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 unshrouded 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] The forces and stresses exerted on the blades can lead to their breakage, which, in the case of an unfaired engine, can cause the blade to detach and then strike and damage the aircraft or fall and cause damage on the ground. Various manufacturing materials have therefore been used to obtain blades with sufficient strength and prevent any blade detachment.

[0012] The blades can, for example, be made of metallic material, giving them good mechanical strength. However, such blades have the disadvantage of having a relatively large mass.

[0013] 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. Description of the invention

[0014] One of the aims of the invention is therefore to provide a blade suitable for use with a variable pitch mechanism and in an "Open Rotor" type environment, while being able to withstand intense aerodynamic forces, under the constraints of limited size and minimum mass. Furthermore, the proposed blade should preferably comprise a limited number of structural elements and be quick to manufacture.

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

[0016] - a composite material structure comprising a blade root and a profile blade aerodynamics extending from the blade root, the composite material structure comprising a fibrous reinforcement having a portion of blade root extending into the blade root and a portion of blade extending into the aerodynamically profiled blade, and a matrix in which the portion of blade root of the fibrous reinforcement is embedded; - a sleeve comprising: a wall extending around a longitudinal axis (Y) 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; - an insert positioned in the recess so that the foot portion of the fibrous reinforcement is held between the insert and the inner surface of the sleeve; and - a locking piece being inserted into the sleeve and the insert so as to prevent withdrawal along the longitudinal axis (Y) of the insert relative to the sleeve.

[0017] The blade can thus withstand intense aerodynamic forces while maintaining a limited size. Indeed, as the insert holds the fibrous reinforcement against the sleeve, it strengthens the composite material structure and its retention within the sleeve.

[0018] Furthermore, the locking piece prevents any separation of the insert and the sleeve, and therefore also of the composite material structure that is wedged between the insert and the sleeve. The locking piece also prevents the blade from being torn off even in the event of a crack or break in a portion of the sleeve, particularly a portion located beyond the locking piece in a radial direction.

[0019] Furthermore, the blade is formed by a minimal number of elements allowing it to have a minimum mass and to be quick to manufacture.

[0020] 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.

[0021] The fibrous reinforcement is obtained by three-dimensional weaving of strands. The matrix in which the blade root portion of the fibrous reinforcement is embedded is preferably organic and comprises a resin. Preferably, the blade portion is also embedded in the matrix.

[0022] The insert may be a metallic part and may include, in particular, titanium, aluminum, nickel, iron, or one of their alloys. The insert may be a solid part, or a partially solid part, or totally hollow so as to lighten the blade root.

