PROPELLER BLADE OR SHOVEL WITH HOLLOW COMPOSITE FOOT

Description

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 offer good mechanical strength, they have the disadvantage of being relatively heavy.

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

[0004] US document 2013 / 0017093 describes the fabrication 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] US patent 2019 / 323357 A1 describes a blade comprising a composite material structure including a three-dimensionally woven fiber reinforcement and a matrix in which the fiber reinforcement is embedded, the composite material structure comprising an aerodynamically profiled blade portion and a blade root portion, the blade root portion comprising two sections each connected to the blade portion, a blade root attachment piece comprising a wall delimiting a cavity and an opening formed in the wall, the composite material structure extending through the opening such that the blade portion is located outside the attachment piece and the blade root portion is located inside the cavity, and a locking piece disposed in the cavity, between the two portions of the blade root portion,to keep the two portions separated from each other so as to prevent the blade's foot section from being pulled out of the cavity through the opening.

[0006] The new generation of engines requires more compact blade or vane feet. This need stems from the requirement to be able to rotate the blade or vane around its vertical axis to adapt its angle of attack to the flight regime (variable-pitch blade or vane). This requirement, combined with the fact that the blade or vane must be integrated as low as possible on the rotor disc, necessitates a significant reduction in the overall size of the foot.

[0007] For this purpose, 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 document US 2013 / 0017093 which extend over the entire width of the lower part of the blade or vane.

[0008] This axisymmetric or quasi-axisymmetric shape is more difficult to manufacture in composite material, especially when three-dimensional (3D) weaving is used to form the fibrous reinforcement of the blade or vane.

[0009] Furthermore, the mechanical loads to which the new generation feet are subjected impose additional constraints. Indeed, in addition to the usual tensile and bending mechanical loads (caused respectively by centrifugal forces and impacts with objects), the new generation feet can be integrated into the rotor disc using metal shells, which results in an additional circumferential compressive mechanical load. Description of the invention

[0010] It is therefore desirable to be able to offer a solution for the production of aircraft propeller blades or vanes in composite material with a compact base capable of withstanding various mechanical loads.

[0011] To this end, the present invention proposes a method for manufacturing a turboprop propeller blade or fan 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, 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 airfoil 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 the airfoil preform and said root portion forming the root preform,and the densification of the preform by a matrix to obtain a blade or propeller blade made of composite material having a fibrous reinforcement consisting of the fibrous preform and densified by the matrix, and forming a single piece with an integrated foot, characterized in that the foot portion of the fibrous blank includes a debonding delimiting an internal foot housing opening at a free end of said foot portion and extending along the longitudinal direction, and in that the shaping of the fibrous blank includes the positioning of at least one insertion element in the internal foot housing so as to form a bulbous foot preform portion.

[0012] The process of the invention thus makes it possible to produce a propeller blade or 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 has a bulbous shape that is connected to the fibrous reinforcement portion of the airfoil at its center or elsewhere. This results in a composite base that is much more compact than that of the prior art, which generally extends across the entire width of the lower part of the airfoil. Within this composite base, there are threads, for example warp threads, oriented in the span direction of the blade or blade, which, in combination with the 3D weave, gives it good tensile and flexural strength.In addition, in the composite foot there are threads, for example weft threads, oriented in the direction of the chord of the blade or vane which gives it good mechanical resistance in circumferential compression.

[0013] Furthermore, the bulb shape allows for a foot with an axisymmetric or quasi-axisymmetric shape compatible with integration into a rotation system or helix pitch change.

[0014] By creating a fibrous reinforcement in which a part of the foot is fully formed, i.e. woven in one piece, with a part of the aerodynamic profile, we ensure very good mechanical strength of the whole piece and, in particular, at the connection between the foot and the aerodynamic profile.

[0015] According to one embodiment of the process of the invention, the densification of the preform includes placing the fibrous preform in an injection tool having the shape of the blade or propeller blade to be manufactured, the densification further including the injection of a resin into the fibrous preform held in the injection tool, 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 said at least one insertion element so as to obtain a hollow foot.

