Propeller blade or airfoil with hollow composite root

Abstract

The invention relates to a propeller blade or airfoil (10) for a turboprop engine, made of a composite material and comprising a fibre reinforcement of matrix densification, the propeller blade or airfoil comprising, in a spanwise direction (DL), a root (12) and an aerodynamic profile (11). The fibrous reinforcement comprises a fibrous preform having a three-dimensional weave, the fibrous preform having a root preform portion present in the root (12) and an aerodynamic profile preform portion present in the aerodynamic profile (11), the root and aerodynamic profile preform portions being connected to each other by the three-dimensional weave. The root preform portion of the fiber preform comprises a breach at the junction that delimits a shell inside the root, which shell forms a cavity (14) that opens at the free end (12a) of the root (12).

Description

Technical Field

[0001] The present invention relates to the field of propeller blades or airfoils for aircraft, such as those present on turboprop engines. Background Art

[0002] Propeller blades or airfoils for turboprop engines are usually made of metal materials. Although propeller blades or airfoils of metal materials have good mechanical strength, they have the disadvantage of having a large mass.

[0003] In order to obtain lighter propeller blades or airfoils, it is known to use propeller airfoils in composite materials, ie by producing structural components with fiber reinforcement densified by a matrix.

[0004] Document US 2013 / 0017093 describes the production of a propeller airfoil based on a fiber structure with an aerodynamic profile, inside which is introduced a portion of a spar, one end of which is continued by a bulge intended to form the root of the propeller airfoil.

[0005] New generation engines require more compact blade or airfoil roots. This need arises from the necessity to be able to pivot the blade or airfoil about its vertical axis in order to adapt its angle of attack to the flight mode (variable pitch blade or airfoil). This need, combined with the fact that the blade or airfoil must be integrated as low as possible on the disk, imposes a strong reduction in the volume of the root.

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

[0007] Such axisymmetric or quasi-axisymmetric shapes are more difficult to manufacture in composite materials, particularly when three-dimensional (3D) weaving is used to form the fiber reinforcement of the blade or airfoil.

[0008] Furthermore, the mechanical loads to which the new generation roots are subjected impose additional stresses. In fact, the new generation roots may be integrated into the rotor disk by means of a metal shell, which results in additional mechanical loads in circumferential compression, in addition to the mechanical traction and bending loads normally encountered (caused by centrifugal forces and impact with an object, respectively). Summary of the invention

[0009] It is therefore desirable to be able to propose a solution for producing aircraft propeller blades or airfoils in composite material with a compact root, which are able to resist different mechanical loads.

[0010] To this end, the invention proposes a method for manufacturing a propeller blade or airfoil made of composite material for a turboprop engine, the propeller blade or airfoil comprising fiber reinforcement densified by a matrix, the method comprising:

[0011] - producing, by three-dimensional weaving, a single-piece fiber blank having a flat shape extending in a longitudinal direction and in a transverse direction, the longitudinal direction and the transverse direction respectively corresponding to the span direction and the chord direction of the propeller blade or airfoil 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 the leading edge portion and the trailing edge portion;

[0012] - forming a fiber portion for obtaining a one-piece fiber preform, having an aerodynamic profile portion for forming an aerodynamic profile preform, and said root portion forming a root preform, and

[0013] - densification of the preform with a matrix to obtain a propeller blade or airfoil in composite material with fiber reinforcement consisting of a fiber preform and densified by a matrix and formed into a single piece with an integral root,

[0014] Characterized in that the root portion of the fiber blank includes an unconnected area which defines an internal root recess opening at the free end of the root portion and extends in the longitudinal direction, and characterized in that the forming of the fiber blank includes positioning at least one insert element in the internal root recess so as to form a bulb-shaped root preform portion.

[0015] The method of the invention thus allows the production of a propeller blade or airfoil with a composite root that is both compact and perfectly suited to resisting the different mechanical loads previously described. In fact, the fiber-reinforced portion of the root is produced by 3D weaving and has a bulb shape that is connected to the fiber-reinforced portion of the aerodynamic profile at its center or elsewhere. A composite root is thus obtained that is much more compact than the composite roots of the prior art and that generally extends over the entire width of the lower part of the aerodynamic profile. In this composite root, there are yarns oriented in the span direction of the blade or airfoil, such as warp yarns, which, combined with 3D weaving, give it good mechanical strength in terms of traction and bending. In addition, in the composite root, there are yarns oriented in the chord direction of the blade or airfoil, such as weft yarns, which give it good mechanical strength in circumferential compression.

