUM> harness satin weave including warp tows interlaced with weft tows, and the warp tows or the weft tows are dimensioned to substantially span between the mate faces.

In a further embodiment of any of the foregoing embodiments, the seal is a blade outer air seal (BOAS).

In a further embodiment according to the invention there is provided a gas turbine engine as set out in claim <NUM>.

In a further embodiment of any of the foregoing embodiments, the mounting blocks are mechanically attached to the engine case. The mounting blocks span across the intersegment gap established by the mate faces of the respective adjacent pair of seals. Each of the mounting blocks includes an interface portion having a dovetail geometry that extends through an opening along a respective one of the mate faces to mate with ramped surfaces of the internal cavity and limit movement of the respective seal relative to the engine case.

In a further embodiment of any of the foregoing embodiments, the platform insert includes at least one intermediate ply having a third fiber construction of substantially discontinuous fibers.

In a further embodiment of any of the foregoing embodiments, the at least one intermediate ply comprises a woven fabric, the core plies are triaxially braided, and the overwrap plies are biaxially braided.

In a further embodiment of any of the foregoing embodiments, the core and overwrap plies include silicon carbide fibers embedded in a ceramic matrix.

The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description of an embodiment.

The geared architecture <NUM> may be an epicycle gear train, such as a planetary gear system or other gear system, with a gear reduction ratio of greater than about <NUM>:<NUM>.

The fan section <NUM> of the engine <NUM> is designed for a particular flight condition -- typically cruise at about <NUM> Mach and about <NUM>,<NUM> feet (<NUM> meters). The flight condition of <NUM> Mach and <NUM>,<NUM> ft (<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. "Low corrected fan tip speed" is the actual fan tip speed in ft/sec divided by an industry standard temperature correction of [(Tram °R) / (<NUM> °R)]^<NUM>. The "Low corrected fan tip speed" as disclosed herein according to one non-limiting embodiment is less than about <NUM> ft / second (<NUM> meters / second).

<FIG> shows selected portions of the turbine section <NUM> including a rotor <NUM> carrying one or more blades or airfoils <NUM> that are rotatable about the engine axis A. In this disclosure, like reference numerals designate like elements where appropriate and reference numerals with the addition of one-hundred or multiples thereof designate modified elements that are understood to incorporate the same features and benefits of the corresponding original elements. Each airfoil <NUM> includes a platform <NUM> and an airfoil section <NUM> extending in a radial direction R from the platform <NUM> to a tip <NUM>. The airfoil section <NUM> generally extends in a chordwise or axial direction X between a leading edge <NUM> and a trailing edge <NUM>. A root section <NUM> of the airfoil <NUM> is mounted to, or integrally formed with, the rotor <NUM>. A blade outer air seal (BOAS) <NUM> is spaced radially outward from the tip <NUM> of the airfoil section <NUM>. The BOAS <NUM> can include a plurality of seal arc segments (one exemplary BOAS shown in <FIG> at <NUM>) that are circumferentially arranged in an annulus around the engine axis A. An array of the BOAS <NUM> are circumferentially distributed about an array of the airfoils <NUM> to bound a gas path such as the core flow path C.

A vane <NUM> is positioned along the engine axis A and adjacent to the airfoil <NUM>. The vane <NUM> includes an airfoil section 72A extending between an inner platform 72B and an outer platform 72C to define a portion of the core flow path C. The turbine section <NUM> includes an array of airfoils <NUM>, vanes <NUM>, and BOAS <NUM> arranged circumferentially about the engine axis A.