[0016] According to another embodiment of the process of the invention, the densification of the preform includes placing the fibrous preform in an injection tool having the shape of the blade or propeller blade to be manufactured, the densification further including injecting a resin into the fibrous preform held in the injection tool, transforming the resin into a matrix by heat treatment and demolding the blade or propeller blade so as to obtain a base including a cavity with said at least one insertion element glued inside said cavity.

[0017] According to one aspect of the method of the invention, a lower portion of the aerodynamic profile part of the fibrous blank includes a debonding delimiting a passage between an edge of said aerodynamic profile part and the internal foot housing, said internal foot housing comprising along the longitudinal direction a first portion whose cross-section decreases between the free end of the foot part and an intermediate part of the housing and a second portion whose cross-section increases between said intermediate portion and the aerodynamic profile part, a first part of the insertion element having a flared shape being positioned in the first portion of the internal foot housing, a second part of the insertion element having a flared shape being positioned in the second portion of the internal foot housing via the passage present in the aerodynamic profile part.

[0018] According to another aspect of the process of the invention, the insertion element is made of one of the following materials: metallic material, resin and salt.

[0019] The invention also relates to a turboprop 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 part of the foot preform of the fibrous preform includes a debonding delimiting an internal foot housing forming a cavity opening at a free end of the foot.

[0020] According to one aspect of the blade or propeller blade of the invention, it further comprises at least one insertion element glued inside the cavity present in the base of the blade or propeller blade.

[0021] According to one aspect of the blade or propeller blade of the invention, the cavity of the foot comprises, along the span direction, a first portion whose cross-section decreases between the free end of the foot and an intermediate part of the housing and a second portion whose cross-section increases between said intermediate portion and the aerodynamic profile, a first part of the insertion element having a flared shape being present in the first portion of the cavity, a second part of the insertion element having a flared shape being present in the second portion of the cavity.

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

[0023] [ Fig. 1 ] There figure 1 is a schematic view illustrating the 3D weaving of a fibrous blank for the manufacture of a blade, [ Fig. 2 ] There figure 2 is a cross-sectional view in the weft direction at an enlarged scale of a set of yarn layers showing the formation of two unbindings in the toe portion of the rough draft of the figure 1 according to a section plan II-II, [ Fig. 3 ] There figure 3 is a cross-sectional view in the weft direction at an enlarged scale of a set of yarn layers showing the formation of two unbindings in the toe portion of the rough draft of the figure 1 according to a section plan III-III, [ Fig. 4 ] There figure 4 is a schematic perspective view showing the shaping of a portion of the foot preform in the fibrous roughing of the figure 1 , [ Fig. 5 ] There figure 5 is a schematic exploded perspective view showing an injection mold and the placement of the fibrous preform inside it according to an embodiment of the invention, [ Fig. 6 ] There figure 6 is a schematic perspective view showing the injection molding tooling of the figure 5 farm, [ Fig. 7 ] There figure 7 is a schematic perspective view of a composite material blade obtained according to an embodiment of the invention, [ Fig. 8 ] There figure 8 is a schematic perspective view of a composite material blade obtained according to another embodiment of the invention, [ Fig. 9 ] There figure 9 is a schematic perspective view of a fibrous blank according to another embodiment of the invention, [ Fig. 10 ] There figure 10 is a schematic perspective view showing the shaping of the fibrous rough-out of the figure 9 , [ Fig. 11 ] There figure 11 is a schematic perspective view of a composite material blade obtained according to another embodiment of the invention. Description of the implementation methods

[0024] The invention is generally applicable to various types of propeller blades used in aircraft engines. The invention finds 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 stresses. The blade according to the invention can, in particular, be used for shrouded rotating wheels such as fan blades or for unshrouded rotating wheels as in so-called "open rotor" aircraft engines.

