Method for manufacturing a hollow stator vane having internal stiffeners
Patent Information
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- SAFRAN AIRCRAFT ENGINES SAS
- Filing Date
- 2024-07-10
- Publication Date
- 2026-05-20
AI Technical Summary
Existing methods for manufacturing hollow stator blades with internal stiffeners face challenges in design and positioning of stiffeners, as well as the removal of shaping cores, which limits the mass reduction and mechanical strength of composite material blades used in aeronautical gas turbine engines.
A method involving three-dimensional weaving of fibrous blanks with intersecting stiffeners, insertion of soluble cores, and resin injection followed by heat treatment to create a hollow blade with internal stiffeners, allowing for the dissolution of cores and optimized mass reduction and impact absorption.
The method enables the production of lightweight, impact-resistant hollow blades with internal stiffeners that absorb energy during impacts, maintaining blade integrity while reducing overall mass.
Smart Images
Figure FR2024050946_16012025_PF_FP_ABST
Abstract
Description
[0001] Description
[0002] Title of the invention: Method for manufacturing a hollow stator blade with internal stiffeners
[0003] Technical Field
[0004] The present invention relates to the general field of blades for gas turbine aircraft engines and their manufacturing method.
[0005] Prior art
[0006] The invention relates more particularly to stator vanes or fixed vanes such as for example outlet guide vanes or "OGV" (for "outlet guide vane") or variable pitch stator vanes or "VSV" (for "variable stator vane").
[0007] In order to obtain lighter blades, it is known to produce blades from composite material, that is to say by producing structural parts with fibrous reinforcement densified by a matrix.
[0008] 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. While this method makes it possible to obtain blades with high mechanical strength, the overall mass of the blade remains high, particularly for large blades.
[0009] In order to reduce the overall mass of composite blades, methods for manufacturing hollow blades have been developed. In some of these methods, one or more foam pieces are used to shape the woven fiber blank. For example, US 20220097824 discloses a method for producing a composite blade using a shaping foam to shape a fiber structure obtained by three-dimensional weaving.
[0010] However, foam has a significant cost and requires special precautions due to its sensitivity to humidity. Also, in order to maintain good mechanical strength at the level of the internal volume of the blade, one solution consists of providing the blade with internal stiffeners. Document WO2022263743 discloses a method for manufacturing a fiber blade preform whose internal volume is provided with internal stiffeners.
[0011] However, shaping a fiber preform equipped with internal stiffeners can be tricky, especially when one wishes to obtain a blade with an empty internal volume. Indeed, in this case, the shaping parts or cores used for shaping the blade preform must be removed at the end of manufacturing. The internal volume must therefore have a geometry that allows the shaping part(s) to be removed, which greatly limits the possibilities of integrating internal stiffeners into the blade. In document WO2022263743, the internal stiffeners extend in a radial direction of the blade along the internal surface of the blade skins, which allows the disassembly of the shaping part(s) used.
[0012] Statement of the invention
[0013] It is therefore desirable to be able to offer a solution for the production of stator blades in composite material which offers greater freedom in the design and positioning of the stiffeners in the internal volume of the blade.
[0014] To this end, the present invention provides a method for manufacturing a turbomachine stator blade, the method comprising:
[0015] - the production of a fiber blank of an aerodynamic profile structure by three-dimensional weaving of threads, said blank comprising a first and a second skin, an internal housing present between the skins, one or more first fiber stiffeners extending in a first direction in the internal housing and one or more second fiber stiffeners extending in a second direction in the internal housing, the first and second directions being intersecting, the first fiber stiffener(s) and the second fiber stiffener(s) delimiting between them cavities in the internal housing,
[0016] - the insertion of soluble cores into the cavities of the internal housing so as to obtain a fibrous preform, - the holding of the fibrous preform in a molding cavity of an injection tool having the shape of the stator blade to be manufactured,
[0017] - injecting a resin into the molding cavity containing the fiber preform and transforming the resin into a matrix by heat treatment so as to obtain an intermediate stator blade part made of composite material comprising an internal volume present between two skins, said internal volume comprising one or more first stiffeners extending in the first direction and one or more second stiffeners extending in the second direction, each in contact with the internal face of the skins, at least some stiffeners comprising one or more circulation channels,
[0018] - the dissolution of the nuclei present in the cavities.
