Propeller blade or fan blade with a composite base in the shape of a cross or star

Abstract

Propeller blade with cross- or star-shaped composite base. A turboprop propeller blade (10) made of composite material comprises a matrix-densified fiber reinforcement. The propeller blade has, along a span direction (DL), a base (12) and an airfoil (11). The fiber reinforcement comprises a fibrous preform having a three-dimensional weave, with a portion of the base preform present in the base (12) and a portion of the airfoil preform present in the airfoil. The base and airfoil preform portions are bonded to each other by the three-dimensional weave. The base (12) has a plurality of branches. The base preform portion of the fibrous preform comprises a plurality of branches, each extending into a branch (23, 24, 25, 26) of the base (12). Figure for the abbreviation: Fig. 6.

Description

Title of the invention: Propeller blade or fan blade with a composite base in the shape of a cross or star. Technical field

[0001] The present invention relates to the field of propeller blades or vanes for aircraft such as those found on turboprops. Previous technique

[0002] Propeller blades for turboprop engines are generally made of metallic material. While metallic propeller blades have good mechanical strength, they have the disadvantage of being relatively heavy.

[0003] In order to obtain lighter blades or propeller blades, it is known to produce propeller blades from composite material, that is to say by producing structural parts with fiber reinforcement densified by a matrix.

[0004] US document 2013 / 0017093 describes the production of a propeller blade from a fiber structure with an aerodynamic profile into which a portion of a spar is inserted, one end of the spar being extended by a swollen portion intended to form the root of the propeller blade.

[0005] The new generation of engines requires more compact blade or vane feet. This need arises from the necessity of being able to rotate the blade or vane around its vertical axis in order to adapt its angle of attack to the flight regime (variable-pitch blade or vane). This need, combined with the fact that the blade or vane must be integrated as low as possible on the disc, necessitates a significant reduction in the size of the foot.

[0006] To this end, the feet of the new generation blades or vanes have an axisymmetric or substantially axisymmetric shape and reduced dimensions unlike the feet of the prior art such as those described in US document 2013 / 0017093 which extend over the entire width of the lower part of the blade or vane.

[0007] This axisymmetric or quasi-axisymmetric shape is more difficult to manufacture in composite material, in particular when three-dimensional (3D) weaving is used to form the fibrous reinforcement of the blade or vane.

[0008] Furthermore, the mechanical loads to which the new generation feet are subjected impose additional constraints. Indeed, in addition to the tensile and bending mechanical loads usually encountered (caused respectively by centrifugal forces and impacts with objects), the new generation feet can be integrated into the rotor disc using shells metallic, which results in an additional mechanical load in circumferential compression. Description of the invention

[0009] It is therefore desirable to be able to propose a solution for the production of aircraft propeller blades or blades in composite material with a compact base capable of withstanding various mechanical loads.

[0010] To this end, the present invention proposes a method for manufacturing a turboprop propeller blade or blade from a composite material comprising a fibrous reinforcement densified by a matrix, the method comprising: - the production by three-dimensional (3D) weaving of a one-piece fibrous blank, the fibrous blank having a flat shape extending along a longitudinal direction and a transverse direction corresponding respectively to the span direction and the chord direction of the blade or propeller blade to be manufactured, the fibrous blank comprising a root portion and an aerodynamic profile portion extending along the longitudinal direction from the root portion and along the transverse direction between a leading edge portion and a trailing edge portion, - the shaping of the fibrous blank to obtain a one-piece fibrous preform having said airfoil portion forming part of the airfoil preform and said foot portion forming part of the foot preform, and - the densification of the preform by a matrix to obtain a blade or propeller blade in composite material having a fibrous reinforcement constituted by the fibrous preform and densified by the matrix, and forming a single piece with integrated foot, characterized in that the foot part of the fibrous blank comprises several unbonds extending along a plane parallel to the surface of the fibrous blank, each unbond extends in the transverse direction from an edge of the foot part of the fibrous blank and over a distance less than half the width of the foot part, each unbond separating two woven portions in the fibrous blank and in that the shaping of the fibrous blank comprises the orientation in different directions of the woven portions separated by the unbonds so as to form a foot preform part comprising a plurality of branches.

