Hollow dawn with resin stiffeners in a curve

Abstract

The present invention relates to a blade (7) comprising a first skin (21) and a second skin (21) each having an inner face (22) delimiting between them an inner housing (23), the blade (7) further comprising a set of stiffeners (30) extending through the inner housing (23) by being fixed on the inner face (22) of the first skin (21) and of the second skin (21) so as to connect them, the inner housing (23) having a lower limit (26) adjacent to a root (8) of the blade (7), a leading edge limit (27) and a trailing edge limit (28), all or part of the stiffeners (30) extending in the inner housing (23) from a lower limit (26) to a leading edge limit (27) to a trailing edge limit (28). Figure for abstract: Fig. 3a

Description

Title of the invention: Hollow blade with curvilinear resin stiffeners 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 geometries of the stiffeners, designed to ensure the connection of the skins, do not offer satisfactory mechanical behavior and the blades are therefore likely to be damaged during engine operation under the effect of repeated static and / or dynamic loading. Such damage, however, has the consequence of modifying the vibration response of the blade and therefore reducing its service life as well as its certification. EXPOSED

[0011] An aim of the invention is to remedy the aforementioned drawbacks by proposing a blade, in particular a mobile fan blade or an external guide blade (stator), made of composite material 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 blade is proposed comprising a three-dimensional fiber reinforcement densified by a matrix, the fiber reinforcement comprising a first skin and a second skin facing each other, the first skin and the second skin each having an internal face delimiting between them an internal housing, the blade further comprising a set of stiffeners monolithic with the first skin and the second skin and extending through the internal housing while being fixed on the internal face of the first skin and the second skin so as to connect them, the internal housing having a lower limit adjacent to a root of the blade, a leading edge limit adjacent to a leading edge of the blade and a trailing edge limit adjacent to a trailing edge of the blade,all or part of the stiffeners extending into the internal housing from the lower limit to the leading edge limit or from the lower limit to the trailing edge limit.

[0013] The invention is advantageously completed by the following characteristics, taken alone or considering one of their technically possible combinations: - all or part of the stiffeners comprises a first portion extending radially from the lower limit of the internal housing and a second portion extending axially from the leading edge limit of the internal housing, - the blade further has a chord, the second portion of all or part of the stiffeners extending into the internal housing at an angle of between 0° and 70° relative to the chord at the leading edge limit of the internal housing, - the internal housing has a total height equal to a maximum distance between the lower limit and the upper limit, for example a total height between 20% and 80% of the total height of the blade, all or part of the stiffeners having a height strictly less than the total height of the internal housing, - the stiffeners have a volume between 2% and 50% of a volume of the internal accommodation, preferably between 5% and 25%, - the stiffeners have a thickness between 0.01 times the chord and 0.25 times the chord of the blade, the thickness of the stiffeners being able to vary in a radial direction at the lower limit, - two adjacent stiffeners have a spacing of between 0.01 and 0.5 times the blade chord, the spacing of the stiffeners being able to vary in a radial direction at the lower limit, - the stiffeners have a rectangular, circular, triangular or trapezoidal section, - stiffening pads are placed between the stiffeners, the height of each stiffening pad being at most equal to 10% of the height of the stiffeners, - the stiffeners also include fibrous bars obtained by three-dimensional weaving and densified by the matrix.

[0014] The invention also relates to a fan comprising a rotor or stator blade comprising blades as above, distributed circumferentially around an axis of revolution. In this fan, the stiffeners can extend at an angle relative to the axis of revolution of between 0° and 180°, preferably between 45° and 135°, the angle being able to vary in a direction radial to the axis of revolution.

[0015] Finally, the invention covers 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 on the casing of the propulsion system. DESCRIPTION OF FIGURES

[0016] 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:

[0017] [Fig.l] schematically represents an example of an engine including an unducted fan;

[0018] [Fig.2] illustrates an example of an aircraft comprising engines according to one embodiment;

[0019] [Fig.3a] 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;

[0020] [Fig.3b] is a sectional view of the blade of [Fig.3a] in a plane normal to the blade extension axis;

[0021] [Fig.4] is a sectional view of a blade according to another embodiment, in a plane comprising the chord of the blade at the blade root and the extension axis of the blade.

