ROTOR BLADE FOR AN AIRCRAFT TURBOMACHINE PROPELLER AND ITS MANUFACTURING METHOD

Abstract

Rotor blade (14) for a propeller (10) of an aircraft turbomachine, this blade (14) comprising a blade (20) connected to a root (40) which is housed in a platform (22), the blade (20) and the root (40) being made of a composite material comprising a fibrous body (50) embedded in a polymer matrix, the root (40) having a generally elongated shape, the platform (22) comprising a housing (38) for receiving said root (40), this housing (38) having a shape complementary to this root (40), the platform (22) being configured to define a setting axis (Y) of the blade (10) which extends along an elongation axis of the blade (20), characterized in that the platform (22) comprises orifices (62) which extend from an external surface (34) of the platform (22) into the housing (38). Figure for abstract: Figure 2

Description

Title of the invention: ROTOR BLADE FOR AN AIRCRAFT TURBOMACHINE PROPELLER AND METHOD FOR MAKING SAME BRICATION Technical field of the invention

[0001] The present invention relates to the field of aircraft turbomachines and in particular to the propulsion propellers of these turbomachines which comprise variable-pitch blades. Technical background

[0002] The state of the art includes in particular documents FR-A1-3 017 163 and FR-Al-3 080 322.

[0003] An aircraft turbomachine propeller may be shrouded, as is the case with a fan for example, or unshrouded as is the case with an open-rotor type architecture for example.

[0004] A propeller comprises blades which can be variable pitch. The turbomachine then comprises a mechanism for modifying the pitch angle of the blades in order to adapt the thrust generated by the propeller according to the different phases of flight.

[0005] The design of a propeller blade involves several disciplines whose objectives are generally antagonistic. It must allow optimal aerodynamic performance (i.e. provide thrust while maximizing efficiency), guarantee mechanical strength of the blade (i.e. withstand the mechanical constraints resulting from static and dynamic loadings) while limiting the mass as well as the acoustic signature. In particular, the improvement of the aerodynamic performance of the propeller tends towards an increase in the BPR (By Pass Ratio), which results in an increase in its external diameter and therefore in the span of the blades.

[0006] In current technology, it is common to fix a blade to its support by a so-called broached fastener. The blade comprises a foot which has a general dovetail shape and which is intended to be engaged by complementary shapes in a housing of a support platform, this housing being conventionally produced by broaching.

[0007] The support platform is housed in an orifice of a hub of the propeller and defines the pitch axis of the blade. The platform is therefore movable in rotation around the pitch axis inside this orifice of the hub.

[0008] For a blade with a pinned attachment, the aerodynamic force is so intense that it can cause rigid solid movements of the blade root in its housing which are similar to swiveling. Indeed, during a feather start, the reduced speed of the fan does not generate sufficient centrifugal force to prevent these movements induced by the aerodynamic force. This results in frictional damage to the blade and the shim inserted between the root and the bottom of its housing, in just a few cycles. This shim is intended to take up the assembly clearances in the broaching between the blade and its mounting housing, and must also perfectly position the blade perpendicular to the propeller's rotation axis. For the same reasons, this problem may arise in a freewheeling situation (or "windmilling") following an engine failure because variable pitch blades are generally equipped with a feathering system.

[0009] In addition, intense vibration excitation can also occur at much higher 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 subject to the influence of the ground and the fuselage, which causes a distortion in the supply of the propeller, in flow speed, according to the engine azimuths. This results in a vibration response of the propeller blades on the first engine orders IN, 2N and 3N (possibly more). On the other hand, in the absence of an air intake sleeve, the direction of the air flowing through the blades is not parallel to the engine axis. This sideslip angle results in so-called "IP" forces which cause a vibration response of the propeller blades on the engine order IN.Similarly, these IP forces can also occur during the aircraft's climb or approach phases because the air flows through the blades at an angle of incidence. These high rotational speed vibration excitations can cause the same friction damage discussed above if the blade attachment is not suitable.

