METHOD FOR MANUFACTURING A BLADE FOR AN AIRCRAFT TURBOMACHINE

Abstract

A method of manufacturing a blade (30) for an aircraft turbomachine, comprising: a) producing a three-dimensional preform by weaving fibers, b) solidifying the preform with a polymerizable resin to form a body (36) of the blade, and c) forming serrations (35), this formation being carried out by mounting the body (36) of the blade in a mold (38) comprising an imprint (40) of the serrations (35) to be formed, and by thermocompressing a material (42) in the mold (38), this material (42) being intended to be secured to the body (36) of the blade and to adopt the shape of the imprint (40), the assembly formed by the body (36) of the blade and the secured material (42) forming the blade (32) of the blade (30). Figure for abstract: Figure 4

Description

Title of the invention: METHOD FOR MANUFACTURING A BLADE FOR AN AIRCRAFT TURBOMACHINE Technical field of the invention

[0001] The present invention relates to a method of manufacturing a blade for an aircraft turbomachine, as well as a blade obtained by this method. Technical approval plan

[0002] The state of the art includes in particular document FR-A1-3 073 017.

[0003] An aircraft turbomachine conventionally comprises a gas generator which drives at least one propeller. The gas generator comprises at least one compressor, a combustion chamber and at least one turbine. The rotor or one of the rotors of the gas generator is connected to the rotor of the propeller for its rotational drive.

[0004] A propeller can be shrouded. This is the case for a fan in a turbomachine of the turbojet or turbofan type, for example.

[0005] A propeller can be unducted. This is the case for a turboprop, for example.

[0006] A propeller comprises a hub and an annular row of blades which are mounted all around the hub. The blades may be fixed and therefore have a fixed angular position around their axes of extension. Alternatively, the blades may be variable pitch, that is, they are capable of being moved in rotation around axes called pitch axes, which generally extend along the axes of extension of the blades. The pitch axes may be radial axes relative to the axis of rotation of the propeller.

[0007] A blade conventionally comprises a blade having a lower surface and an upper surface, as well as a leading edge and a trailing edge. It may further comprise a platform connected to one end of the blade and defining the blade's pitch axis. The platform is generally mounted in an orifice in the hub and centered and guided in rotation in this orifice around the pitch axis.

[0008] It is known to produce such blades from metallic, ceramic or composite material. A well-known composite material for one comprises a body based on woven carbon fibers which is embedded in a polymer matrix based on epoxy for example. The leading edge of the blade can be reinforced by a bonded metal shield.

[0009] The evolution of the performance of turbomachines tends towards the increase of their bypass ratio, which is mainly achieved by the increase of the diameter of the propellers and therefore of the length and mass of their blades.

[0010] In addition, a so-called slow and high bypass ratio propeller comprises a reduced number of blades whose chord is increased to improve the propulsive efficiency of the turbomachine.

[0011] In the case of a shrouded propeller, the nacelle surrounding the propeller includes an internal acoustic treatment which makes it possible to reduce noise emissions outside the turbomachine.

[0012] In the case of an unducted propeller, other solutions must be found for reducing propulsive noise. This is particularly the case for the turbomachine illustrated in [Fig.l]. This turbomachine 10 comprises a propeller 12 upstream, which comprises variable-pitch rotor blades 14, and a rectifier 16 downstream, which comprises stator blades 18 also with variable pitch.

[0013] To remedy the problem of noise emission, a noise reduction technology already known on fans and inspired in particular by the wings of nocturnal birds of prey consists of arranging serrations 20 on the trailing edges of the rotor blades 14 or on the leading edges of the stator blades 18 (figures 2 and 3).

[0014] Serrations 20 of a leading or trailing edge are formed by alternating teeth 20a and hollows 20b along this edge. The serrations can cause variations in the chord of the blade as a function of the radial height, with variable thicknesses and a very thin trailing or leading edge.

[0015] The teeth 20a are defined so as to reduce noise in the average emission spectrum without unduly worsening other frequencies at other engine speeds.

[0016] The angular setting of the blades implies variable acoustics of the blades depending on the engine speed and the orientation of the blades.

[0017] It has been found that, in most engine speeds, the serrations make it possible to reduce the noise emitted. However, a significant increase in the noise emitted has also been observed when the blades are set in reverse or thrust reversal mode. In the case of a rotor blade, the serrations of the trailing edge are oriented upstream in reverse mode, which greatly disrupts the aerodynamic flow. The serrations are then counterproductive.

[0018] The thrust reversal phase is a phase which, on the contrary, should be as quiet as possible because it generally takes place in a nearby urban environment.

