Variable-pitch vane made of composite material for an unducted fan of an aircraft

Abstract

The present invention relates to a variable-pitch vane (100) made of a composite material for an unducted fan of an aircraft, the vane comprising: a fibrous reinforcement formed as a single piece of three-dimensional fabric comprising an airfoil portion (102) and a root portion (104) forming a retaining bulb and intended to be connected to a variable-pitch mechanism (20), the three-dimensional weaving being carried out continuously between the root portion and the airfoil portion, the fibrous reinforcement defining an internal shaping cavity (111) formed by a separation (D1) extending inside the root portion and the blade portion, wherein a matrix densifies the fibrous reinforcement and reinforcing metal shells (105) are arranged around the root portion.

Description

Description Title of the invention: Variable-pitch composite material blade for an unducted aircraft fan Technical Field

[0001] The invention relates to an unducted variable pitch fan blade for an aircraft, as well as an associated fan. Prior art

[0002] The advantage of unducted fan engines is that the fan diameter is not limited by the presence of a shroud, so it is possible to design an engine with a high bypass ratio, and therefore reduced fuel consumption.

[0003] Thus, in this type of engine, the fan blades can have a large span.

[0004] In addition, these engines generally include a mechanism for modifying the pitch angle of the blades in order to adapt the thrust generated by the fan according to the different phases of flight.

[0005] Intense vibration excitation can occur at high rotational speeds on unducted architectures due to the effects of engine installation on the aircraft and the direction of the upstream infinite flow. Indeed, an unducted engine is influenced by the ground and the fuselage, which causes a distortion in the blade feed, in flow velocity, according to the engine azimuths. This results in a vibration response of the blades on the first engine orders IN, 2N and 3N (possibly more). On the other hand, in the absence of an air inlet duct, the direction of the air flowing through the blades is not parallel to the engine axis. This sideslip angle results in forces, called "IP", which cause a vibration response of the blades on the engine order IN. Similarly, these IP forces can also appear during the climb or approach phases of the aircraft because the air flows through the blades at an angle of incidence.These high-speed vibration excitations generate very significant stress cycling across the entire blade assembly. In particular, the part of the blade root located between the hub and the duct, also called the "stilt", is a loaded and critical area due to its blade retention function. FR 3 112 819 is known, which discloses a variable-pitch blade root. having a retention bulb and which is reinforced by added metal shells to limit premature wear of the blade. This solution was proposed in order to address the drawbacks encountered with a broached attachment. Nevertheless, the mechanical strength of such a blade can still be improved.

[0006] The present invention proposes to reinforce a variable-pitch composite material blade for an unducted aircraft fan, in particular in order to improve its resistance to “IP” forces. Statement of the invention

[0007] The present invention relates to a variable-pitch composite material blade for an unducted aircraft fan, comprising: - a fibrous reinforcement, formed in a single piece of three-dimensional fabric, comprising a blade part, and a root part forming a retention bulb and intended to be connected to a variable wedging mechanism, the three-dimensional weaving being carried out continuously between the root part and the blade part, the fibrous reinforcement defining an internal shaping cavity, formed by a delinking, extending inside the root part and the blade part, - a matrix densifying said fibrous reinforcement, and - metal reinforcement shells added around the foot part.

[0008] The invention implements a mono-texture reinforcement, obtained by three-dimensional weaving, between the root and the blade with reinforcement of the outer part of the composite root by metal shells. The continuity of the three-dimensional weaving between the root and the blade facilitates the transmission of forces without creating a mechanically weak interface. In addition, this continuity of weaving makes it possible to directly ensure the retention of the blade on the root, without having to create a securing interface as in the case where an extension of the root is introduced and fixed inside the blade as proposed by FR 3 112 819.

[0009] In an exemplary embodiment, the blade portion defines two second internal shaping cavities, formed by a second separation, opening onto the root portion and located on either side of the shaping cavity, the metal shells being partly housed in the second shaping cavities.

[0010] The extension of the shells into the second cavities prevents the transmission of aerodynamic forces from the blade to the shells via the composite material, which would subject the boundary between the metal shells and the composite material to significant shear forces which could, in certain cases, lead to a detachment. The metal shells directly transmit aerodynamic forces to the retention zone via bending forces. In addition, the shells are inserted into the second cavities in a simple manner during manufacturing, from the bottom of the blade part, i.e. from its lower end along a longitudinal direction of the blade.

