Soluble plugs for creating a blind cavity in a composite blade

Abstract

The present invention relates to a manufacturing method (S) of a blade (7) comprising the following steps: - S1: three-dimensional weaving of a fibrous reinforcement (20) so as to form a first skin (21) and a second skin (21) delimiting between them a cavity (23); - S2: insertion of a core (40) into the cavity (23); - S3: insertion of a first plug (31) opening into the cavity (23) so as to come into contact with the core (40); - S4: placement of the fibrous reinforcement (20) comprising the core (40) and the first plug (31) in a mold and die injection; - S5: dissolution of the first plug (31) and the core (40), so as to form a through passage (33) and a housing (41); and - S6: insertion of a second plug (32) into the through passage (33). Figure for abstract: Fig. 3

Description

Title of the invention: Soluble plugs for creating a blind cavity in a composite blade Technical field

[0001] The present disclosure relates to the general field of propulsion systems, and more particularly to the blades of a propulsion system which may comprise a structure made of composite material.

[0002] The present disclosure relates more particularly, but not exclusively, to a blade intended to be used in a rotor or a stator of a fan of an aircraft engine, the fan being able to be shrouded or unshrouded. STATE OF THE ART

[0003] The design of fan blades requires taking into account opposing constraints.

[0004] On the one hand, the sizing of these blades must allow optimal aerodynamic performance (maximize efficiency and provide thrust while minimizing losses). Improving the aerodynamic performance of the fan tending towards an increase in the bypass ratio (or BPR) implies an increase in the external diameter and therefore the span of these blades.

[0005] On the other hand, it is also necessary to guarantee resistance to the mechanical stresses that can be exerted on these blades while limiting their acoustic signature.

[0006] The advantage of unducted fan (or propeller) engines is that the diameter of the fan is not limited by the presence of a fairing, so that it is possible to design an engine with a high dilution ratio, and consequently reduced fuel consumption.

[0007] Thus, in this type of engine, the fan blades can have a large span.

[0008] It has been proposed to make these blades from metallic material. Although blades made from metallic material have good mechanical strength, they nevertheless have the disadvantage of having a relatively large mass.

[0009] In order to reduce this mass, it is desirable to be able to manufacture these blades from composite material. To this end, the composite material of the fan blades generally comprises a fibrous reinforcement produced by three-dimensional weaving densified by a polymer matrix. Where appropriate, the blades may comprise skins made from composite material and defining the aerodynamic profile structure of the blade, and a set of stiffeners housed in a cavity delimited by the skins.

[0010] It appears, however, that the current manufacturing process constrains the stiffeners, intended to ensure the connection of the skins, to geometries which do not offer satisfactory mechanical behavior. The blades are therefore liable to be damaged during engine operation under the effect of repeated static and / or dynamic loading. However, such damage has the consequence of modifying the vibration response of the blade and therefore reducing its service life and calling into question its certification. EXPOSED

[0011] An aim of the invention is to remedy the aforementioned drawbacks by proposing a method for manufacturing a blade made of composite material, in particular a mobile fan blade or an external fixed guide blade (stator), which is simple to produce while effectively limiting the deformation of the blade profile during operation.

[0012] To this end, according to a first aspect of the invention, a method of manufacturing a blade is proposed, comprising the following steps: - SI: three-dimensional weaving of a fibrous reinforcement so as to form a first skin and a second skin facing each other, the first skin and the second skin each having an internal face delimiting a cavity between them, the fibrous reinforcement comprising a plurality of strands; - S2: insertion of a core into the cavity; - S3: insertion of a first plug between the strands, the first plug opening into the cavity so as to come into contact with the core; - S4: placing the fibrous reinforcement comprising the core and the first plug in a mold and injecting a matrix into the mold so as to embed the fibrous reinforcement in the matrix; - S5: dissolution of the first plug and the core, so as to form a through passage in the fibrous reinforcement at the location of the first plug and a housing at the location of the core, the through passage opening onto the housing; and - S6: insertion of a second plug into the through passage.