[0019] Another disadvantage of the prior art is linked to the fact that the serrations cannot be manufactured with the same material as the woven blades because the serrations are too thin, and they would be too fragile and in particular brittle.

[0020] The present invention provides a solution to at least some of the problems of the prior art, which is simple, effective and economical. Summary of the invention

[0021] The invention relates to a method for manufacturing a blade for an aircraft turbomachine, this blade comprising a blade having a lower surface and an upper surface, as well as a leading edge and a trailing edge, the leading or trailing edge comprising serrations (35) formed by an alternation of teeth and hollows along this edge,

[0022] the method comprising:

[0023] a) the production of a three-dimensional preform by weaving fibers, and

[0024] b) solidifying the preform with a polymerizable resin,

[0025] characterized in that steps a) and b) make it possible to produce a body of the blade without the clamps, and the method further comprises:

[0026] c) the formation of the serrations, this formation being carried out by mounting the body of the blade in a mold comprising an imprint of the serrations to be formed, and by thermocompressing a material in the mold, this material being intended to become integral with the body of the blade and to adopt the shape of the imprint, the assembly formed by the body of the blade and the integral material forming the blade of the vane.

[0027] The invention thus proposes to produce the serrations after the preform has solidified with the resin. The serrations are produced by thermocompression, that is to say by a treatment combining an increase in temperature and pressure. A material is used specifically for producing the serrations and is thermocompressed with the solidified preform, called the blade body, so that it matches the shape of the mold and therefore adopts a serrated shape. Thermocompression also makes it possible to secure the material to the preform.

[0028] The method according to the invention may comprise one or more of the following characteristics, taken in isolation from one another, or in combination with one another: • the method comprises, between steps b) and c), a step i) of preparation or treatment of the surface of the body of the blade intended to be secured to the material;

[0029] — said preparation or said surface treatment is chosen from sandblasting, plasma treatment and a glue film; • the material extends over the body of the blade, only along the edge of the blade containing the serrations; • the material is secured to the body of the blade by chemical adhesion and / or mechanical anchoring; • mechanical anchoring is achieved by filling the housings of the blade body with the material during step c); • the method comprises, between steps b) and c), a step i) of forming the housings, for example by machining the blade body; • the housings each have a general dovetail shape; • the method further comprises, after step c), a step d) of covering the blade with a consolidation layer which covers both the body of the blade and the material; • the consolidation layer is made of polyurethane; • during step c), the mold is heated to a temperature above 100°C, and for example between 120 and 150°C; • during step c), thermocompression is carried out at a pressure greater than 50 bars, and for example between 70 and 140 bars; • the material comprises at least one thermosetting polymer; • the material includes fillers; • the fillers include fibers, particularly carbon.

[0030] The invention also relates to a blade for an aircraft turbomachine, this blade being obtained by a method as described above.

[0031] Advantageously, the blade comprises a blade comprising a lower surface and an upper surface, as well as a leading edge and a trailing edge, the leading or trailing edge comprising serrations formed by alternating teeth and hollows along this edge, the blade comprising a blade body and a material secured to the blade body and defining said serrations, the blade body comprising a three-dimensional preform produced by weaving fibers and embedded in a resin.

[0032] Both the resin and the material may be epoxy based. Brief description of the figures

[0033] Other characteristics and advantages will emerge from the following description of a non-limiting embodiment of the invention with reference to the appended drawings in which:

[0034] [Fig-1] [Fig.l] is a schematic perspective view of a turbomachine with unducted propeller and an unducted stator, the propeller and stator having variable pitch blades;

[0035] [Fig.2] [Fig.2] is a schematic view of a rotor or propeller blade with pitch variable;

[0036] [Fig.3] [Fig.3] is a schematic view of a variable-pitch stator or rectifier blade;

[0037] [Fig.4] [Fig.4] is a schematic view of a blade according to the invention;

[0038] [Fig.5] [Fig.5] is a perspective view of a thermocompression mold and shows a step of a method according to the invention;

[0039] [Fig.6] [Fig.6] is another schematic view of the mold and also illustrates the step of the method according to the invention;

[0040] [Fig.7a-7b] Figures 7a and 7b are very schematic partial sectional views of the thermocompression mold and also illustrate the aforementioned step;

[0041] [Fig.8] [Fig.8] is a schematic sectional view of a blade according to the invention; and

[0042] [Fig.9] [Fig.9] is a view similar to that of [Fig.6] and illustrates a variant of realization. Detailed description of the invention

[0043] Figures 1 to 3 have been described in the above.

[0044] The invention relates to an aircraft turbomachine blade, which may be the turbomachine of [Fig.l] or another turbomachine.

