Blade made of composite material comprising a fibrous structure

Abstract

The invention relates to a blade for a turbine engine, comprising: - a composite material structure (20) comprising a blade root (22) and a blade body (24) having an aerodynamic profile; and - a sleeve (34) comprising a wall (36) extending about a longitudinal axis (Y) and having an outer surface (38) that is configured to cooperate with a variable-pitch mechanism of a turbine engine, and an inner surface (40) delimiting a recess (42) in which the blade root (22) is housed, the composite material structure (20) being arranged against the inner surface (40) and the longitudinal fibres (30) being arranged substantially parallel to the longitudinal axis (Y) in the central portion (44) and extending radially away from the longitudinal axis (Y) in the end portion (46).

Description

[0001] TITLE: BLADE MADE OF COMPOSITE MATERIAL COMPRISING A FIBROUS STRUCTURE

[0002] FIELD OF INVENTION

[0003] The invention relates generally to the field of turbomachinery, and in particular to turbomachine blades.

[0004] The invention relates more particularly, but not exclusively, to a blade intended for use in an unfaired aircraft engine fan rotor (such as an "Open Rotor" type engine having two rotating propellers or a USF type engine for "Unducted Single Fan" having a movable blade and a fixed blade or a turboprop engine having an architecture with a single propeller).

[0005] TECHNOLOGICAL BACKGROUND

[0006] The advantage of unfaired fan engines 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 BPR), and consequently, reduced fuel consumption. Therefore, in this type of engine, the fan blades can have a large span.

[0007] In addition, these engines generally include a mechanism to change the angle of the blades in order to adapt the thrust generated by the fan according to the different phases of flight.

[0008] However, the design of such blades requires taking into account conflicting constraints.

[0009] On the one hand, the design of these blades must allow for optimal aerodynamic performance, notably 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.

[0010] 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.

[0011] Furthermore, on unshod fan designs, engine start-up is generally performed with a very open valve timing. Indeed, a very open valve timing allows power to be consumed by torque, which ensures machine safety by guaranteeing low fan speeds. However, with a very open valve timing, the blades experience turbulent, completely separated aerodynamic flow, which generates broadband vibrational excitation. In particular, on large-chord, long-span blades, the bending stress is intense, even though the engine speed is not at its maximum.

[0012] In normal operation, that is, during ground and flight phases, the fan pitch is adjusted to a more closed angle. The aerodynamic flow is then perfectly controlled, particularly in relation to 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 fairing, the angle of attack experienced by the individual fan blades varies according to their angular position and the aircraft's angle of attack, creating a cyclic bending moment (commonly called the 1P moment) on the blades. This cyclic bending moment then generates significant bending stresses on the blades in addition to the centrifugal forces due to their rotation.

[0013] The forces and stresses exerted on the blades can lead to their breakage, which, in the case of an unfaired engine, can result in the blade being torn off and potentially striking and damaging the aircraft, or falling and causing damage on the ground. Various manufacturing materials have therefore been used to produce blades with sufficient strength to prevent them from being torn off.

[0014] The blades can, for example, be made of metallic material, giving them good mechanical strength. However, such blades have the disadvantage of being relatively heavy.

[0015] 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 they are subjected to. These aerodynamic stresses can therefore damage the blades and / or the hub in the interface area between the blades and the fan rotor hub, at the blade root.

[0016] DESCRIPTION OF THE INVENTION

[0017] 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, all under the constraints of limited size and minimum mass. Furthermore, the proposed blade should preferably have a limited number of structural elements and be quick to manufacture.

[0018] According to a first aspect of the invention, a blade for a turbomachine is proposed comprising: a composite material structure including a blade root and an aerodynamically profiled blade extending from the blade root, the composite material structure including a fibrous reinforcement having a portion of the blade root extending into the blade root and a portion of the blade extending into the aerodynamically profiled blade, and a matrix in which the portion of the blade root of the fibrous reinforcement is embedded; a sleeve including: a wall extending around a longitudinal axis (Y) and having an external surface configured to cooperate with a variable pitching mechanism of a turbomachine, and an internal surface delimiting a through recess formed in the sleeve and in which the blade root 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.

