Composite material blade with reinforced strut

Abstract

Composite material blade with reinforced strut. A composite material blade (10) comprises a matrix-densified fibrous reinforcement, the blade having, along a span direction, a foot (13), a strut (12), and an airfoil (11), the fibrous reinforcement comprising a fibrous preform having a three-dimensional weave between a plurality of warp yarns and a plurality of weft yarns. The strut preform portion of the fibrous preform has a weft texture smaller than the weft texture of the foot preform portion and the airfoil preform portion of said fibrous blank. Figure for the abbreviation: Fig. 15.

Description

Title of the invention: Composite material blade with reinforced strut technical field

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

[0002] Turbopropeller blades are generally made of metallic material. While metallic blades have good mechanical strength, they have the disadvantage of having a relatively large mass.

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

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

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

[0006] For this purpose, the feet of the new generation blades have an axisymmetric or substantially axisymmetric shape and reduced dimensions such as the blade disclosed in document WO 2023 / 209289 which is made entirely from a fibrous reinforcement having a three-dimensional or 3D weave and densified by a matrix.

[0007] On a shrouded engine, the retention housing serves to contain the blade(s) in the event of blade loss following an impact with an object, such as in the case of bird ingestion. Conversely, on an unshrouded engine, it is necessary to ensure a virtually unlimited blade lifespan. Cyclic fatigue loading in bending has a significant impact on the lifespan of new-generation composite blades (axisymmetric or substantially axisymmetric shape and reduced blade root dimensions). Indeed, the bending load caused by impacts with objects induces, in particular, tensile stresses at the level of the Péchasse's leave of the dawn. In addition, the feet of the new generation blades can be integrated into the rotor disc using metal shells, resulting in an additional mechanical load in circumferential compression.

[0008] If the 3D woven fibrous reinforcement gives the aerodynamic profile part of the blade (vein zone) very high resistance to impacts, however it has a lower resistance to mechanical loads in tension and compression at the level of Péchasse de l'aube. Description of the invention

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

[0010] To this end, the present invention proposes a method for manufacturing a blade made of composite material, the method comprising: - the weaving of a one-piece fibrous blank comprising a foot section, an aerodynamic profile section and a stilt section connecting the foot section to the aerodynamic profile section, the foot section of the fibrous blank comprising a central debonding delimiting an internal foot housing opening at a free end of said foot section, the aerodynamic profile section and the foot section being woven according to a three-dimensional weave between a plurality of warp yarns extending along a longitudinal direction corresponding to the span direction of the blade to be manufactured and a plurality of weft yarns extending along a transverse direction corresponding to the chord direction of the blade to be manufactured, - the shaping of the fibrous blank to obtain a one-piece fibrous preform with an aerodynamic profile preform part, a foot preform part and a stilt preform part, the shaping including the positioning of an insertion element in the internal foot housing so as to form the foot preform part, - the densification of the fibrous preform by a matrix to obtain a blade made of composite material having a fibrous reinforcement consisting of the fibrous preform and densified by the matrix, and forming a single piece with a foot, a stilt and an aerodynamic profile, characterized in that the stilt part of the fibrous blank has a weft texture lower than the weft texture of the foot part and the aerodynamic profile part of said fibrous blank.

[0011] The process of the invention thus makes it possible to produce a blade with a composite base that is both compact and perfectly adapted to withstand the various mechanical loads described above. Indeed, the reduction of the texture The weave in the strut section allows the behavior to approximate that of a unidirectional fiber reinforcement and to locally impart to the fibrous reinforcement of the final blade mechanical properties similar to those of a unidirectional fiber reinforcement or ply. This increases the resistance at the strut of the final blade to tensile and compressive mechanical loads, significantly increasing the blade's lifespan, particularly with respect to bending fatigue loading cycles.

[0012] Furthermore, by maintaining a three-dimensional weave in the foot portion of the fibrous blank, it is possible to retain drapability for the strut portion even when it lacks weft threads. This also allows for maintaining useful mechanical strength in the weft direction under compression, particularly in the span of the blade foot.

[0013] According to one embodiment of the invention, the stilt portion of the fibrous blank is devoid of weft yarns so as to comprise only unidirectional plies of warp yarns. In this case, the portion of the fibrous reinforcement of the blade present at the stilt has the same behavior as a unidirectional reinforcement.

[0014] According to another embodiment of the invention, an external portion of the stilt part of the fiber blank is devoid of weft yarns so as to comprise only unidirectional plies of warp yarns in said external portion, while an internal portion of the stilt part comprises weft yarns woven with warp yarns. This makes it possible to limit the reduction in cross-section at the stilt part of the fiber blank while maintaining a gain in mechanical strength at the stilt due to the presence of unidirectional plies in an external portion of the stilt part of the fiber blank.Furthermore, retaining weft yarns on a certain proportion of the stilt portion of the fiber blank allows for a preform with better structure that is easier to handle without risk of damage, including for the portion of the fiber blank that consists only of unidirectional plies, i.e., without weft yarns.