[0013] The method according to the invention is advantageously supplemented by the following characteristics, taken alone or in one of their technically possible combinations:

[0014] - at least two cores are inserted into the cavity in step S3, the cores being spaced apart so as to define a space, the space extending from a leading edge boundary of the cavity which is adjacent to a leading edge of the blade to a trailing edge boundary which is adjacent to a trailing edge of the blade,

[0015] - there are at least as many first plugs as there are cores,

[0016] - step S2 further comprises inserting a fibrous bar into the space between the two cores, the fibrous bar extending from the leading edge boundary to the trailing edge boundary and being embedded in step S4 in the matrix so as to form a stiffener,

[0017] - the core comprises two core portions extending successively between a leading edge boundary of the cavity which is adjacent to a leading edge of the blade and a trailing edge boundary of the cavity which is adjacent to a trailing edge of the blade, the core portions being spaced apart from each other so as to delimit additional spaces, each additional space being configured to be embedded in the matrix during step S5,

[0018] - step S2 further comprises inserting an additional fibrous bar into each additional space, each additional fibrous bar being embedded in step S4 in the matrix so as to form additional stiffeners,

[0019] - the first plug is elongated.

[0020] The invention also relates to a blade comprising a three-dimensional fibrous reinforcement densified by a matrix, the fibrous reinforcement comprising a first skin and a second skin facing each other, the first skin and the second skin each having an internal face and the fibrous reinforcement comprising a plurality of strands; the dawn being characterized in that: - the internal faces of the first skin and the second skin delimit an internal housing; - the internal faces of the first skin and the second skin are connected by the matrix between the housing and a foot of the blade; - a through passage opens into the accommodation; and - a second plug is inserted into the through passage.

[0021] The blade according to the invention is advantageously completed by an additional internal housing between the housing and the root of the blade, the additional internal housing being separated from the housing by a fibrous bar forming a stiffener, the fibrous bar extending from a leading edge limit of the housing which is adjacent to a leading edge of the blade to a trailing edge limit of the housing which is adjacent to a trailing edge of the blade,

[0022] Finally, the invention relates to a fan comprising a rotor or stator blade comprising a blade as above and a propulsion system comprising such a fan and a casing, the blades being mounted on a fan hub and configured to be movable in rotation around an axis of the fan, or fixed to the casing of the propulsion system. DESCRIPTION OF FIGURES

[0023] Other characteristics, aims and advantages will emerge from the following description, which is purely illustrative and non-limiting, and which must be read in conjunction with the appended drawings in which:

[0024] [Fig.l] schematically represents an example of an engine including an unducted fan in which a blade made of composite material can be implemented;

[0025] [Fig.2] illustrates an example of an aircraft comprising engines according to one embodiment;

[0026] [Fig.3] is a flowchart illustrating steps of an exemplary method of fa building a dawn;

[0027] [Fig.4] is a sectional view of a blade according to a first embodiment, in a plane comprising the chord of the blade at the blade root and the extension axis of the blade;

[0028] [Fig.5] is a sectional view of the blade of [Fig.4] in a plane normal to the axis blade extension;

[0029] [Fig.6] is a succession of sectional views of a blade following the stages of a example of a manufacturing process, in a plane comprising the blade chord at the blade root and the blade extension axis;

[0030] [Fig.7] is a succession of sectional views of a blade of [Fig.6] in a plane normal to the axis of the engine;

[0031] [Fig.8] is a diagram of a plug inserted into an example of weaving according to a embodiment; and

[0032] [Fig.9] is a diagram of a plug inserted into an example of weaving according to another embodiment.

