Fibrous texture for a rotating part made of a composite material with increased torsional stiffness
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- SAFRAN AIRCRAFT ENGINES SAS
- Filing Date
- 2026-01-27
- Publication Date
- 2026-08-06
Smart Images
Figure FR2026050079_06082026_PF_FP_ABST
Abstract
Description
[0001] Description
[0002] Title of the invention: Fibrous texture for a part of revolution made of a composite material with increased torsional stiffness
[0003] Technical Field
[0004] The invention relates to the composite material parts of revolution of gas turbines, and more particularly, but not exclusively, to the fan casings of gas turbines for aeronautical engines and the external shells of the intermediate casing present downstream of a fan casing of a turbofan engine.
[0005] Previous technique
[0006] A turbofan engine includes a fan, typically located at the front of the engine. This fan delivers an airflow split into a primary flow and a secondary flow surrounding the primary flow. The primary flow is directed to a compressor, a combustion chamber, and a turbine driving both the compressor and the fan. It is then expelled, along with the exhaust gases, through an exhaust nozzle to produce reaction thrust. The secondary flow is straightened downstream of the fan and expelled in roughly the same direction. Thus, the majority of the thrust is due to the secondary flow of fresh air driven by the fan, with a smaller portion coming from the primary flow containing the hot exhaust gases.
[0007] The "bypass ratio" refers to the ratio between the mass flow rates of the secondary and primary streams. Except at very high speeds, particularly supersonic speeds, the propulsive efficiency of a turbofan engine increases with this bypass ratio. Increasing the bypass ratio is therefore a promising way to reduce the energy consumption of turbofan engines, and consequently lower both operating costs and emissions of pollutants and greenhouse gases. A high bypass ratio also offers additional advantages, such as reduced noise.
[0008] However, to increase the dilution ratio, it is normally necessary to also increase the diameter of the fan. This presents several drawbacks, including an increase in the mass and drag of the casing and nacelle surrounding the fan blades.
[0009] Existing turbofan engines of twin-flow design generally have a fan casing extended downstream by an intermediate casing which includes an external shell known as the "intermediate casing shell" or "VCI".
[0010] Previously made of metallic material, blower housings are now made of composite material, that is to say from a fibrous preform densified by an organic matrix, which makes it possible to make parts with a lower overall mass than the same parts when made of metallic material while having at least equivalent if not superior mechanical resistance.
[0011] The manufacture of a blower housing in organic matrix composite material is described in particular in US document 8,322,971, the blower housing being formed from a fibrous reinforcement obtained by winding a 3D woven fibrous texture densified by an organic matrix.
[0012] It may be possible to also manufacture the outer shell of the intermediate housing from composite material in order to further lighten the entire blower assembly.
[0013] However, to achieve a significant weight reduction, the housing and ferrule must be relatively thin. This makes the housing and ferrule sensitive to vibration, which can be problematic for dynamic behavior.
[0014] Prior art solutions exist to prevent the development of undesirable modes in composite housings. One such solution, disclosed in US patent application 2014 / 212273, involves equipping the composite housing with added stiffeners. However, this solution significantly increases the overall mass of the housing, particularly for large-diameter blower housings. Furthermore, it is complex to implement, especially regarding the attachment of the stiffeners, which must be as reliable as possible.
[0015] Another solution, disclosed in US patent 2017 / 266893, involves stiffening a composite blower housing by incorporating an omega-shaped section. However, this solution results in a significant increase in the housing's size and weight. Furthermore, due to its complex omega geometry, manufacturing and installing equipment (e.g., acoustic panels, abradable cartridges) on this type of housing is cumbersome. Finally, the cavity formed by the omega section must be filled with a material, further increasing the housing's overall weight.
[0016] Thus, there is a need to improve the resistance of a part of revolution made of composite material to vibrational stresses without significantly increasing the mass and / or size of the part.
[0017] Description of the invention
[0018] To this end, the invention proposes a fibrous texture for the fibrous reinforcement of a part of revolution made of composite material, having a band shape extending in a longitudinal direction over a determined length between a proximal end and a distal end, and in a transverse direction over a determined width between a first lateral edge and a second lateral edge. The fibrous texture has a three-dimensional weave between a plurality of layers of warp yarns extending in the longitudinal direction and a plurality of layers of weft yarns extending in the lateral direction. The fibrous texture is characterized in that it comprises a terminal portion extending along the longitudinal direction.over a determined length between an intermediate position present between the proximal and distal extremities and the distal extremity, and in that the portion comprises a plurality of debondings, each forming an internal housing in the fibrous texture, each debonding extending between the first and second lateral edges of the fibrous texture in a direction making an angle with the longitudinal direction of between ± 40° and ± 50°.
