Propeller blade or vane with hollow composite base

Abstract

Propeller blade with hollow 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 fiber 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 (11). The base and airfoil preform portions are bonded to each other by the three-dimensional weave. The base preform portion of the fiber preform includes a debonding delimiting an internal base housing forming a cavity (14) opening at a free end (12a) of the base (12). Figure for the abbreviation: Fig. 7.

Description

Title of the invention: Propeller blade or vane with hollow composite root Technical field

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

[0002] Propeller blades or vanes for turboprops are generally made of metallic material. Although propeller blades or vanes made of metallic material have good mechanical strength, they nevertheless have the disadvantage of having a relatively high mass.

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

[0004] Document US 2013 / 0017093 describes the production of a propeller blade from a fiber structure with an aerodynamic profile inside which a part of a spar is introduced, 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 roots. This need arises from the necessity to be able to pivot the blade or vane around its vertical axis in order to adapt its incidence 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, requires a significant reduction in the size of the root.

[0006] For this purpose, the roots of the new generation blades or vanes have an axisymmetric or substantially axisymmetric shape as well as reduced dimensions unlike the roots 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.

[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 fiber 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 mechanical loads in traction and bending 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 additional mechanical loading in circumferential compression. Statement of the invention

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

[0010] To this end, the present invention proposes a method for manufacturing a turboprop propeller blade or blade made of composite material comprising a fibrous reinforcement densified by a matrix, the method comprising: - the production by three-dimensional weaving of a single-piece fiber blank, the fiber blank having a flat shape extending in 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 fiber blank comprising a root portion and an aerodynamic profile portion extending in the longitudinal direction from the root portion and in the transverse direction between a leading edge portion and a trailing edge portion, - shaping the fiber blank to obtain a one-piece fiber preform having said aerodynamic profile portion forming an aerodynamic profile preform and said foot portion forming a foot preform, and - densifying the preform by a matrix to obtain a blade or propeller blade made of 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 a delinking delimiting an internal foot housing opening at a free end of said foot part and extending in the longitudinal direction and in that the shaping of the fibrous blank comprises the positioning of at least one insertion element in the internal foot housing so as to form a bulb-shaped foot preform part.

[0011] The method of the invention thus makes it possible to produce a propeller blade or a vane with a composite root which is both compact and perfectly adapted to withstand the various mechanical loads described above. Indeed, the fiber reinforcement part of the root is made in 3D weaving and has a bulb shape which is connected to the fiber reinforcement part of the aerodynamic profile in its center or elsewhere. This produces a composite root which is much more compact than that of the prior art which generally extends over the entire width of the lower part of the aerodynamic profile. In this composite root, there are threads, for example warp threads, oriented in the span direction of the blade or vane which gives it good mechanical resistance in tension and bending in combination with the 3D weaving. In addition, in the composite root, there are threads, for example weft threads, oriented in the chord direction of the blade or vane which gives it good mechanical resistance in circumferential compression.

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

[0013] By thus producing a fibrous reinforcement in which a foot part is integrally formed, i.e. woven in a single piece, with an aerodynamic profile part, very good mechanical strength of the entire 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 method of the invention, the densification of the preform comprises the placement of the fiber preform in an injection tool having the shape of the blade or propeller blade to be manufactured, the densification further comprising the injection of a resin into the fiber 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 comprising the removal of said at least one insertion element so as to obtain a hollow root.

[0015] According to another embodiment of the method of the invention, the densification of the preform comprises the placement of the fiber preform in an injection tool having the shape of the blade or propeller blade to be manufactured, the densification further comprising the injection of a resin into the fiber 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 so as to obtain a root comprising a cavity with said at least one insertion element glued inside said cavity.

[0016] According to one aspect of the method of the invention, a lower portion of the aerodynamic profile part of the fiber blank comprises a delinking delimiting a passage between an edge of said aerodynamic profile part and the internal foot housing, said internal foot housing comprising, in the longitudinal direction, a first portion whose section decreases between the free end of the foot part and an intermediate portion of the housing and a second portion whose section increases between said intermediate portion and the aerodynamic profile part, a first portion of the insertion element having a flared shape being positioned in the first portion of the internal foot housing, a second portion 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.

