Fibrous preform of a turbomachine blade

Abstract

Fibrous Preform of a Turbomachine Blade The present invention relates to a fibrous preform (10) of a blade woven in a single piece of three-dimensional fabric, comprising: - a first part (12) defining a profile and having a radial unbundle (DR), and - a second part formed by portions (14) originating from the first part and unbundled from the radial unbundle, each portion being folded over a respective side of the first part, each unbundled portion comprising a first textile element (15) defining a platform reinforcement, and a second textile element (16) comprising (i) at least one zone woven (161) with the first element, and (ii) two textile units (163) cut from the second element and extending from said at least one woven zone, said units being unbundled from the first element and deployed transversely to the latter to define a swashplate reinforcement. Fig. 2.

Description

Title of the invention: Fibrous preform of a turbomachine blade technical field

[0001] The present disclosure relates to the design of turbomachine blades made of ceramic matrix composite (CMC) material, in particular turbine blades. Prior art

[0002] Ceramic matrix composite materials (CMCs) withstand temperatures ranging from 600°C to 1400°C. Due to their superior high-temperature resistance, CMCs require less cooling. Since this cooling is traditionally obtained from the compressor, which impacts the turbomachine's efficiency, CMCs improve engine efficiency, thereby reducing fuel consumption. Furthermore, their use helps optimize turbomachine performance, notably by reducing the overall mass of the turbomachine, which further contributes to lower fuel consumption and thus a significant reduction in pollutant emissions.

[0003] Turbine blades made of CMC material can be produced from a fibrous blank obtained by three-dimensional weaving, which is then shaped and densified by the ceramic matrix. US2017 / 198591, in particular, discloses the production of continuous tangential blade edges from a woven blank. This solution gives satisfactory results but leads to an imbalance in thickness between the lower and upper surfaces, and requires removing a significant volume of material from the thicker area of ​​the blade root, while machining the composite is generally lengthy and expensive. This material removal in the thicker part also requires precautions with regard to the textile pattern to ensure a minimum of textile continuity. Furthermore, this solution makes it difficult to control the radius dimensions at the unbalanced lower / upper surface transition. The invention aims to overcome all or part of these drawbacks. Description of the invention

[0004] The present description relates to a fibrous preform of a turbomachine blade woven in a single piece of three-dimensional fabric, comprising: - a first part defining a reinforcement of an aerodynamic profile having, at one apex, a radial decoupling, and - a second part which is formed by fibrous portions each originating from the first part and detached from the radial detachment, each fibrous portion being folded back on a respective side of the first part and transversely to the latter, each unbound portion comprising a first textile element defining a platform reinforcement, and a second textile element comprising (i) at least one area woven with the first element and offset along a radial direction relative to the latter, and (ii) two textile units cut from the second element and extending from said at least one woven area, said units being unbound from the first element and deployed transversely to the latter to define a slat reinforcement.

[0005] The invention advantageously avoids the use of the unbalanced unlinking of the prior art mentioned above, and provides high mechanical strength in the platform area due to the use of a single piece of fabric guaranteeing textile continuity.

[0006] The invention is expressed in different embodiments which are detailed below.

[0007] In one embodiment, the second textile element of each unbound portion comprises (i) a zone woven with the first element and located radially outside with respect to the first element, and (ii) two textile units unbound from the first element and each extending from a distinct axial edge of the woven zone, each textile unit being obtained by cutting from the side of the radial unbinding and being deployed transversely to the corresponding axial edge.

[0008] In one embodiment, the second textile element of each unbound portion comprises (i) two areas woven with the first element, each having a first axial edge on a distinct axial end of the preform and located radially outside with respect to the first element, and (ii) two textile units, separated from each other by cutting, each extending from a second axial edge, opposite the first axial edge, of a distinct woven area, the textile units being unbound from the first element and each textile unit being obtained by cutting on the side of the radial unbinding and deployed transversely to the corresponding second axial edge.

