Internal attachment part for a hybrid blade root

Abstract

The present invention relates to a blade comprising: - a structure made of composite material comprising a blade-root portion that comprises a cavity; - an external attachment part; and - an internal attachment part arranged inside the cavity; wherein the internal attachment part comprises a head comprising a contour line defining a base and an upper edge; the upper edge extending between a first intersection and a second intersection with the contour line, the first intersection and the second intersection separating the contour line into a first portion and a second portion; the first portion defining, with the upper edge, a first lateral surface and the second portion defining, with the upper edge, a second lateral surface; and the first lateral surface and the second lateral surface each comprising a concave curvature region.

Description

[0001] DESCRIPTION

[0002] TITLE: INTERNAL ATTACHMENT FOR HYBRID BLADE FOOT

[0003] FIELD OF INVENTION

[0004] The present presentation concerns a variable pitch blade comprising a composite material structure and a blade foot attachment.

[0005] The present presentation relates more particularly, but not exclusively, to a variable pitch blade intended for use in a blower rotor of a propulsion system, such as a gas turbine engine.

[0006] STATE OF THE ART

[0007] The search for minimizing polluting emissions related to air transport involves, in particular, improving all the efficiencies of propulsion systems, and more specifically the propulsive efficiency which characterizes the efficiency with which the energy communicated to the air passing through the propulsion system is converted into useful thrust effort, as well as reducing fuel consumption.

[0008] The advantage of unfaired fan engines is that the diameter of the fan is not limited by the presence of a fairing, so it is possible to design an engine with a high bypass ratio or BPR (ByPass Ratio in Anglo-Saxon terminology), and therefore reduced fuel consumption.

[0009] Thus, in this type of engine, the fan blades can have a large span.

[0010] In addition, these engines generally include a mechanism to change the angle of the blades in order to adapt the thrust generated by the fan according to the different phases of flight.

[0011] However, the design of such blades requires taking into account conflicting constraints.

[0012] On the one hand, the sizing of these blades must allow optimal aerodynamic performance (maximizing propulsive efficiency and providing thrust while minimizing losses) and therefore requires an increase in the external diameter, and thus in the span of the blades.

[0013] On the other hand, it is also necessary to ensure resistance to the mechanical stresses that may be exerted on these blades while limiting their acoustic signature. These blades can be made of metallic material. While metallic blades offer good mechanical resistance, they have the disadvantage of being relatively heavy.

[0014] Manufacturing blades from composite materials is an attractive solution for reducing blade weight. However, composite blades can be fragile due to the intense aerodynamic stresses they are subjected to. These aerodynamic stresses can therefore damage the blades and / or the hub in the interface area between the blades and the fan rotor hub, at the blade root.

[0015] A metal attachment to the blade root could help limit damage to the blade and / or hub in the interface area. However, the material difference between the metal attachment and the composite portion of the blade can lead to delamination or cracking in the composite material. Delamination is a crack or separation in the composite material. These delaminations can occur primarily at the interface between the composite material and the metal. This is because the composite material and the metal do not have the same coefficient of thermal expansion, resulting in differential expansion between the blade root attachment and the composite blade root.

[0016] DESCRIPTION OF THE INVENTION

[0017] One aim of this presentation is to propose a blade including a composite material, adapted to be used with a variable shimming mechanism without the thermal expansion of the composite material creating decohesion or cracking in the composite material due to the variable shimming mechanism.