One or more cooling sources CS (one shown) are configured to provide cooling air to one or more cooling cavities or plenums <NUM> defined by an engine static structure such as the engine case <NUM> or another portion of the engine static structure <NUM> (<FIG>). In the illustrated example of <FIG>, the plenums <NUM> are defined between an engine case <NUM> and the outer platform 72C and/or BOAS <NUM>. The engine case <NUM> provides a portion of the engine static structure <NUM> (<FIG>) and extends along the engine axis A. The plenums <NUM> are configured to receive pressurized cooling flow from the cooling source(s) CS to cool portions of the airfoil <NUM>, BOAS <NUM> and/or vane <NUM>. Cooling sources CS can include bleed air from an upstream stage of the compressor section <NUM> (<FIG>), bypass air, or a secondary cooling system aboard the aircraft, for example. Each of the plenums <NUM> can extend in a circumferential or thickness direction T between adjacent airfoils <NUM>, BOAS <NUM> and/or vanes <NUM>. The tips <NUM> of each of the airfoil sections <NUM> and adjacent BOAS <NUM> are in close radial proximity to reduce the amount of gas flow that escapes around the tips <NUM> through a corresponding clearance gap.

<FIG> illustrate an exemplary seal assembly <NUM> including a seal <NUM> for a gas turbine engine, which can be incorporated into the engine <NUM> of <FIG> or the turbine section <NUM> of <FIG>, for example. In the illustrated example of <FIG>, the seal <NUM> is a blade outer air seal (BOAS). <FIG> is sectional view of the seal assembly <NUM> in an installed position. <FIG> is a sectional view of an adjacent pair of seal assemblies <NUM> (indicated as 176A, 176B). Although the components discussed herein primarily refer to a BOAS in the turbine section <NUM>, the teachings herein can also be utilized for other components of the engine <NUM>, such as one of the platforms <NUM>, 72B, 72C, an upstream stage of the compressor section <NUM>, or combustor panels or liners defining portions of a combustion chamber located in the combustor section <NUM>, and exhaust nozzles.

Referring to <FIG>, each seal assembly <NUM> includes a seal <NUM> and at least one support or mounting block <NUM>. Each seal <NUM> is arranged in close proximity to an airfoil tip <NUM> during operation of the engine. An array of the seals <NUM> are distributed about an array of blades or airfoils <NUM> to bound a gas path GP. One pair of seals 169A, 169B is shown in <FIG> for illustrative purposes. The gas path GP can be a portion of the core flow path C of <FIG>, for example.

Referring to <FIG>, the seal <NUM> includes a main body <NUM> that extends circumferentially between opposed (or first and second) mate faces <NUM>. The main body <NUM> can have a generally elongated and arcuate profile, as illustrated by <FIG>. The seal <NUM> includes a sealing portion <NUM> that extends circumferentially between the mate faces <NUM>. The sealing portion <NUM> includes a seal face <NUM> that extends circumferentially between the mate faces <NUM>, with exposed surfaces of the seal face <NUM> bounding the gas path GP. The main body <NUM> includes an engagement portion <NUM> extending radially outwardly from the sealing portion <NUM>. The engagement portion <NUM> extends radially outwardly from the sealing portion <NUM> along at least one of the mate faces <NUM>. In the illustrative example of <FIG>, the engagement portion <NUM> extends circumferentially between the mate faces <NUM>. The engagement portion <NUM> includes a backside face <NUM> (<FIG>) opposite the seal face <NUM> relative to the radial direction R.

The seal <NUM> includes an internal cavity <NUM> established by the main body <NUM>. The internal cavity <NUM> extends inwardly from a pair of openings <NUM> along each of the respective mate faces <NUM>. The engagement portion <NUM> defines a portion of the internal cavity <NUM>, as illustrated by <FIG>. The internal cavity <NUM> can be substantially enclosed along the main body <NUM> between the openings <NUM>, as illustrated by <FIG>. The internal cavity <NUM> can be dimensioned to span or extend circumferentially between the mate faces <NUM>. The internal cavity <NUM> can be configured to receive cooling flow in operation, such as from the cooling source CS (<FIG>), to cool adjacent portions of the seal <NUM>.