[0010] For all of these reasons, there is a need to improve the existing technology for fixing and securing the blade root to its support platform. Summary of the invention

[0011] The invention relates to a rotor blade for an aircraft turbomachine propeller, this blade comprising a blade connected to a root which is housed in a platform,

[0012] the blade and the root being made of a composite material comprising a fibrous body embedded in a polymer matrix, the blade comprising a lower surface and an upper surface connected together at a leading edge and a trailing edge of the blade, the root having a generally elongated shape,

[0013] the platform comprising a housing for receiving said root, this housing having a shape complementary to this root, the platform being configured to define a blade setting axis which extends along an axis of elongation of the blade,

[0014] characterized in that the platform comprises orifices which extend from a external surface of the platform into the housing.

[0015] The platform of the blade is advantageously used to mold the root. During molding, air bubbles may be generated and / or trapped in the housing, between the root and the walls of the housing. The orifices of the platform allow these air bubbles to escape from the housing and therefore make it possible to limit or even eliminate the risk of such bubbles being present in the housing. It is therefore understood that the root of the blade can take up all the space available in the housing of the platform. There is therefore advantageously no play between the root and the walls of the housing because the polymer matrix at the root will occupy all the space in the housing. Furthermore, the polymer matrix will harden upon contact with the walls of the housing and thus makes it possible to further secure the blade to the platform and therefore to participate in the retention of the blade by the platform.

[0016] The blade according to the invention may comprise one or more of the following characteristics, taken in isolation from one another, or in combination with one another:

[0017] — the foot has a dovetail shape in section;

[0018] — the housing has a dovetail shape in section;

[0019] — the foot and the housing cooperate with each other by broached attachment and complementarity of shapes;

[0020] - the orifices are at least partly filled by the polymer matrix;

[0021] - the orifices are completely filled by the polymer matrix;

[0022] - the orifices are partly filled by the polymer matrix, the rest of the orifices being filled with plugs; • the platform comprises at least one aerodynamic surface capable of being swept by an air flow when the propeller is operating, said orifices opening onto said at least one aerodynamic surface; • the platform comprises a first aerodynamic surface located on the side of said intrados, and a second aerodynamic surface located on the side of said extrados, said orifices opening onto these aerodynamic surfaces;

[0023] — said first and second aerodynamic surfaces being capable of being swept by an air flow when the propeller is operating;

[0024] the foot is housed without any play in said housing and is secured to the platform thanks to said polymer matrix; • said housing has an elongated shape and opens at its two longitudinal ends, the longitudinal ends of the foot being aligned with the longitudinal ends of the housing;

[0025] — said foot occupying the entire volume of this housing, • the longitudinal ends of the housing open onto a cylindrical surface lindic of the platform which extends around said wedging axis, the longitudinal ends of the foot comprising portions of cylindrical surface which extend in the extension of the cylindrical surface of the platform and which complete this cylindrical surface at the level of the outlets of the housing;

[0026] — the dawn further comprises two locks fixed on the platform, on either side of the foot, and configured to cover the longitudinal ends of the foot respectively; the locks thus make it possible to block the foot in its housing;

[0027] — a first of the locks comprises a first aerodynamic surface located on the side of said leading edge, and a second of said locks comprises a second aerodynamic surface located on the side of said trailing edge, said first and second aerodynamic surfaces of the first and second locks being capable of being swept by an air flow when the propeller is operating; the locks thus make it possible to reconstitute part of the aerodynamic vein of the propeller, • the platform comprises a cylindrical body which extends under the foot along said wedging axis; • the platform comprises a disc centered on the wedging axis and comprising the foot receiving housing, the orifices being formed in this disc; • the number of holes in the platform is between two and ten, and preferably between two and four.

[0028] The present invention also relates to a propeller for an aircraft turbomachine, comprising an annular hub which extends around an axis of rotation and which comprises a series of orifices which are regularly distributed around the axis of rotation and which are oriented radially relative to the axis of rotation, and blades as described above, the platforms of which are mounted respectively in these orifices so that the blades extend radially outwards from the hub, each of the platforms being able to rotate around its pitch axis inside the orifice of the hub.

[0029] The present invention also relates to a turbomachine, in particular for an aircraft, comprising a propeller as described above.

[0030] The invention further provides a method of manufacturing a blade as described above, comprising the following steps:

[0031] a) preparation of the fibrous body of the blade,

[0032] b) insertion of the foot into the platform housing,

[0033] c) injection of a resin into the housing of the platform so as to give it the function of an injection mold, or molding of the foot previously impregnated with resin in the housing of the platform, the resin being intended to form said polymer matrix, and to circulate in said orifices in order to expel the air contained in the housing and preferably to remove any play between the foot and the housing, and to secure the foot to the platform.