[0019] The fibrous texture according to the invention makes it possible to produce large-diameter parts of revolution with greater stiffness, thereby enhancing their natural modes to move frequency coincidences outside the operating range. The part of revolution consequently exhibits improved mode stability, which helps prevent the occurrence of undesirable vibration modes. Furthermore, the stiffening solution of the invention does not increase the mass of the housing.
[0020] The invention also relates to a fibrous preform of a part of revolution comprising a winding on several turns of a fibrous texture according to the invention, the internal housings formed by the debondings in the fibrous texture extending on the outer turn of the winding of the preform, stiffening elements being introduced into each of the internal housings so as to form preform parts of stiffening portion.
[0021] The fibrous preform of the invention can advantageously serve as a fibrous reinforcement for an external intermediate housing (ICH) ferrule. Indeed, an IHC is subjected to significant torsional stress. The integration of stiffeners oriented between ±40° and ±50° significantly increases the mechanical strength of the IHC.
[0022] According to a particular feature of the preform of the invention, the stiffening elements correspond to fibrous reinforcement elements such as, in particular, unidirectional yarns, fibers, braids or textiles (sheets, strips, etc.) pre-consolidated or not.
[0023] The invention also relates to a gas turbine casing made of a composite material, comprising a fibrous reinforcement consisting of a fibrous preform according to the invention, and a matrix densifying the fibrous reinforcement. The casing can, in particular, be a gas turbine blower casing. The invention also relates to an intermediate casing shell made of a composite material, comprising a fibrous reinforcement consisting of a fibrous preform according to the invention, and a matrix densifying the fibrous reinforcement.
[0024] The invention also relates to an aeronautical gas turbine engine having an intermediate casing or casing ferrule according to the invention.
[0025] The invention also relates to a method for manufacturing a fibrous texture by three-dimensional weaving between a plurality of layers of warp strands extending in a longitudinal direction and a plurality of layers of weft strands extending in a transverse direction, the fibrous structure having a band shape extending in the longitudinal direction over a determined length between a proximal end and a distal end and in the transverse direction over a determined width between a first lateral edge and a second lateral edge, characterized in that the method comprises creating in a terminal portion of the fibrous texture extending, along the longitudinal direction, over a determined length between an intermediate position present between the proximal and distal ends and the distal end, a plurality of unlinks each forming an internal housing in the fibrous texture,each debonding extending between the first and second lateral edges of the fibrous texture along a direction making an angle with the longitudinal direction of between ± 40° and ± 50°.
[0026] The invention also relates to a method for manufacturing a fibrous preform for a part of revolution comprising:
[0027] - the manufacture of a fibrous texture according to the process of the invention,
[0028] - the winding of the fibrous texture over several turns on a shaping tool, the terminal portion of the fibrous texture forming the last turn of the winding,
[0029] - the insertion of stiffening elements in each of the internal housings present in the terminal portion of the fibrous texture.
[0030] The invention also relates to a method for manufacturing an aeronautical casing or an external shell of an intermediate casing comprising the manufacture of a fibrous preform according to the method of the invention and the densification of the preform by a matrix.
[0031] Brief description of the drawings
[0032] [Fig. 1] Figure 1 is a schematic perspective view of a loom showing the three-dimensional weaving of a fibrous texture,
[0033] [Fig. 2] Figure 2 is a schematic perspective view of a fibrous texture according to one embodiment of the invention,
[0034] [Fig. 3] Figure 3 is a partial lateral section of the fibrous texture of Figure 2 and showing a weave pattern with unbinding,
[0035] [Fig. 4] Figure 4 is a schematic perspective view showing the beginning of the winding of the fibrous texture of Figure 2 on a forming tool, [Fig. 5] Figure 5 is a schematic perspective view showing the end of the winding of the fibrous texture of Figure 2 on a forming tool, [Fig. 6] Figure 6 is a partial lateral section of the fibrous texture shown in Figure 5 according to a weave pattern,
[0036] [Fig. 7] Figure 7 is a cross-sectional view showing the positioning of injection sectors on a crankcase preform,
[0037] [Fig. 8] Figure 8 is a perspective view of an aircraft engine according to one embodiment of the invention.
