ROTOR BLADE FOR AN AIRCRAFT TURBOMACHINE PROPELLER AND ITS MANUFACTURING PROCESS

Abstract

Rotor blade (14) for an aircraft turbomachine propeller (10), this blade (14) comprising a blade (20) connected to a foot (40) which is housed in a platform (22), the blade (20) and the foot (40) being made of a composite material comprising a fibrous body (50) embedded in a polymer matrix, the foot (40) having a generally elongated shape, the platform (22) comprising a housing (38) for receiving said foot (40), this housing (38) having a shape complementary to this foot (40), the platform (22) being configured to define a blade (10) alignment axis (Y) which extends along an axis of elongation of the blade (20), characterized in that the housing (38) comprises teeth (60) for engaging the foot (40). Figure for the abbreviation: Figure 2

Description

Title of the invention: ROTOR BLADE FOR AN AIRCRAFT TURBOMACHINE PROPELLER AND ITS METHOD OF MAKING IT DIY Technical field of the invention

[0001] The present invention relates to the field of aircraft turbomachinery and in particular to the propulsion propellers of these turbomachinery which have 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 can be shrouded, as is the case of a fan for example, or unshrouded as is the case of an open-rotor type architecture for example.

[0004] A propeller comprises blades which may have 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 conflicting. It must allow for optimal aerodynamic performance (i.e., provide thrust while maximizing efficiency), guarantee the blade's mechanical strength (i.e., withstand the mechanical stresses resulting from static and dynamic loads), while limiting mass and acoustic signature. In particular, improving the propeller's aerodynamic performance tends towards an increase in the BPR (By-Pass Ratio), which translates into an increase in its external diameter and therefore the blade span.

[0006] In current technology, it is common to attach a blade to its support by means of a so-called pinned attachment. The blade comprises a foot which has a generally dovetail shape and which is designed to be engaged by complementary shapes in a recess of a support platform, this recess being conventionally made by pinning.

[0007] The support platform is housed in an opening in a propeller hub and defines the blade's alignment axis. The platform is therefore free to rotate around the alignment axis within this hub opening.

[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 that resemble ball jointing. Indeed, during a feathering start, the reduced speed The fan's design does not generate sufficient centrifugal force to prevent these movements induced by aerodynamic stress. This results in friction damage to the blade and the shim between the blade root and the bottom of its housing, within just a few cycles. This shim is designed to eliminate any play in the mounting pins between the blade and its housing, and must also perfectly position the blade perpendicular to the propeller's axis of rotation. For the same reasons, this problem can arise in a freewheeling (or "windmilling") situation following an engine failure, as variable-pitch blades are generally equipped with a feathering return system.

[0009] Furthermore, intense vibrational excitation can also occur at much higher rotational speeds on unfaired designs due to the effects of engine installation on the aircraft and the direction of the upstream continuous flow. Indeed, an unfaired engine is influenced by the ground and the fuselage, which causes a distortion in the propeller's airflow velocity, depending on the engine azimuth. This results in a vibrational response of the propeller blades on the first engine commands IN, 2N, and 3N (possibly higher). Moreover, in the absence of an air intake duct, the direction of the air flowing through the blades is not parallel to the engine axis. This sideslip angle induces so-called "IP" forces, which cause a vibrational response of the propeller blades on the engine command IN.Similarly, these IP stresses can also occur during the aircraft's climb or approach phases because air flows through the blades at an angle of attack. These high-speed vibrational excitations can cause the same friction damage mentioned above if the blade attachment is not properly adapted.

[0010] For all these reasons, there is a need to improve the existing technology for fixing and securing the blade foot 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 foot which is housed in a platform,

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

[0013] the platform being configured to define a blade alignment axis extending along a blade extension axis, the platform comprising a housing for receiving said foot, this housing having a shape complementary to this foot and comprising a base connected to two lateral bearing surfaces, the lateral bearing surfaces being adapted to

[0014]

[0015]

[0016]

[0017]

[0018]