[0019] With the method of the invention, it is possible to form a hollow blade comprising internal stiffeners extending in different directions, and with a hollowed-out internal volume between the stiffeners. Indeed, certain cavities are not accessible at the end of manufacturing, which prevents manual disassembly or dissolution of the cores present in these cavities. By using soluble cores and creating circulation channels in the stiffeners, it is possible to dissolve all the cores used for shaping the blade.
[0020] The blade thus obtained comprises one or more internal stiffeners which, in addition to increasing the rigidity of the blade skins at the level of the internal volume thereof, advantageously form portions capable of breaking in the event of impact of the aerodynamic structure of the blade with ingested objects or fragments of damaged blades. In this case, the stiffener(s) absorb a significant portion of the impact energy, thus allowing the blade to retain its integrity. The overall mass of the blade is further optimized because apart from the stiffeners, the internal volume of the blade is empty.
[0021] According to a particular characteristic of the method of the invention, the first fibrous stiffener(s) extend in a radial direction in the internal housing and the second fibrous stiffener(s) extend in an axial direction in the internal housing.
[0022] According to another particular characteristic of the method of the invention, at least a portion of the first fibrous stiffeners and the second fibrous stiffeners is formed by three-dimensional weaving on an internal face of the first or second skin.
[0023] According to another particular characteristic of the method of the invention, at least a portion of the first fibrous stiffeners and the second fibrous stiffeners comprises one or more unidirectional layers of yarns held on an internal face of the first or second skin.
[0024] According to another particular characteristic of the method of the invention, the soluble cores are connected together by soluble connecting rods positioned on at least certain fibrous stiffeners of the fibrous blank during the insertion of the soluble cores into the cavities of the internal housing, said connecting rods forming circulation channels in at least certain stiffeners of the stator blade.
[0025] According to another particular characteristic of the process of the invention, the soluble nuclei may be salt nuclei, for example zirconium salt, or sand nuclei or salt nuclei mixed with sand.
[0026] The invention also relates to a stator blade made of composite material comprising a fibrous reinforcement densified by a matrix, the stator blade comprising an aerodynamic profile structure, said aerodynamic profile structure comprising first and second skins and an internal volume present between the skins, the stator blade further comprising one or more first stiffeners extending in a first direction in the internal volume and one or more second stiffeners extending in a second direction in the internal volume, the first and second directions being intersecting, the first stiffener(s) and the second stiffener(s) being integral with the internal faces of the first and second skins, at least some stiffeners comprising one or more channels.
[0027] The blade according to the invention comprises in particular one or more stiffeners which, in addition to increasing the rigidity of the skins of the blade at the level of the internal volume thereof, advantageously form portions capable of breaking in the event of impact of the aerodynamic structure of the blade with ingested objects or fragments of damaged blades. In this case, the stiffener(s) absorb a significant portion of the impact energy, thus allowing the blade to retain its integrity. The overall mass of the blade is further optimized because apart from the stiffeners, the internal volume of the blade is empty. According to a particular characteristic of the stator blade of the invention, the first stiffener(s) extend in a radial direction in the internal volume and the second stiffener(s) extend in an axial direction in the internal volume.
[0028] According to another particular characteristic of the stator blade of the invention, at least a portion of the first stiffeners and the second stiffeners has a three-dimensional weave linked to an internal face of the first or second skin.
[0029] According to another particular characteristic of the stator blade of the invention, at least a portion of the first stiffeners and the second stiffeners comprises one or more unidirectional layers of wires held on an internal face of the first or second skin.
[0030] Brief description of the drawings
[0031] [Fig. 1] Figure 1 is a perspective view of a stator blade in accordance with one embodiment of the invention,
[0032] [Fig. 2] Figure 2 is a schematic view illustrating the 3D weaving of a fiber blank for the manufacture of an aerodynamic profile structure of the blade of Figure 1,
[0033] [Fig. 3A] Figure 3A is an enlarged partial sectional view of a set of layers of wires forming the blank of Figure 1,
[0034] [Fig. 3B] Figure 3B is another enlarged partial sectional view of a set of layers of wires forming the blank of Figure 1,
[0035] [Fig. 4] Figure 4 is an exploded view showing the production of a preform of the blade of Figure 1,
[0036] [Fig. 5] Figure 5 is a perspective view showing the resulting blade preform,
[0037] [Fig. 6] Figure 6 is a sectional view of the preform of Figure 5,
[0038] [Fig. 7] Figure 7 is an exploded perspective schematic view showing an injection tool and the placement of the preform of Figure 6 therein, [Fig. 8] Figure 8 is a perspective schematic view showing the injection tool of Figure 7 closed during a resin injection step,
[0039] [Fig. 9] Figure 9 is a perspective view of the intermediate part obtained after injection and polymerization of resin in the preform of Figure 5,
[0040] [Fig. 10] Figure 10 is a sectional view of the intermediate piece of Figure 9.