[0017] According to another aspect of the method of the invention, the insertion element is made of one of the following materials: metallic material, resin and salt.

[0018] The invention also relates to a turbopropeller blade or propeller blade made of composite material comprising a fibrous reinforcement densified by a matrix, the blade or propeller blade comprising, in a spanwise direction, a root and an aerodynamic profile, the fibrous reinforcement comprising a fibrous preform having a three-dimensional weave with a root preform portion present in the root and an aerodynamic profile preform portion present in the aerodynamic profile, the root preform and aerodynamic profile preform portions being linked to each other by the three-dimensional weave, characterized in that the root preform portion of the fibrous preform comprises a delinking delimiting an internal root housing forming a cavity opening at a free end of the root.

[0019] According to one aspect of the propeller blade or vane of the invention, the latter further comprises at least one insertion element glued inside the cavity present in the root of the propeller blade or vane.

[0020] According to one aspect of the propeller blade or vane of the invention, the cavity of the root comprises, along the span direction, a first portion whose section decreases between the free end of the root and an intermediate part of the housing and a second portion whose 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.

[0021] The invention further covers an aeronautical engine comprising a plurality of propeller blades or vanes according to the invention as well as an aircraft comprising at least one such engine. Brief description of the drawings

[0022] [Fig-1] [Fig.l] is a schematic view illustrating the 3D weaving of a blank fibrous for the manufacture of a blade,

[0023] [Fig.2] [Fig.2] is an enlarged scale cross-sectional view in the weft direction of a set of layers of yarns showing the formation of two unlinkages in the foot part of the blank of [Fig.l] according to a section plane II-II,

[0024] [Fig.3] [Fig.3] is an enlarged scale cross-sectional view in the weft direction of a set of layers of yarns showing the formation of two unlinkages in the foot part of the blank of [Fig.l] according to a section plane III-III,

[0025] [Fig.4] [Fig.4] is a schematic perspective view showing the shaping of a foot preform portion in the fiber blank of [Fig.l],

[0026] [Fig.5] [Fig.5] is an exploded perspective schematic view showing an injection tool and the placement of the fiber preform therein in accordance with one embodiment of the invention,

[0027] [Fig.6] [Fig.6] is a schematic perspective view showing the injection tooling of [Fig.5] closed,

[0028] [Fig.7] [Fig.7] is a schematic perspective view of a composite material blade obtained in accordance with one embodiment of the invention,

[0029] [Fig.8] [Fig.8] is a schematic perspective view of a composite material blade obtained in accordance with another embodiment of the invention,

[0030] [Fig.9] [Fig.9] is a schematic perspective view of a fiber blank in accordance with another embodiment of the invention,

[0031] [Fig. 10] [Fig. 10] is a schematic perspective view showing the shaping of the fiber blank of [Fig.9],

[0032] [Fig. 11] [Fig. 11] is a schematic perspective view of a composite material blade obtained in accordance with another embodiment of the invention. Description of the embodiments

[0033] The invention applies generally to different types of propeller blades or vanes used in aircraft engines. The invention finds an advantageous but not exclusive application in large propeller blades or vanes which are intended to be integrated into pivoting or variable pitch systems. Such propeller blades or vanes are generally provided with a root having both a small footprint (compact shape) and good resistance to tensile, bending and circumferential compression forces. The vane according to the invention may in particular constitute a vane for shrouded moving wheels such as fan blades or a vane for unshrouded moving wheels as in so-called "open rotor" aeronautical engines.

[0034] In the remainder of the description, the exemplary embodiments are described in relation to turboprop blades. However, the exemplary embodiments also apply to propeller blades for aircraft.

[0035] [Fig.l] shows very schematically a fiber blank 100 intended to form the fiber preform of a blade to be produced.