[0022] Throughout the figures, similar elements bear identical references. DETAILED DESCRIPTION

[0023] In the following, the present description will relate more particularly to a fan blade 7, in a fan blade which may be a rotor or a stator, in order to simplify the description. This is not, however, limiting, the present 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 housing 23. The blade 7 is provided for a blade which thus preferably 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.This 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 comprises a single fan rotor), to the moving and / or fixed blades of a turbomachine type engine (comprising a shrouded fan rotor and OGV type blades) or to the moving blades of a turboprop (comprising a single fan rotor, or propeller).

[0024] 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.

[0025] 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.

[0026] The term “fan” will also be used in the remainder of the description, although the present disclosure applies mutatis mutandis to a propeller.

[0027] 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.

[0028] 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 foot is called a chord measured at the foot 8 of the blade 7 and a chord at the head is called a chord measured near the top 9 of the blade 7.

[0029] 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 the root 8 and stilt of the blade 7, respectively.

[0030] 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 of the fibrous reinforcement 20, is typically a plastic material, typically a polymer, for example epoxy, bis-maleimide or polyimide.

[0031] The blade portion 12 comprises two skins 21. The fiber reinforcement 20 is woven such that it comprises warp strands that extend continuously both inside the aerodynamically profiled blade portion 12 and inside the root area 8 of the blade 7. The fiber reinforcement 20 may be produced by weaving on a jacquard-type loom. During weaving, bundles of warp strands are arranged in several layers. Weft strands are interwoven with the warp strands so as to bind the different layers of warp strands together. The three-dimensional weave may be an “interlock” weave. “Interlock” refers to a weave pattern in which each layer of weft strands binds several layers of warp strands with all the strands of a single weft column having the same movement in the plane of the weave. Other types of three-dimensional weaving Known techniques may be used, such as those described in WO 2006 / 136755.

[0032] 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).

[0033] In the present application, by strand we mean any type of wire(s) forming in particular the fibrous reinforcement 20.

[0034] Preferably, each skin 21 comprises at least two layers of strands over the entire height of the blade 12, for example four layers.

[0035] 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 an internal housing 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, the internal housing 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 an internal housing 23 between the two skins 21.

[0036] The internal housing 23 can be obtained by creating a disconnection in the fiber reinforcement, that is to say by not connecting the warp strands of several successive warp layers. The internal faces 22 of the skins 21 are therefore directly connected to each other at a junction 24 which delimits the internal housing 23. The internal housing 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 internal housing 23 therefore has 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 internal housing 23 which is adjacent to Péchasse and to the root 8 of the blade 7.

[0037] 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 further comprises a set of stiffeners 30 extending into the internal housing 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 internal housing 23, from the internal face 22 of one of the skins 21 to the internal face 22 opposite the other of the skins 21. All or part of the stiffeners 30 extend in the internal housing 23 from the lower limit 26 to the leading edge limit 27 or to the trailing edge limit 28 of the internal housing 23. The stiffeners 30 thus contribute to the mechanical behavior of the blade 12 in addition to their structural role of connecting the skins 21.

[0038] The stiffeners 30 are furthermore monolithic with the skins 21 and their constituent material is identical to the material of 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 stiffeners 30, 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. The mechanical behavior of the blade 7 is furthermore not modified since the stiffeners 30 ensure the connection between the skins 21 of the fiber reinforcement 20.

[0039] 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 in the same 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 internal housing 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.

[0040] 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 formed in the spaces left free by a core inserted in the blade 7. The fibrous reinforcement 20 comprising the core is then placed in a mold. Matrix is ​​then injected into the mold so as to impregnate the fibrous reinforcement 20 while forming the stiffeners 30. Each stiffener 30 is configured so as to put the junction 24 (limit between the skins 21 and the internal housing 23) and the lower limit 26 of the internal housing 23 into fluid communication, 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 through the lower limit during its dissolution.