[0016] Furthermore, the bulb shape allows obtaining a root having an axisymmetric shape or a quasi-axisymmetric shape which is compatible with integration into a propeller rotation or pitch variation system.

[0017] Thus, by creating a fiber reinforcement in which the root portion is integrally formed, ie woven in one piece, with the aerodynamic profile portion, a very good mechanical strength of the component is ensured, in particular at the connection between the root and the aerodynamic profile.

[0018] According to one embodiment of the method according to the invention, the densification of the preform comprises placing the fiber preform into an injection tool having the shape of the propeller blade or airfoil to be manufactured, the densification further comprising injecting a resin into the fiber preform held in the injection tool, converting the resin into a matrix by heat treatment, and removing the propeller blade or airfoil from the mold, the removal from the mold comprising extracting the at least one inserted element so as to obtain a hollow root.

[0019] According to another embodiment of the method according to the invention, the densification of the preform comprises placing the fiber preform into an injection tool having the shape of the propeller blade or airfoil to be manufactured, the densification further comprising injecting a resin into the fiber preform held in the injection tool, converting the resin into a matrix by heat treatment, and removing the propeller blade or airfoil from the mold so as to obtain a root comprising a cavity, wherein the at least one injection element is glued into said cavity.

[0020] According to one aspect of the method of the present invention, the lower part of the aerodynamic profile portion of the fiber blank includes an unconnected area, which defines a channel between one edge of the aerodynamic profile portion and an internal root recess, the internal root recess includes a first part and a second part in the longitudinal direction, the cross-section of the first part decreases between the free end of the root portion and the middle part of the recess, and the cross-section of the second part increases between the middle part and the aerodynamic profile portion, the first part of the insert element with a flared shape is positioned in the first part of the internal root recess, and the second part of the insert element with a flared shape is positioned in the second part of the internal root recess via the channel present in the aerodynamic profile portion.

[0021] According to another aspect of the present invention, the insert element is made of one of the following materials: a metallic material, a resin, and a salt.

[0022] The object of the present invention is also a propeller blade or airfoil of a composite material for a turboprop engine, comprising a fiber reinforcement densified by a matrix, the propeller blade or airfoil comprising a root and an aerodynamic profile in the span direction, the fiber reinforcement comprising a fiber preform with three-dimensional weaving, with a root preform portion present in the root and an aerodynamic preform portion present in the aerodynamic profile, the root and aerodynamic profile preform portions being connected to each other by three-dimensional weaving, characterized in that the root preform portion of the fiber preform comprises an unconnected area defining an internal root recess forming a cavity opening at the free end of the root.

[0023] According to one aspect of the propeller blade or airfoil of the invention, it further comprises at least one insert element which is glued into a cavity present in the root of the propeller blade or airfoil.

[0024] According to one aspect of the propeller blade or airfoil of the present invention, the cavity of the root comprises a first part and a second part in the span direction, the cross-section of the first part decreases between the free end of the root and the middle part of the recess, the cross-section of the second part increases between the middle part and the aerodynamic profile, the first part of the insert element has a flared shape and is present in the first part of the cavity, and the second part of the insert element has a flared shape and is present in the second part of the cavity.

[0025] The invention also covers an aircraft engine comprising a plurality of propeller blades or airfoils according to the invention, and an aircraft comprising at least one such engine. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a schematic diagram showing the 3D weaving of a fiber blank for making a blade,

[0027] Figure 2 is an enlarged scale cross-sectional view of a set of yarn layers in the weft direction, showing the cross-sectional plane II-II. Figure 1 Two unconnected areas are formed in the root portion of the blank.

[0028] Figure 3 is an enlarged scale cross-sectional view of a set of yarn layers in the weft direction, showing the cross-sectional plane III-III. Figure 1 Two unconnected areas are formed in the root portion of the blank.

