METHOD FOR MANUFACTURING A BLADED PART FOR A TURBOMACHINE AND BLADED PART FOR A TURBOMACHINE OBTAINED FROM SUCH A METHOD

Abstract

The invention relates to a method (100) for manufacturing a bladed part (1) for an aircraft turbomachine, this bladed part being made of organic matrix composite (OMC) material, the method comprising the following steps: (110) providing a molding core (10) made of a material having a melting point denoted T1, the molding core having a generally elongated shape along an elongation axis (X2) and comprising a first positioning protuberance (20) located at at least one of its ends (11, 12), (120) producing a first fibrous preform (50) by three-dimensional weaving, this first preform comprising a body (54) having a generally elongated and tubular shape and comprising a cavity (57) which extends along an elongation axis (X1) of the first preform and which opens at the opposite axial ends (51, 52) of the body (54), (130) inserting the molding core (10) into the molding core (10) and then ... molding in the cavity so that their axes of elongation coincide,the first positioning protrusion (20) opening outside the cavity. Figure for the abstract: Fig. 2a,

Description

Title of the invention: METHOD FOR MANUFACTURING A BLADED PART FOR A TURBOMACHINE AND BLADED PART FOR A TURBOMACHINE OBTAINED FROM SUCH A METHOD Technical field of the invention

[0001] The invention relates to the technical field of methods for manufacturing a bladed part for a turbomachine, in particular by resin transfer molding. The invention also relates to a bladed part for a turbomachine obtained by such a manufacturing method.

[0002] The invention applies to all bladed parts for turbomachines, including rotating bladed parts such as bladed parts for a fan or a propeller, bladed parts for rectifier arms, and also bladed stator or rotor parts (vanes, blades, etc.). Technical background

[0003] In recent turbomachines, particularly aircraft turbomachines, large-sized bladed parts are increasingly frequently made of organic matrix composite (OMC) material in order to reduce their mass, while guaranteeing mechanical properties equivalent to those of bladed parts made of metallic material. Although the function and architecture of these bladed parts vary according to their position within the turbomachine, reducing their mass is a common problem regardless of the part concerned.

[0004] It is known to produce these bladed parts by laminating two-dimensional fiber reinforcements, then densified by resin, or by three-dimensional weaving of a single preform, then densified. With the more recent three-dimensional weaving technique, threads are interlaced three-dimensionally so as to obtain a fiber reinforcement, then this is impregnated in a matrix, for example injected by a resin transfer molding process. Other matrix injection processes such as stamping or thermocompression can also be used.

[0005] There are mainly two methods of manufacturing these bladed parts in the prior art.

[0006] According to a first manufacturing method known from the prior art, relatively widely used, the bladed part is solid. It is first presented in the form of a hollow part which is then filled either with composite or with foam. This method is advantageous, in particular when foam is used. Indeed, dry layup or pre-impregnation on foam is simpler than on composite. However, foam has the disadvantage of being expensive, in addition to being sensitive to moisture absorption, brittleness and a tendency to generate explosions during rapid drying. Typically, the sensitivity of foam to the environment requires either controlling the humidity of the environment in which the manufacturing is carried out or controlling and reducing its exposure time to the environment.

[0007] According to a second manufacturing method known from the prior art, the bladed part is hollow. This method is conventionally implemented by means of a molding core, also called a mandrel, made of metal or silicone which makes it possible to form the cavity of the bladed part.

[0008] Depending on the metal from which they are made, metal casting cores can be removed either by mechanical extraction or by melting. When the metal casting core is not fusible and therefore mechanical extraction must be carried out, its use is limited to the production of cavities of simple shapes. Indeed, if it were used to form cavities of complex shapes, it could not be demolded. However, most new generation bladed parts are of complex shape. When the metal casting core is fusible and can therefore be dissolved by firing, it is the presence of post-firing defects on the bladed part that raises questions. These defects require an additional firing step, which in addition to generating additional cost and additional processing time, significantly affects the mechanical properties of the bladed part.Furthermore, in this case, the repair potential of the bladed part is reduced because its duration of exposure to heat must not exceed a certain threshold.

[0009] Silicone molding cores, for their part, can only be extracted by mechanical extraction. The cavity of the preform must have a large passage section in order to allow the molding core to pass through, which limits the manufacture of bladed parts having closed cavities. In addition, the extraction of the silicone molding core from the preform requires significant mechanical effort because the surface of the molding core in contact with the preform deforms and induces significant friction. Furthermore, still in this case, the flexibility of the silicone molding core must be precisely controlled in order to avoid poor positioning of the preform and undulations of the surface of the bladed part. Indeed, the shape of the surface of the bladed part depends on the hardness of the molding core and the composite preform used.As with metal casting cores, this type of core is therefore contraindicated for the production of hollow bladed parts with complex shaped cavities.

[0010] In addition, the requirements in terms of mechanical strength are particularly high. for such bladed parts. It is the control of the fiber volume ratio that ensures the mechanical strength of the bladed part under different mechanical loads (aerodynamic loading, impacts, bird ingestion, etc.). However, to control this fiber volume ratio, the geometry of the cavity must not fluctuate during curing. It is therefore important to ensure good positioning of the molding core because if the latter is shifted from its theoretical position in the direction of the thickness of the bladed part, then the thickness will increase on one side and decrease on the other. Deviations in the fiber volume ratio of plus or minus 20% have thus been observed compared to the initially set value. In the manufacturing processes of the prior art, lasers are used to achieve alignment between the preform and the molding core.This alignment step can be very complex to implement and significantly increases the manufacturing process time. In addition, since it requires the use of a laser, it increases the total manufacturing cost.