[0009] In one embodiment, the second textile element of each unbound portion comprises, on the side of each axial end of the preform, (i) a zone woven with the first element and located radially outside with respect to the first element, the woven zone having a first axial edge on an axial end of the preform, a second axial edge, opposite the first axial edge, not perpendicular to an axial direction, and a tangential edge connecting the first axial edge to the second axial edge, and (ii) a textile unit extending from the second axial edge and separated by cutting from a unbound zone of the second element extending from the tangential edge, the textile unit being unbound from the first element and comprising a first section extending from the second axial edge and folded over the woven zone so as to partially cover it up to a deployment fold and a second section extending from this fold. deployment and deployed transversely to the first section to define the reinforcement of the lick, the units being separated from each other by cutting.

[0010] In one embodiment, the second textile element of each unbound portion comprises (i) two woven areas with the first element, each having a first axial edge on a distinct axial end of the preform and located radially inward with respect to the first element, and (ii) two textile units, separated from each other by cutting, each extending from a second axial edge, opposite the first axial edge, of a distinct woven area, the textile units being unbound from the first element and each textile unit being obtained by cutting on the side of the radial unbinding and comprising (a) a first section extending from the corresponding second axial edge and forming a first fold around the first axial edge of the corresponding woven area so as to be positioned radially outward with respect to the first element, the first section extending to a second fold,and (b) a second section extending from this second fold and deployed transversely to the first section to define the slit reinforcement.

[0011] The present disclosure also relates to a turbomachine blade made of ceramic matrix composite material, comprising a fibrous reinforcement formed by a preform as described above, and a ceramic matrix densifying said reinforcement.

[0012] In one embodiment, the blade is a turbine blade.

[0013] The aforementioned features and advantages, as well as others, will become apparent from the following detailed description which refers to the attached drawings. Brief description of the drawings

[0014] The attached drawings are schematic and are intended primarily to illustrate the principles of the exposition.

[0015] [Fig-1] Fig. 1 is a schematic cross-sectional view of a twin-turbine engine flow.

[0016] [Fig.2] Fig.2 represents, schematically, a first example of a fibrous preform according to the invention.

[0017] [Fig.3] Fig.3 represents schematically the texture, intended to form the fibrous preform of Fig.2, before cutting and deployment of the reinforcement of the slats.

[0018] [Fig.4] Fig.4 schematically represents the deployment of the reinforcement of the slats to obtain the fibrous preform of Fig.2.

[0019] [Fig.5] Fig.5 represents, schematically, a second example of a fibrous preform according to the invention.

[0020] [Fig.6] Fig.6 represents schematically the texture, intended to form the fibrous preform of Fig.5, before cutting and deployment of the reinforcement of the slats.

[0021] [Fig.7] Fig.7 schematically represents the deployment of the reinforcement of the slats to obtain the fibrous preform of Fig.5.

[0022] [Fig.8] Fig.8 represents, schematically, a third example of a fibrous preform according to the invention.

[0023] [Fig.9] Fig.9 schematically represents a view along the axial direction of the preform of Fig.8.

[0024] [Fig. 10] The [Fig. 10] schematically represents the texture, intended to form the fibrous preform of figures 8 and 9, before cutting and deployment of the reinforcement of the strips.

[0025] [Fig. 11] Fig. 11 schematically represents the deployment of the reinforcement of the slats to obtain the fibrous preform of figures 8 and 9.

[0026] [Fig. 12] The [Fig. 12] represents, schematically, a fourth example of a fibrous preform according to the invention.

[0027] [Fig. 13] The [Fig. 13] schematically represents the texture, intended to form the fibrous preform of the [Fig. 12], before cutting and deployment of the reinforcement of the slats.

[0028] [Fig. 14] The [Fig. 14] schematically represents the deployment of the reinforcement of the slats to obtain the fibrous preform of the [Fig. 12].