In the illustrative example of <FIG>, seal <NUM>' includes at least one opening such as an elongated slot <NUM>' extending radially between internal cavity <NUM>' and a backside face <NUM>' of the seal <NUM>'. The slot <NUM>' can be dimensioned to extend along a length of the internal cavity <NUM>', as illustrated by <FIG>. In examples, the slot <NUM>' extends a first width W1 (<FIG>), and the retention feature <NUM> extends a second width W2 (<FIG>). The first width W1 is less than the second width W2. The engagement portion <NUM> extends a third width W3 (<FIG>) in the thickness direction T. The slot <NUM>' can be dimensioned such that the first width W1 is no more than approximately <NUM> or <NUM> percent of the third width W3 for each position, or at least a majority of positions, along the slot <NUM>'. The slot <NUM>' can be utilized to compensate for differential thermal growth and reduce thermal stresses in the component.

Referring to <FIG> and <FIG>, with continuing reference to <FIG> and <FIG>, each mounting block <NUM> secures one or more of the seals <NUM> to a housing such as engine case <NUM>, or to another portion of the engine static structure <NUM> (<FIG>). The mounting block <NUM> includes at least one interface portion <NUM> extending outwardly from a main body or mounting portion <NUM>. In the illustrated example of <FIG> and <FIG>, the mounting block <NUM> includes a pair of opposed interface portions <NUM> that extend outwardly from the mounting portion <NUM>. Each interface portion <NUM> is dimensioned to abut the engagement portion <NUM> of the respective seal <NUM> to limit relative movement between the mounting block <NUM> and the seal <NUM> in the radial and/or circumferential directions, for example.

A cross-section of the mounting block <NUM> can have a generally trapezoidal geometry, as illustrated by <FIG> and <FIG>. Ends of the interface portions <NUM> can be contoured to guide the interface portions <NUM> during insertion into the respective internal cavities <NUM> in an installed position. In the illustrative example of <FIG> and <FIG>, each of the interface portions <NUM> has a dovetail geometry. Surfaces of each interface portion <NUM> slope outwardly between a top 182A and bottom 182B of the mounting portion <NUM>. The dovetail geometry and contouring of the interface portions <NUM> can reduce mechanical stress on the seal <NUM>, including seals made of a composite material which can be strong but relative brittle. The dovetail geometry of the interfaces portion <NUM> circumferentially overlaps with the engagement portions <NUM> when in the installed position to secure adjacent pairs of the seal assemblies <NUM> to the engine case <NUM>, as illustrated by the seal assemblies 176A, 176B of <FIG>.

Each interface portion <NUM> can include an outwardly extending retention feature <NUM>. The retention feature <NUM> is dimensioned to abut against surfaces of the engagement portion <NUM> to seat the seal <NUM> during assembly and limit circumferential and/or radial movement, as illustrated by the retention features <NUM> of <FIG>.

The mounting block <NUM> can be mechanically attached or otherwise secured to the engine case <NUM> using one or more fasteners <NUM> (one shown in <FIG> for illustrative purposes). Each mounting portion <NUM> defines an aperture <NUM> that receives a respective fastener <NUM> to mechanically attach the mounting portion <NUM> to the engine case <NUM> and limit relative movement of one or more seals <NUM>. In the illustrated example of <FIG>, the fastener <NUM> is a bolt, and the aperture <NUM> threadably receives a length of the bolt. Other fasteners such as pins, rivets and clips, and other techniques such as welding can be utilized to secure the mounting block <NUM> to the engine static structure <NUM>.

The seal assemblies 176A, 176B are arranged in close proximity such that the respective mate faces 178A, 178B establish an intersegment gap G that extends a distance in the circumferential direction T, as illustrated in <FIG>. The mounting block <NUM> is dimensioned to span across the intersegment gap G. A portion of the fastener <NUM> can be circumferentially aligned with one or more of the adjacent mate faces 178A, 178B and/or the intersegment gap G. The mounting block <NUM> is arranged between the engagement portions 179A, 179B to circumferentially space apart the seals 169A, 169B. Each mounting block <NUM> secures an adjacent pair of the engagement portions 179A, 179B to the engine case <NUM> when in the installed position.

