COMPOSITE OUTER HOUSING CLAMP FOR AN AIRCRAFT TURBINE ENGINE

Description

TECHNICAL FIELD

[0001] The invention relates to the field of intermediate housings for aircraft turbomachinery, and more specifically to the manufacture of the outer shell of such an intermediate housing.

[0002] An intermediate casing ferrule of an aircraft turbomachine is for example known from document FR 2 925 120 A1 and document US 206 / 047275. PREVIOUS STATE OF THE ART

[0003] A turbomachine mounting mast, also known as an "EMS" (Engine Mounting Structure), or simply a "pylon" or "engine pylon," is typically used to suspend the turbomachine beneath the aircraft's wing. It serves as the interface between the turbomachine and a specific structural component of the aircraft, often the forward wing box. It transmits the forces generated by the turbomachine to the aircraft's structure and also allows for the routing of fuel, electrical, hydraulic, and air systems between the turbomachine and the aircraft.

[0004] The nacelle is conventionally equipped with several hoods that enclose the turbomachine, allowing access to it in the open position. These hoods are known as fan hoods and thrust reverser hoods, the latter being hinged to the primary structure of the mounting mast.

[0005] The turbojet engine comprises a fan casing extended rearward by an intermediate casing, consisting of an outer ring, an inner hub, and structural arms arranged angularly and extending radially between the hub and the outer ring, which they connect. The intermediate casing thus corresponds to the structural element positioned between the fan casing located further upstream and the nacelle cowlings located further downstream. More precisely, the annular downstream end of the intermediate casing is dedicated to providing the interface between this intermediate casing and the nacelle cowlings, typically the thrust reverser cowlings.

[0006] The annular downstream end of the intermediate housing forms a peripheral annular, or nearly annular, groove, open radially outwards. This groove is designed to receive a supplementary connecting element provided on the thrust reverser cowlings, and it is further delimited by an upstream groove wall and a downstream groove wall, both of which are radial walls. The supplementary connecting element can thus be a radial rib extending inwards, so as to fit into the groove between the two upstream and downstream walls. The interaction between the rib and the groove allows the transmission of aerodynamic forces from the nacelle to the turbomachine during takeoff, flight, and landing, particularly axial forces, and even more specifically, the axial counter-thrust forces when the thrust reverser systems equipping the nacelle cowlings are actuated.

[0007] This arrangement, characterized by the simple penetration of the rib into the groove, allows for easy and rapid opening of the reversing gear covers hinged to the mast. This opening is necessary, for example, to perform maintenance on the aircraft while it is parked on the ground. Several solutions are known for manufacturing the outer shell of the intermediate housing, including one that involves making the shell body from a composite material and attaching a downstream metallic end structure to it, which defines the groove.

[0008] The outer ferrule's body is therefore manufactured from a composite material, usually from a fibrous reinforcement densified by a matrix, preferably resin, such as epoxy resin. In this case, the body is made from a fibrous preform that can be obtained in various ways known to those skilled in the art, typically by three-dimensional weaving of yarns (3D weaving), or by draping two-dimensional fibrous fabrics.

[0009] The use of a composite material for the outer shell reduces the mass of the turbomachine, but this mass is still impacted by the presence of the metallic downstream end structure defining the peripheral groove, as well as by the mechanical fastening means required at the interface, such as bolts.

[0010] The invention therefore aims to further reduce the mass of the outer shell of the intermediate housing, while offering a design that facilitates its manufacture. DESCRIPTION OF THE INVENTION

[0011] To meet the purpose identified above, the invention first relates to an outer shell of an intermediate housing for an aircraft turbomachine, the shell made of composite material comprising an annular downstream connecting end forming a peripheral groove open radially outwards, said groove being intended to receive a complementary connecting element provided on one or more nacelle hoods, and this groove being delimited by an upstream groove wall, as well as by a downstream groove wall.

