Composite material blade with reinforced stilt

Abstract

Composite material blade with reinforced stilt A blade (10) made of composite material comprises a fiber reinforcement densified by a matrix, the blade comprising, in a span direction, a root (13), a stilt (12) and an aerodynamic profile (11), the fiber reinforcement comprising a fiber preform having a three-dimensional weave between a plurality of warp threads and a plurality of weft threads. The stilt preform portion of the fiber preform has a weft structure lower than the weft structure of the root preform portion and the aerodynamic profile preform portion of said fiber blank. Figure for abstract: Fig. 15.

Description

Title of the invention: Composite material blade with reinforced stilt Technical field

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

[0002] Turboprop blades are generally made of metallic material. While blades made of metallic material have good mechanical strength, they do have the disadvantage of being relatively heavy.

[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] Document US 2013 / 0017093 describes the production of a propeller blade from a fiber structure with an aerodynamic profile inside which a part of a spar is introduced, 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 unducted engines (known as "open fan" or "open rotor" in English) requires more compact blade roots. This need arises from the necessity of being able to pivot the blade around its vertical axis in order to adapt its incidence to the flight regime (variable pitch blade or blade). This need, combined with the fact that the blade must be integrated as low as possible on the disk, requires a significant reduction in the size of the root.

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

[0007] On a ducted engine, the retention casing has the function of containing the blade(s) in the event of a blade loss incident following an impact with an object, such as in the case of bird ingestion. On the other hand, on an unducted engine, it is necessary to ensure a virtually unlimited blade life. Cyclic fatigue loading in bending has a significant impact on the life of blades made of new-generation composite material (axisymmetric or substantially axisymmetric shape and reduced dimensions of the blade root). Indeed, the bending loading caused by impacts with objects induces in particular tensile forces at the Péchasse leave of the dawn. In addition, the roots of the new generation blades can be integrated into the rotor disc using metal shells, which results in additional mechanical loading in circumferential compression.

[0008] If the 3D woven fiber reinforcement gives the aerodynamic profile part of the blade (vein zone) very high resistance to impacts, however it has a lower resistance to mechanical loading in traction and compression at the level of Péchasse of the dawn. Statement of the invention

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

[0010] To this end, the present invention proposes a method of manufacturing a blade made of composite material, the method comprising: - weaving a single-piece fiber blank comprising a root portion, an aerodynamic profile portion and a stilt portion connecting the root portion to the aerodynamic profile portion, the root portion of the fiber blank comprising a central uncoupling delimiting an internal root housing opening at a free end of said root portion, the aerodynamic profile portion and the root portion being woven in a three-dimensional weave between a plurality of warp threads extending in a longitudinal direction corresponding to the span direction of the blade to be manufactured and a plurality of weft threads extending in a transverse direction corresponding to the chord direction of the blade to be manufactured, - shaping the fiber blank to obtain a one-piece fiber preform with an aerofoil preform portion, a foot preform portion and a stilt preform portion, the shaping comprising positioning an insertion element in the internal foot housing so as to form the foot preform portion, - densification of the fiber preform by a matrix to obtain a blade made of composite material having a fiber reinforcement constituted by the fiber 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 portion of the fiber blank has a weft structure lower than the weft structure of the foot portion and the aerodynamic profile portion of said fiber blank.

[0011] The method of the invention thus makes it possible to produce a blade with a composite root which is both compact and perfectly adapted to withstand the various mechanical loads described above. Indeed, the reduction of the texture The weft in the stilt part makes it possible to approach the behavior of a unidirectional fiber reinforcement and to locally give the fiber reinforcement of the final blade mechanical properties similar to those of a unidirectional fiber reinforcement or ply. This increases the resistance at the Péchasse level of the final blade with respect to mechanical loading in tension and compression at the Péchasse level of the blade, which makes it possible to significantly increase the life of the blade, particularly with respect to loading cycles in bending fatigue.

[0012] Furthermore, by maintaining a three-dimensional weave in the root portion of the fiber blank, it is possible to maintain drapability for the stilt portion even when the latter is devoid of weft threads. This also makes it possible to maintain mechanical strength in the weft direction in useful compression, particularly in the reach of the root of the blade.

[0013] According to one embodiment of the method of the invention, the stilt portion of the fiber blank is devoid of weft threads so as to comprise only unidirectional plies of warp threads. In this case, the portion of the fiber reinforcement of the blade present at the Péchasse level has a behavior identical to that of a unidirectional reinforcement.