[0045] [Fig. 4] illustrates an embodiment of a blade 30 according to the invention for an aircraft turbomachine. The invention applies to any type of blade, stator or rotor. The blade 30 can therefore be a rotor propeller blade, like a stator blade. The blade can also be of the variable pitch type or not.

[0046] The blade 30 comprises a blade 32 having a lower surface 32a and an upper surface 32b, as well as a leading edge 32c and a trailing edge 32d.

[0047] One of the edges 32c, 32d of the blade 30 comprises serrations 35 formed by an alternation of teeth 35a and hollows 35b along this edge. This may be the leading edge 32c or the trailing edge 32d and the invention applies to these two cases although [Fig. 4] and the following figures focus on the presence and formation of serrations on the trailing edge 32d.

[0048] The invention relates to a method of manufacturing the blade 30.

[0049] The method comprises the following steps:

[0050] a) the production of a three-dimensional preform by weaving fibers, and

[0051] b) solidifying the preform with a polymerizable resin.

[0052] These steps are known, in particular in the context of a process of the RTM (Resin Transfer Molding) type.

[0053] In the context of the present invention, these steps are used to produce a blade body without the serrations 35.

[0054] The invention thus proposes to produce the serrations 35 after the solidification of the body of the blade. It is therefore understood that the formation of the serrations does not in itself impact the RTM type process.

[0055] The method according to the invention comprises, after steps a) and b), a step c) of forming the serrations 35.

[0056] As illustrated 5, 6 and 7a-7b, this formation is carried out by mounting the body 36 of the blade in a mold 38 comprising an imprint 40 of the serrations 35 to be formed, and by thermocompressing a material 42 in the mold 38.

[0057] This material 42 is intended to be secured to the body 36 of the blade and to adopt the shape of the imprint 40.

[0058] The assembly formed by the body 36 of the blade and the material 42 secured together forms the blade 32 of the vane 30.

[0059] In [Fig. 5], we see a mold 38 in two parts between which the body 36 of the blade is arranged. The two parts of the mold 38 define a cavity for housing the body of the blade. This cavity includes the aforementioned imprint 40.

[0060] In [Fig.6] and figure 7a, it can be seen that the material 42 is deposited on a part of the body 36 of the blade or is injected into the cavity of the mold 38, then in figure 7b, the mold 38 is closed and subjected to a thermocompression treatment so that the material 42 fills the imprint 40 and adopts its shape.

[0061] In Figures 4 and 8, it can be seen that the material 42 extends over the body 36 of the blade, only along the edge of the blade comprising the serrations 35. It is in fact not necessary to mold the material 42 over the entire body 36 of the blade.

[0062] The material 42 can be secured to the body 36 of the blade by chemical adhesion and / or mechanical anchoring. In the case of [Fig.8], it is a simple chemical adhesion which makes it possible to secure the material 42 to the body 36 of the blade.

[0063] In the case of [Fig.9], it is also a mechanical anchor which ensures this connection.

[0064] The mechanical anchoring can be achieved by filling housings 44 of the blade body 36 with the material 42 during step c). The method then preferably comprises, between steps b) and c), a step i) of forming the housings 44, for example by machining the blade body 36.

[0065] The housings 44 may each have a general dovetail shape as illustrated schematically in [Fig. 9]. They may extend over the entire transverse extent of the body 36 and therefore open respectively onto the intrados and the extrados of this body 36.

[0066] The method may comprise, after step c), a step d) of covering the blade 32 with a consolidation layer 46 which covers both the body 36 of the blade and the material 42 (see [Fig.8]). The consolidation layer is for example made of polyurethane.

[0067] With regard to the thermocompression in step c), the mold 38 is preferably heated to a temperature above 100°C, and for example between 120 and 150°C.

[0068] Thermocompression is preferably carried out at a pressure greater than 50 bars, and for example between 70 and 140 bars.

[0069] Thermocompression can be carried out for a period of between 15s and 40min depending on the nature of the material and the molding temperature.

[0070] The material 42 used for the formation of the serrations 36 preferably comprises at least one thermosetting polymer. This material 42 may comprise fillers, such as fibers, in particular carbon fibers.

[0071] It will be possible to use DLF (Discontinuons Long Fibre) type fillers and SMC (Sheet Molding Compound) or BMC (Bulk Molding Compound) type material. These fillers and materials have the advantage, in particular, of flowing in order to allow a complex shape such as the imprint 40 to be filled with serrations 35.

[0072] The material 42 used may be that marketed by the company Hexcel under the name HexMC®-i.

