Blade comprising a composite material structure and a metal spar

Abstract

The invention relates to a blade (7) of a turbomachine, comprising: - an aerodynamic profile structure (20) comprising two facing skins (23), the skins (23) comprising a fibrous reinforcement densified by a matrix; - a spar (21) comprising a blade root portion (24) configured to be mounted on a hub of a rotor of the turbomachine, a blade portion (25) a strut portion (26) extending outside the aerodynamic profile structure (20) between the blade root portion (24) and the blade portion (25), the blade portion (25) comprising a body (27) connected to the blade root portion (24) and a bulb (28) extending radially from the body (27);The blade (7) further comprises a connecting piece (22) surrounding the spar (21), the connecting piece (22) extending radially from the strut part (26) beyond the blade part (25), the connecting piece (22) being integral with the spar (21), the connecting piece (22) containing the spar (21) being disposed inside the airfoil structure (20) between the two skins (23). Figure for the abbreviation: Fig. 3;

Description

Title of the invention: Blade comprising a composite material structure and a metal spar. FIELD OF THE INVENTION

[0001] The invention relates to a blade comprising a structure made of composite material.

[0002] The invention relates more particularly, but not exclusively, to a blade intended for use in an unfaired aircraft engine fan rotor (such as an "Open Rotor" type engine, i.e. one whose fan is not faired, having two rotating propellers or an "Unducted Single Fan" type engine having one moving blade and one fixed blade or a turboprop having a single propeller architecture) or in a wind turbine rotor. STATE OF THE ART

[0003] The design of blower blades requires taking into account opposing constraints.

[0004] On the one hand, the sizing of these blades must allow for optimal aerodynamic performance (maximizing efficiency and providing thrust while minimizing losses). Since improving the aerodynamic performance of the fan tends towards an increase in the bypass ratio (BPR), this translates into an increase in the external diameter, and therefore the span, of these blades.

[0005] 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.

[0006] The advantage of engines with an unfaired fan 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 dilution ratio, and consequently reduced fuel consumption.

[0007] Thus, in this type of engine, the fan blades can have a large span.

[0008] Furthermore, during the various phases, on the ground or in flight, the fan blades are subjected to several stresses such as ingestion (birds, ice, various foreign bodies). They operate in a harsh environment with significant temperature and humidity variations. For example, they are exposed to inclement weather.

[0009] It is therefore important to optimize the blades to meet these safety criteria while ensuring viable aerodynamic performance.

[0010] It has been proposed to make these blades from metallic material. While metallic blades have good mechanical resistance, they nevertheless have the disadvantage of having a relatively large mass.

[0011] In order to reduce this mass, it is desirable to be able to manufacture these blades from composite material. Description of the invention

[0012] An object of the invention is to provide a blade comprising a composite material suitable for use in an "Open Rotor" type environment while being able to withstand intense aerodynamic forces, under the constraint of limited size and minimum mass.

[0013] Another object of the invention is to provide a blade comprising a composite material suitable for use in an "Open Rotor" type environment which is capable of retaining the blade in the event of breakage of a part of the blade, particularly in the Péchasse area which is very stressed.

[0014] Another object of the invention is to provide a blade comprising a composite material suitable for use in an "Open Rotor" type environment which can be made simply and quickly, without requiring a large number of operations.

[0015] To this end, according to a first aspect of the invention, a turbine blade for a turbomachine is proposed, comprising:

[0016] - an aerodynamically profiled structure comprising two opposing skins, the skins comprising at least one fibrous reinforcement densified by a matrix;

[0017] - a longeron comprising a blade foot portion configured to be mounted on a hub of a turbomachine rotor, a blade section and a stilt section extending outside the aerodynamic profile structure between the blade root section and the blade section,

[0018] the blade part comprising a body connected to the blade root part and a bulb extending radially from the body;

[0019] the blade further comprises a connecting piece surrounding the spar, the connecting piece extending radially from the stilt part beyond the blade part, the connecting piece being integral with the spar, the connecting piece containing the spar being disposed inside the airfoil structure between the two skins.