[0033] Throughout the figures, similar elements bear identical references. DETAILED DESCRIPTION

[0034] In the following, the present description will relate more particularly to a blade 7 of a fan blade, the fan blade being able to comprise a rotor or a stator, in order to simplify the description. This is not, however, limiting, the description applying to any blade, rotor or stator, of a propulsion system 1, in particular for an aircraft 100, having a span sufficient to comprise two skins made of a composite material and delimiting an internal cavity 23. The blade 7 can in particular be implemented in a blade which has a diameter greater than or equal to 150 cm, preferably greater than or equal to 200 cm, for example less than or equal to 400 cm. The blade 7 thus preferably has a height, or radial extent, greater than or equal to 50 cm, preferably greater than or equal to 70 cm, for example of the order of 80 cm to 100 cm, being for example less than or equal to 160 cm.The disclosure can thus be applied to a fan blade of an “Open Rotor” type engine (comprising two counter-rotating fan rotors 4 and 5 and a nacelle 3), to the moving and / or fixed blades of a USF type engine (for “Unducted Single Fan” in English, . which includes a single fan rotor), to the moving and / or fixed blades of a turbomachine type engine (comprising a shrouded fan rotor and OGV type blading) or to the moving blades of a turboprop (comprising a single fan rotor, or propeller).

[0035] In the present application, the axis of rotation of the rotor of the fan 3 is called the X axis. The axial direction corresponds to the direction of the X axis and a radial direction is a direction perpendicular to this X axis and passing through it. Each blade 7 extends along a respective Y axis, which may correspond to its pitch axis when the blade 7 is rotatably mounted relative to a hub 6 of the fan (case of a variable pitch fan). This Y axis extends in a generally radial direction relative to the X axis. Finally, internal (respectively, interior) and external (respectively, exterior) are used with reference to a radial direction so that the internal part or face of an element is closer to the X axis than the external part or face of the same element.

[0036] The blade 7 will thus be defined relative to the X axis of the rotor on which it is intended to be mounted and its Y axis of extension.

[0037] The term “fan” will also be used in the remainder of the description, although the invention applies mutatis mutandis to a propeller.

[0038] In [Fig. 1], the fan rotor comprises a hub 6 (or blade hub) rotatably mounted relative to a casing of the engine and a plurality of blades 7 fixed to the hub 6. The blades 7 extend substantially radially relative to the axis of rotation X of the rotor.

[0039] The fan blade 7 comprises a blade root 8 configured to be inserted into the hub 6, a blade 12 suitable for being arranged in a flow and a stilt corresponding to the zone of the blade 7 which extends between the outlet of the hub 6 (at the bearing surfaces) and the blade 12. The blade 12 has a lower surface, an upper surface, a leading edge 10, a trailing edge 11 and a tip 9. In a manner known per se, the leading edge 10 is configured to extend opposite the flow of gases entering the engine 1. It corresponds to the front or upstream part of an aerodynamic profile which faces the air flow and which divides the air flow into an lower surface flow and an upper surface flow. The trailing edge 11 corresponds to the rear or downstream part of the aerodynamic profile, where the intrados and extrados flows meet. The chord corresponds to the segment connecting the leading edge 10 to the trailing edge 11 of the blade 7.In particular, a chord at the bottom is called a chord measured at the foot 8 of the blade 7 and a chord at the top is called a chord measured near the top 9 of the blade 7.

[0040] The blade 7 comprises a fibrous reinforcement 20 and a matrix in which the fibrous reinforcement 20 is embedded. The fibrous reinforcement 20 comprises a blade portion intended to form the blade 12 with an aerodynamic profile, a root zone and a stilt zone intended to form foot 8 and Péchasse de l’aube 7, respectively.

[0041] The fibrous reinforcement 20 can be formed in a single piece and obtained by three-dimensional or multi-layer weaving with evolving thickness. It can in particular comprise carbon, glass or aramid fibers. The matrix, also called the impregnation matrix, which coats strands 200 of the fibrous reinforcement 20 is typically a plastic material, typically a polymer, for example epoxy, bis-maleimide or polyimide.

