INTERNAL ATTACHMENT PIECE FOR HYBRID BLADE FOOT

Abstract

The present invention relates to a blade comprising: a composite material structure including a blade foot portion comprising a housing, an external attachment piece, and an internal attachment piece disposed inside the housing; wherein the internal attachment piece includes a head comprising a contour line, delimiting a base, and a top edge; the top edge extending between a first and a second intersection with the contour line, the first and second intersections dividing the contour line into a first and a second portion; the first portion delimiting, with the top edge, a first lateral surface and the second portion delimiting, with the top edge, a second lateral surface; and the first and second lateral surfaces each comprising a concave curvature zone. Figure for the abstract: Fig. 4b

Description

Title of the invention: INTERNAL ATTACHMENT PIECE FOR HYBRID BLADE FOOT FIELD OF THE INVENTION

[0001] The present description relates to a variable pitch blade comprising a composite material structure and a blade foot attachment.

[0002] The present exposition 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. STATE OF THE ART

[0003] 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.

[0004] The advantage of engines with unfaired fans is that the diameter of the fan is not limited by the presence of a fairing, so that it is possible to design an engine with a high bypass ratio or BPR (ByPass Ratio according to Anglo-Saxon terminology), and consequently reduced fuel consumption.

[0005] Thus, in this type of engine, the fan blades can have a large span.

[0006] In addition, these engines generally include a mechanism for changing the angle of the blades in order to adapt the thrust generated by the fan according to the different phases of flight.

[0007] However, the design of such blades requires taking into account opposing constraints.

[0008] On the one hand, the dimensioning of these blades must allow optimal aerodynamic performance (maximize propulsive efficiency and provide thrust while minimizing losses) and therefore requires an increase in the external diameter, and thus in the span of the blades.

[0009] On the other hand, it is also necessary to guarantee resistance to the mechanical stresses that may be exerted on these blades while limiting their acoustic signature.

[0010] These blades can be made of metallic material. While blades made of metallic material have good mechanical resistance, they nevertheless have the disadvantage of having a relatively large mass.

[0011] 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 to which they are subjected. These aerodynamic stresses can therefore damage the blades and / or the hub in the interface zone between the blades and the fan rotor hub, at the blade root.

[0012] A metal attachment to the blade root could limit damage to the blade and / or hub in the interface area. However, the difference in material between the metal attachment and a portion of the blade made of composite material can induce decohesion or cracking in the composite material. Decohesion is a crack or separation in the composite material. Decohesion can occur primarily in the area at the interface between the composite material and the metal. Indeed, the composite material and the metal do not have the same coefficient of thermal expansion, which induces differential expansion between the blade root attachment and the composite blade root. Description of the invention

[0013] One aim of the present 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.

[0014] For this purpose, according to one aspect of the present description, a blade is proposed comprising: - a composite material structure comprising 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 along a longitudinal direction of the blade and weft strands extending along a transverse direction of 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 along the longitudinal direction 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 part comprising a wall delimiting a cavity and an opening formed in the wall, the structure made of composite material extending through the opening in such a way that the blade portion is located outside the external attachment piece and the blade root portion is located inside the cavity, and - an internal fastening piece arranged in the cavity and inside the housing so that the internal fastening piece locks the blade foot part against the wall of the external fastening piece;

[0015] in which the internal attachment piece comprises a main body extending along the longitudinal direction and a head extending from the main body;

[0016] the head comprising a contour line, delimiting a base, and a top edge;

[0017] the upper 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 the contour line and a second portion of the contour line,

[0018] 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

[0019] the first lateral surface and the second lateral surface and each comprising a concave curvature zone.

[0020] Advantageously, but optionally:

[0021] - the first lateral surface and the second lateral surface are separated by the upper edge and each include, from the contour line to the upper edge, a convex curvature zone and then the concave curvature zone;

[0022] - 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, ;

[0023] - the main body is metallic;

[0024] - the head is made of a material:

[0025] whose Young's modulus is less than 500 MPa, to accommodate expansion of the composite material structure,

[0026] which can withstand a pressure of at least 7 bars, and

[0027] which can withstand temperatures of at least 120°C;

[0028] - the head is made of a composite material comprising an organic matrix and fibers short ones embedded in the organic matrix, the organic matrix preferably being made of a thermosetting material, or polyurethane;

[0029] - the head and the main body are two separate parts, the head being fixed to the second end of the main body;

[0030] - the second end includes an oblong lug and the head includes a mortise to receive the spur, the spur and the mortise being configured to cooperate and orient the head relative to the main body;

[0031] - the first end includes an alignment marker to indicate the angular orientation of the internal fastener relative to the composite material structure once the internal fastener has been positioned in the housing.