[0020] The invention according to the first aspect is advantageously complemented by the following features, taken alone or in combination:

[0021] - the body is cylindrical in shape, the bulb comprising a lower part which flares out as it extends radially from the body;

[0022] - the bulb comprises an upper part surmounting the lower part upper being configured to ensure a continuous retention zone with the aerodynamic profile structure;

[0023] - the bulb is spherical or in the shape of a spherical ellipse;

[0024] - the connecting piece fits the bulb;

[0025] - the longeron is metallic;

[0026] - the connecting piece is one piece with the aerodynamic profile structure;

[0027] - the connecting piece is attached to the aerodynamic profile structure.

[0028] According to a second aspect, the invention proposes a blower comprising a hub and blades according to the first aspect extending radially from the hub, each blade being mounted to rotate relative to the hub around a respective staking axis.

[0029] According to a third aspect, the invention proposes a motor comprising a blower according to the second aspect of the invention.

[0030] According to a fourth aspect, the invention proposes a method for manufacturing a blade according to the first aspect, comprising the following steps:

[0031] SI: construction of the longitudinal member

[0032] S2: production of a first fibrous reinforcement of the structure with aerodynamic profile, for example by a first three-dimensional weaving;

[0033] S3: production of a second fibrous reinforcement of the connecting piece around the spar, for example by a second three-dimensional weave;

[0034] S4: insertion of the spar contained in the connecting piece into the first fibrous reinforcement so that the blade foot part is outside the first fibrous reinforcement and the blade part is inside the first fibrous reinforcement;

[0035] S5: placement of the assembly formed by the first fibrous reinforcement, the second fibrous reinforcement and the spar in a mold and injection of a matrix into the assembly so as to obtain the blade.

[0036] According to a fifth aspect, the invention proposes a method for manufacturing a blade according to the first aspect, comprising the following steps:

[0037] SI: realization of the longeron;

[0038] S2: production of a first fibrous reinforcement of the structure with an aerodynamic profile, for example by a first three-dimensional weaving;

[0039] S3': realization of the second fibrous reinforcement of the connecting piece in the first fibrous reinforcement for example by a second three-dimensional weave different from the first three-dimensional weave;

[0040] S4': insertion of the longeron into the second fibrous reinforcement so that the part of the blade foot is located outside the first fibrous reinforcement and the blade part is located inside the second fibrous reinforcement;

[0041] S5: placement of the assembly formed by the first fibrous reinforcement, the second fibrous reinforcement and the spar in a mold and injection of a matrix into the assembly so as to obtain the blade. DESCRIPTION OF THE FIGURES

[0042] Other features, purposes and advantages of the invention 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:

[0043] [Fig.1] Fig.1 schematically represents an example of an engine including an unfaired fan.

[0044] [Fig.2] Fig.2 illustrates an example of an aircraft comprising engines conforming to an embodiment of the invention.

[0045] [Fig.3] Fig.3 schematically represents a blower blade and a actuation mechanism allowing modification of the angle of the blower blades.

[0046] [Fig.4] Fig.4 is a view of a first example of the embodiment of a longitudinal member of a blade housed in a connecting piece according to the invention.

[0047] [Fig. 5] Fig. 5 is a flowchart illustrating the steps of a process of manufacturing a waterwheel according to two methods of construction.

[0048] Throughout the figures, similar elements bear identical references. DETAILED DESCRIPTION OF THE INVENTION

[0049] In relation to [Fig.1], a motor 1 shown is an "Open Rotor" type motor, in a configuration commonly referred to as "pusher" (i.e. the unfaired blower is placed at the rear of the power generator with an air inlet located on the side, to the right in [Fig.1]).

[0050] As illustrated in [Fig. 2], the engine 1 comprises a nacelle 2 for attachment to the fuselage of an aircraft 100 and an unfaired fan 3 (or propeller). The fan 3 advantageously comprises two counter-rotating fan rotors 4 and 5. In other words, when the engine 1 is running, the rotors 4 and 5 are driven in rotation relative to the nacelle 2 about the same axis of rotation X (which coincides with a principal axis of the engine), in opposite directions.

[0051] In the example illustrated in [Fig. 1], the motor 1 is an "Open Rotor" type motor in a "pusher" configuration with counter-rotating fan rotors. However, the invention is not limited to this configuration. The invention also applies to "Open Rotor" type motors in a "puller" configuration (i.e., the fan is placed upstream of the power generator with an air inlet located before, between, or just behind the two fan rotors).

