Method for manufacturing a reinforced blade by stitching
The method enhances the mechanical properties and erosion resistance of composite blades by sewing the skins together at the debonding zone and reinforcing the leading edge, addressing the weakness of monolithic blades.
Patent Information
- Application Number
- FR2023013081
- Authority / Receiving Office
- FR · FR
- Patent Type
- Patents
- Current Assignee / Owner
- Filing Date
- 2023-11-27
- Publication Date
- 2025-11-28
- Estimated Expiration
- 2043-11-27
AI Technical Summary
Monolithic blades or propeller blades made from organic or ceramic matrix composites have debonding points that weaken mechanical properties, creating areas of vulnerability, especially in large blades or propeller blades.
A method involving three-dimensional weaving to create a fibrous blank with a debonding zone, inserting an insert into the internal cavity, sewing the skins together at the debonding zone, and reinforcing the leading edge with a stitching operation to enhance mechanical strength and erosion resistance.
The method strengthens the seams and leading edge, improving mechanical properties and resistance to mechanical stresses while maintaining the efficiency and lightweight properties of composite materials.
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Abstract
Description
Title of the invention: Method for manufacturing a blade reinforced by stitching technical field
[0001] The present invention relates to the field of propeller blades or vanes for aircraft such as those found on turbomachinery. Previous technique
[0002] The fabrication of blades from organic matrix composite (OMC) or ceramic matrix composite (CMC) materials is well known. Such blades comprise a fibrous reinforcement densified by an organic or ceramic matrix. Organic matrix composite (OMC) and ceramic matrix composite (CMC) materials are lighter than most metals while retaining good mechanical properties. This improves the efficiency of the turbomachine, resulting in reduced fuel consumption.
[0003] The fibrous reinforcement of turbomachine blades is formed by a fibrous preform. The fibrous preform is conventionally obtained by weaving a plurality of fibers, for example by three-dimensional weaving.
[0004] US patent 2005 / 0084377 describes a process for manufacturing a turbomachine blade from a monolithic composite material, the blade being manufactured by three-dimensional weaving of a fibrous preform and densification of the preform by a matrix. This process makes it possible to obtain blades with very high mechanical resistance, particularly with respect to shocks or impacts, without risk of delamination. However, monolithic blades or propeller blades have many disadvantages, especially in the case of large blades or propeller blades.
[0005] Manufacturing processes enabling the production of blades or vanes with the introduction of one or more inserts into a dry woven fibrous preform by unbinding have been developed.
[0006] However, the debonding points have weaker mechanical properties than the rest of the woven preform and thus constitute areas of weakness in the resulting blade. Description of the invention
[0007] The invention proposes a method for manufacturing a turbine blade or propeller blade, the method comprising:
[0008] - the production of a fibrous blank by three-dimensional weaving of fibers, said a blank comprising a debonding separating a first skin from a second skin of the fibrous blank so as to form an internal cavity between the skins, the debonding extending at least in part from an edge of the fibrous blank intended to to form the leading edge of the blade or the blade,
[0009] - the introduction of an insert into the internal housing of the fibrous blank in such a way to form a fibrous preform, the insert filling only part of the internal cavity of the blank,
[0010] - the retention of the fibrous preform in a molding cavity of a tool injection molding in the shape of the blade or propeller blade to be manufactured,
[0011] - the injection of a resin into the molding cavity containing the fibrous preform and the transformation of the resin into a matrix by heat treatment to obtain a composite material part having the shape of the blade or vane to be obtained and including a leading edge, and
[0012] - the addition of a reinforcement element attached to the leading edge,
[0013] the method being characterized in that it comprises an operation of sewing the first skin to the second skin by sewing threads in at least one area devoid of insert, said area comprising the edge intended to form the leading edge of the blade or the blade to be obtained, the sewing operation being carried out after the introduction of the insert and before the injection of the resin, and in that the reinforcing element covers at least in part the seam or seams made.