[0012] According to the invention, the ferrule is made from: of a first fibrous preform obtained by three-dimensional weaving of yarns and densified by a matrix, the first preform defining a barrel of the ferrule as well as a structural part of the downstream wall of the groove, projecting radially outwards from the barrel; and of a second fibrous preform or of a group of second fibrous preforms, each second fibrous preform being obtained by three-dimensional weaving of yarns and densified by a matrix, the second preform or the group of second preforms defining a base attached externally to the barrel defined by the first preform, as well as a structural part of the upstream wall of the groove, projecting radially outwards from the barrel.

[0013] The invention offers the advantage of reduced mass due to its all-composite design and the absence of mechanical fasteners such as bolts. This reduction in the mass of the outer shell leads to a decrease in the turbomachine's specific fuel consumption, thus contributing to a reduction in greenhouse gas emissions.

[0014] Furthermore, the invention advantageously provides for the production of the peripheral groove using two preforms, simplifying their shape and consequently facilitating their manufacture. Since the downstream wall of the groove is subjected to the greatest mechanical stress during the counter-thrust phases, it is particularly advantageous to integrate the structural portion of this downstream wall within a single preform that also defines the barrel of the ferrule, corresponding to the most substantial structural part of this outer ferrule of the intermediate housing. As the upstream wall of the groove is subjected to less mechanical stress from the nacelle covers, its formation from a dedicated preform, applied to the other preform, constitutes a perfectly appropriate technical solution.

[0015] The invention preferably provides at least one of the following optional features, taken individually or in combination.

[0016] Preferably, in the case of a second fibrous preform, that is to say with a single second woven 3D fibrous preform, it has an annular or substantially annular shape centered on a longitudinal central axis of the ferrule, and in the other case of a group of second fibrous preforms, each of them has the form of an angular sector to together form an annular or substantially annular structure centered on the longitudinal central axis of the ferrule.

[0017] Preferably, the ferrule includes an anti-friction coating covering the upstream and downstream walls of the groove, inside the groove. This anti-friction coating is preferably a fabric or a shim. The anti-friction coating reduces friction between the outer ferrule and the nacelle covers at the groove forming the interface between these elements. This limits wear on these elements and increases their service life.

[0018] Preferably, the ferrule also includes a third fibrous preform or a group of third fibrous preforms, each third fibrous preform being obtained by three-dimensional weaving of yarns and densified by a matrix. The third preform or group of third preforms defines a base attached internally to the shaft defined by the first preform, as well as a structural sealing surface projecting axially downstream beyond the downstream wall of the groove. The third preform, or each preform in the group of third preforms, is preferably unbound during weaving so as to also define an additional base attached externally to the downstream wall of the groove. While this additional base remains optional, it is noted that it reinforces the mechanical strength of the structural sealing surface.

[0019] The invention also relates to an aircraft turbomachine comprising such an outer shell of an intermediate casing. The turbomachine is preferably a turbojet, preferably a turbofan and / or a twin-spool turbojet, but other types of turbomachines are also conceivable, such as a turboprop, without departing from the scope of the invention. Most preferably, the invention relates to a very high bypass ratio turbojet, also known as an UHBR (Ultra High Bypass Ratio) turbojet.

[0020] The invention also relates to a method for manufacturing an outer shell of an intermediate housing for an aircraft turbomachine, the shell made of composite material comprising an annular downstream connecting end forming a peripheral groove open radially outwards, said groove being intended to receive a complementary connecting element provided on one or more nacelle covers, and this groove being delimited by an upstream groove wall, as well as by a downstream groove wall.

[0021] According to the invention, the process comprises the following steps: fabrication of a first fibrous preform by three-dimensional weaving of yarns, the first preform being intended to define a barrel of the ferrule as well as a structural part of the downstream wall of the groove, projecting radially outwards relative to the barrel; fabrication of a second fibrous preform or a group of second fibrous preforms, each second preform being fabricated by three-dimensional weaving of yarns, the second preform or group of second preforms being intended to define a base as well as a structural part of the upstream wall of the groove, projecting radially outwards relative to the barrel; injection and polymerization of a densification matrix of the first preform; and injection and polymerization of a densification matrix of the second preform or group of second preforms, so that the base is attached fixedly and externally to the barrel of the ferrule.