[0014] According to another embodiment of the method of the invention, an external portion of the stilt part of the fiber blank is devoid of weft threads so as to comprise only unidirectional folds of warp threads in said external portion while an internal portion of the stilt part comprises weft threads woven with warp threads. This makes it possible to limit the reduction in section at the level of the stilt part of the fiber blank while maintaining a gain in mechanical strength at the level of the stilt by the presence of unidirectional folds in an external portion of the stilt part of the fiber blank.Furthermore, the retention of weft threads on a certain proportion of the stilt part of the fiber blank makes it possible to have a preform with better hold which is easier to handle without risk of damage, including for the portion of the fiber blank which only comprises unidirectional folds, i.e. without weft thread.

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

[0016] According to a particular characteristic of the method of the invention, during the shaping of the fiber blank, at least a portion of the warp threads of the stilt portion of the fiber blank is oriented in at least one determined direction different from the direction of the warp threads present in the foot preform portion. and in the profile preform part. This makes it possible to further strengthen the mechanical strength at the level of the blade stilt because the warp threads can be oriented in one or more directions corresponding to the direction(s) of application of the mechanical forces.

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

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

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

[0020] According to one embodiment of the blade of the invention, the stilt preform portion is devoid of weft threads so as to comprise only unidirectional plies of warp threads. In this case, the portion of the fiber reinforcement of the blade present at the Péchasse level has a behavior identical to that of a unidirectional reinforcement.

[0021] According to another embodiment of the blade of the invention, an outer portion of the stilt preform part is devoid of weft yarns so as to comprise only unidirectional plies of warp yarns in said outer portion while an inner 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 stilt and the foot preform portion comprise one or more debonds extending around the central debond of the foot preform portion. This makes it possible in particular to form several independent portions in the fiber reinforcement, each having its own mechanical characteristics.

[0023] According to a particular characteristic of the blade of the invention, at least a portion of the warp threads of the stilt preform portion is oriented in at least one determined direction different from the direction of the warp threads present in the root preform portion and the aerodynamic profile preform portion. This makes it possible to further reinforce the mechanical strength at the stilt of the blade because the warp threads can be oriented in one or more directions corresponding to the direction(s) of application of the mechanical forces.

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

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

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

[0027] [Fig.2] [Fig.2] is an enlarged scale cross-sectional view in the weft direction of a set of layers of yarns showing the formation of two unlinkages in the foot part of the blank of [Fig.l] according to a section plane II-II,

[0028] [Fig.3] [Fig.3] is an enlarged scale cross-sectional view in the weft direction of a set of layers of yarns showing the formation of two unlinkages in the foot part of the blank of [Fig.l] according to a section plane III-III,

[0029] [Fig.4] [Fig.4] is a schematic perspective view showing the shaping of a foot preform portion in the fiber blank of [Fig.l],

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

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

[0032] [Fig.7] [Fig.7] is a partial schematic view of a fiber blade preform without twisting of the stilt preform portion,

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

[0034] [Fig.9] [Fig.9] is a schematic sectional view of a portion of the fiber blank of [Fig.l] showing a stilt portion according to another embodiment,

[0035] [Fig. 10] [Fig. 10] is a schematic sectional view of a portion of the fiber blank of [Fig.l] showing a stilt portion according to another embodiment,

[0036] [Fig. 11] [Fig. 11] is a schematic sectional view of a portion of the fiber blank of [Fig.l] showing a stilt portion according to another embodiment,

[0037] [Fig. 12] [Fig. 12] is a schematic sectional view of a portion of the fiber blank of [Fig.l] showing a stilt portion according to another embodiment,

[0038] [Fig. 13] [Fig. 13] is an exploded perspective schematic view showing an injection tool and the placement of the fiber preform therein in accordance with one embodiment of the invention,

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

[0040] [Fig. 15] [Fig. 15] is a schematic perspective view of a composite material blade obtained in accordance with one embodiment of the invention. Description of the embodiments

[0041] The invention applies generally to different types of propeller blades or vanes used in aircraft engines. The invention finds an advantageous but not exclusive application in large propeller blades or vanes which are intended to be integrated into pivoting or variable pitch systems. Such propeller blades or vanes are generally provided with a root having both a small footprint (compact shape) and good resistance to tensile, bending and circumferential compression forces. The vane according to the invention may in particular constitute a vane for shrouded moving wheels such as fan blades or a vane for unshrouded moving wheels as in so-called "open rotor" aeronautical engines.

