PROPELLER BLADE OR SHOVEL WITH HOLLOW COMPOSITE FOOT

Description

Technical Field

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

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

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

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

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

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

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

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

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

[0010] To this end, the present invention proposes a method for manufacturing a turboprop propeller blade or blade from a composite material comprising a fibrous reinforcement densified by a matrix, the method comprising: the production by three-dimensional weaving of a one-piece fibrous blank, the fibrous blank having a flat shape extending along a longitudinal direction and a transverse direction corresponding respectively to the span direction between a lower part and an upper part and to the chord direction of the blade or propeller blade to be manufactured, the fibrous blank comprising a root portion and an airfoil portion extending along the longitudinal direction from the root portion and along the transverse direction between a leading edge portion and a trailing edge portion, the shaping of the fibrous blank to obtain a one-piece fibrous preform having said airfoil portion forming the airfoil preform and said root portion forming the root preform,and the densification of the fibrous preform by a matrix to obtain an intermediate part in composite material having a fibrous reinforcement consisting of the fibrous preform and densified by the matrix, the intermediate part comprising an aerodynamic profile part and a foot part, , characterized in that the foot portion of the fiber blank comprises a debonding delimiting an internal housing extending both into the foot portion and into the airfoil portion of the fiber blank, the internal housing opening at a lower part of the fiber blank, in that the shaping of the fiber blank comprises the insertion of a spar into the internal housing, the spar comprising an airfoil shaping portion positioned in the airfoil portion of the fiber blank and a foot shaping portion positioned in the foot portion of the fiber blank so as to form respectively an airfoil preform portion and a foot preform portion, and in that the method further comprises, after the densification step,a machining step of the foot portion of the intermediate part made of composite material along a determined radius so as to form a blade or propeller blade comprising a foot having a shape of revolution and an aerodynamic profile.

[0011] The process of the invention thus makes it possible to produce a propeller blade or blade with a composite base that is both compact and perfectly adapted to withstand the various mechanical loads described above. Indeed, the fibrous reinforcement portion of the base is made using 3D weaving and has a shape of revolution that is connected to the fibrous reinforcement portion of the airfoil at its center. This results in a composite base that is much more compact than that of the prior art, which generally extends across the entire width of the lower part of the airfoil. Within this composite base, there are threads, for example warp threads, oriented in the span direction of the blade or blade, which, in combination with the 3D weave, gives it good tensile and flexural strength.In addition, in the composite foot there are threads, for example weft threads, oriented in the direction of the chord of the blade or vane which gives it good mechanical resistance in circumferential compression.

[0012] Furthermore, the revolutionary shape of the foot is compatible with integration into a system for rotating or changing the helix pitch.

[0013] By inserting a spar into the fibrous reinforcement, in which a foot portion is integrally formed—that is, woven in one piece—with an aerodynamic profile portion, very good mechanical strength is ensured for the entire component, particularly with respect to the stresses to which the foot may be subjected. According to one aspect of the invention, the debonding present in the foot portion of the fibrous blank and the foot portion of the spar have, in the transverse direction, a width greater than the machining radius of the foot portion of the intermediate composite material component. This allows the entire spar to pass through the foot portion of the fibrous blank. According to another aspect of the invention, the spar is made of a composite material comprising a fibrous reinforcement densified by a matrix or of a metallic material.

[0014] According to another aspect of the process of the invention, the shaping of the fibrous blank further includes the insertion of a shaping piece made of rigid, honeycomb material around the aerodynamic profile shaping portion of the spar.

[0015] According to another aspect of the process of the invention, the shaping of the fibrous blank further includes the injection of an expansive material around the aerodynamic profile conformation portion of the spar.

[0016] The invention also relates to a turboprop propeller blade or blade made of composite material comprising a fibrous reinforcement densified by a matrix, the propeller blade or blade having, along a span direction, a root and an airfoil, the root and the airfoil extending along a chord direction between a leading edge and a trailing edge, the fibrous reinforcement comprising a fibrous preform having a three-dimensional weave with a portion of the root preform present in the root and a portion of the airfoil preform present in the airfoil, the portions of the root preform and the airfoil being linked to each other by the three-dimensional weave, characterized in that the fibrous preform includes a debonding delimiting an internal housing opening at the level of the portion of the root preform, the housing forming a cavity extending both in the root and in the airfoil,in that a spar is present in the cavity, the spar comprising a portion of the aerodynamic profile shape positioned in a first portion of the cavity and a portion of the root shape positioned in a second portion of the cavity, and in that the root of the blade or propeller blade has a shape of revolution.