[0025] In the following description, embodiment examples are described in relation to turboprop turbine blades. However, these embodiment examples also apply to aircraft propeller blades.

[0026] There figure 1 shows very schematically a fibrous rough 100 intended to form the fibrous preform of a blade to be produced.

[0027] The initial fibrous structure 100 is obtained, as schematically illustrated on the figure 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 has been arranged in a plurality of layers of several hundred yarns each, the warp yarns being linked by weft yarns 102.The fiber structure blank 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. In the illustrated example, the 3D weave is an "interlock" weave.By "interlock" weaving, we mean a weaving structure in which each layer of weft yarns connects several layers of warp yarns with all yarns in the same weft column having the same movement in the plane of the weave.

[0028] Other known types of three-dimensional weaving may be used, such as those described in document WO 2006 / 136755.

[0029] This document describes in particular the production by weaving in one piece of fibrous reinforcement structures for parts such as blades having a first type of core armor and a second type of skin armor which make it possible to confer both the mechanical and aerodynamic properties expected for this type of part.

[0030] The fibrous blank according to the invention can be woven in particular from carbon fiber yarns or ceramic such as silicon carbide.

[0031] As the fibrous blank, whose thickness and width vary, is woven, a certain number of warp threads 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, allowing in particular the variation of the thickness of the blank 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 document US 2006 / 257260.

[0032] According to the invention, during weaving, a debinding 106 is made inside the foot part 112 of the fibrous rough 100 between two successive layers of warp yarns. The debonding 106 extends along a plane parallel to the surface of the fibrous blank and over a debonding zone delimited by a contour 106a locally separating the foot portion 112 into two woven portions 113 and 114. In addition, the debonding 106 extends in the transverse direction between a first lateral edge 1120 and a second lateral edge 1121 and set back from these edges (i.e., the debonding 106 does not open onto the lateral edges 1120 and 1121) so as to maintain bonding portions 105 and 107 adjacent respectively to the first and second lateral edges 1120 and 1121. The debonding 106 also opens onto the free lower end 1122 of the foot portion 112.The detachment 106 thus forms an internal housing 140 in the foot part 112 which is accessible from the free lower end 1122.

[0033] A 3D interlock weave pattern of the 100 draft is shown schematically by the figure 2 . There figure 2 is a partial enlarged view of a cross-sectional plane in a portion of the rough 100 including the unbonding zone 106 (section II-II on the figure 1 ). In this example, the blank 100 comprises 8 layers of warp yarns 101 extending substantially in the longitudinal direction DL. On the figure 2 The 8 layers of warp yarns are linked by weft yarns T1 to T8 in the linking zones 105 and 107 of the foot portion 112 of the fibrous blank 100, the weft yarns extending substantially in the transverse direction DT. At the unlinking 106, the woven portion 113 comprises 4 layers of warp yarns 101 linked together by 4 weft yarns T1 to T4, while the woven portion 114 comprises the 4 layers of warp yarns forming the set of yarn layers 109, which are linked by 4 weft yarns T5 to T8.

[0034] In other words, the fact that the weft yarns T 1 to T 4 do not extend into the warp yarn layers of the woven portion 114 and that the weft yarns T 5 to T 8 do not extend into the warp yarn layers of the woven portion 113 ensures the unbinding 106 which separates the woven portions 113 and 114.

[0035] In the weaving example shown on the figure 2 , the weft yarns T 1 to T 4, on the one hand, and the weft yarns T 5 to T 8, on the other hand, are respectively arranged on each side of the unlinking 106, the weft yarns T 1 to T 4 linking the first four layers of warp yarns forming the woven portion 113 and the weft yarns T 5 to T 8 linking the last four layers of warp yarns forming the woven portion 114.

