Method for manufacturing a blade or propeller with an elastomer media

Abstract

A method for manufacturing a blade or propeller with an elastomeric media comprises: - the creation of a fibrous blank (100) of an aerodynamically profiled structure by three-dimensional weaving of yarns, said blank comprising an internal cavity (104a), - the introduction of a portion (41) of an insert (40) into the internal cavity (104a) of the fibrous blank so as to form a preform, - the holding of the preform in a molding cavity of an injection mold having the shape of the blade or propeller to be manufactured, - the injection of a resin into the molding cavity containing the preform and the transformation of the resin into a matrix by heat treatment. The method further comprises, before the introduction of the portion (41) of the insert (40) into the internal cavity (104a) of the fibrous blank (100), the deposition of an elastomer layer (60) on at least said part of the insert and vulcanization of the elastomer.Figure for the abridged version: Fig. 6.

Description

Title of the invention: Method for manufacturing a blade or propeller with elastomeric media Technical field

[0001] The present invention relates to the field of blades or propellers for aircraft such as those present on turbomachines. Prior art

[0002] In order to obtain lighter blades or propellers, it is known to produce propellers from composite material, that is to say by producing structural parts with fibrous reinforcement densified by a matrix.

[0003] Document US 2005 / 0084377 describes a method for manufacturing a turbomachine blade from a monolithic composite material, the blade being manufactured by three-dimensional weaving of a fiber preform and densification of the preform by a matrix. This method makes it possible to obtain blades having very high mechanical strength, in particular with respect to shocks or impacts, without risk of delamination. However, the manufacture of large monolithic blades or propellers with this technique can prove difficult.

[0004] Manufacturing processes for manufacturing blades or propellers with the introduction of one or more inserts into a dry fiber preform have been developed.

[0005] Document US 2013 / 0017093 describes the production of a propeller from a fiber structure with an aerodynamic profile obtained by three-dimensional weaving and comprising an internal housing into which a part of a spar and several foam shaping elements are introduced. Before their introduction, the spar and the shaping elements are glued together in order to hold them and facilitate their positioning in the fiber structure.

[0006] The presence of initially raw glue in the mold creates significant constraints on the manufacturing process, particularly at the injection cycle level. The presence of glue also increases the risks of manufacturing non-conformities.

[0007] The insertion of the assembly of the spar and the shaping elements into the fiber structure is carried out using an interposition film which makes it possible to avoid adhesion between the assembly and the dry fiber structure, in particular at the level of the spar where a film of glue is previously deposited. This film must be removed before the injection molding operation of the preform. When the film is removed, it can tear and leave pieces in the final part ("foreign object damage"). Such contamination affects the material health of the final part which can be rejected in some cases.

[0008] Furthermore, the blades or propellers are subjected to high vibration levels which can lead to the appearance of vibrational instabilities (of the fluttering type) and / or to a reduction in fatigue life under forced stress (crosswind type, ground effect, etc.). Statement of the invention

[0009] It is therefore desirable to be able to propose a solution for the production of aircraft blades or propellers making it possible to minimize the risks of material contamination during manufacturing and to obtain blades or propellers in which the level of vibrations is reduced.

[0010] To this end, the present invention proposes a method of manufacturing a turbomachine blade or propeller, the method comprising:

[0011] - the production of a fiber blank of an aerodynamic profile structure by three-dimensional weaving of threads, said blank comprising an internal housing,

[0012] - the introduction of a part of an insert into the internal housing of the blank fibrous so as to form a preform,

[0013] - holding the preform in a molding cavity of an injection tool having the shape of the blade or propeller to be manufactured,

[0014] - injecting a resin into the molding cavity containing the preform and transforming it formation of the resin matrix by heat treatment,

[0015] characterized in that the method further comprises, before the introduction of the part of the insert into the internal housing of the fiber blank, the deposition of a layer of elastomer on at least said part of the insert and the vulcanization of the elastomer.