[0014] Thus, the present invention makes it possible to reinforce the seams necessary for insert insertion by performing a stitching operation. The invention is particularly advantageous when the shape of the insert requires a large opening to allow insertion without completely filling the space provided by the seam. Furthermore, by placing at least part of the stitch(es) under the leading edge reinforcement element, the strength of the seam located under the leading edge is increased against the mechanical stresses it undergoes, while also improving erosion resistance.
[0015] According to one aspect of the invention, the sewing threads can follow a crenellated trajectory.
[0016] According to one aspect of the invention, the seam or seams can be made at least in part by tufting.
[0017] According to one aspect of the invention, the seam or seams can be made at least in part with invisible stitches.
[0018] According to one aspect of the invention, the seam(s) can be made at least in part with unilateral stitches known as "one-sided stitches".
[0019] According to one aspect of the invention, the unbinding also extends from an edge of the fibrous blank intended to form the trailing edge of the blade or the vane, the area without insert comprising the edge intended to form the trailing edge of the blade or the vane to be obtained so that the first skin is sewn to the second skin by the sewing threads at the level of this edge intended to form the trailing edge.
[0020] According to one aspect of the invention, at least one of the seams can extend along the edge intended to form the trailing edge.
[0021] According to one aspect of the invention, the fibrous blank can extend along a longitudinal direction corresponding to the span direction of the blade or vane to be manufactured between a lower edge and an upper edge corresponding to the head of the blade or vane to be manufactured, the debonding extending from the lower edge of the fibrous blank.
[0022] According to one aspect of the invention, at least one of the seams can extend along the edge intended to form the leading edge.
[0023] According to one aspect of the invention, all the seams can extend along the edge intended to form the leading edge and be covered by the reinforcing element. Brief description of the drawings
[0024] [Fig-1] Fig. 1 is a schematic perspective view illustrating the weaving of a fibrous blank for the manufacture of a blade.
[0025] [Fig.2A] The [Fig.2A] is a partial cross-sectional view at enlarged scale of a set of layers of wires forming the rough of the [Fig.1].
[0026] [Fig.2B] The [Fig.2B] is another enlarged partial cross-sectional view of a set of wire layers forming the rough outline of the [Fig.1].
[0027] [Fig.3] Fig.3 is an exploded view showing the fabrication of a fibrous preform from the draft of [Fig.1].
[0028] [Fig.4] Fig.4 is a perspective view of the fibrous preform obtained on the [Fig.3].
[0029] [Fig. 5] [Fig. 5] is a perspective view of the fibrous preform of [Fig. 4] on which involves a sewing operation.
[0030] [Fig.6] The [Fig.6] is a cross-sectional view of the [Fig.5].
[0031] [Fig.7] The [Fig.7] is another cross-sectional view of the [Fig.5].
[0032] [Fig.8] Fig.8 is a schematic exploded perspective view showing a injection tooling and the placement of the preform in figures 5 and 6 inside it.
[0033] [Fig.9] Fig.9 is a schematic perspective view showing the tooling injection of the [Fig.8] closed during a resin injection step.
[0034] [Fig. 10] The [Fig. 10] is a schematic perspective view showing the assembly of the reinforcement element on the leading edge. Description of the implementation methods
[0035] The invention applies generally to various types of propeller blades or vanes used in aircraft engines. The invention finds advantageous but not exclusive application in large-diameter propeller blades or vanes. dimensions intended for integration into pivoting or variable-pitch systems. Such blades or propeller blades are generally equipped with a base that offers both a small footprint (compact shape) 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.
[0036] In the following description, an example of an implementation of the method of the invention is described in relation to the manufacture of a blade for an unfaired moving wheel. However, the embodiment also applies to the manufacture of other types of blades or propeller blades for aircraft turbomachinery.
[0037] Fig. 1 shows very schematically a fibrous rough 100.