[0011] The process of the invention thus makes it possible to produce a propeller blade or a blade with a composite base that is both compact and perfectly adapted to withstand the various mechanical loads described above. Indeed, the fibrous reinforcement portion of the base is made using 3D weaving and comprises a plurality of branches that are connected to the fibrous reinforcement portion of the aerodynamic profile at its center. By Consequently, the overall size of the foot is determined primarily by the length of the arms, resulting in a composite foot that is far more compact than those of the prior art, which generally extend across the entire width of the lower part of the airfoil. Within each arm, there are threads, such as warp threads, oriented in the span direction of the blade or vane, which, combined with the 3D weave, provides it with good tensile and flexural strength.

[0012] Moreover, the branched shape makes it possible to obtain a foot having an axisymmetric or quasi-axisymmetric shape compatible with integration into a rotation system or change of helix pitch.

[0013] By thus producing a fibrous reinforcement in which a part of the foot is fully formed, that is to say woven in one piece, with a part of the aerodynamic profile, a very good mechanical strength of the whole of the part is ensured and, in particular, at the level of the connection between the foot and the aerodynamic profile.

[0014] According to one embodiment of the process of the invention, the densification of the fibrous preform includes placing the preform in an injection mold having the shape of the blade or propeller blade to be manufactured, removable insertion elements being placed between the arms of the foot preform portion, the densification further including the injection of a resin into the fibrous preform held in the injection mold, the transformation of the resin into a matrix by heat treatment and the demolding of the blade or propeller blade, the demolding including the removal of the insertion elements so as to obtain a foot with a plurality of arms.

[0015] According to one embodiment of the process of the invention, the densification of the fibrous preform comprises placing the preform in an injection mold having the shape of the blade or propeller blade to be manufactured, with filler elements being placed between the arms of the base portion of the preform. The densification further comprises injecting a resin into the fibrous preform held in the injection mold, transforming the resin into a matrix by heat treatment, and demolding the blade or propeller blade so as to obtain a base comprising a skeleton with a plurality of arms, with the filler elements bonded to said arms. The filler elements enhance the mechanical resistance to circumferential compression.

[0016] According to one aspect of the process of the invention, the filling elements are made of a fibrous material chosen from one of the following fibrous materials: three-dimensional woven, unidirectional layers and fiber mat.

[0017] According to one aspect of the process of the invention, the filling elements are made of metallic material.

[0018] The invention also relates to a turboprop turbine blade or propeller blade made of composite material comprising a fibrous reinforcement densified by a matrix, the turbine blade or propeller blade having along a span direction a foot and an aerodynamic profile, the fibrous reinforcement comprising a fibrous preform having a three-dimensional weave with a part of the foot preform present in the foot and a part of the aerodynamic profile preform present in the aerodynamic profile, the parts of the foot preform and the aerodynamic profile being linked to each other by the three-dimensional weave, characterized in that the foot has a plurality of branches and in that the part of the foot preform of the fibrous preform comprises a plurality of branches each extending into a branch of the foot.

[0019] The invention further relates to a turboprop turbine blade or propeller blade made of composite material comprising a fibrous reinforcement densified by a matrix, the blade or propeller blade having along a span direction a foot and an aerodynamic profile, the fibrous reinforcement comprising a fibrous preform having a three-dimensional weave with a part of the foot preform present in the foot and a part of the aerodynamic profile preform present in the aerodynamic profile, the parts of the foot preform and the aerodynamic profile being linked to each other by the three-dimensional weave, characterized in that the foot has a bulbous shape, said foot comprising a skeleton having a plurality of branches with filling elements present between the branches and in that the part of the foot preform of the fibrous preform comprises a plurality of branches each extending into a branch of the foot skeleton.

