Reinforcement comprising mixture of fiber cuts and tackifier for composite bucket of turbomachine

Abstract

The present application relates to a reinforcement (6) for a bucket (1) of a turbomachine (100), the bucket (1) comprising a first shell layer (2) and a second shell layer (3) made of a composite material, the first shell layer and the second shell layer each comprising inner end portions (21, 31) spaced apart from one another so as to define an inner cavity (4) of the bucket (1) therebetween, the inner cavity opening into an opening (5), the reinforcing member (6) is adapted to be arranged in the inner cavity (4) to close the opening (5), and wherein the reinforcing member (6) comprises a mixture of at least one fibrous cutting member having a length greater than or equal to 1 mm and a tackifier comprising an epoxy resin dissolved in a solvent.

Description

Technical Field

[0001] The present invention relates to an aircraft turbine, in particular a turbojet or turboprop engine. The present invention relates to a reinforcement for a composite turbine blade, a composite blade having such a reinforcement and a method for producing such a reinforcement and such a composite blade. Background Art

[0002] Aircraft typically include at least one turbine to provide propulsion.

[0003] The turbomachine includes at least one fan or propeller, at least one compressor, a combustion chamber, at least one turbine and an exhaust nozzle. For example, the turbomachine may include a low-pressure compressor, a high-pressure compressor, a high-pressure turbine and a low-pressure turbine. The high-pressure turbine rotates the high-pressure compressor via a high-pressure shaft, and the low-pressure turbine rotates the low-pressure compressor via a low-pressure shaft. The low-pressure turbine may also rotate the fan directly via the low-pressure shaft or via a speed reducer arranged between the low-pressure turbine and the fan, the speed reducer being rotated by the low-pressure shaft.

[0004] The fan comprises a hub and blades fixed to the hub, the fan blades being rotatable about the longitudinal axis of the turbine. A secondary flow rectifier may be arranged downstream of the fan. The rectifier comprises rectifier blades located downstream of the fan blades, the rectifier blades being fixed, i.e. rotationally fixed relative to the longitudinal axis of rotation of the fan blades.

[0005] In a ducted turbine or turbojet engine, the fan is housed in a fan casing upstream of the rest of the turbine.

[0006] In an unducted turbine or turboprop (or unducted fan or open rotor), the fan is an unducted propeller arranged outside the nacelle, in the airflow around the turbine. An unducted turbine may include two unducted and counter-rotating fans or propellers (referred to as "UnDucted Fan (UDF)"), or alternatively include an unducted single fan and a rectifier including a plurality of rectifier blades (referred to as "Unducted Single Fan (USF)". The fan may be arranged at the rear of the gas generator so that the fan is of the push type, or at the front of the gas generator so that the fan is of the pull type. An unducted turbine makes it possible to increase the bypass ratio very significantly without being affected by the mass of the casing or nacelle intended to surround the fan blades.

[0007] The turbine may be a twin-flow turbine in which the amount of air sucked in by the fan is divided into a mainstream that passes through at least one compressor, a combustion chamber and at least one turbine and a secondary flow coaxial with the mainstream. The bypass ratio of the turbine corresponds to the ratio of the mainstream flow rate to the secondary flow rate. Increasing the bypass ratio improves the performance of the turbine and reduces the fuel consumption rate of the turbine. This results in an increase in the diameter of the blades (particularly the fan blades and the associated stator blades) at equal engine thrust. This increase in size is even more important for ductless turbines, in which the blades are larger and the rotation speed is lower. Increasing the size of the blades results in an increase in the mass of the blades (particularly the stator blades), which is detrimental to the performance of the turbine.

[0008] In order to reduce the mass of the blade, the blade can be designed with an organic matrix composite material, which includes fiber reinforcements embedded in an organic matrix. In addition, the organic matrix can be partially hollow, so that only the structural part is reinforced.

[0009] like Figure 1 As shown, it is known from the prior art that the rectifier blades 100 of a ducted turbine extend radially between an inner platform and an outer platform, through which the blades 100 are fixed to the inner casing of the turbine, and through which the blades 100 are fixed to the outer casing of the turbine. Each blade 100 comprises a blade body made of a composite material consisting of a fiber reinforcement having a three-dimensional braid and densified by a matrix. The fiber reinforcement has an end portion comprising two sections 200, which are disconnected from each other until the free end of the fiber reinforcement. The blade 100 also includes a gap filler or a roving subcomponent in the form of an additional insert 300, which enables the free space at the joint between the sections 200 of the fiber reinforcement to be filled. The insert 300 can in particular be made of a shaped braid. Document FR 3063 514A1 describes such a rectifier blade, which also includes an additional insert having a π-shaped cross-section. Thus, the blades may be manufactured from a solid composite material rather than a metallic material such as titanium, and the increase in mass of the blades may be reduced.

[0010] However, the insert does not meet the new geometry and structural constraints of the composite blade, in particular the three-dimensional (3D) woven organic matrix composite blade of the secondary flow rectifier. In fact, the change in the target geometry of the additional insert, which must have a very significant thickness change, makes it unfeasible to manufacture the additional insert using known techniques (e.g., from a formed braid).

[0011] Furthermore, in ductless turbines, fixing the blades, in particular the stator blades, to the casing of the turbine only by the inner radial end of the blades at the blade root has the consequence that all forces are transmitted into the blade root region, which leads to high levels of stress in the composite material part of the blade root. The known additional inserts do not allow sufficient local reinforcement of the blade root region and therefore do not adequately limit the openings and stresses at the disconnected sections of the fiber reinforcement under tensile, compressive and bending biases. Furthermore, the known inserts made of braids have too low a rigidity and therefore do not allow sufficient increase of the overall stiffness of the blade, which leads to an increased risk of buckling and a degradation of the frequency arrangement of the rectifier. Summary of the invention

[0012] The object of the present application is to propose a reinforcement for a composite turbine blade which makes it possible to reduce the stresses exerted on the blade at its structural region and to limit the increase in the mass of the blade.

[0013] Another object of the present application is to propose a reinforcement for a composite turbine blade having a complex geometry and satisfactory mechanical resistance properties.

[0014] Another object of the present application is to propose a method for manufacturing such a reinforcement that is easy to implement and enables rapid production of reinforcements having complex geometries.

[0015] To this end, according to a first aspect, a reinforcement for a blade of a turbine is provided, the blade comprising a first shell layer and a second shell layer made of a composite material, the first shell layer and the second shell layer being connected to each other at the outer end of the blade, the first shell layer comprising a first inner end portion, the second shell layer comprising a second inner end portion, the first inner end portion and the second inner end portion being spaced apart from each other to define an inner cavity of the blade between the first inner end portion and the second inner end portion, the inner cavity leading to an opening at the inner end of the blade, the inner end being radially opposite to the outer end, wherein the reinforcement is suitable for being arranged in the inner cavity to close the opening, and wherein the reinforcement is suitable for being arranged in the inner cavity to close the opening, and wherein the reinforcement comprises a mixture of cut pieces of at least one fiber and a tackifier, the cut pieces having a length greater than or equal to 1 mm, the tackifier comprising an epoxy resin dissolved in a solvent.

