SHOVEL WITH A FOOT FORMED BY CROSSING WEDGE THREADS

Description

Domaine Technique

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

[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 vanes, it is known to produce blades or vanes from composite material, that is to say by making structural parts with fiber reinforcement densified by a matrix.

[0004] Document FR 3 098 226 A1 describes an example of a fibrous reinforcement structure for a blade made of composite material.

[0005] The new generation of engines requires more compact blade or fan blade mounts. This need stems from the requirement to be able to rotate the blade or fan blade around its vertical axis to adapt its angle of attack to the flight regime. This requirement, combined with the fact that the blade or fan blade must be integrated as low as possible on the rotor disc, necessitates a significant reduction in the overall size of the mount.

[0006] To this end, the roots of the new generation of blades or fan blades have an axisymmetric or nearly axisymmetric shape and reduced dimensions, unlike the roots of prior art such as those described in US documents 2013 / 272893 and US 2013 / 0017093, which extend across the entire width of the lower part of the blade or fan blade. Document FR 3 120 249 A1 describes a fan blade for an unfaired fan.

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

[0008] Furthermore, the mechanical loads to which the new generation of propeller feet are subjected impose additional constraints. Indeed, in addition to the usual tensile and bending loads, which can be caused respectively by centrifugal forces and impacts with objects, these new generation feet can be subjected to significant vibratory bending loads due to the absence of a nacelle around the blade or rotor to control airflow. To counteract this alternating bending moment, the foot is pre-stressed in the hub, which generates an additional circumferential compressive load. Exposé de l'invention

[0009] It is therefore desirable to be able to propose a solution for the production of aircraft propeller blades or blades in composite material capable of withstanding various mechanical loads, particularly at the small-sized base.

[0010] To this end, the present invention proposes a method for manufacturing a 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 between a plurality of warp yarns and a plurality of weft yarns of a one-piece fibrous blank, the fibrous blank having a flat shape in which the warp yarns extend along a longitudinal direction corresponding to the span direction of the blade or propeller blade to be manufactured and in which the weft yarns extend along a transverse direction corresponding to the chord direction of the blade or propeller blade to be manufactured, the fibrous blank comprising an airfoil portion and a root portion intended to form respectively at least a part of the fibrous reinforcement of the airfoil and the root of the blade or propeller blade,the shaping of the fibrous blank to obtain a one-piece fibrous preform comprising an aerodynamic profile preform formed by the aerodynamic profile portion of the fibrous blank and a foot preform formed by the foot portion of the fibrous blank, the densification of the fibrous 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 part of the fibrous blank includes a first unbinding delimiting a first internal housing opening at a free end of said foot part and extending along the longitudinal direction, and in that the foot part includes at least one evolving sub-zone extending from the aerodynamic profile part and in which a plurality of weft yarns located inside the foot part of the fibrous blank cross on either side of the first unbinding along the transverse direction, the number of weft yarns crossing on either side of the first unbinding along the transverse direction in said evolving sub-zone increasing progressively from the aerodynamic profile part towards the free end of the foot part.

[0011] By "weft yarns located inside the foot part" or "internal weft yarns", we mean the weft yarns that are not present on the surface of the foot part of the fibrous blank.

[0012] It is considered that a fibrous blank produced by three-dimensional weaving can include, in a well-known manner, two-dimensional weaving or other weaving structure on its surface, in order to improve its surface condition.

[0013] The weft thread crossing at the base of the fiber blank provides circumferential stiffness to the blade base. This ensures that the blade base is not only resistant to normal tensile and bending stresses, but also to circumferential compression.

[0014] Therefore, the blade will exhibit, on the one hand, a high circumferential stiffness at the foot, which is strongly subjected to circumferential compression, while on the other hand exhibiting a high transverse stiffness at the aerodynamic profile, which is not very subjected to circumferential compression but is exposed to stronger bending and tensile stresses.

[0015] More generally, the continuity of the three-dimensional weave between the foot and the airfoil facilitates the transmission of various forces without creating a mechanically weak interface. Furthermore, by progressively decreasing the number of weft thread crossings as one approaches the airfoil and moves away from the free end of the foot, a smooth transition is ensured between the end of the foot, which will exhibit high circumferential stiffness, and the airfoil, which will exhibit primarily transverse stiffness.

[0016] According to a particular feature of the invention, the foot part further comprises an end sub-zone, extending between the free end of the foot part and the evolving sub-zone, and in which all the internal weft yarns cross on either side of the first unlinking in the transverse direction.

[0017] This weaving method provides great robustness to the blade foot made from the blank, ensuring excellent circumferential stiffness at the foot end, which is most exposed to circumferential compression. The evolving sub-zone also allows for a smoother transition between, on the one hand, the tip sub-zone, where the crossing of all the inner threads results in predominantly circumferential stiffness, and on the other hand, the aerodynamic profile section, where the stiffness is primarily transverse.

[0018] According to a particular feature of the invention, the aerodynamic profile part of the fibrous blank includes a second and a third debonding delimiting a second and a third internal housing opening onto the same edge of the aerodynamic profile part of the blank on either side of the foot part of the fibrous blank along the transverse direction.

[0019] These unbundling mechanisms allow for the insertion of small or lightweight inserts into the blank, resulting in a lighter aerodynamic profile for the blade or propeller blade while maintaining roughly the same mechanical strength. Furthermore, since the loom used to produce the fiber blank cannot create a very thick root or aerodynamic profile, the insert(s) allow for increasing the thickness of the root or aerodynamic profile section without reducing the yarn density in areas subject to high mechanical stress.

[0020] According to a particular feature of the invention, the first unbinding also extends into the aerodynamic profile part of the fibrous blank.

[0021] Thus, the fiber blank includes an internal housing present in both the foot and the airfoil section. Therefore, the insert element(s) inserted by the first unbinding can also increase the thickness of the airfoil section, while maintaining a constant warp / weft ratio and a high volumetric warp yarn content in the area around the insert, which is subject to significant bending stress. Indeed, the loom used to produce the fiber blank does not allow for the creation of a very thick foot or airfoil.

[0022] According to a particular feature of the invention, at most six weft yarns per plane cross on either side of the first unlinking along the transverse direction in the aerodynamic profile portion of the fiber blank. Preferably, only two weft yarns per plane cross on either side of the first unlinking along the transverse direction in the aerodynamic profile portion of the fiber blank.