[0020] According to one aspect of the blade or propeller blade of the invention, the filling elements are made of a fibrous material chosen from one of the following fibrous materials: three-dimensional woven, unidirectional layers and fiber mat.

[0021] According to another aspect of the blade or propeller blade of the invention, the filling elements are made of metallic material.

[0022] The invention further covers an aeronautical engine comprising a plurality of blades or propeller blades according to the invention as well as an aircraft comprising at least one such engine. Brief description of the drawings

[0023] [Fig-1] Fig. 1 is a schematic view illustrating the 3D weaving of a blank fibrous material for manufacturing a blade,

[0024] [Fig.2] [Fig.2] is an enlarged cross-sectional view in the weft direction of a set of yarn layers showing the formation of two unbonds in the foot part of the blank of [Fig.1] along a section plane II-II,

[0025] [Fig.3] The [Fig.3] is a perspective view showing the shaping of a part of the foot preform in the fibrous blank of the [Fig.1],

[0026] [Fig.4] [Fig.4] is a schematic exploded perspective view showing an injection mold and the placement of the fibrous preform of [Fig.3] inside it according to an embodiment of the invention,

[0027] [Fig.5] Fig.5 is a schematic perspective view showing the injection tooling of the closed Fig.4,

[0028] [Fig.6] Fig.6 is a schematic perspective view of a composite material blade obtained according to an embodiment of the invention,

[0029] [Fig.7] Fig.7 is a schematic exploded perspective view showing an injection mold and the placement of the fibrous preform of Fig.3 inside it according to another embodiment of the invention,

[0030] [Fig.8] Fig.8 is a schematic perspective view showing the injection tooling of the closed Fig.7,

[0031] [Fig. 9] [Fig. 9] is a schematic perspective view of a composite material blade obtained according to another embodiment of the invention. Description of embodiments

[0032] The invention applies generally to various types of propeller blades used in aircraft engines. The invention finds an advantageous, but not exclusive, application in large propeller blades intended for integration into pivoting or variable-pitch systems. Such propeller blades are generally equipped with a base that is both compact (small footprint) and offers good resistance to tensile, bending, and circumferential compression forces. The blade according to the invention can, in particular, be a blade for shrouded rotating wheels such as fan blades or a blade for unshrouded rotating wheels as in so-called "open rotor" aircraft engines.

[0033] In the following description, the embodiment examples are described in relation to turboprop turbine blades. However, the embodiment examples also apply to aircraft propeller blades.

[0034] Fig. 1 shows very schematically a fibrous blank 100 intended to form the fibrous preform of a blade to be produced.

[0035] The fiber structure 100 is obtained, as schematically illustrated in [Fig. 1], by three-dimensional (3D) weaving carried out in a known manner using a Jacquard-type loom on which a bundle of warp yarns 101 or strands is arranged in a plurality of layers of several hundred yarns each, the warp yarns being linked by weft yarns 102. The structure fibrous 100 is woven in one piece, the blank extending in a longitudinal direction DL, corresponding to the span direction of the blade to be manufactured, between a lower part 100c and an upper part 100d and in a transverse direction DT, corresponding to the chord direction of the blade to be manufactured between a front edge 100a and a rear edge 100b, the blank comprising an aerodynamic profile part 111 defining two faces 111e and 111f intended to form respectively the extrados and intrados faces of the blade and a foot part 112 intended to subsequently form a blade foot and extending outside the aerodynamic profile blank 111 along the longitudinal direction DL and set back from the front and rear edges 100a and 100b along the transverse direction DT.

[0036] In the illustrated example, the 3D weave is an "interlock" weave. By "interlock" weave, we mean here a weave structure in which each layer of weft yarns connects several layers of warp yarns with all the yarns in the same weft column having the same movement in the plane of the weave.

[0037] Other known types of three-dimensional weaving may be used, such as those described in document WO 2006 / 136755, the contents of which are incorporated herein by reference. This document describes, in particular, the production by one-piece weaving of reinforcing fibrous structures for parts such as blades, having a first type of core reinforcement and a second type of skin reinforcement, which provide both the mechanical and aerodynamic properties expected for this type of part.