[0016] Some preferred but non-limiting features of the reinforcement according to the first aspect are the following features, taken alone or in any technically possible combination:

[0017] - the cut pieces are obtained from prepreg tapes comprising carbon fibres, preferably the prepreg tapes are recycled;

[0018] - the tackifier comprises between 20 and 85% by weight of epoxy resin, preferably about 25% by weight of epoxy resin;

[0019] - the epoxy resin is PR520 resin, and the solvent is acetone;

[0020] the mixture comprises between 65% and 85% by weight of tackifier and between 15% and 35% by weight of chopped fibers, preferably about 75% by weight of tackifier and about 25% by weight of chopped fibers;

[0021] The cutting element has a length between 1 mm and 15 mm, for example between 3 mm and 6 mm.

[0022] According to a second aspect, the present application relates to a blade of a turbine, which blade includes a first shell layer and a second shell layer made of a composite material, the first shell layer and the second shell layer are connected to each other at the outer end of the blade, the first shell layer includes a first inner end portion, and the second shell layer includes a second inner end portion, the first inner end portion and the second inner end portion are spaced apart from each other to define an inner cavity of the blade between the first inner end portion and the second inner end portion, the inner cavity leads to an opening at the inner end of the blade, the inner end is radially opposite to the outer end, and the blade also includes a reinforcement according to the first aspect, the reinforcement having a size substantially corresponding to the size of the inner cavity at the opening, and the reinforcement is arranged in the inner cavity to close the opening.

[0023] Optionally, the bucket may further comprise a filling material arranged in the inner cavity and radially between the reinforcement and the outer end of the bucket.

[0024] According to a third aspect, the present application relates to a ductless turbine, the ductless turbine comprising:

[0025] -case;

[0026] a fan having a hub of the fan and peripheral blades of the fan integral with the hub of the fan, the hub of the fan having a downstream portion of the hub surrounded by the inner surface of the upstream portion of the housing and protruding from the upstream portion of the housing, the hub of the fan being rotatably mounted relative to the upstream portion of the housing about a longitudinal axis; and

[0027] - at least one rectifier blade according to the second aspect, located downstream relative to the peripheral blades of the fan, mounted on the outer surface of the upstream part of the casing at its inner end, the reinforcement being arranged at the inner end of the blade.

[0028] According to a fourth aspect, the present application relates to a method for manufacturing a reinforcement according to the first aspect for a blade of a turbomachine, the method comprising the following steps:

[0029] E1: cutting at least one fiber to obtain a cut piece having a length greater than or equal to 1 mm;

[0030] E2: The tackifier was prepared by dissolving the epoxy resin in a solvent;

[0031] E3: Mix the cut pieces and the tackifier;

[0032] E4: compacting the mixture; and

[0033] E5: The compacted mixture is dried to evaporate the solvent.

[0034] According to a fifth aspect, the present application relates to a method for manufacturing a blade according to the second aspect of a turbomachine, the method comprising the following steps:

[0035] A composite preform for manufacturing a composite blade, the preform comprising a first shell layer and a second shell layer made of composite material, the first shell layer and the second shell layer being connected to each other at an outer end of the blade, the first shell layer comprising a first inner end portion, the second shell layer comprising a second inner end portion, the first inner end portion and the second inner end portion being spaced apart from each other to define an inner cavity of the blade between the first inner end portion and the second inner end portion, the inner cavity leading to an opening at the inner end of the blade, the inner end being diametrically opposite to the outer end;

[0036] The reinforcement is manufactured by the method according to the fourth aspect, the reinforcement having substantially the same dimensions as the dimensions of the inner cavity at the opening;

[0037] placing a reinforcement in the inner cavity of the preform of the bucket to close the opening; and

[0038] Resin is injected into the assembly comprising the preform of the blade and the reinforcement. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Other features, objects and advantages will emerge from the following description, which is purely illustrative and non-limiting and should be read in conjunction with the accompanying drawings, in which:

[0040] Figure 1 A schematic perspective sectional view of a blade according to the prior art is shown.

[0041] Figure 2 A schematic perspective view of a reinforcement according to one embodiment is shown, the reinforcement having a second geometry different from the first geometry.

[0042] Figure 3a A schematic radial cross-sectional view of a bucket according to one embodiment is shown.

[0043] Figure 3b A schematic radial longitudinal cross-section of a bucket according to one embodiment is shown.

[0044] Figure 4 A schematic cross-sectional view of a stamping-type tool suitable for implementing a method for manufacturing a reinforcement according to one embodiment is shown.

[0045] Figure 5 A partial schematic perspective view of a bucket according to one embodiment is shown.

[0046] Figure 6 A schematic perspective view of an example of an unducted turbine including buckets according to one embodiment is shown.

[0047] Figure 7 is a block diagram illustrating a method for manufacturing a bucket according to one embodiment. DETAILED DESCRIPTION

[0048] Turbine

[0049] In the present application, upstream and downstream are defined relative to the normal flow direction of the gas through the fan 200 of the turbine 100, and the air flow flows from upstream to downstream in the turbine 100. The longitudinal axis X corresponds to the rotation axis of the fan 200. The radial axis is an axis perpendicular to the longitudinal axis X and passing through the longitudinal axis. The longitudinal direction and the radial direction correspond to the directions of the longitudinal axis and the radial axis X, respectively. The terms inner and outer are used with reference to the radial direction, respectively, so that the inner part or inner surface of the element is closer to the longitudinal axis X than the outer part or outer surface of the same element. The width direction L of the blade 1 generally corresponds to the longitudinal direction, the height direction R of the blade 1 corresponds to the radial direction at the blade 1, and the thickness direction Y of the blade 1 corresponds to the direction perpendicular to the width direction L and the height direction R of the blade 1.

[0050] The turbine 100 generally extends around the longitudinal axis X. The turbine 100 includes at least one fan 200 or propeller, an engine assembly 300 and an exhaust nozzle 108 from upstream to downstream in the direction of the gas flow, and the engine assembly includes at least one compressor, a combustion chamber and at least one turbine. For example, the engine assembly 300 of the turbine 100 may include a fan and a rectifier, a low-pressure compressor and a high-pressure compressor, a combustion chamber and a high-pressure turbine and a low-pressure turbine. The high-pressure turbine rotates the high-pressure compressor via a high-pressure shaft extending along the longitudinal axis X. The low-pressure turbine rotates the low-pressure compressor via a low-pressure shaft extending along the longitudinal axis X. The low-pressure turbine can also rotate the fan 200 directly via the low-pressure shaft or via a speed reducer arranged between the low-pressure turbine and the fan 200, and the speed reducer is rotated by the low-pressure shaft.

[0051] Each compressor and each turbine may include one or more stages, each stage being formed by a set of stationary blades or stator blade sections and a set of rotating blades or rotor blade sections. The stationary blades are fixed to the casing 101 of the turbine 100. The rotating blades of the low-pressure compressor and the low-pressure turbine are fixed to the low-pressure shaft. The rotating blades of the high-pressure compressor and the high-pressure turbine are fixed to the high-pressure shaft.

[0052] In operation, air flows through the rotating fan 200, and a first portion of the air flow, called the main flow, is directed through the low-pressure compressor and the high-pressure compressor, the main flow is compressed, and then sent to the combustion chamber. The hot combustion products from the combustion chamber are used to drive the high-pressure turbine and the low-pressure turbine and thus generate the thrust of the turbine 100, and the hot combustion products from the combustion chamber are discharged through the nozzle 108 located downstream of the engine assembly 300. The second portion of the air, called the secondary flow, is discharged from the rotating fan 200 around the housing 101 from upstream to downstream.

