FR3121480A1 - CRANKCASE FOR AN AIRCRAFT TURBOMACHINE AND METHOD FOR MANUFACTURING CRANKCASE - Google Patents

Abstract

The invention proposes an aircraft turbomachine casing, comprising an annular casing (9) extending around an axis A and made of a composite material comprising a fibrous texture reinforcement (13; 16, 17) embedded in a resin matrix (14), the fibrous texture reinforcement (13; 16, 17) comprising at least two carbon fiber plies (16, 17). The fibrous texture reinforcement (13; 16, 17) also comprises a thickness of Kevlar (30, 30a; 31, 31a), interposed between the two carbon fiber plies (16, 17; 18, 19) in the thickness of the envelope (9). The invention also proposes a method of manufacturing such a casing (3). Figure for abstract: Figure 5

Description

CRANKCASE FOR AN AIRCRAFT TURBOMACHINE AND METHOD FOR MANUFACTURING CRANKCASE

Technical field of the invention

The present invention relates to the production of a casing, in particular of a fan, for an aircraft turbine engine.

Technical background

Conventionally, a turbomachine comprises, from upstream to downstream, that is to say in the direction of flow of the gas flows, a fan, one or more compressors, a combustion chamber, one or more turbines, and a nozzle for ejecting the combustion gases leaving the turbine or turbines.

There partially and schematically represents a fan 1 of an aircraft turbine engine.

The fan 1 comprises a blade wheel 2 which is surrounded by a fan casing 3, also called a retention casing because of its retention function in the event of ingestion of debris in the fan or loss of blade.

The fan casing 3 typically comprises an annular casing 9 with an axis of revolution A which extends around the fan blades 2 of the turbomachine. This casing includes a 3', 3'' annular fixing flange at each of its axial ends. These 3′, 3″ flanges are used to attach the casing 3 to the annular walls of the nacelle of the turbomachine.

The fan casing 3 is connected, upstream, to an air inlet sleeve 5, and, downstream, to a ferrule 6 of the intermediate casing.

The casing also includes an upstream acoustic shroud 7 and a downstream acoustic panel 8. The fan casing 3 also includes an annular layer 4 of abradable material, positioned on an annular layer called the abradable support layer 4', itself placed on a surface inner ring 9' of casing 9, between upstream shroud 7 and downstream panel 8.

In addition to the retention function, the fan housing 3 is also designed for:

• ensure mechanical continuity (of forces and moments) between the air inlet sleeve 5 and the shell 6 of the intermediate casing;
• allow the vein panels to be fixed (upstream shroud 7, acoustic panel 8 and layer of abradable material 4),
• allow attachment of equipment and supports;
• comply with fire and leak regulation specifications;
• allow continuity of the electric current for lightning resistance, etc.

To ensure its functions while minimizing its mass, the fan casing 3 is optimized by zones. There are then three types of zones: a retention zone 10, structural zones 11, respectively upstream and downstream of the retention zone 10, and the clamping zones 12 at the axial ends of the casing 3.

The retention zone 10 is located opposite the fan blades 2, for example substantially in contact with the layer of abradable material 4 ( ). The retention zone 10 ensures the primary functions of the fan casing 3, namely the static and dynamic mechanical strength, and the retention capacity, that is to say the resistance to the impacts of elements projected at high speed such as lost dawns.

The upstream and downstream structural zones 11 provide dynamic mechanical strength. They are thinned with respect to the retention zone 10, which makes it possible to limit the mass of the casing 3.

The clamping zones 12 guarantee static thermo-mechanical resistance. They work in tension, compression and shear. Finally, they ensure the connection with other parts of the aircraft on which the casing 3 is mounted.

Turbomachine casing envelopes 9 are thus known which are made of composite material comprising a fibrous texture 13 of carbon fibers embedded in a resin matrix 14. Such a fibrous texture 13 may comprise a superposition of plies of carbon fibers 16 to 19 , for example four folds, such as in . Each ply 16 to 19 comprises a multitude of interwoven weft threads 20 and warp threads 21.

