Method for manufacturing a fan blade composite material platform and platform thus obtained

Abstract

Method for manufacturing a platform made of composite fan blade material intended to be inserted between two consecutive fan blades spaced transversely from each other, comprising a step (S1) of producing a body preform comprising reinforcing fibers and mainly forming a platform which extends in particular in an axial direction and a transverse direction, the body preform comprising two opposite axial edges which extend axially, are spaced from each other in the transverse direction and are each intended to be arranged opposite a fan blade, characterized in that the method further comprises a step (S2) of producing an axial delink in each of the two opposite axial edges of the body preform. Figure for the abstract: Fig.6 .

Description

Title of the invention: Method for manufacturing a fan blade composite material platform and platform thus obtained Technical field

[0001] The present disclosure relates to a method of manufacturing a fan blade composite material platform. Prior art

[0002] Turbomachine fans, particularly for aircraft, comprise a structure formed of fan blades mounted regularly spaced around the circumference of a fan rotor.

[0003] Blade platforms, generally made of composite material, are mounted in each free space between two consecutive blades, at the base of the latter.

[0004] Each dawn platform generally comprises: - a part forming the body and which has a general platform shape along which the aerodynamic flow crossing the fan (air vein) flows, - as well as two stiffeners placed below the part forming the platform and which allow the entire part to be stiffened and thus ensure satisfactory mechanical strength in the event of ingestion of flying foreign bodies (known in English terminology by the acronym FOD, for “Flying Object Debris”).

[0005] Each blade platform is also provided, on either side thereof in a direction tangential to the circumference of the fan rotor, with two seals which each ensure the seal between the platform and the relevant side blade. One of the two seals ensures the seal between one of the two opposite edges of the platform and the extrados of a side blade and the other seal ensures the seal between the other opposite edge of the platform and the intrados of the other side blade. In a known manner, each seal is bonded to the corresponding edge of the platform.

[0006] Generally, each blade platform ensures the continuity of the aerodynamic vein as well as the tangential positioning of the two lateral blades between which the platform is arranged.

[0007] Given that each blade has, in a known manner, an untwisting, the two seals of two adjacent blade platforms which frame the blade and which are in contact respectively with its extrados face and its intrados face, each have an evolving lip profile. This profile makes it possible to adapt to variations in the clearance to be sealed between the blade and each of the two platforms arranged on either side.

[0008] In order to allow sealing and limit the circulation of air under the plates- teformes, the seals of the two respective platforms which are located on the intrados and extrados of the blade come to encircle the blade. These seals are therefore also in contact with the leading edge and the trailing edge of the blade.

[0009] When the blower thus configured is in service, the seals can give rise to various problems such as seal reversal, detachment, tearing (in fatigue), erosion wear and seal wear due to friction with the fan blade, which leads to local losses of sealing and therefore losses of performance of the blower.

[0010] Furthermore, since the joints are glued, a gluing step itself is therefore necessary in the manufacturing process of the fan platform. Furthermore, with the current configuration of the joints, the gluing surface is limited, which may explain at least in part the detachment problems mentioned above. Statement of the invention

[0011] The present disclosure aims to remedy at least in part these drawbacks. For this purpose, the present disclosure relates to a method for manufacturing a fan blade composite material platform intended to be inserted between two consecutive fan blades spaced transversely from one another, the method comprising a step of producing a body preform comprising reinforcing fibers and mainly forming a platform which extends in particular in an axial direction and a transverse direction, the body preform comprising two opposite axial edges which extend axially, are spaced from one another in the transverse direction and intended to be each arranged opposite a fan blade, characterized in that the method further comprises a step of producing an axial decoupling in each of the two opposite axial edges of the body preform.

[0012] Producing an axial decoupling in each edge constitutes a preliminary step which makes it possible to prepare / configure the preform with a view to the subsequent insertion of a seal in this decoupling, unlike the prior art where, previously, the platform was manufactured by a known manufacturing method, then the seal was subsequently added thereto by gluing.