[0038] Description of the implementation methods
[0039] The invention applies generally to fibrous textures intended for the manufacture of housings made of composite material, these housings being subjected to mechanical stresses in torsion. The invention applies more particularly but not exclusively to the manufacture of blower housings or external ferrules known as "intermediate housing ferrules" or "VCI".
[0040] As shown in Figure 1, a fibrous texture 100 is produced in a known way by weaving using a jacquard type loom 5 on which a bundle of warp yarns or strands 20 has been arranged in a plurality of layers, the warp yarns being linked by weft yarns or strands 30.
[0041] The fibrous texture is achieved through three-dimensional weaving. "Three-dimensional weaving" or "3D weaving" refers to a weaving method in which at least some of the weft yarns interlock with warp yarns across multiple layers of warp yarns, or vice versa. The fibrous texture may exhibit an interlock weave. "Interlock" weaving refers to a weave structure in which each layer of weft yarns interlocks with multiple layers of warp yarns, with all yarns in the same weft column moving in the same direction within the plane of the weave. Other weave structures are also possible.
[0042] The fibers of the main fibrous texture 100 may be carbon, ceramic, glass, or aramid fibers, or a mixture of such fibers. In particular, the main fibrous texture 100 may be made from fibers composed of the following materials: silicon carbide, alumina, mullite, silica, an aluminosilicate, a borosilicate, or a mixture of several of these materials. According to a preferred embodiment of the invention, the fibers of the main fibrous texture 100 are made of carbon or glass.
[0043] As illustrated in Figure 2, the fibrous texture 100 has a band shape which extends lengthwise in a longitudinal direction DL corresponding to the direction of the warp yarns or strands 20 and widthwise or transversely in a transverse direction DT between a first and a second lateral edges 101 and 102, the transverse direction DT corresponding to the direction of the weft yarns or strands 30. The fibrous texture extends longitudinally over a determined length Lioo in the longitudinal direction DL between a proximal end 103 intended to form the beginning of the winding of a fibrous preform on a forming tool and a distal end 104 intended to form the end of the winding of the fibrous preform.
[0044] The length Lioo of the fibrous texture 100 is determined based on the circumference of the tooling or shaping mold in order to allow a determined number of turns of the fibrous texture.
[0045] In the example described here, the fibrous texture 100 has a length Lioo, allowing for four windings on the forming tooling. To this end, the fibrous texture 100 comprises, along its longitudinal direction, four segments Ti to T with lengths LTI to LT4, corresponding respectively to the first, second, third, and fourth windings of the fibrous texture on the forming tooling. The length LT2 is slightly greater than the length LTI, the length LT3 is slightly greater than the length LT2, and the length LT4 is slightly greater than the length LT3 to account for the increasing radius as the fibrous texture is wound.
[0046] The fourth portion T4, referred to as the "terminal portion," of the fibrous texture 100 is intended to form the last or outermost turn of the winding on the forming tooling. According to the invention, during the weaving of the fibrous texture 100, unbindings 160, 161, 162, 163, 164, and 165 are formed in the terminal portion T4. The unbindings 160, 161, 162, 163, 164, and 165 extend along a direction forming an angle with the longitudinal direction DL of between ±40° and ±50°, and preferably an angle of ±45°.In the example described here, the disjunctions 161, 163, 165 extend between the first and second lateral edges 101, 102 along a first direction Di forming an angle with the longitudinal direction DL between 40° and 50°, and preferably an angle of 45°, while the disjunctions 160, 162, 164 extend between the first and second lateral edges 101, 102 along a second direction D2 forming an angle with the longitudinal direction DL between - 40° and - 50°, and preferably an angle of - 45°.The disjunctions 161, 163 and 165 respectively form internal housings 170, 173 and 175 which extend along the first direction Di forming an angle with the longitudinal direction DL between 40° and 50°, and preferably an angle of 45°, while the disjunctions 160, 162 and 164 respectively form internal housings 170, 172 and 174 which extend along the second direction D2 forming an angle with the longitudinal direction DL between -40° and -50°, and preferably an angle of -45°. Each of the connections 160, 162, 163, 164 and 165 opens onto the lateral edges 101 and 102. The internal housings 170, 172, 173, 174 and 175 are each accessible from the lateral edges 101 and 102.