[0015] According to another embodiment of the method of the invention, the stilt portion and the foot portion of the fibrous blank comprise one or more disconnections extending around the central disconnection of the foot portion of the fibrous blank. This makes it possible, in particular, to form several independent portions, each having its own mechanical characteristics.

[0016] According to a particular feature of the process of the invention, during the shaping of the fibrous blank, at least a portion of the warp yarns in the stilt portion of the fibrous blank is oriented in at least one determined direction different from the direction of the warp yarns present in the foot preform portion and in the preformed part of the profile. This further strengthens the mechanical strength at the level of the blade's strut because the warp threads can be oriented along one or more directions corresponding to the direction(s) of application of the mechanical forces.

[0017] According to another particular feature of the method of the invention, it further comprises the placement of an external shell around the preform part of the foot or the foot of the blade.

[0018] The invention also relates to a blade made of composite material comprising a fibrous reinforcement densified by a matrix, the blade comprising, along a span direction, a foot, a stile and an aerodynamic profile, the fibrous reinforcement comprising a fibrous preform having a three-dimensional weave between a plurality of warp yarns extending along the span direction and a plurality of weft yarns extending along a chord direction of the blade, the fibrous preform comprising a portion of the foot preform present in the foot, a portion of the stile preform present in the stile and a portion of the aerodynamic profile preform present in the aerodynamic profile, the portion of the foot preform of the fibrous preform comprising a central debonding delimiting an internal foot housing forming a cavity in which an insertion element is present,characterized in that the stilt preform portion of the fibrous preform has a weft texture inferior to the weft texture of the foot preform portion and the aerodynamic profile preform portion of said fibrous blank.

[0019] As previously stated, the reduction of the weft texture in the part of the Péchasse fibrous reinforcement makes it possible to approach the behavior of a unidirectional fibrous reinforcement and to locally give the fibrous reinforcement of the blade mechanical properties similar to those of a unidirectional fibrous reinforcement or ply, which makes it possible to significantly increase the life of the blade in particular with regard to bending fatigue loading cycles.

[0020] According to one embodiment of the blade of the invention, the preform portion of the stilt is devoid of weft yarns so as to comprise only unidirectional plies of warp yarns. In this case, the portion of the fibrous reinforcement of the blade present at the stilt has the same behavior as a unidirectional reinforcement.

[0021] According to another embodiment of the blade of the invention, an external portion of the stilt preform part is devoid of weft yarns so as to comprise only unidirectional folds of warp yarns in said external portion while an internal portion of the stilt preform part comprises weft yarns woven with warp yarns.

[0022] According to another embodiment of the blade of the invention, the preform part The stilt and the foot preform include one or more disconnections extending around the central disconnection of the foot preform. This allows, in particular, the formation of several independent sections in the fibrous reinforcement, each with its own mechanical characteristics.

[0023] According to a particular feature of the blade of the invention, at least a portion of the warp threads in the stilt preform portion is oriented in at least one determined direction different from the direction of the warp threads in the foot preform portion and the airfoil preform portion. This further strengthens the mechanical strength at the stilt end of the blade because the warp threads can be oriented along one or more directions corresponding to the direction(s) of application of the mechanical forces.

[0024] According to another particular feature of the blade of the invention, the foot of the blade further comprises a metal shell.

[0025] The invention further covers an aeronautical engine comprising a plurality of blades or propeller blades according to the invention and an aircraft comprising at least one such engine. Brief description of the drawings

[0026] [Fig-1] Fig. 1 is a schematic view illustrating the 3D weaving of a blank fibrous material for manufacturing a blade,

[0027] [Fig.2] [Fig.2] is an enlarged cross-sectional view in the weft direction of a set of yarn layers showing the formation of two unbonds in the foot part of the blank of [Fig.1] along a section plane II-II,

[0028] [Fig.3] The [Fig.3] is an enlarged cross-sectional view in the weft direction of a set of yarn layers showing the formation of two unbonds in the foot part of the blank of the [Fig.1] along a III-III section plane,

[0029] [Fig.4] The [Fig.4] is a schematic perspective view showing the shaping of a part of the foot preform in the fibrous blank of the [Fig.1],

[0030] [Fig.5] The [Fig.5] is a schematic perspective view showing a fibrous blade preform obtained from the fibrous blank of the [Fig.1],

[0031] [Fig.6] [Fig.6] is a schematic cross-sectional view of a portion of the fibrous blank of [Fig.1] showing a part of the stilt according to one embodiment,

[0032] [Fig.7] [Fig.7] is a partial schematic view of a twist-free fibrous blade preform of the stilt preform portion,