[0023] Thus, we obtain a blade that allows for a very gradual evolution of the stiffness orientation from the tip to the tip: the stiffness is predominantly circumferential in the blade's root, then hybrid in the lower part of the airfoil which includes the first uncoupling, and finally predominantly transverse in the upper part of the airfoil which does not include the first uncoupling. The transition between the predominantly circumferential stiffness of the root and the predominantly transverse stiffness in the upper part of the airfoil is therefore smoother, with a transition zone in the lower part of the airfoil which contains the first uncoupling.

[0024] According to a particular feature of the invention, the fibrous blank is produced by three-dimensional weaving having an interlock weave.

[0025] The use of a three-dimensional interlock weave further reduces the risk of delamination within the blade or propeller.

[0026] A fibrous blank produced by three-dimensional weaving with an interlock weave is considered to include another weave weave on its surface, for example two-dimensional or multi-satin, in order to improve its surface condition.

[0027] According to another particular feature of the invention, the shaping of the fibrous blank is achieved by inserting an insertion element into each debinding of the fibrous blank.

[0028] The invention further relates to a blade or propeller blade made of composite material comprising a fibrous reinforcement densified by a matrix, the blade or propeller blade having, along a longitudinal direction, a root and an airfoil, and extending along a transverse direction between a leading edge and a trailing edge, the fibrous reinforcement comprising a fibrous preform having a three-dimensional weave in one piece between a plurality of warp yarns extending along the longitudinal direction and a plurality of weft yarns extending along the transverse direction, said fibrous preform comprising a root preform present in the root and an airfoil preform present in the airfoil of the blade or propeller blade,the blade or propeller blade being characterized in that the foot preform of the fibrous preform comprises a first unbinding delimiting a first internal housing forming a cavity opening at a free end of the foot and in that the foot preform comprises at least one evolving portion extending from the airfoil preform and in which a plurality of weft yarns located inside the foot preform cross on either side of the first internal housing along the transverse direction, the number of weft yarns crossing on either side of the first internal housing along the transverse direction in said evolving portion increasing progressively from the airfoil preform towards the free end of the foot preform.

[0029] According to a particular feature of the invention, the foot preform further comprises an end portion, extending between the free end of the foot preform and the evolving portion, and in which all the internal weft threads cross on either side of the first internal housing in the transverse direction.

[0030] According to a particular feature of the invention, the aerodynamic profile preform of the fibrous preform comprises a second and a third debonding delimiting a second and a third internal housing opening onto the same edge of the aerodynamic profile preform on either side of the foot preform along the transverse direction.

[0031] According to another particular feature of the invention, the first internal housing also extends into the aerodynamic profile preform of the fibrous preform.

[0032] According to another particular feature of the invention, at most six weft yarns per plane cross on either side of the first internal pocket along the transverse direction in the aerodynamic profile preform of the fiber preform. Preferably, only two weft yarns per plane cross on either side of the first internal pocket along the transverse direction in the aerodynamic profile preform of the fiber preform. Brève description des dessins

[0033] [ 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 schematic illustration of the zones of the fibrous rudiment of the figure 1 . [ Fig. 3 ] There figure 3 is a schematic view illustrating the weaving of the fibrous rough-out of the figure 2 according to a section plan III-III. [ Fig. 4 ] There figure 4 is a schematic view illustrating the weaving of the fibrous rough-out of the figure 2 according to a section plan IV-IV. [ Fig. 5 ] There figure 5 is a schematic view illustrating the weaving of the fibrous rough-out of the figure 2 according to a VV cutting plan. Fig. 6 ] There figure 6 is a schematic view illustrating the weaving of the fibrous rough-out of the figure 2 according to a section plan VI-VI. [ Fig. 7 ] There figure 7 is a schematic exploded perspective view showing an injection mold and the placement of the fibrous preform obtained from the fibrous blank of the figures 1 à 6 within it according to an embodiment of the invention. Fig. 8 ] There figure 8 is a schematic perspective view showing the injection molding tooling of the figure 7 farm. [ Fig. 9 ] There figure 9 is a schematic cross-sectional view showing a flexible membrane injection mold and the placement of the fibrous preform obtained from the fibrous blank of the figures 1 à 6 inside it in accordance with one embodiment of the invention. Description des modes de réalisation

[0034] The invention is generally applicable to various 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 intended for integration into pivoting or variable-pitch systems.

[0035] Such propeller blades are generally equipped with a base that is both compact and highly resistant to tensile, bending, and circumferential compression stresses. The blade according to the invention can, in particular, serve as a blade for unfaired rotating wheels, such as those found in so-called "open rotor" aircraft engines.

[0036] In the following description, embodiment examples are described in relation to turboprop turbine blades. However, these embodiment examples also apply to aircraft propeller blades.

[0037] There figure 1 shows very schematically a fibrous rough 100 intended to form the fibrous preform 1 of the blade to be produced.

[0038] 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 rough fibrous structure 100 is woven in one piece, the rough extending in a longitudinal direction DL, corresponding to the span direction of the blade to be manufactured, 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.

[0039] The blank 100 comprises a portion of the airfoil 111 intended to subsequently form part of the airfoil of the blade and defining a first face 111e and a second face 111f intended to form respectively the upper and lower surfaces of the blade. Thus, the portion of the airfoil 111 extends in the longitudinal direction DL between a lower edge 100c and an upper edge 100d.

[0040] The fibrous blank 100 further comprises a foot portion 112 intended to subsequently form part of the blade foot, and extending outside the airfoil portion 111 along the longitudinal direction DL to a lower edge 102c and set back from the leading and trailing edges 100a and 100b along the transverse direction DT. The lower edge 102c of the foot portion 112 corresponds to a free end of said foot portion 112.

[0041] Preferably, as in the illustrated example, the 3D weave is an "interlock" weave. By "interlock" weave, we mean a weave 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 within the plane of the weave.

[0042] Other known three-dimensional weaving types may be used, such as those described in document WO 2006 / 136755. 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.

[0043] The fiber blank 100 may comprise a plurality of fibers of various types, in particular ceramic or carbon fibers, or a mixture of such fibers. Preferably, the fiber blank 100 may be made from silicon carbide fibers. In general, the fiber blank 100 may also be made from fibers composed of the following materials: alumina, mullite, silica, an aluminosilicate, a borosilicate, carbon, or a mixture of several of these materials.

