Blade made of composite material comprising a fibrous structure

Abstract

The invention relates to a turbine blade for a turbomachine comprising: - a composite material structure (20) including a blade root (22) and a blade (24) with an aerodynamic profile, and - a sleeve (34) comprising a wall (36) extending around a longitudinal axis (Y) and having an external surface (38) configured to cooperate with a variable pitch mechanism of a turbomachine, and an internal surface (40) defining a recess (42) in which the blade root (22) is housed, the composite material structure (20) being disposed against the internal surface (40) and the longitudinal fibers (30) being arranged substantially parallel to the longitudinal axis (Y) in the central portion (44) and radiating away from the longitudinal axis (Y) in the end portion (46). Figure for the abstract: Fig. 4a

Description

Title of the invention: Blade made of composite material comprising a fibrous structure. Field of the invention

[0001] The invention relates generally to the field of turbomachinery, and in particular to turbomachine blades.

[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 having two rotating propellers or an "Unducted Single Fan" type engine having one moving blade and one fixed blade, or a turboprop engine having a single-propeller architecture). Technological background

[0003] The advantage of engines with unshod fans is that the fan diameter is not limited by the presence of a shroud, making it possible to design an engine with a high bypass ratio (known as the "By Pass Ratio" or BPR), and consequently reduced fuel consumption. Thus, in this type of engine, the fan blades can have a large span.

[0004] 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.

[0005] However, the design of such blades requires taking into account opposing constraints.

[0006] On the one hand, the sizing of these blades must allow for optimal aerodynamic performance, in particular maximizing efficiency and providing thrust while minimizing losses. Improving the aerodynamic performance of the fan tends towards an increase in the bypass ratio, which translates into an increase in the external diameter, and therefore the span, of these blades.

[0007] 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.

[0008] Furthermore, on unshod fan designs, engine starting is generally performed with a very open timing setting. Indeed, a very open timing setting allows power to be consumed by torque, which ensures machine safety by guaranteeing low fan speeds.

[0009] However, with a very open pitch, the blades undergo a turbulent, completely separated aerodynamic flow, which generates a broadband vibratory excitation. In In particular, on wide-chord and large-span blades, the bending force is intense, although the engine speed is not at its maximum.

[0010] In normal operation, namely during ground and flight phases, the fan pitch is adjusted so that the pitch angle is more closed. The aerodynamic flow is then perfectly smooth, particularly when aligned with the airfoil. Broadband stresses disappear because the rotational speed is higher, and the bending force is controlled. However, since the engine is not enclosed in a cowling, the angle of attack seen by the various fan blades, depending on their angular position, varies according to the aircraft's angle of attack, creating a cyclic bending moment (commonly called the IP moment) on the blades. This cyclic bending moment then generates strong bending stresses on the blades in addition to the centrifugal forces due to their rotation.

[0011] These blades can be made of metallic material, giving them good mechanical strength. However, such blades have the disadvantage of having a relatively large mass.

[0012] 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.

[0013] To overcome these drawbacks, various solutions exist in the prior art. Most use reinforcing elements, particularly at the blade root, and add various structural elements to allow, for example, the blade to be attached to the leveling mechanism. Patent documents WO2022 / 018353 and WO2022 / 208002 describe the addition of reinforcing and structural elements, particularly at the blade roots.

[0014] However, these solutions have the disadvantage of requiring the manufacture of several elements in potentially different materials and the assembly of these elements using fastening means. Such blades can therefore be relatively time-consuming to manufacture. Description of the invention

[0015] One of the aims of the invention is therefore to provide a blade adapted for use with a variable pitch mechanism and in an "Open Rotor" type environment, while being able to withstand intense aerodynamic forces, under the constraint of limited size and minimum mass. Furthermore, the blade The proposed design should preferably include a limited number of structural elements and be quick to manufacture.