[0036] The blank of fibrous structure 100 is obtained, as schematically illustrated in [Fig.l], by three-dimensional (3D) weaving carried out in a known manner using a jacquard-type loom on which a bundle of warp threads 101 or strands has been arranged in a plurality of layers of several hundred threads each, the warp threads being linked by weft threads 102. The blank of fibrous structure 100 is woven in a single piece, the blank extending in one direction longitudinal 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 root part 112 intended to subsequently form a blade root and extending outside the aerodynamic profile blank 111 in the longitudinal direction DL and set back from the front and rear edges 100a and 100b in the transverse direction DT.

[0037] In the example illustrated, the 3D weave is an "interlock" weave. By "interlock" we mean here a weave weave in which each layer of weft threads links several layers of warp threads with all the threads of the same weft column having the same movement in the plane of the weave.

[0038] Other known types of three-dimensional weaving may be used, such as those described in document WO 2006 / 136755. This document describes in particular the production by weaving in a single piece of fiber 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.

[0039] The fiber blank according to the invention can be woven in particular from carbon fiber or ceramic fiber threads such as silicon carbide.

[0040] As the fiber blank, the thickness and width of which vary, is woven, a certain number of warp threads are not woven, which makes it possible to define the desired, continuously variable contour and thickness of the blank 100. An example of scalable 3D weaving, in particular making it possible to vary the thickness of the blank between a first edge intended to form the leading edge and a second edge of lesser thickness and intended to form the trailing edge, is described in document US 2006 / 257260.

[0041] According to the invention, during weaving, a separation 106 is produced inside the foot portion 112 of the fiber blank 100 between two successive layers of warp threads. The separation 106 extends along a plane parallel to the surface of the fiber blank and over a separation zone delimited by a contour 106a locally separating the foot portion 112 into two woven portions 113 and 114. Furthermore, the separation 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 separation 106 does not open onto the lateral edges 1120 and 1121) so as to maintain connecting portions 105 and 107 adjacent to the first lateral edges 1120 and 1121 respectively. and second lateral edges 1120 and 1121. The disconnection 106 further opens at the free lower end 1122 of the foot part 112. The disconnection 106 thus forms an internal housing 140 in the foot part 112 which is accessible via the free lower end 1122.

[0042] A 3D interlock weaving mode of the blank 100 is shown schematically in [Fig. 2]. [Fig. 2] is an enlarged partial view of a warp sectional plane in a portion of the blank 100 comprising the unlinking zone 106 (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 DL. In [Fig. 2], the 8 layers of warp yarns are linked by weft yarns Ti to T8 in the linking zones 105 and 107 of the foot portion 112 of the fiber blank 100, 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 threads 101 linked together by 4 weft threads Ti to T4 while the woven portion 114 comprises the 4 layers of warp threads forming the set of layers of threads 109 are linked by 4 weft threads T5 to T8.

[0043] In other words, the fact that the weft threads Ti to T4 do not extend into the layers of warp threads of the woven portion 114 and that the weft threads T5 to T8 do not extend into the layers of warp threads of the woven portion 113 ensures the delinking 106 which separates the woven portions 113 and 114.

[0044] In the weaving example presented in [Fig. 2], the weft threads Ti to T4, on the one hand, and the weft threads T5 to T8, on the other hand, are respectively arranged on each side of the unlinking 106, the weft threads Ti to T4 binding the first four layers of warp threads forming the woven portion 113 and the weft threads T5 to T8 binding the last four layers of warp threads forming the woven portion 114.

