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 unducted fan rotor of an aircraft engine (such as an “Open Rotor” type engine, i.e. one whose fan is not ducted, having two rotating propellers or a USF type engine for “Unducted Single Fan” having a moving blade and a fixed blade or a turbo-propeller having an architecture with a single propeller) or in a wind turbine rotor. STATE OF THE ART

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

[0004] On the one hand, the dimensioning of these blades must allow optimal aerodynamic performances (maximize efficiency and provide thrust while minimizing losses). The improvement of the aerodynamic performances of the fan tending towards an increase in the dilution ratio (BPR, in English ByPass Ratio), this results in an increase in the external diameter, and therefore in the span of these blades.

[0005] On the other hand, it is also necessary to guarantee resistance to the mechanical stresses that can be exerted on these blades while limiting their acoustic signature.

[0006] The advantage of unducted fan engines 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, and consequently reduced fuel consumption.

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

[0008] Furthermore, during the different phases, on the ground or in flight, the fan blades are subjected to several constraints such as ingestion (birds, ice, various foreign bodies). They operate in a harsh environment with large disparities in temperature or humidity. For example, they are subjected to bad 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. Although blades made from metallic material have good mechanical strength, they nevertheless present the disadvantage of having a relatively large flock.

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

[0012] An aim of the invention is to propose a blade comprising a composite material suitable for use in an “Open Rotor” type environment while being capable of withstanding intense aerodynamic forces, under the constraint of limited bulk and minimal mass.

[0013] Another aim of the invention is to propose 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, in particular in the Péchasse zone which is highly stressed.

[0014] Yet another aim of the invention is to provide a blade comprising a composite material suitable for use in an “Open Rotor” type environment which can be produced simply and quickly, without requiring a large number of operations.

[0015] For this purpose, according to a first aspect of the invention, a blade of a turbomachine is proposed, comprising:

[0016] - an aerodynamic profile structure comprising two facing skins, the skins comprising at least one fibrous reinforcement densified by a matrix;

[0017] - a spar comprising a blade root portion configured to be mounted on a hub of a rotor of the turbomachine, a blade portion a stilt portion extending outside the airfoil structure between the blade root portion and the blade portion,

[0018] the blade portion comprising a body connected to the blade root portion 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 portion beyond the blade portion, the connecting piece being integral with the spar, the connecting piece containing the spar being arranged inside the aerodynamically profiled structure between the two skins.

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

[0021] - the body is cylindrical in shape, the bulb having a lower part which flares out, extending radially from the body;

[0022] - the bulb has an upper part surmounting the lower part, the part su upper being configured to provide a continuous retention area with the airfoil structure;

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

[0024] - the connecting piece fits the bulb;

[0025] - the spar is metallic;

[0026] - the connecting piece is in 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 provides a fan comprising a hub and blades according to the first aspect extending radially from the hub, each blade being rotatably mounted relative to the hub about a respective pitch axis.

[0029] According to a third aspect, the invention provides an engine comprising a fan according to the second aspect of the invention.

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

[0031] SI: production of the spar

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

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

[0034] S4: inserting the spar contained in the connecting piece into the first fiber reinforcement so that the blade root portion is located outside the first fiber reinforcement and the blade portion is located inside the first fiber reinforcement;

[0035] S5: placement of the assembly formed by the first fiber reinforcement, the second fiber 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 of manufacturing a blade according to the first aspect, comprising the following steps:

[0037] SI: production of the spar;

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

[0039] S3': production of the second fiber 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 spar into the second fiber reinforcement so that the part of blade root is located outside the first fiber reinforcement and the blade part is located inside the second fiber reinforcement;

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

[0042] Other characteristics, aims and advantages of the invention will emerge from the following description, which is purely illustrative and non-limiting, and which must be read in conjunction with the appended drawings in which:

[0043] [Fig.l] [Fig.l] schematically represents an example of an engine including an unducted 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 fan blade and a actuating mechanism for changing the pitch angle of the fan blades.