[0011] The invention aims to overcome at least some of the aforementioned problems. Summary of the invention

[0012] The invention proposes for this purpose a method of manufacturing a bladed part for an aircraft turbomachine, this bladed part being made of organic matrix composite material, the method comprising the following steps:

[0013] (110) providing a molding core made of a material having a melting point noted Tl, the molding core having a general elongated shape along an elongation axis and comprising a first positioning protrusion located at at least one of its ends,

[0014] (120) producing a first fiber preform by three-dimensional weaving of fibers, this first preform comprising a body having a generally elongated and tubular shape and comprising a cavity which extends along an axis of elongation of the first preform and which opens at the opposite axial ends of the body,

[0015] (130) insert the molding core into the cavity of the first preform so as to that their axes of elongation are merged, the first positioning protuberance remaining outside the cavity, and carry out a forming of the first fiber preform by compression of the first fiber preform on the molding core,

[0016] (150) loading the first fiber preform and the molding core into a mold injection, said injection mold comprising at least a first housing capable of receiving the first positioning protuberance,

[0017] (160) heating the first fiber preform to a temperature noted T2, with Tl > T2, so as to polymerize a resin, said resin being either injected into the first fibrous preform is provided, with the first fibrous preform, in the form of a pre-impregnated during the three-dimensional weaving step (130),

[0018] (165) extracting the first fiber preform from the injection mold, and

[0019] (170) chemically dissolve the molding core by spraying a liquid brought to a temperature below the melting point Tl of the molding core on the molding core.

[0020] The manufacturing method according to the invention makes it possible to solve the problem linked to the extraction of the molding core from the cavity of the first fiber preform. Indeed, the molding core comprises, at at least one of its ends, a first positioning protrusion which remains projecting from the cavity of the first preform when the molding core is inserted into the cavity. Thus, when the chemical dissolution is implemented, since the first positioning protrusion is accessible from the outside of the cavity, the molding core can be dissolved progressively from said first positioning protrusion and to the other of its ends, namely the one opposite the end where the positioning protrusion is located.

[0021] Furthermore, the method according to the invention makes it possible to control the fiber volume ratio of the first fiber preform without having to use an alignment step using a laser. Indeed, in the manufacturing method according to the invention, the first positioning protrusion makes it possible to precisely position the molding core in the injection mold, and therefore makes it possible to fix the position of the first fiber preform, which contains the molding core, relative to said molding core. Indeed, the injection mold comprises at least one housing capable of receiving the first positioning protrusion. The latter therefore makes it possible to fix the position of the molding core in the injection mold and thus prevents a fluctuation of the fiber volume ratio in the first preform.

[0022] According to different characteristics of the invention which can be taken together or separately: • during the step of dissolving the molding core, the liquid is sprayed onto the first positioning protrusion and / or on the side of the first positioning protrusion; • during the chemical dissolution stage of the core, the liquid projected is a solvent for the molding core, • during the chemical dissolution stage of the core, the liquid projected is water, • during the chemical dissolution stage of the core, the liquid projected is acetone, • the molding core includes a second positioning protrusion operation extending from the other of its ends, the second positioning protrusion remaining outside the cavity after insertion of the molding core into the cavity, the injection mold comprising a second housing adapted to receive the second positioning protrusion; the first positioning protrusion and, where applicable, the second positioning protrusion, have(s) a geometric shape complementary respectively to the geometric shape of the first housing and, where applicable, of the second housing; the first positioning protrusion and, where applicable, the second positioning protrusion, protrude(s) outside the cavity by a distance at least equal to twice a side or diameter of the molding core; the first fiber preform comprises a fiber volume ratio of between 40% and 70%, with a tolerance of ± 1%, for a skin thickness of between 0.5 mm and 200 mm; the first preform further comprises two lateral lips which are diametrically opposite relative to the axis of elongation of the first preform and which extend from one of the axial ends of the body in a direction transverse to a direction of the axis of elongation; the melting point Tl is at least 10% higher than the polymerization temperature T2 of the resin; the method comprises a step in which a second fiber preform is provided and the axial end of the body at which said first positioning protrusion is located is covered, so as to close the cavity at this axial end, the second fiber preform comprising an orifice crossed by the first positioning protrusion; the method comprises after the step of inserting the molding core into the cavity and before the loading step, a step of drying the first fiber preform and the second fiber preform; the molding core is made of a composite material based on nitrates and zircon, said composite material being made of a mixture of sodium nitrate (NaNO3) for a mass content of 13.3%, zirconium silicate (SiO^r) for a mass content of 33.3%, and potassium nitrate (KNO3) for a mass content of 53.4%; the molding core is made of a metal-based composite material, said composite material comprising a first phase of formula Mn+iAlCn, where n = 1 to 3, M being a transition metal selected from the group consisting of titanium, niobium, chromium or zirconium, the composite material further comprising a second phase of formula A14C3; • the molding core is formed from several molding segments.

[0023] The invention further relates to a bladed turbomachine part obtained by the manufacturing method as previously described.