[0042] In the remainder of the description, the exemplary embodiments are described in relation to turboprop blades. However, the exemplary embodiments also apply to propeller blades for aircraft.

[0043] [Fig.l] shows very schematically a fiber blank 100 intended to form the fiber preform of a blade to be produced.

[0044] The fibrous blank 100 is obtained, as schematically illustrated in [Fig.l], by three-dimensional (3D) weaving carried out in a known manner using a jacquard-type loom on which a bundle of warp threads 101 or strands has been arranged in a plurality of layers of several hundred threads each, the warp threads being linked by weft threads 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 threads 101 extend, between a lower part 100c and an upper part 100d and in a transverse direction Dt, corresponding to the chord direction of the blade to be manufactured and the direction in which the weft threads extend, between a front edge 100a and a rear edge 100b. The fiber blank 100 comprises an aerodynamic profile part 111 defining two faces 11e and 11If intended to form respectively the extrados and intrados faces of the blade, a root part 113 intended to subsequently form a blade root and a stilt part 112 present between the root part 113 and the aerodynamic profile part 111, the stilt part 112 connecting the root part 113 to the aerodynamic profile part 111.

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

[0046] In the example illustrated, the 3D weave is an "interlock" weave. By "interlock" we mean here a weave weave in which each layer of weft threads binds several layers of warp threads with all the threads of 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 document WO 2006 / 136755. This document describes in particular the production by weaving in a single piece of fiber 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 fiber blank according to the invention can be woven in particular from carbon fiber or ceramic fiber threads such as silicon carbide.

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

[0050] During weaving, a central uncoupling 106 is produced inside the foot portion 113 of the fiber blank 100 between two successive layers of warp threads. The central uncoupling 106 extends along a plane parallel to the surface of the fiber blank and over a uncoupling zone delimited by a contour 106a locally separating the foot portion 113 into two woven portions 114 and 115. Furthermore, the uncoupling 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 uncoupling 106 does not open onto the lateral edges 1120 and 1121) so as to maintain connecting portions 105 and 107 adjacent to the first and second lateral edges 1120 and 1121 respectively. The central unconnection 106 also opens onto the free lower end 1122 of the foot portion 113. The unconnection 106 thus forms an internal housing 140 in the foot portion 113 which is accessible via the free lower end 1122. The internal housing 140 is intended to receive an insertion element during the shaping of the fiber blank as explained below.

[0051] A 3D interlock weaving mode of the blank 100 is shown schematically in [Fig. 2]. [Fig. 2] is an enlarged partial view of a warp sectional plane 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 root 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 threads 101 linked together by four weft threads Ti to T4 while the woven portion 114 comprises the four layers of warp threads forming the set of layers of threads 109 are linked by four weft threads T5 to T8.

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

[0053] In the weaving example presented in [Fig. 2], the weft threads Ti to T4, on the one hand, and the weft threads T5 to T8, on the other hand, are respectively arranged on each side of the unlinking 106, the weft threads Ti to T4 binding the first four layers of warp threads forming the woven portion 115 and the weft threads T5 to T8 binding the last four layers of warp threads 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 yarns of the layers of weft yarns crosses a second portion of yarns of the layers of weft yarns in a zone of the fiber blank 100 located in the vicinity of the unlinking 106 in the transverse direction DT, the yarns of the first portion of weft yarns 102 extending on one side of the unlinking 106 in the transverse direction DT while the yarns of the second portion of yarns of the plurality of layers of weft yarns 102 extend on the other side of the unlinking 106 in the transverse direction DT. More precisely, one or more weft yarns 102 binding layers of warp yarns forming a set of layers of yarns 108 in the binding zone 105 are used to bind layers of warp yarns 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 start or upstream of unbonding 106 in 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 start or upstream of unbonding 106 in the transverse direction DT to bond layers of warp yarns 101 of the set of yarn layers 108.After the unlinking 106, the weft yarns T3 and T4 are again deflected at the end or downstream of the unlinking 106 in the transverse direction DT, i.e. at 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 unlinking 106 in the transverse direction DT, i.e. at 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 unlinking 106 in the transverse direction DT makes it possible to improve the strength of the fiber blank in the binding zone. unlinking. According to an alternative embodiment, some of the weft threads can cross only upstream or downstream of the unlinking 106 in the transverse direction DT.