[0044] As the fiber blank 100, whose thickness and width vary, is woven, a certain number of warp yarns are not woven. This allows the desired, continuously variable contour and thickness of the blank 100 to be defined. An example of an evolving 3D weave, which notably allows the thickness of the blank 100 to be varied between a first edge intended to form the leading edge and a second, thinner edge intended to form the trailing edge, is described in US document 2006 / 257260. Preferably, the thickness of the trailing or leading edge is reduced by removing layers of weft yarns from within the fiber blank, rather than from the outside, in order to maintain continuity of the wefts located on the surface of the fiber blank.Thus, the final blade will include a fibrous reinforcement with a more satisfactory flexural stiffness in the transverse direction DT and therefore more favorable in case of impact, for example in case of bird strike.

[0045] According to the invention, during weaving, a first unbonding 120 is made at least within the foot portion 112 of the fiber blank 100. Preferably, three unbondings are made within the fiber blank 100. Indeed, a second unbonding 110 is made within the airfoil portion 111 of the fiber blank 100, and a third unbonding 130 is made within the airfoil portion 111 of the fiber blank 100. The three unbondings 110, 120, and 130 extend along a plane parallel to the surface of the blank 100. The second unbonding 110 and the third unbonding 130 made within the airfoil portion 111 are located on either side of the foot portion 112. other than the first unlinking 120 made at least inside the foot part 112.Thus, the second link 110, the first link 120 and the third link 130 are arranged in this order along the transverse direction DT.

[0046] The first debonding 120 extends into the fibrous blank 100 over a first debonding zone delimited by a contour 120a. Thus, the first debonding 120 extends into the foot portion 112 over at least a first portion of the second debonding zone delimited by the contour 120a. The first debonding 120 thus extends through the foot portion 112 of the blank 100.

[0047] In the foot part 112 of the blank 100, the first joint 120 extends along the transverse direction DT between the front edge 100a and the rear edge 100b. Preferably, the first joint 120 extends back from the front and rear edges 100a and 100b, that is to say, the first joint 120 does not open onto the front and rear edges 100a and 100b.

[0048] In the foot section 112 of the blank 100, the first joint 120 extends along the longitudinal direction DL between the lower edge 100c of the airfoil section 111 and the lower edge 102c of the foot section, and terminates at the lower edge 102c of the foot section. The first joint 120 may extend back from the lower edge 100c of the airfoil section 111, that is, it may not terminate in the airfoil section 111 of the blank 100.

[0049] However, preferably, the first debond 120 also extends into the airfoil part 111 of the blank 100. Thus, the first debond 120 extends into the airfoil part 111 over a second portion of the first debond zone delimited by the contour 120a.

[0050] In this case, in the airfoil section 111, the first joint 120 extends along the transverse direction DT between the leading edge 100a and the trailing edge 100b. Preferably, the first joint 120 extends back from the leading and trailing edges 100a and 100b, meaning that the first joint 120 does not open onto the leading and trailing edges 100a and 100b. Of course, it remains within the scope of the invention if the first joint 120 opens onto the leading edge 100a and / or the trailing edge 100b. Furthermore, in the airfoil section 111, the first joint 120 extends along the longitudinal direction DL between the lower edge 100c and the upper edge 100d. The first delinking 120 obviously leads to the said lower edge 100c, in order to lead into the foot part 112.Preferably, the first debond 120 extends along the longitudinal direction DL set back from the upper edge 100d, that is to say that the first debond 120 does not open onto the upper edge 100d.

[0051] Thus, the first debonding 120 locally separates the foot portion 112 into two woven sections 112a and 112b arranged on either side of the first debonding 120 along the thickness direction of the blank 100, that is, along the direction perpendicular to the transverse DT and longitudinal DL directions, as illustrated in the figure 3 In the illustrated example, the first debond 120 locally separates the aerodynamic profile portion 111 into a fifth woven portion 114a and a sixth woven portion 114b arranged on either side of the first debond 120 along the thickness direction of the blank 100, that is, along the direction perpendicular to the transverse DT and longitudinal DL directions, as illustrated in the figure 5 .

[0052] The second debonding 110 extends into the aerodynamic profile part 111 over a second debonding zone delimited by a contour 110a. The debonding 110 thus locally separates the aerodynamic profile part 111 into a first woven portion, comprising a part of the first face 111e intended to form the extrados face, and a second woven portion, comprising a part of the second face 111f intended to form the intrados face.

[0053] The second joint 110 extends along the transverse direction DT between the front edge 100a and the rear edge 100b, and is set back from the rear edge 100b; that is, the second joint 110 does not open onto the rear edge 100b. Preferably, the second joint 110 extends along the transverse direction DT, set back from the front edge 100a; that is, the second joint 110 does not open onto the front edge 100a. Preferably, every point belonging to the second joint 110 is closer to the front edge 100a than to the rear edge 100b along the transverse direction DT.

[0054] In the airfoil section 111, the second joint 110 extends along the longitudinal direction DL between the lower edge 100c and the upper edge 100d. The second joint 110 opens onto said lower edge 100c, the second joint 110 opening onto said lower edge 100c between the leading edge 100a and the junction between the root section 112 and the airfoil section 111. Preferably, the second joint 110 extends along the longitudinal direction DL set back from the upper edge 100d, that is to say, the first joint 110 does not open onto the upper edge 100d.

[0055] Thus, the second debond 110 locally separates the aerodynamic profile part 111 into two woven portions 111a and 111b arranged on either side of the second debond 110 along the thickness direction of the blank 100, that is to say along the direction perpendicular to the transverse DT and longitudinal DL directions.

[0056] The third debonding 130 extends into the aerodynamic profile part 111 over a third debonding zone delimited by a contour 130a. The debonding 130 thus locally separates the aerodynamic profile part 111 into the first woven portion, comprising a part of the first face 111e intended to form the extrados face, and the second woven portion, comprising a part of the second face 111f intended to form the intrados face.

[0057] The third connection 130 extends along the transverse direction DT between the front edge 100a and the rear edge 100b, and is set back from the front edge 100a; that is, the third connection 130 does not open onto the front edge 100a. Preferably, the third connection 130 extends along the transverse direction DT, set back from the rear edge 100b; that is, the third connection 130 does not open onto the rear edge 100b. Preferably, every point belonging to the third connection 130 is closer to the rear edge 100b than to the front edge 100a along the transverse direction DT.