[0073] The present invention also relates to a blade 30 for an aircraft turbomachine, this blade 30 being obtained by the method described above.

[0074] The blade 30 comprises a blade 32 comprising a lower surface 32a and an upper surface 32b, as well as a leading edge 32c and a trailing edge 32d. The leading edge 32c or trailing edge 32d comprises serrations 35 formed by an alternation of teeth 35a and hollows 35b along this edge.

[0075] The blade 32 comprises a blade body 36 and the aforementioned material 42 secured to the blade body 36 and defining the serrations 35. The blade body 36 comprises a three-dimensional preform produced by weaving fibers and embedded in a resin which may be different from the material forming the serrations 35.

[0076] The resin and the material 42 can both be epoxy-based but can have different formulations and in particular different fillers or additives.

[0077] The method according to the invention may comprise, between steps b) and c), a step i) of preparing or treating the surface of the body 36 of the blade intended to be secured to the material 42. This preparation or this surface treatment is preferably chosen from sandblasting, plasma treatment and a film of glue. This makes it possible to activate the adhesion zone in order to have a better affinity between the resins.

[0078] The invention provides several advantages, including: • possibility of making complex shapes, • possibility of integrating the shape into existing blades, • possibility of repairing geometry throughout the part’s life cycle, • no influence on the integrity of the blade structure.

Claims

Claims

1. A method of manufacturing a blade (30) for an aircraft turbomachine, this blade (30) comprising a blade (32) comprising a lower surface (32a) and an upper surface (32b), as well as a leading edge (32c) and a trailing edge (32d), the leading edge (32c) or trailing edge (32d) comprising serrations (35) formed by alternating teeth (35a) and hollows (35b) along this edge, the method comprising: a) producing a three-dimensional preform by weaving fibers, and b) solidifying the preform with a polymerizable resin, characterized in that steps a) and b) make it possible to produce a body (36) of the blade without the serrations (35), and the method further comprises: c) forming the serrations (35), this formation being carried out by mounting the body (36) of the blade in a mold (38) comprising an imprint (40) of the serrations (35) to be formed, and by thermocompressing a material (42) in the mold (38),this material (42) being intended to be secured to the body (36) of the blade and to adopt the shape of the imprint (40), the assembly formed by the body (36) of the blade and the secured material (42) forming the blade (32) of the vane (30).,

2. Method according to claim 1, in which it comprises, between steps b) and c), a step i) of preparing or treating the surface of the body (36) of the blade intended to be secured to the material (42).

3. A method according to claim 1 or 2, wherein the material (42) extends over the body (36) of the blade, only along the edge of the blade (32) comprising the serrations (35).

4. Method according to one of the preceding claims, in which the material (42) is secured to the body (36) of the blade by chemical adhesion and / or mechanical anchoring.

5. Method according to claim 4, in which the mechanical anchoring is carried out by filling housings (44) of the blade body (36) with the material (42) during step c).

6. Method according to claim 5, in which it comprises, between steps b) and c), a step i) of forming the housings (44) for example by machining the blade body (36).

7. A method according to claim 5 or 6, wherein the housings (44) each have a general dovetail shape.

8. Method according to one of the preceding claims, in which it further comprises, after step c), a step d) of covering the blade with a consolidation layer (46) which covers both the body (36) of the blade and the material (42).

9. Method according to the preceding claim, in which the consolidation layer (46) is made of polyurethane.

10. Method according to one of the preceding claims, in which, during step c), the mold (38) is heated to a temperature above 100°C, and for example between 120 and 150°C.

11. Method according to one of the preceding claims, in which, during step c), the thermocompression is carried out at a pressure greater than 50 bars, and for example between 70 and 140 bars.

12. A method according to any preceding claim, wherein the material (42) comprises at least one thermosetting polymer.

13. A method according to any preceding claim, wherein the material (42) comprises fillers.

14. Method according to the preceding claim, in which the fillers comprise fibers, in particular carbon fibers.

15. Blade (30) for an aircraft turbomachine, this blade (30) being obtained by a method according to one of the preceding claims and comprising a blade (32) comprising a lower surface (32a) and an upper surface (32b), as well as a leading edge (32c) and a trailing edge (32d), the leading edge (32c) or trailing edge (32d) comprising serrations (35) formed by alternating teeth (35a) and hollows (35b) along this edge, the blade (32) comprising a blade body (36) and a material (42) secured to the blade body and defining said serrations (35), the blade body (36) comprising a three-dimensional preform produced by weaving fibers and embedded in a resin.

16. A blade (30) according to the preceding claim, wherein the resin and the material are both epoxy-based.

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