[0023] According to embodiments that can be taken alone or in combination, the blade may further have the following characteristics: - the locking piece includes a locking rod inserted into an opening in the wall of the sleeve; the locking piece is thus simple to manufacture and insert and does not require a potentially complex fastening device; the locking rod is preferably also inserted into an opening in the insert and / or the composite material structure so as to hold the insert and / or the composite material structure together with the sleeve; the locking rod is preferably cylindrical, and even more preferably cylindrical of revolution; the locking piece may be solely a rod or may be a rod comprising additional elements such as, for example, one or more grooves or ribs extending in a direction perpendicular to the rod, an enlarged head intended to be positioned outside the sleeve, or fastening and / or hooking elements;The rod may also have one or more threaded holes so that it can be screwed into the sleeve's orifice; the sleeve's orifice may have a complementary threaded hole that can be positioned at the orifice's inlet and / or outlet; according to one possible variant, the rod may be adjusted by cold crimping; - the orifice is a first orifice and the sleeve also has a second orifice formed in its wall diametrically opposite to the first orifice, the locking rod being inserted into the first and second orifices and passing through the insert; the insert is thus securely held in the sleeve and the resistance to pull-out forces of the insert relative to the sleeve during blade rotation is distributed in an optimized manner; preferably, the insert has a through passage whose open ends are opposite the first and second orifices and the locking rod thus passes through the insert;Preferably, the composite material structure also includes two openings positioned opposite the first and second orifices and the insert passage; the first and / or second orifice may include a thread; - the first and / or second orifice is / are oblong in shape with a width and a length, the length being parallel to the longitudinal axis (Y); the first and / or second orifice preferably have a width adjusted relative to the locking rod; preferably, the length of the first and / or second orifice is configured to form a clearance relative to the locking rod; in this way no force is exerted on the sleeve in nominal mode; preferably, both openings of the composite material structure are oblong in shape, and whether the first and / or second orifice is / are oblong in shape or not; - the locking piece also passes through the fibrous reinforcement; the locking piece thus holds the sleeve, the insert and the fibrous reinforcement together; in the event of a crack or break in a portion of the sleeve, in particular a portion located beyond the locking piece in a radial direction, the locking piece thus prevents the blade from being torn off; preferably, the locking piece is positioned once the fibrous reinforcement is embedded in the matrix; the orifice in the fibrous reinforcement, and in particular in the blade root, may also be oblong; preferably, a ring may be cold-pressed onto the blade root so as to better distribute the forces that may be exerted; - the locking piece extends in a direction perpendicular to the longitudinal axis (Y); the locking piece thus optimally opposes the pull-out forces that the blade undergoes when the blower carrying the blades is in operation; - the insert has a main body inserted into the sleeve and an end extending into the blade portion of the fibrous reinforcement; the insert thus makes it possible to reinforce the blade root portion of the fibrous reinforcement and also part of the blade portion; moreover, in the event of a crack and / or break in the blade root portion, the insert, which is held together with the sleeve, prevents the blade portion from being torn away from the fibrous reinforcement; - the end of the insert has a cross-section which extends in a plane perpendicular to the longitudinal axis Y and has a first dimension 11 in a first direction and a second dimension 12 in a second direction, the first dimension XI being less than the second dimension X2; the insert thus has a thinned shape along the first dimension corresponding to the shape of the blade and does not create any excess thickness which could impact the profiled shape of the blade and its aerodynamics; the first and second directions extend perpendicularly to the longitudinal axis (Y); - the end of the insert has a shape that flares outwards from the sleeve and in the second direction; the flared shape of the end of the insert allows the latter to extend extensively inside the blade portion of the fibrous reinforcement; this flared shape helps to prevent the fibrous reinforcement from being torn away, even in the event of a crack and / or break in the blade root; - 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, the insert being housed in the fiber-free zone; thus, in the end part, the foot portion of the fibrous reinforcement, and in particular all the longitudinal fibers it comprises, is positioned around the insert; - the sleeve recess comprises a central part having a first diameter dl measured radially with respect to the longitudinal axis (Y), and an end part, located with respect to the central part opposite the aerodynamically profiled blade, 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 longitudinal fibers of the foot portion of the fibrous reinforcement thus spread radially away from the longitudinal axis in the end part and allow a widening of the fibrous reinforcement in the end part with respect to the central part, and this, in a complementary manner with respect to the shape of the internal surface; this spreading of the fibrous reinforcement helps to prevent the blade foot from coming out of the sleeve under the effect of centrifugal force during the rotation of the blower of which said blade may be a part;Indeed, since the fibrous reinforcement is embedded in a matrix, its configuration is fixed and can no longer be tightened to pass into the central part; - the first diameter dl and the second diameter d2 are such that d2 / dl > 1.10, preferably > 1.20; the fiber spacing 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; in particular, the end part may have an inclination forming an angle of 15° to 20° with respect to the longitudinal axis, the central part preferably extending parallel to the longitudinal axis; the inclination of the end part may extend over a height of the sleeve of at least 30 mm; - the locking piece is positioned in the end section; tensile, torsional, and / or bending forces are exerted primarily in the blade root portion, which is positioned outside the sleeve for the composite material structure, and in the central section and beyond (towards the blade) for the sleeve. The risks of cracking and / or breakage are most likely in these areas subjected to stress. Thus, when the locking piece is positioned in the end section, it keeps the insert and the composite material structure assembled to the end section of the sleeve, which remains attached to the ball bearing. This prevents the composite material structure from being pulled away, even in the event of cracking and / or breakage in the central section of the sleeve and beyond, as well as in the blade root portion. - the inner surface of the sleeve has, in cross-section, a non-circular geometric shape and the composite material structure is configured to cooperate with the inner surface of the sleeve so as to prevent the rotation of the composite material structure relative to the sleeve around the longitudinal axis (Y); the inner surface of the sleeve may in particular have a cross-section with curvatures, for example an oval shape, and / or have angles, for example a polygonal shape, preferably hexagonal; the liquid composition intended to form the matrix being preferably poured once the foot portion of the fibrous reinforcement is positioned between the insert and the inner wall of the sleeve, the matrix once hardened has an outer shape complementary to the shape of the inner surface of the sleeve, and an inner shape complementary to the shape of the insert, preferably circular.

