Method for manufacturing a fibrous preform of a blade

Abstract

The invention relates to a method for producing a fibrous preform (15), the method comprising the steps of: (a) providing a blank (22) comprising at least first and second layers (23, 24) which each comprise weft threads (26), the weft threads of each of the first and second layers being interconnected by the same warp threads (27); (b) unbinding the warp threads and the weft threads over a portion (Pli) of the first layer so as to form floating threads (28); (c) cutting the floating threads, characterised in that step (c) comprises the sub-steps of - (cO) positioning a protective mat (29) between the floating threads of the first layer and the second layer, and - (cl) cutting the floating threads with a motorised rotary cutting tool (30).

Description

[0001] DESCRIPTION

[0002] TITLE: METHOD FOR MANUFACTURING A FIBROUS PREFORM OF A BLADE

[0003] Technical field of the invention

[0004] The invention relates to the field of methods for manufacturing fiber preforms for aircraft turbomachine blades.

[0005] The invention relates in particular to the field of methods for manufacturing fiber preforms comprising a step of cutting the fiber preform.

[0006] Technical background

[0007] 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.

[0008] The blower allows the suction of an air flow divided 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.

[0009] The primary flow is compressed within the compressors. The compressed air is then mixed with fuel and burned within the combustion chamber. The gases from the combustion pass through the turbines and then escape through the nozzle, whose cross-section allows the acceleration of these gases to generate propulsion.

[0010] The fan typically comprises a mobile disc rotating about the longitudinal axis and blades extending radially from the disc. Each blade typically comprises a radially extending blade having an aerodynamic shape. The blade thus has a pressure face and an extrados face connected by a leading edge and a trailing edge. The blade typically has a variable thickness, in particular a thickness which decreases towards the trailing edge.

[0011] The blades can be made of metallic material. However, in order to reduce the overall weight of the turbomachine while preserving the mechanical properties of the blades, it has been proposed to make the blades of composite material. The composite material of the blades typically comprises a polymer matrix and fibers embedded in the polymer matrix. The polymer matrix is, for example, an epoxy resin. The fibers are, for example, glass or carbon fibers. The fibers are typically organized in the form of a three-dimensional fiber preform of the blade.

[0012] The three-dimensional fiber preform typically comprises a plurality of layers of woven yarns. The number of layers depends on the thickness of the blade. Each layer comprises weft yarns that are connected together by the same warp yarns forming a weave of the layers.

[0013] In order to provide a blade of variable thickness, it is necessary to manufacture a three-dimensional fiber preform of equally variable thickness. A fiber preform of variable thickness translates into a fiber preform in which the number of layers of yarns varies. To produce such a preform, a blank of the fiber preform is first produced. In this step, the blank of the fiber preform has a constant thickness equal to the greatest thickness of the blade. Then, the warp yarns are removed from a portion of a layer so that in this portion, the warp yarns and the weft yarns are untied. The unwoven and therefore untied warp yarns and weft yarns are generally called "float yarns". These float yarns are subsequently cut, which results in a fiber preform of variable thickness.

[0014] Although it can provide a fiber preform of variable thickness, such a manufacturing process is not entirely satisfactory. Indeed, cutting the floated yarns is an operation carried out manually by operators using cutting scissors. It is therefore a tedious, long and costly step. Furthermore, performing this step manually represents a health risk for operators who must make significant efforts to cut the blank.

[0015] Finally, since the blank is cut manually, there is a high risk of accidentally cutting woven wires from an underlying layer that are not intended to be cut. This creates a risk of non-compliance and the blade being scrapped.

[0016] Therefore, there is a need to provide a solution that allows a fiber preform with variable thickness to be provided in a simple, fast, reliable and inexpensive manner.

[0017] Summary of the invention

[0018] To this end, the invention proposes a method for manufacturing a fiber preform of an aircraft turbomachine blade, the method comprising the following steps:

[0019] (a) providing a blank having a three-dimensional weave, the blank comprising at least first and second layers of woven yarns, the first and second layers each comprising weft yarns, the weft yarns of each of the first and second layers being connected together by the same warp yarns,

[0020] (b) untying the warp and weft yarns on a portion of the first layer to form floated yarns,

[0021] (c) cut the floating threads from this part of the first layer.

[0022] The manufacturing process is remarkable in that step (c) comprises the following sub-steps:

[0023] (cO) positioning a protective mat between the floating threads of the first layer and the second layer, and

[0024] (c1) cutting the floated wires with a motorized rotary cutting tool. According to the invention, the step of cutting the blank therefore uses on the one hand a protective mat and on the other hand a motorized cutting tool.