[0017] According to one aspect of the blade or propeller blade of the invention, the foot conformation portion of the spar is exposed at the leading edge and trailing edge of the blade or propeller blade foot, the rest of the foot conformation portion of the spar being covered by the fibrous preform.

[0018] According to another aspect of the blade or propeller blade of the invention, the spar is made of composite material comprising a fibrous reinforcement densified by a matrix or of metallic material.

[0019] The invention further covers an aircraft engine comprising a plurality of blades or propeller blades according to the invention and an aircraft comprising at least one such engine. Brief description of the drawings

[0020] [ Fig. 1 ] There figure 1 is a schematic view illustrating the 3D weaving of a fibrous blank for the manufacture of a blade, [ Fig. 2 ] There figure 2 is a cross-sectional view in the weft direction at an enlarged scale of a set of yarn layers showing the formation of a debond in the toe portion of the rough figure 1 according to a section plan II-II, [ Fig. 3 ] There figure 3 is a schematic perspective view showing the shaping of a portion of the foot preform and a portion of the airfoil preform in the fibrous roughing of the figure 1 , [ Fig. 4 ] There figure 4 is a schematic exploded perspective view showing an injection mold and the placement of the fibrous preform inside it according to an embodiment of the invention, [ Fig. 5 ] There figure 5 is a schematic perspective view showing the injection molding tooling of the figure 4 farm, [ Fig. 6 ] There figure 6 is a schematic perspective view of an intermediate part made of composite material obtained according to an embodiment of the invention, [ Fig. 7 ] There figure 7 is a schematic perspective view of a composite material blade obtained after machining the foot part of the intermediate piece of the figure 6 . Description of the implementation methods

[0021] The invention is generally applicable to various types of propeller blades used in aircraft engines. The invention finds advantageous, but not exclusive, application in large propeller blades intended for integration into pivoting or variable-pitch systems. Such propeller blades are generally equipped with a cylindrical root, i.e., a root with a shape of revolution, and good resistance to tensile, bending, and circumferential compression forces. The blade according to the invention can, in particular, constitute a blade for shrouded rotating wheels such as fan blades or a blade for unshrouded rotating wheels as in so-called "open rotor" aircraft engines.

[0022] In the following description, embodiment examples are described in relation to turboprop turbine blades. However, these embodiment examples also apply to aircraft propeller blades.

[0023] There figure 1 shows very schematically a fibrous rough 100 intended to form the fibrous preform of a blade to be produced.

[0024] The initial fibrous structure 100 is obtained, as schematically illustrated on the figure 1 , by three-dimensional (3D) weaving carried out in a known manner using a jacquard type loom on which a bundle of warp yarns 101 or strands has been arranged in a plurality of layers of several hundred yarns each, the warp yarns being linked by weft yarns 102.The fiber structure blank 100 is woven in one piece, the blank extending in a longitudinal direction DL, corresponding to the span direction of the blade to be manufactured, between a lower part 100c and an upper part 100d and in a transverse direction DT, corresponding to the chord direction of the blade to be manufactured between a front edge 100a and a rear edge 100b, the blank comprising an aerodynamic profile part 111 defining two faces 111e and 111f intended to form respectively the extrados and intrados faces of the blade and a foot part 112 intended to subsequently form a blade foot and extending outside the aerodynamic profile blank 111 along the longitudinal direction DL and set back from the front and rear edges 100a and 100b along the transverse direction DT."Three-dimensional weaving" or "3D weaving" refers to a weaving method in which at least some of the warp threads interlock with weft threads across multiple weft layers, such as an "interlock weave." An "interlock" weave, in this context, refers to a weave structure in which each layer of weft threads interlocks with multiple layers of warp threads, with all threads in the same weft column having the same movement within the plane of the weave.

[0025] 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.