[0024] According to a second aspect, the invention proposes a method for manufacturing a blade as previously described, said method comprising:

[0025] - a step El of inserting the insert into the fibrous reinforcement, - a step E2 of inserting the assembly formed by the fibrous reinforcement and the insert into the recess so as to maintain the fibrous reinforcement between the insert and the internal surface of the sleeve; - an E3 step of injecting a first composition inside the recess so as to form a matrix in which the blade root portion of the fibrous reinforcement is embedded; and - a step E4 of inserting the locking piece into the sleeve and the insert.

[0026] This process allows the rapid manufacture of a blade, using few parts and without the use of parts and / or fastening tools other than the locking piece.

[0027] According to an example of an embodiment of step El, the insertion of the insert into the fibrous reinforcement can be done by introducing the insert into a previously formed debond in the fibrous reinforcement.

[0028] According to another embodiment of step E1, the fibrous reinforcement may comprise a first and a second skin that are separated. The insert is then placed in the part forming the foot portion of the first skin, and then the second skin is placed on the first skin so as to form the blade foot portion around the insert.

[0029] The fibrous reinforcement, and in particular the blade foot in which the insert is positioned, is then inserted into the recess of the sleeve by distributing the fibers forming the fibrous reinforcement against the inner surface of the wall. The fibrous reinforcement is then wedged between the insert and the inner surface of the sleeve.

[0030] The first composition injected in step E3 spreads in the recess and conforms to the shape of the inner surface of the sleeve and the shape of an outer surface of the insert, then solidifies to form the matrix.

[0031] 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 first composition which then flows between the internal surface of the sleeve and the insert.

[0032] According to one possible embodiment, all the fibrous reinforcement, in particular the blade foot portion and the blade portion, can be embedded in the matrix which is preferably organic, such as a resin.

[0033] According to one possible embodiment, the sleeve and insert are pre-drilled, and the locking piece can be directly inserted into the sleeve and insert. Depending on the position of the blade root in the recess, the blade root, corresponding to the fibrous reinforcement once embedded in the die, can also pass through the blade root. Indeed, if the blade root is positioned between the first and / or second orifice and the corresponding passage of the insert, the locking piece passes through the blade root. A drilling step of the blade root is then performed beforehand.

[0034] According to another possible embodiment, the sleeve and / or insert is (are) not previously drilled, the process may include a step E4i of drilling the sleeve and / or insert, in particular so as to form the first and / or second office.

[0035] 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.

[0036] 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

[0037] 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:

[0038] - 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;

[0039] - [Fig. 3] is a schematic top view of an aircraft according to a mode of realization of the invention;

[0040] - [Fig. 4a] is a schematic longitudinal cross-sectional view of a blade along a method of implementing the invention;

[0041] - [Fig.4b] is a schematic and side view of the sleeve of [Fig.4a];

[0042] - [Fig.4c] is a schematic view from below of the blade of [Fig.4a]; - [Fig.4d] is a schematic perspective view of part of the sleeve of [Fig.4a]; - [Fig.5] is a schematic view from below of the insert in [Fig.4a]; - [Fig.6] is a schematic cross-sectional view of the blade of [Fig.4a]; - [Fig.7a], [Fig.7b] and [Fig.7c] are schematic views of the stress paths experienced by the blade of [Fig.4a]; - Figures [Fig. 8a], [Fig. 8b], and [Fig. 8c] are schematic views of the stress paths experienced by the blade of [Fig. 4a]; and

[0043] - [Fig.9] is a flowchart of a manufacturing process for the blade of [Fig.4a] according to one 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, the 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 blower 3 further comprises an actuation mechanism 8 or variable timing mechanism allowing modification The rotor blade pitch angle is collectively adjusted to adapt engine performance to different flight phases. To this end, each blade 7 comprises a blade root 22 and an aerodynamically profiled blade 24. The blade root 22 is rotatably mounted relative to the hub 6 around a pitch axis Y. More precisely, the blade root 22 is rotatably mounted within a mounting device 10 formed in the hub 6, via 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 2 and 4a to 4d, the turbine blade 7 comprises a composite material structure 20 including a blade root 22 and a blade 24 with an aerodynamic profile extending from the blade root 22. The composite material structure 20 includes a fibrous reinforcement obtained by three-dimensional weaving of strands and having a blade root portion 26 extending into the blade root 22 and a blade portion 28 extending into the aerodynamically profiled blade 24. The composite material further includes a matrix 32 in which the blade root portion 26 of the fibrous reinforcement is embedded.