[0055] Once the weaving is finished, the non-woven threads 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 lower than the weft structure of the foot portion 113 and the aerodynamic profile portion 111 of the fiber blank 100. The weft structure corresponds to the spacing between two columns of weft threads. In other words, the stilt portion 112 comprises a number of weft threads per unit length in the longitudinal direction DL lower than the number of weft threads present in the foot portion 113 and in the aerodynamic profile portion 111 for the same unit length. The number of weft threads present in the stilt portion may be zero or almost zero. In this case, the stilt portion comprises only warp threads which are not woven with weft threads thus forming unidirectional plies of warp threads as described below in detail.When the stilt portion of the fiber blank comprises 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 comprises weft threads, these can be made of yarns with a lower count and / or grammage than the other weft yarns used in the rest of the fiber blank. The weft yarns present in the stilt part can be, for example, polyester yarns.

[0058] The reduction of the weft texture in the stilt part makes it possible to approach the behavior of a unidirectional fiber reinforcement and to locally confer on the fiber reinforcement of the final blade mechanical properties similar to those of a unidirectional fiber reinforcement or ply. This increases the resistance at the Péchasse level of the final blade with respect to mechanical loadings in tension and compression at the Péchasse level of the blade, which makes it possible to significantly increase the service life of the blade, in particular with respect to loading cycles in bending fatigue.

[0059] Furthermore, by maintaining a three-dimensional weave in the root portion of the fiber blank, it is possible to maintain drapability for the stilt portion even when the latter is devoid of weft threads. This also makes it possible to maintain mechanical strength in the weft direction in useful compression, particularly in the reach of the root of the blade.

[0060] [Fig. 6] illustrates very schematically a portion of the fiber blank 100 showing a stilt portion 112 according to one embodiment. [Fig. 6] corresponds to a half-section at the level of the root portion 113, of Péchasse 112 and of a lower part of the aerodynamic profile portion 111 of the fiber blank 100 according to the reference VLVI in [Fig. 4]. In this embodiment, the stilt portion of the fiber blank is devoid of weft threads 102 and only comprises non-woven warp threads 101 forming unidirectional folds of warp threads. In this embodiment, the part of the fiber reinforcement of the blade present at the Péchasse level has a behavior identical to that of a unidirectional reinforcement.

[0061] [Fig. 9] illustrates very schematically a portion of the fiber blank 100 showing a stilt portion 112 according to another embodiment. [Fig. 9] corresponds to a half-section at the level of the foot portion 113, of the stilt portion 112 and of a lower part of the aerodynamic profile portion 111 of the fiber blank 100 along the reference IX-IX in [Fig. 4]. In this embodiment, the stilt portion of the fiber blank has a lower weft construction than the weft construction in the foot portion 113 and in the airfoil portion 111. Although the stilt portion 112 here has a 3D weave, the spacing between the weft columns is much greater than in the other 3D woven portions of the blank, which allows for 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 part is preferably 90 / 10. The presence of weft threads 102 even very spaced from each other makes it possible to have a . more regular spacing between warp threads 101.

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

[0063] According to another particular characteristic of the invention, one or more disconnections may be formed in the stilt portion 112 and in the foot portion 113.

[0064] As a non-limiting example, [Fig. 11] very schematically illustrates a portion of the fiber blank 100 showing a stilt portion 112 according to another embodiment. [Fig. 11] corresponds to a half-section at the level of the root portion 113, of Péchasse 112 and of a lower part of the aerodynamic profile portion 111 of the fiber blank 100 according to the reference XLXI in [Fig. 4]. In this embodiment, the stilt portion of the fiber blank is devoid of weft threads 102 and only comprises non-woven warp threads 101 forming unidirectional folds of warp threads. In this case, the part of the fiber reinforcement of the blade present at the Péchasse level has a behavior identical to that of a unidirectional reinforcement.Furthermore, in this embodiment, the stilt portion 112 and the foot portion 113 of the fiber blank comprise a gap 122 which extends around the central gap 106 of the foot portion 113 of the fiber blank and which separates the stilt portion 112 and the foot portion 113 into two independent portions 120 and 121.