[0058] In the airfoil section 111, the third joint 130 extends along the longitudinal direction DL between the lower edge 100c and the upper edge 100d. The third joint 130 opens onto said lower edge 100c, the third joint 130 opening onto said lower edge 100c between the rear edge 100b and the junction between the foot section 112 and the airfoil section 111. Preferably, the third joint 130 extends along the longitudinal direction DL set back from the upper edge 100d, that is to say, the joint 110 does not open onto the upper edge 100d.

[0059] Thus, the third debond 130 locally separates the aerodynamic profile portion 111 into two woven sections 113a and 113b arranged on either side of the third debond 130 along the thickness direction of the blank 100, that is, along the direction perpendicular to the transverse DT and longitudinal DL directions, as illustrated in the figure 5 .

[0060] Preferably, in the aerodynamic profile part 111, the second debond 110 and the third debond 130 extend over a greater length along the longitudinal direction DL than the first debond 120.

[0061] The fibrous blank 100 is thus composed of several successive zones extending across the entire width of the fibrous blank 100 along the transverse direction DT and succeeding one another along the longitudinal direction DL, as illustrated in the figure 2 .

[0062] The first zone Z1 of the fiber blank 100 corresponds to the area of ​​the foot part 112 of the fiber blank 100. The first zone Z1 thus extends across the entire width of the foot part 112 of the fiber blank 100 along the transverse direction DT, and extends between the lower edge 102c of the foot part 112 and the lower edge 100c of the airfoil part 111. Thus, the first zone Z1 has only the first unbond 120 as its sole unbond.

[0063] The first zone Z1 comprises a first subzone Z1a, called the "end subzone," which includes the free end of the foot section 112; that is, the first subzone Z1a extends from the lower edge 102c of the foot section 112. The first zone Z1 also comprises a second subzone Z1b, called the "evolving subzone," which extends from the lower edge 100c of the airfoil section 111. Preferably, the first subzone Z1a and the second subzone Z1b are adjacent and follow each other along the longitudinal direction DL. Preferably, this occurs when the foot section 112 has an hourglass shape as illustrated in the figure 2 , the section of smallest thickness of said hourglass, which corresponds to the neck of the foot of the dawn 112, makes the delimitation between the first sub-zone Z1a and the second sub-zone Z1b.

[0064] The second zone Z2 corresponds to the area of ​​the airfoil section 111 containing the three bonds 110, 120, and 130, in the case where the first bond 120 also extends into the airfoil section 111. The second zone Z2 thus extends across the entire width of the airfoil section 111 of the fiber blank 100 along the transverse direction DT, and extends from the lower edge 100c of the airfoil section 111. Therefore, if it exists, the second zone Z2 includes the second bond 110, the first bond 120, and the third bond 130, as illustrated in the figure. figure 2 .

[0065] The third zone Z3 of the fiber blank 100 corresponds to the area of ​​the blade airfoil section 111 in which two bonds are present, if this area exists. Preferably, the third zone corresponds to the area of ​​the blade airfoil section 111 in which the second bond 110 and the third bond 130 are present, as illustrated in the example of the figure 2 the first debond 120 not extending beyond the first zone Z1 or the second zone Z2. We do not, of course, depart from the scope of the invention if the third zone Z3 corresponds to the area of ​​the aerodynamic profile part of the blade 111 in which the second debond 110 and the first debond 120 are present, or the first debond 120 and the third debond 130, if this area exists.

[0066] The fourth zone Z4 of the fiber blank 100 corresponds to the area of ​​the airfoil portion of the blade 111 in which there is only one unbond, if such an area exists. Preferably, the fiber blank 100 does not include a fourth zone Z4, as is the case in the example of the figure 2 If the fibrous blank 100 includes a fourth zone Z4, the fourth zone Z4 includes the second debond 110 or the third debond 130. However, we do not depart from the scope of the invention if the fourth zone Z4 corresponds to the area of ​​the aerodynamic profile part of the blade 111 in which only the first debond 120 is present, if this area exists.

[0067] The fifth zone Z5 of the fiber blank 100 corresponds to the area of ​​the airfoil portion of the blade 111 that does not include a debond. The fifth zone Z5 thus extends across the entire width of the airfoil portion of the fiber blank 100 along the transverse direction DT, and extends to the upper edge 100d of the airfoil portion 111.

[0068] A 3D interlock weave method of the first draft 100 according to the invention is shown schematically on the figures 3 à 6 The number of schematic weft threads is reduced for the sake of simplifying the figures.

[0069] There figure 3 is a partial enlarged view of a cross-sectional plane in the first sub-zone Z1a of the first zone Z1 of the fibrous rough 100 (section III-III on the figure 2 ). In this example, the fiber blank 100 comprises 8 layers of warp yarns 101 extending substantially in the longitudinal direction DL. The 8 layers of warp yarns 101 are linked by weft yarns T1 to T8 in the linking zones 115 and 125 of the foot portion 112 of the fiber blank 100, the weft yarns T1 to T8 extending substantially in the transverse direction DT.

[0070] The eight layers of warp yarns 101 are arranged in a first set 108 of layers and a second set 109 of layers. These first and second sets 109 are positioned on either side of the first unlinking 120 along the thickness direction, that is, perpendicular to the transverse DT and longitudinal DL directions. Thus, the first woven portion 112a of the foot section 112 comprises a portion of the first set 108 of warp yarns, and the second woven portion 112b of the foot section 112 comprises a portion of the second set 109 of warp yarns. The first and second sets 108 and second sets 109 of layers of warp yarns join at the linking zones 115 and 125.

[0071] As illustrated on the figure 3 In the first sub-zone Z1a of the first zone Z1, all the inner weft yarn layers T2 to T7 cross over each other on either side of the first unlinking 120 in the transverse direction. Conversely, the outer weft yarn layers T1, T8, that is, those located on the surface of the fiber blank 100, do not cross over other weft yarn layers, in order to ensure a better surface finish. Of course, the invention remains within the scope of practice if all the weft yarn layers, both inner and outer, cross over each other on either side of the first unlinking 120 in the transverse direction.