[0055] The blade 7 also includes a sleeve 34 comprising a wall 36 extending about a longitudinal axis (Y) and having an external surface 38 and an internal surface 40. The external surface 38 is configured to cooperate with a variable pitch mechanism 8 of a turbomachine. The internal surface 40 defines a through recess 42 formed in the sleeve 34 and in which the blade root 22 is housed.

[0056] The blade 7 further includes an insert 25 positioned in the recess 42 so that the blade foot portion 26 of the fibrous reinforcement is held between the insert 25 and the internal surface 40 of the sleeve.

[0057] The position of the insert 25 in the sleeve 34 is maintained by means of a locking piece 44 which is inserted into the sleeve 34 and into the insert 25 so as to prevent withdrawal along the longitudinal axis (Y) of the insert 25 relative to the sleeve 34.

[0058] The blade 7 thus formed can therefore withstand intense aerodynamic forces while having a limited size. Indeed, the insert 25, which holds the fibrous reinforcement against the inner wall 40 of the sleeve 34, reinforces the strength of the composite material structure 20 and its retention within the sleeve 34.

[0059] Furthermore, the locking piece 44 prevents the insert 25 from being detached from the sleeve 34 under the effect of the centrifugal force experienced by the blade 7 during the rotation of the blower. As the fibrous reinforcement is embedded in a matrix 32, its configuration between the insert 25 and the inner wall 40 is fixed, and the retention of the insert 25 assembled with the sleeve 34 by means of the locking piece 44 prevents the composite material structure 20 from detaching from the sleeve 34. The locking piece

[0060] The locking piece 44 includes a locking rod 46 inserted into a first orifice 48 provided in the wall 36 of the sleeve 34 and thus forms a simplified fastening device.

[0061] In this embodiment, the locking rod 44 is a cylinder of revolution of constant diameter d3. The diameter of the locking rod 46 can be at least 20 millimeters (mm), preferably between 20 mm and 40 mm inclusive, and for example 30 mm.

[0062] However, the locking rod 46 may have an oval, square, hexagonal, or any other geometric shape in cross-section. Furthermore, the width dimension of the locking rod 46 (for example, the diameter if the rod is a cylinder of revolution) may not be constant along its entire length.

[0063] The locking rod 46 can be configured so that it cannot translate about its longitudinal axis. In particular, it can be screwed into the first and second holes of the sleeve. It can also be held fixed by means of bolts. According to another embodiment, the locking rod 46 may have lugs that fit into grooves on the sleeve.

[0064] The length of the locking rod 46 is at least equal to an outside diameter of the sleeve 34, the diameter being measured at the point on the outer wall where the first hole is located. The locking rod 46 may, for example, have a length of 100 mm to 180 mm, for example 140 mm when screwed into the first and second holes of the sleeve.

[0065] The locking rod 46 is preferably metallic, and may include, for example, titanium, aluminum, nickel, iron, or one of their alloys.

[0066] According to one possible embodiment, the blade may include a second locking piece. The second locking piece may then have the same characteristics as those described for the first locking piece.

[0067] According to this embodiment, the second locking piece can extend in a direction parallel to that of the first locking piece or in another direction, in particular a direction forming a non-zero angle with the direction of the first locking piece. The sleeve

[0068] The sleeve 34 is preferably metallic so that it can be precisely machined and thus cooperate optimally with a variable shimming mechanism. The sleeve 34 may therefore comprise titanium, aluminum, nickel, iron, or one of their alloys. The sleeve is preferably made of titanium.

[0069] The sleeve 34 has at least the first orifice 48 allowing the passage of the locking rod 46 and preferably has a second orifice 48' provided in its wall 36 diametrically opposite to the first orifice 48. Thus, the locking rod 46 is inserted into the first and second orifices and passes through the sleeve 34 and the insert 25.

[0070] The locking rod 46, being inserted into the two orifices 48 and 48' of the sleeve 34 and passing through the insert 25, opposes the pull-out forces of the insert 25 and the composite material structure 20 in an optimized manner. Indeed, the resistance is distributed so as to be along the pull-out axis of the blade 7, which corresponds to the longitudinal axis Y.

[0071] Preferably, the locking piece 46 also passes through the fibrous reinforcement so as to hold the sleeve 34, the insert 25, and the fibrous reinforcement together. The fibrous reinforcement then extends between the sleeve 34 and the insert 25, preferably to an end edge 68 of the sleeve 34.

[0072] The first and second orifices 48 and 48' are positioned at the same height H relative to the lower edge 68 of the sleeve 34. The locking piece 46 thus extends in a direction perpendicular to the longitudinal axis (Y). The locking piece 46 thus optimally resists the pull-out forces experienced by the blade when the blower 4, 5 carrying the blades 7 is in operation.