[0047] Figure 3 illustrates a portion of the fibrous texture comprising the debonding 161. The debonding 161 extends along a plane parallel to the surface of the fibrous blank and locally separates the terminal portion T4 into two woven sections. The debonding 160 extends along the first direction Di, forming an angle with the longitudinal direction DL of between 40° and 50°, and preferably an angle of 45°, over a determined length between the first and second lateral edges 101, 102, at which it emerges. The debonding 161 thus forms the internal recess 171 in the fourth section T4 of the fibrous texture 100, which is accessible via the lateral edges 101 and 102.
[0048] A 3D interlock weave pattern of blank 100 is schematically shown in Figure 3. Figure 3 is a partial enlarged view of a warp cross-section in the fourth portion T4 of blank 100, which includes the unlinking zone 161 (section III-III in Figure 2). In this example, blank 100 comprises 8 layers of warp yarns 20 extending substantially in the longitudinal direction DL. In Figure 3, the 8 warp yarn layers are linked by weft yarns ti to ts in the linking zones, with the weft yarns extending substantially in the lateral direction DT. At the level of the unlinking 161, the upper woven portion comprises 4 layers of warp yarns 20 linked together by 4 weft yarns ti to t4 while the lower woven portion comprises the 4 layers of warp yarns 20 linked together by 4 weft yarns ts to ts.
[0049] In other words, the fact that the weft yarns ti to t4 do not extend into the warp yarn layers of the lower woven portion and that the weft yarns ts to tsne do not extend into the warp yarn layers of the upper woven portion ensures the unbinding 161 which separates the lower and upper woven portions of the fibrous texture.
[0050] In the weaving example shown in Figure 3, the weft yarns ti to , on the one hand, and the weft yarns ts to ts, on the other hand, are respectively arranged on each side of the unbinding 161, the weft yarns ti to linking the first four layers of warp yarns forming the upper woven portion and the weft yarns ts to ts linking the last four layers of warp yarns forming the lower woven portion.
[0051] According to one embodiment, a first set of weft yarns can cross a second set of weft yarns upstream and downstream of the unbinding 161 along the lateral direction DT. The yarns of the first set of weft yarns extend on one side of the unbinding 161 along the lateral direction, while the yarns of the second set of yarns from the plurality of weft yarn layers extend on the other side of the unbinding along the lateral direction. The crossing of the first and second sets of weft yarns upstream and downstream of the unbinding 160 along the lateral direction DT improves the fibrous texture retention in the unbinding zone.
[0052] The fibrous texture 100 of the invention, after shaping, allows for the formation of a fibrous housing reinforcement in which stiffening portions are present in a structural zone of the housing, the stiffening portions being formed with internal recesses 170 to 175 as explained below. This increases the torsional stiffness of the housing.
[0053] We have just described an example in which the fibrous texture has an interlock weave with 8 warp layers and 8 weft layers. However, we do not depart from the scope of the invention when the number of warp and weft layers is different, or when the fibrous texture has a weave other than an interlock weave.
[0054] As illustrated in Figure 4, the production of a fibrous preform intended to form the fibrous reinforcement of the housing begins by winding the fibrous texture 100 described previously onto a mandrel 50. The fibrous reinforcement constitutes a complete tubular fibrous preform of a one-piece housing. To this end, the mandrel 50 has an external surface 51 whose profile corresponds to the internal surface of the housing to be produced. The mandrel 50 also includes two flanges 52 and 53 to form preform portions of the upstream and downstream flanges 63 and 66 corresponding to the flanges of the housing.
[0055] The fibrous texture 100 is wound onto the mandrel 50 from its proximal end 103. One or more turns of winding are made until the terminal portion T4 of the texture is reached, which includes the internal recesses 170, 171, 172, 173, 174, and 175, as illustrated in Figure 5. In the example described here, portions T1, T2, and T3 of the fibrous texture 100 are wound onto the mandrel 50 first, and then the winding is stopped to allow the introduction of stiffening elements into the internal recesses 170 to 175. Each internal recess 170, respectively 171, 172, 173, 174, and 175, is accessible from the first lateral edge 101 of the fibrous texture 100 via an opening 170a, respectively 171a, 172a, 173a, 174a and 175a or from the second lateral edge 102 of the fibrous texture 100 via an opening 170b, respectively 171d, 172b, 173b, 174b and 175b.
