Propeller blade or vane with hollow composite base

Abstract

Propeller blade with hollow composite base. A turboprop propeller blade (10) made of composite material comprises a matrix-densified fiber reinforcement, the blade having, along a span direction (DL), a base (12) and an airfoil (11). The fiber reinforcement includes a fiber preform having a three-dimensional weave with a base preform portion and an airfoil preform portion. The fiber preform includes a debonding delimiting a housing forming a cavity (14) extending into both the base (12) and the airfoil (11). A spar (130) is present in the cavity (14), the spar comprising an airfoil conformation portion (131) positioned in a first portion (142) of the cavity 14 and a base conformation portion (132) positioned in a second portion (141) of the cavity. The foot (12) has a shape of revolution.Figure for the abridged version: Fig. 7.

Description

Title of the invention: Propeller blade or blade with hollow composite base 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 have good mechanical strength, they have the disadvantage of being relatively heavy.

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

[0004] US document 2013 / 0017093 describes the production 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 arises from the necessity of being able to rotate the blade or vane around its vertical axis in order to adapt its angle of attack to the flight regime (variable-pitch blade or vane). This need, combined with the fact that the blade or vane must be integrated as low as possible on the disc, necessitates a significant reduction in the size of the foot.

[0006] To this end, 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, in particular 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 tensile and bending mechanical loads usually encountered (caused respectively by centrifugal forces and impacts with objects), the new generation feet can be integrated into the rotor disc using shells metallic, which results in an additional mechanical load in circumferential compression. Description of the 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 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 and the chord direction of the blade or propeller blade to be manufactured, the fibrous blank comprising a root portion and an aerodynamic profile 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 airfoil preform and said foot portion forming foot 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 part of the intermediate part in composite material along a determined radius so as to form a blade or propeller blade comprising a foot having a shape of revolution and a , aerodynamic profile.

[0011] The process of the invention thus makes it possible to produce a propeller blade or a 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 over the entire width of the lower part of the airfoil. In 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 weaving, gives it good mechanical resistance in tension and bending.Furthermore, in the composite foot, there are threads, for example weft threads, oriented in the direction of the blade's chord or vane, which gives it good mechanical resistance in circumferential compression.

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

[0013] By inserting a spar into the fibrous reinforcement in which a part of the foot is fully formed, i.e. woven in one piece, with a part of the aerodynamic profile, a very good mechanical strength of the whole part is ensured and, in particular, with regard to the forces to which the foot may be subjected.

[0014] According to one aspect of the invention, the debonding present in the foot portion of the fiber blank and the foot-shaped 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 part. This allows the entire spar to pass through the foot portion of the fiber blank.

[0015] According to another aspect of the method of the invention, the longeron is made of composite material comprising a fibrous reinforcement densified by a matrix or of metallic material.

[0016] 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.

[0017] 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.

[0018] The invention also relates to a turboprop propeller blade or fan blade made of composite material comprising a fibrous reinforcement densified by a matrix, the blade or fan blade having, along a span direction, a root and an aerodynamic profile, the root and the aerodynamic profile extending along a direction of chord 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 foot preform present in the foot and a portion of the airfoil preform present in the airfoil, the portions of the foot preform and airfoil preform being linked to each other by the three-dimensional weave, characterized in that the fibrous preform includes a debonding delimiting a housing forming a cavity extending both in the foot and in the airfoil, in that a spar is present in the cavity, the spar comprising a portion of the airfoil conformation positioned in a first portion of the cavity and a portion of the foot conformation positioned in a second portion of the cavity, and in that the foot of the blade or propeller blade has a shape of revolution.

[0019] 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.

[0020] 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.

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

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

[0023] [Fig.2] [Fig.2] is an enlarged cross-sectional view in the weft direction of a set of yarn layers showing the formation of a debond in the foot part of the blank of [Fig.1] along a section plane II-II,

[0024] [Fig.3] The [Fig.3] is a schematic perspective view showing the shaping of a part of the foot preform and a part of the aerodynamic profile preform in the fibrous blank of the [Fig.1],

[0025] [Fig.4] Fig.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,

[0026] [Fig.5] Fig.5 is a schematic perspective view showing the injection tooling of the closed Fig.4,

[0027] [Fig. 6] Fig. 6 is a schematic perspective view of an intermediate part in composite material obtained according to an embodiment of the invention,

[0028] [Fig.7] The [Fig.7] is a schematic perspective view of a blade in composite material obtained after machining the foot part of the intermediate part of the [Fig.6]. Description of the implementation methods

[0029] The invention applies generally to various types of propeller blades used in aircraft engines. The invention finds an 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 so-called "cylindrical" root, i.e., one having 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.