[0045] According to an alternative embodiment illustrated in [Fig. 3] (section III-III in [Fig. 1]), a first portion of yarns of the layers of weft yarns crosses a second portion of yarns of the layers of weft yarns in a zone of the fiber blank 100 located in the vicinity of the uncoupling 106 in the transverse direction DT, the yarns of the first portion of weft yarns 102 extending on one side of the uncoupling 106 in the transverse direction DT while the yarns of the second portion of yarns of the plurality of layers of weft yarns 102 extend on the other side of the uncoupling 106 in the transverse direction DT. More specifically, one or more weft yarns 102 binding layers of warp yarns forming a set of yarn layers 108 in the binding zone 105 are used to bind layers of warp yarns forming a set of yarn layers 109 in the binding zones 107 and vice versa. In the example illustrated in [Fig.3], the weft threads T3 and T4, binding layers of threads of . warp 101 of the set of layers of yarns 108 in the first bonding zone 105 are deflected at the beginning or upstream of unbonding 106 in the transverse direction DT to bond layers of warp yarns 101 of the set of layers of yarns 109. Similarly, the weft yarns T5 and T6, bonding layers of warp yarns 101 of the set of layers of yarns 109 in the first bonding zone 105 are deflected at the beginning or upstream of unbonding 106 in the transverse direction DT to bond layers of warp yarns 101 of the set of layers of yarns 108.After the unlinking 106, the weft yarns T3 and T4 are again deflected at the end or downstream of the unlinking 106 in the transverse direction DT, i.e. at their entry into the second binding zone 107, to bind 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 in the transverse direction DT, i.e. at their entry into the second binding zone 107, to bind 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 in the transverse direction DT makes it possible to improve the strength of the fiber blank in the binding zone. unlinking. According to an alternative embodiment, some of the weft threads can cross only upstream or downstream of the unlinking 106 in the transverse direction DT.

[0046] Once the weaving is finished, the non-woven threads present around the fibrous blank 100 are cut to extract the blank and then the foot part of the blank is shaped. In the example described here, the shaping of the foot part 112 is carried out by separating the woven portions 113 and 114 and by introducing an insertion element 130 into the internal housing 140 formed by the uncoupling 106 as illustrated in [Fig. 4]. The insertion element may in particular be made of metallic material or resin by additive manufacturing for example. It may also be made with a salt which can be dissolved after densification.

[0047] A fiber preform 200 is thus obtained comprising, along the longitudinal direction DL, an aerodynamic profile preform portion 211 and a root preform portion 212 having a bulb shape with an internal housing 240 comprising the insertion element 130 as shown in [Fig. 5]. The aerodynamic profile preform portion 211 extending along the transverse direction DT between a leading edge portion 211a and a trailing edge portion 211b.

[0048] The fibrous preform is then densified. The densification of the fibrous preform intended to form the fibrous reinforcement of the part to be manufactured consists of filling the porosity of the preform, in all or part of its volume, with the material constituting the matrix. This densification is carried out in a known manner in itself following the wet process (WSC). The wet process involves impregnating the preform with a liquid composition containing a precursor to 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 sealable mold with a housing in the shape of the final molded blade. The mold is then closed and the liquid matrix precursor (e.g., a resin) is injected throughout the housing to impregnate the entire fiber portion of the preform.

[0049] The transformation of the precursor into a matrix, namely its polymerization, is carried out by heat treatment, generally by heating the mold, after elimination of any solvent and crosslinking of the polymer, the preform being always maintained in the mold having a shape corresponding to that of the part to be produced.

[0050] In the case of the formation of 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, in particular SiC, may be resins of the polycarbosilane (PCS) or polytitanocarbosilane (PTCS) or polysilazane (PSZ) type, while liquid carbon precursors may be resins with a relatively high coke content, such as phenolic resins. Several consecutive cycles, from impregnation to heat treatment, may be carried out to achieve the desired degree of densification.

[0051] According to one aspect of the invention, in the case in particular of the formation of an organic matrix, the densification of the fibrous preform can be carried out by the well-known transfer molding process known as RTM ("Resin Transfer Molding"). 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 which includes the fibrous preform. A pressure gradient is generally established in this internal space between the place where the resin is injected and the orifices for discharging the latter in order to control and optimize the impregnation of the preform by the resin.

[0052] As illustrated in [Fig. 5], the injection of a liquid matrix precursor composition into the fibrous texture as well as its transformation into a matrix are here carried out in an injection tool 300 which comprises a first shell 310 comprising in its center a first imprint 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 imprint 321 corresponding in part to the shape and dimensions of the blade to be produced.