[0019] retain the foot along the axis, characterized in that the lateral bearing surfaces of the housing include foot-gripping teeth. The gripping teeth improve the mechanical stability of the foot on the platform. The contact surfaces between the lateral bearing surfaces of the platform housing and the foot are increased, ensuring reliable support and optimal force transmission during operation. The blade according to the invention may comprise one or more of the following features, taken individually or in combination with each other: — the foot has a dovetail shape in cross-section; — the housing has a dovetail shape in section; — the foot and the housing cooperate with each other by means of a broached attachment and complementary shapes; - the hooking teeth are anchored in the foot; - at least some of the teeth on each of the rows have different shapes different from the other teeth in this litter; - the teeth are separated from each other by interdental cavities, at least some of the interdental cavities on each of the spans having different shapes from the other interdental cavities of that span; - the inter-tooth cavities have in section a shape chosen from among a concave curved shape, a dovetail shape, a shape in which at least one lateral face is inclined towards a leading edge or a trailing edge of the blade, and a random shape made by machining; - The foot is housed without any play in the said housing and is secured to the platform by the said polymer matrix; this is made possible by the fact that the blade platform is used to mold the foot. It is therefore understood that the blade foot will occupy all the available space in the platform housing. There is therefore no play between the foot and the walls of the housing because the polymer matrix at the foot will occupy all the space in the housing. Furthermore, the polymer matrix will harden upon contact with the walls of the housing and thus further secure the blade to the platform and therefore contribute to retaining the blade by the platform; - the inter-dental cavities are completely filled by the polymer matrix; - the teeth have a minimum height or minimum protrusion dimension between 0.05 and 2 mm; - the foot is permanently mounted in the housing of the platform ; - the teeth are distributed over an entire length or longitudinal dimension of the housing; - the teeth extend over a dimension along the axis which represents at least 20% of a maximum dimension of the housing along this axis, and preferably at least 40% of this maximum dimension;

[0020] — the platform includes a first aerodynamic surface located on the side of said intrados, and a second aerodynamic surface located on the side of said extrados, said first and second aerodynamic surfaces being capable of being swept by an airflow when the propeller is operating;

[0021] — said housing has an elongated shape and opens at its two longitudinal ends tudinales, the longitudinal ends of the foot being aligned with the longitudinal ends of the housing;

[0022] — said foot occupies the entire volume of this dwelling, • the longitudinal ends of the housing open onto a cylindrical surface of the platform which extends around said alignment axis, the longitudinal ends of the foot comprising portions of cylindrical surface which extend in the continuation of the cylindrical surface of the platform and which complete this cylindrical surface at the level of the openings of the housing;

[0023] — the dawn further comprises two latches fixed to the platform, on either side of the foot, and configured to respectively cover the longitudinal ends of the foot; the locks thus allow the foot to be locked in its housing;

[0024] — a first of the locks comprises a first aerodynamic surface located on the on the leading edge side, and a second of said locks comprises a second aerodynamic surface located on the trailing edge side, said first and second aerodynamic surfaces of the first and second locks being capable of being swept by an airflow when the propeller is running; the locks thus make it possible to reconstitute part of the aerodynamic duct of the propeller,

[0025] — the platform includes a cylindrical body which extends under the foot along said alignment axis;

[0026] — the platform includes a disk centered on the alignment axis and comprising the foot reception accommodation.

[0027] The present invention also relates to a propeller for an aircraft turbomachine, comprising an annular hub extending around an axis of rotation and having a series of orifices regularly distributed around the axis of rotation and oriented radially with respect 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 mounting axis inside the orifice of the hub.

[0028] The present invention also relates to a turbomachine, in particular for aircraft, comprising a propeller as described above.

[0029] The invention further proposes a method for manufacturing a blade as described above, comprising the following steps:

[0030] a) preparation of the fibrous body of the dawn,

[0031] b) insertion of the foot into the platform housing,

[0032] c) injection of a resin into the platform housing so as to give it the function of an injection mold, or molding of the foot previously impregnated with resin into the platform housing, the resin being intended to form said polymeric matrix, to eliminate any play between the foot and the housing, and to secure the foot to the platform.

[0033] 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 for a demolding operation of the foot in this case.