[0073] As shown in [Fig. 4d], the first orifice 48 and / or the second orifice 48' are preferably oblong in shape. They thus have a width L1 and a length L2, the length L2 being parallel to the longitudinal axis (Y). Since the locking rod 46 is a cylinder of revolution with a constant diameter DI, the width of the first orifice 48 and / or the second orifice 48' is adjusted relative to the locking rod 46, but the length has some play relative to the locking rod 46.

[0074] The width is measured between two longitudinal edges 60 and 61, and the adjusted width means that there is little space between each edge 60 (or 61) and the locking rod 46, for example, a distance of between 1 and 3 mm. In this way, The locking rod 46 is almost in contact with the two longitudinal edges 60 and 61 but does not rub against them and is not jammed by the two longitudinal edges 60 and 61.

[0075] The length is measured between two lateral edges 62 and 63. A clearance, or space, ranging from 6 to 10 mm, and preferably between 7 and 8 mm, is present between each lateral edge 62 and 63 and the locking rod 46. Thus, the locking rod 46 can translate along the longitudinal axis Y. The clearance between the rod 46 and the lateral edges 62 and 63 ensures that no force is exerted on the locking rod 46 during the nominal operation of the aircraft.

[0076] The two longitudinal borders 60 and 61 each have a central straight portion allowing the translation of the locking rod 46 along the longitudinal axis Y.

[0077] On the other hand, no translation of the locking piece 44 is possible in a direction perpendicular to the longitudinal axis Y once the locking piece 44 has been put in place.

[0078] Furthermore, the recess 42 of the sleeve 34 comprises a central portion 64 and an end portion 66, located, relative to the central portion 64, opposite the aerodynamically profiled blade 24. The central portion 64 has a first diameter dl and the end portion has a second diameter d2 which is greater than the diameter dl; the first diameter dl and the second diameter d2 are each measured radially with respect to the longitudinal axis (Y). The fibrous reinforcement preferably extends into the central part 64 and also into the end part 66, up to the end edge 68. The fibrous reinforcement thus deviates radially from the longitudinal axis Y in the end part 66 and is therefore wider compared to the central part 64. This deviation of the fibrous reinforcement helps to prevent the blade root 26 from coming out of the sleeve 34 under the effect of centrifugal force during the rotation of the blower 4 and / or 5.Indeed, since the fibrous reinforcement is embedded in the matrix 32, its configuration is fixed and can no longer be tightened to pass into the central part 64.

[0079] Preferably, the first diameter dl and the second diameter d2 are such that d2 / dl > 1.10, preferably > 1.20.

[0080] In this embodiment, the locking piece 44 is positioned in the end portion 66. In this way, it is positioned in a part of the sleeve 34 that is subjected to little stress. Thus, if a crack or break occurs on the sleeve 34 due, for example, to bending or tensile stresses, it is positioned beyond the locking piece 44 in a radial direction, and the locking piece 44 can therefore continue to hold the insert 25 and the composite material structure 20 connected to the hub 6, despite the damage to the sleeve 34.

[0081] However, according to possible embodiment variants, the locking piece 44 can be positioned at other heights of the sleeve 34.

[0082] Furthermore, the blade may include one or more other locking pieces, identical or different from the locking piece 44 and positioned at different heights of the sleeve relative to the locking piece 44.

[0083] As can be seen in [Fig. 4c], the inner surface 40 of the sleeve 34 has a non-circular geometric shape in cross-section, and the composite material structure 20, in particular the blade foot 22, is configured to cooperate with the inner surface of the sleeve 34 so as to prevent the rotation of the composite material structure 20 relative to the sleeve 34 around the longitudinal axis (Y). In this embodiment, the cross-section of the inner surface 40 of the sleeve 34 has a hexagonal shape. The composition intended to form the matrix surrounding the fibrous reinforcement is injected in liquid form once the fibrous reinforcement is positioned in the sleeve 34. The matrix 32 solidifies in a shape complementary to the inner surface 40 of the sleeve 34 and also in a shape complementary to an outer wall 70 of the insert 25.Thus, any rotation of the composite material structure 20 around the Y axis is prevented, despite the stresses experienced by the blade 7 during its use. The insert

[0084] The insert 25 can be a metallic part and may include, in particular, titanium, aluminum, nickel, iron, or one of their alloys. In this embodiment, the insert is hollow so as to lighten the blade root. However, the insert may also be totally or partially solid.