[0041] Description of the embodiments
[0042] The invention applies generally to different types of stator blades or static blades used in aircraft engines. Non-limiting examples of such blades include outlet guide vanes (OGVs). The invention finds a particular but not exclusive application in large stator blades for which reducing the overall mass of the blade is particularly desirable.
[0043] 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 flow straightener blade or OGV for an unducted fan such as in so-called "open rotor" aeronautical engines.
[0044] Figure 1 shows a stator blade 10 made of composite material intended to be mounted on an unducted fan of an aircraft turboprop engine which comprises, in a manner well known per se, an aerodynamic profile structure 20 intended to form the aerodynamic part of the blade. The stator blade generally comprises a foot for its attachment to the fan and which is not shown in Figure 1 for the sake of simplification. The aerodynamic profile structure 20 has in cross section a curved profile of variable thickness between its leading edge 20a and its trailing edge 20b.
[0045] The aerodynamic structure 20 comprises an intrados skin 21 and an extrados skin 22 as well as an internal volume 30 present between the skins 21 and 22.
[0046] In the example described here and in accordance with the invention, a first stiffener, here a vertical stiffener 40, extending in a first direction, here a radial direction DR and two second stiffeners, here two horizontal stiffeners 50 and 60, extending in a second direction, here an axial direction D A are present in the internal volume 30. The vertical stiffener 40 extends between an inlet 30c and a bottom 30d of the internal volume 30. The horizontal stiffeners 50 and 60 extend between an upstream edge 30a and a downstream edge 30b of the internal volume 30. The first stiffener, here the stiffener 40, can extend between the inlet 30c and the bottom 30d of the internal volume 30 in a first direction different from the radial direction DR while the second stiffeners, here the two stiffeners 50 and 60, can extend between the upstream edge 30a and the downstream edge 30b of the internal volume 30 in a second direction different from the axial direction DA , the first and second directions being intersecting. The vertical stiffener 40 and horizontal stiffeners 50 and 60 are in contact and secured to the inner face 21a of the intrados skin 21 and the inner face 22a of the extrados skin of the blade. In the example described here, the aerodynamic structure 20 and the stiffeners 40, 50 and 60 comprise a fibrous reinforcement having a three-dimensional weave densified by a matrix as explained below in more detail. The internal volume 30 is empty in all its parts present outside the stiffeners.
[0047] In the example described here, the blade 10 is provided with a single first stiffener, here the vertical stiffener, in its internal volume. However, the stator blade according to the invention may comprise a greater number of first stiffeners. The number of first stiffeners is notably determined according to the need for stiffening the skins at the level of the internal volume of the blade with respect to the vibratory stresses exerted on the blade in operation and / or the ingestion of objects.
[0048] Similarly, the blade 10 described here is provided with two second stiffeners, here two horizontal stiffeners. However, the stator blade according to the invention may comprise only one second stiffener or more than two second stiffeners. In addition to reinforcing the mechanical strength (rigidity) of the blade at the level of its internal volume, the second stiffener(s) advantageously form portions capable of breaking in the event of impact of the aerodynamic structure of the blade with ingested objects or fragments of damaged blades. In this case, the second stiffener(s) absorb a significant portion of the impact energy, thus allowing the blade to retain its integrity.
[0049] Still in the example described here, the first stiffener, here the vertical stiffener 40, comprises channels or grooves 41, 42 and 43 facing the internal face 21a of the intrados skin 21. Similarly, the second stiffeners, here the horizontal stiffeners 50 and 60, respectively comprise channels or grooves 51, 52 and 61, 62 facing the internal face 21a of the intrados skin. These channels have been formed to facilitate the dissolution of shaping cores used during manufacturing as will be described below. These channels can also advantageously form zones of weakness promoting the rupture of the stiffener(s) in the event of impact with an object.