[0022] The advantages associated with this manufacturing process are those mentioned above, in relation to the outer shell, which is also the subject of the invention. As will be detailed below, the various die injection stages can be carried out simultaneously, by co-injection, or successively.

[0023] Indeed, for example, the injection of a densifying matrix for the first preform is carried out simultaneously with the injection of a densifying matrix for the second preform or group of second preforms, preferably through matrix co-injection in a flexible injection mold, a rigid mold matrix transfer mold, or a hybrid flexible injection and rigid mold matrix transfer mold. The injection technique used with the rigid mold matrix transfer mold is preferably resin transfer molding, or RTM (Resin Transfer Molding). The injection technique used with the flexible injection mold is preferably impregnation in an impregnation chamber partially defined by a flexible, impermeable membrane.This technique is possibly implemented using a compaction chamber separated from the impregnation chamber by the membrane, as is known for example from document WO2018 / 234669A1.

[0024] Either of these two preferred injection techniques can indeed be chosen for the production of the outer shell, or they can preferably be combined.

[0025] According to another embodiment of the outer shell, a densifying matrix for the first preform is first injected and polymerized, preferably in a rigid mold matrix transfer tool. Then, in a subsequent curing step, a densifying matrix for the second preform or group of second preforms is injected and polymerized, preferably in a rigid mold matrix transfer tool. In this example, the consolidation of the second preform or group of second preforms thus occurs after the consolidation of the first preform. Also in this example, other types of tooling and other injection methods can be used without departing from the scope of the invention.

[0026] Preferably, the process includes applying an antifriction coating to the upstream and downstream walls of the groove, inside the groove. The antifriction coating is preferably applied by co-firing during the firing of the first and second preforms or groups of second preforms, or bonded to the upstream and downstream walls of the groove after firing. Preferably, the process also includes: the production of a third fibrous preform or a group of third fibrous preforms, each third preform being produced by three-dimensional weaving of yarns, the third preform or group of third preforms being intended to define a base as well as a structural bearing surface of sealing joint projecting axially downstream beyond the downstream wall of groove; and injection and polymerization of a densification matrix of the third preform or group of third preforms, so that the base is attached fixedly and internally to the barrel of the ferrule.

[0027] Here too, the cooking of the third preform or group of third preforms can be carried out by co-cooking during the cooking of the first preform, or during a subsequent cooking step.

[0028] Finally, the process may also include the application of an antifriction coating covering the structural joint surface. In this case, the antifriction coating is preferably applied by co-firing during the firing of the third preform or group of third preforms, or bonded after said firing.

[0029] Other advantages and features of the invention will appear in the detailed, non-limiting description below. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] This description will be made with reference to the attached drawings, among which are; [ Fig. 1 ] represents a half-axial cross-sectional view of an aircraft turbomachine, according to a preferred embodiment of the invention; [ Fig. 2 ] represents a perspective view of the outer shell of the intermediate casing equipping the turbomachine shown in the previous figure; [ Fig. 3] represents a partial enlarged axial cross-sectional view showing the cooperation between the outer shell of the intermediate housing and a nacelle cover; Fig. 4 ] represents a partial axial half-section view of the outer shell, before the matrix injection and polymerization steps; [ Fig. 5 ] represents a view similar to that of the figure 4 , during the matrix injection and polymerization steps; [ Fig. 6 ] is a view similar to that of the figure 4 , with the outer ferrule appearing in another embodiment; and [ Fig. 7 ] is a view similar to that of the figure 6 , with the outer ferrule appearing in the form of another embodiment. DETAILED DESCRIPTION OF SPECIFIC METHODS OF IMPLEMENTATION

[0031] With reference first and foremost to the figure 1Figure 1 represents an aircraft turbomachine according to a preferred embodiment of the invention. This is a twin-spool, turbofan engine. However, it could be a turbomachine of another type, for example a turboprop, without departing from the scope of the invention.