[0034] It is therefore understood that the resin is injected into the platform forming the injection-molding mold, which is advantageous because it is not necessary to provide a foot demolding operation in this case.

[0035] The method according to the invention may comprise one or more of the following characteristics, taken in isolation from one another, or in combination with one another:

[0036] — the resin injected or which impregnates the foot or the fibrous body is liquid or pasty; • between steps b) and c) or in step c), molding shells are placed on the platform; • the shells compress the foot and / or the resin in the platform housing, the foot preferably having a volume greater than that of the housing; the molding shells are thus shells for compressing the foot and / or the resin in the platform housing; compressing the foot is advantageous for ensuring play-free molding of the foot and stressing the foot in the platform housing after polymerization; • before step b) or c), or after step c), plugs are inserted into the holes in the platform;

[0037] — the foot has a length or longitudinal extent greater than that of the housing and includes longitudinal portions projecting at the end of step b);

[0038] — after step c), the process comprises a step d) of cooking with a view to polymerizing resinization; the difference in thermal expansion intrinsic to each material allows, during cooling, the platform to exert a constant and homogeneous pressure force on the blade root; the clearances are not only consumed, but a retention force between the parts is naturally applied;

[0039] — after step c) or d), the method comprises a cooling step e) controlled and homogeneous resin to control thermal expansion forces between the platform and the foot; • for example after step c), d) or e), the method comprises a step f) of removing, for example by machining, said longitudinal portions; • the method further comprises a following step g) of fixing two locks on the platform, on either side of the foot, these locks respectively covering the longitudinal ends of the foot. Brief description of the figures

[0040] Other characteristics and advantages will emerge from the following description of a non-limiting embodiment of the invention with reference to the appended drawings in which:

[0041] [Fig-1] [Fig.l] is a schematic perspective view of a propeller for a tur- aircraft engine,

[0042] [Fig.2] [Fig.2] is a schematic perspective view of a rotor blade for a propeller such as that of [Fig.l],

[0043] [Fig.3] [Fig.3] is another schematic perspective view of the rotor blade of [Fig.2],

[0044] [Fig.4] [Fig.4] is a schematic perspective view of a blade of the dawn of the [Fig.l], and illustrates a step in a blade manufacturing process,

[0045] [Fig.5] [Fig.5] is another schematic perspective view of another stage of the method, in particular of mounting the blade of [Fig.4] in a platform,

[0046] [Fig.6] [Fig.6] is a schematic perspective view of the blade and the platform assembled after the step in [Fig.5],

[0047] [Fig.7] [Fig.7] is a partial schematic sectional view of the blade and the assembled platform of [Fig.6],

[0048] [Fig.8] [Fig.8] is a schematic perspective view of the assembled blade and platform of [Fig.6] with additional schematic representation of molding and compression shells, and illustrates another step in the manufacturing process,

[0049] [Fig.9] [Fig.9] is a view similar to that of [Fig.6] and illustrates a step of elimination of the manufacturing process,

[0050] [Fig. 10] [Fig. 10] is a view similar to that of [Fig.6] and illustrates the end of the removal step of the manufacturing process,

[0051] [Fig. 11] [Fig. 11] is a partial schematic perspective view of the rotor blade platform and latches, and illustrates another step in the manufacturing process,

[0052] [Fig. 12] [Fig. 12] is a partial schematic perspective view of a propeller and the blade platform housed in an orifice of a hub of this propeller,

[0053] [Fig. 13] [Fig. 13] is a view similar to that of [Fig.7] and shows the presence of air bubbles between the foot and the walls of the platform housing,

[0054] [Fig. 14] [Fig. 14] is a partial schematic perspective view of a rotor blade according to the invention,

[0055] [Fig. 15] [Fig. 15] is a partial schematic sectional view of the blade of the [Fig. 14], during a manufacturing process,

[0056] [Fig. 16] [Fig. 16] is a partial schematic sectional view of the blade of the [Fig. 14], at the end of the manufacturing process,

[0057] [Fig. 17] [Fig. 17] is a partial schematic perspective view of a blade of rotor according to an alternative embodiment of the invention,

[0058] [Fig. 18] [Fig. 18] is a partial schematic sectional view of the blade of [Fig.17], and

[0059] [Fig. 19] [Fig. 19] is a schematic perspective view of the blade and the root of a blade (without its platform) obtained by a method according to the invention. Detailed description of the invention

[0060] [Fig.l] shows a propeller 10 for an aircraft turbomachine, this propeller 10 being able to be shrouded or unshrouded, that is to say surrounded or not by an annular casing of the turbomachine.