[0025] The motorized cutting tool allows the cutting of the floated wires of the blank efficiently, i.e. without effort for the operator, more precisely, i.e. limiting the risks of accidental cutting of the wires of the second layer and offering improved safety for the operator.

[0026] In addition, the protective mat helps protect the second layer wires from accidental cutting when handling the cutting tool, which improves the reliability of the cutting step by reducing scrap.

[0027] The invention may comprise one or more of the following features, taken in isolation from each other or in combination with each other:

[0028] - the cutting tool comprises a gripping handle and a rotating cutting blade connected to the gripping handle,

[0029] - the rotating blade is circular and mobile in rotation around its axis of revolution,

[0030] - the rotating blade has a diameter between 20 mm and 100 mm, preferably between 30 mm and 50 mm,

[0031] - the rotating blade comprises a metallic material,

[0032] - the cutting tool further comprises a housing mounted around the rotating blade and having a suction duct,

[0033] - the casing is made of polymeric material,

[0034] - the cutting tool includes a motor for driving the rotating blade,

[0035] - the protective mat comprises a polymeric material, preferably chosen from thermoplastics,

[0036] - the protective mat has a thickness of between 1 mm and 10 mm, preferably between 1 mm and 5 mm. The invention also relates to a method for manufacturing an aircraft turbomachine blade, the manufacturing method comprising the following steps:

[0037] - provide the fiber preform according to the manufacturing process of the fiber preform according to any of the above characteristics,

[0038] - densify the fiber preform.

[0039] Advantageously, the densification step includes the following steps:

[0040] - place the fiber preform in a mold,

[0041] - inject a resin into the mold.

[0042] Brief description of the figures

[0043] 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: Figure 1 is a schematic representation in longitudinal section of a half-turbomachine of an aircraft, Figure 2 is a schematic representation in perspective of a blade, Figure 3 is a schematic representation in perspective of a part of the fiber preform of the blade of Figure 2, Figure 4 is a schematic representation in section along a plane parallel to the third direction, of a blank of the fiber preform, in a first step of the method of manufacturing the fiber preform, Figure 5 is a schematic representation in section along a plane parallel to the third direction, of the blank in a second step of the method of manufacturing the fiber preform,Figure 6 is a schematic representation in section along a plane parallel to the third direction, of the blank in a third step of the method of manufacturing the fiber preform, Figure 7 is a perspective representation of the cutting tool according to the invention, Figure 8 is a block diagram of the manufacturing method according to the invention.,

[0044] Detailed description of the invention

[0045] An example of a turbomachine 1 for an aircraft is shown in Figure 1. The turbomachine 1 extends around and along a longitudinal axis A.

[0046] 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 A.

[0047] The terms "axial", "axially", "radial", "radially" are defined in relation to the longitudinal axis A.

[0048] The terms "internal", "interior", "internally", "external", "exterior", "exteriorly", are defined in relation to the distance from the longitudinal axis A along a radial axis.

[0049] 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.

[0050] 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 A.

[0051] The fan 2 comprises a disc movable in rotation about the longitudinal axis A and blades 10 extending radially from the disc. The fan 2 further comprises a fan shaft 2a connected to the low pressure shaft 8 via a speed reducer 11 for example.

[0052] The fan 2 may be of the ducted type. The turbomachine 1 may therefore comprise a fan casing 2b. The fan casing 2b is annular and centered on the longitudinal axis X. It is arranged around the blades 10. According to another example, the fan 2 may be of the unducted type.

[0053] The blower 2 allows the suction of an air flow F dividing into a primary air flow F1 and a secondary air flow F2. The primary air flow F1 passes through a primary vein v1 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 v1.

[0054] 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 section of which allows the acceleration of these gases to generate propulsion.

[0055] With reference to Figure 2, each blade 10 comprises a blade 12 extending between a head 13 and a root 14. The blade 12 has an aerodynamic shape and comprises a lower surface face 12i and an upper surface face (not visible) connected by a leading edge 12a and a trailing edge 12b.

[0056] Each blade 10 has a variable thickness. For example, the blade 10 has a first thickness e1 as measured at the leading edge 12a greater than a second thickness e2 as measured at the trailing edge 12b. In particular, the thickness of the blade 10 decreases towards the trailing edge 12b.

[0057] According to the invention, each blade 10 comprises a composite material. The composite material is an organic matrix material, also known by the acronym CMC. The composite material thus comprises fibers embedded in an organic matrix. The fibers are, for example, glass fibers, or carbon fibers, or ceramic fibers, or polyester fibers, or polypropylene fibers, or polyamide fibers. The organic matrix is, for example, chosen from thermosetting polymers such as epoxy resins or thermoplastic polymers such as polyolefins.

