Composite platform for a fan of an aircraft turbomachine

Abstract

The present invention relates to a composite platform (30) for a fan of an aircraft turboengine, the composite platform including an elongated wall (32) and configured to extend between two fan blades (3), the wall including an aerodynamic outer surface (32a) and an inner surface (32b), fastening tabs (34) being located on the inner surface, wherein the fastening tabs are configured to be attached to a fan disk (2), characterized in that the fastening tabs are integrally formed with a metallic reinforcement (36), the metallic reinforcement having a plate (38) which has an elongated shape and extends over more than 50% of the longitudinal extent of the wall, and the wall is produced by overmolding a resin on the plate so as to integrate the plate in the wall.

Description

Technical Field

[0001] The present invention relates to a composite platform for a fan of an aircraft turbomotor. Background Art

[0002] The technical background particularly includes the documents EP-A1-3 536 909, US-A1-2019 / 277150, US-A1-2019 / 162119 and EP-A1-2 985 366.

[0003] Reference Figure 1 shows a partial cross-sectional view of a fan rotor 1 of an aircraft turbomotor. It is known from the prior art that the fan rotor 1 has a rotational axis and includes a fan casing, a fan disk 2, and fan blades 3 or vanes. The fan blades 3 or vanes include roots as holding means, and the roots are sleeved in cavities in the outer periphery of the disk 2. Each blade 3 includes a camber, a back, a leading edge 3a and a trailing edge 3b.

[0004] The fan rotor 1 includes platforms 4b inserted between the fan blades 3 and attached to the outer periphery of the disk 2. Each platform 4b includes an aerodynamic outer surface 4c, and the aerodynamic outer surface 4c extends substantially along the axis from the leading edge 3a to the trailing edge 3b of the blade 3. The platform 4b is mounted between the leading edge 3a and the trailing edge 3b.

[0005] Finally, the rotor 1 includes an upstream cone 13, an upstream shroud 14 and a downstream shroud 15, and the two shrouds 14, 15 are fixed to the fan disk 2.

[0006] Such a fan rotor is particularly known from the document EP-A1-1 970 537.

[0007] Each platform must provide an aerodynamic function as its main function and provide the definition of the air flow path.

[0008] In addition, each platform must meet all operating conditions, that is, ensure the performance of the entire operating envelope (for example, the flight envelope of the aircraft), ensure safety requirements, and ensure the availability of the rotor as part of the engine for commercial use.

[0009] In terms of safety, each platform must be able to absorb a large amount of energy by squeezing its side edges, and the side edges extend along the camber of the blade and the back of the adjacent blade.

[0010] It is known to produce fan blades made of composite materials, which are particularly interesting in the aviation field due to their mechanical properties and mass improvement compared to metal alloys.

[0011] The platform is generally made of metal alloy. However, it is not conceivable to use a metal platform for a composite blade because the risk of wear and weakening of the blade due to metal-composite contact is too high.

[0012] Therefore, it has been proposed to provide a fan platform made of composite material. However, the currently known techniques are not entirely satisfactory, especially because the manufacturing methods are time-consuming, complex, and involve high production costs.

[0013] The present invention proposes to solve at least some of these problems in a simple, effective, and economical way. Summary of the Invention

[0014] The present invention relates to a composite platform for a fan of an aircraft turbomachine, the composite platform comprising a wall having an elongated shape and configured to extend between two fan blades, the wall comprising an aerodynamic outer surface and an inner surface, and attachment tabs located on the inner surface and configured to attach to a fan disk, characterized in that the attachment tabs are formed as a single piece with a metal frame, the metal frame comprising a plate having an elongated shape and extending over more than 50% of the longitudinal extent of the wall, and the wall is produced by overmolding resin on the plate such that the plate is integrated into the wall.

[0015] The platform according to the invention is designed to reduce its mass while increasing its stiffness and its service life. By overmolding resin on the frame (including the attachment tabs of the platform), the manufacturing is relatively simple. The plate is integrated into the wall and strengthens the wall over most of its length. Thus, there is no specific mechanical assembly step, such as screwing, which simplifies the manufacturing and reduces the manufacturing cost of the components.