[0024] According to a particular implementation, the bladed part is a straightening arm, a vane, or a blade.

[0025] The invention further relates to a molding core for manufacturing a hollow part, in particular a bladed turbomachine part made of CMO materials produced from a first fiber preform, the molding core being made of a material having a melting point noted T1, the molding core having a general elongated shape along an elongation axis and comprising a first positioning protuberance located at at least one of its ends.

[0026] According to a preferred implementation, the molding core further comprises a second positioning protrusion located at the other of its outer ends.

[0027] According to a preferred implementation, the molding core comprises a first portion comprising the first protuberance and a second portion comprising the second protuberance, the first part of the molding core being distinct from the second part of said molding core, said first and second parts having substantially the same longitudinal dimensions.

[0028] According to a preferred implementation, the first positioning protrusion and, where appropriate, the second positioning protrusion protrude(s) outside the cavity by a distance at least equal to twice a side or diameter of the molding core. Brief description of the figures

[0029] Other objects, characteristics and advantages of the invention will appear more clearly in the description which follows, made with reference to the appended figures, in which:

[0030] - Figures 1a and 1b illustrate bladed parts for a turbomachine: [Fig. 1a] illustrating a bladed part for an unducted turbomachine and [Fig.lb] illustrating a bladed part for a ducted turbomachine;

[0031] - [Fig.2a] illustrates a first fiber preform and a molding core according to a embodiment of the invention: the molding core is being inserted into the first fiber preform;

[0032] - [Fig.2b] illustrates a first fiber preform and a molding core according to a embodiment of the invention: the molding core is completely inserted into the first fiber preform;

[0033] - [Fig.3a] illustrates a first fiber preform and a molding core according to a embodiment of the invention: only a first positioning protrusion of the molding core is visible;

[0034] - [Fig.3b] illustrates a first fiber preform and a molding core according to a embodiment of the invention while a jet of liquid is performed on the first positioning protrusion;

[0035] - [Fig.4] illustrates a molding core according to a second embodiment of the invention;

[0036] - [Fig.5] illustrates a method of manufacturing a bladed part according to a first alternative embodiment of the invention;

[0037] - [Fig.6] illustrates a method of manufacturing a bladed part according to a second variant embodiment of the invention;

[0038] - [Fig.7] illustrates a method of manufacturing a bladed part according to a third alternative embodiment of the invention. Detailed description of the invention

[0039] Figures 1a and 1b illustrate bladed parts for a turbomachine, in particular an aircraft turbomachine. These bladed parts are used to cover blades of different components of the turbomachine, among which a distinction is mainly made between rotating bladed parts and fixed, and therefore non-rotating, bladed parts. In a manner well known per se, among the rotating bladed parts are parts used to cover fan blades and propeller blades, while among the fixed bladed parts are parts used to cover flow straightening vanes, called Outlet Guide Vane (OGV), static compressor blades or even turbine blades for a turbomachine. By nature, the bladed parts for flow straighteners are used in unducted fans. An example of such a bladed part is illustrated in [Fig.1a].Other bladed parts found on static blades, such as those of the compressor or turbine, are generally used for shrouded fans. An example of such a bladed part is illustrated in [Fig.lb]. Depending on a particular implementation, the bladed part is a straightening arm, a blade, or a vane.

[0040] In the remainder of this description, we will describe the manufacture of an OGV type bladed part. However, the invention is in no way limited to OGV type bladed parts and can, on the contrary, be applied to all other bladed parts as mentioned above. In the context of the invention, these bladed parts are made of organic matrix composite (OMC) material having a three-dimensional weave of fibers. As mentioned in the preamble to this description, these materials CMOs allow the mass of the turbomachine to be reduced, while guaranteeing mechanical properties equivalent to those of bladed parts made of metallic material. The invention proposes an improved manufacturing method for bladed parts, and in particular hollow bladed parts. As a reminder, hollow bladed parts differ from solid bladed parts in that they include an empty internal cavity.

[0041] [Fig.2a] illustrates a molding core 10 and a first fibrous preform 50 or first preform 50 for producing a hollow bladed part 1 made of CMO material.

[0042] The first fibrous preform 50 is a fibrous blank of the bladed part 1 to be obtained. It therefore designates the non-final bladed part obtained at the different stages of its manufacture, the finished part being called bladed part 1. The first preform 50 can be obtained by three-dimensional weaving of fibers using a loom, for example of the Jacquard type, by providing a decoupling zone making it possible to define a cavity 57 allowing the insertion of the molding core. For example, an interlock weave armor can be used. The three-dimensional woven fabric obtained can then be pre-impregnated with a resin in order to form a pre-impregnated material. This makes it possible to simplify the manufacturing process, in particular, as will be described below, during the final shaping of the first preform 50 by heating.

[0043] The first preform 50 typically comprises a body 54 having a generally elongated and tubular shape and comprising the cavity 57 which extends along an elongation axis XI of the first preform and which opens at the opposite axial ends 51, 52 of the body. At this stage, let us specify that the elongation axis XI of the first preform is the central axis of the cavity 57 passing through the center of its axial ends 51, 52. The cavity 57 may open at one of the axial ends 51, 52 only or at both axial ends 51, 52. In other words, the cavity 57 may be open at only one of the axial ends 51, 52, or be open at both axial ends 51, 52. In the first case, it will therefore comprise an opening 58 while in the second case, it will comprise two openings 58.

