Patent Description:
An example of such a platform is described in <CIT> in which a platform for a gas turbine engine includes a platform body that has a gas path surface extending axially between a leading edge and a trailing edge. The gas path surface also extends circumferentially between opposed mate faces. A plurality of platform flanges extend from the platform body to define one or more slots. The slots are dimensioned to receive a respective flange of a rotatable hub, and each platform flange has a retention member dimensioned to receive a retention pin to mount the platform body. The platform body includes a composite wrap extending about a perimeter of the platform body to define an internal cavity. At least one honeycomb core has a plurality of cells that is disposed in the internal cavity.

<CIT> describes platforms which include a flow structure having a gaspath surface and a non-gaspath surface with a front end, a rear end, a first edge, and a second edge. A platform connector extends from the flow structure. A first layer forms a part of the gaspath surface and is a non-continuous layer terminating at the ends and the edges. A second layer forms a part of the platform connector and is a non-continuous layer terminating at the ends and the edges. The second layer contacts the first layer proximate the first and second edges. A third layer defines an internal void and is a continuous layer arranged between the first layer and the second layer and defines a part of the flow structure and a part of the platform connector.

<CIT> describes an annulus filler which may include an outer lid which defines an airflow surface for air being drawn through the engine in an axial airflow direction, and a support structure configured to connect the outer lid to a rotor disc. The annulus filler includes at least one composite material which includes one or both of a plurality of relatively high-modulus reinforcement elements, a plurality of relatively tough polymer-based reinforcement elements, and a matrix material for substantially encapsulating those elements.

In a first aspect of the present invention, there is provided a fan platform comprising a platform body that has gaspath and non-gaspath sides, leading and trailing ends, first and second circumferential sides that are contoured to follow profiles of adjacent fan blades, and lugs projecting from the non-gaspath side that define fastener openings. The platform body includes a core and a fiber-reinforced polymer matrix composite skin attached on the core at least on portions of the gaspath and non-gaspath sides, the core is formed of a material selected from the group consisting of honeycomb, foam, and combinations thereof, an environmental barrier layer disposed on at least a portion of the core that does not have the skin, and wherein the environmental barrier layer (<NUM>) is an elastomer material.

In an embodiment of the above embodiment, the skin is also attached on the lugs.

In an embodiment of any of the above embodiments, the core includes lug stubs, and there are lug pieces adhesively bonded to the lug stubs. The lug pieces contain the fastener openings.

In an embodiment of any of the above embodiments, the lug pieces are selected from the group consisting of polymer blocks, metal blocks, and combinations thereof.

In an embodiment of any of the above embodiments, the core is formed of a closed-cell foam.

In an embodiment of any of the above embodiments, the core is bare and exposed on at least a portion of the leading end, the trailing end, the first circumferential side, or the second circumferential side.

In an embodiment of any of the above embodiments, the environmental barrier layer is an elastomer material.

In an embodiment of any of the above embodiments, the environmental barrier layer includes a fluoropolymer.

In an embodiment of any of the above embodiments, the fastener openings are axially aligned.

In an embodiment of any of the above embodiments, the core thickens from the leading end to the trailing end.

In an embodiment of any of the above embodiments, the platform body further includes an adhesive between the skin and the core.

In an embodiment of any of the above embodiments, the core includes lug stubs, and there are lug pieces adhesively bonded to the lug stubs. The lug pieces contain the fastener openings. The core is formed of a material selected from the group consisting of honeycomb, foam, and combinations thereof, and the lug pieces are selected from the group consisting of polymer blocks, metal blocks, and combinations thereof.

In a second aspect of the present invention, the fan platform is included in a fan of a gas turbine engine that also includes a compressor section, a combustor, and a turbine section.

In an embodiment of the above embodiment, the core has lug stubs, and there are lug pieces adhesively bonded to the lug stubs. The lug pieces contain the fastener openings. The core is formed of a material selected from the group consisting of honeycomb, foam, and combinations thereof, and the lug pieces are selected from the group consisting of polymer blocks, metal blocks, and combinations thereof.

In a third aspect of the present invention, there is provided a method of fabricating a fan platform comprising forming a platform body that has gaspath and non-gaspath sides, leading and trailing ends, first and second circumferential sides that are contoured to follow profiles of adjacent fan blades, and lugs that project from the non-gaspath side and define fastener openings. The forming includes arranging one or more layers of a fiber-reinforced polymer matrix composite skin on a core at least on portions of the gaspath and non-gaspath sides, wherein the core is formed of a material selected from the group consisting of honeycomb, foam, and combinations thereof, and an environmental barrier layer disposed on at least a portion of the core that does not have the skin, and wherein the environmental barrier layer is an elastomer material.