[0072] Thus, in the first sub-zone Z1a of the first zone Z1, each inner weft yarn crosses the other weft yarns in the first bonding zone 115 and in the second bonding zone 125. All the inner weft yarns are therefore deflected at the beginning or upstream of the first unbinding 120 along the transverse direction DT, and then deflected again at the exit or downstream of the first unbinding 120 along the transverse direction DT. Thus, the weft yarn layers T2 to T4 bind the first set 108 of warp yarns 101 in the first bonding zone 115, then bind the second set 109 of warp yarns 101 in the second woven portion 112b, and finally bind the first set 108 of warp yarns 101 in the second bonding zone 125.Conversely, the weft yarn layers T 5 to T 7 bind the second set 109 of warp yarns 101 in the first bonding zone 115, then bind the first set 108 of warp yarns 101 in the first woven portion 112a and finally bind the second set 109 of warp yarns 101 in the second bonding zone 125.

[0073] Such a crossing of the weft threads in the foot part 112 improves the holding of the fibrous rough 100 around the first unbinding 120, and subsequently allows to confer excellent circumferential stiffness to the foot of the blade.

[0074] The first zone Z1 also includes the second sub-zone Z1b, which extends from the lower edge 100c of the airfoil section 111. This second sub-zone Z1b allows for a transition between, on the one hand, the first sub-zone Z1a, in which all the internal weft threads cross, and on the other hand, the airfoil section, in which the percentage of crossing weft threads is very low. Thus, the second sub-zone Z1b exhibits a progressive weft thread crossing percentage on either side of the first unlinking 120, following the longitudinal direction DL. More precisely, the second sub-zone Z1b exhibits a weft thread crossing percentage that gradually decreases from the first sub-zone Z1a of the foot section 112 to the airfoil section 111. This avoids an abrupt transition between the foot section 112 and the airfoil section 111.Consequently, the resulting blade exhibits a gradual change in stiffness orientation between the root and the airfoil: the stiffness is strongly circumferential at the tip of the blade root, then becomes less and less circumferential and increasingly transverse as one approaches the airfoil. However, the stiffness of the blade root remains more circumferential and less transverse than that of the airfoil. The transition between the predominantly circumferential stiffness at the root tip and the predominantly transverse stiffness in the upper part of the airfoil is therefore smoother.

[0075] There figure 4 is a partial enlarged view of a cross-sectional plane in the second sub-zone Z1b of the first zone Z1 of the fibrous rough 100 (section IV-IV on the figure 2 ). In the second sub-zone Z1b of the first zone Z1, the 8 layers of warp yarns 101 are linked by weft yarns T t1 to T t8 in the linking zones 115 and 125 of the foot part 112 of the fibrous rough 100, the weft yarns T t1 to T t8 extending substantially in the transverse direction DT.

[0076] As illustrated on the figure 4 In the second sub-zone Z1b of the first zone Z1, only a portion of the inner weft yarn layers Tt2 to Tt7 cross over each other on either side of the first unlinking 120 in the transverse direction. The outer weft yarn layers Tt1 and Tt8, i.e., those located on the surface of the fiber blank 100, do not cross over other weft yarn layers, in order to ensure a better surface finish.

[0077] Thus, in the second sub-zone Z1b of the first zone Z1, only a percentage of internal weft wires cross the other weft wires in the first link zone 115 and in the second link zone 125. Only a percentage of the internal weft wires is therefore deflected at the beginning or upstream of the first unlink 120 along the transverse direction DT, and then deflected again at the exit or downstream of the first unlink 120 along the transverse direction DT.

[0078] Thus, the weft yarn layers Tt3 and Tt4 bind the first set 108 of warp yarns 101 in the first bonding zone 115, then bind the second set 109 of warp yarns 101 in the second woven portion 112b, and finally bind the first set 108 of warp yarns 101 in the second bonding zone 125. Conversely, the weft yarn layers Tt5 and Tt6 bind the second set 109 of warp yarns 101 in the first bonding zone 115, then bind the first set 108 of warp yarns 101 in the first woven portion 112a, and finally bind the second set 109 of warp yarns 101 in the second bonding zone 125. In the example illustrated on the figure 4 For the sake of simplifying the figures, only four weft threads cross on either side of the first unlinking 120. Preferably, more weft threads cross on either side of the first unlinking 120 to ensure sufficient circumferential stiffness in the future blade foot.

[0079] Preferably, in the second sub-zone Z1b of the first zone Z1, the percentage of inner weft threads crossing on either side of the first unlinking 120 varies progressively from 100% at the junction with the first sub-zone Z1a to between 5% and 30% at the junction with the aerodynamic profile part 111.

[0080] There figure 5 is a partial enlarged view of a cross-sectional plane in the second zone Z2 of the fibrous rough 100 (section VV on the figure 2 ). In the second zone Z2, the 8 layers of warp yarns 101 are linked by weft yarns T 11 to T 18 in the bonding zones 105, 115, 125 and 135 of the aerodynamic profile part 111 of the fibrous blank 100, the weft yarns T 11 to T 18 extending substantially in the transverse direction DT.

[0081] The first set 108 and the second set 109 of warp yarn layers 101 are arranged on either side of the second unlinking 110, the first unlinking 120 and the third unlinking 130 along the thickness direction, that is to say along the direction perpendicular to the transverse DT and longitudinal DL directions.

[0082] Thus, the first woven portion 111a, the third woven portion 113a, and the fifth woven portion 114a of the airfoil section 111 each comprise a portion of the first set 108 of warp yarns 101, and the second woven portion 111b, the fourth woven portion 113b, and the sixth woven portion 114b of the airfoil section 111 each comprise a portion of the second set 109 of warp yarns. The first set 108 and the second set 109 of layers of warp yarns 101 join at the bonding zones 105, 115, 125, and 135.

[0083] The first bond zone 115 separates the second bond 110 from the first bond 120. The second bond zone 125 separates the first bond 120 from the third bond 130. The third bond zone 105 includes a portion of the leading edge 100a. The fourth bond zone 135 includes a portion of the trailing edge 100b. Thus, the third bond zone 105, the second bond 110, the first bond zone 115, the first bond 120, the second bond zone 125, the third bond 130, and the fourth bond zone 135 follow one another in that order along the transverse direction DT in the second zone Z2.

[0084] As illustrated on the figure 5 , only two weft wires T14, T15 per plane cross, these two wires being located at the core of the aerodynamic profile part 111 and crossing the aerodynamic profile part 111 substantially along the transverse direction DT along the boundaries of the first, second and third unlinkage 110, 120, 130. Preferably, six weft wires at most per plane cross in the second zone Z2, preferably along the boundaries of the first, second and third unlinkage 110, 120, 130.