[0056] In the example described here, the stiffening elements correspond to pre-consolidated fibers 150 extending into each of the internal spaces 170 to 175, as illustrated in Figure 6 for internal space 171. Generally, the stiffening elements arranged in each of the internal spaces consist of fibrous reinforcing elements, which may be, but are not limited to, pre-consolidated or non-pre-consolidated unidirectional yarns, fibers, braids, or webs or strips of textiles. The pre-consolidation of the yarns, fibers, braids, or unidirectional textiles can be carried out using a known method, either liquid (impregnation of the fibrous elements with a liquid matrix precursor and transformation of the precursor into a matrix) or gaseous (chemical infiltration via gas or CVI).
[0057] Once the stiffening elements are inserted into the internal recesses and the fibrous texture is fully wound, a fibrous preform 60 is obtained, as illustrated in Figure 7. This preform will constitute the fibrous reinforcement of the composite housing. The preform 60 comprises preform portions of the stiffening section formed by the internal recesses 170 to 175, in which stiffening elements are present (not shown in Figure 7). These preform portions of the stiffening section are located on the outer periphery of the preform 60 (not shown in Figure 7).
[0058] The next step is to densify the fibrous preform 60 using a matrix. Densification of the fibrous preform consists of filling the porosity of the preform, in all or part of its volume, with the material constituting the matrix.
[0059] The matrix can be obtained in a manner known per se via the liquid process. The liquid process consists of impregnating the preform with a liquid composition containing an organic precursor of the matrix material. The organic precursor is usually in the form of a polymer, such as a resin, possibly diluted in a solvent. The fibrous preform is placed in a mold that can be sealed tightly with a cavity having the shape of the final molded part. As illustrated in Figure 7, the fibrous preform 60 is placed between a plurality of sectors 54 forming a counter-mold and the mandrel 50 forming a support, these elements having respectively the external and internal shapes of the housing to be produced. Then, the liquid matrix precursor, for example a resin, is injected throughout the cavity to impregnate the preform.
[0060] The transformation of the precursor into an organic matrix, namely its polymerization, is achieved through heat treatment, generally by heating the mold after removing any solvent and crosslinking the polymer. The preform remains in the mold, which has a shape corresponding to that of the part to be produced. The organic matrix can be obtained from epoxy resins, such as high-performance epoxy resins, or from liquid precursors of carbon or ceramic matrices. In the case of forming a carbon matrix, the heat treatment involves pyrolyzing the organic precursor to transform it into a carbon matrix. For example, 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.
[0061] The densification of the fibrous preform can be achieved using the well-known resin transfer molding (RTM) process. According to the RTM process, the fibrous preform is placed in a mold shaped like the housing to be produced. A thermosetting resin is injected into the internal space between the rigid material part and the mold, a space that includes the fibrous preform. A pressure gradient is generally established within this internal space between the resin injection point and the resin discharge ports to control and optimize the resin impregnation of the preform.
[0062] The resin used can be, for example, an epoxy resin. 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 will be subjected. Once the resin has been injected throughout the reinforcement, it is cured by heat treatment according to the RTM process.
[0063] After injection and polymerization, the part is demolded. The part is then trimmed to remove excess resin, and the chamfers are machined to obtain a housing 810 with a shape of revolution as illustrated in Figure 8. The housing 810 comprises an upstream flange 811, a barrel 813, and a downstream flange 814.
[0064] According to the invention, the housing further comprises stiffeners 815 formed by preform portions of the stiffening section. The stiffeners 815 extend alternately along the first direction DI, forming an angle with the longitudinal direction DL of between 40° and 50°, and preferably an angle of 45°, and along the second direction D2, forming an angle with the longitudinal direction DL of between -40° and -50°, and preferably an angle of -45°. The stiffeners 815 are preferably, but not exclusively, distributed homogeneously over the entire external periphery of the housing 810.
[0065] The number of stiffeners formed in the casing is determined according to the level of torsional stiffening that one wishes to impart to the casing.
[0066] The casing 810 shown in Figure 8 is a casing for a fan of a gas turbine aircraft engine 80. Such an engine, as schematically shown in Figure 8, comprises, from upstream to downstream in the direction of the gas flow, a fan 81 located at the engine inlet, a compressor 82, a combustion chamber 83, a high-pressure turbine 84, and a low-pressure turbine 85. The engine is housed within a casing comprising several parts corresponding to different engine components. Thus, the fan 81 is surrounded by the casing 810.