[0044] In the embodiment illustrated in [Fig.2a], the first preform 50 comprises a decoupling zone at one of its axial ends, here the first axial end 51. The decoupling zone here comprises two lateral lips 55, 56 which are diametrically opposite with respect to the elongation axis XI of the first preform 50. These two lateral lips 55, 56 extend from the first axial end 51 of the body in a direction substantially orthogonal to the elongation axis XI of the first preform, in this case a direction of axis Z. They therefore laterally delimit the opening 58 or one of the openings 58 of the cavity.

[0045] The molding core 10, also called a mandrel or insert, is used to make the cavity 57 and therefore the complex external shape of the bladed part 1. It is used exclusively during the manufacture of the bladed part 1, and in particular during the curing of the first preform 50 to give its final shape to the bladed part 1. The molding core 10 is made of a material having a melting point noted Tl. Preferably, and as will be better understood below, the melting point Tl of the molding core 10 is at least 10% higher than the polymerization temperature of the resin giving its shape and rigidity to the first preform 50, which makes it possible to carry out the curing of the first preform 50 without altering the mechanical integrity of the molding core 10.

[0046] Like the body 54 of the first preform, the molding core 10 has a general elongated shape along an elongation axis X2. It comprises a first end 11, a second end 12 and a first positioning protrusion 20 or first protrusion 20 located at at least one of its ends 11, 12. At this stage, let us specify that the elongation axis X2 of the molding core 10 is the central axis of the molding core passing through the center of its ends 11, 12. As will be seen in more detail below, the first positioning protrusion 20 makes it possible to fix the position of the first preform 50 during molding. In the exemplary embodiment illustrated in the figures, the first positioning protrusion 20 has a different shape from the end at which it is located, namely the first end 11.In this case, the first protuberance 20 has a parallelepiped shape while the first end 11 has a shape similar to that of a biconvex lens. However, this is not obligatory since the first protuberance 20 may have the same shape as the first end 11 and, moreover, have the same dimensions as the first end 11. The first protuberance 20 may also have any other shape, for example a conical, cylindrical, spherical shape, etc. The first protuberance 20 may be formed in a single piece with the molding core 10 or may be attached to the first end 11 of the molding core. It is nevertheless preferable for it to be formed in a single piece with the molding core in order to avoid disassembly of the molding core during the manufacture of the bladed part 1.

[0047] It may also be specified that the molding core 10 may be formed from several molding segments. These molding segments constitute independent parts of the molding core which, once assembled, give the molding core its final shape. The molding segments may be manufactured independently of one another, which facilitates the manufacture of the molding core 10. This is particularly advantageous when the first preform 50 has small dimensions, i.e. dimensions greater than 100 mm. Indeed, geometric compatibility problems may arise for the insertion of the molding core 10 in the first preform 50.

[0048] The molding core 10 may, in addition, comprise a second positioning protrusion 22 or second protrusion 22 extending from the other of its ends, in this case the second end 12. The second protrusion 22 has the same functions as the first protrusion 20. It may also have the same shape and the same dimensions as the first protrusion 20, however this is not obligatory and it may be different from the first protrusion 20. This second protrusion 22 may be provided when the cavity 57 of the first preform 50 is open at both axial ends 51, 52.

[0049] In this regard and as illustrated in [Fig. 4], the molding core 10 may comprise a first portion 13 comprising the first protuberance 20 and a second portion 14 comprising the second protuberance 22, said first 13 and second 14 portions being intended to form distinct portions of the molding core. In this regard, the molding core 10 may be produced as illustrated in [Fig. 4]. This comprises an intermittent cut along a center line, located between the first end 11 and the second end 12 of the molding core, which makes it possible to separate the two portions of the molding core 10 at the time of manufacture, if necessary.This configuration is particularly advantageous when it is desired to limit the size of the molding core 10 or when it is desired to facilitate the insertion of the molding core 10 into the cavity 57 of the first preform, in particular when the first protuberance 20 and the second protuberance 22 have a different shape and / or dimensions from the end, respectively first end 11 and second end 12, at which they are located. Indeed, they constitute means for gripping the molding core 10.

[0050] Furthermore, this is particularly advantageous when seeking to produce cavities 57 of complex and / or non-symmetrical shapes. Indeed, the first portion 13 can be inserted independently of the second portion 14 into the cavity 57 of the first preform.

[0051] The molding core 10 may be made of a nitrate- and zircon-based CMO material, or a metal-based one.

[0052] According to a first preferred implementation, the CMO material is based on nitrates and zircon, said CMO material being made of a mixture of sodium nitrate (NaNO3) for a mass content of 13.3%, zirconium silicate (SiO4Zr) for a mass content of 33.3%, and potassium nitrate (KNO3) for a mass content of 53.4%. This mixture is particularly advantageous because it makes the molding core 10 capable of contracting under the effect of the temperature and, possibly, pressure conditions, used during the curing phase, a phase which will be described in more detail below. Once these temperature and, possibly, pressure conditions have been reached, the molding core 10 is able to contract under the effect of the temperature and, possibly, pressure conditions, used during the curing phase, a phase which will be described in more detail below. pressure, are filled, the molding core 10 can then be easily removed from the cavity because a clearance appears between it and the first preform 50. The removal of the molding core is therefore facilitated. In addition, this makes it possible to manufacture the bladed part 1 without chemical disturbance thereof, in particular by oxidation.