[0046] [Fig.4] [Fig.4] is a view of a first example of the embodiment of a spar 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 fa process construction of a blade according to two embodiments.

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

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

[0050] As illustrated in [Fig.2], the engine 1 comprises a nacelle 2 intended to be fixed to a fuselage of an aircraft 100 and an unducted 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 in operation, the rotors 4 and 5 are rotated relative to the nacelle 2 around the same axis of rotation X (which coincides with a main axis of the engine), in opposite directions.

[0051] In the example illustrated in [Fig.l], the engine 1 is an “Open Rotor” type engine in “pusher” configuration with counter-rotating fan rotors. However, the invention is not limited to this configuration. The invention also applies to “Open Rotor” type engines in “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] Furthermore, the invention also applies to engines having different architectures, such as an architecture comprising a fan rotor comprising moving blades and a fan stator comprising fixed blades, or a single fan 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 rotor of the fan 4, 5 (or of the propeller) is called the axis X. The axial direction corresponds to the direction of the axis X and a radial direction is a direction perpendicular to this axis X and passing through it. Each blade 7 is rotatably mounted relative to the hub 6 around a respective setting axis Y: this setting axis Y extends in a generally radial direction relative to the axis X. Finally, internal (respectively, interior) and external (respectively, exterior), respectively, are used with reference to a radial direction so that the internal part or face of an element is closer to the axis X than the external part or face of the same element.

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

[0056] In [Fig. 1], each fan 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 comprises an actuating mechanism 8 for collectively modifying the pitch angle of the blades 7 of the rotors, in order to adapt the performance of the engine to the different flight phases. For this purpose, each blade 7 comprises an attachment part 9 (or blade hub) arranged at the blade root. The attachment part 9 is rotatably mounted relative to the hub 6 around a pitch axis Y. More precisely, the attachment part 9 is rotatably mounted inside a housing 10 formed in the hub 6, by means of balls 11 or other rolling elements.

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

[0059] The actuating mechanism 8 comprises for example an actuator 12 comprising a body 13 fixed to the hub 6 and a rod 14 capable of being driven in translation relative to the body 12. The actuating mechanism 8 further comprises an annular slide 15 mounted integral with the rod 14 and a pin 16 mounted integral with the attachment part 9. The pin 16 is capable of sliding in the slide 15 and of rotating relative to the slide 15, so as to convert a translational movement of the rod 14 into a rotational movement of the attachment part 9, and consequently a rotational movement of the blade 7 relative to the hub 6 around its setting axis Y.

[0060] The blade 7 comprises an aerodynamic profile structure 20 (or blade 20) suitable for being placed in an air flow when the engine 1 is operating in order to generate a 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 so as to define together a lower surface, an upper surface, a leading edge and a trailing edge of the blade 7. In a manner known per se, the leading edge is configured to extend opposite the flow of gases entering the engine 1. It corresponds to the front part of an aerodynamic profile which faces the air flow and which divides the air flow into an lower surface flow and an upper surface flow. The trailing edge corresponds to the rear part of the aerodynamic profile, where the lower and upper surface 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 a single piece according to a non-limiting embodiment.

[0063] The fibrous reinforcement may be formed from a single-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 (thermosetting, thermoplastic, or elastomeric) or a carbon matrix. For example, the matrix comprises a plastic material, typically a polymer, for example, epoxy, bismaleimide, or polyimide.

[0064] As visible in [Fig. 4], the spar 21 comprises a blade root portion 24 which extends outside the blade 20, a blade portion 25 which is arranged inside the blade 20, between the two skins 23 and a stilt portion 26 which extends 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, if necessary by means of an attachment part 9. The stilt portion 26 corresponds to the area of ​​the spar 21 which extends between the outlet of the hub 6 and the blade 20.

[0065] The spar 21 is advantageously made of metal and in a single piece: the blade root portion 24, the blade portion 25 and the stilt 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 manufacture of the metal spar 21 may involve several specific processes such as machining, forging, forming, casting or even additive manufacturing (3D printing).