The retention zone 10 of the casing 9 is dimensioned to guarantee the retention capacity of the casing 3. The retention zone 10 is thus the thickest part of the casing 9, therefore the heaviest. In addition, while carbon fibers have many advantages in terms of stiffness, their ability to absorb and dampen impact may in some cases be insufficient. Furthermore, the slightest weaving anomaly directly affects the retention capacity of the fan casing. Finally, the first layers of the retention zone work in shear while the last layer works in tension.

In an existing turbomachine, the outer surface of the casing casing is covered with plies of Kevlar, which has drawbacks related to the draping of the plies during winding (appearance of voids, compaction problems), the axial positioning of the pleats, covering and cutting pleats. Indeed, during the laying up of these plies, there is a risk of the appearance of an interlaminar void which is likely to generate material defects, which is visible during a non-destructive test.

The invention therefore aims to propose an alternative to the existing solutions of aircraft turbomachine casings with reinforced retention zone to overcome the aforementioned problems. The invention therefore proposes in particular a turbomachine casing and a method of manufacturing such a casing.

The invention thus relates to an aircraft turbomachine casing, comprising an annular casing extending around a longitudinal axis and made of a composite material comprising a fiber texture reinforcement embedded in a resin matrix, the fiber texture reinforcement comprising at least two carbon fiber plies. In this casing, the fibrous texture reinforcement further comprises a thickness of Kevlar, the thickness of Kevlar being interposed between the two plies of carbon fibers so as to form a stack.

The proposed solution thus makes it possible to reinforce the retention zone by interposing between the layers of the composite material one or more thicknesses of Kevlar. Kevlar provides better energy absorption capacity on impact than carbon fibers, while being lighter than them. The invention thus offers both the possibility of improving the retention capacity, for example in the event of impact from a lost blade or a foreign body, of limiting the number of plies of carbon fibers in the zone of retention, and thus to limit its thickness and mass.

In addition, the presence of internal thicknesses of Kevlar makes it possible to counter possible variations in the property of retention of the crankcase in the event of production hazards or a change of design.

The housing according to the invention may comprise one or more of the following characteristics, considered independently of each other or in combination with each other:

- the casing comprises a second stack comprising a respective thickness of Kevlar and at least one carbon fiber ply, the second stack then covering radially and externally the first stack on an periphery of the casing;

- The second stack comprises two carbon fiber plies distinct from the two carbon fiber plies of the first stack, and between which said respective thickness of Kevlar is interposed.

- a said thickness of Kevlar is formed from at least one ply of Kevlar with a thickness of between 0.05 mm and 1 mm, preferably between 0.1 mm and 0.3 mm;

- the, or each, thickness of Kevlar is formed exclusively from plies of Kevlar with a thickness of between 0.05 mm and 1 mm, preferably between 0.1 mm and 0.3 mm;

- the, or each, thickness of Kevlar is formed of a single fold of Kevlar, the latter having a thickness of between 0.05 mm and 1 mm, preferably between 0.1 mm and 0.3 mm;

- a said thickness of Kevlar is made of pre-impregnated Kevlar;

- a said thickness of Kevlar is made of dry Kevlar;

- the thickness of Kevlar is in woven fabric of Kevlar, which is provided with weft threads and interwoven warp threads;

- a retention zone is defined longitudinally between two axially opposite ends of an extra thickness of the casing, and/or between two axially opposite ends of a support layer of abradable material of the casing, and/or between two ends axially opposite of a layer of abradable material of the envelope, and in which a said thickness of Kevlar extends over at least 80% of the axial length of the retention zone, preferably at least 90% of this length, of preferably still all this length.

The invention also relates to an aircraft turbine engine comprising a casing comprising one or more of the characteristics defined above.