[0029] Figure 4 is a schematic perspective view showing Figure 1 The fiber blank is formed into a root preform part,

[0030] Figure 5is a schematic exploded perspective view showing an injection tool and the placement of a fiber preform therein according to one embodiment of the present invention,

[0031] Figure 6 is a schematic perspective view showing Figure 5 Closed injection tool,

[0032] Figure 7 is a schematic perspective view of a composite material blade obtained according to one embodiment of the present invention,

[0033] Figure 8 is a schematic perspective view of a blade of a composite material obtained according to another embodiment of the present invention,

[0034] Fig. 9 is a schematic perspective view of a fiber blank according to another embodiment of the present invention,

[0035] Fig.10 is a schematic perspective view showing Fig. 9 The formation of fiber blanks,

[0036] Fig.11 is a schematic perspective view of a blade of a composite material obtained according to another embodiment of the present invention. DETAILED DESCRIPTION

[0037] The invention is generally applicable to different types of propeller blades or airfoils used in aircraft engines. The invention finds advantageous, but not exclusive, application in propeller blades or airfoils of large dimensions intended to be integrated into pivoting or variable pitch systems. Such propeller blades or airfoils are generally provided with a root having a small volume (compact shape) and a good resistance with respect to traction forces, bending forces and circumferential compression forces. The blade according to the invention may in particular constitute a blade for a movable wheel with a shroud (such as a fan blade) or a blade for a movable wheel without a shroud (such as in aircraft engines known as "open rotors").

[0038] In the following description, the exemplary embodiments are described with respect to a blade for a turboprop engine. However, the exemplary embodiments are also applicable to a propeller blade for an aircraft.

[0039] Figure 1 A fiber blank 100 intended to form a fiber preform of a blade to be produced is shown very schematically.

[0040] like Figure 1As schematically shown in FIG. 1 , a fiber structure blank 100 is obtained by three-dimensional (3D) weaving, which is realized in a known manner by means of a jacquard-type loom on which clusters of warp yarns 101 or strands have been arranged, each having multiple layers of several hundred yarns, the warp yarns being connected by weft yarns 102. The fiber structure blank 100 is woven into a single piece, which has a longitudinal direction D corresponding to the span direction of the blade to be manufactured. L , extending between the lower portion 100c and the upper portion 100d, and in the transverse direction D T In the chord direction of the blade to be manufactured, extending between the leading edge 100a and the trailing edge 100b, the blank comprises an aerodynamic profile portion 111 defining two surfaces 111e and 111f intended to form respectively the upper and lower surfaces of the blade, and a root portion 112 intended to subsequently form the root of the blade, and extending in the longitudinal direction D L on the outside of the blank of the aerodynamic profile portion 111 and in the transverse direction D T On the top, it is recessed from the leading edge 100a and the trailing edge 100b.

[0041] In the illustrated embodiment, the 3D weave is an "interlock" weave. Here, an "interlock" weave refers to a weave pattern in which each weft yarn layer connects several layers of warp yarns, and all yarns of the same weft yarn column have the same movement in the plane of the pattern.

[0042] Other known types of three-dimensional weaving may be used, such as those described in particular in document WO 2006 / 136755, the content of which is incorporated herein by reference. This document describes in particular the production of a fiber-reinforced structure for a component such as a blade by weaving the fiber-reinforced structure in a single piece, with a first type of pattern in the core and a second type of pattern in the skin, which allows to give this type of component the desired mechanical and aerodynamic properties.

[0043] The fiber blank according to the invention can in particular be woven from yarns of carbon or ceramic fibers, such as silicon carbide.

[0044] During the weaving process of the fiber blank, its thickness and width vary, without weaving a certain number of warp yarns, which allows defining the desired continuously variable profile and thickness of the blank 100. One embodiment of an evolving 3D weaving is described in document US 2006 / 257260, which in particular allows varying the thickness of the blank between a first edge intended to form the leading edge and a second edge having a smaller thickness and intended to form the trailing edge.