[0016] To this end, according to a first aspect of the invention, a blade for a turbomachine comprising is proposed:

[0017] - a composite material structure comprising a blade root and a profile blade aerodynamic extending from the blade root, the composite material structure comprising a fibrous reinforcement obtained by three-dimensional weaving of strands, the fibrous reinforcement having a blade root portion extending into the blade root and a blade portion extending into the aerodynamically profiled blade, the strands comprising longitudinal fibers extending continuously inside the blade root and inside the aerodynamically profiled blade, and a first metallic matrix in which the blade root portion of the fibrous reinforcement is embedded, and - a sleeve comprising: a wall extending around a longitudinal axis and having an external surface configured to cooperate with a variable stalling mechanism of a turbomachine, and an internal surface delimiting a through recess formed in the sleeve and in which the blade foot is housed, the recess comprising a central part having a first diameter dl measured radially with respect to the longitudinal axis, and an end part, located with respect to the central part opposite the aerodynamically profiled blade, and having a second diameter measured radially with respect to the longitudinal axis, the second diameter being greater than the first diameter; the composite material structure being disposed against the internal surface and the longitudinal fibers being arranged substantially parallel to the longitudinal axis in the central part and radiating away from the longitudinal axis in the end part.

[0018] The blade can thus withstand intense aerodynamic forces while having a limited size. Furthermore, the blade is formed by a minimal number of elements, allowing it to have a minimal mass and be quick to manufacture.

[0019] The longitudinal fibers, radiating outwards from the longitudinal axis in the end portion, allow for a widening of the fibrous reinforcement in the end portion relative to the central portion, in a manner complementary to the shape of the internal surface. Since the longitudinal fibers are embedded in a metallic matrix, their configuration is fixed, preventing the composite material structure from separating from the sleeve under the effect of centrifugal force during the rotation of the blower of which the blade may be a part. It is therefore unnecessary to use fastening means to attach the blade root to the sleeve, thus avoiding the creation of weak points on the blade root.

[0020] The metal matrix may comprise titanium, aluminum, nickel, iron, or one of their alloys. Preferably, the metal matrix is ​​titanium.

[0021] The sleeve is preferably metallic so that it can be precisely machined and thus cooperate optimally with a variable shimming mechanism. The sleeve may therefore comprise titanium, aluminum, nickel, iron, or one of their alloys. The sleeve is preferably made of titanium.

[0022] According to embodiments that can be taken alone or in combination, the blade may further have the following characteristics: - in the end part of the sleeve, the fibrous reinforcement includes a debonding on either side of which longitudinal fibers extend, the debonding forming a fiber-free zone in the center of the fibrous reinforcement; all the longitudinal fibers of the end part are thus positioned in a peripheral zone of the blade foot so as to leave a central fiber-free zone, this central zone being able to be empty or on the contrary filled with a material; the number of fibers is the same from one end to the other of the debonding zone; - the first diameter dl and the second diameter d2 are such that d2 / dl > 1.10, preferably > 1.20; the spacing of the fibers in the end part thus prevents the composite material structure from being torn away and separating from the sleeve during the operation of the blower of which the blade is a part; - the number of longitudinal fibers in an inlet portion of the central part is greater than the number of longitudinal fibers in the end portion; the inlet portion of the central part is in particular a portion in which only the fibrous reinforcement and the metallic matrix in which it is embedded are inserted; - the longitudinal fibers include central longitudinal fibers which extend into the inlet portion of the central part of the recess and are interrupted to leave the fiber-free zone, and peripheral longitudinal fibers which conform to the shape of the internal surface in the central part and in the end part of the recess; the number of peripheral longitudinal fibers is the same from the inlet portion to the end part of the sleeve; - the blade includes an insert housed in the fiber-free zone; the insert contributes in particular to pressing the longitudinal fibers of the end portion against the inner wall of the sleeve; the insert may be a metallic part, preferably formed from the same metal as the metallic matrix; the insert may be a hollow part so as to lighten the blade root; the insert may extend only in the end portion or may extend in the end portion and in the central portion; preferably, the insert does not extend into the inlet portion of the central portion; the number of peripheral longitudinal fibers is identical along the insert; - in the end part of the recess, the longitudinal fibers each have a portion which is located outside a cylindrical surface of revolution having the longitudinal axis as its axis and the first diameter as its diameter; thus, all the longitudinal fibers of the end part are separated radially with respect to the central part and contribute to keeping the blade inside the sleeve despite the centrifugal force which is exerted on the composite material structure during the operation of the blower of which the blade is a part; - the internal surface of the sleeve has a shape of revolution, defined by a curved generatrix with the longitudinal axis as its axis of revolution, and in which the first diameter is the smallest diameter of the shape of revolution and the second diameter is the largest diameter of the shape of revolution in the end part of the recess; thus, the internal wall gradually flares out towards the end part and the fibers also gradually move radially away from the longitudinal axis; thus, the longitudinal fibers do not have any folds or angled areas that could weaken them; and - the peripheral longitudinal fibers spread out radially in a progressive manner from a first radial plane in which the recess has the first diameter dl to a second radial plane in which the recess has the second diameter d2.