[0053] The blade 1 is a structural component of the turbine 100, which is intended to be integrated into a blade section of the turbine 100. The blade section comprises a hub which can be mounted rotatably relative to a casing 101 of the turbine 100 for a rotating blade section or fixedly relative to a casing 101 of the turbine 100 for a stationary blade section. The blade section also comprises a plurality of blades 1 fixed to the hub. The blades 1 extend substantially radially relative to the longitudinal axis X and can be distributed circumferentially around the longitudinal axis X.

[0054] The blade section may have a diameter, for example, greater than or equal to 150 cm, preferably greater than or equal to 200 cm, for example less than or equal to 400 cm. Thus, the blade 1 has a sufficient span, so that the blade 1 of the blade section comprises two outer shell layers 2, 3 made of composite material and delimiting an inner cavity 4. Thus, the blade 1 of the blade section preferably has a height greater than or equal to 50 cm, preferably greater than or equal to 70 cm, for example about 80 cm to 100 cm, for example less than or equal to 160 cm.

[0055] Figure 6 A non-limiting example is shown in which the turbine 100 is a ductless turbine whose rectifier comprises a blade 1 comprising a reinforcement 6 according to a particular embodiment. The turbine 100 comprises:

[0056] - housing 101;

[0057] a fan 200 having a hub 201 of the fan 200 and peripheral blades 202 of the fan 200 which are integral with the hub 201 of the fan 200, the hub 201 of the fan 200 having a downstream portion 203 of the hub 201 which is surrounded by the inner surface 102 of the upstream portion 103 of the housing 101 and projects from the upstream portion 103 of the housing 101, the hub 201 of the fan 200 being rotatably mounted relative to the upstream portion 103 of the housing 101 about the longitudinal axis X; and

[0058] - at least one rectifier blade 1, which is located downstream relative to the peripheral blades 202 of the fan 200, and is mounted on the outer surface of the upstream part 103 of the casing 101 at its inner end, and includes a reinforcement 6 as described below, which is arranged at the inner end of the blade 1.

[0059] The casing 101 of the turbine 100 carries a fan 200 on the upstream side of the casing. The peripheral blades 202 of the fan 200 are distributed on the hub 201 of the fan 200 about the longitudinal axis of rotation X upstream of the casing 101 of the turbine 100. The hub 201 of the fan 200 is capable of rotating about the longitudinal axis X on its own relative to the upstream part 103 of the casing 101. The turbine 100 comprises a motor assembly 300 downstream of the hub 201 of the fan 200 and in the casing 101, which rotates the hub 201 of the fan 200 and therefore the peripheral blades 202 of the fan 200 about the longitudinal axis X.

[0060] The rectifier blades 1 are located in a flow space of a secondary flow generated around the outer surface of the housing 101 downstream of the peripheral blades 202 of the fan 200 when the peripheral blades 202 of the fan 200 rotate around the longitudinal axis X.

[0061] The turbine 100 is of the ductless type, and each secondary flow rectifier blade 1 is fixed to the outer surface of the upstream part 103 of the casing 101 only at the inner end 11 of the blade or is movably mounted on the outer surface of the upstream part of the casing. The outer end 12 of the blade 1, which is radially opposite to the inner end 11, is exposed to the secondary flow without being mounted or fixed to the casing, and there is no casing or nacelle surrounding the rectifier blade 1 and the casing 101.

[0062] The engine assembly 300 is located in the casing 101. The air inlet is located between the upstream portion 103 of the casing 101 and the hub 201 of the fan 200, and is located downstream of the peripheral blades 202 of the fan 200. The straightener blade 1 has a shape configured to concentrate the secondary flow on the outer surface of the downstream portion 107 of the casing 101, which is located downstream of the outer surface of the upstream portion 103 of the casing 101. An outer attachment arm or an outer attachment device connects the casing 101 to the aircraft.

[0063] It should be understood that the reinforcement 6 may be a reinforcement 6 for a blade 1 of a turbine 100 of any type, such as an unducted turbine 100, such as an open rotor of the unducted fan (UDF) type including two unducted and counter-rotating fans, or an open rotor of the unducted single fan (USF) type including an unducted single fan and a rectifier. Alternatively, the reinforcement 6 may be a reinforcement 6 for a blade 1 of a ducted turbine 100, such as a turbojet engine including a ducted fan 200.

[0064] Furthermore, it should be understood that the reinforcement 6 can be a reinforcement 6 for any composite blade 1 of the turbine 100 that requires a thick reinforcement 6 or a geometry with progressive thickness, in particular for a partially hollow organic matrix composite blade 1 having a structural hollow area to be reinforced. Thus, the reinforcement 6 can be a reinforcement 6 for a composite blade 1 of any blade portion of the turbine 100, for example, a reinforcement 6 for a fan 200, a rectifier, a compressor and / or a turbine blade 1.

[0065] Wheel blade

[0066] The blade 1 comprises an aerodynamic profile blade 13 suitable for being arranged in an air flow to generate lift when the turbine 100 is in operation, and a root 14 configured to be fixed at an inner end 11 of the blade 1 to a rotating or fixed hub comprising a blade portion of the blade 1. Thus, the inner end 11 of the blade 1 corresponds to a mounting side of the blade 1.

[0067] The root portion 14 of the bucket 1 may be secured to a fixed or rotating hub portion of the bucket portion by fasteners which receive the root portion 14 of the bucket 1 and secure the root portion to the hub portion of the blade portion. Figure 5 An example of a fastener is shown by way of non-limiting example, which includes holes 210, 310 passing through the first inner end portion 21 and the second inner end portion 31 respectively in the radial direction R, and may include bolting or riveting in the holes, etc.

[0068] The root 14 of the blade 1 corresponds to the portion of the blade 1 that is located below the line Fs that delimits the flow space of the secondary flow of the turbine 100 or below the secondary streamline Fs. Therefore, the root 14 of the blade 1 is located in a radially inner position relative to the wall of the casing 101 of the turbine 100, which radially delimits the flow space of the secondary flow on the inside. In the ducted turbojet 100, the flow space of the secondary flow is the flow path of the secondary flow that is delimited on the inside by the wall of the casing 101 and on the outside by the wall of the outer casing of the turbojet 100, the casing 101 corresponding to the inner casing. In the open rotor 100, the flow space of the secondary flow is the space outside the open rotor 10, which is delimited on the inside by the wall of the casing 101.

[0069] The wall of the housing 101 may be formed by one or a group of inter-bucket platforms 1. The inter-bucket platform 1 may be formed integrally with the bucket 1 or it may be separate and attached to the bucket 1 of the bucket section at the junction between the root 14 and the blade 13 of the bucket 1. The inter-bucket platform 1 delimits the flow space of the secondary flow at the bucket section on the inside.

[0070] The aerodynamic profile blade 13 has a leading edge 8 and a trailing edge 9 connected by a pressure side wall and a suction side wall. The leading edge 8 of the blade 13 forms the upstream end of the blade 13 in the flow space. The leading edge of the blade corresponds to the front part of the aerodynamic profile, which faces the air flow and divides the air flow into a pressure side flow and a suction side flow. The leading edge 8 of the blade 13 is configured to extend opposite to the gas flow entering the turbine. The trailing edge 9 of the blade 13 corresponds to the rear part of the aerodynamic profile and forms the downstream end of the blade 13 in the flow space, where the pressure side flow and the suction side flow meet.