[0061] The propeller 10 is rotatable about an axis X and comprises a hub 12 and blades 14 carried by the hub 12. The hub 12 has an annular shape about the axis X and comprises a series of orifices 16 regularly distributed about the axis X. These orifices 16 have substantially radial orientations relative to the axis X and generally open in a radial direction inside the hub 12, and outside the hub 12. The orifices 16 open for example onto an external annular surface 12a of the hub 12, which may be cylindrical or frustoconical.

[0062] Each of the blades 14 comprises a blade 20 and a platform 22 secured to a root of the blade 20. Conventionally, the blade 20 comprises a lower surface face 21, an upper surface face 24, a leading edge 26, and a trailing edge 28. The blade 20 comprises a free end opposite its root, called the apex 29. The root and the platform 22 are located at the end opposite the apex 29.

[0063] The orifices 16 are intended to receive the platforms 22 of the blades 14 which make it possible to guide the blades 14 in rotation around radial axes Y and to wedge them angularly around these radial axes Y, called wedge axes.

[0064] Figures 2 and 3 show a rotor blade 14 which can equip a propeller 10 such as that illustrated in [Fig.l].

[0065] The platform 22 has a particular shape in the example shown. It essentially comprises two parts, namely a cylindrical body 30 and a disc 32. The cylindrical body 30 forms a pivot for setting the blade 14. The disc 32 can have a function of holding the blade and ensuring an aerodynamic junction between the vein and the body / pivot.

[0066] The body 30 is centered on the setting axis Y and has a generally elongated shape along this axis Y. The upper or radially external end of the body 30, relative to the axis X, is connected to the disk 32 and located on the side of the blade 20. The lower or radially internal end of the body 30, relative to the axis X, is intended to be connected to a mechanism for actuating the setting of the blade 14 which is generally located inside the hub 12 of the propeller 10 and which is not shown in the drawings.

[0067] The platform 22, and in particular the disc 32, comprises an aerodynamic surface 34 intended to be aligned with the surface 12a of the hub 12 and therefore to be swept by a flow of gas in operation.

[0068] In the example shown, the disc 32 comprises a first aerodynamic surface 34a located on the side of the intrados face 21, and a second aerodynamic surface 34b located on the side of the extrados face 24.

[0069] The platform 22, and in particular the body 30, comprises a cylindrical surface 36 which extends around the Y axis.

[0070] The platform 22 comprises a housing 38 for receiving the root 40 of the blade 20. In the example shown, the housing 38 is of the broached type and the root 40 of the blade 20 has a generally elongated shape, preferably with a dovetail section.

[0071] Alternatively, other types of pinned attachment are conceivable. Instead of a dovetail section, the foot 40 and the housing 38 could have another sectional shape and for example a fir tree, C, Z shape, etc.

[0072] The housing 38 has an elongated shape along an elongation axis Z substantially perpendicular to the setting axis Y and opens at its two longitudinal ends at the surface 36 in the example shown. There are therefore two outlets of the housing 38, on the surface 36, diametrically opposite relative to the axis Y.

[0073] The foot 40 of the blade 20 also has an elongated shape along the aforementioned elongation axis Z, and has a shape complementary to that of the housing 38

[0074] It can be seen in Figures 2 and 3 that the longitudinal ends of the foot 40 have convex curved shapes which extend at the level of the aforementioned outlets and which reproduce the missing portions of the surface 36 by extending in the extension thereof.

[0075] The blade 20 and the foot 40 are made of a composite material comprising a fibrous body embedded in a polymer matrix. The fibrous body is made by three-dimensional weaving of fibers, for example carbon, or by draping of folds or fabrics (woven or non-woven) which are superimposed on each other.