[0041] The stiffeners 30 may comprise in particular a first portion and a second portion. The first portion is contiguous to the lower limit 26 of the cavity and has a length of at most 60% of the total curvilinear length of the stiffener 30 in question, the curvilinear lengths being measured in the plane comprising the chord of the blade at the blade root and the Y axis. The total curvilinear length is measured from the lower limit 26 to the end of the stiffener 30 in question, that is to say in contact with the leading edge limit 27 or the trailing edge limit 28. The first portion extends substantially parallel to the Y axis of the blade 7 from the lower limit 26 of the internal housing 23, that is to say along an axis which extends substantially radially relative to the X axis of the fan, in order to improve the bending resistance of the blade 7.

[0042] The second portion is contiguous to the leading edge limit 27 or the trailing edge limit 28, depending on the configuration of the stiffener 30 considered, and has a curvilinear length of at most 60% of the total curvilinear length of the stiffener 30 considered. The second portion extends in a substantially axial direction relative to the axis X of the fan, in order to improve the torsional resistance of the blade 7.

[0043] The second portion of all or part of the stiffeners 30 extending into the internal housing 23 can form an angle of between 0° and 70° with the chord at the root at the leading edge limit of the internal housing 23 in order to optimize the torsional resistance of the blade 7.

[0044] The stiffeners 30 extend at an angle 0 relative to the axis X of revolution of between 0° and 180°, preferably between 45° and 135°, the angle being able to vary in a direction radial to the axis X of revolution. In particular, the angle 0 can vary between 75° and 105° on the first portion of the stiffeners 30. In a plane normal to the axis Y of extension of the blade, each stiffener 30 comprises an upstream limit 33 facing the leading edge 10 and a downstream limit 34 facing the trailing edge 11. The tangent at each upstream limit 33 and at each downstream limit 34 respectively forms an angle 0amont and 0avai with respect to the camber curve Z, or skeleton curve, of the aerodynamic profile of the blade 7. The angles 0amont and 0avais are between 20° and 160°, preferably between 60° and 120°.The upstream limits 33 and the downstream limits 34 are preferably parallel and normal to the skins 21 so that the connection formed by the stiffeners 30 between the two skins 21 has better shear resistance.

[0045] The internal housing 23 has a total height defined as a maximum distance between the lower limit 26 and the upper limit 25 of the cavity. The total height of the internal housing 23 is between 20% and 80%, preferably between 35% and 70% of the height of the blade 7. The number of stiffeners 30 is between 2 and 30, preferably between 4 and 15 to obtain a blade 7 of sufficient stiffness while preserving a reduced mass. For this same objective, the stiffeners 30 have a volume comprised between 2% and 50% of a volume of the internal housing 23, preferably between 5% and 25% of the volume of the internal housing 23. In particular, the stiffeners 30 have a thickness comprised between 0.01 times the chord and 0.25 times the chord of the blade 7, the thickness of the stiffeners 30 being able to vary in a radial direction at the lower limit 26, that is to say along the Y axis. Two stiffeners 30 adjacent have a spacing of between 0.01 and 0.5 times the chord of the blade 7, the spacing of the stiffeners 30 being able to vary in a radial direction at the lower limit 26, that is to say along the Y axis. These parameters make it possible to limit the total mass of the blade 7 while improving the mechanical strength.

[0046] The stiffeners 30 have a section, corresponding to the surface of a stiffener 30 in a plane normal to the Y axis, which can be rectangular, circular, triangular, trapezoidal, etc.

[0047] Optionally, the skins 21 are further connected by stiffening pads 31 placed between the stiffeners 30, a width of each stiffening pad 31 being at most equal to 10% of the total height of the longest stiffener 30, the width of each stiffening pad 31 being measured as the greatest distance between two points of the stiffening pad 31 in the plane comprising the chord of the blade at the blade root and the Y axis. The stiffening pads 31 have a section, corresponding to the surface of a stiffener 30 in a plane normal to the Y axis, which can be rectangular, circular, triangular, trapezoidal, etc. The stiffening pads 31 make it possible to increase the rigidity of the blade 7 by limiting the deformations of the skins 21 throughout the volume of the internal housing 23.