[0071] The blade 1 comprises a first shell layer 2 and a second shell layer 3, which are made of a composite material and are connected to each other at an outer end 12 of the blade 1. The first shell layer 2 and the second shell layer 3 extend substantially opposite to each other. The first shell layer 2 can form a pressure side wall of the blade 13, and the second shell layer 3 can form a suction side wall of the blade 13. The shell layers 2, 3 form an outer surface of the blade 1, which is located in the secondary air flow during operation of the turbine 100. The first shell layer 2 and the second shell layer 3 carry the leading edge 8 and the trailing edge 9 of the blade 1.

[0072] The first shell 2 and the second shell 3 of the blade 1 are made of a composite material comprising a fiber reinforcement densified by a matrix. The shells 2, 3 may be monolithic and made in one piece from a fiber preform of varying thickness. Alternatively, the fiber reinforcement may comprise a first shell 2 and a second shell 3, which are connected, for example, near the outer end 12 of the blade 1. The fiber reinforcement comprises a blade portion for forming an aerodynamic profile blade 13 and a root portion for forming a root 14 of the blade 1.

[0073] The fiber reinforcement may comprise a woven or knitted three-dimensional fiber arrangement. The fiber reinforcement is also made so that it comprises strands (i.e., any type of thin wire) extending continuously inside the blade 13 portion and inside the root 14 portion of the blade 1. Alternatively, the fiber reinforcement may comprise a laminated two-dimensional fiber arrangement. The fibers of the fiber reinforcement comprise at least one of the following materials: carbon (typically silicon carbide), glass, aramid, polypropylene and / or ceramic (typically oxide ceramic). The matrix typically comprises an organic (thermosetting, thermoplastic or elastomeric) matrix or a carbon matrix. For example, the matrix comprises a plastic material, which is typically a polymer, such as an epoxide, a bismaleimide or a polyimide.

[0074] The first shell 2 comprises a first inner end portion 21 and the second shell 3 comprises a second inner end portion 31. The first inner end portion 21 and the second inner end portion 31 are spaced apart from each other to delimit between them an inner cavity 4 of the blade 1 which opens into an opening 5 at an inner end 11 of the blade 1, the inner end 11 being diametrically opposite to the outer end 12.

[0075] The inner end 11 of the blade 1 corresponds to the mounting end of the first shell 2 and the second shell 3 on a rotating or fixed hub of a blade part comprising the blade 1. In particular in the case of a non-ducted turbine 100, the blade 1 may be fixed to the rotating or fixed hub of the blade part only at the inner end 11 of the blade, or in particular in the case of a ducted turbine 100, the blade may be fixed to the rotating or fixed hub of the blade part at both the inner end 11 of the blade and the outer end 12 of the blade.

[0076] The height of the blade 1 corresponds to the distance along the radial axis between the inner end 11 and the outer end 12 of the blade 1. The outer end 12 of the blade 1 corresponds to the tip of the blade 1. The height of the blade 13 corresponds to the distance along the radial axis between the inner end and the outer end of the blade 13. The height of the root 14 corresponds to the distance along the radial axis between the inner end and the outer end of the root 14. The outer end 12 of the blade 1 corresponds to the outer end of the blade 13, and the inner end 11 of the blade 1 corresponds to the inner end of the root 14. The inner end of the blade 13 may correspond to the outer end of the root 14.

[0077] The shells 2, 3 of the fiber reinforcement are separated by an inner cavity 4 which is open at the inner end of the blade 1, which makes it possible to further reduce the mass of the blade 1 compared to conventional blades 1. In the case where the shells 2, 3 are obtained by three-dimensional weaving and the shells are monolithic, the inner cavity 4 is obtained by producing a break in the fiber reinforcement between two consecutive warp yarn layers from a so-called non-break area (here including the head 12 of the blade 1) to the inner end 11 of the shells 2, 3 (at which the inner cavity 4 is open at the opening 5). For this purpose, at the break, the warp yarn strands of two consecutive layers of the fiber blank are not connected by weft yarn strands. Preferably, the break extends within the aerodynamic profile blade 13 and to the inner end of the root 14 of the blade 1.

[0078] In the blade portion of the fiber reinforcement, the inner cavity 4 does not open on the leading edge 8 or the trailing edge 9. Therefore, the portion of the fiber reinforcement forming the leading edge 8 and the trailing edge 9 is not disconnected. The leading edge 8 and / or the trailing edge 9 can be attached and fixed to the fiber reinforcement as described below in relation to the method for manufacturing the blade 1. On the other hand, in the root portion of the fiber reinforcement, the inner cavity 4 can open on the upstream edge and the downstream edge of the root 14 of the blade 1, which upstream edge and the downstream edge of the root 14 extend in the extension of the leading edge 8 and the trailing edge 9 of the blade 13, respectively. Therefore, the portion of the fiber blank forming the upstream edge and the downstream edge of the root 14 of the blade 1 can be disconnected.

[0079] For example, reference may be made to document EP2588758 in the name of the applicant for more details on producing the breaks.

[0080] The first inner end portion 21 and the second inner end portion 31 correspond to the portion of the shell 2, 3 which is located radially inside relative to the interruption formed in the fiber reinforcement. The first inner end portion 21 and the second inner end portion 31 may extend over the entire height of the root 14 of the blade 1 and over at least a portion of the height of the blades 13 of the blade 1, or even substantially over the entire height of the blades 13 of the blade 1 when the interruption is substantially located at the outer end 12 of the blade 1. Thus, the first inner end portion 21 and the second inner end portion 31 are suitable for defining together the outer wall of the root 14 and the outer wall of at least a portion of the blade 13 of the blade, so that the inner cavity 4 comprises the root portion and the blade portion. Thus, the inner cavity 4 extends over the entire height of the root 14 of the blade 1 and over at least a portion of the height of the blade 13 or even substantially over the entire height of the blade 13.

[0081] The first shell 2 and the second shell 3 can be moved 101 away from each other along the thickness direction Y of the blade 1 towards the inner end 11 of the blade 1. The inner cavity 4 is located radially outside relative to the opening 5 and therefore has a maximum thickness at the opening 5, i.e. at the inner end 11 of the blade 1.

[0082] The plate 10 may be fixed below and against the first inner end portion 21 and the second inner end portion 31, and the plate may be located below and against the opening 5 and the reinforcement 6. The plate 10 enables a connection to be formed between the first inner end portion 21 and the second inner end portion 31.

[0083] The blade 1 may be a variable pitch rectifier blade. The rectifier comprises a hub fixedly mounted relative to the housing 101 of the turbine 100 and is therefore non-rotating. The stator blade 1 extends substantially radially relative to the longitudinal axis X. The blade 1 then comprises an actuating mechanism for changing the pitch angle of the blade so as to adapt the performance of the turbine 100 to different flight phases. In addition, each blade 1 comprises a fastener or pivot arranged at the root 14 of the blade 1. The fastener is rotatably mounted relative to the hub about the pitch axis. More precisely, the fastener is rotatably mounted in a housing by a ball or other rolling element, which is arranged in the hub. Therefore, each root 14 of the rectifier blade 1 is pivotally mounted along the pitch axis and connected to a pitch change system, which is installed in the turbine 100.