[0018] For this purpose, according to one aspect of this presentation, a blade is proposed comprising: a composite material structure including a fibrous reinforcement obtained by three-dimensional weaving and a matrix in which the fibrous reinforcement is embedded; the fibrous reinforcement comprising warp strands extending longitudinally from the blade and weft strands extending transversely from the blade, perpendicular to the longitudinal direction; the composite material structure comprising a portion of the blade with an aerodynamic profile and a portion of the blade root; the portion of the blade root comprising a housing extending longitudinally in a debonding of the fibrous reinforcement obtained during the three-dimensional weaving of the fibrous reinforcement; the housing comprising an opening to the outside of the portion of the blade root; an external attachment piece comprising a wall delimiting a cavity and an opening formed in the wall.the composite material structure extending through the opening such that the blade portion is located outside the external attachment piece and the blade root portion is located inside the cavity, and an internal attachment piece disposed in the cavity and inside the housing such that the internal attachment piece locks the blade root portion against the wall of the external attachment piece; wherein the internal attachment piece comprises a main body extending in the longitudinal direction and a head extending from the main body; the head comprising a contour line, delimiting a base, and a top edge; the top edge extending from a first intersection with the contour line to a second intersection with the contour line, distinct from the first intersection,the first intersection and the second intersection separating the contour line into a first portion of contour line and a second portion of contour line, the first portion delimiting with the upper edge a first lateral surface of the head and the second portion delimiting with the upper edge a second lateral surface of the head, and the lateral surfaces extending respectively on either side of the upper edge, and the first lateral surface and the second lateral surface each comprising a concave curvature zone.

[0019] Advantageously, but optionally:

[0020] - the first lateral surface and the second lateral surface are separated by the upper edge and each includes, from the contour line to the upper edge, a convex curvature zone and then the concave curvature zone;

[0021] - the main body has a cylindrical shape of revolution having an axis of revolution parallel to the longitudinal direction, and includes a first end and a second end, and the second end of the main body and the contour line of the head having an elliptical circular section, ;

[0022] - the main body is metallic;

[0023] - the head is made of a material: whose Young's modulus is less than 500 MPa, to accommodate expansion of the composite material structure, which resists a pressure of at least 7 bars, and which withstands temperatures of at least 120°C; - the head is made of a composite material comprising an organic matrix and short fibers embedded in the organic matrix, the organic matrix preferably being made of a thermosetting material, or polyurethane;

[0024] - the head and the main body are two separate pieces, the head being fixed to the second end of the main body;

[0025] - the second end includes an oblong lug and the head includes a mortise to receive the lug, the lug and the mortise being configured to cooperate and orient the head relative to the main body;

[0026] - the first end includes an alignment marker to indicate the angular orientation of the internal fastener piece relative to the composite material structure once the internal fastener piece has been positioned in the housing.

[0027] According to another aspect of this presentation, a gas turbine engine is proposed comprising a blower, the blower comprising a hub and blades extending radially from the hub, each of the blades as previously described.

[0028] Advantageously, but optionally, each blade is mounted to rotate relative to the hub around a respective staking axis, the motor further comprising an actuation mechanism suitable for being controlled to rotate the blades around their staking axes so as to modify a staking angle of the blades.

[0029] DESCRIPTION OF THE FIGURES

[0030] Other features, purposes, and advantages will become apparent from the following description, which is purely illustrative and not exhaustive, and should be read in conjunction with the attached drawings on which:

[0031] Figure 1 represents a schematic perspective view of a gas turbine engine according to one embodiment of the present exposition.

[0032] Figure 2 represents a schematic view of a blade according to one embodiment of the present exposition.

[0033] Figure 3 represents a schematic view of a composite material structure of a blade according to one embodiment of the present presentation.

[0034] Figure 4a and Figure 4b represent a schematic view of an external attachment piece and an internal attachment piece of a blade according to an embodiment of the present exposition.

[0035] Figures 5a and 5b show cross-sectional views of an internal attachment part of a blade according to an embodiment of this presentation. Figure 6 illustrates a top view of the head of an internal attachment part according to an embodiment of this presentation.

[0036] Figure 7 illustrates a flowchart of the steps in a blade assembly process according to a particular implementation of the present presentation.

[0037] Across all figures, similar elements bear identical references.