[0016] The platform according to the invention may include one or more of the following features taken individually or in combination with each other:

[0017] - The plate extends to the upstream and downstream ends of the wall.

[0018] - The wall includes at least one curved side edge, and the plate includes at least one side edge arranged to be offset relative to the side edge of the wall.

[0019] - The wall includes a concave-curved side edge and a convex-curved opposite side edge, and the plate includes two side edges arranged to be offset relative to the side edges of the wall.

[0020] - The plate is at least partially coated with a bonding primer, and / or the outer surface of the wall is at least partially coated with a damping layer.

[0021] - The resin is selected from, for example, the following materials and their mixtures: polyaryletherketone, polyetherimide, semi-aromatic polyamide, and polyamide.

[0022] - The resin is reinforced by a reinforcement member, the reinforcement member including fibers and / or possibly including at least one pre-impregnated overlap portion.

[0023] - The reinforcement member projects from the inner surface of the wall and is made of resin.

[0024] - The plate includes an outer surface and an inner surface connected to the attachment tab, the reinforcement member extending at the level of the outer surface and the inner surface of the plate or even extending into the reinforcement member.

[0025] The invention also relates to an aircraft turbomachine, characterized in that the aircraft turbomachine includes a fan, the fan including a disk carrying blades and a platform as described above. Description of the Drawings

[0026] Other features, objects, and advantages of the invention will become apparent from the following detailed description and the drawings given as non-limiting examples, in which:

[0027] Figure 1 is a schematic axial cross-sectional view of a fan rotor according to the prior art.

[0028] Figure 2 is Figure 1 a schematic perspective view of the fan rotor of

[0029] Figure 3 is a schematic perspective view of a composite platform seen from above or from the outside, which does not form part of the invention.

[0030] Figure 4 is along Figure 3 a schematic cross-sectional view along line IV-IV of

[0031] Figure 5 is from below or from the inside of Figure 3 another schematic perspective view of the platform of

[0032] Figure 6 is a schematic perspective view of a composite platform according to an embodiment of the invention.

[0033] Figure 7 is along Figure 6 a schematic cross-sectional view along line VII-VII of, and

[0034] Figure 8 is according to Figure 6 a schematic cross-sectional view along line VIII-VIII of. Detailed Description

[0035] Figure 1 has been described above, and Figure 2 shows Figure 1Perspective view of a part of the fan rotor 1. Figure 1 and Figure 2 shows the prior art.

[0036] The rotor 1 is mounted to rotate about a rotational axis and includes a fan disk 2 and fan blades 3, the fan blades 3 including roots that are sleeved in cavities in the outer periphery of the disk 2, wherein Figure 2 only one blade 3 is visible therein. Each blade 3 includes a camber, a back, a leading edge 3a, and a trailing edge 3b.

[0037] The outer periphery of the disk 2 is advantageously serrated by being provided with teeth 16, the teeth 16 advantageously having a trapezoidal cross-section and extending axially on the disk 2 relative to the rotational axis of the rotor 1. At least one wedge 17 is provided on the upstream side between two adjacent teeth 16, the two adjacent teeth 16 forming a cavity for receiving the root of the blade 3, the wedge 17 being intended to axially block the root of the blade in its corresponding cavity.

[0038] A platform 4 is inserted between the fan blades 3 and attached to the outer periphery of the disk 2. Thus, each platform 4 can be inserted between two consecutive fan blades 3.

[0039] Each platform 4 includes an inner surface 4b (or a surface radially internal with reference to the axis) and an aerodynamic outer surface 4a. These surfaces 4a, 4b extend substantially along the axis from the leading edge 3a of two blades 3 to the trailing edge 3b, the platform 4 being mounted between the leading edge 3a and the trailing edge 3b.

[0040] At the upstream end of the platform (with reference to the flow of gas in the fan and the turbomachine), each platform 4 includes an outer edge 5 for attachment or hooking to the disk 2. A similar outer edge 9 is located at the downstream end of each platform 4.

