INTERMEDIATE CASING FOR AN AIRCRAFT TURBOMACHINE AND ASSOCIATED MANUFACTURING METHOD

Abstract

The invention relates to an annular intermediate casing (12) for an aircraft turbomachine (1), the intermediate casing (12) having an axis of revolution (X) and comprising: - an annular inner shell (13) centered on the axis of revolution (X), - an annular outer shell (14) arranged coaxially around the inner shell (13), and - radial arms (15) connecting the inner and outer shells (13, 14), the intermediate casing (12) being characterized in that the outer shell (14) comprises: - an annular inner panel (18) centered on the axis of revolution (X) and extending around the arms (15), - an annular outer panel (19) arranged coaxially around the inner panel (18), and - an annular core (20) arranged coaxially between the inner and outer panels (18, 19). Abstract figure: Figure 4

Description

Title of the invention: INTERMEDIATE CASING FOR AN AIRCRAFT TURBOMACHINE AND ASSOCIATED MANUFACTURING METHOD Technical field of the invention

[0001] The invention relates to the field of intermediate casings for aircraft turbomachines.

[0002] The invention also relates to the field of manufacturing these intermediate casings. Technical background

[0003] An aircraft turbomachine typically has a longitudinal axis. It comprises, for example, from upstream to downstream in the direction of gas flow along the longitudinal axis, a fan, a low-pressure compressor, a high-pressure compressor, a combustion chamber, a high-pressure turbine, a low-pressure turbine and a gas exhaust nozzle.

[0004] The blower allows the suction of an air flow dividing into a primary flow and a secondary flow. The primary flow passes through a primary vein of the turbomachine while the secondary flow is directed towards a secondary vein surrounding the primary vein.

[0005] The primary flow is compressed within the compressors. The compressed air is then mixed with a fuel and burned within the combustion chamber. The gases resulting from the combustion pass through the turbines and then escape through the nozzle, the cross-section of which allows the acceleration of these gases to generate propulsion.

[0006] The fan typically comprises a movable disc rotating about the longitudinal axis and blades mounted on the disc. The blades are surrounded by a fan casing centered on the longitudinal axis and intended to retain the blades in the event of damage, for example, to the blades.

[0007] The fan casing is typically surrounded by a nacelle which protects the fan. Such a fan is called ducted as opposed to unducted fans whose blades are not surrounded by a casing.

[0008] The turbomachine further comprises an intermediate casing located downstream of the fan casing. The intermediate casing typically comprises an annular inner shroud centered on the longitudinal axis and an annular outer shroud arranged coaxially around the inner shroud. The outer shroud defines with the inner shroud a portion of the secondary flow path v2. The intermediate casing further comprises radial arms connecting the inner and outer shrouds. The radial arms are typically connected to the outer shroud by platforms arranged radially between the arms and a portion downstream annular portion of the outer shell. The outer shell further comprises an upstream annular portion axially connected to the fan casing.

[0009] Turbomachines are a significant source of noise pollution and there is a strong demand to reduce this type of pollution. To this end, it has been proposed to equip the outer shell of the intermediate casing with acoustic panels in order to reduce the noise generated by turbomachines.

[0010] An acoustic panel typically comprises a sandwich structure comprising internal and external panels, and between which is arranged a core having for example a honeycomb structure intended to absorb sound waves. The internal panel also has holes allowing the sound waves to propagate in the core through which they are absorbed.

[0011] Such an acoustic panel is typically manufactured in the form of angular sectors which are each attached and fixed to the upstream part of the external shell. The acoustic panels are secured to the external shell of the intermediate casing by rivet-type fixing elements.

[0012] Although significantly reducing the noise pollution generated by the turbomachine, this type of acoustic panel is not entirely satisfactory. Indeed, the fixing means tend to reduce the acoustic performance since they are permeable to acoustic waves. Furthermore, these fixing means considerably increase the mass of the intermediate casing. Also, the presence of the platforms prevents the arrangement of the acoustic panels in the downstream annular part of the outer shell, further reducing the acoustic performance of the outer shell. Finally, the manufacture of such acoustic panels and their installation in the intermediate casing are long and tedious operations and consequently expensive.