[0033] [Fig.8] Fig.8 is a partial schematic view of a fibrous blade preform with twist of the stilt preform portion,

[0034] [Fig.9] Fig.9 is a schematic cross-sectional view of a portion of the fibrous blank of Fig.1 showing part of a stilt according to another embodiment,

[0035] [Fig. 10] [Fig. 10] is a schematic cross-sectional view of a portion of the fibrous blank of [Fig. 1] showing part of a stilt according to another embodiment,

[0036] [Fig. 11] [Fig. 11] is a schematic cross-sectional view of a portion of the fibrous blank of [Fig. 1] showing part of a stilt according to another embodiment,

[0037] [Fig. 12] [Fig. 12] is a schematic cross-sectional view of a portion of the fibrous blank of [Fig. 1] showing part of a stilt according to another embodiment,

[0038] [Fig. 13] [Fig. Figure 13] is a schematic exploded perspective view showing an injection mold and the placement of the fibrous preform inside it according to an embodiment of the invention,

[0039] [Fig. 14] Fig. 14 is a schematic perspective view showing the injection tooling of the closed Fig. 13,

[0040] [Fig. 15] [Fig. 15] is a schematic perspective view of a composite material blade obtained according to an embodiment of the invention. Description of embodiments

[0041] The invention is generally applicable to various types of propeller blades used in aircraft engines. The invention finds an advantageous, but not exclusive, application in large propeller blades intended for integration into pivoting or variable-pitch systems. Such propeller blades are generally equipped with a base that is both compact (small footprint) and offers good resistance to tensile, bending, and circumferential compression forces. The blade according to the invention can, in particular, be 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.

[0042] In the following description, the embodiments are described in relation to turboprop turbine blades. However, the embodiments also apply to aircraft propeller blades.

[0043] Fig. 1 shows very schematically a fibrous rough 100 intended to form the fibrous preform of a blade to be produced.

[0044] The fibrous blank 100 is obtained, as schematically illustrated in [Fig. 1], by three-dimensional (3D) weaving carried out in a known manner using a Jacquard-type loom on which a bundle of warp yarns 101 or strands is arranged in a plurality of layers of several hundred yarns each, the warp yarns being linked by weft yarns 102. The fibrous blank 100 intended to form the fibrous reinforcement of the final blade is woven in a single piece, the blank extending in a longitudinal direction DL, corresponding to the span direction of the blade to be manufactured and to the direction in which the warp yarns 101 extend, between a lower part 100c and an upper part lOOd and in a transverse direction Dt, corresponding to the chord direction of the blade to be manufactured and the direction in which the weft yarns extend, between a front edge 100a and a rear edge 100b. The fibrous blank 100 comprises an airfoil part 111 defining two faces 11 le and 11 If intended to form respectively the extrados and intrados faces of the blade, a foot part 113 intended to subsequently form a blade foot and a strut part 112 present between the foot part 113 and the airfoil part 111, the strut part 112 connecting the foot part 113 to the airfoil part 111.

[0045] The stilt part 112 extends outside the aerodynamic profile part 111 along the longitudinal direction DL and set back from the front and rear edges 100a and 100b along the transverse direction DT.

[0046] In the illustrated example, the 3D 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.

[0047] Other known types of three-dimensional weaving may be used, such as those described in WO 2006 / 136755. This document describes in particular the production by weaving in one piece of fibrous reinforcement structures for parts such as blades having a first type of core armor and a second type of skin armor which make it possible to confer both the mechanical and aerodynamic properties expected for this type of part.

[0048] The fibrous blank according to the invention can be woven in particular from carbon fiber yarns or ceramic such as silicon carbide.

[0049] As the fibrous blank, whose thickness and width vary, is woven, a certain number of warp yarns are not woven, which makes it possible to define the desired contour and thickness, continuously variable, of the blank 100. An example of evolving 3D weaving, in particular allowing the thickness of the blank to be varied between a first edge intended to form the leading edge and a second edge of lesser thickness intended to form the trailing edge, is described in US document 2006 / 257260.

[0050] During weaving, a central unbinding 106 is made within the foot portion 113 of the fibrous blank 100 between two successive layers of warp yarns. The central unbinding 106 extends along a plane parallel to the surface of the fibrous blank and over an unbinding zone delimited by a contour 106a locally separating the foot portion 113 into two woven sections 114 and 115. Furthermore, the unbinding 106 extends in the transverse direction between a first lateral edge 1120 and a second lateral edge 1121 and set back from these edges (i.e., the unbinding 106 does not open onto the lateral edges 1120 and 1121) so as to maintain connecting portions 105 and 107 adjacent respectively to the first and second lateral edges 1120 and 1121. The central connection 106 also opens onto the free lower end 1122 of the foot portion 113. The connection 106 thus forms an internal recess 140 in the foot portion 113 which is accessible via the free lower end 1122. The internal recess 140 is intended to receive an insertion element during the shaping of the fiber blank as explained below.