[0085] According to another possible embodiment, the insert can be a laminated composite of unidirectional, 2D fabric or braid.

[0086] The insert 25 has a main body 72 inserted into the sleeve and an end 74 extending into the blade portion 24 of the fibrous reinforcement. The insert 25 thus makes it possible to reinforce the blade root portion 22 of the fibrous reinforcement and also the blade portion 28.

[0087] The main body 72 is preferably a cylinder of revolution around which the fibers 30 of the fibrous reinforcement are distributed. The diameter of the main body 72 can be between 40 and 80 mm inclusive.

[0088] As shown in [Fig. 5], the end 74 of the insert 25, which extends from the main body 72, has a cross-section extending in a plane perpendicular to the longitudinal axis Y and has a first dimension XI in a first direction and a second dimension X2 in a second direction, the first dimension XI being smaller than the second dimension X2. The insert 25 thus has a tapered shape along the first dimension XI, corresponding to the shape of the blade 24, and does not create any excess thickness that could affect the streamlined shape of the blade 24 and its aerodynamics.

[0089] Furthermore, the end 74 of the insert 25 has a shape that flares outwards from the sleeve and in the second direction. The insert 25 thus has a cylindrical shape of revolution complementary to the fibrous reinforcement in the blade root portion 26 and then flares out into the blade 24 to form a more extensive support. Thus, if a crack or break occurs at the blade root 22, and in particular in the part of the blade root that is not inserted into the sleeve 34, the blade 24 is held by the insert 25, and in particular by its end 74, around which the blade root 22 cannot pass. Any tearing of the blade 24 is thus prevented.

[0090] Preferably, the fibrous reinforcement has a debonding on either side of which longitudinal fibers 30 extend, the debonding forming a fiber-free zone in the center of the fibrous reinforcement. The insert 25 is housed in the fiber-free zone. The debonding is shaped according to the form of the insert 25. In this embodiment, the debonding is formed in the blade root portion 26 of the fibrous reinforcement that receives the main body 72 of the insert 25 and also in the blade portion 28 that receives the end 74 of the insert 25.

[0091] The locking piece 44, and in particular the locking rod 46, is inserted into the main body 72 of the insert 25. For this purpose, the insert 25 has a through passage 76 whose open ends 78 and 78' are positioned opposite the first orifice 48 and the second orifice 48'.

[0092] In this embodiment, the main body 72 of the insert 25 is hollow. However, the insert 25 may be only partially hollow or even solid. The fibrous structure

[0093] The fibrous structure comprises strands including longitudinal fibers 30, at least a portion of which extend continuously inside the blade root 22 and inside the airfoil blade 24. The longitudinal fibers 30 spread apart from each other and are distributed, preferably uniformly, around the insert 25.

[0094] As illustrated in [Fig. 6], 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.

[0095] 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. In the case where the skins are in two parts, the joining of the two skins at their periphery can be ensured by the resin.

[0096] Preferably, the matrix in which the fibrous reinforcement is embedded comprises an organic material (thermoset, thermoplastic, or elastomer) or is a carbon matrix. For example, the matrix may comprise a plastic material, typically a polymer, such as epoxy, bismaleimide, or polyimide. The fibers of the fibrous reinforcement comprise at least one of the following materials: carbon, glass, aramid, polypropylene, and / or ceramic.

[0097] The fibrous reinforcement comprises longitudinal fibers 30 and also transverse fibers not shown in the figures.

[0098] The blade portion 28 may also include one or two cavities 54, 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 24 while allowing it to retain its aerodynamic shape.

[0099] 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.

[0100] 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.

[0101] However, according to one possible embodiment, the cavities 54 may remain empty and not be filled by filler pieces.

[0102] Force path during fan rotation

[0103] With reference to figures 7a, 7b and 7c, the paths of force in tension and torsion during nominal operation are shown, the paths of force being represented by arrows.

[0104] Figure 7a represents the stress paths when the sleeve 34 and the structure The composite material 20 remains intact. The forces exerted on the sleeve 34 are transmitted to the composite material structure 20, which cannot be pulled away from the sleeve 34 since it is held wedged between the sleeve 34 and the insert 25, and prevented from being pulled away thanks to the flare of the internal diameter in the end part of the sleeve.

[0105] Fig. 7b represents the case where the sleeve 34 has suffered a rupture in plane A. The locking piece 44 makes it possible to hold the end part 66 of the sleeve 34, the composite material structure and the insert 25 securely assembled. The forces experienced by the sleeve 34 are then transmitted in the same way as in Fig. 7a.