[0038] DETAILED DESCRIPTION OF THE INVENTION

[0039] Aircraft

[0040] An aircraft is a device configured to rise and move through the air, and can be, for example, a civil or military airplane, or even a helicopter. An aircraft comprises a fuselage which, in the case of an airplane, consists of a fuselage, wings, tail assembly, control surfaces, and landing gear. Propulsion system

[0041] In the example shown in Figure 1, the propulsion system depicted is an unfaired gas turbine engine 1. The propulsion system is configured to be mounted on the aircraft's airframe, for example, under its wings in the case of an airplane, via a pylon (or mast). The propulsion device can also be mounted on the aircraft's wing or at the rear of its fuselage, or even integrated into the fuselage itself.

[0042] Alternatively, the propulsion system may be a twin-spool, twin-flow, direct-drive ducted turbojet, but may also have a different number of bodies and / or flows, and / or be another type of turbojet, such as a geared turbojet or turboprop, with or without afterburner.

[0043] The engine 1 illustrated in Figure 1 comprises, from upstream to downstream, a blower 2 and a primary body 3, often called the "gas generator". The primary body 3 includes a combustion chamber and a turbine section.

[0044] During operation, an airflow F entering the propulsion system is divided into a primary airflow and a secondary airflow, which flow from upstream to downstream within the propulsion system. The secondary airflow, also called the "bypass airflow," flows around the primary body 3. The secondary airflow cools the periphery of the primary body 3 and is used to generate most of the thrust provided by the engine 1.

[0045] The fan 2 can be enclosed or unenclosed (or "open rotor" in Anglo-Saxon terminology). In an unenclosed configuration, the fan 2 can comprise a rotor 21 and a stator 22 (or "USF" for "Unducted Single Fan" in English terminology) or two counter-rotating rotors 21 (or "CROR" for "Contra-Rotating Open Rotor" in English terminology, or "UDF" for "Unducted Double Fan" in French terminology). In other words, when the engine 1 is running, the two rotors 21 are driven in rotation relative to the nacelle around the same axis of rotation (which coincides with a main axis of the engine), in opposite directions.

[0046] In an unfaired blower 2, the blower can be in a configuration commonly referred to as "pusher" (i.e. the blower is placed at the rear of the power generator with an air inlet located on the side) or in a "puller" configuration (i.e. the blower is placed upstream of the gas generator with an air inlet located in front of, between or just behind the blower rotor(s)) as illustrated in the example in Figure 1.

[0047] As illustrated in Figure 1, each rotor 21 comprises a hub 23 and blades 4 extending radially from the hub 23. The blades 4 of each rotor 21 may be fixed relative to the hub 23 or have variable pitch. In the latter case, the root of each blade 4 of the rotor 21 is pivotally mounted about a pitch axis and is connected to a pitch-changing mechanism mounted in the propulsion system, the pitch being adjusted according to the flight phases by the pitch-changing mechanism. The variable pitch induces particular stresses on the blade root 4, which are addressed below. The fan rotor 21 also comprises at least ten blades 4, preferably twelve blades 4, and at most eighteen blades 4.

[0048] The stator 22, or stator, comprises blades 4 mounted on a hub 23 and its function is to straighten the secondary airflow exiting the rotor 21. The stator blades 4 may be fixed relative to the hub 23 or have variable pitch. If so, and similarly to the rotor blades 4 of the rotor 21, the base of the stator blades 4 of the stator 22 is pivotally mounted about a pitch axis and is connected to a pitch-changing mechanism, which is generally separate from that of the rotor 21. The pitch is adjusted according to the flight phases by the pitch-changing mechanism. The number of blades 4 in the stator 22 depends on the acoustic criteria defined for the propulsion system and is at least equal to the number of blades 4 in the rotor 21.

[0049] Dawn

[0050] As illustrated in Figures 2 and 3, each blade 4 comprises a composite material structure 5 extending along a longitudinal direction X of the blade 4 and a blade foot attachment 6 for fixing the blade 4 to the hub 23. The composite material structure 5 extends from a lower end 53 to an upper end 54 of the blade 4. The composite material structure 5 comprises a blade portion 51 with an aerodynamic profile and a blade foot portion 52.

