Patent Description:
Fans in gas turbine engines are complex rotating systems that may encounter undesirable conditions during normal operation. Fans may be subject to debris entering an engine inlet. The debris may contact the blades of the fan and cause structural damage. As the use of composite materials for fan blades has become more prevalent, so too has the risk of delamination and fiber breakage.

Fan blades are typically designed to have a light weight while maintaining sufficient strength to absorb impacts. Many composite blades are made using a resin transfer molding (RTM) process. The typical RTM process for fan blades uses two-dimensionally woven plies, three-dimensional preforms, or both. These plies and preforms are costly to make and use complex weaving machines. The carbon fibers in the plies and preforms may not be optimally oriented as there is little ability to customize fiber orientation to accommodate loads on a blade. <CIT> discloses a composite core structure having a triaxial braid for an airfoil structure.

A method according to claim <NUM> of making a fan blade is provided.

In various embodiments, the core may be trimmed before the placing the first layer of dry fiber tows over the core. The first layer may be placed over the core in a curved configuration. The core may include a three-dimensionally woven core formed on a loom and/or a plurality of layers of dry fiber tows placed by the robot. The thermoplastic coating may be heated after placing the first layer over the core. The first layer and the second layer may be tufted and or needled together.

A fan blade according to claim <NUM> is also provided.

In various embodiments, the fibrous material of the core may comprise a three-dimensionally woven material and/or a second plurality of layers of dry fiber tows. The plurality of layers of dry fiber tows maybe curved. A tufting may be disposed in the plurality of layers. The plurality of layers may also be needled together.

A fan for a gas turbine engine according to claim <NUM> is also provided.

In various embodiments, the first layer may be curved relative to a surface of the fan blade. The first layer and the second layer may be tufted together and/or needled together.

The subject matter of the present invention is defined by the appended claims. A more complete understanding of the present invention is obtained by referring to the detailed description.

The detailed description of exemplary embodiments herein makes reference to the accompanying drawings, which show exemplary embodiments by way of illustration and their best mode. While these exemplary embodiments are described in sufficient detail to enable those skilled in the art to practice the disclosures, it should be understood that other embodiments may be realized and that logical, chemical, and mechanical changes may be made without departing from the scope of the invention as defined by the claims. For example, the steps recited in any of the method or process descriptions may be executed in any order and are not necessarily limited to the order presented. Also, any reference to attached, fixed, connected or the like may include permanent, removable, temporary, partial, full and/or any other possible attachment option.

The present disclosure relates to composite fan blades made using Automated Fiber Placement (AFP) of dry fiber tows. AFP may use a robot to place the fiber in tows with a thermoplastic material. Heat may be applied to hold the tows in place by increasing tackiness of the thermoplastic. The preform is made by adding numerous layers of the dry fiber tows. Reinforcement through the thickness can also be added via tufting or needling. Tufting and/or needling may insert additional fiber through the layers after layup. Various embodiments may also include a three-dimensional woven core in the middle of the preform with only the outer layers formed by AFP of dry fiber tows. The preform can be highly customized for optimal structure. The tows are held in place in an un-crimped configuration. The robotic placement process allows consistency and repeatability in the manufacturing process. As used herein, dry means substantially free of viscous or adhesive material other than the thermoplastic coating.

Referring now to <FIG>, an exemplary gas turbine engine <NUM> is shown, in accordance with various embodiments. Gas turbine engine <NUM> may be a two-spool turbofan that generally incorporates a fan section <NUM>, a compressor section <NUM>, a combustor section <NUM> and a turbine section <NUM>. Alternative engines may include, for example, an augmentor section among other systems or features. In operation, fan section <NUM> can drive fluid (e.g., air) along a bypass-flow path B while compressor section <NUM> can drive coolant along a core-flow path C for compression and communication into combustor section <NUM> then expansion through turbine section <NUM>. Although depicted as a two-spool turbofan gas turbine engine <NUM> herein, 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 turbojet, turboprop, turboshaft, or power generation turbines, with or without geared fan, geared compressor or three-spool architectures.

Gas turbine engine <NUM> may generally comprise a low speed spool <NUM> and a high speed spool <NUM> mounted for rotation about an engine central longitudinal axis A-A' relative to an engine static structure <NUM> via several bearing systems <NUM>, <NUM>-<NUM>, and <NUM>-<NUM>. It should be understood that various bearing systems <NUM> at various locations may alternatively or additionally be provided, including for example, bearing system <NUM>, bearing system <NUM>-<NUM>, and bearing system <NUM>-<NUM>.