[0013] According to other possible characteristics: -the method comprises a step of inserting a seal blank into each of the two axial misalignments of the two opposite axial edges of the body preform so that a portion of the seal blank is contained in the axial misalignment and the remaining portion of the seal blank forms a projection outside the axial misalignment; this insertion of the seal blank during the platform manufacturing step makes it possible to reliably secure, effective and durable seal to the platform, thus ensuring a mechanical anchoring in the platform which will withstand the conditions of commissioning and thus avoid at least some of the drawbacks encountered in the prior art (turning over, detachment of the seal, etc.); - the material of the seal is EPDM rubber foam (ethylene-propylene-diene (monomer) rubber); -the method comprises a step of injecting a resin into the body preform so that the body preform is impregnated with resin; -the method comprises a step of co-firing the sealing gasket blanks and the resin-impregnated body preform; -the method comprises, after the co-firing step and obtaining a platform body, a step of machining each of the two opposite axial edges of the body along the two axial and transverse directions and along a third perpendicular radial direction, so as to reduce the radial dimension of each axial edge (thinned axial edge) integrating a seal along the axial and transverse directions; -each axial edge (thinned) has a thickness, taken in the radial direction, which is between 1 and 3 mm; - a waterproofing membrane is added to each sealing joint, in particular to the projecting part of each sealing joint; - each seal has a thickness, taken in the radial direction, which is between 1 and 2 mm; - the body preform mainly forming a platform also comprises two stiffeners which each extend in a third radial direction perpendicular to the two axial and transverse directions, away from the platform or a stiffening system formed of a closed box.

[0014] The invention also relates to a fan blade platform made of composite material intended to be inserted between two consecutive fan blades spaced transversely from one another, comprising a body made of composite material mainly forming a platform which extends in particular in an axial direction and a transverse direction, the body comprising two opposite axial edges spaced from one another in the transverse direction and intended to be arranged each opposite a fan blade, each axial edge being provided with a seal intended to ensure sealing between the body of the platform and the opposite fan blade, characterized in that the seal is integrated into the corresponding axial edge.

[0015] The physical integration of a part of each joint at the axial edge of the platform makes it possible to intimately link the two elements and therefore to ensure better solidarity than simple gluing, which makes it possible to significantly reduce the problems observed on the seals during their use (turning, detachment, tearing, wear due to erosion and fretting). It follows that the sealing provided by these seals partially introduced into the platform is more reliable than in the prior art because it holds up better over time, thus allowing the engine's performance to be maintained. Ice accretion problems are also avoided.

[0016] According to other possible characteristics: -the seal comprises a part mechanically inserted into the axial edge and a remaining part which extends transversely away from the axial edge and projects beyond it; - a sealing membrane is added to each sealing joint, in particular to the remaining projecting part of each sealing joint; -each axial edge has a thickness, taken along a third radial direction perpendicular to the two axial and transverse directions, which is between 1 and 3 mm; - each seal has a thickness, taken in the radial direction, which is between 1 and 2 mm; - the material constituting the sealing gasket is EPDM rubber foam; -the body mainly forming a platform also comprises two stiffeners which each extend in a third radial direction perpendicular to the two axial and transverse directions, away from the platform or a stiffening system formed from a closed box.

[0017] The invention also relates to a turbomachine fan, comprising a fan rotor and a plurality of fan blades distributed over a circumference of the fan rotor and between each of which is mounted a fan blade platform as briefly explained above. Such a fan offers the same advantages as those mentioned above for the platform and they will therefore not be repeated. Brief description of the drawings

[0018] Other characteristics and advantages of the subject of the present disclosure will emerge from the following description of embodiments, given as non-limiting examples, with reference to the appended figures.

[0019] [Fig-1] [Fig.l] is an exploded schematic view of a turbomachine fan according to one embodiment of the invention.

[0020] [Fig.2] [Fig.2] is an enlarged schematic perspective view showing pla blade forms arranged between blades on the fan of [Fig.l], according to one embodiment of the invention.

[0021] [Fig.3] [Fig.3] is an enlarged schematic top view of an upstream portion of the seals framing a blade of [Fig.2].

[0022] [Fig.4] [Fig.4] is an enlarged schematic top view of the downstream part of the seals of [Fig.3].

[0023] [Fig.5] [Fig.5] is a schematic cross-sectional view of the platform dawn of [Fig.l].

[0024] [Fig.6] [Fig.6] is a flowchart of a manufacturing process for a platform in composite fan blade material according to one embodiment.

[0025] [Fig.7] [Fig.7] is an enlarged partial schematic view of an axial edge of the platform body preform being manufactured.

[0026] [Fig.8] [Fig.8] is an enlarged partial schematic view of the axial edge of the [Fig.7] after integration of a sealing gasket and co-firing. Description of the embodiments

[0027] The following description relates to an exemplary embodiment of a composite material platform for a fan blade intended for an aircraft turbomachine in which the fan has a known general configuration illustrated in [Fig.l]. Only the blade platform differs from known blade platforms.