[0045] According to the invention, during weaving, an unconnected area 106 is created in the root portion 112 of the fiber blank 100, between two consecutive layers of warp yarns. The unconnected area 106 extends in a plane parallel to the surface of the fiber blank and over an unconnected area defined by a contour 106a, which locally separates the root portion 112 into two woven portions 113 and 114. Furthermore, the unconnected area 106 extends in the transverse direction between the first lateral edge 1120 and the second lateral edge 1121 and is recessed from these edges (i.e., it does not open onto the lateral edges 1120 and 1121) so as to maintain the connected portions 105 and 107, which are adjacent to the first and second lateral edges 1120 and 1121, respectively. The unconnected area 106 is also open at the lower free end 1122 of the root portion 112. The unconnected region 106 thus forms an inner recess 140 in the root portion 112 , which is accessible from the lower free end 1122 .

[0046] Figure 2 A 3D weaving pattern having an interlocking pattern of a blank 100 is schematically shown. Figure 2 is a partial enlarged view of a warp yarn cross-sectional plane and a portion of the blank 100 including an unconnected area 106 ( Figure 1 In this embodiment, the blank 100 includes a substantially longitudinal direction D L 8 layers of warp yarns 101 extending upward. Figure 2 In the embodiment, the eight layers of warp yarns are connected by weft yarns T1 to T8 in the connecting regions 105 and 107 of the root portion 112 of the fiber blank 100, and the weft yarns are substantially in the transverse direction D. T At the unconnected area 106, the woven portion 113 comprises 4 layers of warp yarns 101 connected together by 4 weft yarns T1 to T4, while the woven portion 114 comprises 4 layers of warp yarns forming the set of yarn layers 109, which are connected by 4 weft yarns T5 to T8.

[0047] In other words, the fact that weft yarns T1 to T4 do not extend into the warp yarn layers of woven portion 114 and that weft yarns T5 to T8 do not extend into the warp yarn layers of woven portion 113 provides an unconnected region 106 separating woven portions 113 and 114 .

[0048] exist Figure 2 In the weaving embodiment presented in , on the one hand, weft yarns T1 to T4, and on the other hand, weft yarns T5 to T8 are arranged respectively on each side of the unconnected area 106, the weft yarns T1 to T4 being connected to form the first layer of the four warp yarns of the woven portion 113, and the weft yarns T5 to T8 being connected to form the last layer of the four warp yarns of the woven portion 114.

[0049] according to Figure 3 The variant embodiment shown in ( Figure 1 Section III-III in the transverse direction D T In the area of ​​the fiber blank 100 located near the unconnected area 106, the first part of the yarns of the weft yarn layer intersects with the second part of the yarns of the weft yarn layer, and the yarns of the first part of the weft yarn 102 extending on one side of the unconnected area are in the transverse direction D. T The second part of the yarns of the layer of the plurality of warp yarns 102 is 106, and the yarns of the second part of the layer of the plurality of warp yarns 102 are oriented in the transverse direction D T More precisely, one or more weft yarns 102 that connect the warp yarn layers in the connection region 105 to form a set of yarn layers 108 are used to connect the warp yarn layers, forming a set of yarn layers 109 in the connection region 107, and vice versa. Figure 3 In the embodiment shown, the weft yarns T3 and T4 of the warp yarn layer 101 connecting the set of yarn layers 108 in the first connecting region 105 are at the beginning or upstream of the unconnected region 106, in the transverse direction D T Similarly, the weft yarns T5 and T6 that connect the warp yarn layers 101 of the group of yarn layers 109 in the first connection area 105 are at the beginning or upstream of the unconnected area 106, in the transverse direction D T The warp yarn layers 101 in the group of yarn layers 108 are deflected in the transverse direction D after the unconnected area 106. T At the end or downstream of the unconnected area 106, i.e., at the entrance to the second connecting area 107, the weft yarns T3 and T4 are deflected again to connect the warp yarn layer 101 in the group of yarn layers 109, while the weft yarns T5 and T6 are deflected in the transverse direction D T At the downstream end of the unconnected area 106, that is, at the entrance to the second connecting area 107, it is deflected again to connect the warp yarn layer 101 of the group of yarn layers 108. T The intersection of weft yarns T3 and T4 with weft yarns T5 and T6 upstream and / or downstream of the unconnected zone 106 allows improving the strength of the fiber blank in the unconnected zone. According to a variant embodiment, a portion of the weft yarns may be connected only in the transverse direction D T The two electrodes intersect each other upstream or downstream of the unconnected region 106 .