[0106] Figure 7c illustrates the case where the composite material structure 20 has a break in the portion of the blade root 22 that lies outside the sleeve 34, according to plane B. The forces acting on the sleeve 34 can no longer be transmitted through the composite material structure 20 due to the break. These forces are then taken up by the insert 25 via the locking piece 44 and transmitted to the composite material structure 20, which cannot be detached because it is held in place by the insert 25, itself held to the fan hub 6 by the sleeve 34.

[0107] With reference to figures 8a, 8b and 8c, the bending force paths during nominal operation are shown, the force paths being represented by arrows.

[0108] Figure 8a shows the load paths when the sleeve 34 and the composite material structure 20 are intact. The loads experienced by the sleeve 34 are transmitted to the composite material structure 20, which cannot be pulled away from the sleeve 34 since it is held wedged between the sleeve 34 and the insert 25, and prevented from pulling away by the flared internal diameter in the end portion of the sleeve.

[0109] Figure 8b represents the case where the sleeve 34 has suffered a rupture in plane A. The forces are then taken up by the locking piece 44 and transmitted to the composite material structure via the insert 25. The composite material structure 20 cannot be pulled away because it is held by the end part 66 of the sleeve 34 and the insert 25 via the locking piece 44.

[0110] Figure 8c illustrates the case where the composite material structure 20 has a break in the portion of the blade root 22 that lies outside the sleeve 34, according to plane B. The forces acting on the sleeve 34 can no longer be transmitted through the composite material structure 20 due to the break. These forces are then transferred to the insert 25 via the locking piece 44 and to the composite material structure 20, which cannot be detached because it is held in place by the insert 25, itself held to the fan hub 6 by the sleeve 34. Blade manufacturing process

[0111] With reference to [Fig. 9], a manufacturing process 80 for a blade 7 includes a step El of inserting the insert 25 into the fibrous reinforcement. According to an example of an embodiment of step El, the insertion of the insert 25 into the fibrous reinforcement can be done by introducing the insert 25 into a previously formed debond in the fibrous reinforcement.

[0112] According to another embodiment of step E1, the fibrous reinforcement may comprise a first and a second skin which are separated. The insert 25 is then placed in the part forming the foot portion of the first skin, and then the second skin is placed on the first skin so as to form the foot portion of the blade 22 around the insert 25.

[0113] The method also includes a step E2 of inserting the assembly formed by the fibrous reinforcement and the insert 25 into the recess 42 so as to maintain the fibrous reinforcement between the insert 25 and the inner surface 40 of the sleeve 34. Preferably, the foot portion 22 of the fibrous reinforcement surrounds the entire outer surface 70 of the cylindrical body 72 and is positioned against the inner surface 40 of the sleeve 34. Furthermore, the cylindrical body 72 and the fibrous reinforcement both extend to the end edge 68 of the sleeve 34. The fibrous reinforcement is then wedged between the insert and the inner surface of the sleeve.

[0114] The process further comprises a step E3 of injecting a first composition into the recess 42 so as to form a matrix 32 in which the blade root portion 26 of the fibrous reinforcement is embedded. Preferably, step E3 is carried out by overmolding, by introducing the assembly formed by the sleeve 34, the fibrous reinforcement, and the insert 25 into a mold and then injecting the first composition according to the RTM process to embed the fibers of the fibrous reinforcement. The resin then flows between the inner surface 40 of the sleeve 34 and the insert 25.

[0115] The first composition injected in step E3 is distributed in the recess 42 and conforms to the shape of the internal surface 40 of the sleeve 34 and the shape of the external surface 70 of the insert 25 and then solidifies to form the matrix 32. The blade 7 shown in [Fig.2] is then obtained.

[0116] The resin may be, in particular, an epoxy resin, a thermoplastic resin or a polybismaleimide (BMI) resin.

[0117] The method also includes a step E4 of inserting the locking piece into the sleeve 34 and the insert 25. Step E3 is carried out before step E4.

[0118] This process thus allows the manufacture of a blade 7 in a rapid manner, using few parts and without the use of parts and / or fastening tools other than the locking piece 44.

[0119] According to one possible embodiment, the sleeve 34 and the insert 25 are pre-drilled, and the locking piece 44 can be directly inserted into the sleeve 34 and the insert 25. Depending on the position of the fibrous reinforcement in the recess 42, the locking piece 44 can also pass through the fibrous reinforcement. Indeed, if the fibrous reinforcement is positioned between the first and / or second holes 48 and 48' and The corresponding passage 76 of the insert 25, the locking piece 44 also passes through the fibrous reinforcement. A drilling step through the fibrous reinforcement can be performed, particularly if the matrix is ​​solidified.