[0041] The inner surface 4b of each platform 4 is connected to an attachment tab 6 on a flange 8 of the disk 2. The tab 6 extends radially inwards and includes a hole at its radially inner free end for a screw 7 to pass through to attach the tab and the platform 4 to the flange 8 and thus to the disk 2.

[0042] Figure 1 and Figure 2 The platform 4 visible in

[0043] Figures 3 to 5 is made of a single metal alloy component, and the present invention proposes a composite platform that can be used, for example, with fan blades also made of composite materials.

[0044] Figures 2 to 5 The composite platform 20 of

[0045] The wall 22 includes an aerodynamic outer surface 22a and an inner surface 22b, and attachment tabs 24 similar to the above-mentioned tabs 6 are located on the inner surface 22b.

[0046] The attachment tabs 24 are made of a metal alloy and include a hub 24a that is connected to ears 24b, and the ears 24b are perforated with holes 24c through which screws (similar to the above-mentioned screws 7) pass.

[0047] The hub 24a is flat and applied to the inner surface 22b of the wall 22. The wall 22 is made of a composite material from a resin. The wall 22 basically includes a hole in its middle, which is aligned with the hole in the hub 24a and receives a screw 26 for attaching the tab 24 to the wall 22. Each screw 26 includes a head and a threaded rod. The head is preferably a countersunk head and engages in a recess on the outer surface 22a of the wall, and a nut supported on the hub 24a is screwed onto the threaded rod.

[0048] This composite platform technology is not entirely satisfactory because it has the following disadvantages.

[0049] - The positioning of the tabs 24 on the wall 22 requires high precision (and thus high cost) to comply with the geometric constraints imposed by aerodynamics. In addition, the screw heads 26 must be covered to maintain the aerodynamic geometry of the duct, which also incurs additional costs by adding a covering step, and the control of the covering step is delicate and complex. In addition, the fact that the screw heads are covered with a coating makes it more difficult to position the screw heads, for example, to finally disassemble the tabs and remove the platform to replace the platform.

[0050] - Each platform 20 has a large mass, about 1 kilogram per platform 20. For example, a fan rotor includes 18 platforms 20.

[0051] - At the level of the hub 24a and the screw 26, an excessive thickness of the wall 22 is required to reduce the clamping force generated in the wall due to the clamping of the hub and the screw; the clamping must also withstand the centrifugal force seen by the components: the clamping characteristics must be greater than the sum of the compressive force and the centrifugal force (F 夹持 >F 压紧 +F 离心 ).

[0052] The clamping force is more difficult to maintain because the countersunk heads of the screws 26 cannot support the washers in a straight line with their heads, which contributes to a poor distribution of the clamping force and requires a smaller volume of material.

[0053] - The geometric behavior of each platform 20 during engine operation is caused by centrifugal force. The slightest deformation results in a loss of efficiency of the fan. Similarly, the use of screws 26 with countersunk heads reduces the volume of material loaded by the components and significantly increases the local constraint, especially at the level of the screw heads.

[0054] These latter two points create the need for a very controlled tightening of the screws (torque wrenches) and are therefore expensive.

[0055] - After the step of covering the screw heads comes durability. In principle, the components should function throughout the life of the engine without degradation. Corrosion combined with local constraint casts doubt on the possibility of meeting this criterion.

[0056] The present invention makes it possible to remedy at least some of these problems and to propose a platform, an embodiment of which is shown in Figures 6 to 8 in.

[0057] The composite platform 30 includes an elongated wall 32 configured to extend between two fan blades.

[0058] The wall 32 includes an aerodynamic outer surface 32a and an inner surface 32b, and tabs 34 attached to the fan disk are located on the inner surface 32b.

[0059] The wall 32 further includes an upstream edge 32c, a downstream edge 32d, a concave - curved side edge 32e, and a convex - curved side edge 32f. It should be understood that the concave - curved edge 32e extends along the camber of the blade from the leading edge to the trailing edge of the blade, and the convex - curved edge 32f extends along the camber of the adjacent blade from the leading edge to the trailing edge of the adjacent blade. At each axial end of the wall, at the level of the edges 32c, 32d, the wall may have flanges or form steps. These ends are intended to cooperate with the shroud of the fan rotor, as mentioned above with respect to Figure 1 .