[0076] The polymer matrix is ​​generally obtained by polymerization of a resin, which can be thermosetting and which is for example an epoxy resin.

[0077] The foot 40 of the blade 20 is advantageously housed without any play in the housing 38 of the platform 22 and is secured to the platform 22 by means of the polymer matrix.

[0078] For this, the invention proposes a method of manufacturing the blade 12 which will be described below with reference to Figures 4 and following. Figures 4 and following illustrate several steps of this method.

[0079] [Fig.4] illustrates a first step a) of the method in which the fibrous body 50 of the blade 20 and the root 40 of the vane 14 is prepared. As mentioned in the above, the fibrous body can be prepared by three-dimensional weaving of fibers or draping of folds. This gives a three-dimensional shape comprising a (part of) blade and a (part of) foot, the blade and the foot being integral. The foot 40 of the fibrous body 50 has a generally elongated and preferably dovetailed shape, with a length along its elongation axis Z which is denoted Ll.

[0080] [Fig.5] illustrates another step b) of the method in which the foot 40 is inserted into the housing 38 of the platform 22. As mentioned above, the housing 38 is obtained by broaching and the foot 40 is intended to be inserted into the housing 38 by translation along the elongation axis Z. The foot 40 is thus intended to slide or slide into the housing 38. It can be seen in [Fig.6], after mounting the foot 40 in the housing 38 of the platform 22, that the length L1 of the foot 40 is greater than the length L2 of the housing 38. [Fig.7] shows that the foot 40 has a complementary shape with the housing 38 of the platform 22, mounting clearances being able to exist between them after step b).

[0081] [Fig.8] illustrates another step c) of the method in which a resin is injected into the housing 38 of the platform 22 so as to give it an injection mold function. Alternatively, the fibrous body or only the foot could be impregnated or pre-impregnated with a resin. Step c) would then consist of molding the foot previously impregnated with resin in the housing of the platform.

[0082] The resin is intended to form the aforementioned polymer matrix, to eliminate any play between the foot 40 and the housing 38, and to secure the foot 40 to the platform 22.

[0083] In practice, the platform 22 may constitute a part of the injection mold and additional elements, such as molding shells 52, may be added to the platform 22 in order to constitute the molding cavity all around the platform 22.

[0084] [Fig. 8] very schematically represents two molding shells 52 which are arranged on two diametrically opposite sides of the platform 22, with respect to the Y axis. In particular, these two shells 52 can make it possible to cover the portions of the foot 40 which protrude from the housing 38.

[0085] The molding shells 52 may have the function of compressing these portions of the foot 40 radially inwards, with respect to the setting axis Y (see arrows F). The molding shells 52 are then shells for compressing the foot and / or the resin. This solution has the advantage of filling the assembly clearances to create a fitting connection.

[0086] To facilitate or allow compression of the foot into the platform housing, the foot may initially have a volume greater than that of the platform housing.

[0087] During compression (and preferably also during polymerization resin), the blade 20 and the platform 22 are perfectly positioned to guarantee the repeatability of each blade 14 of the propeller 10.

[0088] [Fig. 8] thus also represents an optional step of the process in which, between steps b) and c) or after step c), molding shells 52 are attached to the platform 22.

[0089] After step c), the method may include a step d) of curing for the polymerization of the resin. The difference in thermal expansion intrinsic to each material allows, during cooling, the platform to exert a constant and homogeneous pressure force on the blade root. The clearances are not only consumed, but a retention force between the parts is naturally applied.

[0090] After step c) or d), the method comprises a cooling step e). During cooling of the blade, the material (generally metallic) of the platform 22 generally has a coefficient of expansion greater than the composite material of the blade, which allows the cold clearance to become negative between the parts. The cooling of the resin is preferably controlled and homogeneous to control the thermal expansion forces between the platform and the root.

[0091] The method may further comprise an optional step f) illustrated in [Fig.9], in which the projecting longitudinal portions of the foot 40 are removed, for example by machining.

[0092] At the end of step f) or directly after step c), a blade is obtained as illustrated in [Fig. 10] in which the longitudinal ends of the root 40 comprise cylindrical surface portions which extend in the extension of the cylindrical surface 36 of the platform 22 and complete this cylindrical surface 36 at the level of the outlets of the housing 36.