Each engagement portion 179A, 179B includes ramped surfaces 186A, 186B extending along the internal cavity 184A, 184B. The ramped surfaces 186A, 186B extend transversely from internal surfaces bounding the internal cavity 184A, 184B. Each interface portion <NUM> of the mounting block <NUM> is dimensioned to be inserted into or otherwise extend through a respective one of the openings 185A, 185B to abut against and mate with the ramped surfaces 186A, 186B to support the adjacent seals 169A, 169B and to limit or bound circumferential, radial and/or axial movement of the seals 169A, 169B relative to the engine case <NUM> and engine axis A.

The seal <NUM> can include slots <NUM> along the respective mate faces <NUM>, as illustrated by <FIG>. Each slot <NUM> can be dimensioned to extend along surfaces of the platform insert <NUM>, as illustrated by <FIG>. Each slot <NUM> can be dimensioned to receive a seal member SM (shown in dashed lines in <FIG> for illustrative purposes). The seal member SM can be a feather seal, for example, and can be dimensioned to span between the mate faces <NUM> of adjacent seals <NUM> to reduce a likelihood of ingestion of hot combustion gases from the gas path GP being communicated into and through the intersegment gap G, as illustrated by the arrangement of the mate faces 178A, 178B and seal member SM of <FIG>. The slots <NUM> can be formed by an ultrasonic machining technique, for example. The slot <NUM> can be dimensioned to substantially align with a direction of adjacent core and/or overwrap layers CL, OL, which can reduce a likelihood of strength degradation of the adjacent layers CL, OL.

Various materials can be utilized to form the seal <NUM> and mounting block <NUM>. The seal <NUM> is made of a first material, and the mounting block <NUM> is made of a second material, which can be the same or can differ from the first material. For example, the first material can include a ceramic or ceramic matrix composite (CMC) material such as silicon carbide (SiC) fibers in a silicon carbide (SiC) matrix. The seal <NUM> can be formed from one or more layers L (<FIG>) of a composite layup. In other examples, the seal <NUM> is made of another material, such as a high temperature metal, alloy, or composite material. The mounting block <NUM> can be made of a high temperature composite, metal, or alloy, such as a nickel-based superalloy, for example. The seal <NUM> can have a unitary construction. In other examples, the sealing portion <NUM> and engagement portion <NUM> are separate and distinct components that are mechanically attached to one another with one or more fasteners.

In the illustrative example of <FIG>, the seal <NUM> is formed from a plurality of plies or layers L (see also L' of <FIG>). The main body <NUM> of the seal <NUM> includes at least a core <NUM> and an overwrap <NUM>. The main body <NUM> can include a platform insert <NUM> dimensioned to extend between portions of the core <NUM> and the overwrap <NUM> to establish at least the sealing portion <NUM>, as illustrated by <FIG>. The platform insert <NUM> can have a substantially planar geometry and can be dimensioned to extend within the sealing portion <NUM> between opposed portions of the overwrap <NUM>, including portions of the overwrap <NUM> that establish leading and trailing edge segments 177LE, 177TE of the sealing portion <NUM>, as illustrated by <FIG>. The leading and trailing edge segments 177LE, 177TE extend circumferentially between the mate faces <NUM>. The platform insert <NUM> has a third construction, which can be the same or can differ from the first and/or second fiber constructions. For example, the platform insert <NUM> can be a monolithic component constructed from a metal material, a glass material and/or a ceramic material, which can be the same or different ceramic material as the core <NUM> and/or overwrap <NUM>. In examples, the platform insert <NUM> is made of a homogenous monolithic ceramic or glass-ceramic. Example metal materials can include high temperature metals or alloys, including any of those disclosed herein.

In examples, the platform insert <NUM> includes at least one or more interstitial or intermediate (or platform) plies or layers <NUM>. The main body <NUM> can include one or more fillers <NUM>. The intermediate layer(s) <NUM> and/or fillers <NUM> can be situated between portions of the core <NUM> and/or overwrap <NUM> to establish the sealing portion <NUM>, as illustrated in <FIG>. Various materials can be utilized to form the intermediate layer(s) <NUM> and filler(s) <NUM>, including any of the materials disclosed herein. The intermediate layer(s) can serve to increase rigidity of the sealing portion <NUM> adjacent to regions established by the fillers <NUM> and can improve thermal performance along the gas path wall established by the sealing portion <NUM>.