[0029] [Fig. 15] The [Fig. 15] schematically represents an example of a turbine blade according to the invention. Description of the implementation methods

[0030] Fig. 1 represents, in section along a vertical plane passing through its main axis A, a turbofan engine 1. It comprises, from upstream to downstream along the airflow circulation, a fan 2, a low-pressure compressor 3, a high-pressure compressor 4, a combustion chamber 5, a high-pressure turbine 6, and a low-pressure turbine 7.

[0031] The blower 2 allows the aspiration of an airflow to which two independent circulations are imposed, to form a primary airflow (hot flow) and a secondary airflow (cold flow).

[0032] The primary stream air can for example be compressed within the low pressure compressor 3 and then the high pressure compressor 4, and then mixed with a fuel and burned within a combustion chamber 5. The gases expelled from the combustion chamber can pass through a high pressure turbine 6 and then a low pressure turbine 7 before undergoing acceleration through a nozzle.

[0033] The secondary flow, on the other hand, bypasses the hot part of the reactor.

[0034] The compressors 3, 4 and the turbines 5, 6 comprise several stages of fixed blades (called "stators") and moving blades (called "rotors").

[0035] The movable blades comprise a ring of blades mounted radially on a disk, which drives a rotating shaft under the effect of a passing air or gas flow. Each blade comprises a blade connected to a foot that is fitted into a groove in the disk in order to hold the blade in place during the operation of the turbomachine.

[0036] The fixed blades, generally arranged between each stage of moving blades, allow the airflow to be straightened before the flow enters the next stage of moving blades.

[0037] The hot sections of the turbojet engine, located downstream of chamber 5, can incorporate CMC components such as CMC turbine blades. The following section describes various examples of CMC blade architectures according to the invention.

[0038] In the present exposition, the terms "axial", "radial", "tangential", "internal", "external" and their derivatives are defined with respect to the main axis of the turbomachine; the terms "upstream" and "downstream" are defined with respect to the flow of gas in the turbomachine.

[0039] We will now describe different examples of fibrous preforms of turbomachine blades according to the invention.

[0040] Generally, the preform according to the invention was obtained by weaving a three-dimensional fabric in a single piece. The term "three-dimensional fabric" or "3D fabric" refers to a weaving method in which at least some of the weft yarns bind warp yarns across several warp layers. It should be noted that a reversal of the roles between warp and weft is possible and should be considered as also covered by the claims. The production of the fibrous preform by 3D weaving makes it possible to obtain a bond between the layers, thus ensuring good mechanical strength of both the fibrous preform and the resulting composite material part, all in a single textile operation. The fibrous preform may, for example, have an interlock weave.The term "interlock weave or fabric" refers to a three-dimensional weave in which each layer of weft yarns interlocks several layers of warp yarns, with all yarns in the same weft column having the same movement within the plane of the weave. The use of other types of 3D weaves is, of course, not outside the scope of the invention. Various suitable weaving techniques are described in document WO 2006 / 136755.

[0041] The 3D weaving technique is a known technique per se, as is the formation of unlinks which is exploited within the scope of the present invention. In a manner known per se, an unlink is created between two layers of warp yarns by not passing weft yarns through the unlinking zone so as not to bind yarns from warp layers located on either side of the unlink. As will be detailed Further down, the invention also proposes to make local cuts which are implemented using techniques known per se.

[0042] Generally, the fibrous preform can be made of ceramic wires, for example, silicon carbide wires. The fibrous preform can constitute the fibrous reinforcement of the composite part to be obtained. Examples of usable silicon carbide wires include "Nicalon," "Hi-Nicalon," "Hi-Nicalon-S," or Tyranno SA3 wires from UBE Industries. The ceramic wires of the fibrous preform can have an oxygen content of 1% or less. "Hi-Nicalon-S" wires, for example, have this characteristic.