The invention further relates to a method for manufacturing an aircraft turbine engine casing as described above, the method comprising: placing on an impregnation mandrel at least two said fiber plies carbon of the fibrous texture reinforcement produced before a step of injecting resin into an impregnation mold enveloping the impregnation mandrel and the fibrous texture reinforcement. In this method, at least one said thickness of Kevlar is placed between the two said carbon fiber plies during the placement on the impregnation mandrel of the at least two said carbon fiber plies of the reinforcement in fibrous texture so as to form a said stack.

In the method of manufacturing a casing as described above, said thickness of Kevlar can be put in place, so as to be interposed between the two carbon fiber plies, by draping.

The invention may also relate to a method for manufacturing an aircraft turbomachine casing, this casing comprising an annular casing extending around a longitudinal axis and made of a composite material comprising a fibrous texture reinforcement embedded in a resin matrix, the fibrous texture reinforcement comprising at least two carbon fiber plies, the method comprising: placing on an impregnation mandrel at least two said carbon fiber plies of the fibrous texture reinforcement produced before a resin injection step in an impregnation mold enveloping the impregnation mandrel and the fibrous texture reinforcement. In this method, at least one thickness of Kevlar is placed, during the placement of the two said carbon fiber plies on the impregnation mandrel, between the two said carbon fiber plies so as to form a stack.

Brief description of figures

Other characteristics and advantages of the invention will appear during the reading of the detailed description which will follow for the understanding of which reference will be made to the appended drawings in which:

There already discussed partially shows a sectional view of a fan of an aircraft turbine engine according to the state of the art;

There illustrates in schematic section a stack of layers of a fibrous texture reinforcement of an envelope of the prior art along section line AA of the ;

There is a perspective view of a machine for draping a fibrous texture reinforcement of a composite material on an impregnation drum before injection of resin;

There partially shows a sectional view of a fan of an aircraft turbine engine according to the invention;

There illustrates in schematic section a stack of layers of a fibrous texture reinforcement of the envelope of the invention along the section line BB of the .

Detailed description of the invention

In the following description, the invention is applied to a fan casing such as the casing 3 illustrated partially in . The invention is however not limited to this type of casing and can be applied to other casings of a turbomachine.

The casing 3 to which the invention applies has a general annular shape around the longitudinal axis A. An arrow F materializes a forward direction of the elements illustrated with regard to their orientation once installed in the turbomachine.

The casing 3 comprises an annular casing 9 which itself extends around the axis A ( ). The fan casing 3 further comprises an annular layer 4 of abradable material, positioned on an annular layer called the abradable support layer 4', itself placed on an internal annular surface 9a of the casing 9.

The invention relates in particular to a retention zone 10 of the casing 9, defined longitudinally between two axially opposite ends of an extra thickness 10' of the casing 9, and/or between two ends 4'a, 4'b axially opposite sides of a support layer 4' of abradable material 4 of the casing 9, and/or between two axially opposite ends 10'a, 10'b of a layer of abradable material 4 of the casing 9.

The envelope 9 is here made of a composite material comprising a fibrous texture reinforcement 13' embedded in a resin matrix 14. More specifically, the fibrous texture reinforcement 13' is integrated into the resin matrix 14 after polymerization of the resin .

As seen in , the fibrous texture reinforcement 13' comprises a stack 25 of two fibrous texture materials. More precisely, the stack 25 comprises a thickness of Kevlar 30 as well as two plies of carbon fibers 16 and 17. The thickness of Kevlar 30 is sandwiched, that is to say interposed, between the plies 16 and 17.

Preferably, the reinforcement 13' comprises at least a second stack 26 of two materials with fibrous textures, comprising a thickness of Kevlar 31 and at least one ply of additional carbon fibers 19. The at least one second stack 26 then covers radially on the outside the first stack 25 on the periphery of the casing 9.

In the preferred example, however non-limiting, illustrated in , the second stack 26 comprises a thickness of Kevlar and two plies of carbon fibers 18 and 19. The thickness of Kevlar 30 is sandwiched between the plies 18 and 19. The structure of the reinforcement in fibrous texture 13' illustrated in then comprises, superimposed from the inside outwards: a ply of carbon fiber 16, a thickness of Kevlar 30, two plies of carbon fiber 17 and 18, another thickness of Kevlar 31, a ply of carbon fiber 19. Preferably, at least one, more preferably both, thicknesses of Kevlar 30, 31 is made of Kevlar fabric provided with weft yarns and interlaced warp yarns.