[0050] Figure 2 shows very schematically a fiber blank 100 intended to form the fiber preform of the aerodynamic profile structure of the blade.
[0051] The fibrous blank 100 is obtained, as schematically illustrated in Figure 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.
[0052] In the example shown, the 3D weave is an interlock weave. An interlock weave here means a weave pattern in which each layer of weft yarns binds together multiple layers of warp yarns, with all yarns in a single weft column moving in the plane of the weave.
[0053] Other known types of three-dimensional weaving may be used, such as those described in document WO 2006 / 136755.
[0054] The fiber blank can be woven from carbon fiber or ceramic yarns such as silicon carbide.
[0055] 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, the content of which is incorporated here by reference.
[0056] During weaving, a delinking 103 (figure 2) is produced inside the fiber blank between two successive layers of warp threads and on a delinking zone 104 (figure 4). The delinking zone 104 makes it possible to provide an internal housing 104a inside the fiber blank 100 for the purpose of forming the preform of the aerodynamic profile structure.
[0057] A 3D interlock weaving mode of the blank 100 is shown schematically by Figures 3A and 3B. Figure 3A is an enlarged partial view of two successive warp sectional planes in a portion of the blank 100 not having a delink, that is to say in an area of the blank located outside the delink 103, while Figure 3B shows two successive warp sectional planes in the portion of the blank 100 having the delink 103 forming the delink zone 104.
[0058] In this example, the blank 100 comprises 6 layers of warp yarns 101 extending in the X direction. In Figure 3A, the 6 layers of warp yarns are linked by weft yarns to T5. In Figure 3B, 3 layers of warp threads 101 forming a portion or skin 110 are linked together by two weft threads Ti, T2, just as the 3 layers of warp threads forming a portion or skin 111 are linked by two weft threads T4 and T5. In other words, the fact that the weft threads Tn T2 do not extend into the portion 111 and that the weft threads T4, T5 do not extend into the portion 110 ensures the delinking 103 which separates the portions 110 and 111 from each other.
[0059] At the end of weaving (Figure 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 Figure 4 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 parts of the intrados 21 and extrados 22 skins of the aerodynamic structure 20 at the level of the hollow internal volume 30. The internal housing 104a is open on the lower edge 100c.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 (figure 1). As illustrated in figure 4, the fiber blank 100 comprises inside the internal housing 104a a first fiber stiffener, here a vertical fiber stiffener 140, extending in a first direction, here the radial direction D. R corresponding to the direction of extension of the warp threads 101 in the blank 100 and two second stiffeners, here two horizontal fibrous stiffeners 150 and 160, extending in a second direction, here the axial direction D Acorresponding to the direction of extension of the weft threads 102 in the blank 100. The first fibrous stiffener, here the fibrous stiffener 140, can extend in a first direction different from the radial direction DR while the second fibrous stiffeners, here the two fibrous stiffeners 150 and 160, can extend in a second direction different from the axial direction D A , the first and second directions being intersecting.
[0060] The fibrous stiffeners 140, 150 and 160 are here produced by three-dimensional weaving at the same time as the three-dimensional weaving of the fibrous blank 100. The fibrous stiffeners 140, 150 and 160 are woven integrally with the internal face of the portion 111 of the blank 100 but are not linked by weaving to the internal face of the portion 110 of the blank 100. This makes it possible to provide a passage between the portion 110, on the one hand, and the portion 111 and the fibrous stiffeners 140, 150 and 160, on the other hand for the insertion of shaping cores as explained below. The fibrous stiffeners 140, 150 and 160 delimit between them and in the internal housing 104a cavities 112, 113, 114, 115, 116 and 117 as illustrated in FIG. 4.
[0061] As previously stated, the number of first fiber stiffeners or second fiber stiffeners is variable between one or more stiffeners depending on the blade's rigidity and impact resistance requirements.
[0062] According to an alternative embodiment, all or part of the first fiber stiffener(s) and the second fiber stiffener(s) may be formed from one or more unidirectional layers of yarns held against the inner face of one of the portions 110 and 110 of the blank. The formation of stiffeners from unidirectional layers of yarns is described in document WO2022263743.