[0051] The blade foot portion 52 extends between the lower end 53 and the blade portion 51. The blade foot portion 52 is intended to allow the attachment of the composite material structure 5 to the blade foot attachment 6.

[0052] The aerodynamically shaped blade section 51 is designed to be placed in an airflow, when engine 1 is running, in order to generate lift. The blade section 51 can have an aerodynamic profile in all three spatial directions.

[0053] The blade part 51 and the blade root part 52 are formed by the same composite material structure 5. The blade 4 can thus withstand significant aerodynamic forces while having a limited mass.

[0054] The composite material structure 5 includes a fibrous reinforcement 55, which is obtained by three-dimensional weaving, and a matrix in which the fibrous reinforcement 55 is embedded during the blade manufacturing process. Weaving and embedding the fibrous reinforcement 55 give the blade portion 51 its aerodynamic profile. The fibrous reinforcement 55 comprises warp strands 551 extending longitudinally within the blade 4 (i.e., from the lower end 53 to the upper end 54) and weft strands 552 extending transversely within the blade 4, i.e., along a transverse direction Y, substantially perpendicular to the longitudinal direction X. The warp strands extend from the lower end 53 to the upper end 54 to allow the transfer of mechanical loads between the blade portion 51 and the blade root portion 52.

[0055] The warp strands 551 and weft strands 552 are made of carbon, glass, aramid, polypropylene, and / or ceramic. The matrix typically comprises an organic material (thermoset, thermoplastic, or elastomer) or a carbon matrix. For example, the matrix may comprise a plastic material, typically a polymer, such as epoxy, bismaleimide, or polyimide.

[0056] The blade foot portion 52 includes a housing 521 extending into the blade foot portion 52 along the longitudinal direction X. The housing 521 is formed by unbinding the fibrous reinforcement 55. This unbinding occurs during the three-dimensional weaving of the fibrous reinforcement 55. The unbinding results from the absence of exchange of weft strands 552 between two distinct layers of warp strands 551 located on either side of and delimiting the unbinding. The housing 521 includes an opening 522 at the lower end 53 of the blade 4, that is, towards the outside of the blade foot portion 52.

[0057] Blade foot attachment As illustrated in figures 4a and 4b, the blade foot attachment 6 of each blade 4 comprises an external attachment piece 61 and an internal attachment piece 62 which are adapted to cooperate with the blade foot part 52 to fix the composite material structure 5 to the hub 23. The blade foot attachment 6 advantageously has a shape of revolution in order to allow angular positioning of the blade 4 relative to the hub 23.

[0058] The external attachment piece 61 is configured to be housed within the hub 23 in order to rotationally fix the blade 4 to the hub 23. The external attachment piece 61 comprises a wall 611 having an external surface 613 and an internal surface 612, both having a shape of revolution about an axis configured to be parallel to the alignment axis when the composite material structure 5 is fixed to the hub 23 via the blade foot attachment 6. The external surface 613 may have two annular grooves adapted to form raceways for balls or other rolling elements to facilitate angular alignment of the blade relative to the hub. The internal surface 612 defines a cavity 614.

[0059] The wall 611 further defines two openings 615 giving access to the cavity 614. One of the openings 615 allows the passage of the composite material structure 5 of the blade root 4 such that, once the blade root attachment 6 is assembled with the composite material structure 5, the aerodynamically profiled blade portion 51 is located outside the external attachment piece 61 and the blade root portion 52 is located inside the cavity 614. The other opening 615 allows the insertion of the internal attachment piece 62 into the housing 521 once the blade root portion 52 is inside the cavity 614.

[0060] The external attachment piece 61 is monolithic. The external attachment piece 61 can be metallic and, for example, made of martensitic steel, in order to allow for a sufficiently strong attachment of the blade 4 to the hub 23.