[0084] Reinforcement

[0085] Figure 2 The reinforcement 6 (or "spar filler") shown as a non-limiting example in FIG. 4 is a subcomponent of the blade 1. The reinforcement 6 is suitable for being arranged in the inner cavity 4 to close the opening 5. Furthermore, the reinforcement 6 contributes to forming and / or compacting the three-dimensional woven shell.

[0086] The reinforcement 6 comprises a mixture of cut pieces of at least one fiber and a tackifier. The cut pieces may have a length greater than or equal to 1 mm. The tackifier may comprise an epoxy resin dissolved in a solvent.

[0087] The above-mentioned reinforcement 6 makes it possible to fill the opening 5 between the first inner end portion 21 and the second inner end portion 31 so as to correctly form a three-dimensional (3D) braided shell and to provide improved mechanical strength (in particular bending stiffness) at the inner end 11 of the blade 1, which is the area of ​​greatest stress, once the parts have been polymerized. The reinforcement 6 thus makes it possible to have a satisfactory compromise between stiffness and mass in order to improve the mechanical strength of the blade 1, for example compared to adding girders or to increasing the thickness of the composite outer shell 2, 3. The stiffness of the area situated at the inner end 11 of the blade 1 makes it possible to reduce the stresses in the composite outer shell 2, 3, compared to a solution in which the cavity is merely filled with foam or provided with an insert, as described in document FR 3 063 514 A1. The increase in stiffness also makes it possible to limit the movements of the outer end 12 of the blade 1.

[0088] The mixture of chopped fiber and tackifier makes it possible to produce a reinforcement 6 having a significant volume and profile, i.e. a complex geometry with large dimensional variations, in particular with large thickness variations over a reduced height. The reinforcement 6 can thus close the inner cavity 4 of the blade 1, in particular at its inner end 11, which is located at the attachment zone of the blade 1 to the casing 101 of the turbine 100.

[0089] Furthermore, the mixture of fiber chops and tackifier makes it possible to obtain a reinforcement having sufficient cohesion to ensure its function as a structural reinforcement of the blade 1. Simple fiber chops alone would not have such cohesion.

[0090] Furthermore, the mixture of fiber cut pieces and tackifier is simple and quick to produce.

[0091] Finally, the use of such a mixture, in particular one containing short fibers having a length greater than or equal to 1 mm, makes it possible to precisely control the composition of the reinforcement 6 obtained, for example the amount of fibers and the volume ratio of the fibers.

[0092] The reinforcement 6 may have a stiffness value greater than 15 (+ / - 5) GPa in the radial direction R of the blade 1 . The reinforcement 6 thus contributes to the overall stiffness of the blade 1 , limiting the risk of buckling and improving the frequency arrangement of the blade portion comprising the blade 1 .

[0093] The volume fraction of the fibers of the reinforcement 6 is preferably between 20% and 50%, for example between 30% and 45%, in order to ensure optimal mechanical properties of the reinforcement 6 .

[0094] The reinforcement 6 may have a size that substantially corresponds to the size of the inner cavity 4 of the blade 1 at the opening 5. Thus, the reinforcement 6 is arranged in the inner cavity 4 to close the opening 5. The reinforcement 6 may have a size that substantially corresponds to the size of the inner cavity 4 over the entire height of the reinforcement 6, and the reinforcement 6 is arranged in a portion of the inner cavity 4 to at least partially fill the inner cavity 4. More specifically, the reinforcement 6 may include a root portion arranged in the root portion of the inner cavity 4 and a blade portion arranged in the blade portion of the inner cavity 4. The root portion of the reinforcement 6 may have a size that substantially corresponds to the size of the root portion of the inner cavity 4, so that the root portion of the reinforcement 6 completely closes the root portion of the inner cavity 4. The blade portion of the reinforcement 6 may have a size that substantially corresponds to the size of a portion of the blade portion of the inner cavity 4, so that the blade portion of the reinforcement 6 partially closes the blade portion of the inner cavity 4.

[0095] The reinforcement 6 may have a downwardly flared shape, ie an inverted funnel shape. Thus, the shape of the reinforcement 6 substantially corresponds to the shape of the inner cavity 4 of the blade 1 at the end portions of the blade 1 which are separated from each other in the thickness direction Y of the blade 1 .

[0096] In the following, reference is made to chopped fibers. It should be understood that the cut piece can be produced in a single fiber or in a plurality of fibers, which are chopped to obtain the cut piece.

[0097] The fibers may be carbon fibers such as IM7 fibers or T1100 fibers. Alternatively, the fibers may be glass fibers. The fibers may be oversized fibers.

[0098] The cutouts may have a length between 1 mm and 15 mm, for example between 3 mm and 6 mm. Thus, the cutouts are even shorter, the fibers on which they are based can be shorter, and the composition of the reinforcement 6 can be controlled with better reproducibility.

[0099] The chopped fibers may be prepreg tapes comprising fibers, such as carbon fibers.

[0100] The cut fibers may be recycled fibers. The use of recycled and cut fibers of the reinforced subcomponent 6 of the structural component of the blade 1 of the turbine makes it possible to reduce the cost of the reinforcement 6 and to quickly manufacture the reinforcement 6 with a complex shape. The recycled fibers may be, for example, fibers from the ends of reels, for example fibers from the ends of reels that were not used at the end of a weaving activity, or fibers from waste of a braided preform of the blade 1, for example fibers from surface wire cutting ("trimming") of a braided preform of the blade 1, etc.

[0101] Alternatively, the cut fibers may be new fibers. The use of new fibers may make it possible to adjust and improve the mechanical properties of the reinforcement 6 according to the desired properties.

[0102] The tackifier may include 20% to 85% by mass of epoxy resin and 15% to 80% by mass of solvent, preferably about 25% by mass of epoxy resin and about 75% by mass of solvent. This mass ratio of about 25% by mass of epoxy resin and about 75% by mass of solvent enables to obtain a tackifier with the best performance for manufacturing the reinforcement 6. When the proportion of epoxy resin is increased to about 85%, the cohesion of the mixture of tackifier and fiber cut pieces is still ensured.

[0103] The epoxy resin may be, for example, a PR520, DGEBA or DGEBF resin. The PR520 resin has good tackifying properties. The epoxy resin, in particular the PR520 resin, is dissolved in a solvent to obtain a tackifier. In fact, at room temperature, the PR520 resin has a high viscosity, which makes it difficult or even impossible to mix undissolved PR520 resin with the fiber cut pieces. Furthermore, it is not necessary to provide a large amount of epoxy resin to the fiber cut pieces in order to ensure the cohesion of the mixture. Therefore, dissolving the epoxy resin in a solvent does not impair the cohesion of the reinforcement 6.

[0104] The solvent may be acetone or any other solvent that is compatible with the epoxy resin used, that is to say that enables the epoxy resin to be dissolved. The mixture of PR520 resin and acetone makes it possible to obtain a tackifier with satisfactory properties. In particular, the tackifier may comprise about 25% by mass of PR520 resin and about 75% by mass of acetone to obtain a tackifier with optimal properties for manufacturing the reinforcement 6.

[0105] The mixture may include between 65% and 85% by weight of tackifier and between 15% and 35% by weight of chopped fibers, preferably about 75% by weight of tackifier and about 25% by weight of chopped fibers. The ratio of about 75% by weight of tackifier to about 25% by weight of chopped fibers enables an ideal mixture fabric to be obtained for manufacturing the reinforcement 6.