[0063] In accordance with the invention and as shown in FIG. 4, the shaping of the fibrous blank 100 is carried out by introducing soluble cores into the internal housing 104a. More specifically, soluble cores 171, 172, 173, 174, 175 and 176 are respectively introduced and arranged in the cavities 112, 113, 114, 115, 116 and 117 present in the internal housing 104a of the fiber blank 100. In the example described here, the soluble cores 171, 172, 173, 174, 175 and 176 are connected to each other by horizontal 177 and vertical 178 connecting rods. This makes it possible to form a network 170 with the cores 171, 172, 173, 174, 175 and 176, thus facilitating the insertion of all the cores into the internal housing.
[0064] Once the network 170 of cores 171, 172, 173, 174, 175 and 176 has been introduced and positioned in the internal housing 104a of the fiber blank 100, a fiber blade preform 200 is obtained, illustrated in FIG. 5 and which comprises an aerodynamic profile preform portion 211 constituted by the dry fiber blank 100 in the internal housing 104a of which the cores 171, 172, 173, 174, 175 and 176 are positioned in the cavities delimited by the fiber stiffeners 140, 150 and 160.
[0065] The horizontal connecting rods 177 overlap the vertical fiber stiffener 140 while the vertical connecting rods 178 overlap the horizontal fiber stiffeners 150 and 160. The connecting rods here also have a function of forming circulation channels in the stiffeners in order to facilitate the elimination of soluble cores at the end of manufacturing as explained later. Indeed, as shown in Figure 6 for the horizontal fiber stiffener 160, the connecting rods 178 each form a channel or groove in the stiffener 160 which may be more pronounced after compacting the preform.
[0066] According to an implementation variant, the soluble cores 171, 172, 173, 174, 175 and 176 can be used independently (no network 170) to be positioned one by one in the corresponding cavities. In this case, independent elements made of the same material as the cores or of a different material can be placed on the fibrous stiffeners in which it is desired to form circulation channels. According to a variant, the stiffeners comprise different compaction zones making it possible to form circulation channels.
[0067] The aerodynamic profile preform portion 211 extends in a transverse direction D Tbetween a leading edge portion 211 a and a trailing edge portion 211 b. The fiber preform is then densified. The densification of the fiber preform intended to form the fiber reinforcement of the part to be manufactured consists of filling the porosity of the preform, in all or part of its volume, with the material constituting the matrix. This densification is carried out in a manner known per se using the liquid process (LC). 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. The preform is placed in a mold that can be closed tightly with a housing having the shape of the final molded blade.Then, the mold is closed and the liquid matrix precursor (for example a resin) is injected into the entire housing to impregnate the entire fibrous part of the preform.
[0068] The transformation of the precursor into a matrix, namely its polymerization, is carried out by heat treatment, generally by heating the mold, after elimination of any solvent and crosslinking of the polymer, the preform always being maintained in the mold having a shape corresponding to that of the part to be produced.
[0069] In the case of carbon or ceramic matrix formation, the heat treatment consists of pyrolyzing the precursor to transform the matrix into a carbon or ceramic matrix depending on the precursor used and the pyrolysis conditions. For example, liquid ceramic precursors, particularly SiC, can be polycarbosilane (PCS) or polytitanocarbosilane (PTCS) or polysilazane (PSZ) resins, while liquid carbon precursors can be resins with a relatively high coke content, such as phenolic resins. Several consecutive cycles, from impregnation to heat treatment, can be carried out to achieve the desired degree of densification.
[0070] According to one aspect of the invention, in the case in particular of the formation of an organic matrix, the densification of the fibrous preform can be carried out by the well-known transfer molding process known as RTM ("Resin Transfer Molding").
[0071] In the RTM process, the fiber preform is placed in a mold that has the external shape of the part to be produced. A thermosetting resin is injected into the internal space of the mold, which contains the fiber preform. A pressure gradient is generally established in this internal space between the point where the resin is injected and the resin discharge ports in order to control and optimize the impregnation of the preform by the resin.
[0072] As illustrated in Figure 7, the injection of a liquid matrix precursor composition into the fibrous texture and its transformation into a matrix are here carried out 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.
[0073] 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 an internal volume 301 having the shape of the blade to be produced and in which the fiber preform 200 is placed. A compaction of the fiber preform 200 can be carried out with the closing of the tool 300 in order to obtain a determined fiber rate in the preform. In this case, a compaction pressure is applied to the shells 310 and 320 for example by means of a press. The compaction of the fiber preform can also be carried out in a separate tool before the introduction of the preform into the injection tool.