[0032] According to another aspect of the present exposition, 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.

[0033] Advantageously, but optionally, each blade is mounted to rotate about a respective alignment axis relative to the hub, the motor further comprising an actuation mechanism that can be controlled to rotate the blades about their alignment axes so as to modify the blade pitch angle. DESCRIPTION OF FIGURES

[0034] Other features, purposes and advantages will become apparent from the following description, which is purely illustrative and not limiting, and which should be read in conjunction with the accompanying drawings on which:

[0035] Fig. 1 represents a schematic perspective view of a gas turbine engine according to an embodiment of the present exposition.

[0036] Fig. 2 represents a schematic view of a blade according to one embodiment of the present exposition.

[0037] Fig. 3 represents a schematic view of a composite material structure of a blade according to an embodiment of the present description.

[0038] Fig. 4a and Fig. 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 disclosure.

[0039] Fig. 5a and Fig. 5b represent cross-sectional views of an internal attachment part of a blade according to an embodiment of the present disclosure.

[0040] Fig. 6 illustrates a top view of a head of an internal fastener according to an embodiment of the present disclosure.

[0041] Figure [Fig.7] illustrates a flowchart of the steps of a blade assembly process according to a particular implementation of the present exposition.

[0042] Throughout the figures, similar elements bear identical references. DETAILED DESCRIPTION OF THE INVENTION Aircraft

[0043] An aircraft is a device configured to rise and move through the air, and can, for example, be 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

[0044] In the example illustrated in [Fig. 1], the propulsion system shown is an unfaired gas turbine engine 1. The propulsion system is configured to be fixed to the aircraft's airframe, for example under its wings in the case of an airplane, by means of a pylon (or mast). The propulsion device can also be mounted on the wing of the airplane or at the rear of its fuselage, or even be integrated into its fuselage.

[0045] Alternatively, the propulsion system may be a ducted twin-body, twin-flow, direct-drive 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 a turboprop, with or without afterburner.

[0046] The engine 1 illustrated in [Fig. 1] comprises, from upstream to downstream, a blower 2 and a primary body 3, often called a "gas generator". The primary body 3 comprises a combustion chamber and a turbine section.

[0047] In operation, an airflow F entering the propulsion system is divided into a primary airflow and a secondary airflow, which flow from upstream to downstream in 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 supplied by the engine 1.

[0048] The fan 2 can be enclosed or unenclosed (or "open rotor" according to 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" ("unenclosed fan" in French terminology)) or two counter-rotating rotors 21 (or "CROR" for "Contra-Rotating Open Rotor" in Anglo-Saxon terminology ("contra-rotating open rotor" in French terminology), or "UDF" for "Unducted Double Fan" ("unenclosed 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.

[0049] 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 of [Fig. 1].

[0050] As illustrated in [Fig. 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 this 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.

[0051] The stator 22, or stator, comprises blades 4 mounted on a hub 23 of the stator 22 and its function is to straighten the secondary airflow exiting the rotor 21. The stator 22 blades 4 may be fixed relative to the hub 23 of the stator 22 or have a variable pitch. If so, and similarly to the rotor 21 blades 4, the base of the stator 22 blades 4 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 being 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. Dawn

[0052] 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.

[0053] 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 root portion 52.

[0054] 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.

[0055] The aerodynamically profiled portion of the blade 51 is designed to be placed in an airflow, when the engine 1 is running, in order to generate lift. The Part of blade 51 can present an aerodynamic profile in all three directions of space.

[0056] 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.

[0057] The composite material structure 5 comprises a fibrous reinforcement 55 obtained by three-dimensional weaving and a matrix in which the fibrous reinforcement 55 is embedded during the manufacturing of the blade. The weaving and embedding of the fibrous reinforcement 55 enable the blade portion 51 to achieve its aerodynamic profile. The fibrous reinforcement 55 comprises warp strands 551 extending longitudinally in the blade 4 (i.e., from the lower end 53 to the upper end 54) and weft strands 552 extending transversely in 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.

[0058] The warp strands 551 and the 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.

[0059] 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. Dawn foot attachment

[0060] 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.

[0061] The external attachment piece 61 is configured to be housed in the hub 23 in order to rotatably fix the blade 4 to the hub 23. The external attachment piece 61 The structure 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 attached 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.

[0062] 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.

[0063] The external attachment piece 61 is monolithic. The external attachment piece 61 may be metallic and, for example, made of martensitic steel, in order to allow a sufficiently strong attachment of the blade 4 to the hub 23. Internal attachment piece

[0064] 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 portion 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 portion 52 against the wall 611 of the external attachment piece 61.