[0030] In the following description, the embodiment examples are described in relation to turboprop turbine blades. However, the embodiment examples also apply to aircraft propeller blades.

[0031] Fig. 1 shows very schematically a fibrous blank 100 intended to form the fibrous preform of a blade to be produced.

[0032] The fiber structure 100 is obtained, as schematically illustrated in [Fig.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 leading edge 100a and a trailing edge 100b, the blank comprising an airfoil portion 111 defining two faces 111e and 111e intended to form respectively the upper and lower surfaces of the blade and a foot portion 112 intended to subsequently form a blade foot and extending outside the airfoil blank 111 along the longitudinal direction DL and set back from the leading and trailing edges 100a and 100b along the transverse direction DT.

[0033] By "three-dimensional weaving" or "3D weaving" is meant a weaving method in which at least some of the warp yarns bind weft yarns over several layers of weft such as for example an "interlock weave". By "interlock" weave we mean here a weaving structure in which each layer of weft yarns connects several layers of warp yarns with all the yarns in the same weft column having the same movement in the plane of the weave.

[0034] Other known types of three-dimensional weaving may be used, such as those described in document WO 2006 / 136755, the contents of which are incorporated herein by reference. This document describes, in particular, the production by one-piece weaving of reinforcing fibrous structures for parts such as blades, having a first type of core reinforcement and a second type of skin reinforcement, which provide both the mechanical and aerodynamic properties expected for this type of part.

[0035] The fibrous blank according to the invention can be woven in particular from carbon fiber yarns or ceramic such as silicon carbide.

[0036] As the fibrous blank, whose thickness and width vary, is woven, a certain number of warp yarns 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, in particular allowing the thickness of the blank to be varied 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 US document 2006 / 257260.

[0037] 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.

[0038] A 3D interlock weave of the blank 100 is shown schematically in [Fig. 2]. [Fig. 2] is a partial enlarged view of a warp cross-section in a portion of the blank 100 comprising the unlinking zone 106 (section II-II in [Fig. 1]). In this example, the blank 100 comprises 8 layers of yarns The warp 101 extends substantially in the longitudinal direction DL. In [Fig. 2], the 8 layers of warp yarns are linked by weft yarns Ti to T8 in the bonding zones 105 and 107 of the fiber blank 100, the weft yarns extending substantially in the transverse direction DT. At the unbonding point 106, the woven portion 113 comprises 4 layers of warp yarns 101 linked together by 4 weft yarns Ti 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.

[0039] In other words, the fact that the weft yarns Ti to T4 do not extend into the warp yarn layers of the woven portion 114 and that the weft yarns T5 to T8 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.

[0040] 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 portions 113 and 114 and inserting a stringer 130 into the internal recess 140 formed by the unbundling 106 as illustrated in [Fig. 3]. The spar 130 includes a portion of the airfoil shape 131 which is positioned in an upper part or bottom 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 part or beginning 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 li40 which is greater than the final diameter of the blade root or propeller blade to be produced as explained below. The width l140 corresponds to the width li06 of the debond 106 in the fiber blank 100 ([Fig. 1]). Such a width is necessary to allow the passage of the airfoil shaping portion 111 through the lower part 140b of the housing 140. The root shaping portion 132 of the spar 130 has an elongated shape along the transverse direction Dt in order to adapt to the width l140 of the housing in the lower part 140b of the housing, in particular to control the shape retention of the preform in the injection mold.

[0041] The spar 130 can be made of different materials. In particular, it can be made of a composite material comprising a fibrous reinforcement obtained by three-dimensional weaving or stacking of two-dimensional fibrous plies and densified by a matrix. The spar can also be made of a metallic material.

[0042] In the example described here, a part with a conformation 150 made of rigid, honeycomb-structured material, such as rigid foam, is positioned around the portion of aerodynamic profile conformation 131 of the longeron.