[0093] The method may further comprise a following step g) of fixing two locks 54 on the platform 22, on either side of the foot 40 ([Fig. 11]). The locks 54 may be fixed by elements of the screw-nut type or the like.

[0094] These locks 54 are intended to cover respectively the longitudinal ends of the foot 40.

[0095] A first of the locks 54 comprises a first aerodynamic surface 54a located on the side of the leading edge 26, and a second of the locks 54 comprises a second aerodynamic surface 54b located on the side of the trailing edge 28.

[0096] These aerodynamic surfaces 54a, 54b are aligned on the one hand with the surface 34 of the platform 22, and are further intended to be aligned with the surface 12a of the hub (cf. [Fig. 12]).

[0097] [Fig. 13] shows a situation to be avoided in which air bubbles 60 are likely to be generated and / or trapped in the housing 38, between the foot 40 and the walls of the housing 38, in particular at the end of the manufacturing process.

[0098] These air bubbles 60 may for example result from the exothermic reaction of polymerization or cooking of the resin.

[0099] These air bubbles are likely to alter the cohesion between the foot 40 and the platform 22 and to create areas of weakness around the foot 40 of the blade.

[0100] It is therefore important to limit or even eliminate the presence of these air bubbles 60.

[0101] The present invention provides a solution to this subject: a rotor blade such that described in the above, the platform 22 of which has orifices 62 which extend from an external surface 34a of the platform into the housing 38.

[0102] The rotor blade thus includes all the characteristics of the blade described above with reference to Figures 2 to 12 to the extent that they do not contradict what follows.

[0103] Figures 14 and following illustrate several alternative embodiments of the invention. The orifices 62 can be at least partly filled by the polymer matrix. In the case of [Fig. 16] for example, the orifices 62 are entirely filled by the polymer matrix. In the case of [Fig. 18], the orifices 62 are partly filled by the polymer matrix, the remainder of the orifices 62 being filled by plugs 64.

[0104] Furthermore, as can be seen in the drawings, the orifices 60 preferably open onto the aerodynamic surface(s) 34, 34a, 34b of the platform 22.

[0105] The number of orifices 62 of the platform 22 is for example between two and ten, and preferably between two and four.

[0106] The blade according to the invention can be produced by the method described above, the resin injected or impregnated in step c) being able to circulate in the orifices 62 in order to expel the air contained in the housing 38.

[0107] In the context of the method described above, this means for example that, in step c), the injected or impregnated resin is able to circulate in the orifices 62 in order to expel the air contained in the housing 38. [Fig. 15] shows the situation before injection or compression, and [Fig. 16] shows the situation after injection or curing.

[0108] The aforementioned compression of the foot 40 in the housing 38 makes it easier to evacuate the air bubbles 60 which are forced to move and exit through the orifices 62.

[0109] The orifices 62 can be left free during the process so that resin exits through these orifices 62 during molding. It would then be sufficient to remove the excess resin and level its surface so that one end of the resin located at the level of the aerodynamic surface 34 is aligned with this surface.

[0110] Alternatively, as illustrated in figures 17 and 18, before step b) or c), plugs 64 can be engaged in the orifices 62 of the platform 22. It is therefore understood that the air bubbles 60 will be expelled into these orifices 62 and stopped by the plugs. 64 and that only part of the orifices 62 will be filled by the resin after molding. Alternatively, the plugs 64 could be engaged in the orifices 62 after step c) and therefore after evacuation of the air bubbles 60. The resin would partially fill the orifices 62 which would be finished filling by the plugs 64 which could be leveled as mentioned above.

[0111] [Fig. 19] shows the blade without its platform and allows the small pins 66 projecting from the foot 40 of the blade to be viewed, which result from the engagement and hardening of the resin in the orifices 62 of the platform22.

[0112] These pins 66 further increase the mechanical strength of the foot with respect to the platform 22.