An embodiment of the above embodiment the method further comprises, prior to the arranging, adhesively bonding lug pieces to lug stubs on the core. The lug pieces contain the fastener openings.

In an embodiment of any of the above embodiments the method further comprises applying an environmental barrier layer on at least a portion of the core that does not have the skin. The environmental barrier layer is selected from the group consisting of a glass fiber-reinforced material, fluoropolymer, and combinations thereof.

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

Although depicted as a two-spool turbofan gas turbine engine in the disclosed non-limiting embodiment, it should be understood that the concepts described herein are not limited to use with two-spool turbofans as the teachings may be applied to other types of turbine engines including but not limited to three-spool architectures.

The low pressure turbine <NUM> pressure ratio is pressure measured prior to the inlet of low pressure turbine <NUM> as related to the pressure at the outlet of the low pressure turbine <NUM> prior to an exhaust nozzle.

The example gas turbine engine <NUM> includes the fan section <NUM> that comprises in one non-limiting embodiment less than about <NUM> fan blades <NUM>. In another non-limiting embodiment, the fan section <NUM> includes less than about <NUM> fan blades <NUM>. Moreover, in one disclosed embodiment the low pressure turbine <NUM> includes no more than about <NUM> turbine rotors. In another disclosed embodiment, the low pressure turbine includes about <NUM> rotors. In another non-limiting example embodiment, the low pressure turbine <NUM> includes about <NUM> turbine rotors. In yet another disclosed embodiment, the number of turbine rotors for the low pressure turbine <NUM> may be between <NUM> and <NUM>. A ratio between the number of fan blades <NUM> and the number of low pressure turbine rotors is between about <NUM> and about <NUM>. The example low pressure turbine <NUM> provides the driving power to rotate the fan section <NUM> and therefore the relationship between the number of turbine rotors <NUM> in the low pressure turbine <NUM> and the number of blades <NUM> in the fan section <NUM> disclose an example gas turbine engine <NUM> with increased power transfer efficiency.

Selected portions of the fan section <NUM> are shown in <FIG>. The fan blades <NUM> (two shown) are attached to a fan hub <NUM>. For example, each fan blade <NUM> has a root 42a that is received axially into a corresponding slot 60a in the rim of the hub <NUM>. The slot 60a radially secures the blade <NUM>. In one embodiment, the roots 42a are a dovetails and the slots 60a are doveslots.

Between each adjacent pair of blades <NUM> there is a fan platform <NUM>, which is also shown in an elevation view in <FIG> and a sectional view in <FIG>. The fan platform <NUM> serves to provide an inner diameter boundary for air coming into the fan blades <NUM>.

<FIG> illustrate isolated views of the fan platform <NUM>. The fan platform <NUM> generally includes a platform body <NUM> that defines a gaspath side 66a, a non-gaspath side 66b, a leading end 66c, a trailing end 66d, a first circumferential side 66e, and a second circumferential side 66f. The gaspath side 66a generally faces radially outwards away from the slots 60a in the hub <NUM>, while the non-gaspath side 66b faces radially inwards towards the slots 60a. The leading end 66c faces toward the front of the engine <NUM> and the trailing end 66d faces toward the rear of the engine <NUM>. The circumferential sides 66e/66f are contoured to follow the aerodynamic profiles of the adjacent fan blades <NUM>. For example, the circumferential sides 66e/66f may abut the blades <NUM> or interface with seals that abut the blades <NUM>.

The platform body <NUM> includes lugs 68a/68b/68c/68d that project from the non-gaspath side 66b. The lugs 68a/68b/68c/68d each define a respective fastener opening <NUM>. For example, the openings <NUM> are coaxial such that a fastener <NUM> (<FIG>) can be received there through. The fastener <NUM> is also received through corresponding openings <NUM> in the rim of the hub <NUM> to secure the fan platform <NUM> to hub <NUM>. Optionally, one or more bushings <NUM> can be used with the fastener <NUM> to facilitate mounting.