[0038] The fibrous blank according to the invention can be woven in particular from carbon fiber yarns or ceramic such as silicon carbide.

[0039] As the fibrous blank, whose thickness and width vary, is woven, a certain number of warp yarns are not woven, which makes it possible to define the desired contour and thickness, continuously variable, of the blank 100. An example of evolving 3D weaving, in particular allowing the thickness of the blank to be varied between a first edge intended to form the leading edge and a second edge of lesser thickness intended to form the trailing edge, is described in US document 2006 / 257260.

[0040] According to the invention, during weaving, two unbindings 106 and 107 are made within the foot portion 112 of the fibrous blank 100 between two successive layers of warp yarns. The unbinding 106 extends along a plane parallel to the surface of the fibrous blank and over an unbinding zone delimited by a contour 106a, locally separating the foot portion 112 into two woven sections 113 and 114. Similarly, the unbinding 107 extends along a plane parallel to the surface of the fibrous blank and over an unbinding zone delimited by a contour 107a, separating locally the foot part 112 in two woven portions 115 and 116. In addition, the debonding 106 extends in the transverse direction from a first lateral edge 1120 of the foot part 112 and over a distance di06 less than half the width ln2 of the foot part 112 while the debonding 107 extends in the transverse direction from a second lateral edge 1121 of the foot part 112 and over a distance di07 less than half the width 1112 of the foot part 112. A bonding zone 117, that is to say a zone in which the blank is woven 3D in its entire thickness, is thus present in the foot part 112 between the two debondings 106 and 107.

[0041] A 3D interlock weave pattern of the blank 100 is shown schematically in [Fig. 2]. [Fig. 2] is a partial enlarged view of a warp cross-section in the foot portion 112 of the blank 100, including the unlinks 106 and 107 (section II-II in [Fig. 1]). In this example, the blank 100 comprises 8 layers of warp yarns 101 extending substantially in the longitudinal direction D1. In [Fig. 2], the 8 layers of warp yarns are linked by weft yarns Ti to T8 in the linking zone 117, the weft yarns extending substantially in the transverse direction DT. At the level of the unlinking 106, the woven portion 113 comprises 4 layers of warp yarns 101 linked together by 4 weft yarns Ti to T4 while the woven portion 114 comprises 4 layers of warp yarns linked together by 4 weft yarns T5 and T8.Similarly, at the unlinking point 107, the woven portion 115 comprises 4 layers of warp yarns 101 linked together by 4 weft yarns Ti to T4, while the woven portion 116 comprises 4 layers of warp yarns linked together by 4 weft yarns T5 and T8.

[0042] In other words, the fact that the weft yarns Ti to T4 do not extend into the warp yarn layers of the woven portions 114 and 116 and that the weft yarns T5 to T8 do not extend into the warp yarn layers of the woven portions 113 and 115 ensures the unbindings 106 and 107 which separate the woven portions 113 and 114, on the one hand, and the woven portions 115 and 116, on the other hand.

[0043] Once the weaving is complete, the non-woven yarns surrounding the fibrous blank 100 are cut to extract the blank, and then the foot portion of the blank is shaped. In the example described here, the shaping of the foot portion 112 is achieved by unfolding the woven portions 113 to 116 in different directions, as illustrated in [Fig. 3]. Generally, the woven portions separated from each other in the foot portion are unfolded in different directions to form an axisymmetric or quasi-axissymmetric foot skeleton, for example, but not limited to, in the shape of a cross or a star.

[0044] A fibrous preform 200 is thus obtained, comprising, along the longitudinal direction DL, a portion of the airfoil preform 211 and a portion of the foot preform 212, which in the example described here has a cross or star shape with four points 213 to 216 as shown in [Fig. 4]. The portion of the airfoil preform 211 extends along the transverse direction DT between a leading edge portion 211a and a trailing edge portion 211b. The number of points can vary. The foot portion of the blank can, for example, include four unbonds to obtain a foot preform with six points. Generally, the points of the foot preform extend along a plane parallel to the transverse direction DT.