The core <NUM> includes one or more core plies or layers CL. The overwrap <NUM> includes one or more overwrap plies or layers OL. The layers L of the seal <NUM> comprise the core and overwrap layers CL, OL and the intermediate layer(s) <NUM>. In the illustrative example of <FIG>, the seal <NUM> includes six separate and distinct core plies CL, three separate and distinct overwrap plies OL, and two separate and distinct intermediate layers <NUM>. It should be understood that fewer or more than six core plies CL, three overwrap pies OL and two intermediate layers <NUM> can be utilized in accordance with the teachings disclosed herein.

The core and overwrap plies CL, OL and intermediate layers <NUM> are arranged in stacked relation to establish the main body <NUM> of the seal <NUM>. The core plies CL are arranged to establish an inner, generally tubular shaped box. The overwrap plies OL are arranged to establish an outer, generally tubular shaped box that substantially encloses the inner box to establish a double box architecture. The inner box established by the core plies CL can serve to provide structural support, and the outer box established by the overwrap plies OL can serve to provide additional structural support and enclose other features such as the intermediate layer(s) <NUM> and filler(s) <NUM> to establish a cross-sectional profile of the seal <NUM>.

The core and/or overwrap plies CL, OL and/or intermediate layer(s) <NUM> can be dimensioned to extend from, and span circumferentially between, the mate faces <NUM>. The continuous inner and outer box arrangement can reduce a likelihood of delamination of the plies CL, OL. The core plies CL are arranged to establish the internal cavity <NUM>. The overwrap plies OL of the overwrap <NUM> are arranged to follow a perimeter P of the core <NUM> comprising the core plies CL to establish the sealing portion <NUM> and engagement portion <NUM>. The overwrap <NUM> can be dimensioned to surround the perimeter P of the core plies CL at circumferential positions along the internal cavity <NUM>, as illustrated by <FIG>. The core plies CL follow an inner periphery or passageway OP of the overwrap <NUM>, as illustrated by <FIG>. The core plies CL establish the ramped surfaces <NUM> and can be arranged to space apart the overwrap plies OL of the overwrap <NUM> from the internal cavity <NUM>, as illustrated by <FIG>. The ramped surfaces <NUM> can be utilized to improve non-binding thermal growth of the mounting block <NUM>. The internal cavity <NUM> can serve to provide an area where a cross section of the seal <NUM> is allowed to change to accommodate thermal distortions of the engine case <NUM>.

Various materials can be utilized to form the core and overwrap plies CL, OL and the intermediate layer(s) <NUM>. The plies CL, OL and/or intermediate layer(s) <NUM> can be constructed from fibers made of the same material or different materials. In examples, the core plies CL, overwrap plies OL and/or intermediate layer(s) <NUM> include silicon-based fibers in a silicon-based ceramic matrix such as silicon carbide fibers (SiC) in a silicon carbide (SiC) matrix to establish a ceramic matrix composite (CMC) component. Other materials can be utilized to construct the core plies CL, overwrap plies OL and/or intermediate layer(s) <NUM>, and corresponding matrix materials, such as oxide-based chemistries.

Various fiber constructions can be utilized for the core and overwrap plies CL, OL and intermediate layer(s) <NUM>. The core plies CL have a first fiber construction. The overwrap plies OL have a second fiber construction, which can be the same or can differ from the first fiber construction. Each intermediate layer <NUM> of the platform insert <NUM> has a third fiber construction, which can be the same or can differ from the first and/or second fiber constructions. The first, second and third fiber constructions can include any of the fiber constructions or patterns disclosed herein. Example fiber constructions include unidirectional fibers and fabrics including woven fibers.