[0019] The blade can thus withstand intense aerodynamic forces while maintaining a compact size. Indeed, because the insert holds the fibrous reinforcement against the sleeve, it strengthens the composite structure and secures it within the sleeve.

[0020] Furthermore, the locking piece prevents the insert from separating from the sleeve, and therefore also prevents the composite material structure, which is sandwiched between the insert and the sleeve, from separating. The locking piece also prevents the blade from being torn off, even if a crack or break occurs in a portion of the sleeve, particularly a portion located radially beyond the locking piece.

[0021] Furthermore, the blade is formed by a minimal number of elements allowing it to have a minimal mass and to be quick to manufacture.

[0022] 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 be made of titanium, aluminum, nickel, iron, or one of their alloys. The sleeve is preferably made of titanium. 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 includes a resin. Preferably, the blade portion is also embedded in the matrix.

[0023] The insert can be a metallic part and may include, in particular, titanium, aluminum, nickel, iron, or one of their alloys. The insert can be a solid part, a partially solid part, or a completely hollow part in order to lighten the blade root.

[0024] Depending on embodiments that can be taken alone or in combination, the blade may also have the following characteristics:

[0025] - 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 hole, the sleeve hole having a complementary threaded hole which can be positioned at the inlet of the hole and / or at the outlet of the hole; according to a possible variant, the rod can be adjusted by cold crimping;

[0026] - the orifice is a first orifice and the sleeve further comprises 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 the rotation of the blades is distributed in an optimized manner; preferably, the insert comprises 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 comprises two openings positioned opposite the first and second orifices and the passage of the insert; the first and / or the second orifice may have a thread;

[0027] - 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;

[0028] - 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;

[0029] - 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;

[0030] - 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;

[0031] - 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 X1 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);

[0032] - 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;

[0033] - 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;

[0034] - the sleeve recess comprises a central part having a first diameter d1 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 d1; 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;

[0035] - the first diameter d1 and the second diameter d2 are such that d2 / d1 > 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;

[0036] - 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, and therefore 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.

[0037] - 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.

[0038] According to a second aspect, the invention proposes a method for manufacturing a blade as previously described, said method comprising:

[0039] - a step E1 of inserting the insert into the fibrous reinforcement,

[0040] - 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;

[0041] - 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

[0042] - a step E4 of inserting the locking piece into the sleeve and the insert.

[0043] This process allows for the rapid manufacture of a blade, using few parts and without the need for any parts and / or fastening tools other than the locking piece. According to an example of the implementation of step E1, the insert can be inserted into the fiber reinforcement by introducing the insert into a previously formed debond in the fiber reinforcement.

[0044] According to another example of the implementation of step E1, the fibrous reinforcement can 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 top of the first skin so as to form the blade foot portion around the insert.

[0045] 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.

[0046] The first composition injected in step E3 spreads into 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.

[0047] Preferably, step E3 is carried out by overmolding by introducing the assembly 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.

[0048] According to one possible embodiment, all the fibrous reinforcement, in particular the blade root portion and the blade portion, can be embedded in the matrix which is preferably organic, such as a resin.

[0049] In 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 within the recess, the locking piece can also pass through the blade root once embedded in the die. Specifically, if the blade root is positioned between the first and / or second orifice and the corresponding opening in the insert, the locking piece will pass through the blade root. In this case, the blade root is pre-drilled.

[0050] According to another possible embodiment, the sleeve and / or insert is (are) not pre-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.

[0051] 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.

[0052] 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.