[0053] According to a second preferred implementation, the CMO material is metal-based, said composite material comprising a first phase of formula Mn+iAlCn, where n = 1 to 3, M being a transition metal chosen from the group consisting of titanium, niobium, chromium or zirconium, the CMO material further comprising a second phase of formula ACCs. A CMO material having such a formulation allows the production of a molding core of complex shape, while allowing easy and rapid extraction of said molding core 10, without resorting to chemical solutions potentially harmful to the bladed part 1 to be manufactured subsequently and to the environment. Such a molding core 10 made of such a material can, moreover, be recycled.

[0054] Although its use is less suitable for bladed parts with complex shapes, a silicone molding core 10 could also be used, in particular for the manufacture of bladed parts 1 with a simple shape.

[0055] With reference to Figures 5 to 7, we will now describe in more detail the different steps of the method 100 for manufacturing the bladed part according to the invention (hereinafter “the method”). In Figures 5 to 7, the optional steps are indicated by boxes made of dotted points.

[0056] During a first step 110 of the method 100, the molding core 10 is provided as previously described. At this stage, it should be recalled that the second protuberance 22 is not obligatory, as in the case where the cavity 57 of the first preform is closed at one of its ends 51, 52. Similarly, it should be recalled that a molding core 10 like that described in relation to [Fig. 4], which comprises two portions, is also not obligatory for the same reasons.

[0057] During a second step 120 of the method 100, a first preform 50 such as that described previously is produced, and comprising the body 54, a cavity 57 which extends along the axis of elongation XI of the first preform and which opens out at the opposite axial ends 51, 52 of the body 54. In practice, this second step 120 can be carried out indifferently before, concomitantly, or after the first step 110 of supplying the molding core 10.

[0058] During a third step 130 of the method 100, and as illustrated in FIGS. 2a and 2b, the molding core 10 is inserted into the cavity 57 of the first preform so that their respective elongation axes XI, X2 coincide, the first protuberance 20 remaining outside the cavity 57. [Fig. 2a] illustrates a start-of-stroke position during this step of inserting the molding core 10 in the cavity 57 while [Fig.2b] illustrates an end-of-travel position. According to one aspect of the method according to the invention, the first positioning protrusion 20 remains outside the cavity 57 of the first preform. In other words, at least a portion of the first protrusion 20 is outside the cavity 57 when the molding core 10 is completely inserted into the cavity 57. In other words, at least a portion of the first protrusion 20 projects relative to a plane orthogonal to the elongation axis XI of the first preform, this plane passing through the first axial end 51.

[0059] After the complete insertion of the molding core 10 into the first preform 50 and when the molding core 10 comprises a second protuberance 22 at the other of its ends 11, 12, this second protuberance 22 also remains outside the cavity 57. As already mentioned, the use of a second protuberance 22 is more particularly indicated when the cavity 57 opens out at its two ends 51, 52. In this case, and similarly to what has been seen for the first protuberance 20, the molding core 10 is configured so that at least a portion of the second protuberance 22 is outside the cavity 57 when the molding core 10 is completely inserted into the cavity 57.Thus, the first protrusion 20 remains outside the cavity 57 at one 51, 52 of the axial ends of the first preform 50 while the second protrusion 22 remains outside the cavity 57 at the other 52, 51 of the axial ends of the first preform.

[0060] Still during this third step 130 of the method 100, the first preform 50 is formed by compressing the first preform 50 onto the molding core 10. This makes it possible to adapt the shape of the cavity 57 to that of the molding core 10 so that an inner surface of the cavity 57 matches the contours of an outer surface of the molding core 10. Indeed, at this stage, the first preform 50 has not yet undergone baking, so that it can be deformed as desired. At the end of the third step 130, the molding core 10 and the first preform 50 are assembled so that the cavity 57 matches the contours of the molding core 10, the first protuberance 20 remaining outside the cavity 57.

[0061] During a fourth step 150 of the method 100, the first preform 50 and the molding core 10 are loaded into an injection mold, this injection mold comprising at least a first housing capable of receiving the first protuberance 20. The injection mold is typically a mold suitable for performing resin transfer molding. As previously introduced, the first protuberance 20 makes it possible to fix the position of the first preform 50 during molding. Indeed, the first protuberance 20 is configured to fit into the first housing of the injection mold (not shown) so that there is little or no play between the first protuberance 20 and the first housing of the injection mold. In these conditions, the molding core 10 is stabilized and the first preform 20 adopts its final position in the injection mold, which makes it possible to control the geometric shape of the cavity 57, and therefore the internal shape of the bladed part 1 to be manufactured, relative to the external shape of said bladed part 1. The injection mold can advantageously comprise a second housing capable of receiving, if necessary, the second protuberance 22 of the molding core, which further secures the position of the molding core 10 within the injection mold.