[0065] 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 comprises a first end 623 and a second end 624. The second end 624 is understood to be the portion of the main body 621 on the side of the head 7, and the first end 623 is understood to be the portion of the main body opposite the second end 624 with respect to the axis of the internal fastener 62. The second end 624 extends in a plane orthogonal to the axis of the internal fastener 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.

[0066] The internal attachment piece 62 may be monolithic, or the main body 621 and the head 7 constituting the internal attachment piece 62 may be two separate pieces fixed to each other. Furthermore, the pieces may be made of different materials and / or manufactured separately and then fixed to each other by a fastening method such as gluing, for example.

[0067] The main body 621 may have a cylindrical shape of revolution about the axis of the internal attachment piece 62. Furthermore, the main body 621 may have an elliptical or even circular cross-section. This improves the strength of the internal attachment piece 62 and facilitates its positioning in the housing 521.

[0068] 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.

[0069] In the case of a two-part internal fastener 62, the second end 624 may include a lug 626 projecting from the main body along the axis of the internal fastener 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 be of 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 fastener 62 to be oriented relative to the fibrous reinforcement 55 once the internal fastener 62 is positioned in the housing 521.

[0070] As illustrated by Figures 5a, 5b and [Fig. 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 delimits two lateral surfaces 73 extending from the base 71 to the top edge 72. The two lateral surfaces 73 comprise 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 comprises 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 attachment piece 62, the base 71 of the head 7 is coincident 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 predefined angular orientation 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 direction Z (a direction perpendicular to the longitudinal direction X of the warp strands 551 and to the transverse direction Y 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 of 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, a shape curved outwards from the head 7. This allows to further avoid 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 may have the form of a broken ridge line. The broken ridge line may then comprise several segments of lines connected to one another. For example, the upper edge 72 may comprise 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 (or rounded) zone 732 connecting the two concave zones 731 of the two lateral surfaces 73, the radius of which does not exceed 3 mm and preferably 1.5 mm. Thus, at the junction between the concave 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.

[0082] Furthermore, at the junction between the narrow zone of convex curvature 732 and the zone of concave curvature 731, each lateral surface 73 can present a tangent parallel to the axis of the internal attachment piece 62.

[0083] Thus, the head 7 has, near its upper edge 72, a very reduced thickness 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.

[0084] 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.

[0085] 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 that of the composite material structure 5. The head 7 may be made of a foam material (i.e., a porous or cellular material), in other words, 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 can withstand a pressure of at least 7 bars, and - which can withstand temperatures of at least 120°C.

[0086] The head 7 may 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 may be made of a composite material comprising an organic matrix, preferably thermosetting.

[0087] This makes it possible 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. Blade manufacturing process

[0088] The blade 4 is manufactured according to a manufacturing process comprising the steps described below and illustrated for example in [Fig.7].

[0089] The fibrous reinforcement 55 is obtained by three-dimensional weaving (step El) 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.

[0090] The method then includes a positioning step E2 of the blade foot portion 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.

[0091] 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 portion 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. This can be achieved using the alignment marker 625. Indeed, the alignment marker 625 is visible on the main body 621. The marker alignment 625 is therefore a reference point facilitating the maintenance of the orientation of the head 7 relative to the fibrous reinforcement 55 in the housing 521.

[0092] The insertion E4 of the internal attachment piece 62 into the housing 521 is carried out at the lower end 53 by 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.

[0093] Once the fibrous reinforcement 55, the external attachment piece 61, and the internal attachment piece 62 are assembled, the blade 4 thus formed 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 according to the RTM process to obtain the blade 4.

[0094] During the injection, the matrix 56 impregnates the entire fibrous reinforcement 55 and thus inserts itself in particular between the external attachment piece 61 and the internal attachment piece 62. The resin thus makes it possible to hold the various assembled elements together.

[0095] Thus, the blade 4 is assembled and can be fixed to the hub 23.

Claims

Demands

1. 1. Dawn (4) comprising: - a composite material structure (5) comprising 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 root portion (52) is located inside the cavity (614), and - an internal attachment piece (62) disposed in the cavity (614) and inside the housing (521) so that the internal attachment piece (62) locks the blade foot part (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 withstands a pressure of at least 7 bars, and - which withstands 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 pieces distinct, 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, wherein each blade (4) is mounted rotatably relative to the hub (23) around a respective pitch axis, the engine (1) further comprising an actuation mechanism suitable for being controlled to rotate the blades (4) around their pitch axes so as to modify a pitch angle of the blades (4).

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