[0060] The attachment tabs 34 are formed integrally with a metal frame 36, and the metal frame 36 is at least partially integrated in the wall 32, and the wall 32 is made by resin overmolding onto the frame 36 such that no attachment screws etc. are used.

[0061] The frame 36 includes a plate 38 that extends along the wall 32 for at least 50% of the longitudinal extent of the wall 32 and is connected to the attachment tabs 34. As can be seen from Figure 7 : the plate 38 can extend to the upstream and downstream ends of the wall 32. Figure 8It is shown that the plate 38 includes two side edges 38a, 38b, and the two side edges 38a, 38b are arranged to be set back relative to the side edges 32e, 32f of the wall 32. Therefore, the edges 32e, 32f of the wall 32 are made of resin and do not include any metal parts of the plate, which is particularly important because in the case of blade breakage, these edges may contact the blade and may be broken by the blade. For safety standards, the "fuse" function of these edges is indeed an important criterion for these platforms.

[0062] The frame 36, in particular the plate 38, can be at least partially coated with a bonding primer or subjected to a surface treatment to improve the mechanical strength of the resin on the frame.

[0063] The frame 36 can be made of aluminum, titanium or steel and can be manufactured by casting, forging, stamping and welding, machining, electrocorrosion or additive manufacturing, etc. The frame 36 can be hollow and / or recessed.

[0064] The resin of the wall 32 is thermoplastic or thermosetting and is, for example, selected from the following materials and their mixtures: polyaryletherketone, polyetherimide, semi-aromatic polyamide and polyamide.

[0065] Preferably, the resin is strengthened by a reinforcement 40 including fibers (e.g., glass or carbon), and / or may be strengthened by at least one pre-impregnated lap joint. For example, the lap joint can be woven or non-woven and is formed of carbon fiber, thermoplastic (PET), glass, aramid, etc.

[0066] As seen in Figure 7 the reinforcement preferably extends along the entire longitudinal extent of the wall 32. Figure 8 It is shown that the reinforcement 40 further extends across the entire transverse extent of the wall 32.

[0067] The reinforcement 40 also extends into a stiffener 42 protruding from the inner surface 32b of the wall 32.

[0068] The reinforcement 40 and the resin cover the outer surface 38c and the inner surface 38d of the plate 38, and the inner surface is connected to the attachment tab 34.

[0069] The outer surface 32a of the wall 32 can be at least partially coated with a damping layer (not shown). This layer (dual-material overmolding, painting, film bonding, etc.) can contribute to the modification of the natural frequency of the component or the dynamic manipulation of the entire fan rotor.

[0070] The platform 30 is made by overmolding resin on the frame by injecting the resin hot into a mold, which is well known to those skilled in the art. The injection temperature in the mold depends on the resin and is, for example, between 100°C and 400°C (for example, between 100°C and 300°C for thermosetting resins and between 150°C and 400°C for thermoplastic resins). When using a thermoplastic prepreg type of carbon reinforcement 40, the melting temperature of the prepreg thermoplastic is preferably lower than the processing temperature of the injected thermoplastic.

[0071] The present invention provides several advantages:

[0072] - By eliminating screws, nuts, and washers, a mass saving of 10% to 20% per component is estimated. The mass of the platform can be minimized by an optimized design of the frame (thickening at the constrained positions, possibly hollowing out or perforating the frame, optimizing the shape and dimensions of the frame, etc.).

[0073] - Ensure that the aerodynamic surface 32a remains smooth over time without disturbing the air flow. Next, after the component is globally strengthened due to the frame and / or reinforcement and / or stiffener, the screws are eliminated and the component is better held.

[0074] - Benefit from the price of the component because it may not be necessary to perform a re-contact operation at the exit of the mold. Instead of assembling several components, there is only one component because it integrates several functions (stiffener, fusible edge, etc.).

[0075] - Simplify installation and manufacturing. Once the component is made, it can be installed directly. The geometry and dimensions of the component are ensured by the mold. The final geometry is controlled because the metal frame is directly positioned in the mold, enabling the reproducibility of the shape to be ensured.