[0038] The fiber blank 100 is produced by three-dimensional weaving between a plurality of warp yarns 101 and a plurality of weft yarns 102. The fiber blank 100 can be produced in a well-known manner using a Jacquard-type loom. "Three-dimensional weaving" (3D) is understood here as a weaving method in which at least some of the warp yarns interlace weft yarns over several weft layers. A fiber blank produced by three-dimensional weaving is considered to include another type of weave on its surface, for example, two-dimensional weaving, in order to improve its surface finish. The fiber blank may, for example, have a three-dimensional weave structure of the interlock or multisatin type. Various usable three-dimensional weaving methods are described in document WO 2006 / 136755.
[0039] In the illustrated example, the three-dimensional weave is an "interlock" weave. By "interlock" weave, we mean here a weave 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.
[0040] The fibrous blank 100 may comprise a plurality of wires or filaments of various kinds, in particular ceramic or carbon wires, or a mixture of such wires. Preferably, the fibrous blank may be made from silicon carbide fibers. In general, the fibrous blank 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.
[0041] As the fibrous blank 100, whose thickness and width vary, is woven, a certain number of warp threads are not woven, thus defining the desired, continuously variable contour and thickness of the blank 100. An example of an evolving three-dimensional weave, allowing, in particular, the thickness of The roughing 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 EP 1 526 285.
[0042] The fiber blank 100 extends along a first direction between a lower edge 100c and an upper edge. After shaping the fiber blank 100, this first direction will correspond to the span direction of the blade to be obtained. The fiber blank 100 extends along a second direction perpendicular to the first direction between a first edge 100a and a second edge 100b. After shaping the fiber blank 100, this second direction will correspond to the chord direction of the blade to be obtained. The first edge 100a of the fiber blank 100 is intended to form the leading edge of the blade to be obtained. The second edge 100b of the fiber blank 100 is intended to form the trailing edge of the blade to be obtained.
[0043] During weaving, as illustrated in [Fig. 1], a debonding 103 is made within the fibrous blank between two successive layers of warp yarns. The debonding 103 thus separates a first skin 110 from a second skin 120 of the fibrous blank 100.
[0044] A 3D interlock weave mode of the blank 100 is shown schematically in Figures 2A and 2B. [Fig.2A] is a partial enlarged view of two successive warp cross-section planes in a part of the blank 100 not exhibiting a debonding, i.e. in an area of the blank located outside the debonding 103, while [Fig.2B] shows two successive warp cross-section planes in the part of the blank 100 exhibiting the debonding 103.
[0045] In this example, the blank 100 comprises 6 layers of warp yarns 101 extending in the X direction. In [Fig. 2A], the 6 layers of warp yarns are linked by weft yarns T1 to T5. In [Fig. 2B], 3 layers of warp yarns 101 forming the set of yarn layers 105 are linked together by two weft yarns T1, T2, as are the 3 layers of warp yarns forming the set of yarn layers 106, which are linked by two weft yarns T4 and T5. In other words, the fact that the weft yarns T1, T2 do not extend into the yarn layers 106 and that the weft yarns T4, T5 do not extend into the yarn layers 105 ensures the unbinding 103 which separates the sets of warp yarn layers 105, 106 from each other.
[0046] At the end of the weaving process, the warp and weft threads are cut, for example by a pressurized water jet, at the boundary of the woven mass to extract the dry blank 100 shown in [Fig. 3] as it results from the three-dimensional weaving and before any shaping. The unbinding 103 extends over a unbinding zone 104. The unbinding zone 104 created during weaving allows the formation of the two skins 110 and 120, woven independently of each other, delimiting an internal cavity 103a within the blank 100. The unbinding zone 104 allows for the creation of a cavity Internal 103a allows the introduction of one or more inserts inside the fibrous blank 100 for the formation of the preform of the aerodynamic profile structure. The first skin 110 and the second skin 120 can be used to form the fibrous reinforcement of the upper and lower surfaces of the blade to be produced, respectively.
[0047] According to the invention, the debonding zone 104 comprises a portion of the first edge 100a of the fibrous blank 100 intended to form the leading edge. In the example illustrated in the figures, the debonding zone 104 also comprises a portion of the lower edge 100c of the fibrous blank 100.