[0042] The blade portion 12 comprises two skins 21. The fiber reinforcement 20 is woven such that it comprises the warp strands 200 which extend continuously both inside the aerodynamically profiled blade portion 12 and inside the root area 8 of the blade 7. The fiber reinforcement 20 can be produced by weaving on a jacquard type loom. During weaving, bundles of warp strands 200 are arranged in several layers. Weft strands 200 are interlaced with the warp strands 200 so as to bind the different layers of warp strands 200 together. The three-dimensional weaving can be an “interlock” weave. By "interlock" is meant a weave pattern in which each layer of 200 weft strands binds together several layers of 200 warp strands with all the 200 strands of the same weft column having the same movement in the plane of the weave.Other types of known three-dimensional weaves may be used, such as those described in WO 2006 / 136755.

[0043] Within the fiber reinforcement 20, the warp strands and the weft strands extend respectively in a first direction (or warp direction, which may correspond substantially to the Y axis of the blade 7) and a second direction (or weft direction, corresponding substantially to the direction of extension of the chord of the blade 7).

[0044] In the present application, by strand 200 we mean any type of wire(s) forming in particular the fibrous reinforcement 20.

[0045] Preferably, each skin 21 comprises at least two layers of strands 200 over the entire height of the blade 12, for example four layers.

[0046] Each skin 21 comprises an internal face 22, oriented towards the inside of the blade 7, and an external face 71 respectively forming the intrados and the extrados of the blade 7. The internal faces 22 delimit between them a cavity 23 of the blade 7, which extends generally from Péchasse to the tip 9 of the blade 7 between the intrados and the extrados of the blade 7. The skins 21 comprising at least two layers of weft strands 200, the cavity 23 of the blade 7 extends at a distance from the trailing edge 11 and the tip 9, these zones being of lesser thickness than the rest of the blade 12 and therefore generally not allowing the formation of a cavity 23 between the two skins 21.

[0047] The cavity 23 can be obtained by creating a delinking in the fiber reinforcement, that is to say by not connecting the warp strands 200 of several warp layers. successive. The internal faces 22 of the skins 21 are therefore directly connected to each other at a junction 24 which delimits the cavity 23. The cavity 23 therefore opens neither into the leading edge 10, nor into the trailing edge 11, nor into the tip 9 of the blade 7. The cavity 23 therefore comprises an upper limit 25 located on the side of the tip 9 of the blade 7, a leading edge limit 27 close to the leading edge 10 of the blade 7 and a trailing edge limit 28 close to the trailing edge 11 of the blade 7. On the other hand, the skins 21 are disjointed at a lower limit 26 of the cavity 23 which is adjacent to Péchasse and to the root 8 of the blade 7.

[0048] In order to limit the deformations of the skins 21 under aerodynamic loading as well as the specific vibration modes of the skins 21, without penalizing its mass, the blade 7 may further comprise one or more stiffeners 30 extending into the cavity 23, each stiffener 30 being fixed on the internal face of the first skin 21 and of the second skin 21 so as to connect them. The stiffeners 30 therefore extend through the cavity 23, from the internal face 22 of one of the skins 21 to the internal face 22 opposite the other of the skins 21. The stiffeners 30 are furthermore monolithic with the skins 21 and their constituent material is identical to the plastic material of the matrix.

[0049] The stiffeners 30 thus form an internal structure in the blade 7 making it possible to stiffen the blade 12 in one or more directions, depending on the shape and the direction(s) of extension of the stiffeners 30, by connecting the internal faces 22 of the skins 21. The stiffeners 30 thus contribute to the mechanical behavior of the blade 12 in addition to their structural role of connecting the skins 21. The plastic matrix forming the stiffeners 30 in fact has a Young's modulus approximately ten times greater than that of the foams and other filling materials usually used.