[0051] A 3D interlock weave of the blank 100 is schematically shown in [Fig. 2]. [Fig. 2] is an enlarged partial view of a warp cross-section in a portion of the blank 100 comprising the unlinking zone 106 (section II-II in [Fig. 1]). In this example, the blank 100 comprises eight layers of warp yarns 101 extending substantially in the longitudinal direction DL. In [Fig. 2], the eight layers of warp yarns are linked by weft yarns Ti to T8 in the linking zones 105 and 107 of the foot portion 113 of the fiber blank 100, the weft yarns extending substantially in the transverse direction DT. At the level of the unlinking 106, the woven portion 115 comprises four layers of warp yarns 101 linked together by four weft yarns Ti to T4 while the woven portion 114 comprises the four layers of warp yarns forming the set of yarn layers 109 are linked by four weft yarns T5 to T8.

[0052] In other words, the fact that the weft yarns Ti to T4 do not extend into the warp yarn layers of the woven portion 114 and that the weft yarns T5 to T8 do not extend into the warp yarn layers of the woven portion 115 ensures the unbinding 106 which separates the woven portions 114 and 115.

[0053] In the weaving example shown in [Fig.2], the weft yarns Ti to T4, on the one hand, and the weft yarns T5 to T8, on the other hand, are respectively arranged on each side of the unlinking 106, the weft yarns Ti to T4 linking the first four layers of warp yarns forming the woven portion 115 and the weft yarns T5 to T8 linking the last four layers of warp yarns forming the woven portion 114.

[0054] According to an alternative embodiment illustrated in [Fig. 3] (section III-III in [Fig. 1]), a first portion of weft yarn layers crosses a second portion of weft yarn layers in a zone of the fiber blank 100 located near the unlinking 106 along the transverse direction DT. The yarns of the first portion of weft yarns 102 extend on one side of the unlinking 106 along the transverse direction DT, while the yarns of the second portion of yarns from the plurality of weft yarn layers 102 extend on the other side of the unlinking 106 along the transverse direction DT. More specifically, one or more weft yarns 102 linking warp yarn layers forming a set of yarn layers 108 in the linking zone 105 are used to link warp yarn layers forming a set of layers of yarns 109 in the bonding zones 107 and vice versa. In the example illustrated in [Fig. 3], the weft yarns T3 and T4, bonding layers of warp yarns 101 of the set of yarn layers 108 in the first bonding zone 105 are deflected at the beginning or upstream of the unbinding 106 along the transverse direction DT to bond layers of warp yarns 101 of the set of yarn layers 109. Similarly, the weft yarns T5 and T6, bonding layers of warp yarns 101 of the set of yarn layers 109 in the first bonding zone 105 are deflected at the beginning or upstream of the unbinding 106 along the transverse direction DT to bond layers of warp yarns 101 of the set of yarn layers 108.After the unbinding 106, the weft yarns T3 and T4 are again deflected at the end or downstream of the unbinding 106 along the transverse direction DT, that is, upon their entry into the second binding zone 107, to bind layers of warp yarns 101 of the set of yarn layers 109, while the weft yarns T5 and T6 are again deflected at the end or downstream of the unbinding 106 along the transverse direction DT, that is, upon their entry into the second binding zone 107, to bind layers of warp yarns 101 of the set of yarn layers 108. The crossing of the weft yarns T3 and T4 and the weft yarns T5 and T6 upstream and / or downstream of the unbinding 106 along the transverse direction DT improves the strength of the fiber blank in the zone of unlinking. According to one embodiment, some of the weft yarns may cross only upstream or downstream of the unlinking 106 along the transverse direction DT.

[0055] Once the weaving is complete, the non-woven yarns present around the fibrous blank 100 are cut to extract said blank as illustrated in [Fig.4].

[0056] According to the invention, the stilt portion 112 of the fiber blank 100 has a weft structure smaller than the weft structure of the foot portion 113 and the airfoil portion 111 of the fiber blank 100. The weft structure corresponds to the spacing between two columns of weft yarns. In other words, the stilt portion 112 comprises a number of weft yarns per unit length along the longitudinal direction DL that is lower than the number of weft yarns present in the foot portion 113 and in the airfoil portion 111 for the same unit length. The number of weft yarns present in the stilt portion may be zero or almost zero. In this case, the stilt portion comprises only warp yarns that are not woven with weft yarns, thus forming unidirectional plies of warp yarns as described in detail below.When the stilt portion of the fibrous blank includes weft yarns, the ratio between the number of warp yarns and the number of weft yarns in the stilt portion is preferably 90 / 10.