[0061] Internal attachment piece

[0062] The internal attachment piece 62 is configured to be disposed in the cavity 614 of the external attachment piece 61 and inside the housing 521 of the composite material structure 5 when the blade foot part 52 is inside the cavity 614. By being in the cavity 614 of the external attachment piece 61 and inside the housing 521 of the composite material structure 5, the internal attachment piece 62 locks the blade foot part 52 against the wall 611 of the external attachment piece 61.

[0063] As illustrated in Figures 5a and 5b, the internal fastener 62 comprises a main body 621 and a head 7. The main body 621 extends along an axis configured to be parallel to the mounting axis when the internal fastener 62 is positioned in the housing 521. The head 7 extends from the main body 621 along the same axis as the main body 621. The main body 621 includes a first end

[0064] 623 and a second end 624. By second end 624 is meant the part of the main body 621 on the side of the head 7 and by first end 623 is meant the part of the main body opposite the second end 624 with respect to the axis of the internal attachment piece 62. The second end 624 extends in a plane orthogonal to the axis of the internal attachment piece 62. The internal attachment piece 62 is configured so that once the internal attachment piece 62 is positioned in the housing 521, the head 7 is directed towards the side of the upper end 54 of the blade 4 and the first end 623 of the main body 621 is directed towards the side of the lower end 53 of the blade 4.

[0065] The internal fastener 62 can be monolithic, or the main body 621 and the head 7 constituting the internal fastener 62 can be two separate parts fixed to each other. Furthermore, the parts can be made of different materials and / or manufactured separately and then fixed to each other by a fastening method such as gluing.

[0066] The main body 621 may have a cylindrical shape of revolution around the axis of the internal fastener 62. Furthermore, the main body 621 may have an elliptical or even circular cross-section. This improves the strength of the internal fastener 62 and facilitates its positioning within the housing 521.

[0067] The first end 623 may include an alignment marker 625. The alignment marker 625 may be a notch, a slot, or any other mark visible to the naked eye and not weakening the main body 621. The alignment marker 625 indicates the angular orientation of the internal fastener 62 relative to the composite material structure 5 once the internal fastener 62 has been placed in the housing 521. This ensures proper orientation of the internal fastener 62 relative to the fiber reinforcement 55 and thus prevents decohesion, i.e., a crack in the matrix in which the fiber reinforcement 55 is embedded or a void between strands of the fiber reinforcement 55.

[0068] In the case of a two-part internal fastener 62, the second end

[0069] 624 may include a lug 626 projecting from the main body along the axis of the internal attachment piece 62. The lug 626 may be any type of protrusion that cooperates with the head 7 to orient the head 7 on the main body 621. The lug 626 may have various elongated shapes, such as oblong or rectangular, to constrain the orientation. Thus, the presence of a lug 626 and an alignment marker 625 allows the head 7 of the internal attachment piece 62 to be oriented relative to the fibrous reinforcement 55 once the internal attachment piece 62 is positioned in the housing 521.

[0070] As illustrated in Figures 5a, 5b and Figure 6, the head 7 comprises a contour line 70 delimiting a base 71, and a top edge 72, which together with the contour line 70 defines two lateral surfaces 73 extending from the base 71 to the top edge 72. The two lateral surfaces 73 include a first lateral surface 73a and a second lateral surface 73b. The two lateral surfaces 73 extend on either side of the top edge 72.

[0071] The head 7 further includes a vertex 723 defined as the point on the upper edge 72, furthest from the base 71, along the axis of the internal attachment piece 62.

[0072] The base 71 extends in a plane orthogonal to the axis of the internal attachment piece 62.

[0073] In the case of a monolithic internal fastener 62, the base 71 of the head 7 coincides with the second end 624 of the main body 621. In the case of an internal fastener 62 formed in two parts, the base 71 of the head 7 is in contact with the second end 624 of the main body 621. The head 7 may include a mortise 74 formed in the base 71 along the axis of the internal fastener 62. The mortise 74 is configured to receive the lug 626 and cooperate with the lug 626 to orient the head 7 relative to the main body 621. Alternatively, the main body 62 may include a mortise formed in the second end 624, and the head 7 may include a lug 626, or any other device for assembling the head 7 to the main body 621 with a specific orientation. predefined angular position of the head 7 relative to the main body 621.