[0065] As a non-limiting example, [Fig. 12] very schematically illustrates a portion of the fiber blank 100 showing a stilt portion 112 according to another embodiment. [Fig. 12] corresponds to a half-section at the level of the foot portion 113, of the stilt portion 112 and of a lower part of the aerodynamic profile portion 111 of the fiber blank 100 according to the reference XILXII in [Fig. 4]. In this embodiment, the stilt portion 112 and the foot portion 113 of the fiber blank comprise two uncouplings 153 and 154 which extend around the central uncoupling 106 of the foot portion 113 of the fiber blank and which separate the part of stilt 112 and the foot portion 113 into three independent portions 150, 151 and 152. In the portions 150 and 151 at the stilt portion 112, the warp threads 101 are woven with weft threads 102 but with a weft count lower than the weft count in the foot portion 113 and in the airfoil portion 111 while the portion 153 at the stilt portion 112 is devoid of weft threads 102 and comprises only non-woven warp threads 101 forming unidirectional plies of warp threads.

[0066] Each independent portion formed in the stilt portion by a delinking may be devoid of weft yarns or be woven with weft yarns but with a lower thread count than the weft thread count of the foot portion and the aerodynamic profile portion of the fiber blank.

[0067] The manufacture of the blade continues by shaping the fiber blank 100. In the example described here, the shaping of the root part 112 is carried out by separating the woven portions 114 and 115 and by introducing an insertion element 130 into the internal housing 140 formed by the decoupling 106 as illustrated in [Fig. 4]. The insertion element may in particular be made of metallic material or resin by additive manufacturing for example.

[0068] A fiber preform 200 is thus obtained comprising, in the longitudinal direction D1, a root preform portion 213 comprising the insertion element 130, a stilt preform portion 212 and an aerodynamic profile preform portion 211 as shown in [Fig. 5]. The aerodynamic profile preform portion 211 extends in the transverse direction DT between a leading edge preform portion 211a and a trailing edge preform portion 211b.

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

[0070] According to a particular characteristic, 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 may be oriented in at least one determined direction different from the direction of the warp threads present in the root preform portion 213 and in the aerodynamic profile preform portion 211 by applying a twist at the portion of the stilt preform portion. This makes it possible to orient the warp threads in the stilt preform portion in a direction of force stress and to further reinforce the mechanical strength of the final blade at the level of Péchasse as a function of particular forces.

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

[0072] The warp threads of the stilt preform portion may also be oriented in 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. For this purpose, the stilt portion of the fiber blank comprises one or more unlinkings making it possible to form independent portions such as the portions 120, 121, 150, 151 and 152 illustrated respectively in FIGS. 11 and 12. Each independent portion may be subjected to a twist in a determined direction in order to orient the warp threads of one portion in a direction different from that of the warp threads of another portion.For example, the warp yarns of a first portion may form an angle of +45° with the warp yarns present in the root preform portion and in the airfoil preform portion while the warp yarns of a second portion may form an angle of -45° with the warp yarns present in the root preform portion and in the airfoil preform portion.

[0073] The fibrous preform is then densified. The densification of the fibrous preform intended to form the fibrous reinforcement of the part to be manufactured consists of filling the porosity of the preform, in 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 process (LC). The liquid 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 closed tightly with a housing having the shape of the final molded blade.Then, the mold is closed and the liquid matrix precursor (for example a resin) is injected into the entire housing 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 elimination of any solvent and crosslinking of the polymer, the preform being always maintained 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 carbon or ceramic matrix depending on the precursor used and the pyrolysis conditions. For example, liquid ceramic precursors, particularly SiC, can be polycarbosilane (PCS) or polytitanocarbosilane (PTCS) or polysilazane (PSZ) resins, while liquid carbon precursors can be resins with a relatively high coke content, such as phenolic resins. Several consecutive cycles, from impregnation to heat treatment, can be carried out to achieve the desired degree of densification.

[0076] According to one aspect of the invention, in the case in particular of the formation of an organic matrix, the densification of the fibrous preform can be carried out by the well-known transfer molding process known as RTM ("Resin Transfer Molding"). In accordance with 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 which includes the fibrous preform. A pressure gradient is generally established in this internal space between the place where the resin is injected and the orifices for discharging the latter 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 as well as its transformation into a matrix are here carried out in an injection tool 300 which comprises a first shell 310 comprising in its center a first imprint 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 imprint 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 impressions 311 and 321 respectively of the first and second shells 310 and 320 together define an internal volume 301 having the shape of the blade to be produced and in which the fiber preform 200 is placed. A compaction of the fiber preform 200 can be carried out with the closing of the tool 300 in order to obtain a determined fiber rate in the preform. In this case, a compaction pressure is applied to the shells 310 and 320 for example by means of a press. The compaction of the fiber preform can also be carried out in a separate tool before the introduction of the preform into the injection tool.