[0057] In the case where the stilt part includes weft threads, these may be made up of yarns with a lower count and / or basis weight than the other weft yarns used in the rest of the fiber blank. The weft yarns present in the stilt section can be, for example, polyester yarns.

[0058] Reducing the weft structure in the strut section allows the behavior to approach that of a unidirectional fiber reinforcement and to locally impart to the fibrous reinforcement of the end blade mechanical properties similar to those of a unidirectional fiber reinforcement or ply. This increases the resistance at the strut of the end blade to tensile and compressive mechanical loads, thereby significantly increasing the blade's lifespan, particularly with respect to bending fatigue loading cycles.

[0059] Furthermore, by maintaining a three-dimensional weave in the foot portion of the fibrous blank, it is possible to retain drapability for the strut portion even when it lacks weft yarns. This also allows for maintaining useful mechanical strength in the weft direction under compression, particularly in the span of the blade foot.

[0060] Figure 6 schematically illustrates a portion of the fiber blank 100 showing a part of the strut 112 according to one embodiment. Figure 6 corresponds to a half-section at the level of the foot portion 113, the strut 112, and a lower portion of the airfoil portion 111 of the fiber blank 100 along the reference frame VLVI in Figure 4. In this embodiment, the strut portion of the fiber blank is devoid of weft yarns 102 and consists only of non-woven warp yarns 101 forming unidirectional plies of warp yarns. In this embodiment, the portion of the fibrous reinforcement of the blade present at the strut behaves identically to that of a unidirectional reinforcement.

[0061] Figure 9 schematically illustrates a portion of the fibrous blank 100 showing part of the stilt 112 according to another embodiment. Figure 9 corresponds to a half-section at the level of the foot portion 113, the stilt 112 and a lower part of the aerodynamic profile portion 111 of the fibrous blank 100 along the reference IX-IX on Figure 4. In this embodiment, the stilt part of the fibrous blank has a weft texture lower than the weft texture in the foot part 113 and in the aerodynamic profile part 111. Although the stilt part 112 has a 3D weave here, the spacing between the weft columns is much greater than in the other 3D woven parts of the blank, which allows for a mechanical behavior closer to a unidirectional reinforcement than to a 3D woven reinforcement.The ratio between the number of warp threads and the number of weft threads in the stilt section is preferably 90 / 10. The presence of 102 weft threads, even widely spaced, allows for a... more regular spacing between warp threads 101.

[0062] According to a particular feature of the invention, only a portion of the stilt part may be devoid of weft threads. By way of non-limiting example, [Fig. 10] schematically illustrates a portion of the fibrous blank 100 showing a stilt part 112 according to another embodiment. [Fig. 10] corresponds to a half-section at the level of the foot portion 113, the stilt 112, and a lower portion of the aerodynamic profile portion 111 of the fibrous blank 100 along the reference XX in [Fig. 4]. In this embodiment, the stilt part 112 of the fibrous blank includes an external portion 1121 which is devoid of weft yarns 102 so as to comprise only unidirectional folds of warp yarns 101 and an internal portion 1122 comprising weft yarns 102 woven with warp yarns 101.In this embodiment, the part of the fibrous reinforcement in the blade's skin present at the Péchasse level includes an external portion having a behavior identical to that of a unidirectional reinforcement.

[0063] According to another particular feature of the invention, one or more disjunctions can be formed in the stilt part 112 and in the foot part 113.

[0064] By way of non-limiting example, [Fig. 11] schematically illustrates a portion of the fiber blank 100 showing a part of the strut 112 according to another embodiment. [Fig. 11] corresponds to a half-section at the level of the foot portion 113, the strut 112, and a lower portion of the airfoil portion 111 of the fiber blank 100 along reference XLXI in [Fig. 4]. In this embodiment, the strut portion of the fiber blank is devoid of weft yarns 102 and consists only of non-woven warp yarns 101 forming unidirectional plies of warp yarns. In this case, the portion of the fibrous reinforcement of the blade present at the strut behaves identically to that of a unidirectional reinforcement.Furthermore, in this embodiment, the stilt part 112 and the foot part 113 of the fibrous blank include a debonding 122 which extends around the central debonding 106 of the foot part 113 of the fibrous blank and which separates the stilt part 112 and the foot part 113 into two independent portions 120 and 121.