[0016] The deposition and the securing by vulcanization of a layer of elastomer on the external surface of the part of the insert intended to be introduced into the fiber blank makes it possible to protect the part of the insert during its introduction into the blank. There is no risk of material contamination because the layer of elastomer is an integral part of the final blade or propeller and therefore does not need to be removed after the introduction of the insert into the fiber blank.

[0017] The elastomer layer also makes it possible to avoid the use of an adhesive to fix the insert to the blank because the adhesion between the elastomer and the resin injected into the preform occurs naturally and directly during the transformation of the resin into the matrix.

[0018] Furthermore, the blade or propeller thus obtained is provided with a vibration damping function thanks to the presence of the elastomer layer.

[0019] According to a particular characteristic of the method of the invention, the insert comprises a spar made of metallic material comprising first and second parts and a foam body extending the second part of the spar, a layer of elastomer being deposited and vulcanized on the second part of the spar and the foam body before their introduction into the internal housing of the fiber blank. Thanks to the layer of elastomer which makes it possible to secure the foam body to the second part of the spar, it is not necessary to glue the foam body to the second part of the spar, which simplifies the manufacturing process.

[0020] According to another particular characteristic of the method of the invention, the first part of the spar forms a blade or propeller root.

[0021] According to another particular characteristic of the method of the invention, the resin injected into the molding cavity is an epoxy resin and the vulcanized elastomer layer comprises an unsaturated elastomer, the method further comprising, before inserting the insert into the internal housing of the fiber blank, preparing the external surface of the vulcanized unsaturated elastomer layer, the preparation comprising grafting a halogenated element onto said assembly surface by halogenation reaction. This makes it possible to increase the adhesive strength between the composite material of the aerodynamic profile of the blade or propeller and the elastomer and thus to reduce adhesive failures at the interface between the elastomer and the composite material.

[0022] According to another particular characteristic of the method of the invention, the latter comprises, before injecting the resin into the molding cavity, placing said molding cavity under vacuum. The presence of the elastomer layer facilitates placing the molding cavity under vacuum because it seals the foam body present in the preform.

[0023] The invention also provides a turbomachine blade or propeller comprising an aerodynamic profile structure consisting of at least one fiber reinforcement obtained by three-dimensional weaving of threads and densified by a matrix and an insert comprising a part present in a housing provided inside the fiber reinforcement, characterized in that a layer of vulcanized elastomer is present between the external surface of the first part of the insert and the internal surface of the housing of the fiber reinforcement. The presence of the elastomer layer between the external surface of the part of the insert and the internal surface of the housing of the fiber reinforcement makes it possible to provide the blade or propeller with a damping function, in particular by shearing of the elastomer layer when the blade is subjected to vibrations in bending and / or torsion.

[0024] According to a particular characteristic of the blade or propeller of the invention, the insert comprises a spar made of metallic material comprising first and second parts and a foam body extending the second part of the spar, the second part of the spar and the foam body being present in the housing of the fiber reinforcement, the first part of the spar extending outside the fiber reinforcement.

[0025] According to another particular characteristic of the blade or propeller of the invention, the first part of the spar forms a blade or propeller blade root. Brief description of the drawings

[0026] [Fig-1] [Fig.l] is a perspective view of a turbomachine blade in accordance with one embodiment of the invention,

[0027] [Fig.2] [Fig.2] is a schematic view illustrating the 3D weaving of a fiber blank for the manufacture of an aerodynamic profile structure of the propeller of [Fig.l],

[0028] [Fig.3A] [Fig.3A] is an enlarged partial sectional view of a set of layers of wires forming the blank of [Fig.l],

[0029] [Fig.3B] [Fig.3B] is another enlarged partial sectional view of a set of layers of wires forming the blank of [Fig.l],

[0030] [Fig.4] [Fig.4] is a schematic perspective view of an insert used for making a preform of the blade of [Fig.l],

[0031] [Fig.5] [Fig.5] is a schematic perspective view of the insert of [Fig.4] covered with a layer of elastomer,

[0032] [Fig.6] [Fig.6] is an exploded view showing the production of a preform of the blade of [Fig.l],

