Composite turbine blade and method of manufacturing the same

Abstract

A turbine blade (10) is disclosed, the blade being made of a composite material formed from woven fibers embedded in a polymer resin, the blade comprising a root portion (16) connected to a blade (12) comprising a pressure side (18) and a suction side (20) via a support portion (14), at least one textile wear strip (22) being located on the surface of the root portion and / or the support portion, characterised in that the at least one wear strip is fixed to the surface of the root portion in an integral manner by the resin.

Description

Technical Field

[0001] The invention relates to a composite material turbine blade and a manufacturing method thereof. Background Art

[0002] The technical background includes in particular documents US-A1-2015 / 110 636, US-A1-5 935 360, WO-A1-2015 / 057 369 A1 and FR-A1-3 049 305.

[0003] The use of composite materials is particularly advantageous in the aerospace industry because these materials are relatively light and have good mechanical properties.

[0004] Composite materials commonly used in aviation consist of a preform of fibers embedded in a polymer resin. The preform can be a three-dimensional woven fabric or can be obtained by draping and stacking multiple fabrics.

[0005] The resin may be injected into the preform, or the preform may be pre-impregnated with the resin.

[0006] The final part is typically formed using a tool that includes a mold. In the case of resin injection into a preform, the preform is placed in the mold cavity, and the mold is covered with a counter-mold. The tool includes ports for injecting resin into the mold cavity and ports for evacuating the mold cavity.

[0007] Having impregnated the preform with resin, the preform is arranged in the cavity of a mould, which may be covered with a flexible tarpaulin or a counter-mould.

[0008] The tool also includes ports for injecting resin into the mold cavity and for applying a vacuum to the mold cavity. As the vacuum is applied to the preform between the counter mold and the flexible tarp or mold, the counter mold applies pressure to the preform. The use of a counter mold allows for greater control over the thickness of the final part.

[0009] In the case of blades, in particular blades for fans, the above-mentioned molding operation must be followed by an operation of applying a wear strip to the root and the support of the blade.

[0010] Currently, these strips are assembled and fixed to the blade's root and support by gluing. Therefore, the wear strip is first impregnated manually with glue (usually phenolic resin). Then, an operator manually places the wear strip on the blade's root and support.

[0011] The hardbanded bucket is then placed back into the mold and the hardband is vacuum glued using a silicone counter mold.

[0012] Therefore, this operation of gluing the hardband requires a lot of manual work and produces many defects in the final component. In use, it has been found that the hardband falls off, thereby exposing the composite material of the blade and making the blade unusable.

[0013] These falls are mainly due to poor gluing of the wear strips. However, the correct gluing ratio requires weighing the glue to the nearest tenth of a gram, which is almost impossible to achieve when doing it manually.

[0014] Furthermore, the way the glue is distributed on the wear strip has a direct influence on the quality of the gluing: even the smallest areas of poor impregnation will result in a poor gluing.

[0015] The amount of glue can also lead to dimensional non-compliance: The amount of glue directly affects the final thickness of the wear strip on the blade.

[0016] Therefore, if the strip is over-impregnated or the glue is unevenly distributed, variations in flatness and dimensions, particularly at the root of the blade, may be out of tolerance, rendering the blade non-compliant.

[0017] A dry hardstrip is provided, wherein variations in the thickness of the hardstrip do not allow standardisation of the amount of glue: a thinner hardstrip requires a smaller amount of adhesive to achieve a good bond than a thicker hardstrip.

[0018] Furthermore, as we have seen, the wear strips are vacuum glued using a silicone counter-mold that does not perfectly adapt to certain geometries of the fan blades, resulting in glue accumulation at certain points.

[0019] This glue buildup, in turn, results in fan blades that do not meet required thickness and dimensions.

[0020] Another difficulty encountered with the current method of gluing the hardstrip to the blade is the difficulty in manually (in the left-handed form) positioning the strip to within a few tens of millimeters and in maintaining this positioning of the strip during the operation of mounting the hardstripped blade in the mold and during the vacuum gluing operation.

[0021] Furthermore, once glued, the wear strip serves as a dimensional reference for the blade. Therefore, varying gluing quality can lead to problems in use or negatively impact the final geometry of the component.

[0022] The present invention relates to the above-mentioned technique for manufacturing a composite blade, on the surface of which at least one textile wear strip is fixed in a manner respecting precise positioning and precise dimensions.

[0023] The present invention proposes a simple, effective and economical improvement to this technology. Summary of the Invention

[0024] The invention relates to a turbine blade made of a composite material consisting of woven fibers embedded in a polymer resin, the blade comprising a root portion connected to a blade comprising a pressure side and a suction side via a support portion, at least one textile wear strip being located on the surface of the root portion and / or the support portion, characterised in that the at least one wear strip is fixed in an integral manner to the surface of the root portion by means of the resin.