[0032] The turbojet 1 has a central longitudinal axis 2 around which its various components extend. It comprises, from upstream to downstream along a main direction 5 of gas flow through this turbojet, a fan 3, a low-pressure compressor 4, a high-pressure compressor 6, a combustion chamber 11, a high-pressure turbine 7 and a low-pressure turbine 8.

[0033] Conventionally, after passing through the blower, the air splits into a central primary flow 12a and a secondary flow 12b that surrounds the primary flow. The primary flow 12a flows into a main gas circulation channel passing through the compressors 4, 6, the combustion chamber 11, and the turbines 7, 8. The secondary flow 12b, on the other hand, flows into a secondary channel radially delimited outwards by an engine casing, surrounded by a nacelle 32.

[0034] The engine casing is divided into several elements, among which is an intermediate casing 21, comprising an outer ring 23 located in the downstream aerodynamic extension of a fan casing 12. The intermediate casing 21 also includes a hub 26 formed by transverse flanges 25, 27 arranged radially internally with respect to the outer ring 23, the casing 21 further comprising structural arms 17 distributed angularly and extending radially to connect the outer ring 23 and the hub 26.

[0035] The turbojet also includes a central casing 16, also called the "core" casing, extending downstream from the hub 26 of the intermediate casing 21, to which it is connected. It should be noted that the central casing extends to a larger rear end 19, also called the exhaust casing.

[0036] As is known and will be detailed later, the outer ferrule 23 of the intermediate housing has a downstream end connecting with a peripheral groove, the main purpose of which is to establish a connection between this outer ferrule 23 and the nacelle covers directly adjacent downstream.

[0037] The nacelle 32 forms a continuous aerodynamic outer surface using various adjacent elements which follow one another from upstream to downstream, including an air inlet 34, fan cowls 36, thrust reverser cowls 38, and a fixed rear cowling 40.

[0038] The thrust reverser cowls 38, generally two in number and hinged on the rigid structure of a mounting mast of the turbojet 1, delimit in a known way an annular secondary flow channel 42, by means of external annular skins 44 and internal annular skins 43.

[0039] Each thrust reverser hood 38, also called the rear hood or "core" hood, has a general half-cylinder shape, with its upper end intended to be hinged to the rigid structure of the mast, and its lower end intended to be locked to the lower end of the other hood 38, by conventional means.

[0040] With its upstream end, and in its closed position, each reversing gear cover 38 is therefore connected to the annular downstream end of the outer ferrule 23 of the intermediate housing. figure 2 shows the outer ferrule 23 on a larger scale, while the figure 3 represents the cooperation between this ferrule 23 and the reversing gear covers 38 (only one of them being visible on this figure 3 ).

[0041] The outer shell 23, also the subject of the present invention, extends around a central longitudinal shell axis, corresponding to the axis 2 of the turbojet engine. The structural part of the outer shell 23 is made entirely of composite material, forming a single piece incorporating successively, from upstream to downstream, an upstream radial flange 42 for attachment to the fan casing, a shell body 45 of substantially cylindrical shape and circular cross-section, and finally the annular downstream connecting end 46. This latter forms a peripheral groove 48 open radially outwards, of annular or substantially annular shape. Indeed, this groove 48 can be interrupted by notches 51, for example, two axial notches 51 passing through the annular downstream connecting end 46 in diametrically opposite clockwise positions, at 12 o'clock and 6 o'clock, as is known to those skilled in the art.

[0042] The groove 48, for example, generally adopts a V-shape and receives a rib 50 provided on the upstream end of each reversing gear cover 38. As can be seen on the figure 3 The rib 50 preferably extends radially inwards, with a general V-shape complementary to that of the groove 48. Each rib 50 preferentially extends over an angular sector of approximately 180°, or a slightly smaller angle. It thus constitutes a complementary connecting element cooperating with the groove 48 to create the interface between the ferrule 23 and each cover 38.