[0050] These stiffeners 30 being monolithic with the skins 21 and formed in the same constituent material as the matrix, they do not create a critical interface with the fiber reinforcement 20 likely to create weak zones, which reduces the risks of damage. The stiffeners 30 being made of the same plastic material as the constituent material of the matrix, the stiffeners 30 can be made directly during the molding of the fiber reinforcement 20, during the injection of the matrix into the fiber reinforcement 20 intended to embed the fibers of the reinforcement 20. The manufacturing method of the blade 7 is thus simplified. It is also not necessary to fill the cavity 23 with other filling parts such as foams or any other material usually used. The stiffeners 30 are therefore separated two by two by an air gap. The mass of the blade 7 obtained is therefore not significantly modified.

[0051] The stiffeners 30 can be produced simultaneously with the filling of the fibers of the fibrous reinforcement 20 with the plastic matrix. For this purpose, each stiffener 30 is configured so as to put the junction 24 (limit between the skins 21 and the cavity 23) and the lower limit 26 of the cavity 23, so as to allow the uniform filling of the fibers of the fibrous reinforcement 20 with the matrix and the formation of the stiffeners 30 and, where appropriate, the evacuation of a core 40 through the lower limit during its dissolution.

[0052] A stiffener 30 may extend from the leading edge limit 27 to the trailing edge limit 28, the stiffener 30 then being said to be transverse and for example perpendicular to the Y axis. A stiffener 30 may also extend from the upper limit 25 to the lower limit 26, then being for example parallel to the Y axis. In the case where several stiffeners 30 are formed, the two arrangements may be combined, so that the stiffeners 30 are intersected and form a grid or a network in the blade 7, which allows optimal stiffness in both torsion and bending.

[0053] Optionally, a stiffener 30 may comprise a fibrous bar 50 whose fibers are embedded during the molding of the fibrous reinforcement 20, which increases the stiffness of the stiffener 30.

[0054] A manufacturing method S of the blade 7 may comprise the following steps.

[0055] During a step SI, the fibrous reinforcement 20 is produced by three-dimensional weaving. on a jacquard loom. During weaving, bundles of 200 warp strands are arranged in several layers of several hundred 200 strands each. 200 weft strands are interwoven with the 200 warp strands so as to bind the different layers of 200 warp strands together. Preferably, the three-dimensional weave is an interlock weave.

[0056] The step S1 of weaving the raw fiber reinforcement 20 (or preform) comprises the weaving of the two skins 21, which together form an aerodynamic profile of the blade 7 which comprises the tip 9 and a lower part which comprises the junction 24 and delimits the cavity 23. The portion of the fiber reinforcement 20 intended to form the upper part of the skins 21 is woven by interlacing all the warp strands 200 necessary for producing the fiber reinforcement 20. Once the fiber reinforcement 20 has reached the junction 24, a delinking is initiated between two successive layers of warp strands 200 in order to form the cavity 23. Then, the two portions of fiber reinforcement 20 forming the parts of the skins 21 which delimit the cavity 23 are woven in parallel with each other, being separated by the delinking zone.The skins 21 however remain woven together in an area intended to form the leading edge 10 and the trailing edge 11 of the blade 7 in order to close the cavity 23 at these edges. In this way, each of the two portions of fibrous reinforcement 20 forming the cavity 23 comprises warp strands 200 which extend inside the portion of fibrous reinforcement 20 forming the upper part of the blade 7.

[0057] Alternatively, several fibrous preforms may be woven separately, the preforms then being assembled together to form the upper portion and the lower part of the fibrous reinforcement 20 and to delimit the cavity 23.

[0058] During a step S2, a core 40 is inserted into the cavity 23. The core 40 is configured to fill the areas of the cavity 23 intended to separate the stiffener 30. Its shape is therefore complementary to the shape of the stiffener 30. The core 40 forms in the cavity 23 an empty space 42 intended to define a stiffener 30 after injection of the matrix.