[0036] According to an alternative embodiment illustrated in figure 3 (section III-III on the figure 1 ), a first set of weft yarns from the weft yarn layers crosses a second set of weft yarns from the weft yarn layers in a zone of the fibrous rough 100 located in the vicinity of the unlinking 106 along the transverse direction DT, the yarns of the first set of weft yarns 102 extending on one side of the unlinking 106 along the transverse direction DT while the yarns of the second set of yarns from the plurality of weft yarn layers 102 extending on the other side of the unlinking 106 along the transverse direction DT. More precisely, one or more weft yarns 102 linking warp yarn layers forming a set of yarn layers 108 in the linking zone 105 are used to link warp yarn layers forming a set of yarn layers 109 in the linking zones 107 and vice versa. In the example illustrated on the figure 3 , weft yarns T 3 and T 4, linking layers of warp yarns 101 of the set of yarn layers 108 in the first linking zone 105 are deflected at the beginning or upstream of the unlinking 106 along the transverse direction DT to link layers of warp yarns 101 of the set of yarn layers 109. Similarly, weft yarns T 5 and T 6, linking layers of warp yarns 101 of the set of yarn layers 109 in the first linking zone 105 are deflected at the beginning or upstream of the unlinking 106 along the transverse direction DT to link layers of warp yarns 101 of the set of yarn layers 108.After the unlinking 106, the weft yarns T3 and T4 are again deflected at the end or downstream of the unlinking 106 along the transverse direction DT, that is, upon their entry into the second linking zone 107, to link layers of warp yarns 101 of the set of yarn layers 109, while the weft yarns T5 and T6 are again deflected at the end or downstream of the unlinking 106 along the transverse direction DT, that is, upon their entry into the second linking zone 107, to link layers of warp yarns 101 of the set of yarn layers 108. The crossing of the weft yarns T3 and T4 and the weft yarns T5 and T6 upstream and / or downstream of the unlinking 106 along the transverse direction DT improves the strength of the blank. fibrous in the unbinding zone. According to an alternative embodiment, part of the weft yarns may cross only upstream or downstream of the unbinding 106 along the transverse direction DT.

[0037] 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 carried out by separating the woven sections 113 and 114 and inserting an insert element 130 into the internal recess 140 formed by the unbinding 106, as illustrated in the figure. figure 4 The insert element can be made of metallic material or resin, for example, using additive manufacturing. It can also be made with a salt that can be dissolved after densification.

[0038] This yields a fibrous preform 200 comprising, along the longitudinal direction DL, a portion of the aerodynamic profile preform 211 and a portion of the foot preform 212 having a bulbous shape with an internal housing 240 comprising the insertion element 130 as shown in the figure 5 . The preform portion of the aerodynamic profile 211 extending along the transverse direction DT between a leading edge portion 211a and a trailing edge portion 211b.

[0039] 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, involves filling the preform's porosity, throughout all or part of its volume, with the matrix material. This densification is carried out using a well-known liquid-based process (CVL). The liquid-based process involves 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 shaped like the final molded blade. The mold is then closed, and the liquid matrix precursor (for example, a resin) is injected into the entire cavity to impregnate the entire fibrous portion of the preform.

[0040] 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 kept in the mold having a shape corresponding to that of the part to be produced.

[0041] In the case of carbon or ceramic matrix formation, 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 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.

[0042] According to one aspect of the invention, particularly in the case of forming an organic matrix, the densification of the fibrous preform can be achieved by the well-known resin transfer molding (RTM) process. According to the RTM process, the fibrous preform is placed in a mold having 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 discharge ports in order to control and optimize the impregnation of the preform by the resin.

[0043] As illustrated on the figure 5 , 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.

[0044] Once the 300 tool is closed as illustrated on the figure 6 The first and second impressions 311 and 321 of the first and second molds 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 with the tooling 300 closed to obtain a specific fiber content in the preform. In this case, compaction pressure is applied to the molds 310 and 320, for example, using a press. The fiber preform can also be compacted in a separate mold before being introduced into the injection mold.

[0045] The tooling 300 further includes 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 the figure). figure 6 ).