[0026] The fibrous blank according to the invention can be woven in particular from carbon fiber yarns or ceramic such as silicon carbide.

[0027] As the fibrous blank, whose thickness and width vary, is woven, a certain number of warp threads are not woven, which makes it possible to define the desired contour and thickness, continuously variable, of the blank 100. An example of evolving 3D weaving, allowing in particular the variation of the thickness of the blank between a first edge intended to form the leading edge and a second edge of lesser thickness intended to form the trailing edge, is described in document US 2006 / 257260.

[0028] According to the invention, during weaving, a debinding 106 is made inside the fibrous rough 100 between two successive layers of warp yarns. The debonding 106 extends along a plane parallel to the surface of the fiber blank and over a debonding zone delimited by a contour 106a, locally separating the fiber blank 100 into two woven portions 113 and 114. In the longitudinal direction DL, the debonding 106 crosses the foot portion 112 of the fiber blank 100 and partially penetrates the airfoil portion 111 of the fiber blank 100. Furthermore, the debonding 106 extends in the transverse direction DT between the leading edge 100a and the trailing edge 100b of the blank 100 and set back from these edges; that is, the debonding 106 does not extend onto the leading edge 100a and trailing edge 100b so as to maintain bonding portions 105 and 107 adjacent respectively to the front edge 100a and the rear edge 100b.The junction 106 also opens at the lower part 100c. The junction 106 thus forms an internal housing 140 which is accessible from the lower part 100c.

[0029] A 3D interlock weave pattern of the 100 draft is shown schematically by the figure 2 . There figure 2 is a partial enlarged view of a cross-sectional plane in a portion of the rough 100 including the unbonding zone 106 (section II-II on the figure 1 ). In this example, the blank 100 comprises 8 layers of warp yarns 101 extending substantially in the longitudinal direction DL. On the figure 2 The 8 layers of warp yarns are linked by weft yarns T1 to T8 in the linking zones 105 and 107 of the fibrous blank 100, the weft yarns extending substantially in the transverse direction DT. At the linking zone 106, the woven portion 113 comprises 4 layers of warp yarns 101 linked together by 4 weft yarns T1 to T4, while the woven portion 114 comprises the 4 layers of warp yarns forming the set of yarn layers 109, which are linked by 4 weft yarns T5 to T8.

[0030] In other words, the fact that the weft yarns T 1 to T 4 do not extend into the warp yarn layers of the woven portion 114 and that the weft yarns T 5 to T 8 do not extend into the warp yarn layers of the woven portion 113 ensures the unbinding 106 which separates the woven portions 113 and 114.

[0031] Once the weaving is complete, the non-woven yarns surrounding the fibrous blank 100 are cut to extract the blank, and then the foot portion of the blank is shaped. In the example described here, the shaping of the foot portion 112 is carried out by separating the woven sections 113 and 114 and inserting a stringer 130 into the internal recess 140 formed by the unbundling 106, as illustrated in the figure. figure 3 The spar 130 includes a portion of the airfoil shape 131 which is positioned in an upper or bottom part 140a of the housing 140 present in the airfoil part 111 of the fiber blank 100. The spar 130 also includes a portion of the foot shape 132 which is positioned in a lower or beginning part 140b of the housing 140 present in the foot part 112 of the fiber blank 100. The housing 140 extends at its lower part 140b and along the transverse direction DT over a width l 140 which is greater than the final diameter of the blade or propeller blade root to be produced as explained below. The width l 140 corresponds to the width l 106 of the joint 106 in the fiber blank 100 ( figure 1 ). Such a width is necessary to allow the passage of the aerodynamic profile conformation portion 111 through the lower part 140b of the housing 140. The foot conformation portion 132 of the spar 130 has an elongated shape along the transverse direction DT in order to adapt to the width l 140 of the housing in the lower part 140b of the housing in particular in order to control the maintenance of the shape of the preform in the injection tooling.

[0032] The 130 spar can be made from various materials. In particular, it can be made from a composite material comprising a fibrous reinforcement obtained by three-dimensional weaving or by stacking two-dimensional fiber plies and densified by a matrix. The spar can also be made from a metallic material.