[0034] The method according to the invention may comprise one or more of the following features, taken individually or in combination with each other:

[0035] — the resin injected or which impregnates the foot or fibrous body is liquid or pasty;

[0036] — between steps b) and c) or in step c), molding shells are attached to the platform;

[0037] — 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 compression shells of the foot and / or the resin in the housing of the platform; the compression of the foot is advantageous to guarantee the molding without play of the foot and the stressing of the foot in the housing of the platform after polymerization;

[0038] — 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);

[0039] — after step c), the process includes a step d) of cooking for polymerization resin preparation; 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 gaps are not only consumed, but a retention force between the parts is naturally applied;

[0040] — after step c) or d), the process includes a cooling step e) controlled and homogeneous resin to control thermal expansion forces between the platform and the foot;

[0041] — for example after step c), d) or e), the process includes a step f) of sup pressure, for example by machining, of said longitudinal portions;

[0042] — the method further comprises a subsequent 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

[0043] Other features and advantages will become apparent from the following description of a non-limiting embodiment of the invention with reference to the accompanying drawings in which:

[0044] [Fig-1] [Fig.1] is a schematic perspective view of a helix for a tur- aircraft engine,

[0045] [Fig.2] [Fig.2] is a schematic perspective view of a rotor blade for a propeller such as that of [Fig.1],

[0046] [Fig.3] [Fig.3] is another schematic perspective view of the rotor blade of [Fig.2],

[0047] [Fig.4] [Fig.4] is a schematic perspective view of a blade of the turbine's turbine. [Fig. 1], and illustrates a step in a blade manufacturing process,

[0048] [Fig. 5] [Fig. 5] is another schematic perspective view of another stage of the method, in particular of mounting the blade of the [Fig.4] in a platform,

[0049] [Fig.6] [Fig.6] is a schematic perspective view of the blade and the platform assembled after the step of [Fig.5],

[0050] [Fig.7] [Fig.7] is a schematic cross-sectional view of the blade and platform assemblies of the [Fig.6],

[0051] [Fig.8] [Fig.8] is a schematic perspective view of the blade and the assembled platform of [Fig.6] with an additional schematic representation of molding and compression shells, and illustrates another step in the manufacturing process,

[0052] [Fig.9] [Fig.9] is a view similar to that of [Fig.6] and illustrates a step of elimination of the manufacturing process

[0053] [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,

[0054] [Fig. 11] [Fig. 11] is a partial schematic perspective view of the rotor blade platform and locks, and illustrates another step in the manufacturing process,

[0055] [Fig. 12] [Fig. 12] is a partial schematic perspective view of a propeller and the blade platform housed in an opening of a hub of this propeller,

[0056] [Fig. 13] [Fig. 13] is a schematic perspective view of a platform for a blade according to the invention;

[0057] [Fig. 14] [Fig. 14] is another schematic perspective view of a platform for a blade according to the invention;

[0058] [Fig. 15] [Fig. 15] is a very schematic cross-sectional view of the housing of a platform; and

[0059] [Fig. 16a-16b] Figures 16a and 16b are very schematic cross-sectional views of a Lateral span of a platform housing, according to two embodiment variants. Detailed description of the invention

[0060] Fig. 1 shows a propeller 10 for an aircraft turbomachine, this propeller 10 being able to be shrouded or unshrouded, i.e. surrounded or not by an annular housing of the turbomachine.

[0061] The propeller 10 is free to rotate 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 around the axis X. These orifices 16 have substantially radial orientations with respect to the axis X and generally open radially into the inside of the hub 12, and out of 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 attached to a foot of the blade 20. Conventionally, the blade 20 comprises an intrados face 21, an extrados face 24, a leading edge 26, and a trailing edge 28. The blade 20 comprises a free end opposite its foot, called the apex 29. The foot 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 allow the blades 14 to be guided in rotation around radial axes Y and to be angularly calibrated around these radial axes Y, called calibration axes.

[0064] Figures 2 and 3 show a rotor blade 14, which can equip a propeller 10 such as that illustrated in [Fig.1].

[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 the blade 14. The disc 32 can have a function of holding the blade and ensuring an aerodynamic connection between the duct and the body / pivot.

[0066] The body 30 is centered on the Y-axis and has a generally elongated shape along this Y-axis. The upper or radially external end of the body 30, with respect to the X-axis, is connected to the disk 32 and located on the side of the blade 20. The lower end or radially internal to the body 30, relative to the X axis, is intended to be connected to an actuation mechanism for the blade pitch 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, includes an aerodynamic surface 34 intended to be aligned with the surface 12a of the hub 12 and thus to be swept by a flow of gas in operation.