[0120] According to another possible embodiment, the sleeve 34 and / or the insert 25 is (are) not previously drilled, the process may include a step E4i of drilling the sleeve 34 and / or the insert 25, in particular so as to form the first and / or the second orifice 48 and 48'.

[0121] 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.

[0122] 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 having a portion of blade root (26) extending into the blade root (22) and a portion of blade (28) extending into the blade (24) with an aerodynamic profile, and a matrix (32) in which the portion of blade root (26) of the fibrous reinforcement is embedded; - 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;- an insert (25) positioned in the recess (42) so that the foot portion (26) of the fibrous reinforcement is held between the insert (24) and the internal surface (40) of the sleeve (34); and - a locking piece (44) passing through the sleeve (34) and the insert (25) so as to prevent withdrawal along the longitudinal axis (Y) of the insert (25) relative to the sleeve (34).

2. Blade according to claim 1, wherein the locking piece (44) comprises a locking rod (46) inserted into an orifice (48) formed in the wall (36) of the sleeve (34).

3. Blade according to claim 2, wherein the orifice (48) is a first orifice and wherein the sleeve (34) further comprises a second orifice (48') formed in its wall (36) in a diametrically opposite manner to the first orifice (48), the locking rod (46) being inserted into the first and second orifice (48, 48') and passing through the insert (25).

4. Blade according to claim 2 or 3, wherein the first orifice (48) and / or the second orifice (48') is oblong in shape having a width (L2) and a length (Ll), the length (Ll) being parallel to the longitudinal axis (Y).

5. Blade according to any one of the preceding claims, wherein the locking piece (44) further passes through the fibrous reinforcement.

6. Blade according to any one of the preceding claims wherein the locking piece (44) extends in a direction perpendicular to the longitudinal axis (Y).

7. Blade according to any one of the preceding claims, wherein the insert (25) has a main body (72) inserted in the sleeve (34) and an end (74) extending into the blade portion (28) of the fibrous reinforcement.

8. Blade according to claim 7, wherein the end (74) of the insert (25) has a cross-section which extends in a plane perpendicular to the longitudinal axis (Y) and has a first dimension (XI) in a first direction and a second dimension (X2) in a second direction, the first dimension (XI) being less than the second dimension (X2).

9. Blade according to claim 7 or 8, wherein the end (74) of the insert (25) has a shape which flares away from the sleeve (34) and in the second direction.

10. Blade according to any one of the preceding claims, 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, the insert (25) being housed in the fiber-free zone.

11. Blade according to any one of the preceding claims, wherein the recess (24) comprises a central part (64) having a first diameter dl measured radially with respect to the longitudinal axis (Y), and an end part (66), located with respect to the central part (64) 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.

12. Blade according to any one of the preceding claims, wherein the locking piece (44) is positioned in the end part (66).

13. Blade according to any one of the preceding claims, wherein the internal surface (40) of the sleeve (34) has, in section transverse, a non-circular geometric shape and the composite material structure (20) is configured to cooperate with the internal surface (40) of the sleeve (34) so ​​as to prevent the rotation of the composite material structure (20) relative to the sleeve (34) around the longitudinal axis (Y).

14. A method for manufacturing a blade according to any one of claims 1 to 13, comprising: - a step E1 of inserting the insert (25) into the fibrous reinforcement, - a step E2 of inserting the assembly formed by the fibrous reinforcement and the insert (25) into the recess (42) so as to maintain the fibrous reinforcement (30) between the insert (25) and the inner surface (40) of the sleeve (34); - a step E3 of injecting a first composition into the recess (42) so as to form a matrix in which the blade foot portion (26) of the fibrous reinforcement is embedded; and - a step E4 of inserting the locking piece (44) into the sleeve (34) and the insert (25).

15. A manufacturing method according to claim 14 when it depends on claim 2 or 3, further comprising a step E4i of drilling the sleeve (34) so ​​as to form the first orifice (48) and / or the second orifice (48') and / or the insert (25) so as to form the orifice of the insert.

16. 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 13, or being manufactured by means of the method according to claim 14 or 15.

17. Aircraft (19) comprising a fuselage and further comprising at least one gas turbine engine (1) conforming to claim 16, said engine (1) being attached to the fuselage.