[0033] [Fig.7] [Fig.7] is an exploded perspective schematic view showing an injection tool and the placement of the preform of [Fig.6] therein,

[0034] [Fig.8] [Fig.8] is a schematic perspective view showing the injection tooling of [Fig.7] closed during a resin injection step. Description of Embodiments

[0035] The invention applies generally to different types of blades or propellers used in aircraft engines. The invention finds an advantageous but not exclusive application in large blades or propellers which are intended to be integrated into pivoting or variable pitch systems. Such blades or propellers are generally provided with a root having both a small footprint (compact shape) and good resistance to tensile, bending and circumferential compression forces. The blade according to the invention may in particular constitute a blade for shrouded moving wheels such as fan blades or a blade for unshrouded moving wheels as in so-called "open rotor" aeronautical engines.

[0036] In the remainder of the description, an example of implementation of the method of the invention is described in relation to the manufacture of a blade for a non-ducted moving wheel. However, the example of embodiment also applies to the manufacture other types of aircraft turbomachine blades or propellers.

[0037] [Fig. 1] represents a blade 10 intended to be mounted on an aircraft turboprop which comprises, in a manner well known per se, an aerodynamic profile structure 20 intended to form the aerodynamic part of the blade, a root 33 formed by a part of greater thickness, for example with a bulb-shaped section, extended by a stilt 34. The aerodynamic profile structure 20 has in cross section a curved profile of variable thickness between its leading edge 20 a and its trailing edge 20 b. The blade 10 comprises a spar 30 comprising a first part 31 extending outside the aerodynamic profile structure 20 and comprising the root 33 and Péchasse 34 and a second part 32 arranged inside the aerodynamic profile structure 20, the second part 32 being extended inside the aerodynamic profile structure 20 by a foam body 35.As explained below in detail, a layer of elastomer 60 is interposed between the assembly formed by the second part 32 of the spar 30 and the foam body 35 and the fiber reinforcement of the aerodynamic profile structure 20 of the blade 10.

[0038] [Fig.2] shows very schematically a fiber blank 100 intended to form the fiber preform of the aerodynamic profile structure of the blade.

[0039] The fibrous blank 100 is obtained, as illustrated schematically in [Fig. 2], by three-dimensional (3D) weaving carried out in a known manner using a jacquard-type loom on which a bundle of warp threads 101 or strands has been arranged in a plurality of layers of several hundred threads each, the warp threads being linked by weft threads 102.

[0040] In the example illustrated, the 3D weave is an "interlock" weave. By "interlock" we mean here a weave weave in which each layer of weft threads binds several layers of warp threads with all the threads of the same weft column having the same movement in the plane of the weave.

[0041] Other known types of three-dimensional weaving may be used, such as those described in document WO 2006 / 136755.

[0042] The fibrous blank may be woven from carbon fiber or ceramic yarns such as silicon carbide.

[0043] As the fiber blank, the thickness and width of which vary, is woven, a certain number of warp threads are not woven, which makes it possible to define the desired, continuously variable contour and thickness of the blank 100. An example of scalable 3D weaving, in particular making it possible to vary the thickness of the blank between a first edge intended to form the leading edge and a second edge of lesser thickness and intended to form the trailing edge, is described in document EP 1 526 285.

[0044] During weaving, a delinking 103 ([Fig.2]) is made inside the blank fibrous between two successive layers of warp threads and on a delinking zone 104 ([Fig.6]). The delinking zone 104 makes it possible to provide an internal housing 104a allowing the introduction of an insert, inside the fibrous blank 100 for the purpose of forming the preform of the aerodynamic profile structure.

[0045] A 3D interlock weaving mode of the blank 100 is shown schematically by Figures 3A and 3B. [Fig.3A] is an enlarged partial view of two successive warp sectional planes in a portion of the blank 100 not having a gap, that is to say in an area of ​​the blank located outside the gap 103, while [Fig.3B] shows two successive warp sectional planes in the portion of the blank 100 having the gap 103.