[0043] Each example of a preform 10, 20, 30, and 40, which will be described hereafter, comprises a first portion 12, 22, 32, and 42 that defines an aerodynamic profile reinforcement and has, at one vertex, a radial joint denoted DR. The first portion 12-42 is obtained by three-dimensional weaving. The joint DR defines two sections 14, 24, 34, and 44 that can be separated from each other and deployed transversely with respect to the first portion 12-42. Each section 14-44 is obtained by three-dimensional weaving. Each section 14-44 is folded over on one respective side (intrados or extrados) of the first portion 12-42 and transversely to the latter. Each section 14-44 extends either on the intrados side or the extrados side. Portions 14-44 can have essentially the same thickness, for example within 10%.Each portion 14-44 originates from the first portion 12-42; that is, the first portion 12-42 extends beyond the DR unbinding to form the two unbound fibrous portions 14-44. Thus, all the warp fiber layers of the portions 14-44 (taken here as the fibers extending along the R direction before the folding of the portions 14-44) are found in the first portion 12-42. If we denote N, NI, and N2 respectively the number of warp fiber layers in the first portion 12-42, the number of warp fiber layers in the intrados portion 14-44, and the number of warp fiber layers in the extrados portion 14-44, we can thus have the following relationship: N = NI + N2.

[0044] Portions 14-44 define the blade platform reinforcement as well as the flap reinforcement, but they exhibit distinct structures depending on the preform 10-40 considered, which are associated with specific deployment strategies for forming the flap reinforcement, as will now be described. Generally speaking, it should be noted that, for each preform 10-40, the lower surface portion can usually be symmetrical to the upper surface portion with respect to a first plane containing the radial direction R and the decoupling DR. Furthermore, the upstream and downstream parts of each portion 14-44 can generally correspond symmetrically with respect to a second plane transverse, or even perpendicular, to the first plane.

[0045] Figures 2 to 4 relate to a first example of preform 10 according to the invention.

[0046] According to this example, each portion 14 comprises a first textile element 15 which defines a platform reinforcement, and a second textile element 16 which comprises (i) a woven area 161 with the first element 15 and located radially outside with respect to the latter, and (ii) two textile units 163 unbound from the first element 15, separated from the latter, and each extending from an axial edge BA161 distinct from the area 161. Thus a first unit 163 extends from a first upstream edge BA161, and a second unit 163, distinct from the first unit 163, extends from a second downstream edge BA161, opposite the first upstream edge. Each unit 163 has been cut out of the second element 16 and has a cut tangential edge 164 (the tangential direction is materialized by the arrow T on the figures, the corresponding cutting line 165 is schematically shown in [Fig.3]).In this example, the cutting line 165 extends along the DR deflection and is located on its side, for example, so as to leave a minimum of material on the DR side, and thus minimize the tangential gap between two adjacent units 163, each belonging to a respective portion 14. The cuts to form the units 163 are non-through, meaning they are made only in the second element 16 (not in the first element 15). Each unit 163 is deployed transversely to the corresponding axial edge BA161, and more generally transversely to the first element 15 (according to the deployment arrows fl illustrated in [Fig. 4]). Each unit 163 can have a substantially rectangular shape. The areas 161 of the portions 14 can have a tangential edge BT161 on a respective tangential end of the preform 10.The units 163 can extend to a tangential end of the preform 10, thus giving the reinforcement of the slats a maximum extent along the tangential direction T.

[0047] The example just described, in connection with figures 2 to 4, presents for each portion 14 a single woven zone 161. The invention is not limited to this case however, as will now be described in connection with the second example of preform 20 illustrated in figures 5 to 7 which implements two woven zones per unbound portion.