[0045] The next step is to densify the fibrous preform. Densifying the fibrous preform intended to form the fibrous reinforcement of the part to be manufactured consists of filling the porosity of the preform, throughout all or part of its volume, with the material constituting the matrix. This densification is carried out in a manner known per se using the liquid-based process (CVL). The liquid-based process consists of impregnating the preform with a liquid composition containing a precursor of the matrix material. The precursor is usually in the form of a polymer, such as a high-performance epoxy resin, possibly diluted in a solvent. The preform is placed in a mold that can be sealed tightly with a cavity having the shape of the final molded blade.Next, the mold is closed and the liquid matrix precursor (for example, a resin) is injected throughout the cavity to impregnate the entire fibrous part of the preform.

[0046] The transformation of the precursor into a matrix, namely its polymerization, is carried out by heat treatment, generally by heating the mold, after removal of any solvent and crosslinking of the polymer, the preform always being held in the mold having a shape corresponding to that of the part to be produced.

[0047] In the case of forming a carbon or ceramic matrix, the heat treatment consists of pyrolyzing the precursor to transform the matrix into a carbon or ceramic matrix, depending on the precursor used and the pyrolysis conditions. For example, liquid ceramic precursors, particularly SiC, can be polycarbosilane (PCS), polytitanocarbosilane (PTCS), or polysilazane (PSZ) type resins, while liquid carbon precursors can be resins with a relatively high coke content, such as phenolic resins. Several consecutive cycles, from impregnation to heat treatment, can be carried out to achieve the desired degree of densification.

[0048] According to one aspect of the invention, in particular in the case of the formation of an organic matrix, the densification of the fibrous preform can be achieved by the well-known process of transfer molding called RTM ("Resin Transfer Moulding"). According to the RTM process, the fibrous preform is placed in a mold with the external shape of the part to be produced. A thermosetting resin is injected into the internal space of the mold containing the fibrous preform. A pressure gradient is generally established in this internal space between the point where the resin is injected and the resin outlets in order to control and optimize the impregnation of the preform by the resin.

[0049] As illustrated in [Fig.4], the injection of a liquid matrix precursor composition into the fibrous texture and its transformation into a matrix are here carried out in an injection tool 300 which includes a first shell 310 comprising in its center a first impression 311 corresponding in part to the shape and dimensions of the blade to be produced and a second shell 320 comprising in its center a second impression 321 corresponding in part to the shape and dimensions of the blade to be produced.

[0050] According to a first embodiment, removable insert elements 330 to 333 are placed between the branches 213 to 216 of the foot preform part 212. The removable insert elements can be made in particular of resin, of soluble salt core or of metal.

[0051] Once the tool 300 is closed as illustrated in [Fig. 5], the first and second cavities 311 and 321 of the first and second shells 310 and 320, respectively, together define an internal volume 301 having the shape of the blade to be produced, and in which the fiber preform 200 is placed. The fiber preform 200 can be compacted while the tool 300 is closed to obtain a specific fiber content in the preform. In this case, compaction pressure is applied to the shells 310 and 320, for example, by means of a press. The fiber preform can also be compacted in a separate tool before the preform is introduced into the injection mold.

[0052] The tooling 300 further comprises means for injecting a liquid matrix precursor and transforming this precursor into a matrix. More specifically, in the example described here, the first shell 310 of the tooling 300 includes an injection port 313 for injecting a liquid matrix precursor composition into the fibrous preform, while the second shell includes a discharge port 323 for cooperating with a pumping system for evacuating the tooling and drawing air during injection. The injection tooling 300 also includes a lower portion 340 and an upper portion 350 between which the first and second shells 310 and 320 are placed, the lower portion 340 and the upper portion 350 being equipped with heating means (not shown in [Fig. 5]).