[0048] Thus, according to the invention, the internal housing 103a is open on the first edge 100a of the fibrous blank 100. In the example illustrated in the figures, the internal housing 103a is also open on the lower edge 100c of the blank 100. The internal housing 103a does not open on the second edge 100b of the blank 100 in the illustrated example. The invention remains within the scope of the invention if the internal housing 103a opens onto the lower edge 100c and the second edge 100b of the blank 100. Nor does the invention depart from the scope of the invention if the internal housing 103a does not open onto the lower edge 100c but opens onto the second edge 100b of the blank 100. The internal housing 103a may optionally open onto the upper edge of the blank 100.
[0049] In the example illustrated in the figures, the fiber blank 100 is intended to form the fibrous reinforcement of the aerodynamic profile of the blade to be produced. Thus, the fiber blank 100 does not include a portion intended to form the fibrous reinforcement of the blade root. However, it does not depart from the scope of the invention if the fiber blank 100 includes a portion intended to form the fibrous reinforcement of the blade root.
[0050] As illustrated in [Fig.3], an insert 40 is inserted into the fibrous blank 100 so as to obtain a fibrous preform 10.
[0051] As illustrated in Figures 3 and 4, the insert 40 comprises a first portion 41 intended to be located inside the aerodynamic profile of the blade and a second portion 42 intended to form the root of the blade. Thus, the first portion 41 of the insert 40 is inserted into the internal housing 103a. The entire first portion 41 of the insert 40 is located within the internal housing 103a. The second portion 42 of the insert remains outside the fibrous blank 100.
[0052] The invention remains within the scope of the invention if the entire insert 40 is inserted into the fibrous blank 100. Nor does the invention fall outside the scope of the invention if the insert comprises a first portion intended to be present inside the aerodynamic profile of the blade and a second portion intended to be present inside the root of the blade. Nor does the invention fall outside the scope of the invention if several inserts are inserted into the same link, or if several inserts are inserted into several links.
[0053] According to the invention, when the insert 40 is introduced into the fibrous blank 100, the entire unbinding zone does not include the insert 40. The insert 40 does not completely fill the internal housing 103a. Thus, the internal housing 103a comprises at least one portion 104a filled by the insert 40 and one or more portions 104b, 104c without the insert 40. In the portion 104a filled by the insert 40, the first and second skins 110 and 120 are separated from each other by the insert 40. In the portion 104a filled by the insert 40, the first and second skins 110 and 120 are in contact with the insert 40. In the portion(s) 104b, 104c without the insert 40, the first and second skins 110 and 120 are not in contact with the insert 40. In the portion(s) 104b, 104c without the insert 40, the first and second skins 110 and 120 are not separated by insert 40.
[0054] According to the invention, the first and second skins 110 and 120 are sewn together in at least one portion 104b, 104c without insert 40 of the internal housing 103 a.
[0055] In the example illustrated in Figures 5 to 7, the first and second skins 110 and 120 are sewn together in the portions 104b, 104c without insert 40 of the internal housing 103a. The first and second skins 110 and 120 are sewn together by one or more stitching fibers or threads 6. A stitch is formed by one or more bonded threads following the same continuous path.
[0056] The first and second skins 110 and 120 can be sewn together by one or more first seams 61 extending along the second direction, that is, along the chord direction of the blade to be produced. The first and second skins 110 and 120 can also be sewn together by one or more second seams 62 extending along the first direction, that is, along the span direction of the blade to be produced. In particular, the second seam(s) 62 can extend along the first edge 100a, intended to form the leading edge of the blade.
[0057] Fig. 6 is a cross-sectional view of the fibrous preform 10 of Fig. 5 along a plane perpendicular to the first direction, i.e. perpendicular to the span direction of the blade to be produced, illustrating an example of the first seam 61. Fig. 7 is a partial cross-sectional view of the fibrous preform 10 of Fig. 5 along a plane perpendicular to the second direction, i.e. perpendicular to the chord direction of the blade to be produced, illustrating an example of the second seam 62.