[0011] In particular, a larger transverse dimension defined between the metal shells, measured in the chord direction, may be substantially constant in the second shaping cavities.

[0012] This feature is possible because the retention of the blade in the vein is not ensured by a narrowing of the section but by a continuity of fibers. It makes it possible to simplify the shape of the shells and facilitate their insertion into the cavity during manufacturing.

[0013] In particular, a shaping element made of honeycomb or porous material, distinct from the metal shells, may be present in each of the second shaping cavities.

[0014] The use of this or these shaping elements having a low density advantageously contributes to lightening the blade. In addition, as for the shells, a simple insertion is allowed from the bottom of the blade part during manufacture, thus avoiding having to provide an opening by uncoupling at the level of an edge to be able to introduce these elements.

[0015] In an exemplary embodiment, the blade portion may comprise, over a section of its longitudinal dimension adjacent to the root portion, a main woven portion defining a leading edge and a trailing edge, said main portion being separated on the second uncoupling into woven skin portions each delimiting a second shaping cavity, and into an intermediate woven portion located between the skin portions, said intermediate portion being separated on the uncoupling into two uncoupling portions delimiting the shaping cavity.

[0016] In an exemplary embodiment, the blade further comprises a shaping part present in the internal shaping cavity, said shaping part being hollow at least on a lower longitudinal end of the blade.

[0017] Such a characteristic advantageously makes it possible to place in the hollow part of the shaping part one or more masses which contribute to improving the balancing of the rotor.

[0018] In an exemplary embodiment, the foot portion includes a mounting portion, defining the retention bulb, and a stilt portion that transitions between the mounting portion and the blade portion, the metal shells extending around the mounting and stilt portions.

[0019] In an exemplary embodiment, the fiber reinforcement is formed from carbon fibers, glass fibers, aramid fibers, or a mixture of such fibers. The fiber reinforcement is advantageously formed from carbon fibers.

[0020] In one embodiment, the matrix is ​​an epoxy resin.

[0021] The person skilled in the art will recognize that other resins are conceivable and that the resin used may be thermosetting or thermoplastic.

[0022] The present invention also relates to an unducted fan for mounting on an aircraft comprising a hub comprising blade attachment portions, and a plurality of blades as described above mounted on the attachment portions. Brief description of the drawings [Fig. 1] Figure 1 schematically represents a section, taken perpendicular to a chord direction, of an example of a blade according to the invention connected to a variable setting mechanism, [Fig. 2] Figure 2 schematically represents the blade of Figure 1 in section in a plane containing the chord and longitudinal directions, [Fig. 3] Figure 3 schematically represents the blade of figures 1 and 2 in section plane III-III, perpendicular to the longitudinal direction, and located at a first height in the blade part, [Fig. 4] Figure 4 illustrates an example of a possible fiber arrangement in the III-III section plane in the shaped rough state. [Fig. 5] Figure 5 schematically represents the blade of figures 1 and 2 in the section plane VV, perpendicular to the longitudinal direction, and located at a second height in the blade part, greater than the first height. [Fig. 6] Figure 6 schematically represents an example of an engine including an unducted fan comprising several blades according to the invention. Description of the embodiments

[0023] The invention is now described by means of figures, present for descriptive purposes to illustrate certain embodiments of the invention and which should not be interpreted as limiting the latter.

[0024] Figures 1 and 2 show sections along two perpendicular planes of an example of a blade 100 according to the invention. The blade 100 comprises a fiber reinforcement formed in a single piece of three-dimensional fabric which comprises a blade portion 102, and a root portion 104 forming a retention bulb. The fiber reinforcement can be formed from carbon fibers, glass fibers, aramid fibers, or a mixture of such fibers. The blade 100 extends in a longitudinal direction DL which corresponds to its span direction, or height direction. When the blade is mounted on the unducted fan, the root portion 104 is connected to a variable pitch mechanism 20, the principle of which is known per se, which makes it possible to modify the pitch angle of the blade 100 around a pitch axis Y, in order to adapt the performance of the engine to the different phases of flight. The Y-axis of calibration here extends along the DL direction.The part 104 corresponds to the part located below the limit 103 of the aerodynamic vein in the direction DL, and the part 102 corresponds to the part located above this limit 103 in the direction DL. The limit 103 separates the part 102 from the part 104. The part 104 can form a lug 104c at the lower longitudinal end intended to control the setting of the blade in the event of over-torque occurring for example during bird ingestion. Any other device making it possible to achieve a secondary force passage can be an alternative.