[0050] Once the weaving is completed, the non-woven yarns present around the fiber blank 100 are cut away to extract the blank, and then the root portion of the blank is formed. In the embodiment described here, the root portion 112 is formed by separating the woven portions 113 and 114 and by introducing the insert element 130 into the inner recess 140 formed by the unconnected area 106, as shown in FIG. Figure 4 As shown in . For example, by additive manufacturing, the insert element can be produced in particular from a metallic material or a resin. It can also be done with salts that can be dissolved after densification.

[0051] This results in a fiber preform 200 which has a longitudinal direction D L The aerodynamic profile preformed portion 211 and the bulb-shaped root preformed portion 212 are provided on the upper surface. The bulb-shaped root preformed portion 212 has an inner recess 240 and includes an insert element 130, such as Figure 5 The aerodynamic profile preformed portion 211 is formed between the leading edge portion 211a and the trailing edge portion 211b in the lateral direction D T Extend upward.

[0052] The fiber preform is then densified. The densification of a fiber preform intended to form a fiber-reinforced part to be manufactured consists of filling the pores of the whole or part of the volume of the preform with the material constituting the matrix. This densification is achieved in a manner known per se using a liquid path method (CVL). The liquid path method consists of impregnating the preform with a liquid composition comprising a precursor of the matrix material. The precursor is usually in the form of a polymer, such as a high-performance epoxy resin that may be diluted in a solvent. The preform is placed in a mold that can be closed in a sealed manner and that has a recess having the shape of the final molded paddle. The mold is then closed and a liquid matrix precursor (e.g. a resin) is injected into the entire recess to impregnate the entire fiber portion of the preform.

[0053] The conversion of the precursor into a matrix, ie its polymerization, is achieved by thermal treatment, generally by heating the mould, after elimination of possible solvents and polymer crosslinks, the preform always remaining in the mould having a shape corresponding to that of the part to be produced.

[0054] In the case of forming a carbon or ceramic matrix, the thermal treatment consists of pyrolyzing the precursors to transform the matrix into a carbon or ceramic matrix, depending on the precursors used and the pyrolysis conditions. By way of example, the liquid ceramic precursor, in particular for SiC, can be a resin of the polycarbosilane (PCS) type, or polytitanium carbosilane (PTCS) or polysilazane (PSZ), while the liquid carbon precursor can be a resin with a relatively high charring rate, such as a phenolic resin. Several consecutive cycles from impregnation to thermal treatment can be implemented to achieve the desired degree of densification.

[0055] According to one aspect of the invention, in the case of formation of an organic matrix in particular, the densification of the fiber preform can be achieved by a transfer molding method known as RTM ("resin transfer molding"). According to the RTM method, the fiber preform is placed in a mold having the external shape of the part to be produced. A thermosetting resin is injected into the internal volume of the mold, which internal volume includes the fiber preform. A pressure gradient is usually established in this internal volume between the point where the resin is injected and the opening for the discharge of the resin, in order to control and optimize the impregnation of the preform with the resin.

[0056] like Figure 5 As shown, the injection of the liquid matrix precursor composition into the fiber texture and its conversion into the matrix are completed in the injection tool 300, and the injection tool 300 includes a first shell 310 and a second shell 320, the first shell 310 includes a first recess 311 at its center, and the first recess 311 partially corresponds to the shape and size of the blade to be produced, and the second shell 320 includes a second recess 321 at its center, and the second recess 321 partially corresponds to the shape and size of the blade to be produced.

[0057] Once Figure 6 , the first shell 310 and the second shell 320, respectively, with their first recess 311 and second recess 321, together define an inner volume 301 having the shape of the blade to be produced, and the fiber preform 200 is placed in the inner volume. Compacting the preform 200 can be achieved by closing the tool 300 in order to obtain a predetermined fiber content in the preform. In this case, the compacting pressure is applied to the shells 310 and 320, for example, by a press. The compaction of the fiber preform can also be achieved in a separate tool before the preform is introduced into the injection tool.

[0058] The tool 300 also comprises means allowing the injection of a liquid matrix precursor and the conversion of this precursor into a matrix. More precisely, in the embodiment described here, the first housing 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 housing comprises an exhaust port 323 intended to cooperate with a pumping system for placing the tool under vacuum and extracting air during injection. The injection tool 300 also comprises a lower part 340 and an upper part 350, between which the first housing 310 and the second housing 320 are placed, the lower part 340 and the upper part 350 being equipped with heating means ( Figure 6 not shown).