[0059] The core 40 is made of a soluble material, that is to say a material capable of being dissolved by a predetermined solvent in order to be removed from the cavity 23 of the blade 7. The material constituting the core 40 is chosen so that its solvent is neutral with respect to the materials constituting the fibrous reinforcement 20 (strands 200 and matrix), in order not to damage the blade 7 during its dissolution.

[0060] For example, the core 40 may comprise a thermoplastic polymer ST 130 which dissolves in a basic bath at 70°C. A core 40 made of thermoplastic polymer has the advantage of being able to be produced by 3D printing, which allows the use of a monolithic core 40 and / or the implementation of stiffener shapes 30 whose geometry is more complex.

[0061] Alternatively, the core 40 may be segmented and comprise several parts, or several cores 40 may be inserted, in order to define several empty spaces 42 intended to form the stiffeners 30.

[0062] Alternatively, step S2 further comprises inserting a fibrous bar 50 into the space 42 between the two cores 40, the fibrous bar 50 extending from the leading edge limit 27 to the trailing edge limit 28 and being embedded in step S4 in the matrix so as to form a stiffener 30. Preferably, a fibrous bar 50 is made of the same material as the fibrous reinforcement 20. A stiffener 30 comprising a fibrous bar 50 has a greater stiffness compared to a stiffener 30 made solely of injected matrix.

[0063] Optionally, step S2 further comprises inserting an additional fibrous bar 50 into each additional space 42 before inserting the next core 40, each additional fibrous bar 50 being embedded in step S4 in the matrix so as to form additional stiffeners 30. The stiffeners 30 then define an additional housing 41 between the housing 41 and the root of the blade, the additional internal housing 41 being separated from the housing 41 by a fibrous bar 50 forming a stiffener 30, the fibrous bar 50 extending from the leading edge limit 27 of the housing 41 to the trailing edge limit 28 of the housing 41, i.e. perpendicular to the Y axis. Such an arrangement considerably increases the torsional stiffness of the blade 7.

[0064] In a step S3, a first plug 31 is inserted between the strands 200, the first plug 31 opening into the cavity 23 so as to come into contact with the core 40. The first plug 31 is preferably made of a soluble material, for example the same material as the core 40 and is inserted into the fibrous reinforcement 20, between the strands 200 of fibers, at the location where a through passage 33 which opens onto the core 40 in the cavity 23 will be desired. The first plug 31 being inserted between the strands 200 of the fibers, the fibers are deflected but not severed and the mechanical impact applied to the fibrous reinforcement 20 is then limited because the stresses are exerted around the insertion point in a controlled and repeatable manner. The integrity of the fibrous reinforcement 20 and its mechanical properties are therefore preserved, since the fibers are always continuous, which is not the case when a piercing is made.

[0065] Preferably, the first plug 31 is of a shape adapted to the weaving pattern of the fiber reinforcement 20, that is to say adapted to the three-dimensional paths of the strands 200, for example by having an elongated or tapered shape which makes the first plug 31 non-demouldable. Thus, the first plug 31 can only be removed by dissolution. Steps S2 and S3 can be carried out in a different order than that presented here, the first plug 31 then being inserted before the core 40.

[0066] During a step S4, the fibrous reinforcement 20 comprising the core 40 is placed in a mold. Matrix is ​​then injected into the mold so as, on the one hand, to fill the spaces 42 to form the stiffeners 30 and, on the other hand, to embed the fibrous reinforcement 20 in the matrix. The stiffeners 30 thus form an internal structure in the blade 7 making it possible to stiffen the blade 12 in one or more directions, depending on the shape and the direction(s) of extension of the empty spaces 42, by connecting the internal faces 22 of the skins 21. The plastic matrix forming the stiffeners 30 in fact has a Young's modulus approximately ten times higher than that of the foams and other filling materials usually used.