[0046] In this example, the blank 100 comprises 6 layers of warp threads 101 extending in the X direction. In [Fig.3A], the 6 layers of warp threads are linked by weft threads Ti to T5. In [Fig.3B], 3 layers of warp threads 101 forming the set of thread layers 105 are linked together by two weft threads Tb T2, just as the 3 layers of warp threads forming the set of thread layers 106 are linked by two weft threads T4 and T5. In other words, the fact that the weft threads Ti, T2 do not extend into the layers of threads 106 and that the weft threads T4, T5 do not extend into the layers of threads 105 ensures the delinking 103 which separates the sets of layers of warp threads 105, 106 from each other.

[0047] At the end of weaving ([Fig.2]), the warp and weft threads are cut, for example using a pressurized water jet, at the limit of the woven mass to extract the dry blank 100 shown in [Fig.6] as it results from the 3D weaving and before any shaping. The uncoupling zone 104 formed during weaving makes it possible to form two portions 110 and 111 woven independently of each other delimiting an internal housing 104a inside the blank 100. The two portions 110 and 111 are intended to form the skins 21 and 22 of the aerodynamic structure 20. The internal housing 104a is open on the lower edge 100c of the blank 100.The front edge 100a of the fiber blank 100, which connects the two portions 110 and 111 and which is intended to form the leading edge 20a of the aerodynamic profile structure 20 of the blade 10 while the rear edge 100b of the blank 100 corresponds to the part intended to form the trailing edge 20b of the aerodynamic profile structure ([Fig. 1]).

[0048] The manufacture of the blade comprises the use of an insert 40 corresponding here to the spar 30 and to the foam body 35 as illustrated in [Fig.4].

[0049] In accordance with the invention and as illustrated in [Fig. 5], a layer of elastomer 60 is deposited on the external surface of the second part 32 of the spar 30 and on the external surface of the foam body 35 held in position against and in the extension of the second part 32. The elastomer is then vulcanized around the foam body 35 and the second part 32 of the spar, which allows the two elements to be joined together. Bonding the foam body 35 to the second part 32 of the spar is not necessary because these two elements are held against each other by the vulcanized elastomer.

[0050] The metal surface of the second part 32 of the spar 30 is preferably chemically treated in order to promote its adhesion with the elastomer during its vulcanization. In a known manner, such a treatment may correspond to a surface activation by means of chemical products such as chemical conversion agents or specific acid solutions which create a reactive surface conducive to adhesion. The metal surface of the second part 32 of the spar 30 may also be treated by halogenation.

[0051] In the example described here, the spar 30 is made of metallic material, for example titanium, and the foam body 35 of ROHACELL® HERO -Evonik foam.

[0052] In [Fig.6], the conformation of the dry fibrous blank 100 is carried out in introducing into the internal housing 104a a part 41 of the insert 40 corresponding to the second part 32 of the spar 30 and to the foam body 35 covered with the vulcanized elastomer layer 60. The introduction of the part 41 of the insert into the fiber blank is facilitated by the presence of the elastomer layer 60 which secures the spar 30 and the foam body 60. In addition, no adhesive film is present on the external surface of the part 41 of the insert, which greatly simplifies the manufacturing process because it is no longer necessary to protect the insert during its introduction into the blank. The absence of the use of adhesive also simplifies the manufacturing process during the injection step.

[0053] A blade preform 200 is thus obtained comprising, in a longitudinal direction D1, an aerodynamic profile preform portion 211 constituted by the dry fiber blank 100 in the internal housing 104 of which the portion 41 of the insert 40 has been inserted ([Fig.7]). The vulcanized elastomer layer 60 is then interposed between the portion 41 and the dry fiber blank 100. The aerodynamic profile preform portion 211 extends in a transverse direction DT between a leading edge portion 211a and a trailing edge portion 211b.

[0054] As illustrated in [Fig.7], the blade preform 200 is placed in an injection tool 300 which comprises a first shell 310 comprising in its center a first imprint 311 corresponding in part to the shape and dimensions of the blade to be produced and a second shell 320 comprising in its center a second imprint 321 corresponding in part to the shape and dimensions of the blade to be produced.