[0028] Generally, the turbomachine fan 10 comprises a fan rotor 12 and a plurality of fan blades 14 (only one blade is shown in [Fig.l]) distributed over an external circumference of the fan rotor in axial cells 16 made in the external surface of the rotor.

[0029] The blower 10 also comprises, in a known manner, a flange 18 arranged upstream of the fan rotor, which is intended to be fixed to the latter. The blower 10 also comprises a downstream flange 20 arranged downstream of the fan rotor, which is intended to be fixed to the latter.

[0030] The fan 10 also comprises a plurality of fan blade platforms 22 which are each intended to be mounted in a space left free between two consecutive blades 14 of the fan. In [Fig.l], only one fan blade platform 22 is illustrated.

[0031] [Fig. 2] shows, in an enlarged partial perspective view from upstream of the fan of [Fig. 1], a plurality of blades mounted on the rotor disk 12 and between which blade platforms 22 are arranged. A space is left free between the two leftmost blade platforms 22 in the figure in order to show the location for a blade 14 and the contour / profile thereof in its section which is engaged between the two platforms 22. Seals (not visible in [Fig. 2]) fixed to a blade platform 22 are arranged on either side of each blade in order to seal the area against the air flow passing through the fan.

[0032] [Fig. 3] is a partial representation (in top view) of the arrangement of a fan blade 14 (of which only the leading edge 14a is seen) between two seals 24, 26, the seal 24 associated with the blade platform 22 (on the left in [Fig.3]) being intended to be in contact with the intrados of the blade, while the seal 26 (associated with a blade platform not visible in the figure) is intended to be in contact with the extrados of the blade. This representation concerns the upstream part of the fan, in the zone (visible in [Fig.2]) where the seals 24 and 26, arranged on either side of the blade 14, are in contact with each other in their upstream part. These seals are lip seals with an evolving profile which allows them to adapt to variations in the clearance to be sealed between the blade and each of the two platforms arranged on either side of this blade.

[0033] It will be noted that there is a significant clearance from platform to platform downstream of the blade due to the blade's movements. This clearance cannot be filled by the platform itself for assembly reasons. In addition to achieving sealing, it is necessary to fill as much as possible the cavity present downstream of the blade.

[0034] [Fig.4] is a partial representation (in top view) of the downstream part of the fan (the blade is not visible here) where the two seals 24 and 26 come into contact with each other in their downstream part thanks to a notch 26a made in the seal 26, thus making it possible to fill the aforementioned clearance as much as possible, while limiting the deformations in the lip of the seals. [Fig.5] represents a possible embodiment of a blade platform 22 according to an embodiment of the invention, according to a cross-sectional view (the platform is shown in perspective in [Fig.1]). This blade platform 22 has a general structure which extends in particular in an axial direction X (visible in [Fig.l]) and a transverse direction Y perpendicular to the axial direction X, in the form of a body 22a having a general platform shape along which the aerodynamic flow passing through the fan (air vein) flows.This body 22a comprises two opposite axial edges 22b, 22c which extend axially (along the X axis) and are spaced from each other in the transverse direction Y over the entire transverse dimension or width of the body. The two edges 22b, 22c are intended to be arranged each opposite an adjacent fan blade. The edge 22b is for example shown in Figures 3 and 4.

[0035] Each axial edge 22b, 22c, called a fusible edge, is intended to be provided with a seal, such as one of the aforementioned seals 24, 26 depending on the edge considered, in order to ensure sealing between the edge of the platform and the facing fan blade,

[0036] The blade platform 22 also comprises two stiffeners 22d, 22e which are arranged below the platform-forming part 22a and which make it possible to stiffen the entire part and thus ensure satisfactory mechanical strength in the event of ingestion of flying foreign bodies (FOD). These stiffeners each extend following a third radial direction (Z) perpendicular to the two axial directions X and transverse Y, away from the platform-forming part 22a.

[0037] Furthermore, as shown in [Fig.5], the blade platform 22 further comprises a generally U-shaped structure with a bottom 22f and two vertical branches 22g, 22h forming two sides which extend axially inside the space defined between the stiffeners 22d, 22e and in contact with the latter (closed box acting as a stiffening system).

[0038] To achieve the shape of the box under the blade platform, it is necessary to add a woven preform which, by co-injection with the main preform (forming the vein and the sides of the stiffeners), forms the final part.

[0039] In a known manner, the blade platforms 22 are made of composite material, for example carbon fibers, manufactured using a known process, such as a three-dimensional weaving process followed by known injection and baking techniques.