[0043] The annular groove 48 is delimited axially on one side by means of an upstream wall of the groove 52, and on the other side by means of a downstream wall of the groove 58. Each of these walls 52, 58 extends radially outwards with respect to the shaft 45, and has an annular shape centered on the axis 2, or a substantially annular shape if axial notches 51 are made.

[0044] The cooperation between the peripheral groove 48 and each complementary rib 50 allows the transmission of aerodynamic forces from the reverser cowls 38 to the turbojet, in particular axial forces, and even more particularly axial counter-thrust forces.

[0045] Downstream of the downstream wall of groove 58, the connecting end 46 has a structural bearing surface 60 for a sealing gasket. This bearing surface 60 projects axially downstream from the downstream wall of groove 58, and it receives a sealing gasket 62 carried by the upstream end of the inverter cover 38. This gasket 62 can thus compress onto the structural bearing surface 60 when the cover 38 is closed, but also compress onto the downstream surface of the downstream wall of groove 58, as shown in the figure. figure 3 .

[0046] Now, referring to the figure 4 The diagram shows the different elements from which the outer ferrule 23 is made. It is noted that its construction, described as "all composite", implies the absence of mechanical means of fastening between its different parts, therefore the absence of bolts, rivets, etc.

[0047] On the figure 4The constituent elements of the ferrule 23 are represented in a state corresponding to that before their impregnation by a resin-type matrix, preferably an epoxy resin, and therefore before the baking step(s) leading to the polymerization / consolidation of the resin. figure 4 This therefore represents, in particular, fibrous preforms all made by 3D weaving of yarns, intended to be densified by the resin injected subsequently. Typically, the fibers used to make the preforms are carbon fibers, although other conventional materials can be considered without departing from the scope of the invention.

[0048] First, a first fibrous preform 64 is planned, intended to define the upstream flange for fixing the ferrule (not visible on the figure 4), the shaft 45, as well as a structural portion 66 of the downstream wall of the groove 58. The portion 66 extends radially outwards from the shaft, adopting an annular or substantially annular shape. This structural portion 66 of the downstream wall of the groove 58, defined by the first preform 64, extends over the entire radial length of the finalized downstream wall of the groove 58, or over substantially its entire length. The first preform 64 is thus preferentially annular, centered on axis 2, and has a generally U-shaped cross-section.

[0049] Next, a second fibrous preform 68, or a group of second fibrous preforms, is planned. The choice between these two solutions is dictated by how the upstream wall of the groove 52 is to be formed: either as a single continuous piece in the circumferential direction, or in a sector-like fashion in the same direction. In the first case of a single second fibrous preform 68, it has an annular or substantially annular shape centered on axis 2, and in the second case of a group of second fibrous preforms, each of them has an angular sector shape to together form an annular or substantially annular structure centered on this same axis 2. For example, this could involve two angular sectors, each approximately 180°.

[0050] Subsequently, only the first case will be considered, it being specified however that the principle remains identical or similar when a sectorized realization of the upstream wall of groove 52 is carried out, which may be motivated by the presence of the aforementioned axial notches on the ferrule 23.

[0051] Thus, the second fibrous preform 68 is woven in such a way as to define a base 70 intended to be attached fixedly and externally to the shaft 45, on a downstream end of the latter, and also in such a way as to define a structural part 72 of the upstream wall of groove 52, projecting radially outwards relative to the shaft 45.

[0052] Instead of being strictly radial as the structural part 66 of the downstream wall of groove 58 may be, the structural part 72 of the upstream wall of groove 52 may be inclined upstream, so as to provide the desired general V shape for the groove 48. In this hypothesis, the hollow defined by the radius of connection between this structural part 72, and the outer surface of the base 70, may be filled with a filling material 74, preferably polymerizable.