[0065] By way of non-limiting example, [Fig. 12] schematically illustrates a portion of the fiber blank 100 showing a part of the stilt 112 according to another embodiment. [Fig. 12] corresponds to a half-section at the level of the foot portion 113, the stilt 112, and a lower part of the aerodynamic profile portion 111 of the fiber blank 100 along reference XIXII in [Fig. 4]. In this embodiment, the stilt portion 112 and the foot portion 113 of the fiber blank comprise two debonds 153 and 154 which extend around the central debond 106 of the foot portion 113 of the fiber blank and which separate the part stilt 112 and foot part 113 in three independent portions 150, 151 and 152. In portions 150 and 151 at the level of the stilt part 112, the warp yarns 101 are woven with weft yarns 102 but with a weft texture lower than the weft texture in the foot part 113 and in the aerodynamic profile part 111 while the portion 153 at the level of the stilt part 112 is devoid of weft yarns 102 and has only non-woven warp yarns 101 forming unidirectional folds of warp yarns.

[0066] Each independent portion formed in the stilt part by a debinding can be devoid of weft yarns or be woven with weft yarns but with a texture inferior to the weft texture of the foot part and the aerodynamic profile part of the fibrous blank.

[0067] The manufacturing of the blade continues with the shaping of the fibrous blank 100. In the example described here, the shaping of the foot portion 112 is carried out by separating the woven portions 114 and 115 and inserting an insert element 130 into the internal recess 140 formed by the debonding 106 as illustrated in [Fig. 4]. The insert element can, in particular, be made of metallic material or resin by additive manufacturing, for example.

[0068] A fibrous preform 200 is thus obtained comprising, along the longitudinal direction Dl, a portion of the foot preform 213 including the insertion element 130, a portion of the strut preform 212 and a portion of the airfoil preform 211 as shown in [Fig. 5]. The portion of the airfoil preform 211 extends along the transverse direction DT between a portion of the leading edge preform 21la and a portion of the trailing edge preform 211b.

[0069] As illustrated in [Fig.7], the warp threads 101 present in the preform part of stilt 212 extend along the longitudinal direction DL corresponding to the span direction of the final blade.

[0070] According to a particular feature, during the shaping of the fiber blank 100, all or part of the warp threads 101 of the stilt preform portion 212 of the fiber blank can be oriented in at least one determined direction different from the direction of the warp threads present in the foot preform portion 213 and in the airfoil preform portion 211 by applying a twist to the stilt preform portion. This makes it possible to orient the warp threads in the stilt preform portion along a direction of stress application and to further strengthen the mechanical strength of the final blade at the stilt under specific stresses.

[0071] By way of non-limiting example, [Fig. 8] shows a fibrous preform 200 in which the stilt preform portion 212, for example made from the stilt portion of [Fig. 6], has been subjected to twisting so as to orient the warp threads 101 following a different direction from the direction of the warp threads present in the foot preform part 213 and in the airfoil preform part 211, which extend along the longitudinal direction DL. The warp threads in the stilt preform part can, for example, form an angle of +45° or -45° with the warp threads present in the foot preform part 213 and in the airfoil preform part 211.

[0072] The warp threads of the stilt preform portion can also be oriented along several determined directions, each different from the direction of the warp threads present in the foot preform portion 213 and in the aerodynamic profile preform portion 211. To this end, the stilt portion of the fibrous blank includes one or more debondings allowing the formation of independent portions such as portions 120, 121, 150, 151 and 152 illustrated respectively in Figures 11 and 12. Each independent portion can be subjected to a twist in a determined direction in order to orient the warp threads of one portion in a different direction from that of the warp threads of another portion.For example, the warp threads of a first portion may form an angle of +45° with the warp threads present in the foot preform part and in the airfoil preform part, while the warp threads of a second portion may form an angle of -45° with the warp threads present in the foot preform part and in the airfoil preform part.

[0073] The next step is to densify the fibrous preform. Densifying the fibrous preform intended to form the fibrous reinforcement of the part to be manufactured consists of filling the porosity of the preform, throughout all or part of its volume, with the material constituting the matrix. This densification is carried out in a manner known per se using the liquid-based process (CVL). The liquid-based process consists of impregnating the preform with a liquid composition containing a precursor of the matrix material. The precursor is usually in the form of a polymer, such as a high-performance epoxy resin, possibly diluted in a solvent. The preform is placed in a mold that can be sealed tightly with a cavity having the shape of the final molded blade.Next, the mold is closed and the liquid matrix precursor (for example, a resin) is injected throughout the cavity to impregnate the entire fibrous part of the preform.

[0074] The transformation of the precursor into a matrix, namely its polymerization, is carried out by heat treatment, generally by heating the mold, after removal of any solvent and crosslinking of the polymer, the preform always being kept in the mold having a shape corresponding to that of the part to be produced.

[0075] In the case of the formation of a carbon or ceramic matrix, the heat treatment consists of pyrolyzing the precursor to transform the matrix into a The matrix is ​​either carbon or ceramic, depending on the precursor used and the pyrolysis conditions. For example, liquid ceramic precursors, particularly SiC, can be polycarbosilane (PCS), polytitanocarbosilane (PTCS), or polysilazane (PSZ) type resins, while liquid carbon precursors can be resins with relatively high coke content, such as phenolic resins. Several consecutive cycles, from impregnation to heat treatment, can be performed to achieve the desired degree of densification.