[0013] There is therefore a need to provide an intermediate casing for an aircraft turbomachine which has good acoustic insulation performance while being light, easy to manufacture and inexpensive. Summary of the invention

[0014] To this end, the invention proposes an annular intermediate casing for an aircraft turbomachine, the intermediate casing having an axis of revolution and comprising:

[0015] - an annular internal shell centered on the axis of revolution,

[0016] - an annular outer ferrule arranged coaxially around the inner ferrule, and

[0017] - radial arms connecting the inner and outer ferrules,

[0018] the intermediate casing being remarkable in that the external shell comprises:

[0019] - an annular internal panel centered on the axis of revolution and extending around the arm,

[0020] - an annular outer panel arranged coaxially around the inner panel, and

[0021] - an annular core arranged coaxially between the internal and external panels.

[0022] According to the invention, the outer shell of the intermediate casing comprises inner and outer panels between which the core is arranged. Thus, the outer shell of the intermediate casing directly integrates the acoustic insulation properties.

[0023] Thanks to the invention, it is possible to do without sectors of acoustic panels and the fixing elements of these panels and therefore to simplify the manufacturing and assembly process of these panels. The intermediate casing is therefore lighter and less expensive.

[0024] Thanks to the invention, the acoustic properties of the intermediate casing are also considerably improved.

[0025] The invention may comprise one or more of the following features, taken in isolation from one another or in combination with one another:

[0026] - the external ferrule comprises an upstream annular part and a downstream annular part located around the arms, the core being located at least in the upstream annular part;

[0027] - the core is located in both the upstream and downstream annular parts;

[0028] - the internal panel comprises a first polymeric matrix and fibers of reinforcement embedded in the first matrix;

[0029] - the outer panel comprises a second polymeric matrix and fibers of reinforcement embedded in the second matrix;

[0030] - the polymers of the first and / or second matrices are chosen from thermo plastics or thermosets;

[0031] - the internal panel has holes.

[0032] The invention also relates to a method of manufacturing an annular intermediate casing according to any one of the preceding characteristics, the method being remarkable in that it comprises a step (c) of producing the external shell, step (c) comprising the following chronological sub-steps:

[0033] (cl) forming an annular internal panel centered on an axis of revolution,

[0034] (c2) depositing coaxially around the internal panel, an annular core,

[0035] (c3) forming an external panel coaxially around the core, and

[0036] (c4) optionally, heat treat the internal and external panels.

[0037] The method may comprise one or more of the following features, taken in isolation from each other or in combination with each other:

[0038] - sub-steps (cl) and / or (c3) are carried out by a placement method at fiber automation.

[0039] - after sub-step (c4), a step (c5) of drilling the internal panel. Brief description of the figures

[0040] Other characteristics and advantages will emerge from the following description of non-limiting embodiments of the invention with reference to the appended drawings in which:

[0041] [Fig.l] is a schematic representation in longitudinal section of a half aircraft turbomachine,

[0042] [Fig.2] is a schematic perspective representation of an intermediate casing according to the invention,

[0043] [Fig. 3] is a schematic representation of the external shell equipping the intermediate casing according to the invention,

[0044] [Fig.4] is a schematic representation in longitudinal section of the intermediate casing according to one embodiment of the invention,

[0045] [Fig.5] is a schematic representation in longitudinal section of the intermediate casing according to another embodiment of the invention,

[0046] [Fig.6] is a block diagram of a manufacturing method according to the invention,

[0047] [Fig.7] is a schematic representation of an installation for manufacturing the external shell,

[0048] [Fig.8] is a schematic representation of a manufacturing station for the internal and external panels of the external shell. Detailed description of the invention

[0049] An example of a turbomachine 1 for an aircraft is shown in [Fig.l]. The turbomachine 1 extends around and along a longitudinal axis X.

[0050] In the present application, the terms “upstream” and “downstream” are defined in relation to the direction of circulation of the gases in the turbomachine 1 along the longitudinal axis X.

[0051] The terms “axial”, “axially”, “radial”, “radially” are defined with respect to the longitudinal axis X.

[0052] The terms "internal", "interior", "internally", "external", "exterior", "externally", are defined with respect to the distance from the longitudinal axis X along an axis Z perpendicular to the longitudinal axis X.

[0053] The turbomachine 1 is preferably a turbojet, for example a twin-spool, twin-flow turbojet. It comprises, from upstream to downstream, a fan 2, at least one compressor such as a low-pressure compressor 3 and a high-pressure compressor 4, a combustion chamber 5, at least one turbine such as a high-pressure turbine 6 and a low-pressure turbine 7, and a gas exhaust nozzle.