[0046] 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. This is done using the well-known injection or transfer molding process known as RTM ("Resin Transfer Molding"). According to the RTM process, a resin 360, for example a thermosetting resin, is injected through 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 the diagram). figure 6 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 port 323. In this way, the resin 360, injected at approximately the lower part of the preform, will progressively permeate the entire preform as it circulates through it until it reaches the discharge port 323, through which the excess resin is evacuated. Naturally, the first and second shells 310 and 320 of the tooling 300 can each include several injection ports and several discharge ports, respectively.

[0047] The resin used can be, for example, an epoxy resin with a temperature class of 180 °C (the 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 will be subjected. Once the resin has been injected throughout the reinforcement, it is cured by heat treatment according to the RTM process.

[0048] After injection and polymerization, the blade is demolded. The 130 insert element is then removed to create a hollow blade root. Finally, the blade is trimmed to remove excess resin, and the chamfers are machined. No further machining is required since the part, being molded, meets the required dimensions.

[0049] 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).

[0050] As illustrated on the figure 7 A blade 10 is obtained, formed from a fibrous reinforcement densified by a matrix, which has in its lower part a foot 12 formed by the foot preform portion 212 of the fibrous preform 200 and a blade 11 formed by the blade preform portion 211 of the fibrous preform 200. The blade 10 has a leading edge 11a and a trailing edge 11b corresponding respectively to the leading edge portions 211a and trailing edge portions 211b of the fibrous preform 200. The foot 12 includes a cavity 14 formed by the internal housing 240 of the fibrous preform 200, the cavity 14 opening at the free end 12a of the foot 12. The blade 10 thus includes a foot 12 which has a compact axisymmetric shape suitable for integration into a rotation or propeller pitch change system.

[0051] According to one embodiment, the insertion element 130 is retained after demolding. In this case, we obtain, as illustrated in the figure 8 A blade 20 formed of a fibrous reinforcement densified by a matrix, which includes 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 211a and trailing edge portions 211b of the fibrous preform 200. The foot 22 includes a cavity 24 formed by the internal housing 240 of the fibrous preform 200, the insertion element 130 being bonded inside said cavity 24. The blade 20 thus includes a foot 22 which has a compact axisymmetric shape suitable for integration into a rotation or propeller pitch change system.

[0052] There figure 9 This illustrates a fiber blank 400 of a blade according to another embodiment. The fiber blank 400 is produced by 3D weaving under the same conditions as the blank 100 described previously. The fiber blank 400 differs from the fiber blank 100 already described in that the internal foot housing, delimited by the unbundling, has an "hourglass" or "diabolo" geometry in which it is not possible to insert an insert element of a corresponding shape through the single opening present at the free end of the foot portion of the fiber blank. For this purpose, a two-part insert element is used, while the fiber blank includes an additional unbundling allowing the insertion of one of the two parts of the insert element.

[0053] More specifically, the fibrous blank 400 extends in a longitudinal direction DL, corresponding to the span direction of the blade to be manufactured, between a lower part 400c and an upper part 400d and in a transverse direction DT, corresponding to the chord direction of the blade to be manufactured between a leading edge 400a and a trailing edge 400b, the blank comprising an airfoil portion 411 defining two faces 411e and 411f intended to form respectively the upper and lower surfaces of the blade and a foot portion 412 intended to subsequently form a blade foot and extending outside the airfoil blank 411 along the longitudinal direction DL and set back from the leading and trailing edges 400a and 400b along the transverse direction DT.

[0054] According to the invention, during weaving, a first unbinding 406 is carried out inside the foot part 412 of the fibrous rough 400 between two successive layers of warp yarns. The debonding 406 extends along a plane parallel to the surface of the fibrous blank and over a debonding zone delimited by a contour 406a, locally separating the foot portion 412 into two woven sections 413 and 414. Furthermore, the debonding 406 extends in the transverse direction between a first lateral edge 4120 and a second lateral edge 4121 and is set back from these edges so as to maintain bonding sections 405 and 407 adjacent respectively to the first and second lateral edges 4120 and 4121. The debonding 406 also terminates at the free lower end 4122 of the foot portion 412.