[0053] Once the tool 300 is closed as illustrated in [Fig. 6], the first and second impressions 311 and 321 respectively of the first and second shells 310 and 320 together define an internal volume 301 having the shape of the blade to be produced and in which the fiber preform 200 is placed. A compaction of the fiber preform 200 can be carried out with the closing of the tool 300 in order to obtain a determined fiber rate in the preform. In this case, a compaction pressure is applied to the shells 310 and 320 for example by means of a press. The compaction of the fiber preform can also be carried out in a separate tool before the introduction of the preform into the injection tool.

[0054] The tool 300 further comprises means for carrying out the injection of a liquid matrix precursor and the transformation of this precursor into a matrix. More specifically, in the example described here, the first shell 310 of the tool 300 comprises an injection port 313 intended to allow the injection of a liquid matrix precursor composition into the fiber preform while the second shell comprises an evacuation port 323 intended to cooperate with a pumping system for placing the tool under vacuum and drawing air during injection. The injection tool 300 also comprises a lower part 340 and an upper part 350 between which the first and second shells 310 and 320 are placed, the lower part 340 and the upper part 350 being equipped with heating means (not shown in [Fig. 6]).

[0055] Once the tool 300 is closed, the blade is molded by impregnating the preform 200 with a thermosetting resin that is polymerized by heat treatment. For this purpose, the well-known injection or transfer molding process known as RTM ("Resin Transfer Molding") is used. 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 discharge conduit maintained under pressure (not shown in [Fig. 6]). This configuration allows the establishment of 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 substantially at the level of the lower part of the preform will gradually impregnate the entire preform by circulating in it up to the evacuation port 323 through which the surplus is evacuated. Of course, the first and second shells 310 and 320 of the tooling 300 may respectively comprise several injection ports and several evacuation ports.

[0056] The resin used may be, for example, an epoxy resin with a temperature class of 180°C (maximum temperature tolerated without loss of characteristics). 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 in accordance with the RTM process.

[0057] After injection and polymerization, the blade is demolded. The insert element 130 is then removed so as to obtain a hollow blade root. Finally, the blade is trimmed to remove excess resin and the chamfers are machined. No further machining is necessary since, once the part is molded, it meets the required dimensions.

[0058] The densification processes described above make it possible to produce, from the fiber preform of the invention, mainly propeller blades or vanes made of organic matrix composite material (OMC), carbon matrix composite material (C / C) and ceramic matrix composite material (CMC).

[0059] As illustrated in [Fig.7], a blade 10 is obtained formed from a fibrous reinforcement densified by a matrix which comprises in its lower part a root 12 formed by the root preform portion 212 of the fiber preform 200 and a blade 11 formed by the blade preform portion 211 of the fiber preform 200. The blade 10 comprises a leading edge 11a and a trailing edge 11b corresponding respectively to the leading edge 211a and trailing edge 211b portions of the fiber preform 200. The root 12 comprises a cavity 14 formed by the internal housing 240 of the fiber preform 200, the cavity 14 opening at the free end 12a of the root 12. The blade 10 thus comprises a root 12 which has a compact axisymmetric shape suitable for integration into a system of propeller rotation or pitch change.

[0060] According to an alternative embodiment, the insertion element 130 is retained after demolding. In this case, as illustrated in [Fig. 8], a blade 20 is obtained, formed of a fibrous reinforcement densified by a matrix which comprises in its lower part a root 22 formed by the root 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 comprises a leading edge 21a and a trailing edge 21b corresponding respectively to the leading edge 21a and trailing edge 211b portions of the fibrous preform 200. The root 22 comprises a cavity 24 formed by the internal housing 240 of the fibrous preform 200, the insertion element 130 being glued inside said cavity 24. The blade 20 thus comprises a root 22 which has a compact axisymmetric shape suitable for integration into a rotation system. or change of propeller pitch.