In examples, the first and second fiber constructions of the core and overwrap plies CL, OL comprise substantially continuous fibers, and the third fiber construction of each intermediate layer <NUM> comprises substantially discontinuous fibers. For the purposes of this disclosure, the term "continuous" means a construction in which fibers in the respective ply or layer wrap or extend more than one full rotation about an axis of the component. For the purposes of this disclosure, the term "discontinuous" means a construction in which fibers in the respective ply or layer do not wrap or extend more than one full rotation about an axis of the component. For the purposes of this disclosure, the term "substantially" with respect to "continuous" means a construction in which at least <NUM>% of the bias and other non-axial fibers in the respective ply or layer wrap or extend more than one full rotation about an axis of the component. For the purposes of this disclosure, the term "substantially" with respect to "discontinuous" means a construction in which no more than <NUM>% of the fibers or tows of fibers in the respective ply or layer wrap or extend more than one full rotation about an axis of the component.

<FIG> illustrate example fiber constructions <NUM> (indicated at 189A-<NUM>). In examples, the core and/or overwrap plies CL, OL are constructed from braided plies including a plurality of braided yarns forming a weave, and the intermediate layer(s) <NUM> are constructed from a woven fabric. For example, the overwrap plies OL can include a plurality of biaxially braids 189A (shown in <FIG>), and core plies CL can include a plurality of triaxially braids 189B (shown in <FIG>), or vice versa. In other examples, the layup of the core and/or overwrap plies CL, OL include alternating layers of biaxially braided and triaxially braided plies.

Referring to <FIG>, the biaxially braid 189A includes a first set of bias tows 189A-<NUM> interlaced with a second set of bias tows 189A-<NUM>. The bias tows 189A-<NUM>, 189A-<NUM> are illustrated as being arranged in a 2x2 pattern. However, other patterns such as a <NUM>×<NUM> pattern can be utilized. The bias tows 189A-<NUM>, 189A-<NUM> are arranged to establish respective positive and negative bias angles α with respect to a longitudinal axis LA generally extending in a braid direction BD. The tows can be arranged such that the <NUM>° angle used herein has a major component extending in the circumferential direction X (<FIG>) of the seal <NUM>. The bias angle α of each of the bias tows 189A-<NUM>, 189A-<NUM> can be less than or equal to approximately <NUM> degrees, absolute. In examples, the bias angle α of each of the bias tows 189A-<NUM>, 189A-<NUM> approaches <NUM> degrees, absolute, such as between approximately <NUM> degrees and approximately <NUM> degrees, absolute. For purposes of this disclosure the terms "substantially" and "approximately" mean ±<NUM>% of the stated value unless otherwise disclosed. In examples, the second fiber construction of each overwrap ply OL is a +/- <NUM>° biaxial braid. The relatively shallow bias angles α of the bias tows 189A-<NUM>, 189A-<NUM> can compensate for a lack of axial fibers in the respective ply.

Referring to <FIG>, the triaxially braid 189B includes first and second sets of bias tows 189B-<NUM>, 189B-<NUM> and a set of axial tows 189B-<NUM> interlaced with the bias tows 189B-<NUM>, 189B-<NUM>. Each axial tow 189B-<NUM> is arranged along a longitudinal axis LA generally extending in a braid direction BD. The bias tows 189B-<NUM>, 189B-<NUM> are arranged to establish respective positive and negative bias angles α with respect to the longitudinal axis LA. In examples, the bias angle α of each of the bias tows 189B-<NUM>, 189B-<NUM> is greater than or equal to approximately <NUM> degrees, absolute. In examples, the bias angle α of each of the bias tows 189B-<NUM>, 189B-<NUM> approaches <NUM> degrees, absolute, such as between approximately <NUM> degrees and approximately <NUM> degrees, absolute. For the purposes of this disclosure, the <NUM>° position is normal to the axial or braid direction BD. In examples, the first fiber construction of each core ply CL is a <NUM>°, +/- <NUM>° triaxial braid. The axial tows can provide thermal resistance to thermal uncurling. The relatively steep bias angles α of the bias tows 189B-<NUM>, 189B-<NUM> can improve strength in the hoop direction (e.g., thickness and/or radial directions R, T).