[0023] According to a second aspect, the invention proposes a method for manufacturing a blade as previously described, said method comprising:

[0024] - a step El of inserting the fibrous reinforcement into the recess of the sleeve, - a step E2 of inserting an insert into the recess so as to maintain the longitudinal fibers between the insert and the internal surface of the sleeve; and - an E3 step of injecting a first metallic composition inside the recess so as to form a metallic matrix in which the fibers of the blade foot portion of the fibrous reinforcement are embedded.

[0025] This process allows the rapid manufacture of a blade, using few parts and without the use of fastening parts and / or tools.

[0026] The fibrous reinforcement is notably inserted into the recess of the sleeve by distributing the longitudinal fibers against the inner surface of the wall. The insert is then inserted into the recess, and in particular in such a way as to distribute the longitudinal fibers evenly around the sleeve and against the inner surface.

[0027] Preferably, the insert is generally cylindrical in shape and has a flared base so as to press a first portion of the longitudinal fibers against the central part of the sleeve and an end portion against the end part of the sleeve. In the end part of the sleeve, the longitudinal fibers are thus radially offset from the longitudinal axis of the sleeve by means of the insert and its shape substantially complementary to the shape of the internal surface.

[0028] According to one embodiment, the insert may extend only in the end part and have a substantially conical shape of revolution.

[0029] Once the insert is introduced into the sleeve so as to wedge the longitudinal fibers between the insert and the inner surface of the sleeve, a metallic composition is injected between the inner wall of the sleeve and the insert to form the metallic matrix surrounding the longitudinal fibers.

[0030] Preferably, step E3 is carried out by overmolding by introducing the assembly which is formed by the sleeve, the fibrous reinforcement and the insert into a mold and then injecting the metallic composition which then flows between the internal surface of the sleeve and the insert.

[0031] According to one possible embodiment, all the fibrous reinforcement can be embedded in the metallic matrix.

[0032] According to a preferred embodiment, only the blade root portion of the fibrous reinforcement is embedded in the metallic matrix to form the blade root. The blade portion can then be embedded in a lighter matrix such as an organic matrix, and for example a resin.

[0033] In this way, the blade foot comprising a metallic matrix is ​​securely inserted into the sleeve and the blade is strong and resistant while being lightweight.

[0034] According to embodiments that can be taken alone or in combination, the process may further have the following characteristics: - the insert is inserted into a space formed between the longitudinal fibers by a debonding in the fibrous reinforcement, so as to distribute the longitudinal fibers regularly around the insert; - the process further includes a machining step of the insert so as to form a cavity in the fiber-free space of the end part.

[0035] Optionally, the method may further include a machining step of all or part of the insert so that the blade root is not too heavy. Since all the fibers are positioned around the insert and embedded in the metal matrix, machining the insert does not damage the fibers and does not reduce the strength of the blade root.

[0036] The invention also proposes, according to a third aspect, a gas turbine engine comprising a blower, the blower comprising a hub and blades extending radially from the hub, at least one of the blades being as previously described or manufactured as previously described.

[0037] According to a fourth aspect, the invention also proposes an aircraft comprising a fuselage and further comprising at least one gas turbine engine conforming to the third aspect, said engine being attached to the fuselage. Brief description of the Figures

[0038] Other features and advantages of the invention will become apparent from the following description, given solely by way of example and with reference to the accompanying drawings, in which:

[0039] - Fig. 1 is a schematic perspective view of a gas turbine engine according to an embodiment of the invention; - [Fig.2] is a schematic longitudinal cross-sectional view of a blade according to one embodiment of the invention;

[0040] - [Fig. 3] is a schematic top view of an aircraft according to a mode of realization of the invention;

[0041] - [Fig. 4a] is a schematic longitudinal cross-sectional view of a blade along a method of implementing the invention;

[0042] - [Fig.4b] is a schematic cross-sectional view of the foot of the blade of [Fig.4a];

[0043] - [Fig. 5] is a schematic cross-sectional view of the blade of the turbine blade [Fig. 4a] ; and - [Fig.6] is a flowchart of a manufacturing process for the blade of [Fig.4a] according to an embodiment of the invention. Detailed description of an example of implementation

[0044] In [Fig.1], the motor 1 shown is an "Open Rotor" type motor, in "puller" configuration (i.e. the blower is placed upstream of the power generator with an air inlet located before, between or just behind the two blower rotors).