[0066] In order to withstand 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 first extends radially by widening from a top of the body 27, gradually moving away from the pitch axis Y and then converging towards the pitch axis Y. The bulb 28 is therefore a closed structure which comprises a lower bulge 28a which extends from the main body 27 and an upper portion 28b which extends 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 general flared, swollen or curved 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 which extends from the stilt 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 aerodynamic profile structure 20 made of composite material. The connecting piece 22 is in contact with the blade 20.

[0070] The connecting piece 22 therefore entirely houses the spar 21. Thus, the assembly consisting of spar 21 and connecting piece 22 forms 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 comprise 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 junction with the profile 20 of the blade which is smooth.

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

[0074] In the latter case, the cavity provided to house a conventional spar is distinguished by the opening. The spar 21 is held by a 3D weave of the connecting piece 22 around the bulb 28 then inserted into the preform. In a conventional cavity, the bulb would not have a 3D holding weave around it because the cavity would be entirely open. on the 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 surface with the woven composite of the blade and a retention zone of a spherical shape (the upper part 28b of the bulb 28). Thus, if the blade 20 seems to want to escape by centrifugal force, the spar 21 will exert a counter force to retain it. In particular, during rotation of the fan, the centrifugal forces will “pull” the blades outwards. In counter force, the blades will exert a holding force inwards (if not ensured, this is a loss of blade).

[0077] Indeed, the geometry of the spar 21 having in particular this swollen shape in the lower part 28a makes it possible to retain on the one hand the connecting piece 22 around and to retain the skins 23 of the blade 20. Indeed, under the effect of the 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 straight, the forces are taken up on the retention slopes of the spar, limited in angle for insertion. The shape of the spar of the invention with a bulb makes it possible to have a complete counter-support to retain the forces created by the centrifugal force. The forces are taken up by the bulb 28 instead of being exerted on the contour of the connecting part 22, thus retaining the complete 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 less than the space between the skins 23 ensuring a minimum composite thickness. Of course, this is variable depending on the aerodynamic volume retained for the blade 20.

[0082] The blade root portion 24 is advantageously in the shape of a half-sphere.

[0083] The spar 21 may be hollow. Alternatively, only a portion of the spar 21 may be hollow and the remainder of the spar 21 may be solid (solid). According to yet another variant, the entire spar 21 is solid (solid). Example of 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 spar 21 is manufactured. Any conventional method can be used here, including machining, forging, forming, casting or even additive manufacturing (3D printing) for producing the spar 21.

[0086] During a step S2, a first fiber reinforcement of the blade 20 is produced. The first fiber reinforcement can be produced by three-dimensional weaving on a jacquard-type loom. During weaving, bundles of warp strands (or warp strands) are arranged in several layers. Weft strands T are interlaced with the warp strands C so as to bind the different layers of warp strands C together. The three-dimensional weaving can be an “interlock” weave. “Interlock” means a weaving weave in which each layer of weft strands binds several layers of warp strands with all the strands of the same weft column having the same movement in the plane of the weave.

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

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

[0089] Then, in a step S4, the spar 21 contained in the connecting piece 22 is inserted into the first fiber reinforcement so that the blade root portion 24 is located outside the first fiber reinforcement and the blade portion 25 is located inside the first fiber reinforcement.

[0090] In order to allow the insertion (step S4) of the spar 21 contained in the connecting piece 22 in the blade 20, a decoupling is carried out in the first fiber reinforcement.

[0091] According to a second embodiment, in a step S3' the second fiber reinforcement of the connecting piece 22 is directly formed in the first fiber reinforcement of the blade 20. Rather than providing a simple cavity, it is a matter of providing, here, a specific arrangement for the spar 21 in order to promote its retention. Unlike the first embodiment, here the connecting piece 22 is in one piece with the first fiber reinforcement of the blade 20.