[0055] The width of the joint 406 varies between the free lower end 4122 of the foot section and the end 4123 of the foot section opposite end 4122 along the longitudinal direction DL. The joint 406 here delimits an internal housing 440 which, along the longitudinal direction DL, comprises a first portion 441 whose cross-section decreases between the free end 4122 of the foot section 412 and an intermediate portion 443 of the internal housing 440, and a second portion 442 whose cross-section increases between the intermediate portion 443 and the aerodynamic profile section 411. The first portion 441 of the internal housing 440 is accessible through the free lower end 4122.

[0056] An additional linkage 407 delimiting a passage 450 between an edge, here the edge 400b of the aerodynamic profile part 411 and the internal housing 440 in the foot part 412. The second part 442 of the internal housing 440 is accessible through the passage 450.

[0057] On the figure 10 , the shaping of the foot part of the fibrous blank is carried out by introducing a first part 431 of a flared insert element 430 into the first portion 441 of the internal housing 440 through the free lower end 4122, on the one hand, and by introducing a second part 432 of the insert element 430 into the second portion 442 of the internal housing 440 through the passage 450.

[0058] Once the fibrous preform has been produced, it is placed in an injection mold to form a matrix as explained in detail previously and which is not described again here for the sake of simplification.

[0059] We then obtain, as illustrated on the figure 11A blade 30 formed of a fibrous reinforcement densified by a matrix, which has in its lower part a foot 32 formed by the foot preform portion of the fibrous preform and a blade 31 formed by the blade preform portion of the fibrous preform. The blade 30 has a leading edge 31a and a trailing edge 31b corresponding respectively to the leading and trailing edge portions of the fibrous preform.The foot 32 includes a cavity 34 formed by the internal housing 440 of the fibrous preform 400, the cavity 34 including the insertion element 430 bonded inside said cavity 34, the first part 431 of the flared insertion element 430 being present and bonded in a first portion 341 of the cavity 34 corresponding to the first portion 441 of the internal housing 440 while the second part 432 of the insertion element 430 is present and bonded in a second portion 342 of the cavity 34 corresponding to the second portion 442 of the internal housing 440. The first and second parts 431 and 432 of the insertion element 430 may further be bonded at their contact interface. The blade 30 thus includes a foot 32 which has a compact axisymmetric shape suitable for integration into a system of rotation or change of propeller pitch.

[0060] The shaping of the aerodynamic profile of the previously described fibrous blanks may involve inserting one or more conforming pieces into one or more joints in the aerodynamic profile. The conforming piece(s) are preferably made of a lightweight, low-density rigid material such as a rigid, honeycomb-structured material.

Claims

1. A manufacturing method for a propeller blade or airfoil (10) for a turboprop engine, of composite material, comprising a fibrous reinforcement densified by a matrix, the method comprising: - producing a one-piece fibrous blank (100) by three-dimensional weaving, the fibrous blank having a flat shape extending in a longitudinal direction (DL) and a transverse direction (DT) corresponding respectively to the span direction and to the chord direction of the propeller blade or airfoil to be manufactured, the fibrous blank (100) comprising a root portion (112) and an aerodynamic profile portion (111) extending in the longitudinal direction (DL) from the root portion and in the transverse direction (DT) between a leading edge portion (100a) and a trailing edge portion (100b), - forming the fibrous blank (100) for obtaining a one-piece fibrous preform (200) having said aerodynamic profile portion (111) forming an aerodynamic profile preform (211) and said root portion (112) forming a root preform portion (212), and - densifying the fibrous preform (200) with a matrix for obtaining a propeller blade or airfoil (10), of composite material, having a fibrous reinforcement consisting of the fibrous preform (200) and densified by the matrix, and forming a single part with integrated root (12), so that the root portion (112) of the fibrous blank (100) comprises an unlinked area (106) delimiting an internal root recess (140) opening at a free end (1122) of said root portion and extending in the longitudinal direction (DL), said unlinked area extending in the transverse direction between a first lateral edge (1120) and a second lateral edge (1121) and recessed from said lateral edges, and in that the forming of the fibrous blank (100) comprises the positioning of at least one insertion element (130) in the internal root recess (140) so as to form a bulb-shaped root preform portion (212).