[0052] In addition, the invention also applies to motors having different architectures, such as an architecture comprising a blower rotor including movable blades and a blower stator including fixed blades, or a single blower rotor.

[0053] The invention is applicable to turboprop type architectures (comprising a single fan rotor), as well as to wind turbine rotors.

[0054] In the present application, the axis of rotation of the fan rotor 4, 5 (or propeller) is called axis X. The axial direction corresponds to the direction of axis X, and a radial direction is a direction perpendicular to and passing through this axis X. Each blade 7 is mounted to rotate relative to the hub 6 about a respective y-axis: this y-axis Y extends in a generally radial direction with respect to axis X. Finally, internal (respectively, inner) and external (respectively, outer), respectively, are used with reference to a radial direction such that the inner part or face of an element is closer to axis X than the outer part or face of the same element.

[0055] The blade 7 is thus defined with respect to the X axis of the rotor on which it is intended to be mounted and its Y axis of alignment.

[0056] In [Fig. 1], each blower rotor 4, 5 comprises a hub 6 (or blade hub) rotatably mounted relative to the nacelle 2 and a plurality of blades 7 fixed to the hub 6. The blades 7 extend substantially radially relative to the axis of rotation X of the rotor.

[0057] As illustrated in [Fig. 3], the fan 3 includes an actuation mechanism 8 for collectively adjusting the pitch angle of the rotor blades 7 to adapt engine performance to different flight phases. For this purpose, each blade 7 includes a mounting piece 9 (or blade hub) located at the blade root. The mounting piece 9 is rotatably mounted relative to the hub 6 about a pitch axis Y. More precisely, the mounting piece 9 is rotatably mounted within a housing 10 formed in the hub 6, by means of balls 11 or other rolling elements.

[0058] Alternatively, each blade 7 may include a cylindrical blade foot configured to be connected directly to the hub 6 via bearings.

[0059] The actuation mechanism 8 includes, for example, an actuator 12 comprising a body 13 fixed to the hub 6 and a rod 14 adapted to be driven in translation relative to the body 12. The actuation mechanism 8 further includes an annular slide 15 mounted integrally with the rod 14 and a pin 16 mounted integrally with the attachment piece 9. The pin 16 is adapted to slide in the slide 15 and to rotate relative to the slide 15, so as to convert a translational movement of the rod 14 into a rotational movement of the attachment piece 9, and by consequently a rotational movement of the blade 7 relative to the hub 6 around its alignment axis Y.

[0060] The blade 7 includes an aerodynamic profile structure 20 (or blade 20) suitable for being placed in an airflow when the engine 1 is in operation in order to generate lift, a spar 21 surrounded by a connecting piece 22 (or sock).

[0061] The blade 20 comprises two skins 23, which are connected to each other and extend generally opposite each other. The skins 23 are shaped to define together an intrados, an extrados, a leading edge, and a trailing edge of the blade 7. As is known per se, the leading edge is configured to extend opposite the flow of gases entering the engine 1. It corresponds to the forward part of an airfoil that faces the airflow and divides the airflow into an intrados flow and an extrados flow. The trailing edge, for its part, corresponds to the rear part of the airfoil, where the intrados and extrados flows meet.

[0062] The skins 23 of the aerodynamic profile structure 20 are made of a composite material comprising a fibrous reinforcement densified by a matrix. They are therefore monolithic and are made in one piece according to a non-limiting embodiment.

[0063] The fibrous reinforcement can be formed from a one-piece fibrous preform with varying thickness. The fibers of the fibrous reinforcement comprise at least one of the following materials: carbon, glass, aramid, polypropylene, and / or ceramic. The fibrous reinforcement may comprise woven (two-dimensional or three-dimensional), braided, knitted, or laminated fibrous arrangements. The matrix typically comprises an organic material (thermoset, thermoplastic, or elastomer) or a carbon matrix. For example, the matrix comprises a plastic material, typically a polymer, such as epoxy, bismaleimide, or polyimide.

[0064] As can be seen in [Fig. 4], the spar 21 comprises a blade root portion 24 extending outside the blade 20, a blade portion 25 located inside the blade 20, between the two skins 23, and a strut portion 26 extending between the blade root portion 24 and the blade portion 25. The blade root portion 24 is configured to be inserted into the hub 6, optionally by means of a fastener 9. The strut portion 26 corresponds to the area of ​​the spar 21 extending between the hub 6 outlet and the blade 20.