[0076] - Increase the service life of the component because the clamping constraint is zero and the forces pass through the metal reinforcement.

Claims

1. A composite platform (30) for a fan of an aircraft turbomachine, the composite platform comprising: - a wall (32) of elongate shape configured to extend between two fan blades (3), the wall comprising an aerodynamic outer surface (32a) and an inner surface (32b), the wall having a first longitudinal dimension, - a metallic frame configured to be attached to a fan disk (2), the metallic frame being formed in one piece with a first part and a second part: - the first part forming an attachment tab, - the second part forming a plate (38) having an elongate shape, the plate having a second longitudinal dimension which is at least 50% and at most 100% of the first longitudinal dimension, wherein the wall is produced by overmolding resin onto the plate such that the wall surrounds the plate and the attachment tab extends inwards from the wall.

2. The composite platform (30) according to claim 1, wherein, The second longitudinal dimension is 100% of the first longitudinal dimension.

3. The composite platform (30) according to claim 1, wherein The wall (32) comprises at least one curved side edge (32e, 32f), and wherein the plate (38) comprises at least one side edge (38a, 38b) arranged to be offset relative to the at least one side edge of the wall.

4. The composite platform (30) according to claim 1, wherein, The wall (32) comprises a first concave curved side edge (32e) and a second convex curved opposite side edge (32f), and wherein the plate (38) comprises two side edges (38a, 38b) arranged to be offset relative to the first and second side edges of the wall.

5. The composite platform (30) according to claim 1, wherein, The plate (38) is at least partially coated with a bonding primer, and / or the aerodynamic outer surface (32a) of the wall (32) is at least partially coated with a damping layer.

6. The composite platform (30) according to claim 1, wherein, The resin comprises at least one of the following materials: polyaryletherketone, polyetherimide, semi-aromatic polyamide and polyamide.

7. The composite platform (30) according to claim 1, wherein, The resin is reinforced by a reinforcement (40), the reinforcement comprising fibres or at least one pre-impregnated ply.

8. The composite platform (30) according to claim 1, wherein, A stiffener (42) projects from the inner surface (32b) of the wall (32) and is made of resin.

9. The composite platform (30) according to claim 7, wherein, The second part of the metallic frame comprises an outer surface (38c) and an inner surface (38d), and wherein the reinforcement (40) extends over the outer and inner surfaces of the second part.

10. The composite platform according to claim 7, wherein, A stiffener (42) projects from the inner surface (32b) of the wall (32) and is made of resin, the second part of the metallic frame comprises an outer surface and an inner surface, and wherein the reinforcement comprises fibres or at least one pre-impregnated ply, the reinforcement extends over the outer and inner surfaces of the second part and extends into the stiffener.

11. The composite platform according to claim 1, wherein, The second part of the metallic frame comprises an outer surface and an inner surface, and wherein the wall is produced by overmolding the resin onto the outer and inner surfaces of the second part.

12. An aircraft turbine engine, characterized in that, The turbomachine comprises a fan, the fan comprising a disk carrying blades (3) and one or more composite platforms (30) according to claim 1.

13. A composite platform for a fan of an aircraft turbomachine, the composite platform comprising: - a wall of elongate shape configured to extend between two fan blades, the wall comprising an aerodynamic outer surface and an inner surface, the wall having a first longitudinal dimension, - a metallic frame configured to be attached to a fan disk, the metallic frame being formed in one piece with a first part and a second part: - the first part forming an attachment tab, - the second part forming a plate, the plate having an elongate shape, the plate having a second longitudinal dimension, the second longitudinal dimension being at least 50% of the first longitudinal dimension, wherein the wall is produced by resin overmolding onto the plate, and wherein the composite platform further comprises a reinforcement projecting from the inner surface of the wall such that the wall surrounds the plate, and the attachment tab extends inwardly from the wall.

14. The composite platform according to claim 13, wherein, The reinforcement is made of resin.

15. The composite platform according to claim 14, wherein, The resin is used to produce the wall and the reinforcement.

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