[0025] In particular, the invention enables one or more wear strips to be precisely positioned on the blade. Furthermore, the invention enables one or more strips to be fixed to the blade without the use of glue, since the resin used to manufacture the blade is used for this fixing.

[0026] The blade according to the invention may include one or more of the following features, taken alone or in combination with one another:

[0027] the blade comprises at least one abradable strip, preferably two abradable strips, on a first surface of the root and / or the support part situated on the pressure side, and at least one abradable strip, preferably two abradable strips, on a second surface of the root and / or the support part situated on the suction side;

[0028] at least one wear-resistant strip has an elongated shape and extends substantially from one end of the root on the side of the leading edge of the blade to the opposite end of the root on the side of the trailing edge of the blade;

[0029] - at least one belt is formed by braiding PTFE and / or aramid fibers;

[0030] - The thickness of at least one strip varies along the length of the strip.

[0031] The invention also relates to a method for manufacturing a blade as described above, using a tool comprising a mold defining a cavity configured to receive a preform of braided fibers, said method comprising the steps of:

[0032] a) positioning at least one wear strip on at least one wall of the mold leading into the cavity,

[0033] b) installing the preform in the cavity and on the wall, and

[0034] c) polymerizing a resin present on the fibers of the preform or injected into the cavity, said resin being configured to solidify the blade and to ensure the fixing of at least one wear strip to said blade.

[0035] In step a), preferably at least one hard-resistant strip is positioned in a groove formed in the wall.

[0036] In step c), the resin is advantageously configured to impregnate the at least one hardstrip. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Other features and advantages will become apparent from the following description of non-limiting embodiments of the invention and with reference to the accompanying drawings, in which:

[0038] [ Figure 1 ] Figure 1 is a schematic perspective view of a composite material blade according to the present invention,

[0039] [ Figure 2 ] Figure 2 yes Figure 1 A larger scale schematic diagram of a portion of a blade, in particular a larger scale schematic diagram of the blade root and the blade support portion where the wear strip is located,

[0040] [ Figure 3 ] Figure 3 is a very schematic cross-sectional view of a tool for manufacturing a blade according to the invention, and

[0041] [ Figure 4 ] Figure 4 is a schematic perspective view of an embodiment of a mold of a tool for manufacturing a bucket according to the invention. DETAILED DESCRIPTION

[0042] First refer to Figure 1 and Figure 2 , Figure 1 and Figure 2 A composite blade 10 for a turbomachine, such as a fan blade, is shown.

[0043] The bucket 10 comprises a blade 12 connected by a support 14 to a root 16 having, for example, the shape of a dovetail and shaped to engage in a pocket of complementary shape of a rotor disk to retain the bucket on this disk.

[0044] The blade 12 includes a leading edge 12a and a trailing edge 12b for gases flowing through the turbine. The blade 12 has a curved or twisted aerodynamic profile and includes a pressure side 18 and a suction side 20 extending between the leading edge 12a and the trailing edge 12b.

[0045] A wear strip 22 made of fabric is fixed to the bucket 10 .

[0046] In the example shown, the bucket 10 includes four wear strips 22 , two on each side of the root portion 16 and two on each side of the support portion 14 .

[0047] As the name implies, the strips 22 are configured to limit wear on the wall to which they are attached, by contact and / or friction. These strips 22 are located on the root 16 and the support 14 which may be in contact with the bearing surface of the aforementioned rotor disk.

[0048] Each strip 22 has a generally elongated shape and extends substantially from the leading edge 12a to the trailing edge 12b of the blade 12. The strips 22 have, for example, a length comprised between 2 and 50 cm and a width comprised between 2 and 7 cm.

[0049] The wear strip 22 is realized by weaving fibers such as aramid fibers and / or PTFE.

[0050] The blade 10 is produced from a composite material of a fiber preform, the fibers of which, for example carbon fibers, are coated with or impregnated with a polymerizable and in particular crosslinkable resin, for example epoxy resin.

[0051] The tool for manufacturing the bucket 10 comprises a mold and a counter-mold defining a cavity between them, the cavity being configured to receive a fiber preform.

[0052] When manufacturing the blade, the tool is opened and the fiber preform is placed in the cavity. This placement can be achieved with a three-dimensionally woven preform or with a fabric that is draped and stacked in the cavity. This step can be done manually or with the aid of a robot. The tool is then closed by attaching the counter-mold to the mold in a sealed manner.

[0053] The preform is pre-impregnated with resin or the resin is injected into the mold to impregnate the preform.

[0054] The tool is heated to increase the temperature of the resin and polymerize the resin.

[0055] After the resin has polymerized and the blades have hardened, the strip 22 is glued to the blades, for example using a phenolic adhesive, in the prior art.

[0056] Currently, this gluing operation is a completely manual operation comprising three steps, namely, the step of coating the tape with glue, the step of positioning the tape, and the step of holding the tape in place until the glue sets.

[0057] As mentioned above, this manual operation is the cause of many defects in the final part.