[0068] In the example shown, the disk 32 includes 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 includes a housing 38 for receiving the foot 40 of the blade 20. In the example shown, the housing 38 is of the pinned type and the foot 40 of the blade 20 has a generally elongated shape with a preferably dovetail cross-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 cross-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 alignment axis Y and opens at its two longitudinal ends at the surface 36 in the example shown. There are therefore two openings of the housing 38, on the surface 36, diametrically opposite with respect to the Y axis.

[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] Figures 2 and 3 show 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 continuation of it.

[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 fibers, or by draping of plies or fabrics (woven or non-woven) which are superimposed one on the other.

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

[0077] Advantageously, the foot 40 of the blade 20 is 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] To this end, a manufacturing process for the blade 12 is proposed, which will be described below with reference to Figures 4 and following. Figures 4 and following illustrate several steps in this process.

[0079] Figure 4 illustrates a first step (a) of the process in which the fibrous body 50 of the blade 20 and the foot 40 of the blade 14 is prepared. As mentioned above, the fibrous body can be prepared by three-dimensional weaving of fibers or draping of folds. This yields a three-dimensional shape comprising a (part of) blade and a (part of) foot, the blade and foot being joined together. The foot 40 of the fibrous body 50 has a generally elongated shape and is preferably dovetail-shaped, with a length along its elongation axis Z denoted LL

[0080] Figure 5 illustrates another step (b) of the process in which the foot 40 is inserted into the housing 38 of the platform 22. As mentioned above, the housing 38 is obtained by pinning, 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 move within the housing 38. Figure 6 shows that, after the foot 40 has been mounted in the housing 38 of the platform 22, the length L1 of the foot 40 is greater than the length L2 of the housing 38. Figure 7 shows that the foot 40 has a complementary shape to the housing 38 of the platform 22, and that some clearance may exist between them after step (b).

[0081] Figure 8 illustrates another step (c) of the process in which a resin is injected into the recess 38 of the platform 22 so as to give it the function of an injection mold. 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 previously resin-impregnated foot into the recess of the platform.

[0082] The resin is intended to form the aforementioned polymeric 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 can constitute part of the injection mold and additional elements, such as molding shells 52, can be attached to the platform 22 in order to constitute the molding cavity all around the platform 22.

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

[0085] The molding shells 52 can function to compress these portions of the foot 40 radially inwards, with respect to the alignment axis Y (see arrows F). The molding shells 52 then act as compression shells for the foot and / or the resin. This solution has the advantage of filling assembly gaps to create a fixed connection.

[0086] To facilitate or allow compression of the foot in the platform housing, The base may initially have a larger volume than the platform housing.

[0087] During compression (and preferably also during resin polymerization), 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 brought onto the platform 22.

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

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

[0091] The method may further include an optional step f) illustrated in [Fig.9], in which the longitudinal protruding 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 foot 40 have portions of cylindrical surface which extend in the continuation 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 include a subsequent step g) of attaching two latches 54 to the platform 22, on either side of the foot 40 ([Fig. 11]). The latches 54 may be attached by means of screw-nut or similar elements.

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

[0095] A first of the locks 54 includes a first aerodynamic surface 54a located on the leading edge side 26, and a second of the locks 54 includes a second aerodynamic surface 54b located on the trailing edge side 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] Figures 13 and 14 represent an embodiment of a platform 22 for a rotor blade 14 according to the invention.

[0098] The dawn 14 includes all the features of those illustrated in figures 2 to 12 insofar as these features do not contradict the following.

[0099] As can be seen in [Fig. 15], which shows a simplified cross-sectional view of the housing 38 of a platform 22, this housing 38 is preferably dovetailed and comprises a bottom 38a extending between two lateral spans 38b and connected to these lateral spans. As mentioned above, the blade foot 40 preferably occupies the entire volume of this housing 38.

[0100] As illustrated in figures 13 and 14, the bearing surfaces 38b of the housing 38 include teeth 60 for hooking the foot 40.

[0101] The gripping teeth 60 are preferably anchored in the foot 40. This means that the teeth 60 penetrate and are engaged in the material of the foot 40. This mechanical anchoring reinforces the mechanical strength of the connection between the blade and the platform 22.

[0102] The teeth 60 are preferably distributed over the entire length L2 or longitudinal dimension of the housing 38, as in the example shown. The teeth 60 preferably extend over a dimension L3 along the Y axis which represents at least 20% of a maximum dimension Lmax of the housing 38 along this Y axis, and preferably at least 40% of this maximum dimension Lmax ([Fig. 15]).