[0045] The engine comprises a nacelle 2 intended to be fixed to an aircraft fuselage, and an unfaired fan 3. The fan 3 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 around the same axis of rotation X (which coincides with a principal axis of the engine), in opposite directions.

[0046] In the example illustrated in [Fig. 1], the motor 1 is an "Open Rotor" type motor, in a "puller" 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 configuration commonly referred to as "pusher" (i.e., the fan is placed at the rear of the power generator with an air inlet located on the side).

[0047] 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.

[0048] The invention is applicable to turboprop type architectures (comprising a single fan rotor).

[0049] In [Fig. 1], each blower rotor 4, 5 comprises a hub 6 mounted rotatably relative to the nacelle 2 and a plurality of blades 7 according to an embodiment of the invention, said blades being fixed to the hub 6. The blades 7 extend substantially radially relative to the axis of rotation X of the hub.

[0050] As illustrated in [Fig. 2], the fan 3 further comprises an actuation mechanism 8 for collectively adjusting the pitch angle of the rotor blades to adapt engine performance to different flight phases. For this purpose, each blade 7 comprises a blade root 22 and a blade 24 with an aerodynamic profile. The blade root 22 is rotatably mounted relative to the hub 6 about a pitch axis Y. More specifically, the blade root 22 is rotatably mounted within a mounting device 10 formed in the hub 6, by means of balls 11 or other rolling elements.

[0051] The blade 7 has a blade root 22 and a blade 24 with an aerodynamic profile extending opposite the blade root 22. The aerodynamic blade 24 is designed to extend into an air stream of the engine, when the engine 1 is running, in order to generate lift. Conversely, the blade root 22 is designed to extend out of the air stream.

[0052] As illustrated in [Fig. 3], the engine 1 as described with reference to Figures 1 and 2 can be attached to the fuselage of an aircraft 19. The aircraft 19 has a fuselage 18 comprising two wings 17 and a tail assembly 18'. The aircraft 19 has two engines 1, each being attached under a wing 17 of the aircraft 19.

[0053] According to another possible configuration, two motors 1 can be fixed under each wing 17.

[0054] According to an embodiment of the invention described with reference to Figures 4a and 4b, the blade 7 comprises a composite material structure 20 including the blade foot 22 and the aerodynamically profiled blade 24 extending from the blade foot 22. The composite material structure 20 includes a fibrous reinforcement obtained by three-dimensional weaving of strands, the fibrous reinforcement having a portion of the blade foot 26 extending into the blade foot 22 and a portion of the blade 28 extending into the aerodynamically profiled blade 24.

[0055] The strands comprise longitudinal fibers 30 extending continuously inside the blade foot 22 and inside the airfoil blade 24. The composite material structure 20 further comprises a first metallic matrix 32 in which the blade root portion 26 of the fibrous reinforcement is embedded.

[0056] Moreover, the blade 7 comprises a sleeve 34 which has a wall 36 extending around the longitudinal axis Y and having an external surface 38 configured to cooperate with a variable pitching mechanism of a turbomachine and an internal surface 40 defining a through recess 42 formed in the sleeve 34.

[0057] The blade foot 22 is housed in the recess 42 which comprises a central part 44 having a first diameter dl measured radially with respect to the longitudinal axis Y, and an end part 46, located with respect to the central part 44 opposite the aerodynamically profiled blade 24, and having a second diameter d2 measured radially with respect to the longitudinal axis Y. The second diameter d2 is greater than the first diameter dl and the internal wall 40 is thus narrowed in the central part 44 and flared in the end part 46.

[0058] The composite material structure 20 is disposed against the internal surface 40 and the longitudinal fibers 30 are arranged substantially parallel to the longitudinal axis Y in the central part 44 and radiate away from the longitudinal axis Y in the end part 46 following the flared shape of the internal wall 40.

[0059] Thus, the blade 7 can advantageously withstand intense aerodynamic forces while having a limited size. Furthermore, the blade is formed with few elements, which allows it to have a minimal mass and to be manufactured quickly.