[0043] A fibrous preform 200 is thus obtained comprising, along the longitudinal direction DL, a portion of the airfoil preform 211 and a portion of the base preform 212 having a bulged shape with an internal housing 240 comprising the spar 130 as shown in [Fig. 4]. The portion of the airfoil preform 211 extends along the transverse direction DT between a leading edge portion 211a and a trailing edge portion 211b.

[0044] 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 consists of filling the porosity of the preform, throughout all or part of its volume, with the material constituting the matrix. This densification is carried out in a manner known per se, using the liquid-based process (CVL). The liquid-based process consists of 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 having the shape of the final molded blade.Next, the mold is closed and the liquid matrix precursor (for example, a resin) is injected throughout the cavity to impregnate the entire fibrous part of the preform.

[0045] 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 held in the mold having a shape corresponding to that of the part to be produced.

[0046] In the case of forming a carbon or ceramic matrix, the heat treatment consists of pyrolyzing the precursor to transform the matrix into a carbon or ceramic matrix, depending on the precursor used and the pyrolysis conditions. For example, liquid ceramic precursors, particularly SiC, can be polycarbosilane (PCS), polytitanocarbosilane (PTCS), or polysilazane (PSZ) type resins, while liquid carbon precursors can be resins with a 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.

[0047] 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 gradient Pressure is generally established in this internal space between the point where the resin is injected and the outlets for the resin in order to control and optimize the impregnation of the preform by the resin.

[0048] As illustrated in [Fig.4], the injection of a liquid matrix precursor composition into the fibrous texture and its transformation into a matrix are carried out here 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.

[0049] Once the tool 300 is closed as illustrated in [Fig. 5], the first and second cavities 311 and 321 of the first and second shells 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 while the tool 300 is closed to obtain a specific fiber content in the preform. In this case, compaction pressure is applied to the shells 310 and 320, for example, using a press. The fiber preform can also be compacted in a separate tool before the preform is introduced into the injection mold.

[0050] The tooling 300 further comprises 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 [Fig. 5]).

[0051] 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. The well-known injection or transfer molding process known as RTM ("Resin Transfer Molding") is used for this purpose. According to the RTM process, a resin 360, for example a thermosetting resin, is injected via the injection port 313 of the first shell 310 into the internal volume occupied by the preform 200. The port 323 of the second shell 320 is connected to a pressurized discharge conduit (not shown in [Fig. 6]). This configuration allows Re-establishing 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 approximately at the lower part of the preform, will progressively impregnate the entire preform as it circulates through it until it reaches the discharge port 323, through which the excess resin is removed. 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 carried out under vacuum (VA-RTM).

[0052] The resin used can be, for example, a temperature-class epoxy resin with a resistance of 180 °C. Resins suitable for RTM processes are well known. They preferably have a low viscosity to facilitate their injection into the fibers. The choice of temperature class and / or the chemical nature of the resin is determined according to the thermomechanical stresses to which the part must be subjected. Once the resin has been injected throughout the reinforcement, it is polymerized by heat treatment in accordance with the RTM process.

[0053] 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).

[0054] After injection, polymerization and demolding, an intermediate part of composite material 20 is obtained, as illustrated in [Fig.6], having a fibrous reinforcement consisting of the fibrous preform 200 and densified by the matrix, the intermediate part 20 comprising an aerodynamic profile part 21 and a foot part 22.

[0055] The foot portion 22 of the intermediate composite material part 20 is then machined along a determined radius R( which defines a machining contour Cu so as to form a foot with a shape of revolution. The foot portion 22 is therefore machined to remove the material present outside the machining contour Cu and to form a foot with a shape of revolution. It can be seen in [Fig. 6] that a 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 densified fibrous preform portion 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.

[0056] 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.

[0057] As illustrated in [Fig. 7], a blade 10 is obtained formed of a fibrous reinforcement densified by a matrix which has in its lower part a foot 12 formed by the part of foot preform 212 machined and a blade 11 formed by the part of blade preform 211 of the fibrous preform 200. The blade 10 has a leading edge 1la 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 airfoil 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 airfoil 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.

[0058] As can be seen in [Fig. 7], the foot-shaped portion 132 of the spar 13 is exposed at the leading edge 12a and the trailing edge 12b of the blade or propeller blade root 12, the remainder of the foot-shaped 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 portion of the fibrous blank 100 intended to form the blade or propeller blade root. However, thanks to the elongated shape of the foot conformation portion 132 of the spar 130, most of the external perimeter of the foot 12 is made up of 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. The fibrous reinforcement, with its continuous three-dimensional weave from the foot to the aerodynamic profile's apex, is perfectly suited to transferring local stresses to the rest of the blade or propeller blade, thus increasing its mechanical strength.