[0067] In one variation, the stiffening elements are inserted into the internal spaces of the fibrous texture before winding begins. In this case, winding can be completed entirely without interruption.
Claims
Demands
1. Fibrous texture (100) for fibrous reinforcement of a part of revolution made of composite material having a band shape extending in a longitudinal direction (DL) over a determined length (Lioo) between a proximal end (103) and a distal end (104) and in a transverse direction (DT) over a determined width between a first lateral edge (101) and a second lateral edge (102), the fibrous texture having a three-dimensional weave between a plurality of layers of warp yarns (20) extending in the longitudinal direction and a plurality of layers of weft yarns (30) extending in the lateral direction, characterized in that the fibrous texture (100) comprises a terminal portion 0" extending, along the longitudinal direction, over a determined length (L™) between an intermediate position present between the proximal and distal ends (103, 104) and the distal end (104) and in that the portion comprises a plurality of unlinkages (160, 161, 162, 163, 164, 165) each forming an internal housing (170, 171, 172, 173, 174, 175) in the fibrous texture, each unlinkage extending between the first and second lateral edges (101, 102) of the fibrous texture along a direction making an angle with the longitudinal direction (DL) between ± 40° and ± 50°.
2. A fibrous preform (60) of a part of revolution comprising a multi-turn winding of a fibrous texture (100) according to claim 1, the internal recesses (170, 171, 172, 173, 174, 175) formed by the unbindings (160, 161, 162, 163, 164, 165) in the fibrous texture (100) extending over the outer turn of the preform winding, stiffening elements being introduced into each of the internal recesses so as to form preform portions of stiffening portion.
3. A fibrous preform according to claim 2, wherein the stiffening elements correspond to pre-consolidated or unconsolidated fibrous reinforcing elements (150).
4. Gas turbine housing (810) of a composite material, comprising a fibrous reinforcement consisting of a fibrous preform (60) according to claim 2 or 3, and a matrix densifying the fibrous reinforcement.
5. Carter (810) according to claim 4, wherein said housing is a gas turbine blower housing.
6. External intermediate housing ferrule made of composite material comprising a fibrous reinforcement consisting of a fibrous preform (60) according to claim 2 or 3, and a matrix densifying the fibrous reinforcement.
7. Aeronautical gas turbine engine (80) having a casing (810) according to claim 4 or 5 or an external intermediate casing ferrule according to claim 6.
8. Method of manufacturing a fibrous texture (100) by three-dimensional weaving between a plurality of layers of warp yarns (20) extending in a longitudinal direction (DL) and a plurality of layers of weft yarns (30) extending in a transverse direction (DT), the fibrous structure having a band shape extending in the longitudinal direction (DL) over a determined length (100) between a proximal end (103) and a distal end (104) and in the transverse direction (DT) over a determined width between a first lateral edge (101) and a second lateral edge (102), characterized in that the process comprises the creation in a terminal portion 0" of the fibrous texture extending, along the longitudinal direction, over a determined length (L™) between an intermediate position present between the proximal and distal ends (103, 104) and the distal end (104) of a plurality of debondings (160, 161, 162, 163, 164, 165) each forming an internal housing (170, 171, 172, 173, 174, 175) in the fibrous texture, each debonding extending between the first and second lateral edges (101, 102) of the fibrous texture along a direction making an angle with the longitudinal direction of between ± 40° and ± 50°.
9. A method for manufacturing a fibrous preform (60) of a part of revolution (810) comprising: - the manufacture of a fibrous texture (100) according to the process as defined in claim 8, - the winding of the fibrous texture (100) over several turns on a shaping tool (50), the terminal portion of the fibrous texture forming the last turn of the winding, - the insertion of stiffening elements in each of the internal housings present in the terminal portion of the fibrous texture.
10. Method according to claim 9, wherein the stiffening elements correspond to pre-consolidated or non-pre-consolidated fibrous reinforcing elements (150).
11. Method of manufacturing an aeronautical casing (810) comprising manufacturing a fibrous preform (60) according to the method as defined in claim 9 or 10 and densifying the preform by a matrix.
12. Method of manufacturing an external intermediate housing shell comprising manufacturing a fibrous preform (60) according to the method as defined in claim 9 or 10 and densifying the preform by a matrix.