[0074] The tool 300 further comprises means for carrying out the injection of a liquid matrix precursor and the transformation of this precursor into a matrix. More specifically, in the example described here, the first shell 310 of the tool 300 comprises an injection port 313 intended to allow the injection of a liquid matrix precursor composition into the fiber preform while the second shell comprises an evacuation port 323 intended to cooperate with a pumping system for placing the tool under vacuum and drawing air during injection. The injection tool 300 also 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).Once the tool 300 is closed, the blade is molded by impregnating the preform 200 with a thermosetting resin that is polymerized by heat treatment. For this purpose, the well-known injection or transfer molding process known as RTM ("Resin Transfer Molding") is used. In accordance with the RTM process, a resin 380, for example a thermosetting resin, is injected via the injection port 313 of the first shell 310 into the internal volume occupied by the preform 200. The port 323 of the second shell 320 is connected to a discharge conduit maintained under pressure (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 380 injected substantially at the level of the lower part of the preform will gradually impregnate the entire 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 may respectively comprise several injection ports and several evacuation ports. The RTM process can also be carried out under vacuum (VA-RTM).
[0075] The resin used can be, for example, an epoxy resin with a temperature class of 180 °C. 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.
[0076] The densification processes described above make it possible to produce, from the fiber preform of the invention, mainly stator blades made of organic matrix composite (OMC), carbon matrix (C / C) and ceramic matrix (CMC) materials.
[0077] After injection, polymerization and demolding, an intermediate part made of composite material 400 is obtained, as illustrated in FIG. 9, having a fiber reinforcement constituted by the fiber preform 200 and densified by the matrix. The intermediate part 400 comprises an aerodynamic profile portion 411 intended to form the aerodynamic structure 20 of the stator blade 10 to be produced. The aerodynamic profile portion 411 comprises two skins 421 and 422 intended to form respectively the intrados skin 21 and the extrados skin 22 of the blade 10.
[0078] The aerodynamic profile portion 411 comprises an internal volume 430 present between the skins 421 and 422 and intended to form the internal volume 30 of the blade 10. The internal volume 430 comprises a vertical stiffener 440 and two horizontal stiffeners 450 and 460, all three made of composite material and intended to form respectively the vertical stiffener 40 and the horizontal stiffeners 50 and 60 of the stator blade 10. The stiffeners 440, 450 and 460 are linked to the skin 422 by weaving as explained previously (fibrous stiffeners 140, 150 and 160 woven integrally with the portion 111 of the blank 100). At this stage of manufacturing, the stiffeners 440, 450 and 460 are also bonded to the skin 421 by the co-densification carried out between the stiffeners 440, 450 and 460 and the skin 421 during the injection and polymerization of the resin in the fiber preform 200.The airfoil portion 411 includes the dissolvable cores 171, 172, 173, 174, 175, and 176 in the cavities defined between the stiffeners 440, 450, and 460 and the connecting rods 177 and 178 at the stiffeners. As illustrated in FIG. 10, for the horizontal stiffener 460, the connecting rods 178 each form a channel or groove in the stiffener 460 that is more pronounced than in FIG. 6 as a result of compaction of the preform.
[0079] The cores 171, 172, 173, 174, 175 and 176 and the connecting rods 177 and 178 are made of a soluble material so that they can be removed from the intermediate part 400. Indeed, the presence here of two horizontal stiffeners prevents the cores 172, 173, 175 and 176 from being removed from the part 400. The cores and the connecting rods are made of a soluble material or mixture. They can be made in particular from a salt, such as zirconium salt or sand. The cores can also be made from a mixture of salt and sand.
[0080] The cores 171, 172, 173, 174, 175 and 176 present in the intermediate part 400 are then eliminated by dissolution. For this purpose and as in the example described here, a first bore 180 is first made in the core 171 and a second bore 181 in the core 174. A dissolution fluid F1 is then introduced here into the first bore 180 in order to gradually dissolve the cores and the connecting rods, which makes it possible to form a circulation circuit for the dissolution fluid in all the cavities where the cores are present. A fluid F2 comprising the dissolution fluid F1 loaded with the dissolved material of the cores is evacuated. Drilling 180 or 181 is used as a primer for the dissolution first of cores 171 and 174, the dissolution then continuing with that of cores 172, 173, 175 and 176 which cannot be removed from the mold.The dissolving fluid may be, in particular, water, a heated basic solution or any other fluid capable of dissolving the material of the cores. Once the cores have been completely dissolved and removed from the internal volume of the intermediate part 400, the latter may optionally be trimmed to remove excess resin and the chamfers are machined. No further machining is necessary since, since the part is molded, it meets the required dimensions. The stator blade 10 of FIG. 1 is then obtained.