[0053] BRIEF DESCRIPTION OF THE FIGURES

[0054] 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:

[0055] - [Fig. 1] is a schematic perspective view of a gas turbine engine according to one embodiment of the invention;

[0056] - [Fig. 2] is a schematic longitudinal cross-sectional view of a blade according to one embodiment of the invention;

[0057] - [Fig. 3] is a schematic top view of an aircraft according to one embodiment of the invention;

[0058] - [Fig. 4a] is a schematic longitudinal cross-sectional view of a blade according to one embodiment of the invention;

[0059] - [Fig. 4b] is a schematic and side view of the sleeve in figure 4a;

[0060] - [Fig. 4c] is a schematic view from below of the blade in figure 4a;

[0061] - [Fig. 4d] is a schematic perspective view of part of the sleeve in figure 4a;

[0062] - [Fig. 5] is a schematic view from below of the insert in figure 4a;

[0063] - [Fig. 6] is a schematic cross-sectional view of the blade in figure 4a;

[0064] - [Fig. 7a], [Fig. 7b] and [Fig. 7c] are schematic views of the stress paths experienced by the blade in figure 4a;

[0065] - Figures 8a, 8b and 8c are schematic views of the stress paths experienced by the blade in Figure 4a; and

[0066] - [Fig. 9] is a flowchart of a manufacturing process for the blade of figure 4a according to an embodiment of the invention.

[0067] DETAILED DESCRIPTION OF AN EXAMPLE OF IMPLEMENTATION In Figure 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).

[0068] 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.

[0069] In the example illustrated in Figure 1, 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 intake located on the side).

[0070] Furthermore, the invention also applies to motors with different architectures, such as an architecture comprising a blower rotor with moving blades and a blower stator with fixed blades, or a single blower rotor.

[0071] The invention is applicable to turboprop-type architectures (comprising a single fan rotor).

[0072] In Figure 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.

[0073] As illustrated in Figure 2, the fan 3 further includes an actuation mechanism 8, or variable pitch mechanism, which allows the pitch angle of the rotor blades to be collectively adjusted in order to adapt the engine's performance to the different phases of flight. 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 around a pitch axis Y. More precisely, 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.

[0074] 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 from the engine, when engine 1 is running, in order to generate lift. Conversely, the blade root 22 is designed to extend out of the air stream.

[0075] As illustrated in Figure 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 attached under one wing 17 of the aircraft 19.

[0076] According to another possible configuration, two engines 1 can be fixed under each wing 17.

[0077] 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.

[0078] The blade 7 also includes a sleeve 34 comprising a wall 36 extending around 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.

[0079] 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.

[0080] 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.

[0081] The resulting blade 7 can withstand intense aerodynamic forces while maintaining a compact size. Indeed, the insert 25, which holds the fibrous reinforcement against the inner wall 40 of the sleeve 34, strengthens the composite material structure 20 and secures it within the sleeve 34.

[0082] Furthermore, the locking piece 44 prevents the insert 25 from being detached from the sleeve 34 under the effect of the centrifugal force exerted on the blade 7 during the rotation of the blower. Since 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.

[0083] The locking piece

[0084] 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.

[0085] 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 of terminals, and for example 30 mm.

[0086] However, the locking rod 46 can 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.

[0087] The locking rod 46 can be configured so that it cannot translate along 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.

[0088] The length of the locking rod 46 is at least equal to one 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 can, 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.

[0089] The locking rod 46 is preferably metallic, and may include, for example, titanium, aluminum, nickel, iron, or one of their alloys.

[0090] 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.

[0091] 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

[0092] The sleeve 34 is preferably made of metal so that it can be precisely machined and thus cooperate optimally with a variable shimming mechanism. The sleeve 34 may therefore be made of titanium, aluminum, nickel, iron, or one of their alloys. The sleeve is preferably made of titanium.

[0093] 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.

[0094] With the locking rod 46 inserted into the two orifices 48 and 48' of the sleeve 34 and passing through the insert 25, it optimally resists the pull-out forces on the insert 25 and the composite material structure 20. In fact, the resistance is distributed so as to be along the pull-out axis of the blade 7, which corresponds to the longitudinal axis Y.

[0095] 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.