[0053] The structural portion 72 extends radially outwards relative to the shaft 45 and the base 70, adopting an annular or substantially annular shape. This structural portion 72, defined by the second preform 68, extends along the entire radial length of the upstream wall of the completed groove 52, or along substantially its entire length. The second preform 68 is thus preferentially annular, centered on axis 2, and has a generally V-shaped cross-section, open axially upstream and radially outwards.

[0054] To reduce friction between the two groove walls 52, 58 and the rib of the nacelle hoods designed to fit into the groove 48, the ferrule 23 includes an anti-friction coating 76 that conforms to all or part of the inner surface of this groove. In particular, the coating 76 covers both the upstream and downstream walls 52, 58, and more specifically the two structural parts 72, 66 defined by the preforms 64, 68. For illustrative purposes, it is noted that the V-shaped anti-friction coating 76, complementary to that of the groove 48, may have gripping ribs (not shown) to facilitate attachment to the preforms 64, 68, and / or may extend radially outwards to cover the ends of the structural parts 66, 72, in order to protect them against impacts. Such achievements are known for example from document FR 2 994 216 A1.

[0055] The anti-friction coating 76 can be a fabric intended to be impregnated and baked at the same time as the first and second fibrous preforms 64, 68. Alternatively, it can be a shim, for example metallic, glued to the groove walls 52, 58 in a later phase, after baking them.

[0056] When positioning the aforementioned elements, a gap may form between the following elements: the outer surface of the first preform 64, at the level of the bottom of the groove 48; the anti-friction coating 76; and the radius of connection between the base 70 and the structural part 72 defined by the second preform 68.

[0057] This hollow can also be filled using a 78 filler material, preferably polymerizable.

[0058] Next, a third fibrous preform 80, or a group of third fibrous preforms, is planned. Here again, only the first case of a single third fibrous preform will be described, it being specified, however, that the principle remains identical or similar when a sectorized realization of the structural span of joint 60 is carried out.

[0059] Thus, the third fibrous preform 80 is woven in such a way as to define a base 82 intended to be attached fixedly and internally to the shaft 45, on a downstream end of the latter, and also in such a way as to define the structural span of joint 60, projecting axially downstream beyond the downstream wall of groove 58.

[0060] Preferably, a loose weave is made of the third preform 80, so as to also define an additional base 84 intended to be attached externally to a downstream surface of the structural part 66 defined by the first preform 64. The additional base 84 not only reinforces the mechanical strength of the structural joint span 80 on the ferrule, but it also reinforces the structural part 66 of the downstream wall of the groove 58, running along it, preferably over its entire radial length or substantially over its entire length.

[0061] The third preform 80 is thus preferentially annular, centered on axis 2, and of semi-section in the general shape of a Y open axially upstream and radially outwards.

[0062] To reduce friction with the joint, another anti-friction coating 86 can conform to the downstream outer surface of the additional base 84, and / or the structural span 60.

[0063] The anti-friction coating 86 can here also be a fabric intended to be impregnated and baked at the same time as the first, second and third fibrous preforms 64, 68, 80. Alternatively, it can be a shim added later by gluing, after consolidation of the rest of the ferrule.

[0064] During the positioning of the third preform 80, a gap may form between the following elements: the base 82 defined by the third preform 80; the additional base 84 defined by the third preform 80; the radius of connection between the shaft 45 and the structural part 66 defined by the first preform 64.

[0065] This hollow can also be filled using a filler material 88, preferably polymerizable.

[0066] Now, referring to the figure 5 , a resin injection step is shown using hybrid tooling, this resin injection being intended for the impregnation of the fibrous preforms 64, 68, 80 described with reference to the figure 4 , as well as to the impregnation of the fabrics forming the anti-friction coatings 76, 86.

[0067] The hybrid tooling 90 not only allows the co-injection of resin for the impregnation of all the elements 64, 68, 80, 76, 86, but it also allows their co-curing leading to the polymerization of the resin which impregnates them, as well as the co-curing of the filling materials 74, 78, 88.