[0025] In Figure 6, the engine 200 shown is an unducted type engine (called “open rotor”). The engine 200 comprises a nacelle intended to be fixed to a fuselage of an aircraft, and an unducted fan 204. The invention is also applicable to turboprop type architectures. In Figure 6, the fan rotor comprises a hub rotatably mounted relative to the nacelle and the blades 100 are fixed to the hub and are mounted inside the variable pitch mechanism 20 formed in the hub. The part 104 is rotatably mounted inside the mechanism 20 formed in the hub, by means of balls 22 or other rolling elements.

[0026] The portion 104 comprises a mounting portion 107a, defining the retention bulb, which is housed in the mechanism 20, and a stilt portion 107b which provides the transition between the portion 107a and the blade portion 102.

[0027] The retention bulb defines an upper frustoconical portion 104a in the direction DL, called the upper bearing surface, which has a section, taken transversely to the direction DL, which decreases when moving towards the part 102 so as to cooperate with a bearing surface 24 of the mechanism 20 to ensure the retention of the blade 100 subjected to the centrifugal force, as well as the absorption of the bending forces. The retention bulb further defines a lower frustoconical portion 104b in the direction DL, called the lower bearing surface, which has a section, taken transversely to the direction DL, which decreases when moving away from the part 102. This portion 104b rests on the bearing surface 26, which here corresponds to a barrel which is movable in the direction DL relative to the inner bearing ring bearing on the bearings, and makes it possible to apply a pre-load when mounting the blade root in the mechanism 20, that is to say that the root is pressed between the upper bearing surface and the lower bearing surface. A locking member can be introduced through the orifices TJ and 29 so as to maintain the retention bulb in compression between the bearing surfaces 24 and 26.

[0028] An organic matrix made of thermosetting or thermoplastic resin, for example epoxy resin, densifies the fibrous reinforcement by filling its porosity and coating the fibers of this reinforcement. The portion 104 is, in addition, reinforced by added metal shells 105 which extend substantially over its entire height, measured along the direction DL, and extend, in the example considered, into the portion 102, as will be detailed below. The shells 105 extend in particular around the portions 107a and 107b. The shells 105 are imprints of the portion 104 and have a complementary shape. In particular, the shells 105 take on the shape of the retention bulb and of the portion 107b. The shells 105 surround in particular the internal shaping cavity 111, which will be described below.The part 104 is located between the cavity 111 and the shells 105, and in the example illustrated a fraction of the part 102 is located between the cavity 111 and the shells 105. The shells 105 may be made of titanium, titanium alloy, such as TA6V, steel, aluminum or aluminum alloy. The shells 105 may be made by a forging process, coupled if necessary with a mechanical or chemical machining process. They are then attached around the part 104, preferably with a film of adhesive at the interface to improve the adhesion of the assembly after formation of the matrix. If a film of adhesive is used, it is deposited on the inner surface of the shells 105 which may, beforehand, have been treated chemically or dry (for example by laser). The polymerization of the glue film (if present) is carried out during the formation of the organic matrix, and in particular during the polymerization of the resin used to obtain this matrix.

[0029] The fiber reinforcement is made by three-dimensional weaving of first yarns, generally extending along the DL direction, with second yarns, generally extending along the DC chord direction. By "three-dimensional weaving" or "3D weaving" is meant here a fabric in which at least some of the first yarns bind second yarns over several layers of second yarns. The three-dimensional weaving may be in an "interlock" weave, this case being only one example among others as the person skilled in the art will recognize. The first yarns may be warp yarns and the second yarns may be warp yarns. weft or vice versa, the roles between warps and wefts being able to be reversed in the present text. The three-dimensional weaving is carried out continuously between the parts 104 and 102, thus first threads woven with second threads in the part 104 extend into the part 102 and are woven there with second threads. The first threads ensure textile continuity between the parts 102 and 104, these two parts being formed in one piece by the same piece of fabric.