As a variant not shown, an additional stack, or several, of the type of stacks 25 and 26 may still be provided in the envelope 9.

In the example of the , each thickness of Kevlar 30 or 31 comprises a single ply of Kevlar 30a or 31a. In a variant not shown, at least one of the thicknesses of Kevlar 30 or 31 comprises at least one second ply of Kevlar 30a or 31a.

Preferably, the Kevlar ply(s) 30a and/or 31a provided above has (have) a respective thickness of 0.05 mm to 1 mm, more preferably still from 0.1 mm to 0.3mm.

Preferably, without limitation, the layer(s) of Kevlar 30 and/or 31 used in the stack(s) 25 and/or 26 is/are provided in pre-impregnated Kevlar. Alternatively, it is however possible to use dry Kevlar.

The axial length of the thickness of Kevlar 30 and/or 31 corresponds to all or part of the retention zone 10. Preferably, the length of the thickness or thicknesses of Kevlar 30 and/or 31 extends over at least 80 % of the axial length of the retention zone 10, preferably at least 90% of the length of the retention zone 10, more preferably the entire length of the retention zone 10.

A method of manufacturing a casing 3 provided with the casing 9 having at least one stack such as the stack 25 may comprise:

- a step of placing at least two carbon fiber plies 16 and 17 of the fiber texture reinforcement 13' on an impregnation mandrel 32 ( ) And,

- a step of injecting resin 14 into an impregnation mold (not shown) enveloping the impregnation mandrel 32 and the fibrous texture reinforcement 13'.

The carbon fiber plies 16-19 are preferably formed during the winding onto the impregnating mandrel 32 of a continuous carbon fiber sheet 40 from a roll of carbon fibers 41 ( ). During the winding of the plies 16 to 19, the Kevlar layers 30 and 31 can be formed by draping individual sheets of Kevlar 130 and 131. The Kevlar sheets 130 and 131 are then, preferably but not limited to, of circumferential width respective equal to or less than the dimension of a complete turn of the mandrel 32 and/or of the casing 9. The thickness(es) of Kevlar 30 and/or 31 is/are then placed around the mandrel impregnation 32, directly integrated within the fiber texture reinforcement 13'.

Draping individual sheets of Kevlar 130 and 131 while rolling up the carbon fiber sheet 40 has the advantage, due to the tension of the sheet 40 which is stretched between the roll 41 and the impregnation mandrel 32 , eliminate voids and ensure optimal compaction of Kevlar 130 and 131 sheets.

The formation of the stacks 25 and 26 is therefore carried out here directly during the step of placing the reinforcement in fibrous texture 13' on the mandrel 32, before the step of injecting resin 14 into the mold of impregnation (not shown) wrapping the mandrel 32.

Once the stacks 25 and 26 are in place, the mold is closed on the impregnation mandrel covered with the fiber texture reinforcement 13' (called the preform at this stage). The resin 14 is then injected into the mold and then polymerizes, thus giving their final shape to the resin matrix 14 and to the envelope 9.

The invention brings advantages on several levels. From a technical point of view :

• the reinforcement of the retention zone allows the use of a mechanically less efficient and therefore less expensive preform;
• the co-injection of the integrated Kevlar reinforcement with the preform makes it possible to obtain a particularly resistant connection interface.

From an industrial point of view:

• the addition of a thickness of Kevlar in the thickness of the envelope in the manner described above allows the use of a less efficient composite preform, which allows production hazards having an effect on the mechanical properties ;
• the manufacturing cycle is slightly affected thanks to the common injection which does not require additional tooling.

The invention therefore brings significant gains both technically and industrially.