[0068] To achieve this, the hybrid tooling 90 used is, for example, a combination of a tooling 92 for resin transfer in rigid mold (RTM type), and a tooling 94 for flexible injection.

[0069] More specifically, the rigid mold portions 96 are arranged on either side of the upstream and downstream walls of groove 52, 58, as well as inside groove 48. The rigid tooling 92 is thus positioned to cooperate with the annular downstream connecting end of the outer shell 23.

[0070] Furthermore, the flexible injection mold 94 includes a flexible, impermeable membrane 98, covering the outer surface of the barrel 45 defined by the first preform 64, extending onto the outer surface of the base 70 defined by the second preform 68. One or more seals 99 are interposed and compressed between the end of the membrane 98 resting on the base 70 and one of the rigid mold portions 96 of the RTM-type mold 92. The membrane 98 allows pressure to be applied to the part to be consolidated during resin injection, either by creating a vacuum in the impregnation chamber it defines, or by means of a compaction chamber located on the opposite side of this membrane 98.

[0071] Using this hybrid tooling 90, the resin is co-injected to impregnate all the fibrous elements 64, 68, 80, 76, and 86 in a single phase. The heating provided by this tooling also allows for the co-curing of these elements, as well as the co-curing of the filler materials 74, 78, and 88. The resin, combined with all the elements 64, 68, 80, 76, 86, 74, 78, and 88, can thus co-polymerize during the same heating phase. After this co-curing phase, a single, all-composite part is produced, with all the consolidated / densified elements bonded firmly to one another.

[0072] Numerous alternatives are possible, particularly due to the optional nature of many parts of the shell described above, such as the anti-friction coatings 76 and 86, the sealing surface 60, or the additional base 84 when such a sealing surface is required. Other alternatives also arise from the fact that firing is not necessarily carried out simultaneously for all the shell components; a phased firing process can be implemented to perform successive firings, instead of a single, simultaneous firing as described above.

[0073] Thus, another preferred embodiment is shown on the figure 6in which the third preform 80 comprises only the base 82, and not the additional base. For this embodiment, the co-firing of the three preforms 64, 68, 80 remains possible, but a subsequent firing of the third preform 80 could be carried out, after consolidation of the first and second preforms 64, 68.

[0074] Yet another preferred embodiment is shown on the figure 7 , on which the third preform 80 is no longer planned, due to the non-need for the joint support 60. For this embodiment, the co-firing of the two preforms 64, 68 remains possible, but a subsequent firing of the second preform 68 could be carried out, after consolidation of the first fibrous preform 68, which then serves as a support on which the second preform 68 would be consolidated / densified.

[0075] Of course, various modifications can be made by a person skilled in the art to the invention just described, only by way of non-limiting examples and whose scope is defined by the attached claims.

Claims

1. Exterior ferrule (23) of an intermediate casing (21) for an aircraft turbine engine, the ferrule made from composite material comprising an annular connecting downstream end (46) forming a peripheral groove (48) radially open towards the outside, said groove (48) being intended to receive a complementary connecting member (50) provided on one or more nacelle cowls (38), and this groove being delimited by an upstream groove wall (52), as well as by a downstream groove wall (58), the ferrule being produced from: - a first fibrous preform (64) obtained by three-dimensional weaving of threads and densified by a matrix, the first preform (64) defining a barrel (45) of the ferrule and a structural part (66) of the downstream groove wall (58), projecting radially outwards with respect to the barrel; and characterized in that the ferrule is also produced from - a second fibrous preform (68) or a group of second fibrous preforms, each second fibrous preform (68) being obtained by three-dimensional weaving of threads and densified by a matrix, the second preform (68) or the group of second preforms defining a base (70) externally attached to the barrel (45) defined by the first preform (64), as well as a structural part (72) of the upstream groove wall (52), projecting radially outwards with respect to the barrel.

2. Ferrule according to claim 1, characterised in that, in the case of a second fibrous preform (68), this has an annular or substantially annular shape centred on a longitudinal central axis (2) of the ferrule, and in that, in the other case of a group of second fibrous preforms (68), each of them is in the form of an angular sector to form together an annular or substantially annular structure centred on the longitudinal central axis (2) of the ferrule.