[0067] A blade 7 is then obtained, comprising the fibrous reinforcement 20 densified by the matrix and stiffeners 30. Following this step, the blade 7 however also comprises the core 40, which is still housed in the cavity 23 and fills the volume of the cavity 23 which is not occupied by stiffeners 30.

[0068] During a step S5, the first plug 31 and the core 40 are dissolved under conditions adapted to the type of material chosen for the first plug 31 and the core 40 (thermoplastic polymer / basic bath at 70°C for example) consistent with the material of the fibrous reinforcement 20. The solvent can for example be projected against the first plug 31 in order to dissolve it progressively and then to dissolve the core 40 via the through passage 33 thus formed. As a variant, the blade 7 can simply be immersed in a solvent bath.

[0069] The dissolution of the core 40 and the evacuation of the solvent are notably enabled by the configuration of the first plug 31, the position and size of which enable the solvent to reach the entire core 40 and dissolve it, including in cavities which would have been inaccessible without the through passage 33, thus preventing the total dissolution of the core 40. This through passage 33 makes it possible to create stiffener geometries that are impossible to obtain using the methods of the state of the art, in particular the transverse stiffeners 30 described.

[0070] After dissolution of the core, the stiffeners 30 are spaced from each other by air blades in place of the core 40.

[0071] During a step S6, a second plug 32 is inserted into the through passage 33 by adding a polymer that hardens at room temperature, for example a thermosetting resin that crosslinks at room temperature or a heated thermoplastic that sets in shape upon cooling.

[0072] Optionally, at least two cores 40 are inserted into the cavity in step S3, the cores 40 being spaced apart so as to delimit a space 42, the space 42 extending from the leading edge limit 27 to the trailing edge limit 28 of the cavity 23. Such an arrangement allows the formation during step S4 of one or more stiffeners 30 extending from the leading edge limit 27 to the trailing edge limit 28, i.e. axially, thus providing greater torsional stiffness to the blade 7 and allowing compartmentalization of damage in the event of a high-energy impact, for example in the event of impact or ingestion of a foreign body by the propulsion system 1.

[0073] In order to allow the dissolution of all the cores 40, there are preferably at least as many first 31 plugs as there are cores 40, each core 40 being in contact with at least one first plug 31. Of course, a greater number of first plugs 31 facilitates dissolution.

[0074] To also increase the bending stiffness of the blade 7, the core 40 may comprise at least two core portions 40 extending successively between the leading edge limit 27 of the cavity 23 and the trailing edge limit 28, the core portions 40 being distant from each other so as to delimit additional spaces 42, these spaces 42 being preferentially parallel to the Y axis, each additional space 42 being configured to be embedded in the matrix during step S5 in order to form stiffeners 30 extending from the upper limit 25 to the lower limit 26.

[0075] The manufacturing method S therefore makes it possible to obtain a blade 7, the internal faces 22 of the first skin 21 and of the second skin 21 delimit an internal housing 33, the through passages 33 being closed by a second plug 32. The use of first plugs 31 makes it possible to obtain any type of geometry of stiffeners 30, including transverse stiffeners 30 connecting the leading edge 27 and trailing edge 28 limits, these stiffeners 30 being able to be rectilinear as well as curvilinear, but also the formation of a grid or a network of stiffeners 30. The through passage 33 obtained by the dissolution of the first plugs 31 makes it possible to hollow out any zone made inaccessible to the solvent from the lower limit 26. The blades 7 obtained are therefore lightened while presenting optimized mechanical characteristics, in particular in stiffness. Even in the case where the stiffeners 30 do not completely prevent the dissolution of the cores 40, the manufacturing method S allows a considerable saving of time by facilitating access of the solvent.