[0054] The low and high pressure compressors 3, 4 and the high and low pressure turbines 6, 7 each comprise at least one rotor. The rotor of the low pressure compressor 3 is connected to the rotor of the low pressure turbine 7 by a low pressure shaft 8 and the rotor of the high pressure compressor 4 is connected to the rotor of the high pressure turbine 6 by a high pressure shaft 9. The high pressure shaft 9 is arranged coaxially around the low pressure shaft 8. The low and high pressure shafts 8, 9 are centered on the longitudinal axis X.

[0055] The fan 2 comprises a disk movable in rotation about the longitudinal axis X and blades 10 extending radially from the disk. The fan 2 further comprises a fan shaft (not shown) connected to the low pressure shaft 8 via a speed reducer for example.

[0056] The blower 2 allows the suction of an air flow F dividing into a primary air flow Fl and a secondary air flow F2. The primary air flow Fl passes through a primary vein vl of the turbomachine 1 and the secondary flow F2 flows into a secondary vein v2 of the turbomachine 1. The secondary vein v2 surrounds the primary vein vl.

[0057] The primary flow F1 is compressed within the low pressure compressor 3 then the high pressure compressor 4. The compressed air is then mixed with a fuel and burned within the combustion chamber 5. The gases formed by the combustion pass through the high pressure and low pressure turbines 6, 7. The gases finally escape through the nozzle, the cross-section of which allows the acceleration of these gases to generate propulsion.

[0058] The fan 2 is of the ducted type. The turbomachine 1 thus further comprises a fan casing 11. The fan casing 11 is annular and centered on the longitudinal axis X. It is arranged around the blades 10. The fan casing 11 forms a portion of the secondary vein v2.

[0059] The turbomachine 1 further comprises an intermediate casing 12. The intermediate casing 12 is arranged downstream of the fan casing 11.

[0060] With reference to [Fig.2], the intermediate casing 12 has an axis of revolution which coincides with the longitudinal axis X of the turbomachine 1 when the intermediate casing 12 is mounted in the turbomachine 1. The intermediate casing 12 comprises an internal shell 13 and an external shell 14 connected by arms 15.

[0061] The internal ferrule 13 is annular and centered on the longitudinal axis X. The internal ferrule 13 is for example metallic. It externally delimits a portion of the primary vein vl.

[0062] The outer ferrule 14 is annular and centered on the longitudinal axis X. It is arranged coaxially around the inner ferrule 13. The outer ferrule 14 delimits with the inner ferrule 13 a portion of the secondary vein v2.

[0063] The outer ferrule 14 has a thickness e as measured along the radial axis Z of between 10 mm and 50 mm.

[0064] The outer ferrule 14 comprises an upstream annular part 16 and a downstream annular part 17. Preferably, the downstream annular part 17 is located around the arms 15. The upstream annular part 16 is axially connected to the fan casing 11.

[0065] In order to reduce the noise pollution generated by the turbomachine 1, the external shell 14 incorporates acoustic insulation properties. The external shell 14 is advantageously capable of absorbing acoustic energy over a frequency range between 100 Hz and 1500 Hz.

[0066] The outer shell 14 has a sandwich structure. According to the invention, and with reference to [Fig. 3], the outer shell 14 comprises an annular inner panel 18, an annular outer panel 19 and an annular core 20 advantageously having a honeycomb structure 21. The outer shell 14 advantageously forms a monolithic part.

[0067] The inner panel 18 is centered on the longitudinal axis X. It extends around the arms 15. The inner panel 18 is the innermost layer of the outer shell 14. The inner panel 18 comprises a first composite material comprising a first polymer matrix and reinforcing fibers embedded in the first matrix.

[0068] The polymeric material of the first matrix is ​​for example chosen from thermoplastics such as polyolefins, for example polyethylene, polypropylene or thermosets such as epoxies or thermosets such as epoxies or polybismaleimides.

[0069] The reinforcing fibers are for example chosen from carbon, glass, or polyamide fibers.

[0070] The carbon fibers are, for example, polyaryletherketone (PAEK) fibers such as polyetherketone (PEK), polyetheretherketone (PEEK) or polyetherketoneketone (or PEKK) or polyacrylonitrile (PAN) fibers such as HexTow® AS4, AS7 or IM7 fibers marketed by the company Hexcel.

[0071] Advantageously, the fibers are continuous fibers, that is to say strands made up of sets of continuous parallel or twisted filaments.