[0065] The spar 21 is advantageously made of metal and in one piece: the blade root portion 24, the blade portion 25, and the strut portion 26 are therefore monolithic. The metallic material of the spar 21 may comprise at least one of the following materials: steel, titanium, a titanium alloy (in particular TA6V, comprising titanium, aluminum, vanadium, and traces of carbon), iron, oxygen, and nitrogen), a nickel-based superalloy such as Inconel, an aluminum alloy. The fabrication of the metal spar 21 can involve several specific processes such as machining, forging, forming, casting, or additive manufacturing (3D printing).

[0066] In order to resist intense aerodynamic forces, the blade portion 25 of the spar 21 comprises a main body 27 connected to the blade root portion 24 and a bulb 28 which initially extends radially, flaring out from a vertex of the body 27, gradually moving away from the Y-axis and then converging towards the Y-axis. The bulb 28 is therefore a closed structure comprising a lower bulge 28a extending from the main body 27 and an upper portion 28b extending from the bulge 28a to close the spar 21.

[0067] The bulb 28 is preferably spherical (as in [Fig.3]) or in the shape of a spherical ellipse, that is to say that it is more than wide.

[0068] More generally, the bulb 28 gives the spar 21 a generally flared, bulged or domed shape at the junction with the main body 27 in the blade 20.

[0069] The spar 21 is advantageously surrounded by a connecting piece 22 extending from the strut portion 26 into the blade portion 25. The connecting piece 22 is advantageously made of a composite material comprising a fibrous reinforcement densified by a matrix. The connecting piece 22 is therefore, like the airfoil structure 20, made of composite material. The connecting piece 22 is in contact with the blade 20.

[0070] The connecting piece 22 therefore fully houses the spar 21. Thus, the spar 21 and connecting piece 22 together form the core of the blade 7.

[0071] The connecting piece 22 can take several forms provided that it completely surrounds the spar 21: it can include a lower part 22a extending from the stilt part, for example cylindrical, surmounted by an upper part 22b extending from the lower part 22a of the connecting piece 22.

[0072] The upper part 22b of the connecting piece 22 is such that it does not have sharp edges to allow a smooth connection with the profile 20 of the blade.

[0073] The connecting piece 22 is always woven around the bulb 28 and longeron 21. Then, it is: - To insert the assembly formed by the longitudinal member 21 and the connecting piece 22 into a preform having a dedicated cavity and to proceed with the injection of resin (co-injection); - To insert the assembly formed by the longitudinal member 21 and the connecting piece 22 into a preform by weaving between the connecting piece 22 and the cavity of the preform and then to proceed with the injection of the resin.

[0074] In this latter case, the cavity designed to house a conventional longeron is distinguished by the opening. The longeron 21 is held in place by a 3D weave of the connecting piece 22 around the bulb 28 and then inserted into the preform. In a conventional cavity, the bulb would not have a 3D weave for support because the cavity would be completely open on its underside.

[0075] Thus, the connecting piece 22 made of composite material is secured to the blade 20 while containing the spar 21.

[0076] The shape of the spar 21 described here includes a larger contact area with the woven composite of the blade and a retention zone of spherical shape (the upper part 28b of the bulb 28). Thus, if the blade 20 appears to want to escape by centrifugal force, the spar 21 will exert a contrary force to retain it. In particular, during the rotation of the fan, centrifugal forces will pull the blades outwards. Under opposing forces, the blades will exert a retaining force inwards (if this force is not maintained, it constitutes a blade loss).

[0077] Indeed, the geometry of the spar 21, having in particular this swollen shape in the lower part 28a, allows the connecting piece 22 to be retained around and the skins 23 of the blade 20 to be retained. Indeed, under the effect of centrifugal forces oriented in the radial direction, the connecting piece 22 takes up the forces and the connection between the connecting piece 22 and the blade 20 prevents the blade 20 from escaping.

[0078] On a spar without a bulb (for example, a straight one), the forces are absorbed on the spar's retention slopes, which are limited in angle for insertion. The shape of the spar of the invention with a bulb provides complete counter-support to retain the forces created by centrifugal force. The forces are absorbed by the bulb 28 instead of being exerted on the contour of the connecting piece 22, thus retaining the entire blade 20.