Claims
Claims
1. A method of manufacturing a stator blade (10) of a turbomachine, the method comprising: - producing a fibrous blank (100) of an aerodynamically profiled structure by three-dimensional weaving of threads, said blank comprising a first and a second skin (110, 111), an internal housing (104a) present between the skins, one or more first fibrous stiffeners (140) extending in a first direction in the internal housing and one or more second fibrous stiffeners (150, 160) extending in a second direction in the internal housing, the first and second directions being intersecting, the first fibrous stiffener(s) and the second fibrous stiffener(s) delimiting between them cavities (112, 113, 114, 115, 116, 117) in the internal housing (104a), - inserting soluble cores (171, 172, 173, 174, 175, 176) into the cavities of the internal housing so as to obtain a fibrous preform (200), - holding the fiber preform (200) in a molding cavity (301) of an injection tool (300) having the shape of the stator blade to be manufactured, - injecting a resin (380) into the molding cavity (301) containing the fiber preform (200) and transforming the resin into a matrix by heat treatment so as to obtain an intermediate stator blade part (400) made of composite material comprising an internal volume (430) present between two skins (421, 422), said internal volume comprising one or more first stiffeners (440) extending in the first direction and one or more second stiffeners (450, 460) extending in the second direction, each in contact with the internal face of the skins, at least some stiffeners comprising one or more circulation channels, - the dissolution of the nuclei present in the cavities.
2. A method according to claim 1, wherein the first fibrous stiffener(s) (140) extend in a radial direction (DR) in the internal housing and wherein the second stiffener(s) fibrous (150, 160) extend in an axial direction (D) in the internal housing.
3. A method according to claim 1 or 2, wherein at least a portion of the first fibrous stiffeners (140) and the second fibrous stiffeners (150, 160) are formed by three-dimensional weaving on an inner face of the first or second skin (110, 111).
4. A method according to any one of claims 1 to 5. 3, wherein at least a portion of the first fibrous stiffeners (140) and the second stiffeners (150, 160) comprises one or more unidirectional layers of yarns held on an inner face of the first or second skin (110, 111).
5. A method according to any one of claims 1 to 5. 4, wherein the soluble cores (171, 172, 173, 174, 175, 176) are connected together by soluble connecting rods (177, 178) positioned on at least some fibrous stiffeners of the fibrous blank upon insertion of the soluble cores into the cavities of the internal housing, said connecting rods forming circulation channels in at least some stiffeners of the stator blade.
6. A method according to any one of claims 1 to 5. 5, wherein the soluble nuclei (171, 172, 173, 174, 175, 176) are zirconium salt nuclei or sand nuclei, or nuclei of a mixture of zirconium salt and sand.
7. Stator blade (10) made of composite material comprising a fibrous reinforcement densified by a matrix, the stator blade comprising an aerodynamic profile structure (20), said aerodynamic profile structure comprising first and second skins (21, 22) and an internal volume (30) present between the skins, the stator blade further comprising one or more first stiffeners (40) extending in a first direction in the internal volume (30) and one or more second stiffeners (50, 60) extending in a second direction in the internal volume, the first and second directions being intersecting, the first stiffener(s) and the second stiffener(s) being integral with the internal faces (21a, 22a) first and second skins (21, 22), at least some stiffeners comprising one or more channels (41, 42, 43, 51, 52, 61, 62).
8. Blade according to claim 7, in which the first stiffener(s) (40) extend in a radial direction (DR) in the internal volume (30) and in which the second stiffener(s) (50, 60) extend in an axial direction (D A ) in the internal volume.
9. Blade according to claim 7 or 8, in which at least a portion of the first stiffeners (40) and the second (50, 60) has a three-dimensional weave bonded to an internal face (21a, 22a) of the first or second skin (21, 22).
10. A blade according to any one of claims 7 to 9, wherein at least a portion of the first stiffeners (40) and second stiffeners (50, 60) comprises one or more unidirectional layers of wires held on an inner face (21a, 22a) of the first or second skin (21, 22).