[0058] The fibers are typically organized in the form of a three-dimensional fiber preform 15 of the blade 10.

[0059] With reference to Figure 3, the fiber preform 15 comprises a plurality of layers 16, 17, 18 of woven yarns. The layers 16, 17, 18 are stacked in a first direction X1 defining the thickness of the fiber preform 15. Each layer 16, 17, 18 comprises weft yarns 20 which extend in a second direction X2. The weft yarns 20 of the layers 16, 17, 18 are connected to each other by warp yarns 21 which extend in a third direction X3 perpendicular to the first and second directions X1, X2. In other words, the weft yarns 20 and the warp yarns 21 of the layers 16, 17, 18 are interlaced to form a weave. Advantageously, the weave is of the interlock type. Any other type of weave is applicable to the invention.

[0060] The fiber preform 15 has a variable thickness in accordance with the profile of the blade 10 along a profile chord of the blade 10 or along the longitudinal axis A. The fiber preform 15 comprises at least a first part P1 having a first thickness eT and a second part P2 having a second thickness e2' for example less than the first thickness eT. In the first part P1 of the fiber preform 15, the number of layers 16, 17, 18 is greater than the number of layers 16, 17, 18 in the second part P2.

[0061] An example of a method of manufacturing the blade 10 will now be described with reference to FIG. 8. The method of manufacturing the blade 10 may comprise the following steps:

[0062] (100) providing the fiber preform 15, and

[0063] (200) densify the fiber preform 15.

[0064] The densification step (200) may comprise the following steps:

[0065] (201) placing the fiber preform 15 in a mold, and (202) injecting a resin into the mold.

[0066] According to the invention, the method for manufacturing the fiber preform 15 comprises the following steps:

[0067] (a) providing a blank 22 of the fiber preform 15, the blank 22 comprising first and second layers 23, 24 of woven yarns and optionally at least one third layer 25 of woven yarns, the first and second layers 23, 24 each comprising weft yarns 26, the weft yarns 26 of each of the first, second and third layers 23, 24, 25 being connected to each other by the same warp yarns 27,

[0068] (b) untying the warp threads 27 and the weft threads 26 on a first part P11 of the first layer 23 to form floated threads 28, and

[0069] (c) cut the floating wires 28 from this first part P11 of the first layer 23.

[0070] With reference to Figure 4, in step (a), the blank 22 of the fiber preform 15 of the blade 12 has a constant thickness e11. The thickness e11 of the blank 22 during this step (a) is equal to the first thickness e1' of the first part P1 of the fiber preform 15.

[0071] In step (a), the weaving of the threads of the blank 22 is advantageously of the interlock type.

[0072] With reference to Figure 5, during step (b), the warp threads 26 are removed from the first part P11 of the blank 22, for example manually. At the end of this step (b), in this first part P11, the warp threads 27 and the weft threads 26 are untied and are therefore no longer intertwined. The untied warp threads 27 and the weft threads 26 are floated threads 28.

[0073] With reference to Figure 6, according to the invention, step (c) of cutting the floated wires 28 comprises the following steps:

[0074] (cO) positioning a protective mat 29 between the floating wires 27 of the first layer 23 and the wires 26, 27 of the second layer 24, and

[0075] (c1) cutting the floating wires 28 with a motorized rotary cutting tool 30. The protective mat 29 allows the protection of the wires of the second layer 25 during the cutting step (c) in order to limit the risks of accidental cutting of the wires of the second layer 25.

[0076] The protective mat 29 can extend for example over the entire first part P11 along the second and third directions X2, X3.

[0077] The protective mat 29 comprises a polymeric material. The polymeric material may be a thermoplastic polymer or a thermosetting polymer. The thermoplastic polymer is, for example, chosen from polyolefins, fluoropolymers, styrenic polymers, polyacrylic polymers, polyamides, polyesters or polychlorides. Preferably, the thermoplastic polymer is a polyvinyl chloride (PVC). The thermosetting polymer is, for example, chosen from epoxy resins.

[0078] The protective mat 29 may comprise a plurality of superimposed protective layers. The protective mat 29 comprises, for example, three protective layers 29.

[0079] Advantageously, the protective mat 29 has a thickness of between 1 mm and 10 mm, preferably between 1 mm and 5 mm, even more preferably 3 mm. Such a thickness of the protective mat 29 allows easy handling while guaranteeing effective protection of the wires of the second layer 25 during the cutting step (c).

[0080] The rotating and motorized cutting tool 30 allows for quick and effortless cutting by an operator. The operator's health is preserved and manufacturing rates are increased compared to manual cutting without a motorized cutting tool. The cutting tool 30 allows for precise cutting and further limits the risk of accidental cutting of wires of the second layer 24.