The biaxial braid 189A and triaxial braid 189B can include different fiber types in the braid axial and braid bias directions to tailor the strength and stiffness of the core and/or overwrap plies CL, OL. For example, higher modulus fibers may be used in conjunction with lower modulus fibers. Other fiber constructions can be utilized to form the core and/or overwrap plies CL, OL, including any of the fiber constructions disclosed herein.

Example fabrics include a three-dimensional woven fabric 189C (<FIG>), a non-crimp fabric 189D (<FIG>), and/or a two-dimensional woven fabric 189E (<FIG>) can be utilized to form any of the layers CL, OL and/or intermediate layers <NUM> disclosed herein. Other example fabrics that can be utilized include satin weaves. Example satin weaves include four-to-eight harness satin weaves such as a four-harness satin weave 189F (<FIG>), a five-harness satin weave <NUM> (<FIG>) and an eight-harness satin weave <NUM> (<FIG>) having warp tows 189F-<NUM>/<NUM>-<NUM>/<NUM>-<NUM> interlaced with weft tows 189F-<NUM>/<NUM>-<NUM>/<NUM>-<NUM>. Other example configurations include a plain weave (<FIG>), and a twill weave 189I including warp tows 189I-<NUM> interlaced with weft tows 189I-<NUM> (disclosed as a 2x2 pattern in <FIG>). The warp tows or the weft tows can be dimensioned to substantially span between the mate faces <NUM>. Other example constructions include a one-dimensional unidirectional pattern 189J (<FIG>). There may also be variations within each fiber construction, such as the relative angles of the fibers and tows relative to one another. In examples, the intermediate layer <NUM> is constructed from a section of a biaxial or triaxial braided weave in which the continuous fibers are severed and the section is flattened or otherwise formed with respect to a predefined geometry of the platform insert <NUM>.

<FIG> illustrates a process of constructing or forming a component in a flow chart <NUM>. The process <NUM> can be utilized to form a gas turbine engine component, including the seals <NUM>, <NUM>, or another component such as static vanes and struts, for example. Reference is made to the seal <NUM> of <FIG> for illustrative purposes, which disclose exemplary states of fabrication of the component in the process <NUM>.

Referring to <FIG>, a core <NUM> of a main body <NUM> is formed at step 296A. Step 296A includes laying up or forming one or more core plies CL along at least one mandrel M. The core plies CL can include any of the materials and fiber constructions disclosed herein. In examples, a total of six core plies CL are triaxially braided about or over the mandrel M. In the illustrative example of <FIG>, the mandrel M includes a pair of mandrels M-<NUM>, M2 arranged in an opposed relationship. The mandrels M-<NUM>, M2 are constructed according to a predefined geometry of an internal cavity of the main body <NUM> (see, e.g., cavity <NUM> of <FIG> and <FIG>). The mandrels M-<NUM>, M-<NUM> can be held in tooling T (shown in dashed lines for illustrative purposes). The tooling T can be operable to change an orientation or position of the mandrels M-<NUM>, M-<NUM> during fabrication.

Referring to <FIG> and <FIG>, a platform insert <NUM> is situated or positioned along the core plies CL of the core <NUM> at step 296B. The platform insert <NUM> can include at least one or more intermediate (or platform) plies or layers <NUM> situated or laid up along the core plies CL of the core <NUM>. One or more fillers <NUM> can be situated or positioned along the core plies CL at step 296C. The platform insert <NUM> including the intermediate layer(s) <NUM> and the fillers <NUM> can include any of the materials and fiber constructions disclosed herein. In examples, the filler <NUM> is made of chopped fibers in a matrix.

Referring to <FIG> and <FIG>, an overwrap <NUM> is formed at step 296D. Step 296D includes laying up or forming one or more overwrap plies OL over an overwrap mandrel OM (shown in dashed lines for illustrative purposes. The overwrap mandrel OM can have a generally cylindrical geometry, for example. The overwrap plies OL can include any of the materials and fiber constructions disclosed herein. In examples, a total of three overwrap plies OL are biaxially braided about or over the overwrap mandrel OM. The overwrap plies OL are formed such that a passageway OP is established (see also <FIG>).