[0074] The upper edge 72 forms a first intersection 721 with the contour line 70 and a second intersection 722 with the contour line 70, distinct from the first intersection 721. The first intersection 721 and the second intersection 722 divide the contour line 70 into a first portion 70a and a second portion 70b. The first portion 70a and the second portion 70b together form the entire contour line 70.

[0075] The first portion 70a of the contour line 70 delimits, together with the upper edge 72, the first lateral surface 73a. The second portion 70b of the contour line 70 delimits, together with the upper edge 72, the second lateral surface 73b.

[0076] The upper edge 72 is configured to extend between two layers of warp strands 551 delimiting the unbinding of the fibrous reinforcement 55.

[0077] The upper edge 72 is therefore positioned transversely to a Z direction (a direction perpendicular to the longitudinal X direction of the warp strands 551 and to the transverse Y direction of the weft strands 552). Thus, the head 7 has a small thickness at its apex 723 along the Z direction. In other words, the head 7 has a small thickness perpendicular to the warp strands 551 and the weft strands 552 of the fibrous reinforcement 55 between which the head 7 is positioned. This allows free expansion along the Z direction of the cross-section of the fibrous reinforcement 55 near the head 7 and thus limits the risk of cracking in the composite material structure 5 due to the thermal expansion of the composite material 5.

[0078] In the example illustrated in figures 4b, 5a and 5b, the upper edge 72 has a convex curvature from the first intersection 721 to the second intersection 722, that is to say a curved shape outwards from the head 7. This helps to further prevent the decohesion of the fibrous reinforcement 55 by progressively reducing the contact between the head 7 and the fibrous reinforcement 55.

[0079] However, in another example, the upper edge 72 can take the form of a broken ridge line. The broken ridge line can then comprise several segments of lines connected to one another. For example, the upper edge 72 can include a first segment of line extending longitudinally from the first intersection 721, a second segment of line extending in the transverse direction Y from the first segment of line, and then a third segment of line extending longitudinally from the second segment of line to the second intersection 722.

[0080] The two lateral surfaces 73 extend respectively on either side of the upper edge 72. Each of the two lateral surfaces 73 includes a concave curvature zone 731, that is, a zone curved inwards towards the head 7. More specifically, each of the two lateral surfaces 73 includes a concave curvature zone 731 in a plane parallel to the longitudinal direction X and the direction Z. This allows the thickness of the head 7 to be progressively reduced in the Z direction. In other words, the thickness separating the two lateral surfaces 73, at the junction between the two lateral surfaces 73 and the upper edge 72, is as small as possible. Furthermore, the two lateral surfaces 73 converge towards each other from the base 71 to the upper edge 72.

[0081] In practice, the upper edge 72 can consist of a narrow, convex curvature zone 732 (or a rounded edge) connecting the two concave curvature zones 731 of the two lateral surfaces 73, the radius of curvature of which does not exceed 3 mm and preferably 1.5 mm. Thus, at the junction between the concave curvature zones 731 of the two lateral surfaces 73 and the upper edge 72, the thickness separating the two lateral surfaces 73 is less than 6 mm and preferably less than 3 mm. This thickness provides mechanical strength to the head 7. Furthermore, at the junction between the narrow convex curvature zone 732 and the concave curvature zone 731, each lateral surface 73 can have a tangent parallel to the axis of the internal attachment piece 62.

[0082] Thus, the head 7 has a very reduced thickness near its upper edge 72 compared to the thickness of the base 71, in the Z direction, which prevents cracking or decohesion of the fibrous reinforcement 55 at the interface between the head 7 and the composite material structure 5. Indeed, the expansion stresses are greater in the composite material structure 5 perpendicular to the longitudinal direction X and the transverse direction Y due to the orientation of the warp strands 551 and the weft strands 552.