[0062] The cooperation of the protuberance(s) with the housing(s) makes it possible to fix the position of the molding core 10 and to control the fiber volume ratio in the thickness of the first preform 50 and therefore of the bladed part 1 to be manufactured, by limiting the tolerance around the nominal fiber volume ratio to 1%. For example, the first preform 50 comprises a fiber volume ratio of between 40% and 70%, with a tolerance of ± 1%, for a skin thickness of between 0.5 mm and 200 mm. The minimum fiber volume ratio values ​​are not necessarily associated with the minimum thickness values. Similarly, the maximum fiber volume ratio values ​​are not necessarily associated with the maximum skin thickness values. For example also, the first preform 50 comprises a fiber volume rate of 60%, with a tolerance of ± 1%, for a skin thickness equal to 4 mm.It should be noted that the skin thickness is not necessarily uniform along the fiber preform or from one side of said fiber preform to the other. Many design variations can be envisaged by those skilled in the art depending on the intended application.

[0063] It is advantageous for the first protuberance 20 and, where appropriate, the second protuberance 22, to have a geometric shape complementary respectively to the geometric shape of the first housing and, where appropriate, of the second housing. Thus, the first protuberance 20 and the first housing, and where appropriate the second protuberance 22 and the second housing, form a built-in connection, which prevents the molding core 10 from moving relative to the injection mold and secures the positioning of the molding core 10 in the injection mold. For example, the first positioning protuberance 20 and the first housing and, where appropriate, the second positioning protuberance 22 and the second housing, may consist of an assembly chosen from a tenon / mortise system, dovetail, or an ergo / hole system. These assemblies all make it possible to create a built-in connection between the molding core 10 and the injection mold.

[0064] It is also advantageous for the first protuberance 20 and, where appropriate, the second positioning protuberance 22, to project outside the cavity 57 by a distance at least equal to twice a side or diameter of the core of molding. This makes the positioning of the molding core 10 in the injection mold even more reliable since it provides a larger contact surface between the first protrusion 20, where applicable the second protrusion 22, and the first housing, where applicable the second housing.

[0065] The method 100 according to the invention is therefore more reliable, simpler and less expensive than the methods known from the prior art since it makes it possible to guarantee the positioning of the molding core 10 in the injection mold and therefore makes it possible to obtain a homogeneous fiber volume rate, that is to say with a tolerance of ± 1% over the entire skin of the bladed part 1 without needing to use separate alignment equipment, such as a laser for example.

[0066] During a fifth step 160 of the method 100, the first preform 50 is heated to a temperature denoted T2, with T1 strictly greater than T2, so as to polymerize the resin, this resin being either injected into the first preform 50 - then in the form of dry fibers - or provided, with the first preform 50, in the form of a pre-impregnated during the three-dimensional weaving step 130. The purpose of this step is to stiffen the first fibrous preform 50 which, as a reminder, is made by three-dimensional weaving of fibers. Thus, at the end of the fifth step, the first preform 50 acquires its final shape. In practice, the temperature T2 varies from one CMO material to another. The temperature T2 is the temperature making it possible to implement, that is to say to give its final shape, to the first preform 50.The temperature T2 therefore depends essentially on the resin chosen since it is necessary to ensure that the resin can melt so that the impregnation of the first preform 50 is sufficient.

[0067] The fifth step 160 may comprise a first sub-step 162 of injecting the resin making it possible to impregnate the three-dimensional woven fabric from which the first preform 50 is made when said three-dimensional woven fabric is not pre-impregnated or sufficiently impregnated beforehand. When such a first injection sub-step 162 is necessary, the fifth step 160 then comprises a second sub-step 164 during which the first preform 50 is heated to a temperature T2. However, the injection of resin is not obligatory because the three-dimensional woven fabric from which the first preform 50 is made may be pre-impregnated with a resin. In this case, the fifth step 160 simply amounts to heating the first preform 50. It is therefore appropriate to take into account the temperature at which the resin changes state.

[0068] At this stage, it can probably be specified that it is particularly advantageous for the melting point T1 of the molding core to be at least 10% higher than the temperature T2 to which the first preform 50 is heated. Such a difference makes it possible to guarantee that the structural integrity of the molding core 10 will not be affected. during the baking of the first preform 50, which would be likely to modify the shape of the cavity 57 and therefore also modify the fiber volume ratio. For example, the baking temperature T2 of the first preform 50 may be 200°C for a class 180 epoxy resin.

[0069] During a seventh step 170 of the method 100, the molding core 10 is chemically dissolved by spraying a liquid brought to a temperature below the melting point T1 of the molding core 10 onto the molding core 10. At the end of this step, the molding core 10 is completely dissolved and can be easily extracted from the cavity 57. The weight of the bladed part 1 thus formed is therefore considerably reduced in comparison with the bladed parts which comprise full cavities, as described in the preamble to this description.

[0070] The projected liquid may for example be water if the molding core 10 is made of a material comprising salt since water is a solvent for this material. In this case, the water may be heated to accelerate the dissolution of the molding core. According to a particular implementation, the water may be heated to 60°C. That being said, by projecting the water at pressures between 2 and 6 bars, the same effect is obtained. If the molding core 10 is made of a polymer or a mixture of polymers, acetone may be used as a solvent for the dissolution of said molding core. The invention is in no way limited to any one of these liquids and, depending on the material from which the molding core 10 is made, the nature of the liquid to be projected may vary. In this regard, as can be deduced from the above, it is not obligatory to heat the projected liquid or even to project a liquid under pressure.The temperature and pressure at which the liquid is projected can be adapted according to the nature of the material from which the molding core 10 is made and the operator's needs in terms of manufacturing time.