[0079] The tooling 300 further comprises means for carrying out the injection of a liquid matrix precursor and the transformation of this precursor into a matrix. More specifically, in the example described here, the first shell 310 of the tooling 300 comprises an injection port 313 intended to allow the injection of a liquid matrix precursor composition into the fiber preform while the second shell comprises an evacuation port 323 intended to cooperate with a system of pumping for vacuuming the tooling and drawing air during injection. The injection tooling 300 also comprises a lower part 340 and an upper part 350 between which the first and second shells 310 and 320 are placed, the lower part 340 and the upper part 350 being equipped with heating means (not shown in [Fig. 14]).

[0080] Once the tool 300 is closed, the blade is molded by impregnating the preform 200 with a thermosetting resin that is polymerized by heat treatment. For this purpose, the well-known injection or transfer molding process known as RTM ("Resin Transfer Molding") is used. 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 discharge conduit maintained under pressure (not shown in [Fig. 14]). This configuration allows the establishment of 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 substantially at the level of the lower part of the preform will gradually impregnate the entire preform by circulating in it up to the evacuation port 323 through which the surplus is evacuated. Of course, the first and second shells 310 and 320 of the tooling 300 may respectively comprise several injection ports and several evacuation ports.

[0081] The resin used may be, for example, an epoxy resin with a temperature class of 180°C (maximum temperature supported without loss of characteristics). Resins suitable for RTM processes are well known. They preferably have a low viscosity to facilitate their injection into the fibers. The choice of temperature class and / or the chemical nature of the resin is determined according to the thermomechanical stresses to which the part must be subjected. Once the resin has been injected throughout the reinforcement, it is polymerized by heat treatment in accordance with the RTM process.

[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 fiber preform of the invention, mainly propeller blades or vanes made of organic matrix composite material (OMC), carbon matrix composite material (C / C) and ceramic matrix composite material (CMC).

[0084] As illustrated in [Fig.15], a blade 10 is obtained formed from a fibrous reinforcement densified by a matrix which comprises a root 13 formed by the root preform part 213 of the fibrous preform 200, a stilt 12 formed by the preform part of stilt 212 and a blade 11 formed by the blade preform portion 211 of the fiber preform 200. The blade 10 comprises a leading edge 11a and a trailing edge 11b corresponding respectively to the leading edge 211a and trailing edge 211b portions of the fiber preform 200 as well as an extrados face 11e and a intrados face 11f. The root 13 comprises a cavity 14 formed by the internal housing 240 of the fiber preform 200, the insertion element 130 being glued inside said cavity 14. The blade 10 thus comprises a root 13 which has a compact axisymmetrical shape suitable for integration into a propeller rotation or pitch change system and which has at its stilt 12 an increased mechanical resistance with respect to mechanical loading in tension and compression.

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

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

Claims

Claims

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

2. The method of 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. The method of claim 1, wherein an outer portion (1121) of the stilt portion (112) of the fiber blank (100) is devoid of weft threads (102) so as to comprise only unidirectional plies of warp threads (101) in said outer portion while an inner portion (1122) of the stilt part comprises weft threads (102) woven with warp threads (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 debonds (114) extending around the central debond (106) of the foot portion (113) of the fibrous blank.

5. Method according to any one of claims 1 to 4, wherein, when shaping the fibrous blank (100), at least a portion of the warp threads (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 threads 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 outer shell (15) around the root preform portion (213) or the root (13) of the blade (10).

7. Blade (10) made of composite material comprising a fibrous reinforcement densified by a matrix, the blade comprising, in a span direction, a root (13), a stilt (12) and an aerodynamic profile (11), the fibrous reinforcement comprising a fibrous preform (200) having a three-dimensional weave between a plurality of warp threads (101) extending in the span direction and a plurality of weft threads (102) extending in a chord direction of the blade, the fibrous preform (200) comprising a root preform portion (213) present in the root (13), a stilt preform portion (212) present in the stilt (12) and an aerodynamic profile preform portion (211) present in the aerodynamic profile (11), the root preform portion (213) of the fibrous preform (200) comprising a central debonding (106) defining 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 fiber preform has a weft structure lower than the weft structure of the foot preform portion (213) and the aerodynamic profile preform portion (211) of said fiber blank.,

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

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

10. A blade according to any one of claims 7 to 9, wherein the stilt preform portion (212) and the root preform portion (213) comprise one or more uncouplings extending around the central uncoupling of the root preform portion (213).

11. A 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 root preform portion (213) and the aerodynamic profile preform portion (211).

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

13. An 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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