[0079] From a mechanical point of view, the spar 21 also makes it possible to increase the stiffness of the structure of the blade 7 while maintaining a reduced mass.

[0080] In one embodiment, the spar extends over approximately 15% of the blade and the connecting piece 22 over approximately 30% of the blade 20.

[0081] The minimum thicknesses of the composites are between 5 mm and 7.2 mm. It follows that the dimensions of the bulb are smaller than the space between the skins 23, ensuring a minimum composite thickness. Of course, this varies depending on the aerodynamic volume chosen for the blade 20.

[0082] The blade foot part 24 is advantageously in the shape of a hemisphere.

[0083] The longeron 21 may be hollow. Alternatively, only a part of the longeron 21 It can be hollow, while the rest of the spar 21 can be solid. According to yet another variant, the entire spar 21 is solid. Example of a manufacturing process

[0084] In relation to [Fig.5], a blade 7 according to the invention can be obtained in accordance with the following steps.

[0085] During a step SI, the longeron 21 is manufactured. Any conventional method can be used here, including machining, forging, forming, casting or even additive manufacturing (3D printing) for the production of the longeron 21.

[0086] During step S2, a first fibrous reinforcement of the blade 20 is produced. This first fibrous reinforcement can be produced by three-dimensional weaving on a Jacquard-type loom. During weaving, bundles of warp strands are arranged in several layers. Weft strands T are interlaced with the warp strands C so as to link the different layers of warp strands C together. The three-dimensional weave can be an interlock weave. Interlock refers to a weave structure in which each layer of weft strands links several layers of warp strands with all the strands in the same weft column having the same movement in the plane of the weave.

[0087] Other known types of three-dimensional weaves may be used, such as those described in document WO 2006 / 136755.

[0088] According to a first embodiment, a second fibrous reinforcement of the connecting piece 22 is then made around the spar 21 in a step S3. This second fibrous reinforcement is made using a similar technique to that used for the first fibrous reinforcement. According to this embodiment, the connecting piece 22 is woven directly around the spar 21.

[0089] Next, in a step S4, the spar 21 contained in the connecting piece 22 is inserted into the first fibrous reinforcement so that the blade foot part 24 is outside the first fibrous reinforcement and the blade part 25 is inside the first fibrous reinforcement.

[0090] In order to allow the insertion (step S4) of the spar 21 contained in the connecting piece 22 into the blade 20, a disconnection is made in the first fibrous reinforcement.

[0091] According to a second embodiment, in a step S3', the second fiber reinforcement of the connecting piece 22 is directly formed within the first fiber reinforcement of the blade 20. Rather than simply providing a cavity, a specific arrangement is provided for the spar 21 to facilitate its retention. Unlike the first embodiment, here the connecting piece 22 is a single piece with the first fiber reinforcement of the blade 20.

[0092] Next, in a step S4', the spar 21 is inserted into the second fibrous reinforcement so that the blade foot part 24 is outside the first fibrous reinforcement 23 and the blade part 25 is inside the first fibrous reinforcement.

[0093] In addition, the first and second fibrous reinforcements are linked together.

[0094] According to a third embodiment, a single fiber reinforcement is produced and comprises a single block having the aerodynamic structure and the connecting piece for the spar. The spar is then inserted into the connecting piece.

[0095] Regardless of whether the first or second embodiment is shown, during a step S5, the resulting assembly, consisting of the spar 21, the first fiber reinforcement, and the connecting piece 22, is placed in a mold having a cavity shaped like the final molded part (namely, the blade 7), and plastic material (the "matrix" of the blade) is injected into the mold so as to impregnate the first and second fiber reinforcements. The plastic injection can be carried out using an RTM or VARRTM type injection technique. The injected plastic material is, for example, a thermosetting liquid composition containing an organic precursor of the matrix material. The organic precursor is usually in the form of a polymer, such as a resin, possibly diluted in a solvent.

[0096] In a method known per se, the plastic material is heated to induce polymerization, for example by cross-linking. For this purpose, the mold is placed in an oven. The resulting part is then demolded and, optionally, trimmed by machining to remove excess length and obtain a part with the desired shape, despite any possible shrinkage of the reinforcing fibers during the polymerization of the plastic material.