[0072] Advantageously, the fibers are high strength and / or intermediate modulus fibers, for example a modulus of between 200 GPa and 250 GPa or high modulus, for example a modulus of up to 350 GPa.

[0073] The internal panel 18 has holes 18a. The holes 18a are through holes. They thus pass through the internal panel 18 throughout its entire thickness. The holes 18a have, for example, a circular section. They have a diameter, for example, between 5 mm and 0.1 mm, less than 1 mm, and advantageously between 0.1 mm and 0.8 mm. Such a diameter of the holes 18a makes it possible to reduce the aerodynamic drag of the turbomachine 1. Indeed, the internal panel 18 is in contact with the secondary flow F2 and its presence disturbs the flow of the secondary flow F2. Such a disturbance generates aerodynamic drag reducing the performance of the turbomachine 1. The holes 18a are produced by laser drilling or by mechanical drilling.

[0074] The internal panel 18 has, for example, a thickness of between 0.5 mm and 2 mm, preferably between 0.8 mm and 2 mm.

[0075] The internal panel 18 is advantageously produced by automatic placement of fibers.

[0076] The outer panel 19 is arranged coaxially around the inner panel 18. The outer panel 19 is the outermost layer of the outer shell 14.

[0077] The outer panel 19 comprises a second composite material. The second composite material comprises a second polymer matrix and reinforcing fibers embedded in the second matrix.

[0078] The polymeric material of the second matrix is ​​chosen from thermoplastics or thermosets. The thermoplastic or thermoset material may be identical to or different from the thermoplastic or thermoset material of the first polymeric matrix. The thermoplastic of the second matrix is, for example, chosen from polyolefins such as polyethylene, polypropylene or fluorinated polymers or polyamides or polyaryletherketones such as polyetheretherketone (PEEK). According to another example, the thermoset of the second matrix is, for example, chosen from epoxies or polybismaleimides.

[0079] The reinforcing fibers are for example chosen from carbon, glass, and polyamide fibers.

[0080] The carbon fibers are, for example, polyaryletherketone (PAEK) fibers such as polyetherketone (PEK), polyetheretherketone (PEEK) or polyetherketoneketone (or PEKK) or polyacrylonitrile (PAN) fibers such as HexTow® AS4, AS7 or IM7 fibers marketed by the company Hexcel.

[0081] Advantageously, the fibers are continuous fibers, that is to say strands made up of sets of continuous parallel or twisted filaments.

[0082] Advantageously, the fibers are high strength and / or intermediate modulus fibers, for example a modulus of between 200 GPa and 250 GPa or high modulus, for example a modulus of up to 350 GPa.

[0083] The reinforcing fibers may be the same as or different from the reinforcing fibers of the internal panel 18.

[0084] The external panel 19 is advantageously produced by the automatic fiber placement method.

[0085] Advantageously, the external panel 19 has a thickness of between 1 mm and 20 mm, even more advantageously of between 1 mm and 15 mm. Advantageously, the internal and external panels 18, 19 have the same thickness.

[0086] The core 20 is annular and centered on the longitudinal axis X. It is arranged coaxially between the internal panel 18 and the external panel 19. The core 12 can have a structure, for example, a honeycomb 21 or a pattern with a rectangular, square or diamond-shaped cross-section. The core 20 comprises in particular honeycomb cells 21a. Each honeycomb cell 21a has, for example, a hexagonal or triangular, square or even diamond-shaped cross-section. The cross-section of the honeycomb cells 21a may differ from one honeycomb cell 21a to another. Each honeycomb cell 21a is hollow and has an internal cavity 21b which communicates with at least one hole 18a. This allows each honeycomb cell 21a to absorb part of the acoustic energy emitted by the turbomachine 1.

[0087] Advantageously, the core 20 comprises a radial superposition of alveolar cells 21a. The core 20 comprises, for example, a first layer of alveolar cells 21a and a second layer of alveolar cells (not shown). The first and second layers are separated by a septum. In the present technical field, a septum is a perforated membrane which is transparent to certain frequency ranges and impermeable to other frequency ranges. Such a configuration of the core 20 allows the outer shell 14 to absorb sound energy in a wider frequency range. Indeed, the first layer makes it possible to absorb sound energy in a first frequency range while the second layer makes it possible to absorb sound energy in another frequency range.

[0088] The core 20 comprises for example a metallic material such as aluminum or a polymeric material chosen for example from thermoplastics or composites.

