METHOD FOR PRODUCING A BLADED COMPONENT FOR AN AIRCRAFT TURBINE ENGINE

Description

Technical field of the invention

[0001] The present invention relates to a method of manufacturing a bladed part for an aircraft turbomachine. Technical background

[0002] The technical background includes, in particular, documents US-B2-10,532,521 and US-B2-11,141,938.

[0003] A bladed part of an aircraft turbomachine is, for example, a rotor blade or a stator blade. Such a part comprises a blade which has an aerodynamic profile and a general shape elongated along an X axis, commonly called the “stacking” axis in the technique considered. The part may comprise a platform at at least one of the longitudinal ends of the blade along the aforementioned X axis. This platform extends in a transverse direction relative to the X axis, that is to say in a plane perpendicular to this axis.

[0004] There figure 1represents for example an air flow straightener which is a bladed part 10 whose blade 12 is connected to a platform 14 at each of its longitudinal ends.

[0005] It is known and advantageous to produce a bladed part in composite material, from a fiber preform embedded in a polymer matrix which is obtained by polymerization of a thermosetting resin or consolidation of a thermoplastic resin.

[0006] In this case, the preform can be made by three-dimensional weaving of fibers forming weft and warp threads, or by stacking fiber sheets. These fibers are impregnated with resin or this resin is injected into the preform after it has been shaped, for example by RTM technology, which is the acronym for Resin Transfer Molding and which is a well-known technique for producing a blade by injection molding.

[0007] Document WO-A2-2013 / 088040 describes the production of bladed parts from three-dimensional woven preforms.

[0008] In the case of the production of a bladed part equipped with one or more platforms, it is described in this document that portions of the preform can be located in the platform by producing at least one decoupling of the preform.

[0009] In this application, delinking means the act of separating a unitary structure into two independent substructures. In the example illustrated in figure 2, the central portion 16 of the preform 18 remains unitary and the end portions 20 of the preform 18 are each separated into two portions 22 by a separation of the preform 18. Each of the portions 22 may comprise several layers of fibers. The portions 22 are thus separated from each other and are folded to orient them in a direction perpendicular to the axis X of the central portion 16. The two portions 22 located at a longitudinal end of the preform 18 are intended to form one of the platforms 14 or to be integrated into this platform, and the two portions 22 located at the opposite longitudinal end of the preform 18 are intended to form the other platform 14 or to be integrated into this other platform.

[0010] There Figure 3aillustrates a decoupling as achieved in the current art. At each of the end portions 20 of the preform 18, the decoupling is achieved so that the portions 22 are connected together, at the junction between the first and second portions 20, by a connecting line 24 which is rectilinear and can extend perpendicular to the X axis.

[0011] The inventors have found that this straight or rectilinear line 24 creates a preferred axis of rotation or deformation of the bladed part 10, which therefore tends to deform around this line when it is subjected to operating constraints (aerodynamic pressures, forces of the engine structure, etc.). This deformation is not desired and can impair the service life of the bladed part 10 and the performance of the turbomachine.

[0012] The present invention provides a simple, effective and economical solution to this problem. Summary of the invention

[0013] The present invention relates to a method of manufacturing a bladed part for an aircraft turbomachine, in accordance with claim 1, this bladed part comprising a blade having a stacking axis and at least one longitudinal end of which is connected to a transverse platform, the method comprising the steps of: a) producing a fiber preform, this preform having a general shape elongated along said axis and planar, this preform comprising a first part intended to form the blade and at least one second part which is located at a longitudinal end of the preform and which is intended to form a platform, this second part of the preform comprising a decoupling defining two superimposed portions separated by a decoupling surface substantially parallel to the X axis, b) folding the portions respectively on two opposite sides of the first part, and c) stiffening the preform, characterized in that, in step a), the delinking is such that the portions are connected together, at the junction between the first and second parts, by a connecting line which has a generally wavy shape.

[0014] The wavy shape, for example sinusoidal, of the connecting line makes it possible to eliminate the axis of rotation or deformation mentioned above and thus stiffens the connection between the platform and the blade. The bladed part thus has improved mechanical strength and service life.