[0033] In the example described here, a conformation part 150 made of rigid honeycomb material such as rigid foam is positioned around the aerodynamic profile conformation portion 131 of the spar.

[0034] This yields a fibrous preform 200 comprising, along the longitudinal direction DL, a portion of the aerodynamic profile preform 211 and a portion of the foot preform 212 having a bulged shape with an internal housing 240 comprising the spar 130 as shown in the figure 4 . The preform portion of the aerodynamic profile 211 extending along the transverse direction DT between a leading edge portion 211a and a trailing edge portion 211b.

[0035] The next step is to densify the fibrous preform. Densifying the fibrous preform, intended to form the fibrous reinforcement of the part to be manufactured, involves filling the preform's porosity, throughout all or part of its volume, with the matrix material. This densification is carried out using a well-known liquid-based process (CVL). The liquid-based process involves impregnating the preform with a liquid composition containing a precursor of the matrix material. The precursor is usually in the form of a polymer, such as a high-performance epoxy resin, possibly diluted in a solvent. The preform is placed in a mold that can be sealed tightly with a cavity shaped like the final molded blade. The mold is then closed, and the liquid matrix precursor (for example, a resin) is injected into the entire cavity to impregnate the entire fibrous portion of the preform.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] As illustrated on the figure 4 , the injection of a liquid matrix precursor composition into the fibrous texture and its transformation into a matrix are here carried out in an injection tool 300 which includes a first shell 310 comprising in its center a first impression 311 corresponding in part to the shape and dimensions of the blade to be produced and a second shell 320 comprising in its center a second impression 321 corresponding in part to the shape and dimensions of the blade to be produced.

[0040] Once the 300 tool is closed as illustrated on the figure 5 The first and second impressions 311 and 321 of the first and second molds 310 and 320, respectively, together define an internal volume 301 having the shape of the blade to be produced, and in which the fiber preform 200 is placed. The fiber preform 200 can be compacted with the tooling 300 closed to obtain a specific fiber content in the preform. In this case, compaction pressure is applied to the molds 310 and 320, for example, using a press. The fiber preform can also be compacted in a separate mold before being introduced into the injection mold.

[0041] The tooling 300 further includes means for injecting a liquid matrix precursor and transforming this precursor into a matrix. More specifically, in the example described here, the first shell 310 of the tooling 300 includes an injection port 313 for injecting a liquid matrix precursor composition into the fibrous preform, while the second shell includes a discharge port 323 for cooperating with a pumping system for evacuating the tooling and drawing air during injection. The injection tooling 300 also includes a lower portion 340 and an upper portion 350 between which the first and second shells 310 and 320 are placed, the lower portion 340 and the upper portion 350 being equipped with heating means (not shown in the figure). figure 5 ).

[0042] Once the tooling 300 is closed, the blade is molded by impregnating the preform 200 with a thermosetting resin, which is then polymerized by heat treatment. This is done using the well-known injection or transfer molding process known as RTM ("Resin Transfer Molding"). According to the RTM process, a resin 360, for example a thermosetting resin, is injected through the injection port 313 of the first shell 310 into the internal volume occupied by the preform 200. The port 323 of the second shell 320 is connected to a pressurized discharge conduit (not shown in the diagram). figure 6 This configuration establishes a pressure gradient between the lower part of the preform 200, where the resin is injected, and the upper part of the preform, located near port 323. In this way, the resin 360, injected at approximately the lower part of the preform, will progressively permeate the entire preform as it circulates through it until it reaches the discharge port 323, through which the excess resin is evacuated. Naturally, the first and second shells 310 and 320 of the tooling 300 can each include several injection ports and several discharge ports, respectively. The RTM process can also be performed under vacuum (VA-RTM).

[0043] The resin used can be, for example, a temperature-class epoxy resin with a resistance to temperature (RTM) of 180°C. Resins suitable for RTM processes are well-established. They preferably have a low viscosity to facilitate their injection into the fibers. The choice of temperature class and / or the chemical composition 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.

[0044] The densification processes described above make it possible to produce, from the fibrous preform of the invention, mainly blades or propeller blades in organic matrix composite material (CMO), carbon matrix (C / C) and ceramic matrix (CMC).