[0060] The longitudinal fibers 30, extending radially from the longitudinal axis Y in the end portion 46, allow for a widening of the fibrous reinforcement in the end portion 46 relative to the central portion 44, in a manner complementary to the shape of the internal surface 40. Since the longitudinal fibers 30 are embedded in a metallic matrix 32, their configuration is fixed, which prevents the composite material structure 20 from detaching from the sleeve 34 under the effect of centrifugal force during the rotation of the blower 3, of which the blade 7 may be a part. It is therefore unnecessary to use fastening means to attach the blade root 22 to the sleeve 34, which simplifies the manufacturing process of the blade 7 and avoids creating weak points on the blade root 22.

[0061] The fibrous reinforcement is narrowed along a direction D perpendicular to the longitudinal axis Y so that the longitudinal fibers are compacted to fit into the sleeve 34. In particular, the fibrous reinforcement has a third diameter d3 measured in the foot portion 26 located outside the sleeve 34 and radially with respect to the longitudinal axis Y. This diameter d3 is such that 1.50 > d3 / dl > 1.05, preferably 1.30 > d3 / dl > 1.05. In this way, the longitudinal fibers 30 are compacted radially and thus brought closer to the longitudinal axis Y to be inserted into the sleeve 34, and in particular in the central part 44, then radially separated from the longitudinal axis Y in the end part 46.

[0062] In this embodiment, the metal matrix 32 is made of titanium and the sleeve 34 is also made of titanium and is monolithic. The titanium may be a titanium alloy. However, the metal matrix 32 and the sleeve 34 are not necessarily formed from the same metal and may each be formed from a metal other than titanium or a titanium alloy, such as aluminum, nickel, iron, or one of their alloys.

[0063] Since the sleeve 34 is made of metal, it has good mechanical properties. Furthermore, it can be precisely machined to have the desired shape and, in particular, to have an outer surface 38 that cooperates with the actuation mechanism 8 in an optimized manner.

[0064] In the end portion 46, the fibrous reinforcement includes a debonding on either side of which longitudinal fibers 30 extend. This debonding forms a fiber-free zone 48 in the center of the fibrous structure. This debonding facilitates the radial separation of the longitudinal fibers 30 in the end portion 46 so that the fibers are pressed against the internal surface 40.

[0065] The fiber-free zone 48 may in particular consist of a void, or be filled with a metallic matrix or a solid part.

[0066] As illustrated in [Fig. 5], the fibrous reinforcement comprises two skins 50, which are connected to each other and extend generally opposite each other. The skins 50 are shaped to define together an intrados I, an extrados E, a leading edge 52, and a trailing edge 52'. As is known per se, the leading edge 52 is configured to extend opposite the flow of gases entering the turbomachine. It corresponds to the forward part of an airfoil that faces the airflow and divides the airflow into an intrados flow I and an extrados flow E. The trailing edge 52', for its part, corresponds to the rear part of the airfoil, where the intrados and extrados flows meet.

[0067] The skins 50 of the aerodynamically profiled blade 24 are made of a composite material comprising fibrous reinforcement densified by a matrix. They are therefore monolithic and are made in one piece according to a non-limiting embodiment.

[0068] In the portion of the blade foot 26 of the fibrous reinforcement, the matrix 32 is, as previously described, metallic.

[0069] In the blade portion 28 of the fibrous reinforcement, the matrix may be metallic or organic. Preferably, the matrix of the blade portion 28 comprises an organic material (thermosetting, thermoplastic, or elastomer) or is a matrix made of carbon. For example, the matrix may include a plastic material, typically a polymer, such as epoxy, bismaleimide, or polyimide. The fibers of the fibrous reinforcement include at least one of the following materials: carbon, glass, aramid, polypropylene, and / or ceramic.

[0070] The fibrous reinforcement comprises longitudinal fibers 30 and also transverse fibers not shown in the figures.

[0071] The fibrous reinforcement has a free end 58 which forms the free end of the blade portion 28 and is positioned opposite the foot portion 26. The fibrous reinforcement also has a foot end 60 which is positioned opposite the free end 58. The longitudinal fibers 30 passing through the foot portion 26, called inner longitudinal fibers 30', extend from the foot end 60 to the free end 58. Thus, even though the foot portion 26 and the blade portion 28 comprise a different matrix, in particular a metal matrix for the foot portion 26 and an organic matrix for the blade portion 28, the inner longitudinal fibers 30' allow continuity between the foot portion 26 and the blade portion 28 and contribute to the strength of the blade 7.

[0072] The blade portion 28 may also include one or two cavities, preferably two cavities 54, each accommodating a conformation piece 56. The cavities 54 are formed by debonding in the weave. Each conformation piece 56 is formed from a rigid and lightweight material so as to reduce the mass of the aerodynamically profiled blade while allowing it to retain its aerodynamic shape.