[0071] According to a preferred implementation, the liquid can be sprayed onto the first positioning protrusion 20 and / or on the side of the first positioning protrusion 20. Thus, since the first protrusion 20 is accessible from outside the cavity 57, it is possible to use this first protrusion as an entry point for dissolving the molding core 10. That being said, this step can be implemented without going through the first protrusion 20. The molding core 10 can in fact comprise extraction holes allowing the liquid to access said molding core 10. As an alternative or in addition, it is also possible to provide extraction holes in the bladed part 1 to access the molding core.The use of the first protuberance 20 to dissolve the molding core is particularly advantageous since, unlike the methods described above, it does not require drilling the bladed part 1 itself and / or the molding core 10.

[0072] Still during the dissolution step 170, pressurized liquid can advantageously be used, which makes it possible to accelerate the dissolution of the molding core 10 and to evacuate it more quickly. Preferably, the liquid has a pressure greater than or equal to 5 bars. A spraying means 70 can then be used to spray the liquid.

[0073] In a second embodiment of the manufacturing method 100 according to the invention illustrated in Figures 3a and 3b, the fourth step of the method is a step 140 during which a second fiber preform 60 is provided and the axial end 51, 52 of the body at which the positioning protrusion is located is covered, so as to close the cavity 57 at this axial end. In the illustrated embodiment, it is the first end 51 of the first preform which is covered. However, this depends on the axial end at which the first protrusion 20 is located when the molding core 10 is inserted into the first preform. The second fiber preform 60 or second preform 60 makes it possible to close the cavity 57, and therefore makes it possible to prevent objects or insects from becoming lodged therein during manufacturing. Like the first preform 50, the second preform 60 can be made by three-dimensional weaving of fibers.It can also be made of the same CMO material as the first preform 50 but this is not obligatory since it is intended to be separated from the first preform 50 at the end of the manufacturing process 100 in order, for example, to be recycled.

[0074] Still according to this second embodiment, the second preform 60 comprises an orifice (not visible) crossed by the first protuberance 20. Thus, when the second preform 60 covers the first end 51 of the first preform 50, the opening 58 of the cavity can be completely closed if this was not the case. No object or insect can enter the cavity 57 by this means. The opening 58 may not be completely closed, in particular after the molding core 10 has been inserted into the internal cavity 57 and although the first preform 50 has been compressed onto the molding core 10, when the opening 58 is not sufficiently limited. This can occur when the first protrusion does not match the contours of the opening 58. In Figures 3a and 3b, the second preform 60 completely covers the lips 55, 56 of the first preform.However, what is important is that the second preform 60 completely covers the opening 58 of the cavity.

[0075] Then, as can be well understood, the manufacturing method 100 continues with the steps 150, 160 and 170 as previously described.

[0076] According to a particular implementation of the first and second embodiments of the method 100 according to the invention, the method 100 comprises a step of drying the first preform 50 and, where appropriate, the second preform 60. The drying makes it possible to stabilize the first preform 50. It is preferable to carry out this step of drying before the loading step 150 of the first preform and the molding core 10 into the injection mold. As was seen for the heating step 160, it is preferable, during this drying step, to position the molding core 10 by means of the first protuberance 20 so that the position of said molding core 10 is fixed relative to that of the first preform 50. This makes it possible to keep the volume rate of fiber in the first preform 50 constant.

[0077] With reference to [Fig.5] and according to a first variant, when this drying step is implemented within the framework of a manufacturing method 100 according to the first embodiment (without the second preform 60), said drying step 135 is carried out after the step 130 of inserting the molding core 10 into the cavity 57 and before the step 150 of loading the first preform 50 into the injection mold.

[0078] In the case where this drying step is implemented within the framework of a manufacturing method 100 according to the second embodiment (with the second preform 60), according to a second embodiment variant illustrated in [Fig. 6], said drying step 145 is carried out after the step 140 of supplying the second preform and before the step 150 of loading the first preform 50 into the injection mold. The first preform 50 and the second preform 60 can then be dried together. That being said, according to a third embodiment variant illustrated in [Fig. 7], the drying step 144 is a sub-step of step 140, which allows the first preform 50 and the second preform 60 to be dried separately.In this case, a first sub-step 142 of step 140 consists of providing the second preform 60, a second sub-step 144 of step 140 consists of carrying out the drying of the first preform 50 and the second preform 60 together or separately and a third sub-step 146 consists of covering the axial end of the body at which the first protuberance 20 is located, so as to close the cavity 57 at this axial end.

[0079] According to a particular implementation, the method 100 comprises, after the step 170 of demolding the molding core 10, a step 180 of closing a first passage left by the first positioning protrusion 20 and, where appropriate, a second passage left by the second positioning protrusion 22. Here, it is a question of closing the cavity 57 in order to prevent, once the bladed part 1 has been manufactured and installed, elements from the environment from becoming lodged inside the cavity 57 and degrading the physicochemical and mechanical properties of the bladed part, for example by exposure to fluids such as kerosene, oils, water, or weighing down the bladed part 1 by an accumulation of sand, debris and insects.

[0080] In this regard, it can also be provided that the section of the opening 58 used for inserting the molding core 10 into the cavity 47 is smaller than the opening that would be provided for a rigid-section molding core, such as a silicone molding core. This therefore reduces the risk of objects or other elements being introduced into the cavity 57, without however completely preventing their introduction.