[0083] The two lateral surfaces 73 may further include, between the base 71 and the concave curvature zone 731, an additional convex curvature zone 733. In addition, the lateral surfaces 73 may join the base 71 along a tangent parallel to the axis of the internal attachment piece 62. This improves the continuity between the main body 621 and the head 7.

[0084] The head 7 is made of a material sufficiently strong to withstand the compression required to manufacture the composite material structure 5 and whose expansion is as similar as possible to the expansion of the composite material structure 5. The head 7 may be made of a foam material (i.e. a porous or alveolar material), in other words, the head 7 is made of a material: whose Young's modulus is less than 500 MPa, to accommodate an expansion of the composite material structure 5, which withstands a pressure of at least 7 bars, and which can withstand temperatures of at least 120°C.

[0085] The head 7 can be made of a composite material comprising an organic matrix and short fibers embedded in the organic matrix, or of polyurethane. More specifically, the head 7 can be made of a composite material comprising an organic matrix, preferably thermosetting.

[0086] This helps to limit the differential expansion between the composite material structure 5 and the head 7 of the internal attachment piece 62, and therefore to avoid cracking or decohesion of the fibrous reinforcement 55 at the interface between the head 7 and the composite material structure 5.

[0087] Manufacturing process for the blade

[0088] The blade 4 is manufactured according to a manufacturing process comprising the steps described below and illustrated for example in figure 7. The fibrous reinforcement 55 is obtained by three-dimensional weaving (step E1) of the warp strands 551 and the weft strands 552. The weaving is carried out while providing a debonding necessary for the formation of the housing 521 of the blade foot part 52.

[0089] The process then includes a positioning step E2 of the blade foot part 52 of the fibrous reinforcement 55 in the cavity 614 of the external attachment piece 61. The axis of the external attachment piece 61 is then parallel to the longitudinal direction X.

[0090] The positioning step E2 is followed by an orientation step (step E3) and an insertion step E4 of the internal attachment piece 62 into the housing 521 of the blade foot section 52. The internal attachment piece 62 is oriented so that the plane of the upper edge 72 is parallel to the longitudinal direction X and the transverse direction Y. The alignment marker 625 can be used for this purpose. Indeed, the alignment marker 625 is visible on the main body 621. The alignment marker 625 thus serves as a reference point that facilitates maintaining the orientation of the head 7 relative to the fibrous reinforcement 55 in the housing 521.

[0091] The insertion E4 of the internal attachment piece 62 into the housing 521 is carried out at the lower end 53 through one of the openings 615. The internal attachment piece 62 is inserted into the housing 521 by the head 7. The fibrous reinforcement 55 of the blade foot portion 52 is thus pressed against the internal surface 612 of the external attachment piece 61 by the internal attachment piece 62 inserted into the housing 521. The axis of the internal attachment piece 7 is then parallel to the longitudinal direction X.

[0092] Once the fibrous reinforcement 55, the external attachment piece 61, and the internal attachment piece 62 are assembled, the resulting blade 4 is inserted into a mold to obtain a preform with an aerodynamic profile. The matrix material 56 is then injected (step E5) into the mold using the RTM process to obtain the blade 4.

[0093] During the injection, the matrix 56 impregnates the entire fibrous reinforcement 55 and is thus inserted in particular between the external attachment piece 61 and the internal attachment piece 62. The resin thus makes it possible to hold the different elements together.

[0094] Thus, the blade 4 is assembled and can be fixed to the hub 23.