[0103] The teeth 60 can extend to the opening of the housing 38 on the surface 34, as illustrated in the drawings.

[0104] Figures 16a and 16b illustrate alternative embodiments of the lateral bearing surfaces 38b and the teeth 60.

[0105] At least some of the teeth 60 on each of the spans 38b may have different shapes from the other teeth 60 of that span 38b.

[0106] The teeth 60 are separated from each other by inter-tooth cavities 62. At least some of these inter-tooth cavities 62 on each of the bearing surfaces 38b may have different shapes from the other inter-tooth cavities 62 of that bearing surface 38b.

[0107] The inter-tooth cavities 62 have, for example, in section a shape chosen from among a concave curved shape (shapes a, b and c in figure 16a), a preferably dovetail shape (shapes d in figure 16b), a shape in which at least one lateral face is inclined towards a leading edge or a trailing edge of the blade (shape e in figure 16b), and a random shape produced by machining (shapes f and F in figure 16b).

[0108] The teeth 60 preferably have a minimum height H or minimum projection dimension of between 0.05 and 2 mm. This height can be measured from the bottom of the interdental cavities 62

[0109] In the case where the blade 14 is obtained by the process described above, the foot 40 is housed without any play in the housing 38 and is secured to the platform 22 thanks to said polymer matrix.

[0110] The inter-dental cavities 62 are then preferably filled entirely by the polymeric matrix.

[0111] The foot 40 is also preferably mounted in a non-removable manner in the housing 38 of the platform 22.

Claims

Demands

1. Rotor blade (14) for an aircraft turbomachine propeller (10), said blade (14) comprising a blade (20) connected to a foot (40) which is housed in a platform (22), the blade (20) and the foot (40) being made of a composite material comprising a fibrous body (50) embedded in a polymer matrix, the blade (20) comprising an upper surface (21) and an lower surface (24) connected together at a leading edge (26) and a trailing edge (28) of the blade (20), the foot (40) having a generally elongated shape, the platform (22) being configured to define a blade (14) alignment axis (Y) which extends along an axis of elongation of the blade (20), the platform (22) comprising a housing (38) for receiving said foot (40), this housing (38) having a complementary form of this foot (40) and comprising a base (38a) connected to two lateral supports (38b), the lateral supports (38b) being able to retain the foot (40) along the axis (Y),characterized in that the lateral supports (38b) of the housing (38) include teeth (60) for attaching the foot (40).

2. Blade (14) according to claim 1, wherein the hooking teeth (60) are anchored in the foot (40).

3. Blade (14) according to any one of the preceding claims, wherein at least some of the teeth (60) on each of the bearings (38b) have different shapes from the other teeth (60) of that bearing (38b).

4. Blade (14) according to any one of the preceding claims, wherein the teeth (60) are separated from each other by inter-tooth cavities (62), at least some of the inter-tooth cavities (62) on each of the bearing surfaces (38b) having different shapes from the other inter-tooth cavities (62) of that bearing surface (38b).

5. Blade (14) according to the preceding claim, wherein the inter-tooth cavities (62) have in section a shape chosen from a concave curved shape, a dovetail shape, a shape in which at least one lateral face is inclined towards a leading edge or a trailing edge of the blade, and a random shape made by machining.

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

7. Blade (14) according to the preceding claim, dependent on the claim- indication 4 or 5, in which the inter-dental cavities (62) are completely filled by the polymeric matrix.

8. Blade (14) according to any one of the preceding claims, wherein the teeth (60) have a minimum height (H) or minimum projection dimension between 0.05 and 2 mm.

9. Blade (14) according to one of the preceding claims, wherein the foot (40) is mounted in a non-removable manner in the housing (38) of the platform (22).

10. Blade (14) according to any one of the preceding claims, wherein the teeth (60) are distributed over an entire length (L2) or longitudinal dimension of the housing (38).

11. Blade (14) according to any one of the preceding claims, wherein the teeth (60) extend over a dimension (L3) along the axis (Y) which represents at least 20% of a maximum dimension (Lmax) of the housing (38) along this axis (Y), and preferably at least 40% of this maximum dimension (Lmax).

12. Blade (14) according to any one of the preceding claims, 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).

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

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

15. Aircraft turbomachine, comprising a propeller (10) according to claim- previous indication.

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