[0059] Once the tool 300 is closed, the molding of the blade is carried out by impregnating the preform 200 with a thermosetting resin that polymerizes during heat treatment. For this purpose, the well-known injection or transfer molding method called RTM ("resin transfer molding") is used. According to the RTM method, a resin 360 (for example a thermosetting resin) is injected into the internal volume occupied by the preform 200 via the injection port 313 of the first housing 310. The port 323 of the second housing 320 is connected to a discharge line ( Figure 6 323). This configuration allows a pressure gradient to be established between the lower portion of the preform 200 where the resin is injected and the upper portion of the preform located near the port 323. In this way, the resin 360 injected substantially in the lower portion of the preform will gradually impregnate the entire preform by circulating inside the preform until the excess is discharged through the discharge port 323. Of course, the first housing 310 and the second housing 320 of the tool 300 may include several injection ports and several discharge ports, respectively.

[0060] For example, the resin may be an epoxy resin of a temperature grade of 180°C (maximum temperature withstood without loss of properties). Resins suitable for the RTM method are well known. They preferably have a low viscosity to facilitate their infusion into the fibers. Depending on the thermomechanical loads to which the component must be subjected, the choice of temperature grade and / or chemical nature of the resin is determined. Once the resin has been injected into the entire reinforcement, its polymerization is carried out by a heat treatment according to the RTM method.

[0061] After injection and polymerization, the blade is removed from the mold. The insert element 130 is then extracted so as to obtain a hollow blade root. Finally, the blade is trimmed to remove excess resin and the chamfers are machined. No other machining is required, since the molded part meets the required dimensions.

[0062] The previously described densification method allows the production of propeller blades or airfoils, mainly of organic-matrix (CMO), carbon-matrix (C / C) and ceramic-matrix (CMC) composite materials, based on the fiber preform of the invention.

[0063] like Figure 7As shown, the blade 10 is obtained by matrix densification fiber reinforcement, which comprises in its lower part a root 12 formed by a root preform portion 212 of a fiber preform 200 and an airfoil 11 formed by an airfoil preform portion 211 of the fiber preform 200. The blade 10 comprises a leading edge 11a and a trailing edge 11b corresponding to the leading edge 211a and the trailing edge 211b of the fiber preform 200, respectively. The root 12 comprises a cavity 14 formed by an internal recess 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 having a compact, axisymmetric shape suitable for integration into a propeller rotation or pitch change system.

[0064] According to a variant embodiment, the insert element 130 is retained after removal from the mold. Figure 8 As shown, a blade 20 is obtained, which is formed by fiber reinforcement through matrix densification, and includes in its lower part a root 22 formed by a root preform portion 212 of a fiber preform 200 and an airfoil 21 formed by an airfoil preform portion 211 of the fiber preform 200. The blade 20 includes a leading edge 21a and a trailing edge 21b corresponding to the leading edge 211a and trailing edge 211b portions of the fiber preform 200, respectively. The root 22 includes a cavity 24 formed by an internal recess 240 of the fiber preform 200, in which the insert element 130 is glued. The blade 20 thus includes a root 22 having a compact, axisymmetric shape suitable for integration into a propeller rotation or pitch change system.

[0065] Fig. 9 A fiber blade blank 400 according to another embodiment is shown. The fiber blank 400 is produced by 3D weaving under the same conditions as the previously described blank 100. The fiber blank 400 differs from the fiber blank 100 already described in that the internal root recess delimited by the unconnected area has an "hourglass" or "hollow top" geometry into which it is not possible to introduce an insert element having a shape that partially corresponds to the only opening at the free end present in the root portion of the fiber blank. For this purpose, an insert element divided into two parts is used, while the fiber blank comprises an additional unconnected area allowing the introduction of one of the two parts of the insert element.