[0089] The core 20 is advantageously produced by additive manufacturing directly on the internal panel 18 or the external panel 19. Thus, the manufacture of the external shell 14 according to the invention can be fully automated without a manual assembly step.

[0090] Alternatively, the core 20 is manufactured in parallel with the internal panel 18 and then deposited on the internal panel 18.

[0091] The core 20 is located at least in the upstream part 17 of the external shell 14.

[0092] According to a first preferred embodiment illustrated in [Fig.4], the core 20 is located both in the upstream part 16 and the downstream part 17 of the external shell 14.

[0093] According to a second embodiment illustrated in [Fig.5], the core 20 is located in the upstream part 16 and the downstream part 17 is devoid of core 20.

[0094] The arms 15 are regularly distributed around the longitudinal axis X. They are connected to the internal and external shells 13, 14 for example by internal and external bolts 15a, 15b. The arms 15 can take the form of flow straightening vanes, known by the English acronym OGV for “Outlet Guided Vane”.

[0095] The external shell 14 according to the invention directly integrates the acoustic insulation properties. Thanks to the invention, it is therefore possible to do without sectors of acoustic panels added and fixed to the external shell. The acoustic properties of the outer shell 14 are therefore greatly improved. The outer shell 14 is lighter and less expensive.

[0096] Thanks to the invention, it is also possible to acoustically insulate the entire outer shell 14, that is to say both the upstream and downstream parts 16, 17 of the outer shell 14.

[0097] A method of manufacturing the intermediate casing 12 will now be described with reference to [Fig. 6]. The manufacturing method comprises the following steps:

[0098] (a) providing the inner shell 13,

[0099] (b) connect the arms 15 to the internal ferrule 13,

[0100] (c) providing the outer ferrule 14,

[0101] (d) connect the outer ferrule 14 to the arms 15.

[0102] According to the invention, step (c) comprises the following sub-steps carried out in chronological order:

[0103] (cl) form the internal panel 18,

[0104] (c2) deposit the core 20 around the internal panel in a coaxial manner,

[0105] (c3) forming the external panel 19 coaxially around the core 20,

[0106] (c4) optionally, heat treating the inner and outer panels 18, 19, and

[0107] (c5) drill holes 18a in the inner panel 18.

[0108] Sub-steps (cl) and (c3) are advantageously carried out by an automatic fiber placement method, also known by the English acronym AFP (for “Automated Fiber Placement”).

[0109] In sub-steps (c1) and (c3), several strips 110 of pre-impregnated fibers are for example wound onto an annular support 120 using for example a robotic arm 140. The strips 110 are then advantageously compacted and heated to promote adhesion of the strips 110 to each other. The heating temperature of the strips 110 is between 400°C and 500°C, preferably between 400°C and 450°C, even more preferably 420°C when the matrix of the strips 110 is of the thermoplastic type.

[0110] When the matrix of the strips 110 is of the thermosetting type, the heating temperature is between 20°C and 120°C.

[0111] In sub-step (c2), the core 20 is deposited on the internal panel 18 preferably by additive manufacturing. This method offers the advantage of simplifying sub-step (c2) and of considering a greater variety of geometry of the honeycomb cells 21a. This example is preferred when the matrix of the internal panel 18 is of the thermoplastic type.

[0112] According to another example, in sub-step (c2), the core is deposited on the internal panel 18 manually.

[0113] According to yet another example, in sub-step (c2), the core is deposited on the internal panel 18 by a “pick and place” type placement device.

[0114] Sub-step (c4) is particularly advantageous for polymerizing the thermosetting polymer matrix and therefore consolidating the internal and external panels 18, 19. Sub-step (c4) is a curing step. It is for example carried out in an autoclave.

[0115] In sub-step (c5), the drilling of the holes 18a is for example mechanical or laser drilling.

[0116] Laser drilling is for example carried out by a laser. The laser is for example a short or ultra-short pulse power laser. The laser advantageously generates radiation with a wavelength between 1 nm and 1 mm. The radiation generated is therefore in the infrared, visible or ultraviolet range.

[0117] According to the invention, the method for manufacturing the outer shell 14 can be fully automated, which makes it possible to reduce the manufacturing time of the outer shell 14 and to considerably reduce the manufacturing costs. Also, thanks to the implementation of the automatic fiber placement method, it is possible to produce the outer shell 14 in the form of annular panels integrating the acoustic insulation properties.

[0118] This makes it possible to improve the acoustic properties of the outer shell 14 and to reduce the weight of the outer shell 14.