[0076] According to one aspect of the invention, particularly in the case of forming an organic matrix, the densification of the fibrous preform can be achieved by the well-known resin transfer molding (RTM) process. According to the RTM process, the fibrous preform is placed in a mold having the external shape of the part to be produced. A thermosetting resin is injected into the internal space of the mold containing the fibrous preform. A pressure gradient is generally established in this internal space between the point where the resin is injected and the resin discharge ports in order to control and optimize the impregnation of the preform by the resin.

[0077] As illustrated in [Fig.13], the injection of a liquid matrix precursor composition into the fibrous texture and its transformation into a matrix are here carried out in an injection tool 300 which includes a first shell 310 comprising in its center a first impression 311 corresponding in part to the shape and dimensions of the blade to be produced and a second shell 320 comprising in its center a second impression 321 corresponding in part to the shape and dimensions of the blade to be produced.

[0078] Once the tool 300 is closed as illustrated in [Fig. 14], the first and second cavities 311 and 321 of the first and second shells 310 and 320, respectively, together define an internal volume 301 having the shape of the blade to be produced, and in which the fiber preform 200 is placed. The fiber preform 200 can be compacted while the tool 300 is closed to obtain a specific fiber content in the preform. In this case, compaction pressure is applied to the shells 310 and 320, for example, by means of a press. The fiber preform can also be compacted in a separate tool before the preform is introduced into the injection mold.

[0079] The tooling 300 further includes means for injecting a liquid matrix precursor and transforming this precursor into a matrix. More specifically, in the example described here, the first shell 310 of the tooling 300 includes an injection port 313 for injecting a liquid matrix precursor composition into the fibrous preform, while the second shell includes a discharge port 323 for cooperating with a system of pumping for vacuuming the tooling and drawing air during injection. The injection tooling 300 also includes 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. 14]).

[0080] Once the tooling 300 is closed, the blade is molded by impregnating the preform 200 with a thermosetting resin, which is then polymerized by heat treatment. The well-known injection or transfer molding process known as RTM ("Resin Transfer Molding") is used for this purpose. According to the RTM process, a resin 360, for example a thermosetting resin, is injected via the injection port 313 of the first shell 310 into the internal volume occupied by the preform 200. The port 323 of the second shell 320 is connected to a pressurized discharge conduit (not shown in [Fig. 14]). This configuration establishes a pressure gradient between the lower part of the preform 200, where the resin is injected, and the upper part of the preform located near the port 323.In this way, the resin 360, injected approximately at the lower part of the preform, will progressively impregnate the entire preform as it circulates 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.

[0081] 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.

[0082] After injection and polymerization, the blade is demolded. The blade can be trimmed to remove excess resin, and the chamfers can be machined. No further machining is necessary since, as the part is molded, it meets the required dimensions.

[0083] The densification processes described above make it possible to produce, from the fibrous preform of the invention, mainly blades or propeller blades in organic matrix composite material (CMO), carbon matrix (C / C) and ceramic matrix (CMC).

[0084] As illustrated in [Fig. 15], a blade 10 is obtained formed of a fibrous reinforcement densified by a matrix which includes a foot 13 formed by the foot preform portion 213 of the fibrous preform 200, a stilt 12 formed by the preform portion The blade 10 comprises a stilt 212 and a blade 11 formed by the blade preform portion 211 of the fibrous preform 200. The blade 10 has a leading edge 1la and a trailing edge 11b corresponding respectively to the leading edge portions 21la and trailing edge portions 211b of the fibrous preform 200, as well as an upper surface 1le and an lower surface 1If. The foot 13 includes a cavity 14 formed by the internal housing 240 of the fibrous preform 200, the insertion element 130 being bonded inside said cavity 14. The blade 10 thus comprises a foot 13 which has a compact, axisymmetric shape suitable for integration into a rotation or propeller pitch change system and which, at its stilt 12, exhibits increased mechanical resistance to tensile and compressive mechanical loads.

[0085] According to a particular feature and as illustrated in [Fig. 15], an outer shell 15, for example made of metal, is fixed around the foot 13. The outer shell can be glued to the final blade 10 or added to the foot preform portion before its densification. The outer shell 15 has a height Hi5 less than or equal to the height H2b of the foot preform portion 213 ([Fig. 5]). In other words, the outer shell 15 covers the foot 13 but not the Péchasse 12. This simplifies the manufacture of the outer shell since it is not necessary to form a thin section for a part of the shell that would extend to the junction with the blade, i.e., at the Péchasse.