[0066] More precisely, the fiber blank 400 is oriented in the longitudinal direction D corresponding to the span direction of the blade to be manufactured. L on the upper side, extending between the lower portion 400c and the upper portion 400d, and in a transverse direction D corresponding to the chord of the blade to be manufactured. TThe blank comprises an aerodynamic profile portion 411, extending between the leading edge 400a and the trailing edge 400b, which defines two surfaces 411e and 411f intended to form the upper and lower surfaces of the blade, respectively, and a root portion 412 intended to subsequently form the root of the blade and extending in the longitudinal direction D L The aerodynamic profile blank 411 extends inside and in the transverse direction D T The upper edge is recessed from the leading edge 400a and the trailing edge 400b.

[0067] According to the invention, during weaving, between two consecutive layers of warp yarns, a first unconnected area 406 is created inside the root portion 412 of the fiber blank 400. The unconnected area 406 extends in a plane parallel to the surface of the fiber blank and over an unconnected area defined by a contour 406a that locally separates the root portion 412 into two woven portions 413 and 414. Furthermore, the unconnected area 406 extends in the transverse direction between the first lateral edge 4120 and the second lateral edge 4121 and is recessed from these edges so as to keep the connected portions 405 and 407 adjacent to the first lateral edge 4120 and the second lateral edge 4121, respectively. The unconnected area 406 is also open at the lower free end 4122 of the root portion 412.

[0068] The width of the unconnected area 406 is in the longitudinal direction D L The unconnected region 406 defines an inner recess 440 which extends in the longitudinal direction D between a lower free end 4122 of the root portion and an end 4123 of the root portion opposite the end 4122. L The upper portion includes a first portion 441 and a second portion 442, the cross section of the first portion is reduced between the free end 4122 of the root portion 412 and the middle portion 443 of the inner recess 440, and the cross section of the second portion is increased between the middle portion 443 and the aerodynamic profile portion 411. The first portion 441 of the inner recess 440 can be reached from the lower free end 412.

[0069] The additional unconnected area 407 defines a channel 450 between one edge, here the edge 400b of the aerodynamic profile portion 411 and the inner recess 440 in the root portion 412. A second portion 442 of the inner recess 440 is accessible by the channel 450.

[0070] exist Fig.10In the embodiment, the root portion of the fiber blank is formed by, on the one hand, introducing the first portion 431 of the insertion element 430 having a flared shape into the first portion 441 of the internal recess 440 through the lower free end 4122, and on the other hand, introducing the second portion 432 of the insertion element 430 into the second portion 442 of the internal recess 440 through the channel 450.

[0071] Once the fiber preform has been produced in this way, it is placed in an injection tool in order to form a matrix there as explained in detail before and which, for the sake of simplicity, will not be described again here.

[0072] like Fig.11 As shown in , what is then obtained is a blade 30 formed by fiber reinforcement densified by a matrix, which blade comprises in its lower part a root 32 formed by a root preform portion of a fiber preform and an airfoil 31 formed by an airfoil preform portion of a fiber preform. The blade 30 comprises a leading edge 31a and a trailing edge 31b corresponding respectively to the leading edge and trailing edge portions of the fiber preform. The root 32 comprises a cavity 34 formed by an inner shell 440 of the fiber preform 400, the cavity 34 comprising an insert element 430 glued inside said cavity 34, a first portion 431 of the insert element 430 having a flared shape being present and glued in the first portion 341 of the cavity 34, corresponding to the first portion 441 of the inner recess 440, and a second portion 432 of the insert element 430 being present and glued in the second portion 342 of the cavity 34, corresponding to the second portion 442 of the inner recess 440. The first part 431 and the second part 432 of the insert element 430 may also be glued at their contact interface. The blade 30 thus comprises a root 32 having a compact axisymmetric shape suitable for integration into a propeller rotation or pitch variation system.

[0073] The formation of the aerodynamic profile of the fiber blank described previously may include inserting one or more shaped components into the one or more unconnected regions created in the aerodynamic profile. The shaped components are preferably composed of a light rigid material having a low density, such as a rigid honeycomb material.