[0106] The reinforcement 6 is radially delimited by an inner edge and an outer edge opposite the inner edge. The distance (e.g. average distance) between the inner edge and the outer edge of the reinforcement 6 corresponds to the height of the reinforcement 6. The inner edge of the reinforcement 6 may be arranged at the opening 5. The reinforcement 6 may extend between the inner edge and the outer edge over at least a portion of the height of the root 14 of the blade 1 and, where appropriate, over at least a portion of the height of the blade 1.

[0107] The height of the reinforcement 6 may be greater than 3% of the height of the blade 1, for example greater than 5% of the height of the blade 1, for example greater than 10% of the height of the blade 1. The height of the reinforcement 6 may be less than 50% of the height of the blade 1, for example less than 25% of the height of the blade 1, for example less than 15% of the height of the blade 1, for example less than 10% of the height of the blade 1. As a non-limiting example, the height of the reinforcement 6 may be between 5% and 15% of the height of the blade 1.

[0108] In the first embodiment, the reinforcement 6 extends below the secondary streamline Fs, i.e., at a position radially more inside than the secondary streamline Fs, which defines the flow space of the secondary flow of the turbine 100. Therefore, the reinforcement 6 extends only in a portion of the root 14 of the blade 1. Therefore, the stiffness of the blade 1 is increased at the root 14 of the blade 1, and the mass impact of the blade 1 due to the presence of the reinforcement 6 is limited. For example, the height of the reinforcement 6 can be less than 50 mm. The height of the reinforcement 6 can be less than about 10% of the height of the blade 1, or even less than about 5% of the height of the blade 1, or even less than about 3% of the height of the blade 1.

[0109] In the second embodiment, the reinforcement 6 extends in a portion of the root 14 of the blade 1 and in a portion of the blade 13. The upstream end of the outer edge of the reinforcement 6 (i.e., the end of the reinforcement located on the leading edge 8 side of the blade 1) extends above the secondary streamline Fs at the leading edge 8 of the blade 1, i.e., at a position radially more outward than the secondary streamline Fs. The downstream end of the outer edge of the reinforcement 6 (i.e., the end of the reinforcement located on the trailing edge 9 side of the blade 1) extends below the secondary streamline Fs at the trailing edge 9 of the blade 1, i.e., at a position radially more inward than the secondary streamline Fs. Therefore, the stiffness of the blade 1 is increased at the root 14 of the blade 1 and at the leading edge 8 of the blade 1, most of the stress is located at the root of the blade and at the leading edge of the blade, while limiting the mass impact of the blade 1 including the reinforcement 6. For example, the height of the reinforcement 6 may be between 50 mm and 100 mm. The height of the reinforcement 6 may be between about 3% and about 20% of the height of the blade 1 , for example between about 10% and about 15% of the height of the blade 1 .

[0110] In a third embodiment, the reinforcement 6 extends in the root 14 of the blade 1 and in at least a portion of the blade 13 of the blade 1, the outer edge of the reinforcement 6 extending radially above the secondary streamline Fs, i.e. at a position radially further outward than the secondary streamline Fs. Thus, the reinforcement 6 extends in the root 14 of the blade 1 over the entire height of the root 14 of the blade 1, and further in the blade 13 of the blade 1 over at least a portion of the height of the blade 13 or even substantially over the entire height of the blade 13. Thus, the stiffness of the blade 1 is further increased both at the root 14 of the blade 1 and at the leading edge 8 and the trailing edge 9 of the blade 13. For example, the height of the reinforcement 6 may be greater than 100 mm. The height of the reinforcement 6 may be greater than about 5% of the height of the blade 1, or even greater than about 10% of the height of the blade 1, or even greater than about 20% of the height of the blade 1, or even greater than about 50% of the height of the blade 1.

[0111] Filling material

[0112] The blade 1 may further comprise a filling material 41 arranged in the inner cavity 4 radially between the reinforcement 6 and the outer end 12 of the blade 1. Thus, the filling material 41 extends radially above the reinforcement 6 at a distance from the opening 5, i.e. radially further outside than the reinforcement 6. The filling material 41 may be arranged against the reinforcement 6, i.e. in contact with the outer edge of the reinforcement 6.

[0113] The density of the filler material 41 may be lower than the density of the reinforcement 6 and / or lower than the density of the composite material of the outer shell layers 2, 3, and the filler material 41 is inserted into the hollow area of ​​the blade 1, which is not a structural area and therefore does not need to be reinforced. The filler material 41 may have, for example, a density of about 100 kg / m 3 The filling material 41 may be integrated into one or more filling components, each of which is suitable for being arranged in the inner cavity 4 of the blade 1 .

[0114] The filling material 41 may be, for example, a foam, such as a foam of organic (polyether acrylimide, polyethylene terephthalate (PET), polyvinyl chloride (PVC), polyetherimide (PEI), polyethylene, carbon, polyisocyanurate, polyurethane, etc.) or of metallic origin (in particular, aluminum alloy), or the filling material 41 may be The honeycomb section may be made of a nylon type (comprising aramid fibers calendered into sheets and covered with a phenolic resin), Kevlar fibers, fiberglass, or aluminum.

[0115] In particular when the reinforcement 6 extends through the entire root portion of the inner cavity 4 and in a portion of the blade portion of the inner cavity 4, the filling material 41 may be arranged only in the blade portion of the inner cavity 4. In particular when the reinforcement 6 extends only in a portion of the root portion of the inner cavity 4, the filling material 41 may extend only in a portion of the blade portion of the inner cavity 4, or only in the entire blade portion of the inner cavity 4. The filling material 41 makes it possible to reinforce the outer shell layers 2, 3 and / or give the outer shell layers 2, 3 the final shape of the blade 13, with minimal impact on the mass of the blade 1.

[0116] Method for producing a reinforcement

[0117] The method for manufacturing a reinforcement 6 as described above for a blade 1 of a turbine 100 as described above comprises the following steps:

[0118] E1: cutting at least one fiber to obtain a cut piece having a length greater than or equal to 1 mm;

[0119] E2: The tackifier was prepared by dissolving the epoxy resin in a solvent;

[0120] E3: Mix the cut pieces and the tackifier;

[0121] E4: compacting the mixture; and

[0122] E5: The compacted mixture is dried to evaporate the solvent.

[0123] The method described hereinafter generally has the same advantages as those described with respect to the reinforcement 6 described above. In particular, the method enables rapid production of reinforcements 6 having complex geometries.

[0124] Furthermore, the method is particularly simple to implement since it does not require a cutting step or the use of an autoclave.

[0125] The characteristics of the fiber properties, tackifier composition, composition of the mixture of cut pieces and tackifier described above with respect to the reinforcement 6 can be used independently in the steps of the method described above. In particular, the fibers cut in step E1 can be carbon fibers or glass fibers, and can be recycled fibers or new fibers. The cut pieces obtained at the end of step E1 can have a length between 1 mm and 15 mm, for example, between 3 mm and 6 mm. The epoxy resin used to prepare the tackifier in step E2 can be PR520 resin. The solvent used to prepare the tackifier in step E2 can be acetone. The tackifier prepared in step E2 can include an epoxy resin with a mass of between 20% and 85% and a solvent with a mass of between 15% and 80%, preferably including an epoxy resin with a mass of about 25% and a solvent with a mass of about 75%. The mixture of cut pieces and tackifier prepared in step E3 may include between 65% and 85% by weight of tackifier and between 15% and 35% by weight of cut fibers, preferably about 75% by weight of tackifier and about 25% by weight of cut fibers.