[0040] According to this known method, a platform preform is manufactured from reinforcing fibers (e.g. carbon fibers) which are woven according to a 3D weave. This known step is illustrated by step S1 of the method for manufacturing a blade platform according to an embodiment of the invention and a flowchart of which is shown in [Fig.6].

[0041] The preform obtained by 3D weaving then undergoes a known step of injecting resin into a resin transfer mold called RTM (acronym for “Resin Transfer Mold”) and the three-dimensional shape obtained has, for example, the general appearance illustrated in [Fig. 5]. One of the two axial edges of the preform, here the edge 22b', is shown in [Fig. 7] with a part of the body 22a' of the preform. The rest of the preform is not shown for the sake of clarity.

[0042] The edge 22b' is shaped relative to the part of the body 22a' of the preform so as to form a shoulder e, the edge thus extending transversely beyond the body over a part of the thickness, taken along the Z axis, of the latter.

[0043] According to a second step S2 of the method, the formation of an axial decoupling (technique known per se) in each of the two opposite axial edges of the body preform is carried out. The axial decoupling has the purpose of separating, in the radial direction Z, two sides 22b' 1 and 22b' 2 of the edge 22b' in order to create a space D (wallet opening) which will receive a sealing gasket.

[0044] The following step S3 of the method is a step of inserting a blank seal, here the seal 24' (blank seal which will then give rise, after curing, to the seal 24 of the previous figures), into the axial decoupling D of the axial edge 22b' of the body preform 22a'.

[0045] The insertion of the joint blank 24' between the sides 22b' 1 and 22b' 2 of the axial decoupling D is partial ([Fig.8]) in the sense that only a part 24'a of the joint blank joint is contained / imprisoned in the axial misalignment. The remaining part 24'b of the joint blank forms a projection which extends outside the axial misalignment D, transversely beyond it and away from the axial edge. The length ("tangential") of the inserted part is at least equal, or even greater as shown here, than that of the free outer part in order to have sufficient mechanical anchoring in the edge.

[0046] The description is similar for the production of the seal 26 in the opposite axial edge of the preform.

[0047] The material constituting the sealing gasket is for example an EPDM rubber foam (ethylene-propylene-diene (monomer) rubber) which offers very good characteristics in terms of mechanical resistance. Alternatively, the material could be a nitrile butadiene rubber or a styrene butadiene rubber.

[0048] The next step S4 of the method is a step of injecting a resin into the body preform so that the body preform provided with the seal blanks is impregnated / embedded with resin. For example, the woven preform is enclosed in a mold and, in a known manner, a resin injected according to the RTM technique mentioned above. As mentioned above, a polyflex type resin injection technique can alternatively be used.

[0049] The next step S5 of the method is a step of co-firing the seal blanks and the resin-impregnated body preform inside the mold. A temperature is applied to the assembly contained in the mold in order to ensure the polymerization of the resin.

[0050] At the end of this step, the composite material is solidified and the blade platform preform has become a blade platform.

[0051] The following step S6 of the method is a step of machining each of the two opposite axial edges 22b, 22c of the body 22a of the platform along the two axial directions X and transverse Y and along the third perpendicular radial direction Z, so as to reduce the radial dimension or thickness of each axial edge integrating the seal along the axial and transverse directions, thus forming an enlarged shoulder e' and therefore a thinned axial edge 22b. This step takes place on each of the two edges 22b and 22c. [Fig.8] also illustrates the result of this thinning step and the configuration of the thinned edge 22b integrating the seal 24.

[0052] According to a step S7 of the method, a sealing membrane 28 can be added to each seal 24, 26, in particular to the projecting part (only the free part 24b of the seal 24 is shown in [Fig.8]) of each seal. Thus, each seal is covered at least in part by the membrane. In the example described, the membrane covers only the end / edge of the seal. waterproofing membrane 28 is for example liquid, thus forming a liquid waterproofing system. The liquid waterproofing membrane is a material (for example polyurethane) which is in liquid form and which can be applied by brush / roller or by spraying and which, after one hour at 20°C (polymerization of the resin), forms a continuous and elastic membrane, adhering to the support and resistant to cracking, thus ensuring very good waterproofing.

[0053] As shown in [Fig.8], the length (“tangential”) of the part of the seal trapped in the preform (24a, 24'a) is greater than that of the part outside the platform.