[0086] The loss of mechanical strength in torsion and bending at the level of the stilt due to the absence of a shell in this part of the blade is compensated here by the increased mechanical resistance of the fibrous reinforcement of the blade in the stilt part according to the invention.

Claims

Demands

1. A method for manufacturing a blade (10) made of composite material, the method comprising: - weaving a one-piece fibrous blank (100) comprising a foot portion (113), an airfoil portion (111), and a strut portion (112) connecting the foot portion to the airfoil portion, the foot portion (113) of the fibrous blank (100) comprising a central debonding (106) defining an internal foot housing (140) opening at a free end (1122) of said foot portion, the airfoil portion (111) and the foot portion (113) being woven in a three-dimensional weave between a plurality of warp yarns (101) extending along a longitudinal direction (DL) corresponding to the span direction of the blade to be manufactured and a plurality of weft yarns (102) extending along a transverse direction (DT) corresponding to the chord direction of the blade to be manufactured,- shaping the fibrous blank (100) to obtain a one-piece fibrous preform (200) with an aerodynamic profile preform portion (211), a foot preform portion (213), and a stilt preform portion (212), the shaping comprising the positioning of an insertion element (130) in the internal foot housing (140) so as to form the foot preform portion (213), - densifying the fibrous preform (200) with a matrix to obtain a blade (10) made of composite material having a fibrous reinforcement consisting of the fibrous preform (200) densified by the matrix, and forming a single piece with a foot, a stilt, and an aerodynamic profile, characterized in that the stilt portion (112) of the fibrous blank (100) has a weft texture smaller than the weft texture of the foot portion (113) and the aerodynamic profile portion (111) of said fibrous blank.

2. A method according to claim 1, wherein the stilt portion (112) of the fibrous blank (100) is devoid of weft yarns (102) so as to comprise only unidirectional plies of warp yarns.

3. A method according to claim 1, wherein an external portion (1121) of the stilt part (112) of the fibrous blank (100) is devoid of weft yarns (102) so as to comprise only unidirectional folds of warp yarns (101) in said outer portion while an inner portion (1122) of the stilt part comprises weft yarns (102) woven with warp yarns (101).

4. A method according to any one of claims 1 to 3, wherein the stilt portion (112) and the foot portion (113) of the fibrous blank (100) comprise one or more unties (114) extending around the central untie (106) of the foot portion (113) of the fibrous blank.

5. A method according to any one of claims 1 to 4, wherein, during the shaping of the fibrous blank (100), at least a portion of the warp yarns (101) of the stilt portion (112) of the fibrous blank is oriented in at least one determined direction different from the direction of the warp yarns present in the foot preform portion (213) and in the profile preform portion (211).

6. A method according to any one of claims 1 to 5, further comprising placing an external shell (15) around the foot preform portion (213) or the foot (13) of the blade (10).

7. Blade (10) of composite material comprising a matrix-densified fibrous reinforcement, the blade comprising, along a span direction, a foot (13), a stem (12), and an airfoil (11), the fibrous reinforcement comprising a fibrous preform (200) having a three-dimensional weave between a plurality of warp yarns (101) extending along the span direction and a plurality of weft yarns (102) extending along a chord direction of the blade, the fibrous preform (200) comprising a portion of the foot preform (213) present in the foot (13), a portion of the stem preform (212) present in the stem (12), and a portion of the airfoil preform (211) present in the airfoil (11), the portion of the foot preform (213) of the fibrous preform (200) comprising a central debond (106) delimiting an internal foot housing (140) forming a cavity (14) in which an insertion element (130) is present,characterized in that the stilt preform portion (212) of the fibrous preform has a weft texture inferior to the weft texture of the foot preform portion (213) and the aerodynamic profile preform portion (211) of said fibrous blank.

8. Blade according to claim 7, wherein the stilt preform portion (212) is devoid of weft yarns (102) so as to comprise only unidirectional folds of warp yarns (101).

9. Blade according to claim 7, wherein an internal portion of the stilt preform part (212) is devoid of weft yarns (102) so as to comprise only unidirectional plies of warp yarns (101) in said internal portion while an external portion of the stilt preform part comprises weft yarns (102) woven with warp yarns (101).

10. Blade according to any one of claims 7 to 9, wherein the stilt preform part (212) and the foot preform part (213) comprise one or more unties extending around the central untie of the foot preform part (213).

11. Blade according to any one of claims 7 to 10, wherein at least a portion of the warp threads of the stilt preform portion (212) is oriented in at least one determined direction different from the direction of the warp threads (101) present in the foot preform portion (213) and the airfoil preform portion (211).

12. Blade according to any one of claims 7 to 11, wherein the foot (13) of the blade (10) further comprises a metal shell.

13. Aeronautical engine comprising a plurality of blades according to any one of claims 7 to 12.

14. Aircraft comprising at least one engine according to claim 13.

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