Claims

Claims

1. Manufacturing method (S) of a blade (7) comprising the following steps: - S1: three-dimensional weaving of a fibrous reinforcement (20) so as to form a first skin (21) and a second skin (21) facing each other, the first skin (21) and the second skin (21) each having an internal face (22) delimiting between them a cavity (23), the fibrous reinforcement (20) comprising a plurality of strands (200); - S2: insertion of a core (40) into the cavity (23); - S3: insertion of a first plug (31) between the strands (200), the first plug (31) opening into the cavity (23) so as to come into contact with the core (40); - S4: placing the fibrous reinforcement (20) comprising the core (40) and the first plug (31) in a mold and injecting a matrix into the mold so as to embed the fibrous reinforcement (20) in the matrix;- S5: dissolution of the first plug (31) and the core (40), so as to form a through passage (33) in the fibrous reinforcement (20) at the location of the first plug (31) and a housing (41) at the location of the core (40), the through passage (33) opening onto the housing (41); and - S6: insertion of a second plug (32) into the through passage (33).;

2. A manufacturing method according to claim 1, wherein at least two cores (40) are inserted into the cavity in step S3, the cores (40) being spaced apart so as to define a gap (42), the gap (42) extending from a leading edge boundary (27) of the cavity which is adjacent to a leading edge (10) of the blade (7) to a trailing edge boundary (28) which is adjacent to a trailing edge (11) of the blade (7).

3. Manufacturing method according to claim 2, comprising at least as many first (31) plugs as cores (40).

4. A method (S) of manufacturing a blade (7) according to one of claims 2 and 3, wherein step S2 further comprises inserting a fibrous bar (50) into the space (42) between the two cores (40), the fibrous bar (50) extending from the leading edge limit (27) to the trailing edge limit (28) and being embedded in step S4 in the matrix so as to form a stiffener (30).

5. Method of manufacturing (S) a blade (7) according to one of the claims 1 to 4, wherein the core (40) comprises two core portions (40) extending successively between a leading edge boundary (27) of the cavity (23) which is adjacent to a leading edge (10) of the blade (7) and a trailing edge boundary (28) of the cavity which is adjacent to a trailing edge (11) of the blade (7), the core portions (40) being spaced apart from each other so as to delimit additional spaces (42), each additional space (42) being configured to be embedded in the matrix during step S5.

6. A manufacturing method according to claim 5, wherein step S2 further comprises inserting an additional fibrous bar (50) into each additional space (42), each additional fibrous bar (50) being embedded in step S4 in the matrix so as to form additional stiffeners (30).

7. Method (S) for manufacturing a blade (7) according to one of claims 1 to 6, in which the first plug (31) is elongated.

8. Blade (7) comprising a three-dimensional fibrous reinforcement (20) densified by a matrix, the fibrous reinforcement (20) comprising a first skin (21) and a second skin (21) facing each other, the first skin (21) and the second skin (21) each having an internal face (22) and the fibrous reinforcement (20) comprising a plurality of strands (200); the blade (7) being characterized in that: - the internal faces (22) of the first skin (21) and the second skin (21) delimit an internal housing (41); - the internal faces (22) of the first skin (21) and the second skin (21) are connected by the matrix between the housing (41) and a root (8) of the blade (7); - a through passage (33) opens into the housing (41); and - a second plug (32) is inserted into the through passage (33).

9. A blade (7) according to claim 8, further comprising an additional internal housing (41) between the housing (41) and the root of the blade, the additional internal housing (41) being separated from the housing (41) by a fibrous bar (50) forming a stiffener (30), the fibrous bar (50) extending from a leading edge boundary (27) of the housing (41) which is adjacent to a leading edge (10) of the blade (7) to a trailing edge boundary (28) of the housing (41) which is adjacent to a trailing edge (11) of the blade (7).

10. Fan (3) comprising a rotor or stator blade comprising blades (7) according to one of claims 8 and 9.

11. Propulsion system (1) comprising a fan (3) according to claim 10 and a casing (2), the blades (7) being mounted on a hub (6) of the fan (3) and configured to be movable in rotation around an axis (X) of the fan, or fixed on the casing (2) of the propulsion system (1).

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