The platform body <NUM> is formed of several distinct sections. As best shown in <FIG>, the platform body <NUM> includes a core <NUM> and a fiber-reinforced polymer matrix composite skin <NUM> attached on the core <NUM> at least on portions of the gaspath side 66a and non-gaspath side 66b. As an example, the skin <NUM> is adhesively attached by an adhesive layer <NUM>, such as an epoxy adhesive. The core <NUM> is relatively lightweight and provides a substrate for the skin <NUM>, which is conformal with the core <NUM>. As an example, the core <NUM> may be formed of a honeycomb or a foam. One example foam is a closed-cell polymer foam. In the illustrated example, the core <NUM> thickens in the radial dimension from the leading end 66c to the trailing end 66d (e.g., tapers from the trailing end 66d to the leading end 66c). Such a geometry may be used to facilitate meeting space requirements and also enhance bending stiffness.

The skin <NUM> is generally strong and durable. For example, the skin is formed of a high strength fibers, such as carbon fibers, glass fibers, or aramid fibers, disposed in a polymer matrix, such as an epoxy matrix. In one embodiment, the fibers are provided as a woven fabric. In another embodiment, the fibers are unidirectional. In additional embodiments, the skin <NUM> may be formed of multiple fiber layers, including multiple woven layers, multiple unidirectional layers that alternate in fiber direction, or multiple woven and unidirectional layers.

Although the core <NUM> and skin <NUM> may have considerable strength, there may be elevated stresses at the lugs 68a/68b/68c/68d. In this regard, the lugs 68a/68b/68c/68d are formed, at least in part, by lug pieces <NUM> that are composed of a different, stronger material than at least the core <NUM>. For example, the lug pieces <NUM> are formed of blocks of a polymer material or metal which includes the openings <NUM>. In one embodiment, the polymer material is a reinforced polymer matrix composite. For example, the reinforced polymer matrix composite is a laminate formed of multiple fiber layers, such as woven and/or unidirectional fiber layers, disposed in a polymer matrix. In one further example, the fibers of the fiber layers are high strength fibers, such as carbon fibers, and the polymer matrix is epoxy. In one alternative example, the reinforced polymer matrix composite is a discontinuous fiber composite that includes short fibers disposed in a polymer matrix. In one example of a metal block, the metal is aluminum or steel.

The core <NUM> includes lug stubs 76a at which the respective lug pieces <NUM> are attached. The lug stubs 76a are relatively short projections that have an interface surface for receiving the lug pieces <NUM>. For instance, the interface surfaces are flat surfaces that receive and interface with corresponding flat surfaces on the lug pieces <NUM>. In one example, the lug pieces <NUM> are adhesively bonded by an adhesive layer <NUM> to the lug stubs 76a.

As shown in <FIG>, the skin <NUM> does not completely cover the core <NUM>. In this example, the skin <NUM> completely covers the gaspath side 66a and portions of the non-gaspath side 66b but does not cover portions of the lugs 68a/68b/68c/68d, the side of the leading end 66d, the side of the trailing end 66c, or the circumferential sides 66e/66f. These portions of the core <NUM> are thus bare and exposed. If erosion, infiltration of air and/or foreign debris, or other environmental factors are not of concern, those portions may be left bare in the final fan platform <NUM>, which is not part of the present invention.

Referring to a modified example of the fan platform <NUM> in <FIG>, if greater resistance to environmental factors is desired, the fan platform <NUM> is provided with an environmental barrier layer <NUM> on those portions that were bare in the prior example, i.e., the portions of the lugs 68a/68b/68c/68d, the side of the leading end 66d, the side of the trailing end 66c, and the circumferential sides 66e/66f. In another example belonging to the invention, the skin <NUM> and the environmental barrier layer <NUM> completely encase the core <NUM> such that no exterior portion of the core <NUM> is bare. Even if additional environmental resistance is not desired, the layer <NUM> may be utilized to strengthen or stiffen the fan platform <NUM>.

According to the invention, the environmental barrier layer <NUM> is an elastomer material. another example, the environmental barrier layer <NUM> includes a fluoropolymer. As an example, the environmental barrier layer <NUM> is a continuous layer of the fluoropolymer. In one embodiment, the fluoropolymer is VITON.