[0053] Once the tooling 300 is closed, the blade is molded by impregnating the preform 200 with a thermosetting resin, which is then polymerized by heat treatment. The well-known injection or transfer molding process known as RTM ("Resin Transfer Molding") is used for this purpose. According to the RTM process, a resin 360, for example a thermosetting resin, is injected via the injection port 313 of the first shell 310 into the internal volume occupied by the preform 200. The port 323 of the second shell 320 is connected to a pressurized discharge conduit (not shown in [Fig. 5]). This configuration establishes a pressure gradient between the lower part of the preform 200, where the resin is injected, and the upper part of the preform located near the port 323.In this way, the resin 360, injected approximately at the lower part of the preform, will progressively impregnate the entire preform as it circulates within it until it reaches the discharge port 323, through which the excess is evacuated. Of course, the first and second shells 310 and 320 of the tooling 300 can respectively include several injection ports and several discharge ports.

[0054] The resin used can be, for example, an epoxy resin with a temperature class of 180 °C (maximum temperature that can withstand it without loss of properties). Resins suitable for RTM processes are well known. They preferably have a low viscosity to facilitate their injection into the fibers. The choice of temperature class and / or the chemical nature of the resin is determined according to the thermomechanical stresses to which the part must be subjected. Once the resin has been injected throughout the reinforcement, it is polymerized by heat treatment according to the RTM process.

[0055] After injection and polymerization, the blade is demolded. The insert elements 330 to 333 are then removed to obtain a blade root with a plurality of arms. Finally, the blade is trimmed to remove excess resin and the chamfers are machined. No further machining is necessary since, as the part is molded, it meets the required dimensions.

[0056] The densification processes described above make it possible to produce, from the fibrous preform of the invention, mainly blades or propeller blades in organic matrix composite material (CMO), carbon matrix (C / C) and ceramic matrix (CMC).

[0057] As illustrated in [Fig.6], a blade 10 is obtained formed of a fibrous reinforcement densified by a matrix which has in its lower part a foot 12 formed by the foot preform part 212 of the fibrous preform 200 and a blade 11 formed by the blade preform part 211 of the fibrous preform 200. The blade 10 has a leading edge 1la and a trailing edge 11b corresponding respectively to the leading edge parts 21la and trailing edge parts 211b of the fibrous preform 200. The foot 12 here has a cross or star shape with four branches 13 to 16 into which the branches 213 to 216 of the preform part of foot 212 extend respectively. The blade 10 thus includes a foot 12 which has a compact shape suitable for integration into a rotation system or change of propeller pitch.

[0058] According to a particular characteristic, some branches of the blade foot may have a greater thickness and / or length than others in order to adapt to the stresses experienced by the blade.

[0059] According to another embodiment shown in [Fig. 7], filler elements 217 to 220 are placed between the arms 213 to 216 of the foot preform portion 212 of the fibrous preform 200. The filler elements 217 to 220 differ from the removable insert elements 330 to 333 described previously in that they are intended to be retained in the final blade. The filler elements may be made of a fibrous material selected from one of the following: three-dimensional woven fibers, unidirectional layers, and fiber mats. The filler elements may also be made of metallic material.

[0060] The fibrous preform 200 equipped with the filling elements 217 to 220 is placed in an injection tool 400 similar to the tool 300 already described, that is to say which includes a first shell 410 comprising in its center a first impression 411 corresponding in part to the shape and dimensions of the blade to be produced and a second shell 420 comprising in its center a second impression 421 corresponding in part to the shape and dimensions of the blade to be produced.