[0055] Once the tool 300 is closed as illustrated in [Fig. 8], the first and second impressions 311 and 321 respectively of the first and second shells 310 and 320 together define a molding cavity 301 having the shape of the blade to be produced and in which the preform 200 is held.

[0056] The fibrous part of the preform, here the shaped fibrous blank, is then densified, as illustrated in [Fig.8]. The densification of the fibrous part of the preform consists of filling its porosity with the material constituting the matrix. This densification is carried out in a manner known per se using the liquid process (LCM). The liquid process consists of impregnating the preform with a liquid composition containing a precursor of the matrix material. The precursor is usually in the form of a polymer, such as a high-performance epoxy resin, possibly diluted in a solvent.

[0057] The transformation of the precursor into a matrix, namely its polymerization, is carried out by heat treatment, generally by heating the injection tooling, after elimination of any solvent and crosslinking of the polymer, the preform still being maintained in the molding cavity having a shape corresponding to that of the part to be produced. In the example described here, the injection tooling 300 further comprises a lower part 340 and an upper part 350 between which the first and second shells 310 and 320 are placed, the lower part 340 and the upper part 350 being equipped with heating means (not shown in [Fig.8]).

[0058] According to one aspect of the invention, the densification of the fiber preform can be carried out by the well-known transfer molding process known as RTM ("Resin Transfer Molding"). According to the RTM process, the fiber preform is placed in a mold having the external shape of the part to be produced. A thermosetting resin is injected into the internal space of the mold which includes the fiber preform. A pressure gradient is generally established in this internal space between the place where the resin is injected and the orifices for discharging the latter in order to control and optimize the impregnation of the preform by the resin.

[0059] As illustrated in [Fig. 8] and in accordance with the RTM method, a resin 380, for example a thermosetting resin, is injected via the injection port 313 of the first shell 310 into the molding cavity 301 occupied by the preform 200. Before the injection of the resin 380, the molding cavity 301 is placed under vacuum, for example via the port 323 of the second shell 320 which is connected to a vacuum draw conduit (not shown in [Fig. 8]). This configuration allows the establishment of a pressure gradient between the lower part of the preform 200 where the resin is injected and the upper part of the preform located near the port 323. In this way, the resin 360 injected substantially at the level of the lower part of the preform will progressively impregnate the entire fibrous part of the preform by circulating in it up to the evacuation port 323 through which the surplus is evacuated.Of course, the first and second shells 310 and 320 of the tooling 300 can. include respectively several injection ports and several evacuation ports.

[0060] The presence of the elastomer layer facilitates the vacuuming of the molding cavity because it seals the foam body present in the preform 200.

[0061] The resin used may be, for example, an epoxy resin with a temperature class of 180°C (maximum temperature supported without loss of characteristics). Resins suitable for RTM processes are well known. They preferably have a low viscosity to facilitate their injection into the fibers. The choice of temperature class and / or the chemical nature of the resin is determined according to the thermomechanical stresses to which the part must be subjected. Once the resin has been injected throughout the reinforcement, it is polymerized by heat treatment in accordance with the RTM process.

[0062] The injection of the resin into the fiber preform and its transformation into a matrix allows both the densification or consolidation of the aerodynamic profile preform part 211 of the blade preform constituted by the dry fiber blank 100 and the adhesion of the elastomer layer on the internal surface of the internal housing 104 of the dry fiber blank 100 in which the part 41 of the insert 40 has been inserted.

[0063] After injection and polymerization, the blade is demolded. Finally, the blade can be trimmed to remove excess resin and the chamfers are machined. No further machining is necessary since, the part being molded, it respects the required dimensions. The blade 10 of [Fig.l] is then obtained in composite material comprising a fiber reinforcement corresponding to the fiber blank 100 densified by the matrix.

[0064] The presence of the elastomer layer 60 between the external surface of the part 41 of the insert 40 (second part 32 of the spar 30 and foam body 35) and the internal surface of the housing 104 of the fiber reinforcement also makes it possible to provide the blade 10 with a damping function, in particular by shearing of the elastomer layer when the blade is subjected to vibrations in bending and / or in torsion.