[0092] Then, in a step S4', the spar 21 is inserted into the second fiber reinforcement so that the blade root portion 24 is located outside the first fiber reinforcement 23 and the blade portion 25 is located inside the first fiber reinforcement.

[0093] In a complementary manner, the first and second fiber 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] Whatever the first or second embodiment, during a step S5, the assembly thus obtained, formed of the spar 21, the first fiber reinforcement and the connecting piece 22 is placed in a mold having a cavity having the shape of 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 fiber reinforcement and the second fiber reinforcement. The injection of plastic material can be carried out by an injection technique of the RTM or VARRTM type. 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 manner known per se, the plastic material is heated so as to cause polymerization of the plastic material, for example by crosslinking. For this purpose, the mold is placed in an oven. The part obtained is then demolded and then, optionally, machined to remove excess length and obtain a part having the desired shape, despite possible shrinkage of the fibers of the fibrous reinforcement during the polymerization of the plastic material.

[0097] Then, during a step S6, an attachment part 9 may, if necessary, be added and fixed to the root of the blade 7, around the blade root portion 24 of the spar 21. It may in particular be obtained by machining in order to form the cavity whose shape and dimensions correspond to those of the blade root portion 24. Optionally, the attachment part 9 may be made in two parts so that it can be added and fixed around the blade root portion 24 using two dedicated rings, for example by shrinking, screwing, welding or even using a clamp. Step S6 of fixing the attachment part 9 may therefore be carried out before or after the injection (step S5). Advantageously, the material constituting the attachment part 9 may be different from that of the spar 21.

Claims

Claims

1. A blade (7) of a turbomachine, comprising: - an aerodynamic profile structure (20) comprising two facing skins (23), the skins (23) comprising at least one fiber 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 stilt 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 stilt portion (26) beyond the blade portion (25), the connecting piece (22) being integral with the spar (21), the connecting piece (22) containing the spar (21) being arranged inside the aerodynamic profile structure (20) between the two skins (23).;

2. A blade (7) according to claim 1, wherein the body (27) is cylindrical in shape, the bulb (28) having a lower portion (28a) which flares out as it extends radially from the body (27).

3. A blade (7) according to claim 2, wherein the bulb (28) comprises an upper portion (28b) surmounting the lower portion (28a), the upper portion being configured to provide a continuous retention zone with the airfoil structure (20).

4. Blade (7) according to one of claims 1 to 3, in which the bulb (28) is spherical or in the shape of a spherical ellipse.

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

6. Blade (7) according to one of claims 1 to 5, in which the spar (21) is metallic.

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

8. Blade (7) according to one of claims 1 to 6, in which the connecting piece (22) is attached to the aerodynamic profile structure (20).

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

10.

11. Engine (1) comprising a fan (3) according to claim 9.Method for manufacturing a blade (7) according to one of claims 1 to 8, comprising the following steps: S1: producing the spar (21); S2: producing a first fiber reinforcement of the aerodynamic profile structure (20), for example by a first three-dimensional weave; S3: producing a second fiber 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 fiber reinforcement so that the blade root portion (24) is located outside the first fiber reinforcement (23) and the blade portion (25) is located inside the first fiber reinforcement (23); S5: placement of the assembly formed by the first fiber reinforcement (23), the second fiber 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. Method for manufacturing a blade (7) according to one of claims 1 to 8, comprising the following steps: S1: production of the spar (21); S2: production of a first fiber reinforcement of the aerodynamic profile structure (20), for example by a first three-dimensional weave; S3': production of a second fiber reinforcement of the connecting piece (22) in the first fiber reinforcement, for example by a second three-dimensional weave different from the first three-dimensional weave; S4': insertion of the spar (21) in the second fiber reinforcement so that the blade root portion (24) is located outside the first fiber reinforcement (23) and the blade portion (25) is located inside the second fiber reinforcement (23); S5: placement of the assembly formed by the first fiber reinforcement (23), the second fiber 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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