[0048] According to this example, each portion 24 comprises a first textile element 25 that defines a platform reinforcement, and a second textile element 26 that comprises two zones 261 woven with the first element 25, located radially outside with respect to the first element 15, each having a first axial edge BA261a on a distinct axial end of the preform 20 and a second axial edge BA261b opposite the first edge BA261a. The second element 26 further comprises two textile units 263, each extending from a second axial edge BA261b of a distinct woven zone 261. The units 263 are separated from each other by cutting In the second element 26: each unit 263 has a cut edge 264b (the corresponding cut line 265b that results in the separation of the two units 263 is shown schematically in [Fig. 6]). Each unit 263 also has a cut tangential edge 264a (the corresponding cut line 265a is shown schematically in [Fig. 6]). The cut line 265a extends along the debond DR and is located on its side, for example, so as to leave a minimum of material on the latter's side, and thus minimize the tangential gap between two neighboring units 263, each belonging to a respective portion 24. The cut line 265b is transverse to the cut line 265a, for example, perpendicular to it, as illustrated. The cuts to form the units 263 are non-through, that is to say they are made only in the second element 26 (not in the first element 25).Each unit 263 is deployed transversely to the corresponding second axial edge BA261b, and more generally transversely to the first element 25 (according to the deployment arrows f2 illustrated in [Fig. 7]). Each unit 263 can have a substantially rectangular shape. The zones 261 of each portion 24 can have a tangential edge BT261 on a respective tangential end of the preform 20. The units 263 can extend to a tangential end of the preform 20, thus giving the reinforcement strip a maximum extent along the tangential direction T.

[0049] The examples just described concern textile units without significant overlap with the woven areas of the second elements. However, the invention is not limited to this type of arrangement, as will now be described with reference to Figures 8 to 14.

[0050] Figures 8 to 11 relate to a third example of preform 30 according to the invention.

[0051] According to this example, each portion 34 comprises a first textile element 25 that defines a platform reinforcement, and a second textile element 36 that comprises, on the side of each axial end of the preform 30, a woven area 361 with the first element 25 and located radially outside the latter. The area 361 has a first edge BA361a on an axial end of the preform 30 and a second axial edge BA361b, opposite the first edge BA361a, not perpendicular to the axial direction A, forming, for example, an angle between 30° and 60° with respect to this direction. The area 361 is located on the side of the debonding DR. The area 361 further comprises a tangential edge BT361 connecting the first edge BA361a to the second edge BA361b. The edge BT361 is located on the side opposite the debonding DR.The zone 361 extends over only a part of the tangential dimension of the corresponding portion 34, in particular the edge BT361 is separated from a tangential end of the preform 30 by a non-zero distance.

[0052] Each portion 34 further comprises, on the side of each axial end of the preform 30, a textile unit 363 extending from the second edge BA361b and separated by a cut from a detached zone 366 of the second element 36 extending from the tangential edge BT361. The zone 366 extends the zone 361 from the edge BT361 to a tangential end of the preform 30. The detached zone 366 extends from the zone 361 and extends it on the side opposite the detachment DR. The unit 363 thus has a first cut edge 364a and the zone 366 also has a cut edge 366a (the corresponding cut line 365a for separating these two edges is shown schematically in [Fig. 10]). Unit 363 is detached from the first element 35 and comprises a first section 363a extending from the second edge BA361b and folded over area 361 so as to partially cover it. The first section 363a is folded along a fold line corresponding to the second edge BA361b (arrow f3a in [Fig.

[11] illustrates this fold). The first section 363a extends to a deployment fold 363p, from which a second section 363b of unit 363 extends, deployed transversely to the first section 363a to define the reinforcement of the slats (arrow f3b in [Fig. 11] illustrates this deployment). As can be seen in particular in [Fig. 9], the tangential dimension of the second section 363b increases in the R direction as one moves away from the fold 363p. The units 363 are separated from each other by cutting: each unit 363 has a cut edge 364b (the corresponding cut line 365b that results in the separation of the two units 363 is shown schematically in [Fig. 10]). The cuts to form the units 363 are non-through, that is to say they are made only in the second element 36 (not in the first element 35).

[0053] Figures 12 to 14 relate to a fourth example of preform 40 according to the invention in which the units also cover the woven areas of the second elements, as just described in connection with the third example.