[0045] After injection, polymerization, and demolding, the result is as illustrated in the figure 6 , an intermediate piece of composite material 20 having a fibrous reinforcement consisting of the fibrous preform 200 and densified by the matrix, the intermediate piece 20 comprising an aerodynamic profile part 21 and a foot part 22.

[0046] The foot portion 22 of the intermediate composite material part 20 is then machined according to a determined radius RU, which defines a machining contour CU in order to form a foot with a shape of revolution. The foot portion 22 is therefore machined to remove the material outside the machining contour CU and to form a foot with a shape of revolution. This can be seen on the figure 6 that part of the foot conformation portion 132 of the spar 130 extends beyond the machining contour CU. The machining therefore consists here of removing the part of the densified fibrous preform present outside the machining contour CU as well as the part of the foot conformation portion 132 of the spar 130 also present outside the contour CU.

[0047] Finally, the blade is trimmed to remove excess resin and the chamfers are machined. No further machining is necessary since, as the part is molded, it meets the required dimensions.

[0048] As illustrated on the figure 7 , we obtain a blade 10 formed of a fibrous reinforcement densified by a matrix which has in its lower part a foot 12 formed by the machined part of the foot preform 212 and a blade 11 formed by the part of the blade preform 211 of the fibrous preform 200. The blade 10 has a leading edge 11a and a trailing edge 11b corresponding respectively to the leading edge parts 211a and trailing edge parts 211b of the fibrous preform 200.The foot 12 includes a cavity 14 formed by the internal housing 240 of the fibrous preform 200, the cavity 14 including the spar 130 bonded inside said cavity 14, the aerodynamic profile conformation portion 131 of the spar 130 being present and bonded in a first portion 142 of the cavity 14 corresponding to the upper part 140a of the housing 140 present in the aerodynamic profile portion 111 of the fibrous blank 100 while the foot conformation portion 132 of the spar 130 is present and bonded in a second portion 141 of the cavity 14 corresponding to the lower part 140b of the housing 140 present in the foot portion 112 of the fibrous blank 100.

[0049] As can be seen on the figure 7The foot portion 132 of the spar 13 is exposed at the leading edge 12a and trailing edge 12b of the blade or propeller blade root 12, the remainder of the foot portion of the spar being covered by the densified fibrous preform. This partial exposure of the spar at the blade or propeller blade root results from machining the foot portion 22 of the intermediate part 20 to a diameter smaller than the excess width of the decoupling 106 at the level of the portion of the fibrous blank 100 intended to form the blade or propeller blade root. However, thanks to the elongated shape of the foot portion 132 of the spar 130, most of the outer perimeter of the foot 12 is formed by the foot preform portion 212 of the fibrous preform 200.By retaining most of the fibrous reinforcement on the outer perimeter of the foot 12, the strength of the blade or propeller blade is improved in this area, which is subjected to significant bending stresses due to the aerodynamic loads on the blade or propeller blade. Since the fibrous reinforcement has a continuous three-dimensional weave from the foot to the aerodynamic profile's apex, it is perfectly suited to transferring local stresses to the rest of the blade or propeller blade, thus increasing its mechanical strength.

[0050] In the example described above, a rigid, honeycomb-shaped molding piece is positioned around the airfoil portion of the spar. The use of such a molding piece is optional, however, as the spar can be shaped to fill the entire volume of the internal cavity within the airfoil section. Using an additional rigid, honeycomb-shaped molding piece reduces the overall mass of the blade or propeller blade. Alternatively, the molding piece can be fabricated in situ around the airfoil portion by injecting an expansive material. In this case, solvable fillers such as salt nuclei are temporarily positioned within the fibrous preform before the matrix injection.Once the intermediate piece is made, that is, after densification of the fibrous preform, the filling elements are removed and an expansive material is injected into the freed volume.