[0073] The rigid material forming the conforming part(s) 56 is preferably honeycomb-shaped, for example a foam, and formed, for example, from pre-machined polymethacrylimide (PMI). Alternatively, the rigid honeycomb material may be a pre-sealed aluminum honeycomb material.

[0074] The shaping piece(s) 56 allows the desired thickness and shape to be given to the aerodynamic profile blade 24 of the blade 7, while using a lighter material than other elements of the blade.

[0075] However, according to one possible embodiment, the cavities may remain empty and not be filled by filler pieces.

[0076] The first diameter dl and the second diameter d2 are such that d2 / dl > 1.10, preferably > 1.20. Such a ratio allows the longitudinal fibers 30 to be sufficiently spread radially in the end part 46 with respect to the central part 44. In this way, the composite material structure 20 is held securely inside the sleeve 34, and is not at risk of separating from the sleeve 34 under the effect of the centrifugal force experienced by the composite material structure during the rotation of the blower.

[0077] Preferably, the first diameter dl is the smallest diameter of the central part 44 and the second diameter d2 is the largest diameter of the end part 46.

[0078] Preferably, in the end portion 46 of the recess 42, the longitudinal fibers 30 each have a retaining portion 31 which is located outside a cylindrical surface of revolution C having the longitudinal axis Y as its axis and the first diameter dl as its diameter. In this way, in the end portion 46, at least a certain portion of each longitudinal fiber 30 is radially displaced beyond the diameter dl and contributes to retaining the composite structure 20 in the recess 42.

[0079] The radial separation of the internal surface 40 from the central part 44 to form the end part 46 allows to form a stop 64 against which the retaining portion 31 of each longitudinal fiber 30 is pressed.

[0080] Preferably, the end portion 46 has a constant diameter section 46' having a diameter equal to the second diameter d2 and a height h. The constant diameter section 46' is positioned at the foot end 60. In this constant diameter section 46', the retaining portions 31 of the longitudinal fibers 30 are stacked along the longitudinal axis to a height h. This stacking, shown in [Fig. 4b], reinforces the retention of the composite structure 20 in the recess 42 of the sleeve 34.

[0081] In particular, during the rotation of the blower 4, a centrifugal force F is exerted on the composite material structure 20. Indeed, when the blower is rotating, the blade 7 is subjected to centrifugal forces oriented in a radial direction with respect to the axis of rotation of the blower, which tend to separate the composite material structure 20 from the sleeve 34. Under the effect of this force F, the stack of the retaining portions 31 is pushed against the stop 64, which contributes to maintaining the composite material structure 20 in the recess 42 of the sleeve 34.

[0082] The number of longitudinal fibers 30 in the central part 44 is the same as in the end part 46. By spreading out radially in the end part 46, the longitudinal fibers thus form the fiber-free zone 48.

[0083] According to one possible embodiment shown in [Fig. 4b], the central portion 44 may include an inlet portion 70 comprising only longitudinal fibers and the metallic matrix in which they are embedded. The insert 49 does not extend into this inlet portion 70. The number of longitudinal fibers is then greater in this inlet portion 70 than the number of fibers present in the sleeve portion in which the insert 49 is positioned. Some longitudinal fibers, called peripheral longitudinal fibers, then extend into the inlet portion as far as the end portion, bypassing the insert 49, and others fibers, called central longitudinal fibers, extend only in the entry portion 70 and stop to form the fiber-free zone that accommodates the insert.

[0084] According to one possible embodiment, an insert 49 can be housed in the fiber-free area 48. The insert 49 allows the longitudinal fibers 30 to be pressed and held against the internal surface 40. The insert 49 preferably has a shape complementary to the internal surface 40 of the sleeve 34.

[0085] The insert 49, for example, has a substantially cylindrical body 58 extending into the central portion 44 and a flared base 60 extending from the cylindrical body 58 into the end portion 46. The insert 49 may also have a conical or rounded insertion end 62 positioned opposite the flared base 60 with respect to the cylindrical body 58. This insertion end 62 facilitates the insertion of the insert 49 into the unbonding zone of the fibrous reinforcement during the blade manufacturing process and also allows the fibers to be progressively separated towards the inner surface 40 of the sleeve 34.