[0126] Step E1 may comprise cutting one or more fibers to obtain fiber cut pieces.Step E1 may correspond to the simultaneous cutting of a plurality of fibers.

[0127] Step E2 of preparing the tackifier may include a sub-step E21 of providing an epoxy resin and a sub-step E22 of providing a solvent, such as Figure 7 This is shown by way of non-limiting example.

[0128] The step E3 of mixing the cut pieces and the tackifier may include mixing the cut fibers and the solvent in the mass ratio as described above. The mixing of the cut pieces and the tackifier in step E3 enables the tackifier to be incorporated into the cut pieces of fibers.

[0129] In a first exemplary embodiment of step E3, the fiber cut pieces are arranged in a container. Before mixing or gradually during mixing, a tackifier is poured into the container. The set of cut pieces and the tackifier are mixed in the container until the tackifier is completely absorbed by the fiber cut pieces. For small volumes, mixing can be done manually. For industrial applications, a mixing robot can be used to lock key parameters such as mixing tools, rotation speed, mixing time, etc., thereby improving the repeatability of the mixture.

[0130] In a second exemplary embodiment of step E3 , a tackifier is sprayed onto the fiber cut pieces.

[0131] To implement the compaction step E4, the mixture of fiber cut pieces and tackifier is deposited in the cavity 410 of the forming and / or compacting and / or drying tool 400. The tool 400 may comprise a mold forming the cavity 410. The pasty and viscous nature of the mixture of fiber cut pieces and tackifier enables the fibers to be evenly distributed in the cavity 410 of the tool 400, which comprises a cavity 410 with a complex geometry. In particular, the cavity 410 of the mold of the tool 400 may have an inverse shape with respect to the reinforcement 6 to be produced, the dimensions of which correspond substantially to the dimensions of the following portion of the inner cavity 4 of the blade 1 in which the reinforcement 6 is intended to be arranged. The mixture of fiber cut pieces and tackifier is deposited in the cavity 410 so as to fill the cavity 410, thereby producing a reinforcement 6 with the desired geometry. The tool 400 may then be closed in preparation for the compaction step E4.

[0132] The compaction step E4 makes it possible to compact the mixture of cut fiber pieces and tackifier arranged in the cavity 410 in order to obtain the desired final dimensions of the reinforcement 6 and to ensure the cohesion of the mixture. The tool 400 may be of the box type comprising different inserts to be closed to ensure compaction. Alternatively, the tool 400 may be of the die or punch type, such as Figure 4 4. The punch then compacts the fibers uniformly. The mold forming the cavity 410 may be tightened, for example, under pressure.

[0133] The compacted mixture is then soaked in a solvent. A drying step E5 accelerates the evaporation of the solvent to obtain a hardened part. The drying step E5 may include an oven drying cycle. The drying step E5 may be implemented in the tool 400. For a reinforcement with a fiber volume ratio of about 40% and a cavity of about 95 cubic centimeters, the drying step E5 may be carried out at a temperature of about 120° C. for a period of about 3 hours. The drying cycle of step E5 may be adjusted according to the nature of the fiber cut pieces used to make the reinforcement 6, the composition of the tackifier and the mass ratio of the mixture of the fiber cut pieces and the tackifier.

[0134] The method may also comprise a step E6 of demoulding the mixture compacted during step E4 and dried during step E5 to remove the compacted and dried mixture from tool 400. Tool 400 has previously been covered with Teflon and the compacted and dried mixture may be demoulded during step E6 by removing the gaskets one by one.

[0135] The compacted and dried mixture comprises interspaces that the resin can fill during the co-injection carried out in step E11 described below. Depending on the resin used, the compacted and dried mixture may partially polymerize, which makes it possible to increase the rigidity of the mixture, or the compacted and dried mixture may not polymerize. In the case of using a PR520 resin to prepare the tackifier during step E2, the compacted and dried mixture obtained is partially polymerized and in particular sufficiently rigid to be handled and covered as a sub-component of the blade 1. Moreover, the partial polymerization of the compacted and dried mixture makes it possible to obtain a good interface during the co-injection of the reinforcement 6 with the remaining elements of the blade 1 during step E11. In the case of using an epoxy resin without a hardener to prepare the tackifier in step E2, the compacted and dried mixture obtained is not polymerized and is therefore less rigid, but is still sufficiently rigid to be able to be used as a sub-component of the blade 1.

[0136] Method for manufacturing a blade

[0137] The blade 1 as described above can be obtained using the following manufacturing method, which is Figure 7 1 is shown as a non-limiting example. However, this is not limiting and other methods for manufacturing such a blade 1 can be considered. The method for manufacturing the blade 1 may include the following steps:

[0138] During a step E0, a composite preform of a composite blade 1 is manufactured, said preform comprising a first outer shell 2 and a second outer shell 3 made of composite material, the first and second outer shells being connected to each other at an outer end 12 of the blade 1, the first shell 2 comprising a first inner end portion 21, the second shell 3 comprising a second inner end portion 31, the first inner end portion 21 and the second inner end portion 31 being spaced apart from each other so as to define an inner cavity 4 of the blade 1 between the first and second inner end portions, the inner cavity opening into an opening 5 at an inner end 11 of the blade 1, the inner end 11 being diametrically opposite the outer end 12;

[0139] The reinforcement 6 is manufactured by the method for manufacturing the reinforcement 6 as described above, the reinforcement 6 having substantially the same dimensions as the dimensions of the inner cavity 4 at the opening 5;

[0140] The reinforcement 6 is arranged in the inner cavity 4 of the preform of the blade 1 so as to close the opening 5 ; and during a step E11 , resin is injected into the assembly comprising the preform of the blade 1 and the reinforcement 6 .

[0141] This method enables the reinforcement 6 to be injected simultaneously with the rest of the blade 1. The reinforcement 6 is thus bonded to the shells 2, 3 of the blade 1 without the use of glue or surface treatment. Furthermore, the reinforcement 6 ensures good compaction of the shells 2, 3 of the blade 1 in the radius during forming, thereby ensuring the desired fiber volume ratio in the radius.

[0142] The fiber preform of the blade 1 can be manufactured during step E0, for example, by three-dimensional weaving or knitting. In the exemplary embodiment, the fiber blank is woven in three dimensions and the interruptions are produced to obtain the two shells 2, 3 and the inner cavity 4, as described above with respect to the blade 1. The two shells 2, 3 are integral at the head 12 of the blade 1, at the leading edge 8 and at the trailing edge 9 of the blade 13. The inner cavity 4 opens at the root 14 of the blade 1 and extends into the blade 13.

[0143] The manufacture of the preform of the blade 1 may comprise a step of cutting (“trimming”) the surface filaments of the woven preform, in particular when the fils of the preform remain non-woven and protrude.

[0144] A filling material 41 may be arranged in the inner cavity 4 after the reinforcement 6 is arranged in the inner cavity 4 or before the reinforcement is arranged in the inner cavity.