[0085] In the example shown on the figure 5 For the sake of simplicity, the space between each unlinking point 110, 120, 130 is very small. Preferably, a larger space can be maintained between each unlinking point 110, 120, 130 to allow for proper three-dimensional weaving of the fibers. Additional wefts can be inserted into these spaces between unlinking points 110, 120, 130 to compensate for the lack of thickness caused by the absence of unlinking.

[0086] Thus, in the second zone Z2, the two weft wires T14 and T15 cross at least in the first bond zone 115 and in the second bond zone 125. Preferably, the two weft wires T14 and T15 also cross in the third bond zone 105 and in the fourth bond zone 135, as illustrated in the example of the figure 5 . The two weft threads T 14 , T 15 are therefore deflected at the beginning or upstream of the first unlink 120 along the transverse direction DT , then deflected again at the exit or downstream of the first unlink 120 along the transverse direction DT .

[0087] Thus, the weft yarns T 11 to T 13 bind the first set 108 of warp yarns 101 across the entire width of the airfoil section 111 along the transverse direction DT. The weft yarns T 11 to T 13 therefore bind the first set 108 of warp yarns 101 in the third bonding zone 105, in the first woven section 111a, in the first bonding zone 115, in the fifth woven section 114a, in the second bonding zone 125, in the third woven section 113a and in the fourth bonding zone 135.

[0088] Conversely, the weft yarns T 16 to T 18 bind the second set 109 of warp yarns 101 across the entire width of the aerodynamic profile section 111 along the transverse direction DT. The weft yarns T 16 to T 18 therefore bind the second set 109 of warp yarns 101 in the third bonding zone 105, in the second woven section 111b, in the first bonding zone 115, in the sixth woven section 114b, in the second bonding zone 125, in the fourth woven section 113b and in the fourth bonding zone 135.

[0089] Such a partial crossing of the weft yarns in the lower part of the aerodynamic profile section 111 improves the holding of the fibrous blank 100 around the three unbonds 110, 120 and 130, and subsequently allows to confer a smooth transition between the circumferential stiffness of the foot of the blade and the transverse stiffness of the top of the aerodynamic profile, by proposing a hybrid stiffness between circumferential and transverse.

[0090] There figure 6 is a partial enlarged view of a cross-sectional plane in the third zone Z3 of the fibrous rough 100 (section VI-VI on the figure 2 ). In the third zone Z3, the 8 layers of warp yarns 101 are linked by weft yarns T 21 to T 28 in the bonding zones 105, 115, 125 and 135 of the aerodynamic profile part 111 of the fibrous blank 100, the weft yarns T 21 to T 28 extending substantially in the transverse direction DT.

[0091] The first set 108 and the second set 109 of warp yarn layers 101 are arranged on either side of the second unlinking 110 and the third unlinking 130 along the thickness direction, that is to say along the direction perpendicular to the transverse DT and longitudinal DL directions.

[0092] Thus, the first woven portion 111a and the third woven portion 113a of the airfoil section 111 each comprise a portion of the first set 108 of warp yarns 101, and the second woven portion 111b and the fourth woven portion 113b of the airfoil section 111 each comprise a portion of the second set 109 of warp yarns. The first set 108 and the second set 109 of layers of warp yarns 101 join at the bonding zones 105, 115, 125, and 135.

[0093] The third link zone 105, the second link 110, the common zone of the first and second link zones 115 and 125, the third link 130 and the fourth link zone 135 follow each other in this order according to the transverse direction DT in the third zone Z3.

[0094] As illustrated on the figure 6 Preferably, only two weft wires T 24, T 25 per plane cross, these two wires being located at the core of the aerodynamic profile part 111 and crossing the aerodynamic profile part 111 substantially along the transverse direction DT along the boundaries of the second and third unlinkage 110 and 130. Preferably, at most six weft wires per plane cross in the third zone Z3, preferably along the boundaries of the second and third unlinkage 110 and 130.

[0095] Thus, in the third zone Z3, the two weft threads T14, T15 preferably cross in the third unlinking zone 105, twice in the common zone of the first and second linking zones 115 and 125, and in the fourth linking zone 135, as illustrated on the figure 6 .

[0096] The two weft threads T 24, T 25 are therefore deflected at the beginning or upstream of the second unlink 110 along the transverse direction DT, then deflected again at the exit or downstream of the second unlink 110 along the transverse direction DT, then deflected at the beginning or upstream of the third unlink 130 along the transverse direction DT, then deflected again at the exit or downstream of the third unlink 130 along the transverse direction DT.

[0097] Thus, the weft yarns T 21 to T 23 bind the first set 108 of warp yarns 101 across the entire width of the airfoil section 111 along the transverse direction DT. The weft yarns T 21 to T 23 therefore bind the first set 108 of warp yarns 101 in the third bonding zone 105, in the first woven section 111a, in the first and second bonding zones 115 and 125, in the third woven section 113a and in the fourth bonding zone 135.

[0098] Conversely, the weft yarns T 26 to T 28 bind the second set 109 of warp yarns 101 across the entire width of the aerodynamic profile section 111 along the transverse direction DT. The weft yarns T 26 to T 28 therefore bind the second set 109 of warp yarns 101 in the third bonding zone 105, in the second woven section 111b, in the first and second bonding zones 115 and 125, in the fourth woven section 113b and in the fourth bonding zone 135.

[0099] Such a partial crossing of the weft threads in the intermediate part of the aerodynamic profile part 111 improves the holding of the fibrous rough 100 around the two unbonds 110 and 130, and subsequently allows to confer an even smoother transition between the circumferential stiffness of the foot of the blade and the transverse stiffness of the top of the aerodynamic profile, by proposing a hybrid stiffness between circumferential and transverse.

[0100] In the fifth zone Z5, we find a classic three-dimensional weave which consequently presents a predominantly transverse stiffness.

[0101] Once the weaving is complete, the non-woven yarns surrounding the fiber blank 100 are cut to extract the blank. The second, first, and third unbindings 110, 120, 130 respectively form a second, first, and third internal compartments within the first fiber blank 100, extending into the first fiber blank 100.

[0102] To form the fibrous preform 1 of the blade to be produced, the fibrous blank 100 is shaped. Thus, the aerodynamic profile part 111 of the fibrous blank 100 is shaped to form an aerodynamic profile preform 11 of the preform 1, and the foot part 112 of the fibrous blank 100 is shaped to form a foot preform 12 of the preform 1.