[0048] Optionally, the stiffeners 30 further comprise fibrous bars (not shown in the figures) obtained by three-dimensional weaving and densified by the matrix, in a similar manner to the fibers of the fibrous reinforcement 20. The fibrous bars are inserted into the spaces left free of the cores before introduction into the mold and are impregnated at the same time as the fibrous reinforcement 20, in a similar manner to the formation of a stiffener 30 not comprising a fibrous bar. The fibrous bars make it possible to obtain much more rigid stiffeners 30, which further improves the mechanical properties of the blade 7. Manufacturing process

[0049] A blade 7 according to the invention can be obtained using the following manufacturing method. This is not, however, limiting, other methods can be envisaged for the production of such a blade 7.

[0050] During a step SI, the fibrous reinforcement 20 is produced by three-dimensional weaving on a jacquard-type loom. During weaving, bundles of warp strands are arranged in several layers of several hundred strands each. Weft strands are interlaced with the warp strands so as to bind the different layers of warp strands together. Preferably, the three-dimensional weaving is an “interlock” weave.

[0051] The step of weaving the raw fiber reinforcement 20 (or preform) comprises the weaving of the two skins 21, which together form an upper part of the blade 7 which comprises the tip 9 and a lower part comprising the junction 24 and delimits the cavity. The portion of the fibrous reinforcement 20 intended to form the upper part of the skins 21 is woven by interlacing all the warp strands necessary for producing the fibrous reinforcement 20. Once the fibrous reinforcement 20 has reached the junction 24, a delinking is initiated between two successive layers of warp strands in order to form the cavity. Then, the two portions of fibrous reinforcement 20 forming the parts of the skins 21 which delimit the cavity are woven in parallel with each other, being separated by the delinking zone. The skins 21 however remain woven together in the zone intended to form the leading edge 10 and the trailing edge 11 of the blade 7 in order to close the cavity at these edges. In this way, each of the two portions of fiber reinforcement 20 forming the cavity comprises warp strands which extend inside the portion of fiber reinforcement 20 forming the upper part of the blade 7.

[0052] Reference may be made, as an example, to document EP2588758 in the name of the applicant for further details on the production of disconnections.

[0053] Alternatively, several fibrous preforms may be woven separately, the preforms then being assembled together so as to form the upper part and the lower part of the fibrous reinforcement 20 and to delimit the cavity.

[0054] During a step S2, a core is inserted into the cavity. The core is configured to fill the areas of the cavity intended to separate the stiffeners 30. Its shape is therefore complementary to the shape of the stiffeners 30.

[0055] Depending on the shape and number of stiffeners 30, a single, monolithic core may be used, in which case the core comprises through passages whose shape and arrangement correspond to the shape and arrangement of the stiffeners 30. Alternatively, the core may be segmented and comprise several parts, the through passages intended to form the stiffeners 30 then being formed by the spacings between the different core parts and / or through holes formed in one or more core parts.

[0056] The core 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 of the blade 7. The material constituting the core is chosen so that its solvent is neutral with respect to the materials constituting the fibrous reinforcement 20 (strands and matrix), in order not to damage the blade 7 during its dissolution.

[0057] For example, the core may comprise a thermoplastic polymer ST 130 which dissolves in a basic bath at 70°C. A thermoplastic polymer core has the advantage of being able to be produced by 3D printing, which allows the use of a monolithic core and / or the implementation of stiffener shapes 30 whose geometry is more complex.

[0058] During a step S3, the fibrous reinforcement 20 comprising the core is placed in a mold. The matrix is ​​then injected into the mold so as, on the one hand, to fill the through passages to form the stiffeners 30 and, on the other hand, to embed the fiber reinforcement 20 in the matrix.

[0059] 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, which is still housed in the cavity and fills the space in the cavity which is not occupied by stiffeners 30.