3. Ferrule according to claim 1 or claim 2, characterised in that it comprises a non-friction cladding (76) covering the upstream and downstream groove walls (52, 58), inside the groove (48), the non-friction cladding (76) preferentially being a fabric or a foil.

4. Ferrule according to any one of the preceding claims, characterised in that it also comprises a third fibrous preform (80) or a group of third fibrous preforms (80), each third fibrous preform being obtained by three-dimensional weaving of threads and densified by a matrix, the third preform (80) or the group of third preforms defining a base (82) internally attached to the barrel (45) defined by the first preform (64), as well as a structural gasket span (60) projecting axially downstream beyond the downstream groove wall (58).

5. Ferrule according to claim 4, characterised in that the third preform (80) or each preform of the group of third preforms is loosened on weaving so as also to define an additional base (84) externally attached to the downstream groove wall (58).

6. Aircraft turbine engine (1), comprising an exterior intermediate-casing ferrule (23) according to any one of the preceding claims.

7. Method for manufacturing an exterior ferrule (23) of an intermediate casing (21) for an aircraft turbine engine, the ferrule made from composite material comprising an annular connecting downstream end (46) forming a peripheral groove (48) radially open towards the outside, said groove (48) being intended to receive a complementary connecting member (50) provided on one or more nacelle cowls (38), and this groove being axially delimited by an upstream groove wall (52), as well as by a downstream groove wall (58), the method including the following steps: - producing a first fibrous preform (64) by three-dimensional weaving of threads, the first preform being intended to define a barrel (45) of the ferrule and a structural part (66) of the downstream groove wall (58), projecting radially outwards with respect to the barrel; - producing a second fibrous preform (68) or a group of second fibrous preforms, each second fibrous preform (68) being obtained by three-dimensional weaving of threads, the second preform or the group of second preforms being intended to define a base (70) as well as a structural part (72) of the upstream groove wall (52), projecting radially outwards with respect to the barrel; - injecting and polymerising a matrix for densifying the first preform (64); and - injecting and polymerising a matrix for densifying the second preform (68) or the group of second preforms, so that the base (70) is fixedly and externally attached to the barrel (45) of the ferrule.

8. Method according to claim 7, characterised in that the injection of a matrix for densifying the first preform (64) takes place at the same time as the injection of a matrix for densifying the second preform (68) or group of second preforms, by matrix co-injection preferably in a flexible-injection tool, in a rigid-mould matrix transfer tool, or in a hybrid flexible-injection and rigid-mould matrix transfer tool (90).

9. Method according to claim 7, characterised in that first of all the injection and polymerisation of a matrix for densifying the first preform (64) is proceeded with, preferably in a rigid-mould matrix transfer tool, then next, during a subsequent curing step, the injection and polymerisation of a matrix for densifying the second preform (68) or of the group of second preforms is proceeded with, preferably in a rigid-mould matrix transfer tool.

10. Method according to any one of claims 7 to 9, characterised in that it comprises the production of a non-friction cladding (76) covering the upstream and downstream groove walls (52, 58), inside the groove (48), the non-friction cladding (76) preferably being produced by co-curing during the curing of the first preform (64) and of the second preform (68) or of the group of second preforms, or bonded to the upstream and downstream groove walls (52, 58) after said curing.

11. Method according to any one of claims 7 to 10, characterised in that it also comprises: - the production of a third fibrous preform (80) or a group of third fibrous preforms, each third preform (80) being obtained by three-dimensional weaving of threads, the third preform or the group of third preforms being intended to define a base (82) as well as a structural gasket span (60) projecting axially downstream beyond the downstream groove wall; and - injection and polymerisation of a matrix for densifying the third preform (80) or of the group a third preforms, so that the base (82) is fixedly and internally attached to the barrel (45) of the ferrule.