[0103] Preferably, the shaping of the fiber blank 100 is carried out by inserting at least one first insertion element 20 into the first debonding 120. Preferably, one or more second and third insertion elements 10, 30 can also be inserted respectively through the second and third debondings 110, 130 into the aerodynamic profile portion 111 of the fiber blank 100. These insertion elements 10, 20, 30 can be intended to form part of the final part, or to be intended to be removed after the densification operation of the fiber preform 1.

[0104] The insert elements 10, 20, 30 can be made of foam or have at least a partial lattice structure. The insert elements 10, 20, 30 can also be made at least partially of a fugitive material, that is, a material that can be removed mechanically, chemically, or thermally.

[0105] The insert elements 10, 20, and 30 are preferably made of a non-structural material. These insert elements, which may be intended to form part of the final blade, have a lower density than the density of the matrix-densified fibrous blank in the final blade. The insert elements 10, 20, and 30 may be made of foam, for example, polyurethane. The insert elements 10, 20, and 30 may also be honeycomb-shaped.

[0106] The insertion elements 10, 20, 30 can be made of the same material. At least one of the insertion elements 10, 20, 30 can be made of a different material than another of the insertion elements 10, 20, 30. Preferably, the second and third insertion elements 10, 30 intended to be inserted into the second and third disjunctions 110, 130 are made of the same material, and the first insertion element 20 intended to be inserted into the first disjunction 120 is made of a different material.

[0107] The aerodynamic profile preform of the resulting fibrous preform 1 generally exhibits the shape of the final blade's aerodynamic profile. A compaction step can be performed on the fibrous preform 1, for example, to vary its thickness along the longitudinal direction.

[0108] The next step is to densify the fibrous preform 1, which was prepared as described previously. The densification of the fibrous preform 1, 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.

[0109] Densification can be achieved using a method known per se via the liquid-liquid process (LLP). The LLP 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 to match the final molded blade. The mold is then closed, and the liquid matrix precursor (e.g., a resin) is injected into the entire cavity to impregnate all the fibrous material of the preform.

[0110] 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.

[0111] 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.

[0112] 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.

[0113] As illustrated on the figures 7 And 8, the injection of a liquid matrix precursor composition into the fibrous preform and its transformation into a matrix are here carried out in an injection tool 60 which includes a first shell 61 comprising in its center a first impression 61a corresponding in part to the shape and dimensions of the blade to be produced and a second shell 62 comprising in its center a second impression 62a corresponding in part to the shape and dimensions of the blade to be produced.

[0114] Once the tool 60 is closed as illustrated on the figure 8 The first and second impressions 61a and 62a of the first and second molds 61 and 62, respectively, together define an internal volume having the shape of the blade to be produced, and in which the fiber preform 1 is placed. The fiber preform can be compacted with the tooling 60 closed to obtain a specific fiber content within the preform. In this case, compaction pressure is applied to the molds 61 and 62, for example, using a press. The fiber preform can also be compacted in a separate mold before being fed into the injection mold.

[0115] The tooling 60 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 61 of the tooling 60 includes an injection port 61e for injecting a liquid matrix precursor composition into the fibrous preform, while the second shell includes a discharge port 62s for cooperating with a pumping system to evacuate the tooling and draw air during injection. The injection tooling 60 also includes a lower portion 63 and an upper portion 64 between which the first and second shells 61 and 62 are placed, the lower portion 63 and the upper portion 64 being equipped with heating means (not shown in the figure). figure 8 ).

[0116] Once the tooling 60 is closed, the blade is molded by impregnating the preform 1 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, for example a thermosetting resin, is injected through the injection port 61e of the first shell 61 into the internal volume occupied by the preform 1. The port 62s of the second shell 62 is connected to a pressurized discharge conduit (not shown in the figure). figure 8 This configuration establishes a pressure gradient between the lower part of preform 1, where the resin is injected, and the upper part of preform 1, located near port 62s. In this way, the resin injected at approximately the lower part of preform 1 will progressively permeate the entire preform, circulating within it until it reaches the discharge port 62s, through which the excess resin is evacuated. Naturally, the first and second shells 61 and 62 of the tooling 60 can each include several injection ports and several discharge ports, respectively.

[0117] 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.

[0118] The densification of the fibrous preform can also be achieved in a well-known manner by injection under a membrane, as illustrated in the figure 9This injection method allows for complete control of the amount of resin or slurry injected, thus ensuring a precise and appropriate fiber content. Consequently, the mechanical properties of the manufactured part are improved, with low variability from one part to another.

[0119] The fibrous preform 1 is placed in a mold 70, which includes on the one hand an impregnation chamber 71 in which the fibrous preform is placed in order to be densified by a matrix by the injection of an impregnation fluid through the injection ports 71a, and on the other hand a compaction chamber 72 in which a compression fluid is injected through the injection ports 72a in order to apply pressure to the fibrous preform 1 during its densification by the matrix. The impregnation chamber 71 and the compaction chamber 72 are separated by a flexible membrane 73. The membrane 73 allows pressure to be applied to the fibrous preform 1 installed in the impregnation chamber 71, the compression fluid applying a pressure P on the membrane 73 which deforms and thus in turn applies a pressure to the fibrous preform 1. The flexible membrane 73 is for example made of silicone.

[0120] Depending on the size, thickness and shape of the blade or propeller blade to be manufactured, a different injection sequence of compression and impregnation fluids will be preferred.

[0121] For example, one can begin by injecting the impregnation fluid, such as a resin, into the impregnation chamber where the fibrous preform is placed. Once the impregnation fluid injection is complete, the compression fluid, such as water, is injected into the compaction chamber to exert pressure on the flexible membrane. The flexible membrane then applies pressure to the fibrous preform, allowing the impregnation fluid to penetrate it.

[0122] The preform is then subjected to heat treatment while the pressure exerted by the membrane is maintained, in order to form a matrix in the porosities of the fibrous preform.

[0123] In another example, the compression fluid can be injected into the compaction chamber first. Thus, even before the impregnation fluid is injected, pressure is already applied to the fibrous preform via the flexible membrane, at a value that achieves the desired fiber volume percentage. The impregnation fluid is then injected, and this can be done while the compression fluid continues to be injected to compensate for pressure losses, particularly when the impregnation fluid is a slurry. Such an injection sequence is described, for example, in document WO 2019 / 197757 A1.

[0124] After injection and polymerization, the blade is demolded.