[0065] According to a particular characteristic of the invention, the resin injected into the preform is an epoxy resin forming an organic matrix after polymerization. In this case, the vulcanized elastomer layer preferably comprises an unsaturated elastomer whose external surface has been prepared prior to its insertion into the internal housing of the fiber blank in order to improve its adhesion with the internal surface of the preform.

[0066] This step of preparing the external surface of the unsaturated elastomer is carried out by means of a halogenation reaction called addition halogenation. The halogenation reaction allows halogen atoms to react with the double bonds present in the structure of the elastomer. Halogenation is an addition reaction in which the halogen atoms are added to the double bonds of the unsaturated elastomer. The preparation of the assembly surface therefore comprises grafting a halogen element on the outer surface of the elastomer.

[0067] Due to the difference in electronegativity between halogen atoms and carbon atoms, the halogenation reaction on an unsaturated elastomer creates polarity. Therefore, saturating the unsaturated bonds of the elastomer with a halogen makes it possible to create very strong polar bonds with the resin injected into the preform during the polymerization phase. The halogen can be, in particular, chlorine (Cl2), fluorine (F2), bromine (Br2) or iodine (I2). The adhesion between the elastomer and the CMO of the part is thus significantly improved.

Claims

Claims

1. A method of manufacturing a turbomachine blade or propeller (10), the method comprising: - producing a fiber blank (100) of an aerodynamic profile structure by three-dimensional weaving of threads, said blank comprising an internal housing (104a), - introducing a portion (41) of an insert (40) into the internal housing (104a) of the fiber blank so as to form a preform (200), - holding the preform (200) in a molding cavity (301) of an injection tool (300) having the shape of the blade or propeller to be manufactured, - injecting a resin (380) into the molding cavity (301) containing the preform (200) and transforming the resin into a matrix by heat treatment, characterized in that the method further comprises, before the introduction of the part (41) of the insert (40) in the internal housing (104a) of the fiber blank (100),depositing a layer of elastomer (60) on at least said part of the insert and vulcanizing the elastomer.,

2. Method according to claim 1, in which the insert (40) comprises a spar (30) of metallic material having first and second parts (31, 32) and a foam body (35) extending the second part of the spar, a layer of elastomer (60) being deposited and vulcanized on the second part (32) of the spar (30) and the foam body (35) before their introduction into the internal housing (104a) of the fibrous blank (100).

3. Method according to claim 2, in which the first part (31) of the spar (30) forms a blade or propeller root (33).

4. A method according to any one of claims 1 to 3, wherein the resin (380) injected into the molding cavity (301) is an epoxy resin and wherein the vulcanized elastomer layer (60) comprises an unsaturated elastomer, the method further comprising, before inserting the insert into the internal housing of the fiber blank, preparing the external surface of the vulcanized unsaturated elastomer layer, the preparation comprising grafting a halogenated element onto said assembly surface by halogenation reaction.

5. A method according to any one of claims 1 to 4, comprising, before injecting the resin (380) into the molding cavity (301), placing said molding cavity under vacuum.

6. Turbomachine blade or propeller (10) comprising an aerodynamic profile structure (110) consisting of at least one fibrous reinforcement (200) obtained by three-dimensional weaving of threads and densified by a matrix and an insert (40) comprising a part (41) present in a housing provided inside the fibrous reinforcement, characterized in that a layer of vulcanized elastomer (60) is present between the external surface of the first part (41) of the insert (40) and the internal surface of the housing of the fibrous reinforcement.

7. A blade or propeller according to claim 6, wherein the insert (40) comprises a spar (30) of metallic material having first and second parts (31, 32) and a foam body (35) extending the second part (32) of the spar, the second part (32) of the spar and the foam body (35) being present in the housing of the fibrous reinforcement, the first part (31) of the spar extending outside the fibrous reinforcement.

8. A blade or propeller according to claim 7, wherein the first portion (31) of the spar (30) forms a blade or propeller root (33).

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