[0054] According to this example, each portion 44 comprises a first textile element 45 that defines a platform reinforcement, and a second textile element 46 that comprises two woven areas 461, with the first element 45 each having a first axial edge BA461a on a distinct axial end of the preform 40 and located radially inward with respect to the first element 45. The second element 46 further comprises two textile units 463, each extending from a second axial edge BA461b, opposite the first edge BA461a, of a distinct woven area 461. The units 463 are separated from each other by a cut in the second element 46: each unit 463 having a cut edge 464b (the corresponding cut line 465b that results in the separation of the two units 463 is shown schematically in [Fig. 13]). Each unit 463 also has a cut tangential edge 464a (the corresponding cut line 465a is shown schematically in [Fig. 13]). The line of Cut 465a extends along the DR joint and is located on its side, for example, so as to leave a minimum of material on the latter's side, and thus minimize the tangential gap between two neighboring units 463, each belonging to a respective portion 44. The cutting line 465b is transverse to the cutting line 465a, for example, perpendicular to it, as illustrated. The cuts to form the units 463 are non-through, that is, they are made only in the second element 46 (not in the first element 45). Each unit 463 is unbound from the first element 45 and includes a first section 463a extending from the corresponding second edge BA461b and forming a first fold 463pl around the first edge BA461a of the corresponding woven area 461 so as to be positioned radially outside relative to the first element 45 (see arrows f4a in [Fig. 14]).The first section 463a is folded along a fold line corresponding to the first edge BA461a so as to cover the underside of the corresponding woven area 461 and the top of part of the first element 45. The first section 463a extends to a second fold 463p2 from which extends a second section 463b of the unit which is deployed transversely to the first section 463a to define the reinforcement of the swages (arrow f4b in [Fig. 14] illustrates this deployment).

[0055] We have just described various examples of fibrous blade preforms according to the invention. The blade is then obtained by forming a ceramic matrix in a porosity of the preform.

[0056] The formation of this matrix relies on techniques known per se. For example, at least part of the matrix can be produced by chemical vapor infiltration. This allows a silicon carbide matrix phase to be obtained. As an example, chemical vapor infiltration can be limited to the formation of a consolidation phase that incompletely densifies the preform but is sufficient to allow it to maintain its shape without the assistance of holding tools, and the formation of the ceramic matrix can be completed by another technique. In this respect, the matrix formation can be continued by reactive or non-reactive melt infiltration. A SiC matrix, or even a Si-SiC matrix, can be formed by infiltrating a molten silicon composition or a molten silicon alloy.

[0057] Once obtained, protective coatings, for example environmental barrier coatings, can be applied conventionally to the blade.

[0058] The invention is applicable to different types of turbomachine blades, in particular compressor and turbine blades of different gas turbine bodies, for example a low pressure turbine runner blade, such as that illustrated in [Fig.15].

[0059] The blade 100 of [Fig.15] comprises, a blade 101 whose reinforcement is formed by the first part of the preform which has been described above, a foot 102 formed by a thicker part, for example with a bulb-shaped cross-section, extended by a stilt 103, an inner platform 110 located between the stilt 103 and the blade 101 and an outer platform 120 equipped with scrapers, in the vicinity of the free end of the blade, formed by the second part of the preform described above.

[0060] The blades 100 can then be mounted on a turbine disc by positioning the foot 102 of the blades 100 in a corresponding housing of the disc.

[0061] The components according to the invention can be fixed to different types of turbine rotors, in particular compressor and turbine rotors of various gas turbine bodies, for example a low-pressure (LP) turbine rotor disc. Components according to the invention can be fixed to low- or high-pressure turbojet turbines.

[0062] Although the present invention has been described with reference to specific embodiments, those skilled in the art will recognize that modifications and changes can be made to these examples without departing from the general scope of the invention as defined by the claims. In particular, individual features of the various embodiments illustrated / mentioned can be combined in additional embodiments. Therefore, the description and drawings should be considered in an illustrative rather than a restrictive sense.