Claims

1. A method for manufacturing a propeller blade or airfoil (10) made of composite material for a turboprop engine, the propeller blade or airfoil comprising fiber reinforcement densified by a matrix, the method comprising: - producing a single fiber blank (100) by three-dimensional weaving, the fiber blank having a longitudinal direction (D L ) and transverse direction (D T ), the longitudinal direction and the transverse direction respectively corresponding to the span direction and the chord direction of the propeller blade or airfoil to be manufactured, the fiber blank (100) comprising a root portion (112) and an aerodynamic profile portion (111), the aerodynamic profile portion extending in the longitudinal direction (D L ), extending from the root portion and in the transverse direction (D T ), extending between the leading edge portion (100a) and the trailing edge portion (100b), - forming a fiber blank (100) for obtaining a one-piece fiber preform (200), the fiber blank having said aerodynamic profile portion (111) forming an aerodynamic profile preform (211) and said root portion (112) forming a root preform portion (212), and - densification of a fiber preform (200) with a matrix for obtaining a propeller blade or airfoil (10) in composite material with fiber reinforcement consisting of the fiber preform (200) and densified with a matrix and formed into a single piece with an integral root (12), The invention is characterized in that the root portion (112) of the fiber blank (100) comprises an unconnected area (106) defined by an opening at a free end (1122) of the root portion and a longitudinal direction (D L ), the unconnected area extending in a transverse direction between a first lateral edge (1120) and a second lateral edge (1121) and being recessed from the lateral edges, and forming the fiber blank (100) includes positioning at least one insert 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 placing the fiber preform (200) into an injection tool (300) having the shape of the propeller blade or airfoil to be manufactured, the densification also comprising injecting a resin (360) into the fiber preform held in the injection tool (300), converting the resin into a matrix by heat treatment, and removing the propeller blade (10) or airfoil from the mold, the removal from the mold comprising removing the at least one insert element (130) so as to obtain a hollow root (12).

3. The method according to claim 1, wherein: The densification of the preform comprises placing the fiber preform (200) into an injection tool (300) having the shape of the propeller blade or airfoil to be manufactured, the densification also comprising injecting a resin (360) into the fiber preform retained in the injection tool (300), converting the resin into a matrix by heat treatment, and removing the propeller blade or airfoil from the mold so as to obtain a root (22) comprising a cavity (24), wherein at least one insert element (130) is glued into the cavity.

4. The method according to claim 3, wherein: The lower portion of the aerodynamic profile portion (411) of the fiber blank (400) includes an unconnected region (407) defining a channel (450) between one edge (400b) of the aerodynamic profile portion and an internal root recess (440) extending in the longitudinal direction (D L ) comprises a first portion (441) and a second portion (442), wherein the cross-section of the first portion decreases between the free end (4122) of the root portion (412) and the middle portion (443) of the recess, and the cross-section of the second portion increases between the middle portion and the aerodynamic profile portion (411), the first portion (431) having a flared shape of the insert element (430) being positioned in the first portion (441) of the internal root recess (440), and the second portion (432) having a flared shape of the insert element being positioned in the second portion (442) of the internal root recess via a channel (450) present in the aerodynamic profile portion (411).

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

6. A propeller (10) blade or airfoil of a turboprop engine made of composite material, the propeller (10) blade or airfoil comprising fiber reinforcement densified by a matrix, the propeller blade or airfoil having a spanwise direction (D L ) comprises a root (12) and an aerodynamic profile (11), the fiber reinforcement comprises a fiber preform (200) having three-dimensional weaving, the fiber preform having a root preform portion (212) present in the root (12) and an aerodynamic profile portion (211) present in the aerodynamic profile (11), the root preform portion and the aerodynamic profile preform portion being connected to each other by three-dimensional weaving, characterized in that The root preform portion (212) of the fiber preform (200) comprises an unconnected area (106) defining an internal root recess (140) forming a cavity (14) opening at a free end (12a) of the root (12), the unconnected area extending in a transverse direction between the first and second connecting portions (105, 107).

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

8. A propeller blade or airfoil (30) according to claim 6 or 7, wherein: The cavity (34) of the root (32) is shaped in the span direction (D L ) comprises a first portion (341) and a second portion (342), wherein the cross-section of the first portion decreases between the free end of the root (32) and the middle portion of the recess, and the cross-section of the second portion increases between the middle portion and the aerodynamic profile (31), the first portion (431) of the insert element (430) having a flared shape and existing in the first portion (341) of the cavity (34), and the second portion (432) of the insert element having a flared shape and existing in the second portion (342) of the cavity.

9. An aircraft 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.

Images