[0081] Preferably, the cutting tool 30 comprises a gripping handle 31 and a rotary cutting blade 32 connected to the gripping handle 31. The gripping handle 31 makes it easier to grip the cutting tool 30. The gripping handle 31 has an elongated shape. Such a shape of the gripping handle 31 makes it possible to increase the safety of the operator by moving the rotary blade 32 away.

[0082] The gripping handle 31 may comprise a coating. The coating particularly comprises a polymeric material such as polyurethane or polyamide.

[0083] The rotating blade 32 has a circular or annular shape. It thus has an axis of revolution R. The rotating blade 32 has a diameter for example between 20 mm and 100 mm, preferably between 30 mm and 50 mm, even more preferably 45 mm. The diameter of the rotating blade can be adjusted according to the dimensions of the blank 22. The rotating blade 32 can have a rotation speed between 150 rpm and 300 rpm, preferably between 200 rpm and 250 rpm, even more preferably 240 rpm, the acronym rpm corresponding to the expression “rotations per minute”.

[0084] The rotary blade 32 comprises a metallic material, such as titanium. Such a material allows efficient cutting of the float wires 27. The rotary blade 32 may be diamond-coated.

[0085] According to an advantageous embodiment illustrated in Figure 7, the cutting tool 30 comprises a casing 33 mounted around the rotating blade 32. The casing 33 advantageously comprises a semi-annular body 34 centered on the axis of revolution R and a suction duct 35 extending projecting from the body 34.

[0086] The body 34 is connected to the gripping handle 31 and is fixedly mounted around the rotating blade 32.

[0087] The suction duct 35 allows the suction of debris generated during the cutting step (c), thus avoiding contamination of the blank 22 and consequently of the fiber preform 15. The suction duct 35 may have a diameter of between 20 mm and 50 mm, preferably between 20 mm and 30 mm, even more preferably 27 mm. The suction duct 35 may be connected to a suction device.

[0088] The casing 33 is preferably made of polymeric material. This makes it possible to reduce the total weight of the cutting tool 30. The cutting tool 30 comprises, in a manner not illustrated, a motor for driving the cutting blade 30.

[0089] Thanks to the automated cutting tool 30 and the protective mat 29 according to the invention, it is possible to carry out efficient, reliable, rapid and safe cutting of the blank 22 of the fiber preform 15.

Claims

CLAIMS 1. Method for manufacturing a fiber preform (15) of a blade (12) of an aircraft turbomachine (1), the method comprising the following steps: (a) providing a blank (22) having a three-dimensional weave, the blank (22) comprising at least first and second layers (23, 24) of woven yarns, the first and second layers (23, 24) each comprising weft yarns (26), the weft yarns (26) of each of the first and second layers (23, 24) being connected to each other by the same warp yarns (27), (b) untying the warp threads (27) and the weft threads (26) on a part (P11) of the first layer (23) to form floated threads (28), (c) cut the floating wires (28) from this part (P11) of the first layer (23), characterized in that step (c) comprises the following sub-steps: (cO) positioning a protective mat (29) between the floating wires (28) of the first layer (23) and the second layer (24), and (c1) cutting the floated wires (28) with a motorized rotary cutting tool (30).

2. Manufacturing method according to the preceding claim, characterized in that the cutting tool (30) comprises a gripping handle (31) and a rotary cutting blade (32) connected to the gripping handle (31).

3. Manufacturing method according to the preceding claim, characterized in that the rotating blade (32) is circular and movable in rotation around its axis of revolution (R).

4. Manufacturing method according to claims 2 and 3, characterized in that the rotating blade (32) has a diameter between 20 mm and 100 mm, preferably between 30 mm and 50 mm.

5. Manufacturing method according to one of claims 2 or 3 or 4, characterized in that the rotating blade (32) comprises a metallic material.

6. Manufacturing method according to one of claims 2 to 5, characterized in that the cutting tool (30) further comprises a casing (34) mounted around the rotating blade (32) and having a suction duct (35).

7. Manufacturing method according to the preceding claim, characterized in that the casing (34) is made of polymeric material.

8. Manufacturing method according to claim 2 or any one of the preceding claims in combination with claim 2, characterized in that the cutting tool (30) comprises a motor for driving the rotating blade (32).

9. Manufacturing method according to any one of the preceding claims, characterized in that the protective mat (29) comprises a polymeric material, preferably chosen from thermoplastics.

10. Manufacturing method according to any one of the preceding claims, characterized in that the protective mat (29) has a thickness of between 1 mm and 10 mm, preferably between 1 mm and 5 mm.

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