[0086] Preferably, the internal surface 40 of the sleeve 34 has a shape of revolution, defined by a curved generatrix and having the longitudinal axis as the axis of revolution, and in which the first diameter dl is the smallest diameter of the shape of revolution and the second diameter d2 is the largest diameter of the shape of revolution in the end part 46 of the recess 42.

[0087] In this way, the stop 64 is rounded and the longitudinal fibers 30 move radially away from the longitudinal axis Y in a progressive manner, thus avoiding any weakening or breakage of the longitudinal fibers 30 in the end part 46.

[0088] In other words, the peripheral longitudinal fibers 30 spread out radially in a progressive manner from a first radial plane PI in which the recess 42 has the first diameter dl to a second radial plane P2 in which the recess 42 has the second diameter d2. Blade manufacturing process

[0089] With reference to [Fig. 6], a manufacturing process 70 for a blade 7 comprises a step 11 of inserting the fibrous reinforcement into the recess of the sleeve 34. The fibrous reinforcement is notably produced by three-dimensional weaving forming a bond on either side of which longitudinal fibers 30 extend, the bond being formed in the blade root portion 26 of the fibrous reinforcement. Furthermore, the weaving is carried out so as to form the two cavities 54 into which shaping pieces 56 are inserted.

[0090] The method also includes a step E2 of inserting the insert 49 into the recess 42 so as to maintain the longitudinal fibers 30 between the insert 49 and the inner surface 40 of the sleeve 34. In particular, the insert 49 is positioned in the unbinding of the fibrous reinforcement so as to distribute, preferably regularly, the longitudinal fibers 30 around the insert 49 and against the internal surface 40.

[0091] The insert 49 allows the longitudinal fibers 30 pressed against the internal surface 40 to be wedged, both in the central part 44 and also in the end part 46.

[0092] A step E3 of injecting a first metallic composition is then carried out. This step consists of injecting the first metallic composition inside the recess 42 so as to form the metallic matrix in which the fibers of the blade foot portion 26 of the fibrous reinforcement are embedded.

[0093] Step E3 is carried out after insertion into a mold of the assembly formed by the fibrous reinforcement, the sleeve 34 and the insert 49 to obtain a preform with an aerodynamic profile.

[0094] During this injection step E3, the metallic composition impregnates the entire fibrous reinforcement and thus inserts itself in particular between the insert 49 and the internal surface 40 of the sleeve 34.

[0095] When the sleeve 34 and the metal matrix 32 are formed of a different metal, the metal matrix preferably has a lower melting point than the metal or alloy forming the sleeve 34 so that the sleeve 34 does not melt during the injection of the metal composition between the sleeve 34 and the insert 49.

[0096] Once the injected metallic composition has solidified to form the metallic matrix 32, the composite material structure 20 and the sleeve 32 are mechanically inseparable.

[0097] When the sleeve 34 and the metal matrix 32 are formed with the same metal or the same alloy, chemical adhesion by molecular contact occurs at the interface between the sleeve 34 and the metal matrix 32. In this way, the retention of the composite material structure in the sleeve is reinforced.

[0098] In the case where the sleeve 34 and the metal matrix 32 are formed with different metals or alloys, for example steel with a melting point of 1500°C for the sleeve and aluminium with a melting point of 650°C for the sleeve, adhesion occurs by thermal shrinkage during the cooling of the metal matrix.

[0099] It is also possible to form the sleeve 34 and the metal matrix 32 with different metals or alloys but having similar melting temperatures, for example a nickel-based alloy for the sleeve 34 and titanium for the metal matrix 32. In this case, when the liquid metal matrix 32 is injected into the sleeve 34, the liquid titanium can cause the nickel alloy to melt at the interface, resulting in adhesion between the sleeve 34 and the metal matrix 32.

[0100] Preferably, the metallic composition is injected only into the blade foot portion 26 of the fibrous reinforcement.

[0101] A second injection step E4 can then be carried out, consisting of injecting an organic composition, for example a liquid resin, into the mold according to the RTM process to embed the fibers of the blade portion and obtain the blade 7 shown in [Fig. 4a]. The resin can be, in particular, an epoxy resin, a thermoplastic resin, or a polybismaleimide (BMI) resin.

[0102] The blade 7 thus formed may have a radial height, measured between the foot end 60 and the free end 58, ranging from 1500 millimeters (mm) to 21000 and preferably between 1650 and 1950 mm. The diameter of the blower 3 may then be less than or equal to 6 meters (m), and in particular between 3 m and 5 m, preferably between 3.5 m and 4.5 m.