[0061] [Fig.9] illustrates a fiber blade blank 400 according to another method of realization. The fiber blank 400 is produced by 3D weaving under the same conditions as the blank 100 described previously. The fiber blank 400 differs of the fiber blank 100 already described in that the internal foot housing delimited by the uncoupling has an "hourglass" or "diabolo" geometry in which it is not possible to introduce an insertion element of corresponding shape from the only opening present at the free end in the foot part of the fiber blank. For this purpose, a two-part insertion element is used while the fiber blank comprises an additional uncoupling allowing the introduction of one of the two parts of the insertion element.

[0062] More precisely, the fiber blank 400 extends in a longitudinal direction D1, 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 front edge 400a and a rear edge 400b, the blank comprising an aerodynamic profile part 411 defining two faces 411c and 411f intended to form respectively the extrados and intrados faces of the blade and a root part 412 intended to subsequently form a blade root and extending outside the aerodynamic profile blank 411 in the longitudinal direction DL and set back from the front and rear edges 400a and 400b in the transverse direction DT.

[0063] According to the invention, during weaving, a first uncoupling 406 is produced inside the foot portion 412 of the fiber blank 400 between two successive layers of warp threads. The uncoupling 406 extends along a plane parallel to the surface of the fiber blank and over a uncoupling zone delimited by a contour 406a locally separating the foot portion 412 into two woven portions 413 and 414. Furthermore, the uncoupling 406 extends in the transverse direction between a first lateral edge 4120 and a second lateral edge 4121 and set back from these edges so as to maintain connecting portions 405 and 407 adjacent respectively to the first and second lateral edges 4120 and 4121. The uncoupling 406 also opens at the free lower end 4122 of the foot portion 412.

[0064] The width of the uncoupling 406 varies between the free lower end 4122 of the foot portion and the end 4123 of the foot portion opposite the end 4122 in the longitudinal direction DL. The uncoupling 406 here delimits an internal housing 440 which comprises, in the longitudinal direction DL, a first portion 441 whose section decreases between the free end 4122 of the foot portion 412 and an intermediate portion 443 of the internal housing 440 and a second portion 442 whose section increases between the intermediate portion 443 and the aerodynamic profile portion 411. The first portion 441 of the internal housing 440 is accessible via the free lower end 4122.

[0065] An additional disconnection 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 via the passage 450.

[0066] In [Fig. 10], the shaping of the foot part of the fiber blank is carried out by introducing a first part 431 of an insertion element 430 of flared shape into the first portion 441 of the internal housing 440 via the free lower end 4122, on the one hand, and by introducing a second part 432 of the insertion element 430 into the second portion 442 of the internal housing 440 via the passage 450.

[0067] Once the fiber preform has been produced, it is placed in an injection tool in order to form a matrix there as explained in detail previously and which is not described here again for the sake of simplification.

[0068] As illustrated in [Fig. 11], a blade 30 is then obtained, formed from a fibrous reinforcement densified by a matrix which comprises in its lower part a root 32 formed by the root preform part of the fibrous preform and a blade 31 formed by the blade preform part of the fibrous preform. The blade 30 comprises a leading edge 31a and a trailing edge 31b corresponding respectively to the leading edge and trailing edge parts of the fibrous preform.The foot 32 comprises a cavity 34 formed by the internal housing 440 of the fiber preform 400, the cavity 34 comprising the insertion element 430 glued inside said cavity 34, the first part 431 of the flared insertion element 430 being present and glued 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 glued 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 glued at their contact interface. The blade 30 thus comprises a root 32 which has a compact axisymmetric shape suitable for integration into a propeller rotation or pitch change system.

[0069] The shaping of the aerodynamic profile of the fiber blanks described above may comprise the insertion of one or more shaping parts into one or more delinkages made in the aerodynamic profile. The shaping part(s) are preferably made of a lightweight, low-density rigid material such as a rigid honeycomb material.