[0060] During a step S4, the core is dissolved under conditions adapted to the type of material chosen for the core (thermoplastic polymer / basic bath at 70°C) consistent with the material of the fibrous reinforcement 20. The solvent can for example be projected against the lower limit 26 of the cavity in order to gradually dissolve the core. Alternatively, the blade 7 can simply be immersed in a bath of solvent.

[0061] The dissolution of the core and the evacuation of the solvent are notably enabled by the configuration of the stiffeners 30, the shape and spacing of which enable the solvent to reach the junction 24 between the two skins 21 from the lower limit 26 of the cavity. The solvent can thus reach the entire core and dissolve it.

[0062] After dissolution of the core, the stiffeners 30 are spaced from each other by air blades in place of the core.

[0063] Finishing operations (trimming, application of a metal shield, etc.) can also be carried out. These operations are carried out after injection of the matrix, before or after dissolution of the core.

Claims

Claims

1. 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) delimiting between them an internal housing (23), the blade (7) further comprising a set of stiffeners (30) monolithic with the first skin (21) and the second skin (21) and extending through the internal housing (23) while being fixed on the internal face (22) of the first skin (21) and the second skin (21) so as to connect them, the internal housing (23) having a lower limit (26) adjacent to a root (8) of the blade (7), a leading edge limit (27) adjacent to a leading edge (10) of the blade (7) and a trailing edge boundary (28) adjacent to a trailing edge (11) of the blade (7),all or part of the stiffeners (30) extending in the internal housing (23) from the lower limit (26) to the leading edge limit (27) or from the lower limit (26) to the trailing edge limit (28).,

2. A blade (7) according to claim 1, wherein all or part of the stiffeners (30) comprises a first portion extending radially from the lower limit (26) of the inner housing (23) and a second portion extending axially from the leading edge limit (27) of the inner housing (23).

3. A blade (7) according to claim 2 further having a chord, the second portion of all or part of the stiffeners (30) extending into the internal housing (23) at an angle of between 0° and 70° relative to the chord at the leading edge limit (27) of the internal housing (23).

4. Blade (7) according to one of claims 1 to 3, in which the internal housing (23) has a total height equal to a maximum distance between the lower limit (26) and the upper limit (25), for example a total height between 20% and 80% of the total height of the blade (7), all or part of the stiffeners (30) having a height strictly less than the total height of the internal housing (23).

5. Blade (7) according to one of claims 1 to 4, in which the stiffeners (30) have a volume of between 2% and 50% of a volume of the internal housing (23), preferably between 5% and 25%.

6. Blade (7) according to one of claims 1 to 5 further having a chord, in which the stiffeners (30) have a thickness of between 0.01 times the chord and 0.25 times the chord of the blade (7), the thickness of the stiffeners (30) being able to vary in a radial direction at the lower limit (26).

7. A blade (7) according to claim 6, wherein two adjacent stiffeners (30) have a spacing of between 0.01 and 0.5 times the chord of the blade (7), the spacing of the stiffeners (30) being able to vary in a radial direction at the lower limit (26).

8. Blade (7) according to claim 7, in which the stiffeners (30) have a rectangular, circular, triangular or trapezoidal section.

9. Blade according to one of claims 1 to 8, further comprising stiffening pads (31) placed between the stiffeners (30), a height of each stiffening pad (31) being at most equal to 10% of a height of the stiffeners (30).

10. Blade (7) according to one of claims 1 to 9, in which the stiffeners (30) further comprise fibrous bars obtained by three-dimensional weaving and densified by the matrix.

11. Fan (3) comprising a rotor or stator blade comprising blades (7) distributed circumferentially around an axis of revolution according to one of claims 1 to 10.

12. Blower (3) according to claim 11, in which the stiffeners (30) extend at an angle relative to the axis of revolution of between 0° and 180°, preferably between 45° and 135°, the angle being able to vary in a direction radial to the axis of revolution.

13. Propulsion system (1) comprising a fan (3) according to one of claims 11 to 12 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 of the propulsion system (1).

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