[0103] Engine 1 thus has a high dilution ratio and consequently reduced fuel consumption.

Claims

Demands

1. Blade (7) for a turbomachine comprising: - a composite material structure (20) comprising a blade root (22) and a blade (24) with an aerodynamic profile extending from the blade root (22), the composite material structure (20) comprising a fibrous reinforcement obtained by three-dimensional weaving of strands, the fibrous reinforcement having a portion of the blade root (26) extending into the blade root (22) and a portion of the blade (28) extending into the aerodynamically profiled blade (24), the strands comprising longitudinal fibers (30) extending continuously inside the blade root (22) and inside the aerodynamically profiled blade (24), and a first metallic matrix (32) in which the portion of the blade root (26) of the fibrous reinforcement is embedded, and - a sleeve (34) comprising: a wall (36) extending around a longitudinal axis (Y) and having an external surface (38) configured to cooperate with a variable pitching mechanism of a turbomachine, and an internal surface (40) delimiting a through recess (42) formed in the sleeve (34) and in which the blade foot (22) is housed, the recess (42) comprising a central part (44) having a first diameter dl measured radially with respect to the longitudinal axis (Y), and an end part (46), located with respect to the central part (44) opposite the aerodynamically profiled blade (24), and having a second diameter d2 measured radially with respect to the longitudinal axis (Y), the second diameter d2 being greater than the first diameter dl; the composite material structure (20) being disposed against the internal surface (40) and the longitudinal fibers (30) being disposed substantially parallel to the longitudinal axis (Y) in the central part (44) and radiating away from the longitudinal axis (Y) in the end part (46).

2. Blade according to claim 1, wherein, in the end part (46) of the sleeve (34), the fibrous reinforcement comprises a debonding on either side of which longitudinal fibers (30) extend, the debonding forming a fiber-free zone (48) provided in the center of the fibrous reinforcement.

3. Blade (7) according to claim 1 or 2, wherein the first diameter dl and the second diameter d2 are such that d2 / dl > 1.10, preferably > 1.20

4. Blade (7) according to claim 2 or 3, comprising an insert (49) housed in the fiber-free area (48).

5. Blade (7) according to any one of the preceding claims, wherein in the end part (46) of the recess (42), the longitudinal fibers (30) each have a retaining portion (31) which is located outside a cylindrical surface of revolution (C) having as its axis the longitudinal axis (Y) and as its diameter the first diameter dl.

6. Blade (7) according to any one of the preceding claims, wherein the internal surface (40) of the sleeve (34) has a shape of revolution, defined by a curved generatrix and having the longitudinal axis (Y) as its axis of revolution, and wherein the first diameter dl is the smallest diameter of the shape of revolution and the second diameter d2 is the largest diameter of the shape of revolution in the end part (46) of the recess (42).

7. Blade according to claim 6, wherein the longitudinal fibers (30) spread out radially in a progressive manner from a first radial plane (PI) in which the recess (42) has the first diameter d1 to a second radial plane (P2) in which the recess (42) has the second diameter d2.

8. A method for manufacturing a blade according to any one of claims 1 to 7, comprising: - a step E1 of inserting the fibrous reinforcement into the recess (42) of the sleeve (34), - a step E2 of inserting an insert (49) into the recess (42) so as to maintain the longitudinal fibers (30) between the insert (49) and the internal surface (40) of the sleeve (34); and - a step E3 of injecting a first metallic composition into the recess (42) so as to form a metallic matrix in which the fibers of the blade foot portion (26) of the fibrous reinforcement are embedded.

9. A manufacturing method according to claim 8 when it depends on claim 2, wherein the insert (49) is inserted into a space formed between the longitudinal fibers by the unbinding, so that distribute the longitudinal fibers (30) evenly around the insert (49).

10. A manufacturing method according to claim 8 when it depends on claim 2 or according to claim 9, further comprising a machining step of the insert (49) so as to form a cavity in the fiber-free space of the end portion (46).

11. Gas turbine engine (1) comprising a blower (3), the blower (3) comprising a hub (6) and blades (7) extending radially from the hub (6), at least one of the blades (7) conforming to any one of claims 1 to 7, or being manufactured by means of the method according to claim 8 to 10.

12. Aircraft (19) comprising a fuselage and further comprising at least one gas turbine engine (1) conforming to claim 11, said engine (1) being attached to the fuselage.