[0096] 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 therefore optimally resists the pull-out forces experienced by the blade when the blower 4, 5 carrying the blades 7 is in operation.

[0097] As shown in Figure 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, with the length L2 being parallel to the longitudinal axis (Y). Since the locking rod 46 is a cylinder of revolution with a constant diameter D1, 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.

[0098] 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 or get caught by them.

[0099] The length is measured between two lateral edges 62 and 63. A clearance, or gap, 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.

[0100] 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.

[0101] 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.

[0102] Furthermore, the recess 42 of the sleeve 34 comprises a central portion 64 and an end portion 66, located opposite the aerodynamically profiled blade 24 relative to the central portion 64. The central portion 64 has a first diameter d1, and the end portion has a second diameter d2, which is larger than the diameter d1. Both the first diameter d1 and the second diameter d2 are 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.

[0103] Preferably, the first diameter d1 and the second diameter d2 are such that d2 / d1 > 1.10, preferably > 1.20.

[0104] 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.

[0105] However, according to possible embodiment variants, the locking piece 44 can be positioned at other heights of the sleeve 34.

[0106] 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.

[0107] As shown in Figure 4c, the inner surface 40 of the sleeve 34 has a non-circular geometric shape in cross-section, and the composite material structure 20, particularly 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. Since 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.

[0108] The insert

[0109] 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 to lighten the blade root. However, the insert may also be totally or partially solid.

[0110] According to another possible embodiment, the insert can be a laminated composite of unidirectional, 2D fabric or braid.

[0111] The insert 25 has a main body 72 inserted into the sleeve and an end 74 extending into the blade portion 24 of the fiber reinforcement. The insert 25 thus reinforces the blade root portion 22 of the fiber reinforcement and also the blade portion 28.

[0112] 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. As shown in Figure 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 possesses a first dimension X1 in one direction and a second dimension X2 in a second direction, the first dimension X1 being smaller than the second dimension X2. The insert 25 thus has a tapered shape along the first dimension X1, 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.

[0113] Furthermore, the end 74 of the insert 25 has a flared shape as it moves away from the sleeve and in the second direction. The insert 25 thus has a cylindrical shape of revolution that complements the fibrous reinforcement in the blade root portion 26 and then flares out into the blade 24 to provide a more extensive support. Therefore, if a crack or break occurs at the blade root 22, and particularly in the portion of the blade root not inserted into the sleeve 34, the blade 24 is held in place by the insert 25, specifically by its end 74, around which the blade root 22 cannot pass. Any detachment of the blade 24 is thus prevented.

[0114] Preferably, the fibrous reinforcement has a debonding joint 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.

[0115] 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'.

[0116] 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.

[0117] The fibrous structure

[0118] The fibrous structure comprises strands including longitudinal fibers 30, at least a portion of which extend continuously inside the blade root 22 and the aerodynamically profiled blade 24. The longitudinal fibers 30 spread apart and are preferably uniformly distributed around the insert 25. As illustrated in Figure 6, the fibrous reinforcement comprises two skins 50, which are joined 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 in line with the flow of gases entering the turbomachine. It corresponds to the forward part of an aerodynamic profile that faces the airflow and divides the airflow into an intrados flow I and an extrados flow E.The trailing edge 52' corresponds to the rear part of the aerodynamic profile, where the intrados and extrados flows meet.

[0119] The 50 skins of the aerodynamically profiled 24 blade are made of a composite material comprising fiber reinforcement densified by a matrix. They are therefore monolithic and manufactured in a single piece according to a non-limiting embodiment. In cases where the skins are in two parts, the joining of the two skins at their periphery can be ensured by resin.

[0120] 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.

[0121] The fibrous reinforcement includes 30 longitudinal fibers and also transverse fibers not shown in the figures.

[0122] The blade portion 28 may also include one or two cavities 54, preferably two cavities 54, each accommodating a shaping piece 56. The cavities 54 are formed by debonding in the weave. Each shaping 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 maintain its aerodynamic shape.