[0058] Of course, we do not depart from the scope of the invention if the seams extend in other directions. In the example illustrated in Figures 5 to 7, we find both one or more first seams 61 and one or more seams 62. We do not depart from the scope of the invention. understood not within the scope of the invention if the fibrous blank 100 is sewn only by one or more first seams 61 or only by one or more second seams 62.
[0059] In the example illustrated in Figures 6 and 7, the seam(s) produced have a crenellated shape. In particular, the first and / or second seams 61 and 62 may have a crenellated shape. Thus, the stitching fiber(s) or thread(s) 6 comprise, lengthwise, an alternating succession of first stitching fiber portions 6a and second stitching fiber portions 6b. The first stitching fiber portions 6a are perpendicular to the second stitching fiber portions 6b. The second stitching fiber portions 6b extend along a third direction perpendicular to the first and second directions, that is, along the thickness direction of the blade to be produced.
[0060] Adding fibers or threads along a trajectory regularly orthogonal to the debonding improves the strength of the debonding and limits crack propagation in the plane of the debonding. Thus, a seam with a crenellated shape is particularly advantageous.
[0061] We do not, of course, depart from the scope of the invention if the seam produced has a different shape.
[0062] The seam(s) may also be made by tufting. The seam(s) may also be made, at least in part, with blind stitches. The seam(s) may also be made, at least in part, with one-sided stitches. It is, of course, possible to use several types of seams on the same fibrous preform.
[0063] As illustrated in [Fig.8], the blade preform 10 is placed 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.
[0064] Once the tooling 300 is closed as illustrated in [Fig.9], the first and second impressions 311 and 321 respectively of the first and second shells 310 and 320 together define a molding cavity 301 having the shape of the blade to be produced and in which the preform 10 is held.
[0065] The next step is to densify the fibrous portion of the preform, here the shaped fibrous blank, as illustrated in [Fig. 9]. Densifying the fibrous portion of the preform consists of filling its porosity with the material constituting the matrix. This densification is carried out in a manner known per se, following the process Liquid-based (CVL) Adhesive Bonding. 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.
[0066] The transformation of the precursor into a matrix, namely its polymerization, is carried out by heat treatment, generally by heating the injection mold, after removal of any solvent and crosslinking of the polymer, the preform always being held in the mold cavity having a shape corresponding to that of the part to be produced. In the example described here, the injection mold 300 further comprises a lower part 340 and an upper part 350 between which the first and second shells 310 and 320 are placed, the lower part 340 and the upper part 350 being equipped with heating means (not shown in [Fig. 9]).
[0067] 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.
[0068] According to one aspect of the invention, 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.
[0069] As illustrated in [Fig. 9] and in accordance with the RTM process, a resin 380, for example a thermosetting resin, is injected via the injection port 313 of the first shell 310 into the molding cavity 301 occupied by the preform 10. Before the injection of the resin 380, the molding cavity 301 is evacuated, for example, via the port 323 of the second shell 320, which is connected to a vacuum line. This configuration allows the establishment of a pressure gradient between the lower part of the preform 10, where the resin is injected, and the upper part of the preform located near the port 323. In this way, the resin 360, injected approximately at the lower part of the preform, will progressively impregnate the entire of the fibrous portion of the preform, circulating within it until it reaches the discharge port 323, through which the excess is evacuated. Of course, the first and second shells 310 and 320 of the tooling 300 can respectively include several injection ports and several discharge ports.
[0070] The resin used can be, for example, an epoxy resin with a temperature class of 180 °C (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 must be subjected. Once the resin has been injected throughout the reinforcement, it is polymerized by heat treatment according to the RTM process.
[0071] The injection of the resin into the fibrous preform and its transformation into a matrix allows the densification or consolidation of the part of the aerodynamic profile preform 211 of the blade preform constituted by the dry fibrous blank 100.