Claims

Demands

1. A fibrous preform (10; 20; 30; 40) of a turbomachine blade (100) woven in a single piece of three-dimensional fabric, comprising: - a first part (12; 22; 32; 42) defining a reinforcement of an aerodynamic profile having, at one apex, a radial unbundle (DR), and - a second part which is formed by fibrous portions (14; 24; 34; 44) each originating from the first part and unbundled from the radial unbundle, each fibrous portion being folded over a respective side of the first part and transversely to the latter, each unbundled portion comprising a first textile element (15; 25; 35; 45) defining a platform reinforcement, and a second textile element (16; 26; 36; 46) comprising (i) at least one woven zone (161; 261; 361; 461) with the first element and offset along a radial direction (R) relative to the latter, and (ii) two textile units (163; 263; 363;463) cut out of the second element and extending from said at least one woven area, said units being detached from the first element and deployed transversely to the latter to define a reinforcement of slats.;

2. Fibrous preform (10) according to claim 1, wherein the second textile element (16) of each unbound portion (14) comprises (i) a woven area (161) with the first element (15) and located radially outside with respect to the first element, and (ii) two textile units (163) unbound from the first element and each extending from a distinct axial edge (BA161) of the woven area, each textile unit being obtained by cutting from the side of the radial unbinding (DR) and being deployed transversely to the corresponding axial edge.

3. A fibrous preform (20) according to claim 1, wherein the second textile element (26) of each unbound portion (24) comprises (i) two woven zones (261) with the first element (25), each having a first axial edge (BA261a) on a distinct axial end of the preform and located radially outside with respect to the first element, and (ii) two textile units (263), separated from each other by cutting, each extending from a second axial edge (BA261b), opposite the first axial edge, of a zone

4.

5. woven separately, the textile units being unbound from the first element and each textile unit being obtained by cutting from the radial unbinding side (DR) and deployed transversely to the corresponding second axial edge. Fibrous preform (30) according to claim 1, wherein the second textile element (36) of each unbound portion (34) comprises, on the side of each axial end of the preform, (i) a woven zone (361) with the first element (35) and located radially outside with respect to the first element, the woven zone having a first axial edge (BA361a) on an axial end of the preform, a second axial edge (BA361b), opposite the first axial edge, not perpendicular to an axial direction (A) and a tangential edge (BT361) connecting the first axial edge to the second axial edge, and (ii) a textile unit (363) extending from the second axial edge and separated by cutting from a unbound zone (366) of the second element extending from the tangential edge,the textile unit being detached from the first element and comprising a first section (363a) extending from the second axial edge and folded over the woven area so as to partially cover it up to a deployment fold (363p) and a second section (363b) extending from this deployment fold and deployed transversely to the first section to define the hem reinforcement, the units being separated from each other by cutting. A fibrous preform (40) according to claim 1, wherein the second textile element (46) of each unbound portion (44) comprises (i) two woven zones (461) with the first element (45), each having a first axial edge (BA461a) on a distinct axial end of the preform and located radially inward with respect to the first element, and (ii) two textile units (463), separated from each other by cutting, each extending from a second axial edge (BA461b), opposite the first axial edge, of a distinct woven zone, the textile units being unbound from the first element and each textile unit being obtained by cutting from the side of the radial unbound (DR) and comprising (a) a first section (463a) extending from the corresponding second axial edge and forming a first fold (463p1) around the first axial edge of the corresponding woven zone so as to be positioned radially outward with respect to to the first element,the first section extending to a second fold (463p2), and (b) a second, section (463b) extending from this second fold and deployed transversely to the first section to define the lick reinforcement.

6. Turbomachine blade (100) made of ceramic matrix composite material, comprising a fibrous reinforcement formed by a preform (10; 20; 30; 40) according to any one of claims 1 to 5, and a ceramic matrix densifying said reinforcement.

7. Blade (100) according to claim 6, wherein the blade is a turbine blade.

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