[0030] The fibrous reinforcement is obtained by shaping a fibrous blank which has been woven in one piece between the parts 102 and 104 and by providing gaps whose structure and function will now be detailed in connection with figures 3 to 5. The formation of such a blank uses weaving techniques known per se.

[0031] Figure 3 shows the blade 100 according to the section plane III-III, taken at a first height on the part 102. A similar structure is verified on the entire section T of the part 102 which is adjacent to the part 104. In this view, the second wires extend between a leading edge 106 located upstream and a trailing edge 108 located downstream. Unless otherwise stated, the terms “upstream” and “downstream” are taken with reference to the direction of air flow around the blade 100.

[0032] A first uncoupling DI is made in the chord direction DC. The uncoupling DI is made in part 102 as well as in part 104. In a manner known per se, an uncoupling is made between two layers of warp threads by not passing weft threads through the uncoupling zone so as not to link threads of warp layers located on either side of the uncoupling. The uncoupling DI defines an uncoupling (or non-woven) zone extending in the chord direction DC and in the longitudinal direction DL. The uncoupling DI defines a first internal shaping cavity 111 in which a shaping part 112 is housed, which makes it possible, among other things, to shape the root as well as a part of the blade. The presence of this part 112 makes it possible in particular to simplify obtaining the shape of the retention bulb, thus avoiding having to resort to complex weaving to obtain this shape.In the example considered, the part 112 is an integral part of the blade 100 mounted on the fan, but it would not be outside the scope of the invention if this part were removed or eliminated after formation of the matrix and before mounting on the engine. The part 112 may be solid or hollow. It may be made of metallic material, of composite material, for example an organic matrix with a reinforcement based on long or short fibers, or of cellular or porous material, such as a foam. As illustrated in FIGS. 1 and 2, the part 112 may have a hollow portion 119 at least on a lower longitudinal end of the blade 100 which may contain masses to improve the balancing of the rotor. The portion 119 may have a shape of revolution around the direction DL.

[0033] The uncoupling DI is formed by omitting to weave second yarns with first yarns so as to separate the woven fibrous portion 120 into two woven fibrous portions 122 and 124 and uncoupled, which can be separated from each other on the uncoupling DI so as to define the cavity 111 and be able to accommodate the part 112 therein. The portions 122 and 124 ensure the continuity of first yarns between the parts 102 and 104. The uncoupling DI extends from an upstream end D11, located on the side of the leading edge 106, to a downstream end D12, located on the side of the trailing edge 108. The portion 120 separates into two portions 122 and 124 from the end D11 and these portions 122 and 124 are woven together from the end D12 to reform the portion 120.Portions 122 and 124 have been shown having substantially the same dimension along a thickness direction DE, transverse to the chord direction DC, but it is of course not outside the scope of the invention when this is not the case. It will be noted that the end D11 is spaced from the leading edge 106 and that the end D12 is spaced from the trailing edge 108. No separation is made at the leading edges 106 or trailing edges 108.

[0034] In the illustrated example, a second uncoupling D2 is produced in the chord direction DC. The uncoupling D2 is formed between an upstream end D21 and a downstream end D22. The uncoupling D2 defines a uncoupling (or non-woven) zone extending in the chord direction DC and in the longitudinal direction DL. A main woven fibrous portion 130 defines the leading edge 106 and is separated, from the end D21, into three woven portions: the portions 132 and 134, called skin portions, which define the aerodynamic profile of the blade and form the extrados and the intrados, as well as the portion 120 which was previously described, called the intermediate portion which is located between the skin portions 132 and 134. More precisely, the delinking D2 makes it possible to define two second internal conformation cavities 136 and 138 which are located on either side of the cavity 111 and partially surround it.More specifically, the cavity 136 is delimited, on one side, by the joining of the portions 120 and 122, and by the portion 132, on an opposite side. The cavity 136 is located between the portion 132 and the portion 122, or between the portion 132 and the cavity 111. The cavity 136 is located on the extrados side and is present between the extrados and the portion 122, or between the extrados and the cavity 111. The cavity 138 is, for its part, delimited, on one side, by the joining of the portions 120 and 124 and by the portion 134, on an opposite side. The cavity 138 is located between the portion 134 and the portion 124, or between the portion 134 and the cavity 111. The cavity 138 is located on the intrados side and is present between the intrados and the portion 124, or between the intrados and the cavity 111. It will be noted that the portions 132 and 134 each have a dimension, taken in the direction DE, which decreases as one moves away from the end D21 over at least a fraction of their dimension in the direction DC. The cavities 136. and 138 are located inside the blade portion 102 and open at the level of the root portion 104, that is to say at the level of the limit 103 of the aerodynamic vein.