[0061] Once the tooling 400 is closed as illustrated in [Fig. 8], the blade is molded by impregnating the preform 200 with a thermosetting resin, which is then polymerized by heat treatment. The well-known injection or transfer molding process known as RTM ("Resin Transfer Molding") is used for this purpose. According to the RTM process, a resin 460, for example a thermosetting resin, is injected via the injection port 413 of the first shell 410 into the internal volume occupied by the preform 400. The port 423 of the second shell 420 is connected to a pressurized discharge conduit (not shown in [Fig. 5]). This configuration establishes a pressure gradient between the lower part of the preform 200, where the resin is injected, and the upper part of the preform located near the port 423.In this way, the resin 460, injected approximately at the lower part of the preform, will progressively impregnate the entire preform as it circulates within it until it reaches the discharge port 423, through which the excess is evacuated. Of course, the first and second shells 410 and 420 of the tooling 400 can respectively include several injection ports. several evacuation ports. Once the resin has been injected throughout the reinforcement, it is polymerized by heat treatment in accordance with the RTM process using the upper 450 and lower 440 parts of the tooling 300 which are equipped with heating means (not shown in [Fig.7]).

[0062] After injection and polymerization, the blade is demolded and then trimmed to remove excess resin, and the chamfers are machined. No further machining is necessary since, as the part is molded, it meets the required dimensions.

[0063] As described above, it is possible to produce, from the fibrous preform of the invention, mainly blades or propeller blades in organic matrix composite material (CMO), carbon matrix (C / C) and ceramic matrix (CMC).

[0064] As illustrated in [Fig. 9], a blade 20 is obtained, formed from a fibrous reinforcement densified by a matrix, which has in its lower part a foot 22 formed by the foot preform portion 212 of the fibrous preform 200 and a blade 21 formed by the blade preform portion 211 of the fibrous preform 200. The blade 20 has a leading edge 21a and a trailing edge 21b corresponding respectively to the leading edge portions 21a and trailing edge portions 211b of the fibrous preform 200. The foot 22 has a bulbous shape and here comprises a skeleton with four branches 23 to 26 in which the branches 213 to 216 of the foot preform portion 212 extend respectively, with the filling elements 217 to 220 present between the branches 23 to 26.In the case where the filling elements are made of a fibrous material, they are also infiltrated by the resin injected into the tooling and bonded to the arms 213 to 216 of the foot preform 212 by co-densification. In the case where the filling elements are made of a metallic material, they are bonded to the arms 23 to 26 during the polymerization of the resin injected into the tooling or after polymerization. An adhesive may also be deposited on the contact surface of the filling elements 217 to 220 with the arms 213 to 216 of the foot preform 212. The blade 20 thus comprises a foot 22 which has a compact axisymmetric shape suitable for integration into a rotation or helix pitch change system.

[0065] The manufacturing process according to the present invention can in particular be used to produce turbomachine blades having a more complex geometry than the blades shown in Figures 6 and 9.

Claims

1. Demands Method for manufacturing a turboprop turbine blade or propeller blade from a composite material comprising a fibrous reinforcement densified by a matrix, the method comprising: - the production by three-dimensional weaving of a one-piece fibrous blank (100), the fibrous blank having a flat shape extending along a longitudinal direction (DL) and a transverse direction (DT) corresponding respectively to the span direction and the chord direction of the blade or propeller blade to be manufactured, the fibrous blank (100) comprising a root portion (112) and an airfoil portion (111) extending along the longitudinal direction (DL) from the root portion and along the transverse direction (DT) between a leading edge portion (100a) and a trailing edge portion (100b),- the shaping of the fibrous blank (100) to obtain a one-piece fibrous preform (200) having said airfoil portion forming an airfoil preform portion (211) and said foot portion forming a foot preform portion (212), and, - the densification of the preform (200) by a matrix to obtain a blade or propeller blade (10) of composite material having a fibrous reinforcement constituted by the fibrous preform and densified by the matrix, and forming a single piece with an integrated foot (12), characterized in that the foot portion of the fibrous blank (112) comprises several unbonds (106, 107) extending along a plane parallel to the surface of the fibrous blank (100), each unbond (106, 107) extending in the transverse direction (DT) from an edge (1120, 1121) of the foot portion (112) of the fibrous blank and over a distance (di06, di07) less than half the width (1112) of the foot portion, each unbond (106, 107) separating two woven portions (113, 114, 115, 116) in the fibrous rough (100) and in that the shaping of the fibrous rough includes the orientation in different directions of the woven portions (113, 114, 115, 116) separated by the unbindings (106,107) so as to form a preform foot part (212) comprising a plurality of branches (213, 214, 215, 216).