Claims

DEMANDS 1. Blade (4) comprising: a composite material structure (5) including a fibrous reinforcement (55) obtained by three-dimensional weaving and a matrix (56) in which the fibrous reinforcement (55) is embedded, the fibrous reinforcement (55) comprising warp strands (551) extending longitudinally and weft strands (552) extending transversely, the composite material structure (5) comprising a blade portion (51) with an aerodynamic profile and a blade root portion (52), the blade root portion (52) comprising a housing (521) extending into a debonding of the fibrous reinforcement (55) obtained during the three-dimensional weaving of the fibrous reinforcement (55), the housing (521) comprising an opening (522) to the outside of the blade root portion (52), an external attachment piece (61) comprising a wall (611) delimiting a cavity (614) and an opening (615) formed in the wall (611),the composite material structure (5) extending through the opening (615) such that the blade portion (51) is located outside the external attachment piece (61) and the blade foot portion (52) is located inside the cavity (614), and an internal attachment piece (62) disposed in the cavity (614) and inside the housing (521) such that the internal attachment piece (62) locks the blade foot portion (52) against the wall (611) of the external attachment piece (61); in which the internal attachment piece (62) comprises a main body (621) and a head (7) extending from the main body (621); the head (7) comprising a contour line (70), delimiting a base (71), and a top edge (72); the upper edge (72) extending from a first intersection (721) with the contour line (70) to a second intersection (722) with the contour line (70), distinct from the first intersection (721),the first intersection (721) and the second intersection (722) separating the contour line (70) into a first portion (70a) of contour line (70) and a second portion (70b) of contour line (70), the first portion (70a) delimiting with the upper edge (72) a first lateral surface (73a) of the head (7) and the second portion (70b) delimiting with the upper edge (72) a second lateral surface (73b) of the head (7); and the first lateral surface (73a) and the second lateral surface (73b) each comprising a concave curvature zone (731).

2. Blade (4) according to claim 1, wherein the first lateral surface (73a) and the second lateral surface (73b) each comprise, from the contour line (70) to the upper edge (72), a convex curvature zone (733) and then the concave curvature zone (731).

3. Blade (4) according to any one of claims 1 and 2, wherein the main body (621) has a cylindrical shape of revolution having an axis of revolution parallel to the longitudinal direction (X), and comprises a first end (623) and a second end (624), the second end (624) of the main body (621) and the contour line (70) of the head (7) having an elliptical section.

4. Blade (4) according to any one of claims 1 to 3, wherein the main body (621) is metallic.

5. Blade (4) according to any one of claims 1 to 4, wherein the head (7) is made of a material: whose Young's modulus is less than 500 MPa, to accommodate expansion of the composite material structure (5), which is resistant to a pressure of at least 7 bars, and which is able to withstand temperatures of at least 120°C.

6. Blade (4) according to any one of claims 1 to 5, wherein the head (7) is made of a composite material comprising an organic matrix and short fibers embedded in the organic matrix, the organic matrix preferably being made of a thermosetting material, or of polyurethane.

7. Blade (4) according to any one of claims 1 to 6, wherein the head (7) and the main body (621) are two separate parts, the head (7) being fixed on the second end (624) of the main body (621).

8. Blade (4) according to claim 7, wherein the second end (624) includes a lug (626) and the head (7) includes a mortise (74) for receiving the lug (626), the lug (626) and the mortise (74) being configured to cooperate and orient the head (7) relative to the main body (621).

9. Blade (4) according to any one of claims 1 to 8, wherein the first end (623) includes an alignment marker (625) to indicate the angular orientation of the internal attachment piece (62) relative to the composite material structure (5) once the internal attachment piece (62) has been disposed in the housing (521).

10. Gas turbine engine (1) comprising a blower (2), the blower (2) comprising a hub (23) and blades (4) extending radially from the hub (23), each of the blades (4) conforming to any one of claims 1 to 9.

11. Gas turbine engine (1) according to claim 10, in which each blade (4) is mounted to rotate relative to the hub (23) about a respective pitch axis, the engine (1) further comprising an actuation mechanism adapted to be controlled to rotate the blades (4) about their pitch axes so as to modify a pitch angle of the blades (4).

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