Claims

1. A method for manufacturing a propeller blade or airfoil (10) for a turboprop engine made from composite material comprising a matrix-densified fibrous reinforcement, the method comprising: - producing a fibrous blank (100) in a single piece by three-dimensional weaving, the fibrous blank having a flat shape extending in a longitudinal direction (DL) and a transverse direction (DT) respectively corresponding to the direction of its span between a lower portion (100c) and an upper portion (100d) and in the chord direction of the propeller blade or airfoil to be manufactured, the fibrous blank (100) comprising a root portion (112) and an aerodynamic profile portion (111) extending in the longitudinal direction (DL) from the root portion and in the transverse direction (DT) between a leading-edge portion (100a) and a trailing-edge portion (100b), - the shaping of the fibrous blank (100) to obtain a single-piece fibrous preform (200) having said aerodynamic profile portion (111) forming an aerodynamic profile preform (211) and said root portion (112) forming a root preform (212), and - the densification of the fibrous preform (200) by a matrix to obtain an intermediate part made of composite material (20) having a fibrous reinforcement constituted by the fibrous preform (200) and densified by the matrix, the intermediate part comprising an aerodynamic profile portion (21) and a root portion (22), characterised in that the root portion (112) of the fibrous blank (100) comprises a separation (106) delimiting an inner recess (140) extending both into the root portion and into the aerodynamic profile portion of the fibrous blank, the inner recess (140) opening at the lower portion (100c) of the fibrous blank, in that the shaping of the fibrous blank (100) comprises the insertion of a spar (130) in the inner recess (140), the spar comprising an aerodynamic profile shaping portion (131) positioned in the aerodynamic profile portion (111) of the fibrous blank (100) and a root shaping portion (132) positioned in the root portion (112) of the fibrous blank in such a way as to respectively form an aerodynamic profile preform portion (211) and a root preform portion (212), and in that the method further comprises, after the densification step, a machining step of the root portion (22) of the intermediate part made of composite material (20) along a determined radius (RU) in such a way as to form a propeller blade or airfoil (10) comprising a root (12) having a rotationally symmetric shape and an aerodynamic profile (11).

2. The method according to claim 1, wherein the separation (106) present in the root portion (112) of the fibrous blank (100) and the root shaping portion (132) of the spar (130) have, in the transverse direction (DT), a width (l106) greater than the machining radius (RU) of the root portion (22) of the intermediate part made from composite material (20).

3. The method according to claim 1 or 2, wherein the spar (130) is made from composite material comprising a matrix-densified fibrous reinforcement or is made of metal material.

4. The method according to any one of claims 1 to 3, wherein the shaping of the fibrous blank (100) further comprises the insertion of a shaping part (150) made of rigid cellular material around the aerodynamic profile shaping portion (131) of the spar (130).

5. The method according to any one of claims 1 to 3, wherein the shaping of the fibrous blank (100) further comprises the injection of an expansive material around the aerodynamic profile shaping portion (131) of the spar (130).

6. A propeller blade or airfoil (10) for a turboprop engine made from composite material comprising a matrix-densified fibrous reinforcement, the propeller blade or airfoil comprising, in a direction of its span (DL), a root (12) and an aerodynamic profile (11), the root and the aerodynamic profile extending in a chord direction (DT) between a leading edge (11a) and a trailing edge (11b), the fibrous reinforcement comprising a fibrous preform (200) having a three-dimensional weave with a root preform portion (212) present in the root (12) and an aerodynamic profile preform portion (211) present in the aerodynamic profile (11), the preform portions of root and aerodynamic profile being connected to one another by the three-dimensional weave, characterised in that the fibrous preform comprises a separation delimiting an inner recess (140) opening at the root preform portion (212), the recess forming a cavity (14) extending both into the root (12) and into the aerodynamic profile (11), in that a spar (130) is present in the cavity (14), the spar comprising an aerodynamic profile shaping portion (131) positioned in a first portion (142) of the cavity 14 and a root shaping portion (132) positioned in a second portion (141) of the cavity, and in that the root (12) of the propeller blade or airfoil has a rotationally symmetric shape.

7. The propeller blade or airfoil according to claim 6, wherein the root shaping portion (132) of the spar (130) is exposed at the leading edge (12a) and the trailing edge (12b) of the root (12) of the propeller blade or airfoil, the remainder of the root shaping portion of the spar being covered by the fibrous preform.

8. The propeller blade or airfoil (30) according to claim 6 or 7, wherein the spar (130) is made from composite material comprising a matrix-densified fibrous reinforcement or is made of metal material.

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

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