[0054] The seal thus integrated into the platform fulfills overall the same function as the seal of the prior art, namely ensuring sealing. It also has the same shape as before and the same clearance as in the prior art is maintained between the platform and the blade. However, its method of direct integration into the platform, during its manufacture, and in particular, during the step of inserting the seal blank into the preform and the resin injection step, makes it possible to intimately bond the seal to the platform (by mechanical anchoring in the material of the edge of the platform, in particular in a transverse and radial direction following the thickness of the edge of the platform) and to prevent subsequent detachment of the seal from the platform. This results in better sealing of the seal thus integrated into the platform because the risks of detachment or reversal of the seal of the prior art are thus avoided.

[0055] In this exemplary embodiment, each thinned axial edge (22b, 22c) has a thickness, taken along the radial direction Z, which is between 1 and 3 mm. Each seal 24, 26 has, for example, a thickness, taken along the radial direction, which is between 1 and 2 mm.

[0056] Although the present invention has been described with reference to specific exemplary embodiments, it is obvious that modifications and changes may be made to these examples without departing from the general scope of the invention as defined by the claims. In particular, individual features of the various illustrated / mentioned embodiments may be combined in additional embodiments. Therefore, the description and drawings should be considered in an illustrative rather than restrictive sense.

Claims

Claims

1. A method of manufacturing a platform (22) made of a composite fan blade material intended to be inserted between two consecutive fan blades (14) spaced transversely from each other, comprising a step (S1) of producing a body preform (22a') comprising reinforcing fibers and mainly forming a platform which extends in particular in an axial direction (X) and a transverse direction (Y), the body preform comprising two opposite axial edges (22b') which extend axially, are spaced from each other in the transverse direction and are each intended to be arranged opposite a fan blade, characterized in that the method further comprises a step (S2) of producing an axial decoupling (D) in each of the two opposite axial edges (22b') of the body preform (22a').

2. Manufacturing method according to the preceding claim, characterized in that it comprises a step (S3) of inserting a seal blank (24') into each of the two axial misalignments (D) of the two opposite axial edges (22b') of the body preform so that a portion (24'a) of the seal blank is contained in the axial misalignment (D) and the remaining portion (24'b) of the seal blank forms a projection outside the axial misalignment.

3. Manufacturing method according to one of the preceding claims, characterized in that it comprises a step (S4) of injecting a resin into the body preform (22a') so that the body preform is impregnated with resin.

4. Manufacturing method according to claims 2 and 3, characterized in that it comprises a step (S5) of co-firing the sealing gasket blanks (24') and the body preform (22a') impregnated with resin.

5. Manufacturing method according to the preceding claim, characterized in that it comprises, after the co-firing step (S5) and obtaining a platform body (22a), a step (S6) of machining each of the two opposite axial edges (22b, 22c) of the body along the two axial (X) and transverse (Y) directions and along a third perpendicular radial direction (Z), so as to reduce the radial dimension of each axial edge integrating a seal (24, 26) along the axial and transverse directions.

6. Manufacturing method according to claim 4, characterized in that a sealing membrane (28) is added (S7) to each sealing joint.

7. A platform (22) made of a composite fan blade material intended to be inserted between two consecutive fan blades (14) spaced transversely from each other, comprising a body (22a) made of a composite material mainly forming a platform which extends in particular in an axial direction (X) and a transverse direction (Y), the body comprising two opposite axial edges (22b, 22c) which extend axially, are spaced from each other in the transverse direction (Y) and are each intended to be arranged opposite a fan blade, each axial edge (22b, 22c) being provided with a seal (24, 26) intended to ensure sealing between the body (22a) of the platform and the opposite fan blade, characterized in that the seal (24, 26) is integrated into the axial edge (22b, 22c) corresponding.

8. Fan blade composite material platform according to the preceding claim, characterized in that the seal (24, 26) comprises a part (24a) mechanically inserted into the axial edge (22b) and a remaining part (24b) which extends transversely away from the axial edge and projects beyond it.

9. Fan blade composite material platform according to the preceding claim, characterized in that a sealing membrane (28) is added to the remaining projecting part of each sealing joint.

10. Fan blade composite material platform according to one of claims 7 to 9, characterized in that the body (22a) mainly forming a platform also comprises two stiffeners (22d, 22e) which each extend in a third radial direction (Z) perpendicular to the two axial (X) and transverse (Y) directions, away from the platform or a stiffening system formed of a closed box.

11. A turbomachine fan (10), comprising a fan rotor (12) and a plurality of fan blades (14) distributed over a circumference of the fan rotor and between each of which is mounted a fan blade platform (22) according to one of claims 7 to 10.

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