[0035] The elements 140 and 142 participate in giving the desired shape to the aerodynamic profile of the blade 100. The elements 140 and 142 are made of a cellular material, such as a honeycomb, or porous material such as a foam. A layer of organic matrix may be present on the lower longitudinal end of the portion 102 (along the vein boundary 103) so as to isolate the elements 140, 142 from the outside in the blade ready to be mounted on the fan.

[0036] Furthermore, the shells 105 extend into the cavities 136 and 138 and are partly housed therein. The cavities 136 and 138 open at least at the portion 104 to allow the introduction of the shells 105. A first shell 105 is housed between the portions 132 and 122 and another between the portions 124 and 134. The shells 105 are located around the portions 122 and 124. A transverse dimension D105 defined between the shells 105, measured in the chord direction DC, may be substantially constant in the second cavities 136 and 138. Preferably, a surface preparation by chemical means or by dry means such as a laser treatment is also applied to this upper portion of the shells which will be placed inside the blade on the one hand on the outer surface in contact with the portions 132 and 134 and on the other hand on the inner surface in contact with the portions 122 and 124.A film of adhesive is then applied to these surfaces as described above. As illustrated, the elements 140 and 142 bear on the shells 105 and have a bearing surface 140a, 142a matching their shape. Such an extension of the shells into the blade portion 102 constitutes a preferred embodiment and, in a variant not illustrated, the shells cover only the root portion without extending into the blade portion.

[0037] The unlinking D2 has a downstream end D22 from which the portions 120, 132 and 134 are woven together to reform the main portion 130 defining the trailing edge 108. The end D21 is spaced from the leading edge 106 and the end D22 is spaced from the trailing edge 108. In the example considered, the unlinking DI is present inside the unlinking D2 with the ends D21, D11, D12 and D22 succeeding each other in this order when moving from the leading edge 106 to the trailing edge 108. An upstream zone of the portion 120 connects the end D21 to the end D11 and a downstream zone of the portion 120 connects the end D12 to the end D22.

[0038] Figure 4 shows a view of the second threads T1-T4, which are here weft threads, in cross-section to the direction DL. This view corresponds to a view in the shaped rough state, showing in particular excess lengths of non-woven threads. which are intended to be cut to obtain the fiber reinforcement. The second yarns are split into four groups, each denoted from T1 to T4. The first group T1 is woven with first yarns from the leading edge 106 to the trailing edge 108 and extends in particular in the portions 130, 132 and 134. The second group T2 is also woven with first yarns from the leading edge 106 to the trailing edge 108, extending in the portions 130, 120, 122 and 124. The yarns of the second group T2 intersect at the crossing points CT2 which delimit the debonding DI on the upstream side and the downstream side. This interweaving makes it possible to prevent the preform from opening in the direction DE once it has been consolidated. This helps to prevent the debonded areas from extending under mechanical loading.The yarns of the third group T3 intersect at the crossing points CT3, delimiting the unlinking D2 on the upstream side, to split for example into a first subgroup which is woven with the first yarns in the portions 120, 122, 124 and 130 and extends to the trailing edge 108, and into a second subgroup which is taken out of the fabric to adapt the thickness of the woven portions. According to a variant, the yarns of the second subgroup are woven into the portions 132 and 134 rather than being taken out. The choice of one or other of these variants will be made according to the desired thickness for the portions 132 and 134. Generally speaking, the intersecting of the yarns at the points CT3 makes it possible to benefit from the mechanical advantage described above. In the example considered, the wires of the first subgroup of the third group T3 are detached from the wires of the first group T1 so as to form the cavities 136 and 138.Finally, the fourth group T4 is woven with the first yarns on the portion 130 and is then taken out of the fabric to manage the thickness transitions. The fourth group T4 is woven only on the side of the leading edge 106 and is not reintroduced into the reinforcement after the yarns have come out, forming excess lengths which are cut during the shaping of the blank to obtain the fiber reinforcement. In the example illustrated, the portions 130, 120, 122, 124, 132 and 134 are each formed by three-dimensional weaving.