Low speed spool <NUM> may generally comprise an inner shaft <NUM> that interconnects a fan <NUM>, a low-pressure compressor <NUM> and a low-pressure turbine <NUM>. Inner shaft <NUM> may be connected to fan <NUM> through a geared architecture <NUM> that can drive fan <NUM> at a lower speed than low speed spool <NUM>. Fan <NUM> (or other rotating sections having airfoils such as compressor section <NUM> or turbine section <NUM>) may include blades formed from composite materials. Geared architecture <NUM> may comprise a gear assembly enclosed within a gear housing that couples inner shaft <NUM> to a rotating fan structure. High speed spool <NUM> may comprise an outer shaft <NUM> that interconnects a high-pressure compressor <NUM> and high-pressure turbine <NUM>. Airfoils <NUM> coupled to a rotor of high-pressure turbine may rotate about the engine central longitudinal axis A-A' or airfoils <NUM> coupled to a stator may be rotationally fixed about engine central longitudinal axis A-A'.

A combustor <NUM> may be located between high-pressure compressor <NUM> and high-pressure turbine <NUM>. Inner shaft <NUM> and outer shaft <NUM> may be concentric and rotate via bearing systems <NUM> about the engine central longitudinal axis A-A', which is collinear with their longitudinal axes. As used herein, a "high-pressure" compressor or turbine experiences a higher pressure than a corresponding "low-pressure" compressor or turbine.

The core airflow along core-flow path C may be compressed by low-pressure compressor <NUM> then high-pressure compressor <NUM>, mixed and burned with fuel in combustor <NUM>, then expanded over high-pressure turbine <NUM> and low-pressure turbine <NUM>. Turbines <NUM>, <NUM> rotationally drive the respective low speed spool <NUM> and high speed spool <NUM> in response to the expansion.

Referring now to <FIG>, a fan <NUM> is shown according to various embodiments. Fan <NUM> may include a shroud <NUM> having an annular geometry. Blades <NUM> may rotate about hub <NUM> within shroud <NUM>. Impact events may occur when debris enters shroud <NUM> and contacts blades <NUM>. Blades <NUM> made from AFP of dry fiber tows may be resistant to delamination in response to impact events while maintaining light weight. Blades <NUM> may be made either with or without a woven core. The core is made of fibrous material such as AFP of dry fiber tows and/or woven fibers.

Referring to <FIG>, an exemplary cross section of a blade <NUM> made using a core <NUM> and a skin <NUM> made using AFP of dry fiber tows is shown according to various embodiments. Core <NUM> may be a three-dimensionally woven core made using a loom to weave fibers into a predetermined shape. A three-dimensionally woven core may be a woven structure containing a set of fibrous yarn or tows lying in <NUM> orthogonal directions (e.g., an x-axis, y-axis, and z-axis). The woven structure may affect the physical properties in three planar directions as compared to two-dimensional woven composite form with yarns lying in only two orthogonal directions (e.g., an x-axis and a y-axis).

In various embodiments, core <NUM> may be trimmed to leave fibers in a predetermined shape. Skin <NUM> may be formed about core <NUM>. Skin <NUM> is made using AFP (as show in <FIG> and <FIG>) to place dry fiber tows directly on core <NUM>. The dry fiber tows include a thermoplastic coating to hold the fibers in place during the AFP process. A preform comprising core <NUM> and skin <NUM> is molded using resin transfer molding (RTM). Generally, RTM includes a process where a molding material having a first material composition (e.g., a resin, a thermosetting material, a thermoplastic material, or the like) is heated and injected into a mold encasing at least a portion of the skin <NUM> and core <NUM>. The molding material infiltrates and/or encases the skin <NUM> and core <NUM> and is subsequently cured. Core <NUM> and skin <NUM> may be injected with a resin material, such as the resin material commercially available under the tradename Hexcel RTM-<NUM> for example, that lacks thermoplastic additives in response to the skin <NUM> and/or core <NUM> comprising dry fiber tows having a thermoplastic coating.

Referring to <FIG>, an exemplary cross section of a blade <NUM> made using AFP of dry fiber tows <NUM> without a three-dimensionally woven core is shown according to various embodiments. Layers of dry fiber tows <NUM> are built up using an AFP process. Outer surface <NUM> may also be defined by dry fiber tows placed using AFP. In an embodiment that is not claimed, the dry fiber tow <NUM> may be treated injected with a molding material using RTM, as described above with reference to <FIG>.