[0081] The configurations shown in the cited figures are only possible examples, in no way limiting, of the invention which on the contrary encompasses the design variants within the reach of those skilled in the art.

Claims

Claims

1. Method (100) for manufacturing a bladed part (1) for an aircraft turbomachine, this bladed part being made of organic matrix composite (OMC) material, the method comprising the following steps: (110) providing a molding core (10) made of a material having a melting point denoted T1, the molding core (10) having a generally elongated shape along an elongation axis (X2) and comprising a first positioning protuberance (20) located at at least one of its ends (11, 12), (120) producing a first fiber preform (50) by three-dimensional weaving of fibers, this first preform comprising a body (54) having a generally elongated and tubular shape and comprising a cavity (57) which extends along an elongation axis (X1) of the first preform and which opens at the opposite axial ends (51, 52) of the body (54),(130) inserting the molding core (10) into the cavity (57) of the first preform so that their elongation axes coincide, the first positioning protrusion (20) remaining outside the cavity (57), and forming the first fibrous preform (50) by compressing the first fibrous preform (50) onto the molding core (10), (150) loading the first fibrous preform (50) and the molding core (10) into an injection mold, said injection mold comprising at least a first housing capable of receiving the first positioning protrusion (20), (160) heating the first fibrous preform (50) to a temperature denoted T2, with T1 > T2, so as to polymerize a resin, said resin being either injected into the first fibrous preform (50) or provided, with the first fibrous preform (50) in the form of a pre-impregnated during the three-dimensional weaving step (130),(165) extracting the first fibrous preform (50) from the injection mold, and, (170) chemically dissolving the molding core (10) by spraying a liquid heated to a temperature lower than the melting point Tl of the molding core (10) onto the molding core (10).

2. A manufacturing method according to claim 1, wherein in the step of dissolving the molding core (10) the liquid is sprayed on the first positioning protrusion (20) and / or on the side of the first positioning protrusion (20).

3. Manufacturing method according to any one of claims 1 or 2, wherein, during the step (170) of chemical dissolution of the core, the liquid sprayed is a solvent for the molding core (10), said solvent being for example chosen from water and acetone.

4. A manufacturing method (100) according to any one of claims 1 or 2, wherein the molding core (10) comprises a second positioning protrusion (22) extending from the other of its ends (12, 11), the second positioning protrusion (22) remaining outside the cavity (57) after the insertion (130) of the molding core (10) into the cavity (57), the injection mold comprising a second housing adapted to receive the second positioning protrusion (22).

5. Manufacturing method (100) according to any one of the preceding claims, in which the first positioning protrusion (20) and, where appropriate, the second positioning protrusion (22), have(s) a geometric shape complementary respectively to the geometric shape of the first housing and, where appropriate, of the second housing.

6. A manufacturing method (100) according to any preceding claim, wherein the first positioning protrusion (20) and, where appropriate, the second positioning protrusion (22), protrude(s) outside the cavity (57) by a distance at least equal to twice a side or diameter of the molding core.

7. Manufacturing method (100) according to any one of the preceding claims, in which the first fibrous preform (50) comprises a volumetric fiber content of between 40% and 70%, with a tolerance of ± 1%, for a skin thickness of between 0.5 mm and 200 mm.

8. A manufacturing method (100) according to any one of the preceding claims, wherein the first preform (50) further comprises two lateral lips (55, 56) which are diametrically opposite relative to the axis of elongation (XI) of the first preform and which extend from one of the axial ends of the body in a direction transverse to a direction of the axis of elongation (XI).

9. A manufacturing method (100) according to any preceding claim, wherein the melting point T1 is at least 10% compared to the resin polymerization temperature T2.

10. Manufacturing method (100) according to any one of the preceding claims, comprising a step (140) in which a second fibrous preform (60) is provided and the axial end (51) of the body at which said first positioning protrusion (20) is located is covered with this second preform (60), so as to close the cavity (57) at this axial end, the second fibrous preform (60) comprising an orifice crossed by the first positioning protrusion (20).

11. Manufacturing method (100) according to the preceding claim, comprising after the step (130) of inserting the molding core (10) into the cavity (57) and before the loading step (150), a step (135, 144, 145) of drying the first fibrous preform (50) and the second fibrous preform (60).

12. Manufacturing method (100) according to any one of the preceding claims, wherein the molding core (10) is made of a composite material based on nitrates and zircon, said composite material being made of a mixture of sodium nitrate (NaNO3) for a mass content of 13.3%, zirconium silicate (SiO4Zr) for a mass content of 33.3%, and potassium nitrate (KNO3) for a mass content of 53.4%.

13. A manufacturing method (100) according to any one of claims 1 to 11, wherein the molding core (10) is made of a metal-based composite material, said composite material comprising a first phase of formula Mn+iAlCn, where n = 1 to 3, M being a transition metal selected from the group consisting of titanium, niobium, chromium or zirconium, the composite material further comprising a second phase of formula AI4C5.

14. A method (100) according to any preceding claim, wherein the molding core (10) is formed from a plurality of molding segments.

15. A bladed part (1) of a turbomachine obtained by the manufacturing method (100) according to any one of the preceding claims, the bladed part being, for example, a straightening arm, a vane, or a blade.

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