[0123] The rigid material forming the part(s) of conformation 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.

[0124] The shaping piece(s) 56 allow the blade 24 with the aerodynamic profile of the blade 7 to be given the desired thickness and shape, while using a lighter material than other elements of the blade. However, according to one possible embodiment, the cavities 54 can remain empty and not be filled by filler pieces.

[0125] Force path during blower rotation

[0126] With reference to figures 7a, 7b and 7c, the force paths in tension and torsion during nominal operation are shown, the force paths being represented by arrows.

[0127] Figure 7a shows the stress paths when the sleeve 34 and the composite material structure 20 are intact. The stresses 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.

[0128] Figure 7b represents the case where the sleeve 34 has suffered a rupture in plane A. The locking piece 44 allows the end part 66 of the sleeve 34, the composite material structure and the insert 25 to be held securely together. The forces experienced by the sleeve 34 are then transmitted in the same way as in Figure 7a.

[0129] 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. Due to the break, the forces acting on the sleeve 34 can no longer be transmitted through the composite material structure 20. 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.

[0130] With reference to figures 8a, 8b and 8c, the bending force paths during nominal operation are shown, the force paths being represented by arrows.

[0131] Figure 8a shows the stress paths when the sleeve 34 and the composite material structure 20 are intact. The stresses 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.

[0132] 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 torn away because it is held by the end part 66 of the sleeve 34 and the insert 25 via the locking piece 44.

[0133] 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. Due to the break, the forces acting on the sleeve 34 can no longer be transmitted through the composite material structure 20. 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.

[0134] Blade manufacturing process

[0135] With reference to Figure 9, a manufacturing process 80 for a blade 7 includes a step E1 of inserting the insert 25 into the fiber reinforcement. According to an example of an embodiment of step E1, the insertion of the insert 25 into the fiber reinforcement can be carried out by introducing the insert 25 into a previously formed debond in the fiber reinforcement.

[0136] According to another embodiment of step E1, the fibrous reinforcement may comprise a first and a second skin that 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 top of the first skin so as to form the foot portion of the blade 22 around the insert 25.

[0137] 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, both the cylindrical body 72 and the fibrous reinforcement 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.

[0138] The process further includes a step E3 of injecting a first composition into the recess 42 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 placing 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. The first composition injected in step E3 spreads within the recess 42 and conforms to the shape of the inner surface 40 of the sleeve 34 and the shape of the outer surface 70 of the insert 25, then solidifies to form the matrix 32. The blade 7 shown in Figure 2 is then obtained.

[0139] The resin can be, in particular, an epoxy resin, a thermoplastic resin or a polybismaleimide (BMI) resin.

[0140] The process 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.

[0141] This process allows the rapid manufacture of a blade 7, using few parts and without the use of parts and / or fixing tools other than the locking piece 44.

[0142] 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 fiber reinforcement in the recess 42, the locking piece 44 can also pass through the fiber reinforcement. Indeed, if the fiber reinforcement is positioned between the first and / or second orifices 48 and 48' and the corresponding passage 76 of the insert 25, the locking piece 44 also passes through the fiber reinforcement. A drilling step through the fiber reinforcement can be performed, particularly if the matrix is ​​solidified.

[0143] 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'.

[0144] The blade 7 thus formed can 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 can 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.

[0145] 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) including a blade root (22) and an aerodynamically profiled blade (24) extending from the blade root (22), the composite material structure (20) including 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 aerodynamically profiled blade (24), 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 blade foot portion (26) of the fibrous reinforcement is held between the insert (24) and the inner 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 with respect to the first orifice (48), the locking rod (46) being inserted in 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 (L1), the length (L1) 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 in which 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 (X1) in a first direction and a second dimension (X2) in a second direction, the first dimension (X1) 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 out 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 d1 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 d1.

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 cross-section, 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 internal surface (40) of the sleeve (34); - an E3 step of injecting a first composition inside 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. 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.

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