Referring to <FIG>, a diagram illustrating the placement of internal fiber tows <NUM> about core <NUM> is shown according to various embodiments. Internal fiber tows <NUM>, which are similar to skin <NUM> of <FIG> and outer surface <NUM> of <FIG>, are placed in a predetermined orientation on core <NUM>. Multiple layers of internal fiber tows <NUM> may be built by placement on core <NUM>. Core <NUM> may include a three-dimensionally woven core. Core <NUM> may also comprise many layers of internal fiber tows <NUM> built by placement one on top of another. External fiber tows <NUM> may be placed as the outermost layer on either side of core <NUM>. The skin (e.g., skin <NUM> of <FIG>) may include one or more layers of dry fiber tows placed using AFP. For example, the skin may include four layers of dry fiber tows placed on either side of core <NUM>.

Referring briefly to <FIG>, robot <NUM> is programmed to deposit the tows at various predetermined angles and orientations. Robot <NUM> may include head <NUM> that places dry fiber tow <NUM> in position on lower layer <NUM> of fiber material. Upper layer <NUM> of fiber material may comprise a multiple dry fiber tows placed by head <NUM> on lower layer <NUM> as robot translates head <NUM>. Heating device <NUM> may heat the dry fiber tow <NUM> to make a thermoplastic coating on dry fiber tow <NUM> more tacky and retain the layers of fiber material relative to one another.

Referring to <FIG>, internal fiber tows <NUM> may be placed by a robot operating similar to robot <NUM> of <FIG>. The robot may place the internal fiber tows <NUM> and/or external fiber tows <NUM> with the fiber tows oriented in various directions to augment the strength of a finished blade. For example, fiber tows may point in a first direction at a blade root area and curve to a second direction at a blade tip area. The direction of the fiber tows may be predetermined using computer modeling to identify orientations that strengthen the blade. The fiber tows are also placed using AFP in un-crimped manner. In an embodiment that is not claimed, fiber tows <NUM> may also be placed using AFP on a separate tool and then attached to core <NUM>.

In various embodiments, the various layers of internal fiber tows <NUM>, external fiber tows <NUM>, and/or core <NUM> may be laid on a support and needled or tufted together simultaneously or in a series of needling steps. Tufting and/or needling processes may interconnect the horizontal fibers in a third direction (also called the z-direction). The fibers extending into the third direction may be referred to as z-fibers. The needling process may involve driving a multitude of barbed needles into the fibrous layers to displace a portion of the horizontal fibers into the z-direction. Similarly, tufting may involve sewing tufting <NUM> into the various layers to retain the internal fiber tows <NUM>, external fiber tows <NUM>, and/or core <NUM> relative to one another. Tufting <NUM> may extend partially into core <NUM> and/or completely through core <NUM>. Tufting may be done on both sides of the core <NUM>. Resin material <NUM> may infiltrate the fiber tows and/or core in response to an RTM process.

Referring now to <FIG>, a method <NUM> for making a fan blade (e.g., blade <NUM> of <FIG>) is shown, in accordance with the claimed invention. A core is formed comprising fibrous material (Step <NUM>). A first layer of dry fiber tows is placed over the core using a robot (Step <NUM>). The first layer of the dry fiber tows is substantially un-crimped. The first layer of the dry fiber tows includes a thermoplastic coating. A second layer of the dry fiber tows is placed over the first layer of the dry fiber tows using the robot (Step <NUM>). The second layer is similar to the first layer in characteristics. The core, the first layer of the dry fiber tow, and the second layer of the dry fiber tows are molded using resin transfer molding (Step <NUM>).

However, the benefits, advantages, solutions to problems, and any elements that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as critical, required, or essential features or elements of the disclosures.

The scope of the disclosures is accordingly to be limited by nothing other than the appended claims, in which reference to an element in the singular is not intended to mean "one and only one" unless explicitly so stated, but rather "one or more.

Claim 1:
A method of making a fan blade, comprising:
forming a core (<NUM>) comprising fibrous material (step <NUM>);
placing a first layer of dry fiber tows (<NUM>) over the core using a robot (<NUM>) (step <NUM>), wherein the first layer of dry fiber tows is substantially un-crimped, wherein the first layer of dry fiber tows includes a thermoplastic coating;
placing a second layer of dry fiber tows over the first layer of dry fiber tows (step <NUM>), wherein the second layer of dry fiber tows is substantially un-crimped, wherein the second layer of dry fiber tows includes a thermoplastic coating; and
molding the core, the first layer of dry fiber tows, and the second layer of dry fiber tows using resin transfer molding (step <NUM>),
wherein the first layer of dry fiber tows and the second layer of dry fiber tows are deposited at various predetermined angles and orientations with the robot (<NUM>), and wherein the thermoplastic coating is configured to increase the relative retention between each of the first layer of dry fiber tows and the second layer of dry fiber tows in response to heating.