2. A method according to claim 1, wherein the densification of the fibrous preform (200) comprises placing the preform in an injection mold (300) having the shape of the blade or propeller blade to be manufactured, removable insertion elements (330, 331, 332, 333) being placed between the arms (213, 214, 215, 216) of the foot preform portion (212), the densification further comprising injecting a resin (360) into the fibrous preform (200) held in the injection mold (300), transforming the resin into a matrix by heat treatment and demolding the blade (10) or propeller blade, the demolding comprising removing the insertion elements so as to obtain a foot (12) with a plurality of arms (13, 14, 15, 16).

3. A method according to claim 1, wherein the densification of the fibrous preform (200) comprises placing the preform in an injection mold (400) having the shape of the blade or propeller blade to be manufactured, filling elements (217, 218, 219, 220) being placed between the arms (213, 214, 215, 216) of the foot preform portion (212), the densification further comprising injecting a resin (460) into the fibrous preform held in the injection mold, transforming the resin into a matrix by heat treatment and demolding the blade (20) or propeller blade so as to obtain a foot (22) comprising a skeleton formed of a plurality of arms (23, 24, 25, 26) with the filling elements bonded between the arms of said skeleton.

4. A method according to claim 3, wherein the filling elements (217, 218, 219, 220) are made of a fibrous material selected from one of the following fibrous materials: three-dimensional woven, unidirectional layers and fiber mat.

5. Method according to claim 3, wherein the filling elements are made of metallic material.

6. Propeller blade or vane (10) for a turboprop wheel made of composite material obtained by the process according to any one of claims 1 to 5, the blade or vane comprising a fibrous reinforcement densified by a matrix, the propeller blade or vane comprising along a span direction (DL) a foot (12) and an aerodynamic profile (11), the fibrous reinforcement comprising a fibrous preform (200) having a three-dimensional weave with a portion of the foot preform (212) present in the foot (12)

7.

8.

9.

10.

11. and a portion of the aerodynamic profile preform (211) present in the aerodynamic profile (111), the foot preform and aerodynamic profile portions being linked to each other by three-dimensional weaving, characterized in that the foot (12) has a plurality of branches (13, 14, 15, 16) and in that the foot preform portion (212) of the fibrous preform (200) comprises a plurality of branches (213, 214, 215, 216) each extending into a branch (13, 14, 15, 16) of the foot (12). turboprop blade or propeller blade (20) of composite material obtained by the process according to any one of claims 1 to 5, the blade or propeller comprising a matrix-densified fibrous reinforcement, the blade or propeller blade having, along a span direction (DL), a root (22) and an airfoil (21), the fibrous reinforcement comprising a fibrous preform (200) having a three-dimensional weave with a portion of the root preform (212) present in the root (22) and a portion of the airfoil preform (211) present in the airfoil (21), the portions of the root preform and the airfoil being linked to each other by the three-dimensional weave, characterized in that the root (22) has a bulbous shape, said root comprising a skeleton having a plurality of branches (23, 24, 25, 26) with filling elements (217, 218, 219,220) present between the branches and in that the foot preform part (212) of the fibrous preform (200) comprises a plurality of branches (213, 214, 215, 216) each extending into a branch (23, 24, 25, 26) of the foot skeleton (22). A propeller blade or fan blade according to claim 7, wherein the filling elements (217, 218, 219, 220) are made of a fibrous material selected from one of the following fibrous materials: three-dimensional woven fibers, unidirectional layers, and fiber mat. A propeller blade or fan blade according to claim 7, wherein the filling elements are made of metallic material. Aeronautical engine comprising a plurality of blades or propeller blades according to any one of claims 6 to 9. Aircraft comprising at least one engine according to claim 10.