Referring to <FIG> and <FIG>, the overwrap <NUM> and platform insert <NUM> are positioned or situated relative to the core plies CL (<FIG>) of the core <NUM> and mandrels M-<NUM>, M-<NUM> at step 296E. Step 296E can include inserting the core plies CL (<FIG>) and platform insert <NUM> (<FIG>) at least partially into the passageway OP such that the core <NUM>, overwrap <NUM> and platform insert <NUM> cooperate to establish a sealing portion <NUM> and such that at least the core <NUM> and overwrap <NUM> cooperate to establish an engagement portion <NUM>. Step 296E can include moving the overwrap <NUM> in a direction D1 along a length of the mandrels M-<NUM>, M-<NUM>. The sealing and engagement portions <NUM>, <NUM> can be arranged as disclosed by the sealing and engagement portions <NUM>, <NUM> of the seal <NUM> to establish the seal assembly <NUM> including mounting block <NUM>, for example. Steps 296A-296E occur such that an integral preform is established. The overwrap <NUM> of <FIG> including the passageway OP can be shaped to a predefined contour of the component, which can correspond to an outer periphery of the mandrels M-<NUM>, M-<NUM> and core <NUM>, as illustrated in <FIG>. Steps 296A, 296B and 296E can occur such that the core and overwrap plies CL, OL and/or platform insert <NUM> including the intermediate layer(s) <NUM> span between the mate faces <NUM>, as illustrated by <FIG>.

The component is consolidated at step 296F. Step 296F can include embedding the fibers of the seal <NUM> in a matrix material, such as carbon-based fibers in a carbon-based ceramic matrix, including silicon carbide (SiC) fibers in a silicon carbide (SiC) matrix. Step 296F includes removing the mandrels M-<NUM>, M-<NUM> from the main body <NUM> to establish an internal cavity spanning circumferentially between openings along the mate faces <NUM> (see, e.g., the cavity <NUM> of <FIG> and openings <NUM> of <FIG> and <FIG>). Various techniques can be utilized to establish the matrix, including chemical vapor infiltration (CVI) or a melt infiltration (MI) technique. Thereafter, the component is cured in a mold to establish an integral component.

One or more finishing operations can be performed on the component at step <NUM>. Step <NUM> can include machining one or more surfaces of the component. Step <NUM> can include forming one or more features in the component such as an elongated opening or slot (see, e.g., slot <NUM>' of <FIG>).

Although particular step sequences are shown, and described, it should be understood that steps may be performed in any order, separated or combined unless otherwise indicated and will still benefit from the present disclosure.

Claim 1:
A seal assembly (<NUM>) for a gas turbine engine (<NUM>) comprising:
a seal (<NUM>; <NUM>; <NUM>) including a main body (<NUM>; <NUM>) extending circumferentially between opposed mate faces (<NUM>; <NUM>), the main body including a sealing portion (<NUM>; <NUM>) and an engagement portion (<NUM>; <NUM>) extending outwardly from sealing portion along at least one of the mate faces; and
wherein the main body includes:
a core (<NUM>; <NUM>) including one or more core plies having a first fiber construction comprising substantially continuous fibers and arranged to establish an internal cavity (<NUM>);
an overwrap (<NUM>; <NUM>) including one or more overwrap plies having a second fiber construction comprising substantially continuous fibers and arranged to follow a perimeter of the one or more core plies to establish the engagement portion and the sealing portion, and the second fiber construction differing from the first fiber construction; and
a platform insert (<NUM>; <NUM>) extending between portions of the core and the overwrap to establish the sealing portion, and the platform insert having a construction that differs from the first and second fiber construction, characterised in that the platform insert includes at least one intermediate ply situated between portions of the core and the overwrap to establish the sealing portion, and the at least one intermediate ply has a third fiber construction of substantially discontinuous fibers.