[0058] The invention proposes to eliminate the manual gluing operation and to carry out the assembly of the belt 22 simultaneously with the operations of polymerization of the resin and hardening of the blades.

[0059] The method of manufacturing a blade according to the invention therefore makes it possible to dispense with the manual gluing operations of the prior art, which makes it possible to solve the problem of obtaining parts that do not meet the requirements and is simpler than the methods currently used.

[0060] In fact, like the methods of the prior art, the method of the invention comprises the use of a tool 24 comprising a mold 26 and a counter-mold 28 defining between them a cavity 30 configured to receive a fiber preform 32 of a blade ( Figure 3 ).

[0061] However, in the method of the invention, before installing the fiber preform 32 in the mold, one or more fabric strips 22 are placed on at least one wall 26 a of the mold 26 or at least one wall 28 a of the counter-mold 28 , which walls 26 a , 28 a open into the cavity 30 .

[0062] The fiber preform 32 is then mounted between the mold 26 and the counter-mold 28 .

[0063] As described above, the preform is pre-impregnated with resin or impregnated by injecting the resin into the mold through port 33. Injecting the resin into the cavity of the tool allows pressure to be applied to the preform and prevents bubbles and microvoids in the final part. The resin is then polymerized.

[0064] In the method of the invention, instead of using two types of resin (resin for impregnating the fibers of the preform and resin or glue for gluing the tapes), only one resin, for example epoxy resin, is used.

[0065] Thus, defects due to a wrong amount of glue, extra thickness or lack of glue between the strip 22 and the blade are avoided.

[0066] In addition, integral components are obtained.

[0067] In order to achieve an accuracy within a few millimeters in positioning and holding the strip 22 , which is the cause of the drawbacks of the prior art methods, the mold 26 advantageously comprises a housing 34 for receiving the strip 22 .

[0068] These housings 34 may be grooves or cutouts formed in the walls 26a, 28a opening into the cavity 30. These housings are advantageously calibrated to the nominal thickness of the strip 22, for example comprised between 0.1 mm and 1.5 mm.

[0069] Thus, the present invention provides several advantages, including:

[0070] - During the curing of the blades, the strips are fixed by resin instead of special glue, making it possible to achieve perfect geometry and precise arrangement of the strips;

[0071] - the variable thickness of the strips no longer has any effect, since they are pressed against the walls of the tool and are received in calibrated housings in these walls;

[0072] - the amount of resin at any point on the strip is optimal, driven by the injection pressure in the tool and / or the closing pressure of the mold; etc.

Claims

1. A turbine blade (10) made of a composite material, the composite material being formed of three-dimensionally woven carbon fibers embedded in a polymeric resin, the turbine blade comprising a root portion (16) connected to a blade (12) comprising a pressure side (18) and a suction side (20) via a support portion (14), at least one textile wear strip (22) being located on the surface of the root portion and / or the support portion, characterized in that The at least one textile hardband is integrally fixed to the surface of the root by the resin and is made by weaving PTFE and / or aramid fibers, the resin used to cure the turbine blade and the resin used to fix the at least one textile hardband being the same and being cured simultaneously.

2. The turbine blade (10) according to claim 1, wherein: The turbine blade comprises at least one first textile wear strip on a first surface of the root portion (16) and / or the support portion (14) on the pressure side (18), and at least one second textile wear strip on a second surface of the root portion and / or the support portion on the suction side (20).

3. The turbine blade (10) according to claim 1 or 2, wherein: The at least one textile wear strip (22) has an elongated shape and extends substantially from one end of the root on the leading edge (12a) side of the blade (12) to the opposite end of the root on the trailing edge (12b) side of the blade.

4. The turbine blade (10) according to claim 1 or 2, wherein: The thickness of the at least one fabric hardstrip (22) varies along the length of the fabric hardstrip.

5. The turbine blade (10) according to claim 1, wherein The turbine blade comprises two first fabric wear strips on a first surface of the root portion (16) and / or the support portion (14) on the pressure side (18), and two second fabric wear strips on a second surface of the root portion and / or the support portion on the suction side (20).

6. A method for manufacturing a turbine blade (10) according to any one of claims 1 to 5, the method using a tool (24) comprising a mold (26), the mold defining a cavity (30) configured to receive a preform (32) of braided fibers, the method comprising the steps of: a) positioning the at least one textile wear strip (22) on at least one wall (26a, 28a) of the mould opening into the cavity, b) installing the preform in the cavity and on the wall, and c) polymerizing a resin present on the fibers of the preform or injected into the cavity, said resin being configured to solidify the turbine blade and to ensure the fixing of the at least one textile hardstrip to the turbine blade.

7. The method according to claim 6, wherein: In step a), the at least one textile wear strip (22) is positioned in a groove (34) formed in the wall (26a, 28a).

8. The method according to claim 6 or 7, wherein: In step c), the resin is configured to impregnate the at least one textile hardstrip (22).

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