[0039] Figure 5 represents a view along the section plane VV where the main portion 130, which corresponds to the extension of the textile illustrated in figures 3 and 4 along the direction DL, has the separation DI to form the cavity 111. However, there is no longer any separation D2 at this height.

[0040] The following describes details relating to the manufacturing process of the blade 100. First, a fiber blank, in a single piece of fabric, is obtained by three-dimensional weaving by arranging the separations DI and D2, using techniques known per se. The part 112 is then introduced inside the separation D1. The shells 105 are attached to the part 104 and introduced, in the example illustrated, into the separation D2 as previously described. The elements of conformation 140 and 142 in the delinkage D2 which have been previously formed to the desired geometry. In this way, the blank is shaped into the blade 100 to be obtained. The excess lengths are cut and the assembly is then placed in an injection mold in order to introduce a resin into the porosity of the reinforcement, for example by a resin transfer molding technique. A heat treatment can then be carried out to polymerize the resin thus introduced and place, in a manner known per se, the metal protection 110 and a possible de-icing system in order to obtain the blade 100 ready to be mounted on the engine.

Claims

Claims

1. Variable pitch composite material blade (100) for an unducted aircraft fan (204), comprising: - a fibrous reinforcement, formed in a single piece of three-dimensional fabric, comprising a blade portion (102), and a root portion (104) forming a retention bulb and intended to be connected to a variable wedging mechanism (20), the three-dimensional weaving being carried out continuously between the root portion and the blade portion, the fibrous reinforcement defining an internal shaping cavity (111), formed by a delinking (Dl), extending inside the root portion and the blade portion, - a matrix densifying said fibrous reinforcement, and - metal reinforcement shells (105) added around the foot part.

2. Blade (100) according to claim 1, in which the blade portion (102) defines two second internal shaping cavities (136; 138), formed by a second separation (D2), opening onto the root portion (104) and located on either side of the shaping cavity (111), the metal shells (105) being partly housed in the second shaping cavities.

3. Blade (100) according to claim 2, in which a largest transverse dimension (D105) defined between the metal shells (105), measured in the chord direction (DC), is substantially constant in the second shaping cavities (136; 138).

4. Blade (100) according to claim 2 or 3, in which a shaping element (140; 142) made of cellular or porous material, distinct from the metal shells (105), is present in each of the second shaping cavities (136; 138).

5. Blade according to any one of claims 2 to 4, in which the blade portion (102) comprises, over a section of its longitudinal dimension adjacent to the root portion (104), a main woven portion (130) defining a leading edge (106) and a trailing edge (108), said main portion being separated over the second uncoupling (D2) into woven skin portions (132; 134) each delimiting a second shaping cavity, and into an intermediate woven portion (120) located between the skin portions, said intermediate portion being separated on the unlinking (Dl) into two unlinked portions (122; 124) delimiting the shaping cavity.

6. A blade (100) according to any one of claims 1 to 5, wherein the blade further comprises a shaping piece (112) present in the internal shaping cavity (111), said shaping piece being hollow at least on a lower longitudinal end of the blade.

7. A blade (100) according to any one of claims 1 to 6, wherein the root portion (104) comprises a mounting portion (107a), defining the retention bulb, and a stilt portion (107b) which provides the transition between the mounting portion and the blade portion (102), the metal shells (105) extending around the mounting and stilt portions.

8. A blade (100) according to any one of claims 1 to 7, wherein the fibrous reinforcement is formed from carbon fibers, glass fibers, aramid fibers, or a mixture of such fibers.

9. A blade (100) according to any one of claims 1 to 8, wherein the matrix is ​​an epoxy resin.

10. An unducted fan (204) for mounting on an aircraft comprising a hub comprising blade attachment portions, and a plurality of blades (100) according to any one of claims 1 to 9 mounted on the attachment portions.

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