[0119] An installation for the manufacture of the external ferrule 14 will now be described with reference to [Fig.7].

[0120] The installation comprises a first station 100 for manufacturing the internal and external panels 18, 19, a station 200 for depositing the core 20, optionally a cooking station 300 and a drilling station 400.

[0121] With reference to [Fig.8], the first station 100 comprises for example an unwinder 130 of the strips 110 of pre-impregnated fibers. The unwinder 130 makes it possible to deposit the strips 110 on the support 120. The unwinder 130 is for example a robotic arm allowing the strips 110 to be wound onto the annular support 120. The support 120 is for example a mandrel.

[0122] The first station 100 further comprises a compacting roller 140. Advantageously, the first station 100 comprises a plurality of compacting rollers 140 regularly distributed around the support 120. The compacting roller 140 makes it possible to apply pressure to the strips 110 deposited on the support 120 in order to promote adhesion between the strips 110.

[0123] The first station 100 further comprises a heating device 150 for the strips 110. The heating device 150 makes it possible to heat the strips 110 as they are deposited on the support 120. This makes it possible to promote the adhesion of the strips 110 to each other by melting of the matrix. The combination of pressure and temperature therefore promotes the adhesion of the 110 strips to each other.

[0124] The heating device 150 is for example a laser such as an infrared laser. The heating device 150 is for example movable in rotation around the support 120.

[0125] The placement station 200 comprises, for example, an additive manufacturing device or a “pick and place” type placement device.

[0126] The additive manufacturing device comprises, for example, a first filament dispenser and a first extruder.

[0127] The cooking station 300 comprises, for example, an autoclave.

[0128] The drilling station 400 further comprises a member for drilling the internal panel. 18. The drilling device is, for example, a laser or a mechanical drill. The laser is, for example, a short-pulse or ultra-short-pulse power laser. The laser advantageously generates radiation with a wavelength between 1 nm and 1 mm. The radiation generated is therefore in the infrared, visible or ultraviolet range.

[0129] The installation according to the invention therefore allows in-line manufacture of the external shell 14.

Claims

Claims

1. Annular intermediate casing (12) for an aircraft turbomachine (1), the intermediate casing (12) having an axis of revolution (X) and comprising: - an annular inner shell (13) centered on the axis of revolution (X), - an annular outer shell (14) arranged coaxially around the inner shell (13), and - radial arms (15) connecting the inner and outer shells (13, 14), the intermediate casing (12) being characterized in that the outer shell (14) comprises: - an annular inner panel (18) centered on the axis of revolution (X) and extending around the arms (15), - an annular outer panel (19) arranged coaxially around the inner panel (18), and - an annular core (20) arranged coaxially between the inner and outer panels (18, 19).

2. Intermediate casing according to the preceding claim, characterized in that the external ferrule (14) comprises an upstream annular part (16) and a downstream annular part (17) located around the arms (15), the core (20) being located at least in the upstream annular part (16).

3. Intermediate casing according to the preceding claim, characterized in that the core (20) is located both in the upstream and downstream annular parts (16, 17).

4. Intermediate casing according to any one of the preceding claims, characterized in that the internal panel (18) comprises a first polymeric matrix and reinforcing fibers embedded in the first matrix.

5. An intermediate casing according to any one of the preceding claims, characterized in that the external panel (19) comprises a second polymeric matrix and reinforcing fibers embedded in the second matrix.

6. Intermediate casing according to claim 4 and / or 5, characterized in that the polymers of the first and / or second matrices are chosen from thermoplastics or thermosets.

7. Intermediate casing according to any one of the preceding claims, characterized in that the internal panel (18) has holes (18a).

8. Method for manufacturing an annular intermediate casing (12) according to any one of the preceding claims, characterized in that the method comprises a step (c) of producing the external shell (14), step (c) comprising the following chronological sub-steps: (cl) forming an annular internal panel (18) centered on an axis of revolution (X), (c2) depositing coaxially around the internal panel (18), an annular core (20), (c3) forming an external panel (19) coaxially around the core (20), and (c4) optionally, heat treating the internal and external panels (18, 19).

9. Method according to the preceding claim, characterized in that the sub-steps (cl) and / or (c3) are carried out by an automatic fiber placement method.

10. Method according to any one of claims 8 to 9, characterized in that it comprises, after sub-step (c4), a step (c5) of drilling the internal panel (18).