Claims (10)

Aircraft turbomachine casing, comprising an annular casing (9) extending around an axis A and made of a composite material comprising a fibrous texture reinforcement (13'; 16, 17; 18, 19) embedded in a resin matrix (14), the fibrous texture reinforcement (13'; 16, 17; 18, 19) comprising at least two carbon fiber plies (16, 17),
characterized in that the fibrous texture reinforcement (13'; 16, 17; 18, 19) further comprises a thickness of Kevlar (30, 30a; 31, 31a), the thickness of Kevlar (30, 30a; 31, 31a) being interposed between the two carbon fiber plies (16, 17; 18, 19) so as to form a stack (25, 26). Casing according to the preceding claim, in which the casing (9) comprises a second stack (26) comprising a respective thickness of Kevlar (31) and at least one ply of carbon fibers (18, 19), the second stack (26 ) then radially and externally covering the first stack (25) on a circumference of the casing (9). Casing according to the preceding claim, in which the second stack (26) comprises two carbon fiber plies (18, 19) distinct from the two carbon fiber plies (16, 17) of the first stack (25), and between which said respective thickness of Kevlar (31) is interposed. Housing according to one of the preceding claims, in which a said thickness of Kevlar (30, 31) is formed from at least one fold of Kevlar (30a, 31a) with a thickness of between 0.05 mm and 1 mm , preferably between 0.1 mm and 0.3 mm. Housing according to one of the preceding claims, in which a said thickness of Kevlar (30, 31) is of pre-impregnated Kevlar. Casing according to one of the preceding claims, in which a retention zone (10) is defined longitudinally between two axially opposite ends of an extra thickness (10') of the casing (9), and/or between two ends (4 'a, 4'b) axially opposite of a support layer (4') of abradable material (4) of the casing (9), and/or between two axially opposite ends (10'a, 10'b) d 'a layer of abradable material (4) of the envelope (9), and in which a said thickness of Kevlar (30, 31) extends over at least 80% of the axial length of the retention zone (10) , preferably at least 90% of this length, more preferably all of this length. Aircraft turbomachine comprising a casing (3) according to one of the preceding claims. Method of manufacturing an aircraft turbomachine casing (3) according to one of claims 1 to 6, the method comprising:
the placing on an impregnation mandrel (32) of at least two said carbon fiber plies (16, 17) of the fiber texture reinforcement (13'; 16, 17; 18, 19) carried out before a step injection of resin (14) into an impregnation mold enveloping the impregnation mandrel (32) and the fibrous texture reinforcement (13'; 16, 17; 18, 19),
characterized in that at least one said layer of Kevlar (30, 31; 30a, 31a) is placed between the two said plies of carbon fibers (16, 17; 18, 19) during the placement on the impregnation mandrel (32) of the at least two said carbon fiber plies (16, 17) of the fibrous texture reinforcement (13'; 16, 17; 18, 19) so as to form a said stack (25 , 26). Method of manufacturing a casing (3) according to the preceding claim, in which the said thickness of Kevlar (30, 31; 30a, 31a) is put in place, so as to be interposed between the two plies of carbon fiber (16 , 17; 18, 19), by draping. Method of manufacturing an aircraft turbine engine casing (3), this casing (3) comprising an annular casing (9) extending around an axis A and made of a composite material comprising a fibrous texture reinforcement ( 13'; 16, 17) embedded in a resin matrix (14), the fibrous texture reinforcement (13'; 16, 17) comprising at least two carbon fiber plies (16, 17), the method comprising:
the placing on an impregnation mandrel (32) of at least two said carbon fiber plies (16, 17) of the fibrous texture reinforcement (13'; 16, 17) carried out before a resin injection step (14) in an impregnation mold enveloping the impregnation mandrel (32) and the fibrous texture reinforcement (13'; 16, 17),
characterized in that at least one thickness of Kevlar (30, 31; 30a, 31a) is placed, during the placement of the two said plies of carbon fibers (16, 17; 18, 19) on the impregnation mandrel (32), between said two carbon fiber plies (16, 17; 18, 19) so as to form a stack (25, 26).