[0097] Then, during a step S6, an attachment piece 9 can optionally be fitted and fixed to the blade foot 7, around the blade foot portion 24 of the spar 21. It can, in particular, be machined to form a cavity whose shape and dimensions correspond to those of the blade foot portion 24. Optionally, the attachment piece 9 can be made in two parts so that it can be fitted and fixed around the blade foot portion 24 using two dedicated rings, for example by shrink fitting, screwing, welding, or even with a hose clamp. The step S6 of fixing the attachment piece 9 can therefore be carried out before or after injection molding (step S5). Advantageously, the material of the attachment piece 9 can be different from that of the spar 21.

Claims

Demands

1. Blade (7) of a turbomachine, comprising: - an aerodynamic profile structure (20) comprising two facing skins (23), the skins (23) comprising at least one fibrous reinforcement densified by a matrix; - a spar (21) comprising a blade root portion (24) configured to be mounted on a hub of a rotor of the turbomachine, a blade portion (25) a strut portion (26) extending outside the aerodynamic profile structure (20) between the blade root portion (24) and the blade portion (25); the blade part (25) comprising a body (27) connected to the blade root part (24) and a bulb (28) extending radially from the body (27), the bulb (28) being a closed structure comprising a lower bulge (28a) extending from the body (27) and an upper part (28b) extending from the bulge (28a) to close the spar (21);the blade (7) further comprises a connecting piece (22) surrounding the spar (21), the connecting piece (22) extending radially from the strut part (26) beyond the blade part (25), the connecting piece (22) being integral with the spar (21), the connecting piece (22) containing the spar (21) being disposed inside the airfoil structure (20) between the two skins (23).

2. Blade (7) according to claim 1, wherein the body (27) is cylindrical in shape, the bulb (28) comprising a lower part (28a) which flares out by extending radially from the body (27).

3. Blade (7) according to claim 2, wherein the bulb (28) comprises an upper part (28b) surmounting the lower part (28a), the upper part being configured to ensure a continuous retention zone with the aerodynamic profile structure (20).

4. Blade (7) according to any one of claims 1 to 3, wherein the bulb (28) is spherical or spherically elliptical.

5. Blade (7) according to any one of claims 1 to 4, wherein the connecting piece (22) fits the bulb (28).

6. Blade (7) according to any one of claims 1 to 5, wherein the longeron (21) is metallic.

7. Blade (7) according to any one of claims 1 to 6, wherein the connecting piece (22) is one piece with the aerodynamic profile structure (20).

8. Blade (7) according to any one of claims 1 to 6, wherein the connecting piece (22) is related to the aerodynamic profile structure (20).

9. Blower (3) comprising a hub (6) and blades (7) according to any one of claims 1 to 8 extending radially from the hub (6), each blade (7) being mounted rotatably relative to the hub about a respective staking axis (Y).

10.

11. Motor (1) comprising a blower (3) according to claim 9.Method of manufacturing a blade (7) according to any one of claims 1 to 8, comprising the following steps: S1: making the spar (21); S2: making a first fibrous reinforcement of the airfoil structure (20), for example by a first three-dimensional weave; S3: making a second fibrous reinforcement of the connecting piece (22) around the spar (21), for example by a second three-dimensional weave; S4: inserting the spar (21) contained in the connecting piece (22) into the first fibrous reinforcement so that the blade root portion (24) is outside the first fibrous reinforcement (23) and the blade portion (25) is inside the first fibrous reinforcement (23); S5: placement of the assembly formed by the first fibrous reinforcement (23), the second fibrous reinforcement (26) and the spar (21) in a mold and injection of a matrix into the assembly so as to obtain the blade (7).

12. A method for manufacturing a blade (7) according to any one of claims 1 to 8, comprising the following steps: S1: making the spar (21); S2: making a first fibrous reinforcement of the airfoil structure (20), for example by a first three-dimensional weave; S3': making a second fibrous reinforcement of the connecting piece (22) in the first fibrous reinforcement, for example by a second three-dimensional weave different from the first three-dimensional weave; S4': insertion of the spar (21) into the second fibrous reinforcement so that the blade foot part (24) is outside the first fibrous reinforcement (23) and the blade part (25) is inside the second fibrous reinforcement (23); S5: placement of the assembly formed by the first fibrous reinforcement (23), the second fibrous reinforcement (26) and the spar (21) in a mold and injection of a matrix into the assembly so as to obtain the blade (7).

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