Claims

Claims

1. Method for manufacturing a turboprop propeller blade or blade (10) made of composite material comprising a fibrous reinforcement densified by a matrix, the method comprising: - producing by three-dimensional weaving a fibrous blank (100) in a single piece, 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 the chord direction of the propeller blade or blade 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),- shaping the fiber blank (100) to obtain a fiber preform (200) in a single piece having said aerodynamic profile portion (111) forming an aerodynamic profile preform (211) and said root portion (112) forming a root preform (212), and - densifying the fiber preform (200) by a matrix to obtain a propeller blade or vane (10) made of composite material having a fiber reinforcement constituted by the fiber preform (200) and densified by the matrix, and forming a single piece with an integrated root (12), characterized in that the root portion (112) of the fiber blank (100) comprises a decoupling (106) delimiting an internal root housing (140) opening at a free end (1122) of said root portion and extending in the longitudinal direction (DL),said delinking extending in the transverse direction between a first lateral edge (1120) and a second lateral edge (1121) and set back from said lateral edges and in that the shaping of the fibrous blank (100) comprises the positioning of at least one insertion element (130) in the internal foot housing (140) so as to form a bulb-shaped foot preform portion (212).,

2. The method of claim 1, wherein densifying the preform comprises placing the fiber preform (200) in an injection tool (300) having the shape of the blade or the propeller blade to be manufactured, the densification further comprising the injection of a resin (360) into the fiber preform held in the injection tool (300), the transformation of the resin into a matrix by heat treatment and the demolding of the blade (10) or the propeller blade, the demolding comprising the removal of said at least one insertion element (130) so as to obtain a hollow root (12).

3. The method of claim 1, wherein the densification of the preform comprises placing the fiber preform (200) in an injection tool (300) having the shape of the blade or propeller blade to be manufactured, the densification further comprising injecting a resin (360) into the fiber preform held in the injection tool (300), transforming the resin into a matrix by heat treatment and demolding the blade or propeller blade so as to obtain a root (22) comprising a cavity (24) with said at least one insertion element (130) glued inside said cavity.

4. Method according to claim 3, in which a lower portion of the aerodynamic profile part (411) of the fiber blank (400) comprises a decoupling (407) delimiting a passage (450) between an edge (400b) of said aerodynamic profile part and the internal foot housing (440), said internal foot housing comprising in the longitudinal direction (DL) a first portion (441) whose section decreases between the free end (4122) of the foot part (412) and an intermediate portion (443) of the housing and a second portion (442) whose section increases between said intermediate portion and the aerodynamic profile part (411), a first portion (431) of the insertion element (430) having a flared shape being positioned in the first portion (441) of the internal foot housing (440),a second portion (432) of the insert element having a flared shape being positioned in the second portion (442) of the internal foot housing via the passage (450) present in the airfoil portion (411).,

5. The method of claim 3 or 4, wherein the insert member (130, 430) is made of one of the following materials: metallic material, resin and salt.

6. Turbopropeller blade or propeller blade (10) made of composite material comprising a fibrous reinforcement densified by a matrix, the blade or the propeller blade comprising, in a span direction (DL), a root (12) and an aerodynamic profile (11), the fiber reinforcement comprising a fiber preform (200) having a three-dimensional weave with a root preform portion (212) present in the root (12) and an aerodynamic profile preform portion (211) present in the aerodynamic profile (11), the root preform and aerodynamic profile preform portions being linked to each other by the three-dimensional weave, characterized in that the root preform portion (212) of the fiber preform (200) comprises a disconnection (106) delimiting an internal root housing (140) forming a cavity (14) opening at a free end (12a) of the root (12), the disconnection extending in a transverse direction between first and second connecting portions (105, 107).

7. A propeller blade or vane (20) according to claim 6, further comprising at least one insert element (130) bonded inside the cavity (24) present in the root (22) of the propeller blade or vane.

8. Propeller blade or vane (30) according to claim 6 or 7, wherein the cavity (34) of the root (32) comprises, in the span direction (DL), a first portion (341) whose section decreases between the free end of the root (32) and an intermediate part of the housing and a second portion (342) whose section 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 vanes according to any one of claims 6 to 8.

10. Aircraft comprising at least one engine according to claim 9.

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