2. The method according to claim 1, wherein the densification of the preform comprises the placement of the fibrous preform (200) into injection tooling (300) having the shape of the propeller blade or airfoil to be manufactured, the densification also comprising the injection of a resin (360) into the fibrous preform held in the injection tooling (300), the transformation of the resin into a matrix by thermal treatment and the removal of the propeller blade (10) or airfoil from the mold, the removal from the mold comprising the removal of said at least one insertion element (130) so as to obtain a hollow root (12).

3. The method according to claim 1, wherein the densification of the preform comprises the placement of the fibrous preform (200) into injection tooling (300) having the shape of the propeller blade or airfoil to be manufactured, the densification also comprising the injection of a resin (360) into the fibrous preform held in the injection tooling (300), the transformation of the resin into a matrix by thermal treatment and the removal of the propeller blade or airfoil from the mold so as to obtain a root (22) comprising a cavity, (24) with said at least one insertion element (130) glued inside said cavity.

4. The method according to claim 3, wherein a lower portion of the aerodynamic profile portion (411) of the fibrous blank (400) comprises an unlinked area (407) delimiting a passage (450) between one edge (400b) of said aerodynamic profile portion and the internal root recess (440), said internal root recess including, in the longitudinal direction (DL), a first portion (441), the cross section of which decreases between the free end (4122) of the root portion (412) and an intermediate portion (443) of the recess and a second portion (442), the cross section of which increases between said intermediate portion and the aerodynamic profile portion (411), a first portion (431) of the insertion element (430), having a flared shape, being positioned in the first portion (441) of the internal root recess (440), a second portion (432) of the insertion element having a flared shape being positioned in the second portion (442) of the internal root recess via the passage (450) present in the aerodynamic profile portion (411).

5. The method according to claim 3 or 4, wherein the insertion element (130, 430) is constituted of one of the following materials: metallic material, resin and salt.

6. A propeller (10) blade or airfoil, of a turboprop engine, of composite material comprising a fibrous reinforcement densified by a matrix, the propeller blade or airfoil including, in a span direction (DL), a root (12) and an aerodynamic profile (11), the fibrous reinforcement comprising a fibrous preform (200) having a three-dimensional weave with a root preform portion (212) present in the root (12) and an aerodynamic profile portion (211) present in the aerodynamic profile (11), the root and aerodynamic profile preform portions being linked to one another by the three-dimensional weave, so that the root preform portion (212) of the fibrous preform (200) comprises an unlinked area (106) delimiting an internal root recess (140) forming a cavity (14) opening at a free end (12a) of the root (12), the unlinked area extending in a transverse direction between the first and second linking portions (105, 107).

7. The propeller blade or airfoil (20) according to claim 6, also comprising at least one insertion element (130) glued inside the cavity (24) present in the root (22) of the propeller blade or airfoil.

8. The propeller blade or airfoil (30) according to claim 6 or 7, wherein the cavity (34) of the root (32) includes, in the span direction (DL), a first portion (341), the cross section of which decreases between the free end of the root (32) and an intermediate portion of the recess, and a second portion (342), the cross section of which increases between said intermediate portion and the aerodynamic profile (31), a first portion (431) of the insertion element (430), having a flared shape, being present in the first portion (341) of the cavity (34), a second portion (432) of the insertion element, having a flared shape, being present in the second portion (342) of said cavity.

9. An aeronautical engine comprising a plurality of propeller blades or airfoils according to any one of claims 6 to 8.

10. An aircraft comprising at least one engine according to claim 9.