Claims

Claims

1. Rotor blade (14) for a propeller (10) of an aircraft turbomachine, this blade (14) comprising a blade (20) connected to a root (40) which is housed in a platform (22), the blade (20) and the root (40) being made of a composite material comprising a fibrous body (50) embedded in a polymer matrix, the blade (20) comprising a lower surface (21) and an upper surface (24) connected together at a leading edge (26) and a trailing edge (28) of the blade (20), the root (40) having a generally elongated shape, the platform (22) comprising a housing (38) for receiving said root (40), this housing (38) having a shape complementary to this root (40), the platform (22) being configured to define an axis (Y) for setting the blade (14) which extends along a elongation axis of the blade (20), characterized in that the platform (22) comprises orifices (62) which extend from an external surface (34) of the platform (22) into the housing (38).

2. A blade (14) according to claim 1, wherein the orifices (62) are at least partially filled by the polymer matrix.

3. A blade (14) according to claim 2, wherein the orifices (62) are entirely filled by the polymer matrix.

4. A blade (14) according to claim 2, wherein the orifices (62) are partly filled by the polymer matrix, the remainder of the orifices (62) being filled by plugs (64).

5. Blade (14) according to one of the preceding claims, in which the platform (22) comprises at least one aerodynamic surface (34, 34a, 34b) capable of being swept by an air flow when the propeller (10) is operating, said orifices (62) opening onto said at least one aerodynamic surface (34, 34a, 34b).

6. Blade (14) according to the preceding claim, in which the platform (22) comprises a first aerodynamic surface (34a) located on the side of said intrados (21), and a second aerodynamic surface (34b) located on the side of said extrados (24), said orifices (62) opening onto these aerodynamic surfaces (34a, 34b).

7. Blade (14) according to one of the preceding claims, in which the foot (40) is housed without any play in said housing (38) and is secured to the platform (22) by means of said polymer matrix.

8. A blade (14) according to any preceding claim, wherein said housing (38) has an elongated shape and opens at its two longitudinal ends, the longitudinal ends of the foot (40) being aligned with the longitudinal ends of the housing (38).

9. Blade (14) according to the preceding claim, in which the longitudinal ends of the housing (38) open onto a cylindrical surface (36) of the platform (22) which extends around said setting axis (Y), the longitudinal ends of the foot (40) comprising portions of cylindrical surface which extend in the extension of the cylindrical surface (36) of the platform (22) and which complete this cylindrical surface (36) at the level of the outlets of the housing (38).

10. Blade (14) according to one of the preceding claims, in which the platform (22) comprises a cylindrical body (30) which extends under the foot (40) along said setting axis (Y).

11. Blade (14) according to one of the preceding claims, in which the platform (22) comprises a disc (32) centered on the setting axis (Y) and comprising the housing (38) for receiving the foot (40), the orifices (62) being formed in this disc (32).

12. Blade (14) according to one of the preceding claims, in which the number of orifices (62) of the platform (22) is between two and ten, and preferably between two and four.

13. Propeller (10) for an aircraft turbomachine, comprising an annular hub (12) which extends around an axis of rotation (X) and which comprises a series of orifices (16) which are regularly distributed around the axis of rotation (X) and which are oriented radially relative to the axis of rotation (X), and blades (14) according to one of the preceding claims, the platforms (22) of which are mounted respectively in these orifices (16) so that the blades (20) extend radially outwards from the hub (12), each of the platforms (22) being able to rotate around its pitch axis (Y) inside the orifice (16) of the hub (12).

14. Aircraft turbomachine, comprising a propeller (10) according to the preceding claim.

15. A method of manufacturing a blade (14) according to one of claims 1 to 12, comprising the following steps: a) preparation of the fibrous body (50) of the blade (14), b) insertion of the foot (40) into the housing (38) of the platform (22), c) injection of a resin into the housing (38) of the platform (22) so as to give it an injection mold function, or molding of the foot previously impregnated with resin in the platform housing, the resin being intended to form said polymer matrix, and to circulate in said orifices (62) in order to expel the air contained in the housing (38).

16. Method according to the preceding claim, in which, between steps b) and c), or after step c), molding shells (52) are attached to the platform (22).

17. Method according to the preceding claim, in which the molding shells (52) compress the foot (40) and / or the resin in the housing (38) of the platform (22), the foot (40) preferably having a volume greater than that of the housing (38).

18. Method according to one of claims 15 to 17, in which, before step b) or c), or after step c), plugs (64) are engaged in the orifices (62) of the platform (22).

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