[0059] In the example described above, a shaping piece made of rigid, honeycomb material is positioned around the airfoil profile portion of the spar. The use of such a shaping piece is optional, however, as the spar can be shaped to fill the entire volume of the internal cavity in the airfoil portion. Using an additional shaping piece made of rigid, honeycomb material reduces the overall mass of the blade or propeller blade. The shaping piece can also be manufactured in situ around the airfoil profile portion. injecting an expansive material. In this case, solvable fillers such as salt nuclei are temporarily positioned in the fibrous preform before the matrix injection. Once the intermediate part is formed, that is, after the fibrous preform has densified, the fillers are removed and an expansive material is injected into the freed volume.

Claims

Demands

1. A method for manufacturing a turboprop blade or propeller blade (10) made of 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 (100), the fibrous blank having a flat shape extending along a longitudinal direction (DL) and a transverse direction (DT) corresponding respectively to the span direction between a lower part (100c) and an upper part (100d) and to the chord direction of the blade or propeller blade to be manufactured, the fibrous blank (100) comprising a root part (112) and an aerodynamic profile part (111) extending along the longitudinal direction (DL) from the root part and along 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 one-piece fibrous preform (200) having said airfoil portion (111) forming airfoil preform (211) and said foot portion (112) forming foot preform (212), and - the densification of the fibrous preform (200) by a matrix to obtain an intermediate part in 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 part (21) and a foot part (22), characterized in that the foot part (112) of the fibrous blank (100) includes a debonding (106) delimiting an internal housing (140) extending both in the foot part and in the aerodynamic profile part of the fibrous blank, the internal housing (140) opening at the level of the lower part (100c) of the fibrous blank, in that the shaping of the fibrous blank (100) includes the insertion of a spar (130) in the internal housing (140),the spar comprising an airfoil shape portion (131) positioned in the airfoil portion (111) of the fiber blank (100) and a foot shape portion (132) positioned in the foot portion (112) of the fiber blank so as to form respectively an airfoil preform portion (211) and a foot preform portion (212), and in that the method further comprises, after the densification step, a machining step of the foot part (22) of the intermediate part in composite material (20) along a determined radius (RG) so as to form a blade or propeller blade (10) comprising a foot (12) having a shape of revolution and an aerodynamic profile (11).

2. Method according to claim 1, wherein the debonding (106) has in the foot portion (112) of the fibrous blank (100) and the foot shaping portion (132) of the spar (130) have along the transverse direction (DT) a width (l106) greater than the machining radius (RG) of the foot portion (22) of the intermediate part in composite material (20).

3. Method according to claim 1 or 2, wherein the spar (130) is made of composite material comprising a fibrous reinforcement densified by a matrix or of metallic material.

4. A 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 piece (150) of rigid honeycomb material around the aerodynamic profile shaping portion (131) of the spar (130).

5. A 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 conformation portion (131) of the spar (130).

6. A turboprop turbine blade (10) made of composite material comprising a matrix-densified fibrous reinforcement, the blade comprising, along a span direction (DL), a root (12) and an airfoil (11), the root and the airfoil extending along 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 portion of the root preform (212) present in the root (12) and a portion of the airfoil preform (211) present in the airfoil (11), the portions of the root preform and the airfoil preform being linked to each other by the three-dimensional weave, characterized in that the fibrous preform comprises a debonding delimiting an internal housing (140) opening at the level of the portion of the preform foot (212),the housing forming a cavity (14) extending both into the foot (12) and into the aerodynamic profile (11), in that, that a spar (130) is present in the cavity (14), the spar comprising a portion of aerodynamic profile conformation (131) positioned in a first portion (142) of the cavity 14 and a portion of foot conformation (132) positioned in a second portion (141) of the cavity, and in that the foot (12) of the blade or propeller blade has a shape of revolution.

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

8. Propeller blade or blade (30) according to claim 6 or 7, wherein the spar (130) is made of composite material comprising a fibrous reinforcement densified by a matrix or of metallic material.

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

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

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