[0015] The method according to the invention may comprise one or more of the following features or steps, taken alone or in combination with each other: the connecting line comprises at least one or three corrugation antinodes; step a) is carried out by three-dimensional weaving of fibers forming weft threads and warp threads, the warp threads extending along the X axis and the weft threads extending perpendicular to the axis, the weft threads extending continuously in the first part and extending discontinuously in the second part, being interrupted at said uncoupling surface; step c) is carried out by injecting resin into the preform, and polymerizing this resin; step a) is carried out by stacking fiber sheets, the fiber sheets extending along the X axis; step c) is carried out by thermocompression of the preform, the fibers of which are previously impregnated with a resin; the connecting line has an amplitude of between 2 and 20 mm, and preferably between 5 and 10 mm; it comprises, between steps b) and c), a step of forming the preform;the method comprises a following step d) of forming the platform, either by attaching and fixing elements to the portions, or by overmolding these portions.; Brief description of the figures

[0016] Other characteristics and advantages of the invention will appear during the reading of the detailed description which follows for the understanding of which reference will be made to the appended drawings in which: [ Fig. 1 ] there figure 1 is a schematic perspective view of a bladed part of an aircraft turbomachine, which is here an airflow straightener; [ Fig.2 ] there figure 2 is a very schematic view of a preform whose end parts have undergone debonding; [ Fig.3a-3b ] THE Figures 3a and 3b show preforms with debonds, according to the technique prior to the Figure 3a and according to the invention to the Figure 3b ; [ Fig.4 ] there figure 4is a partial schematic view of a preform with several variant embodiments of a delinking according to the invention; [ Fig.5a-5b ] THE Figures 5a and 5b are schematic perspective views of a preform which has undergone debonding in accordance with the invention, as well as consolidation; [ Fig.5c-5d ] THE Figures 5c and 5d are sectional views along lines AA and BB of the Figure 5a ; [ Fig.6a ] there Figure 6a is a schematic perspective view of a bladed part in accordance with the invention, with overmolding; [ Fig.6b ] there Figure 6b is a sectional view along lines AA of the Figure 6a ; [ Fig.7 ] there figure 7 is a schematic perspective view of a preform being debonded by a tool such as a set of blades; and [ Fig.8 ] there figure 8 is another schematic sectional view of the preform and the tool of the figure 7 . Detailed description of the invention

[0017] THE Figures 1 and 2can be considered as illustrating a bladed part 10 within the meaning of the invention.

[0018] This bladed part 10 comprises a blade 12 having a stacking axis X and at least one longitudinal end of which is connected to a transverse platform 14.

[0019] The invention relates to a method of manufacturing this bladed part, which comprises the steps of: a) production of a preform 18 made of fibers, this preform 18 having a generally elongated and flat shape, this preform 18 comprising a first part 16 intended to form the blade 12 and at least one second part 20 which is located at a longitudinal end of the preform 18 and which is intended to form a platform 14, this second part of the preform 18 comprising a separation defining two superimposed portions 22 separated by a separation surface substantially parallel to the axis X, this separation being produced so that the portions 22 are connected together, at the junction between the first and second parts, by a connection line 26 which has a generally wavy shape (cf. Figure 3b ), b) fold the portions 22 respectively on two opposite sides of the first part 16 (cf. figure 2 ), and c) stiffen the preform.

[0020] Y defines an axis perpendicular to X. The preform 18 extends in the XY plane.

[0021] A wavy 26 connecting line means that in the XY plane the value of X varies along the Y axis.

[0022] There figure 4 shows several variants of the corrugated connecting line 26. It can be seen that the line 26 can comprise several corrugation antinodes, for example between 2 and 3. This figure also shows that the amplitude T1, T2 of the corrugations can vary and is for example between 2 and 20mm, and preferably between 5 and 10mm. The bladed part has for example a length along the X axis which is between 10 and 500mm, and preferably between 50 and 200mm.

[0023] In step a), the preform may be manufactured by three-dimensional weaving of fibers, in particular carbon fibers, forming weft threads and warp threads, for example using a Jacquard-type loom. The warp threads extend along the X axis and the weft threads extend perpendicular to the X axis, as shown in figure 2 . Step b) is then carried out by cutting the weft threads at the level of the unlinking surface, using a cutting tool 28.

[0024] In this configuration, there is a portion where the preform is woven throughout the thickness and a portion where the definition of the weave is such that no weft yarn crosses the plane of the unbonding surface. The portions on either side of this plane are therefore not bonded together.

[0025] THE figures 7 and 8 illustrate an example of a tool for opening the delink. The tool comprises several blades 30, 34 superimposed and capable of sliding over each other.

[0026] The principle of the blades 30, 34 is to help form the delinking by unfolding the two portions 22 of the preform progressively so as to create desired radii for connecting the blade to the platform, without undulation of the preform. In practice, one begins by inserting a blade 30 between the two unlinked portions of the preform. Then one inserts on each side additional blades 34 having edges 32 in the shape of the desired radius, ensuring not to create a preform fold, for example by unfolding the preform manually and applying a slight pull in the direction of unfolding. There may be several “blades” in this case and one preferably always starts from the center towards the outside of the radius to avoid folds.

[0027] Step c) of stiffening the preform 18 is preferably carried out by injecting resin into the preform, previously positioned in a mold.

[0028] The technology used here may be of the RTM type, or of another type (known to those skilled in the art) chosen from: VARTM, CRTM, polyflex, etc.