[0072] After injection and polymerization, a composite material part 1 having the shape of the blade to be produced is demolded. Finally, the composite material part can be trimmed to remove excess resin, and machining operations can be performed. This yields a composite material part 1 comprising a fibrous reinforcement densified by the matrix, said fibrous reinforcement comprising at least the fibrous preform 10.
[0073] In the example illustrated in the figures, the insert 40 is part of the blade or the final blade. Of course, this does not depart from the scope of the invention if one or more inserts are removable, that is to say, eliminated during the manufacturing process of the blade or the blade.
[0074] The composite material part 1 is then assembled with at least one leading-edge reinforcement element 2 to obtain the desired blade or vane 3, as illustrated in [Fig. 10]. The reinforcement element 2 is attached to the leading edge of the blade. The reinforcement element 2 is attached so as to cover at least part of the seam(s). In particular, the reinforcement element 2 may at least partially cover the second seam(s) 62. The reinforcement element 2 may completely cover the second seam(s) 62. The reinforcement element 2 may conventionally be made of metal. The reinforcement element 2 may cover the entire leading edge of the blade.
Claims
1.
2.
3.
4. Demands A method for manufacturing a turbine blade or propeller blade (3), the method comprising: - the production of a fibrous blank (100) by three-dimensional weaving of fibers (101, 102), said blank (100) comprising a debonding (103) separating a first skin (110) from a second skin (120) of the fibrous blank (100) so as to form an internal housing (103a) between the skins (110, 120), the debonding (103) extending at least in part from an edge (100a) of the fibrous blank (100) intended to form the leading edge of the blade or the blade (3), - the introduction of an insert (40) into the internal housing (103a) of the fibrous blank (100) so as to form a fibrous preform (10), the insert (40) filling only part of the internal housing (103a) of the blank (100), - the retention of the fibrous preform (10) in a molding cavity of an injection mold (300) having the shape of the blade or propeller blade (3) to be manufactured, - the injection of a resin into the molding cavity containing the fibrous preform (10) and the transformation of the resin into a matrix by heat treatment to obtain a part made of composite material (1) having the shape of the blade or vane (3) to be obtained and comprising a leading edge, and - the addition of a reinforcing element (2) attached to the leading edge, the process being characterized in that it comprises an operation of sewing the first skin (110) to the second skin (120) by sewing threads (6) in at least one area devoid of insert (104b, 104c), said area (104b) comprising the edge (100a) intended to form the leading edge of the blade or vane (3) to be obtained, the sewing operation being carried out after the introduction of the insert (40) and before the injection of the resin, and in that the reinforcing element (2) covers at least part of the seam(s) (61, 62) made. Manufacturing method according to claim 1, wherein the stitching threads (6) follow a crenellated trajectory. Manufacturing method according to claim 1 or 2, wherein the seam or seams are made at least in part by tufting. A manufacturing method according to any one of claims 1 to 3, in which the seam(s) are made at least partly with invisible stitches.
5. A manufacturing method according to any one of claims 1 to 4, wherein the seam or seams are made at least in part with one-sided stitches.
6. A manufacturing method according to any one of claims 1 to 5, wherein the unbinding also extends from an edge of the fibrous blank intended to form the trailing edge of the blade or vane, the insert-free area comprising the edge intended to form the trailing edge of the blade or vane to be obtained such that the first skin is sewn to the second skin by the stitching threads at the level of this edge intended to form the trailing edge.
7. A manufacturing method according to any one of claims 1 to 6, wherein the fibrous blank (100) extends along a longitudinal direction corresponding to the span direction of the blade or vane (3) to be manufactured between a lower edge (100c) and an upper edge corresponding to the head of the blade or vane (3) to be manufactured, the debonding (103) extending from the lower edge (100c) of the fibrous blank (100).
8. A manufacturing method according to any one of claims 1 to 7, wherein at least one of the seams (62) extends along the edge (100a) intended to form the leading edge.
9. A manufacturing method according to claim 8, wherein all the seams extend along the edge intended to form the leading edge and are covered by the reinforcing element.