<FIG> depicts a method of fabricating the fan platform <NUM>. The method generally includes forming the platform body <NUM> by arranging one or more layers of the fiber-reinforced polymer matrix composite skin <NUM> on the core <NUM> at least on portions of the gaspath and non-gaspath sides 66a/66b. For instance, as shown, the core <NUM> is initially provided without any skin <NUM> or lug pieces <NUM> attached. In one embodiment, the core <NUM> is provided as a pre-fabricated piece in a desired geometry. In an alternate example, the core <NUM> is formed to the desired geometry from a starting or blank shape. For instance, the core <NUM> is machined or cut from an initial piece of stock foam or honeycomb.

Thereafter, the lug pieces <NUM> are attached to the lug stubs 76a by applying the adhesive <NUM> to the lug stubs 76a, the lug pieces <NUM>, or both and then moving the lug pieces <NUM> onto the lug stubs 76a. Once the adhesive dries or cures, at least enough to permit handling without inadvertent dislodging, the lug pieces <NUM> are secured to the core <NUM>.

After securing the lug pieces <NUM> to the core <NUM>, one or more layers of the skin <NUM> are applied to the core <NUM>. For instance, if the layers are fiber layers that are preimpregnated with matrix material, the layers may be tacky and adhere to the core <NUM> to permit application without the addition of the adhesive <NUM>. If the layers are not tacky or are not tacky enough to adhere, the adhesive <NUM> is applied to the layer, the core <NUM>, or both. For instance, the fiber layers are dry fiber layers that do not contain any of the matrix material. In this regard, the matrix material may be introduced in a later step, such as by resin transfer, compression molding, or the like. If the matrix material is introduced in this manner, use of a closed-cell foam for the core <NUM> prevents the resin from infiltrating from the fiber layer into the core <NUM>, which could otherwise leave voids in the skin <NUM>. Once the fibers and matrix material are in place on the core <NUM>, a curing step may be conducted to cure the matrix material. For example, the curing step involves a thermal curing in which heat is applied above a curing temperature of the matrix material for a period of time until the matrix material is substantially or fully cured.

After curing, as shown in <FIG>, the fan platform <NUM> may still require additional processing steps to achieve a final desired geometry. For instance, the skin <NUM> may be trimmed or smoothed and/or the lugs 68a/68b/68c/68d may be machined. In the example shown, the lugs 68a/68b/68c/68d initially have a rectangular geometry but are machined to achieve the rounded geometry shown in <FIG>, which may also serve to reduce weight. According to the invention, the environmental barrier layer <NUM> is then applied at least to the bare regions of the core <NUM>, including those portions exposed by machining. If required, the environmental barrier layer <NUM> is cured, such as in a thermal curing process. The environmental barrier layer <NUM> may thereafter be trimmed, smoothed, or machined as appropriate to achieve a final desired geometry.

The use of the core <NUM> and skin <NUM> also permits the fabrication process to be readily adapted for different designs. For instance, it may be desirable that the contour of the aerodynamic gaspath side 66a of the fan platform <NUM> not be varied from one design to another. Yet, the geometry of the hub <NUM> may differ between the two designs such that there is more or less design space for the lugs. In this regard, the lugs can be readily redesigned in location and size to accommodate the space available. The fabrication process, however, can remain generally the same between the two designs, as the core <NUM> and lug pieces <NUM> are just provided or formed according to the different designs. In contrast, for a platform that is cast or molded, entirely new tooling may be required for the different designs.

In other words, a system designed according to an embodiment of this disclosure will not necessarily include all of the features shown in any one of the.

Figures or all of the portions schematically shown in the Figures.

The preceding description is exemplary rather than limiting in nature. Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not necessarily depart from the invention.

Claim 1:
A fan platform (<NUM>) comprising:
a platform body (<NUM>) having
gaspath and non-gaspath sides (66a, 66b),
leading and trailing ends (66c, 66d),
first and second circumferential sides (66e, 66f) that are contoured to follow profiles of adjacent fan blades (<NUM>), and
lugs (68a, 68b, 68c, 68d) projecting from the non-gaspath side (66b) and defining fastener openings (<NUM>),
wherein the platform body (<NUM>) comprises a core (<NUM>), wherein the core (<NUM>) is formed of a material selected from the group consisting of honeycomb, foam, and combinations thereof. characterised in that a fiber-reinforced polymer matrix composite skin (<NUM>) attached on the core (<NUM>) at least on portions of the gaspath and non-gaspath sides (66a, 66b),
an environmental barrier layer (<NUM>) disposed on at least a portion of the core (<NUM>) that does not have the skin (<NUM>), and
wherein the environmental barrier layer (<NUM>) is an elastomer material.