[0029] The polymerization of the resin allows for complete hardening and rigidification of the preform.

[0030] Alternatively, step a) can be carried out by stacking fiber sheets. The fiber sheets extend along the X axis and are stacked along an axis perpendicular to the XY plane. The delinking is carried out during stacking, avoiding joining the fiber sheets constituting one of the portions 22 with the fiber sheets constituting the other portion 22. The fibers used for producing the preform can be continuous or discontinuous fibers, impregnated or not impregnated. In the case of the use of fiber sheets, the sheets can be formed by pre-impregnated long discontinuous fibers, by unidirectional and randomly arranged fiber coupons, etc.

[0031] In this case, step c) of stiffening the preform 18 is preferably carried out by thermocompression of the preform 18. This step may include a prior sub-step of humidification of the preform. This humidification step may make it possible to soften a substance coating the fibers which is intended to facilitate their weaving. The thermocompression then makes it possible to mix the substances of the fibers together and thus bind the fibers of the preform, which contributes to its stiffening after cooling. The resin may be a thermosetting or thermoplastic resin (epoxy - for example PR520, bismaldeide, etc.). The fibers of the preform 18 are preferably made of carbon. The injection of the resin, or even the thermocompression, are carried out in a mold and preferably in two separate molds. The or each mold comprises a hollow impression for receiving the preform 18.

[0032] Between the aforementioned steps b) and c), the method according to the invention may comprise a step of forming the preform. This step is optional and consists of applying pressure to the preform to shape it. This operation may be accompanied by heating, it may also be carried out on a preform wetted with water, it may be carried out by drawing a vacuum to remove the moisture. This step makes it possible to stabilize the preform before tilting it into the injection or thermocompression mold.

[0033] THE Figures 5a to 5dallow the rigidified preform 18 to be visualized. Due to the wavy shape of the connecting line 26, the portions 22 located on either side of the blade 16 themselves have a wavy shape in three dimensions. Each of these portions 22 can be pierced to receive a screw 36 for fixing the bladed part. Each of these portions 22 can also receive at least one part 37 added to form the platform 12, or can receive an overmolding 38 to form this platform, as shown in Figures 6a and 6b .

[0034] The method according to the invention makes it possible to obtain greater stiffness and a greater moment of inertia of the connection of the blade to the platform of the bladed part. The bladed part is subjected during operation to aerodynamic forces (air pressure on the blade) and structural forces (relative movements with casings). These forces pass from the platforms to the blade or vice versa. The stiffening of the junction between the blade and the platform(s) makes it possible to limit the risks of deformation of the bladed part and thus optimizes the performance of the engine.

Claims

1. A method for producing a bladed component (10) for an aircraft turbine engine, this bladed component (10) comprising a blade (12) having a stacking axis (X) and having at least one longitudinal end connected to a transverse platform (14), the method comprising the steps of : a) producing a fibrous preform (18), this preform (18) having a generally elongate shape along said axis (X) and being flat, this preform (18) comprising a first part (16) that is intended to form the blade (12) and at least one second part (20) which is situated at a longitudinal end of the preform (18) and which is intended to form a platform (14), this second part (20) of the preform (18) comprising a disconnect defining two superimposed portions (22) separated by a disconnect surface substantially parallel to the axis (X), b) folding the portions (22) respectively on two opposite sides of the first part (16), and c) stiffening the preform (18), characterized in that, in step a), the disconnect is such that the portions (22) are connected together, at the junction between the first and second parts (16, 20), by a connecting line (26) which has a generally undulating shape.

2. The method according to claim 1, wherein the connecting line (26) comprises at least one or three undulation antinodes.

3. The method according to claim 1 or 2, wherein step a) is carried-out by three-dimensional weaving of fibers forming weft threads and warp threads, the warp threads extending along the axis (X) and the weft threads extending perpendicularly to the axis (X), the weft threads extending continuously in the first part (16) and extending discontinuously in the second part (20) and being interrupted at said disconnect surface.

4. The method according to the preceding claim, wherein step c) is carried out by injecting resin into the preform and polymerizing this resin.

5. The method according to claim 1 or 2, wherein step a) is carried out by stacking fiber mats, the fiber mats extending along the axis (X).

6. The method according to the preceding claim, wherein step c) is carried out by thermocompression of the preform (18), the fibers of which are previously impregnated with a resin.

7. The method according to one of the preceding claims, wherein the connecting line (26) has an amplitude (T1, T2) of between 2 and 20 mm, and preferably between 5 and 10 mm.

8. The method according to one of the preceding claims, wherein it comprises, between steps b) and c), a step of forming the preform.

9. The method according to one of the preceding claims, wherein it comprises a subsequent step d) of forming the platform (14), either by mounting and attaching elements to the portions (22), or by overmolding these portions.