[0125] Preferably, the first insert element(s) 20 are removed to obtain a hollow blade root. The second and third insert elements 10, 30 can also be removed to obtain a blade aerodynamic profile that is at least partially hollow. If insert elements made of fugacious material were inserted into the fibrous preform, they can be removed during resin polymerization, or during or after demolding of the blade. Finally, one or more insert elements 10, 20, 30 can be retained in the blade.

[0126] A trimming or machining step can be carried out on the part produced to obtain the blade or propeller blade to be made.

[0127] The densification processes described above make it possible to produce, from the fibrous preforms of the invention, mainly blades or propeller blades in organic matrix composite material (CMO), carbon matrix (C / C) and ceramic matrix (CMC).

Claims

1. A method for manufacturing a propeller blade or vane made of composite material comprising a fibrous reinforcement densified by a matrix, the method comprising: - making a single-piece fibrous blank (100) by three-dimensional weaving between a plurality of warp yarns (101) and a plurality of weft yarns (102), the fibrous blank (100) having a flat shape in which the warp yarns (101) extend along a longitudinal direction (DL) corresponding to the span direction of the propeller blade or vane to be manufactured and wherein the weft yarns (102) extend along a transverse direction (DT) corresponding to the chord direction of the propeller blade or vane to be manufactured, the fibrous blank (100) comprising an airfoil part (111) and a root part (112) intended to form respectively at least part of the fibrous reinforcement of the airfoil and of the root of the propeller blade or vane, - shaping the fibrous blank (100) to obtain a single-piece fibrous preform (1) comprising an airfoil preform formed by the airfoil part (111) of the fibrous blank (100) and a root preform formed by the root part (112) of the fibrous blank (100), - densifying the fibrous preform (1) by a matrix to obtain a propeller blade or vane made of composite material having a fibrous reinforcement constituted by the fibrous preform (1) and densified by the matrix, and forming a single piece with an integrated root, characterized in that the root part (112) of the fibrous blank (100) comprises a first non-interlinking (120) delimiting a first inner housing opening out at a free end (102c) of said root part (112) and extending along the longitudinal direction (DL), and in that the root part (112) includes at least one changing sub-area (Z1b) extending from the airfoil part (111) and wherein a plurality of weft yarns (Tt3, Tt4, Tt5, Tt6) located inside the root part (112) of the fibrous blank (100) cross on either side of the first non-interlinking (120) along the transverse direction (DT), the number of weft yarns crossing on either side of the first non-interlinking (120) along the transverse direction (DT) in said changing sub-area (Z1b) increasing gradually from the airfoil part (111) to the free end (102c) of the root part (112).

2. The manufacturing method according to claim 1, wherein the root part (112) further includes an end sub-area (Z1a) extending between the free end (102c) of the root part (112) and the changing sub-area (Z1b) and wherein all of the internal weft yarns (T2, T3, T4, T5, T6, T7) cross on either side of the first non-interlinking (120) along the transverse direction (DT).

3. The manufacturing method according to claim 1 or 2, wherein the airfoil part (111) of the fibrous blank (100) comprises a second and a third non-interlinking (110, 130) delimiting a second and a third inner housing opening out onto the same edge of the airfoil part (111) of the blank (100) on either side of the root part (112) of the fibrous blank (100) along the transverse direction (DT).

4. The manufacturing method according to any one of claims 1 to 3, wherein the first non-interlinking (120) also extends into the airfoil part (111) of the fibrous blank (100).

5. The manufacturing method according to claim 4, wherein at most six weft yarns (T14, T15) per plane cross on either side of the first non-interlinking (120) along the transverse direction (DT) in the airfoil part (111) of the fibrous blank (100).

6. The manufacturing method according to claim 5, wherein only two weft yarns (T14, T15) per plane cross on either side of the first non-interlinking (120) along the transverse direction (DT) in the airfoil part (111) of the fibrous blank (100).

7. The manufacturing method according to any one of claims 1 to 6, wherein the fibrous blank (100) is made by three-dimensional weaving having an interlock weave.

8. The manufacturing method according to any one of claims 1 to 7, wherein the shaping of the fibrous blank (100) is carried out by inserting an insertion element (10, 20, 30) into each non-interlinking (110, 120, 130) of the fibrous blank (100).

9. A propeller blade or vane made of composite material comprising a fibrous reinforcement densified by a matrix, the propeller blade or vane including, along a longitudinal direction (DL), a root and an airfoil, and extending along a transverse direction (DT) between a leading edge and a trailing edge, the fibrous reinforcement comprising a fibrous preform (1) having a three-dimensional weaving in a single piece between a plurality of warp yarns (101) extending along the longitudinal direction (DL) and a plurality of weft yarns (102) extending along the transverse direction (DT), said fibrous preform (1) comprising a root preform present in the root and an airfoil preform present in the airfoil of the propeller blade or vane, characterized in that the root preform of the fibrous preform (1) comprises a first non-interlinking (120) delimiting a first inner housing forming a cavity opening out at a free end of the root and in that the root preform includes at least one changing portion extending from the airfoil preform and wherein a plurality of weft yarns (Tt3, Tt4, Tt5, Tt6) located inside the root preform cross on either side of the first inner housing along the transverse direction (DT), the number of weft yarns crossing on either side of the first inner housing along the transverse direction (DT) in said changing portion increasing gradually from the airfoil preform to the free end of the root preform.

10. The propeller blade or vane according to claim 9, wherein the root preform further includes an end portion extending between the free end of the root preform and the changing portion and wherein all of the internal weft yarns (T2, T3, T4, T5, T6, T7) cross on either side of the first inner housing along the transverse direction (DT).

11. The propeller blade or vane according to claim 9 or 10, wherein the airfoil preform of the fibrous preform (1) comprises a second and a third non-interlinking (110, 130) delimiting a second and a third inner housing opening out onto the same edge of the airfoil preform on either side of the root preform along the transverse direction (DT).

12. The propeller blade or vane according to any one of claims 9 to 11, wherein the first inner housing also extends into the airfoil preform of the fibrous preform (1).

13. The propeller blade or vane according to claim 12, wherein at most six weft yarns (T14, T15) per plane cross on either side of the first inner housing along the transverse direction (DT) in the airfoil preform of the fibrous preform (1).

14. The propeller blade or vane according to claim 13, wherein only two weft yarns (T14, T15) per plane cross on either side of the first inner housing along the transverse direction (DT) in the airfoil preform of the fibrous preform (1).