[0145] During step E10, the reinforcement 6 may be arranged in the inner cavity 4, for example pressed onto the filling material 41. The reinforcement 6 closes the inner cavity 4 of the bucket 1 at the opening 5.

[0146] The assembly formed by the fiber preform, the filling material 41 and the reinforcement 6 can then be arranged in an injection mold. The injection mold can have an inverse shape with dimensions substantially corresponding to the dimensions of the final molded blade 1, i.e. the desired blade 13 and root 14 of the blade 1. The mold is then closed, for example by a wall closing the opening 5, to carry out the injection.

[0147] The resin forming the “matrix” of the composite material injected during step E11 is generally a plastic material. The resin is injected into the injection mould to impregnate the fibre reinforcements of the shells 2 , 3 , the filling material 41 and the reinforcements 6 .

[0148] The injection of the matrix can be implemented by an injection technique of the RTM or VARR™ type. In the case of a plastic material, the injected matrix is, for example, a thermosetting liquid composition containing an organic precursor of the matrix material. The organic precursor is usually in the form of a polymer (e.g. a resin), which may be diluted in a solvent. In a manner known per se, the plastic material is then heated to cause polymerization of the plastic material, for example by crosslinking. For this purpose, the injection mold is arranged in an oven. The component obtained can then be demoulded from the injection mold.

[0149] Alternatively, the leading edge 8 may be inserted in the upstream portion of the preform of the blade 1. The outer layer forming the leading edge 8 is then arranged on the preform to achieve the mating of the leading edge 8. The leading edge 8 then passes through an autoclave to be bonded to the preform.

[0150] Then, one or more steps of various finishing and / or finishing can be implemented. For example, the demoulded part can be cut by machining to remove the excess length and obtain a part with the desired shape, despite the possible shrinkage of the fibers of the fiber reinforcement during the polymerization of the plastic material. The sacrificial thickness is in particular machined to obtain a reference surface for the root 14 of the blade 1. Through-channels are also machined in the shells 2, 3 to accommodate the fixing system. Where appropriate, counterbores are also machined around the through-channels.

Claims

1. A reinforcement (6) for a blade (1) of a turbine (100), the blade (1) comprising a first outer shell layer (2) and a second outer shell layer (3) made of a composite material, the first outer shell layer and the second outer shell layer being connected to each other at an outer end (12) of the blade (1), the first shell layer (2) comprising a first inner end portion (21), the second shell layer (3) comprising a second inner end portion (31), the first inner end portion (21) and the second inner end portion (31) being spaced apart from each other to define an inner cavity (4) of the blade (1) between the first inner end portion and the second inner end portion, the inner cavity leading to an opening (5) at an inner end (11) of the blade (1), the inner end (11) being radially opposite to the outer end (12), wherein: The reinforcement (6) is suitable for being arranged in the inner cavity (4) to close the opening (5), and wherein the reinforcement (6) comprises a mixture of cut pieces of at least one fiber and a tackifier, the cut pieces having a length between 1 mm and 15 mm, the tackifier comprising an epoxy resin dissolved in a solvent.

2. The reinforcement member (6) according to claim 1, wherein: The cut pieces are obtained from a prepreg tape comprising carbon fibres, preferably wherein the prepreg tape is recycled.

3. A reinforcement member (6) according to claim 1 or 2, wherein: The tackifier comprises between 20% and 85% by weight of epoxy resin, preferably about 25% by weight of epoxy resin, wherein the epoxy resin is preferably PR520 resin, and the solvent is preferably acetone.

4. A reinforcement (6) according to any one of claims 1 to 3, wherein: The mixture comprises between 65 and 85% by weight of tackifier and between 15 and 35% by weight of chopped fibers, preferably about 75% by weight of tackifier and about 25% by weight of chopped fibers.

5. A reinforcement (6) according to any one of claims 1 to 4, wherein: The cutting element has a length between 3 mm and 6 mm.

6. A blade (1) of a turbine (100), the blade comprising a first outer shell layer (2) and a second outer shell layer (3) made of a composite material, the first outer shell layer and the second outer shell layer being connected to each other at an outer end (12) of the blade (1), the first shell layer (2) comprising a first inner end portion (21), the second shell layer (3) comprising a second inner end portion (31), the first inner end portion (21) and the second inner end portion (31) being spaced apart from each other to define an inner cavity (4) of the blade (1) between the first inner end portion and the second inner end portion, the inner cavity leading to an opening (5) at an inner end (11) of the blade (1), the inner end (11) being radially opposite to the outer end (12), the blade (1) further comprising a reinforcement (6) according to claim 1 or 2, wherein: The reinforcement (6) has a size substantially corresponding to the size of the inner cavity (4) at the opening (5), and the reinforcement (6) is arranged in the inner cavity (4) to close the opening (5).

7. The blade (1) according to claim 6, further comprising a filling material (41) arranged in the inner cavity (4) and radially between the reinforcement (6) and the outer end (12) of the blade (1).

8. A ductless turbine (100), comprising: - a housing (101); - a fan (200), the fan comprising a hub (201) of the fan (200) and peripheral blades (202) of the fan (200) which are integral with the hub (201) of the fan (200), the hub (201) of the fan (200) comprising a downstream portion (203) of the hub (201), the downstream portion being surrounded by an inner surface (102) of an upstream portion (103) of the housing (101) and protruding from the upstream portion (103) of the housing (101), the hub (201) of the fan (200) being rotatably mounted relative to the upstream portion (103) of the housing (101) about a longitudinal axis (X); and - At least one rectifier blade (1) according to claim 6 or 7, the blade (1) being located downstream relative to the peripheral blades (202) of the fan (200), the blade (1) being mounted on the outer surface of the upstream part (103) of the casing (101) at the inner end of the blade (1), and the reinforcement (6) being arranged at the inner end of the blade (1).

9. A method for manufacturing a reinforcement according to any one of claims 1 to 5 for a blade (1) of a turbomachine (100), the method comprising the following steps: E1: cutting at least one fiber to obtain a cut piece having a length greater than or equal to 1 mm; E2: The tackifier was prepared by dissolving the epoxy resin in a solvent; E3: mixing the cut pieces and the tackifier; E4: compacting the mixture; and E5: The compacted mixture is dried to evaporate the solvent.

10. A method for manufacturing a blade (1) according to claim 6 or 7 for a turbomachine (100), the method comprising the following steps: A composite material preform for manufacturing (E0) a composite material blade (1), the preform comprising a first shell layer (2) and a second shell layer (3) made of composite material, the first shell layer and the second shell layer being connected to each other at an outer end (12) of the blade (1), the first shell layer (2) comprising a first inner end portion (21), the second shell layer (3) comprising a second inner end portion (31), the first inner end portion (21) and the second inner end portion (31) being spaced apart from each other to define an inner cavity (4) of the blade (1) between the first inner end portion and the second inner end portion, the inner cavity leading to an opening (5) at an inner end (11) of the blade (1), the inner end (11) being radially opposite to the outer end (12); manufacturing a reinforcement (6) by a method according to claim 9, said reinforcement (6) having substantially the same dimensions as the dimensions of said inner cavity (4) at said opening (5); Arranging the reinforcement (6) in the inner cavity (4) of the preform of the blade (1) to close the opening (5); and Resin is injected ( E11 ) into the assembly comprising the prefabricated part of the blade ( 1 ) and the reinforcement ( 6 ).

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