METHOD FOR PRODUCING A RING SECTOR

Abstract

The invention relates to a three-dimensionally woven multi-layer fibrous structure (20) having the same number of warp threads woven at any level in the warp direction, the fibrous structure (20) comprising, in the warp direction, a first portion (22) and a second portion (24), the first portion (22) having a thickness, measured in a direction perpendicular to the warp and weft directions, which is greater than that of the second portion (24), characterised in that the spacing between two weft planes in the warp direction is greater in the second portion than that in the first portion (22), and in that the number of weft threads is smaller in the second portion (24) than in the first portion (22).

Description

[0001] DESCRIPTION

[0002] TITLE: Manufacturing process for a ring sector

[0003] Technical field of the invention

[0004] The present invention relates to the manufacture of a fibrous structure for the production of composite parts intended to be integrated, for example, into a turbomachine.

[0005] Prior art

[0006] Composite parts, particularly ceramic matrix composites (CMCs), are increasingly used to replace metal parts in turbomachinery. Indeed, CMCs exhibit particularly advantageous high-temperature mechanical properties, ideal for the design of, for example, turbine stators or distributors. In these two examples, segmented CMCs are arranged and assembled on a metal housing and connected by sealed joints to ensure the flow remains sealed despite the thermal expansion caused by high operating temperatures.

[0007] In the field of aeronautics, for the aforementioned applications, the CMC materials used are based on SiC fibers and SiC matrix.

[0008] SiC fibers are incorporated into CMC material as fibrous structures, obtained, for example, through three-dimensional weaving. This is a multilayer weave using several layers of weft yarns and several layers of warp yarns, with warp yarns connecting the different layers of weft yarns. Various types of 3D weave structures can be used, such as interlock, multi-satin, multi-plain, and multi-twill weaves.

[0009] Figure 1 represents a stator sector 2 intended to be mounted radially opposite the tips of moving blades. It comprises two radial flanges 4 spaced axially apart and internally connected to an annular wall sector 6, which includes a central portion 8 connecting the two flanges 4 and spurs 10 extending in opposite directions from the axial ends of the central portion 8. The terms "radial" and "axial" are to be understood in relation to the axis A of the angular sector, this axis corresponding to the axis around which a plurality of sectors are intended to be arranged to surround a bladed wheel.

[0010] As can be seen in Figure 1, the central portion 8, also called the bathtub, has a thickness e pc greater than the thickness of the spoilers e t The thickness is measured in the radial direction. This is directly related to the manufacturing process of the fibrous structure 12.

[0011] To create the ring sector 2 of Figure 1, a fibrous structure 12, as shown in Figure 2, is first constructed. This fibrous structure 12 comprises a central portion 14 connected at each end to a first 16 and a second 18 portion, unbound from each other. The central portion 14 of the fibrous structure 12 is intended to form the central portion 8 of the ring sector 2, and the first 16 and second 18 portions are intended to form the spoilers.

[0012] 10 and the flanges 4 of the ring sector 2.

[0013] The central portion 14 comprises x layers of woven warp threads, the first portions 16 each comprise z layers of woven warp threads, and the second portions 18 each comprise y layers of woven warp threads. The warp threads are arranged in a thickness indicated in the figure by the direction E.

[0014] The absence of a connection in thickness between the first 16 and second 18 portions allows them to be structurally independent of each other and therefore to be shaped in different directions in a mold.

[0015] Thus, once the fibrous structure 12 is obtained, it is shaped to present a form similar to the desired part, i.e. in "Pi" in the example considered, as illustrated in figure 3. The first portions 16, on either side of the central part 14, are thus deployed so as to obtain a fibrous preform presenting the "Pi" topology of the ring sector 2 presented in figure 1.

[0016] With the current weaving technique, the warp / weft ratio is identical at every point of the woven piece. Thus, the number of warp layers in the central part 14 depends on the number of warp layers in the first 16 and second 18 sections, and are related by the following formula x = y + z.

[0017] The interdependence of the number of warp and weft layers, with a constant warp / weft ratio, and therefore of their respective thicknesses, of the central part 14 and the first 16 and second 18 portions, generates a functionally unnecessary thickness at the level of the central part 14. Indeed, the central part 8 functionally requires a thickness e pc minimum equivalent to the thickness e b 10 spoilers. It is also possible to have a thickness of pc of the central part 8 substantially greater than the thickness e b spoilers 10. This excess thickness results in the use of a functionally unnecessary amount of fibrous material, while this material is an expensive element.

[0018] 11 It is therefore necessary, for reasons of cost and also mass, to reduce the thickness of the central part 14 of the fibrous structure 12, and thus to obtain a fibrous structure 12 with variable thickness.

[0019] A technique known as "trimming" is used in the design of organic matrix composite (OMC) blades. This method involves removing warp and weft yarns from the fibrous structure by changing the weave pattern. The removed yarns are then cut, resulting in a fibrous structure with a thickness that varies along the warp direction. This method cannot be used for a ceramic matrix composite (CMC) part, primarily due to the fragility of the fibers used. The trimming method would weaken the resulting fibrous structure and, consequently, the preform.

[0020] Furthermore, the small dimensions of the aforementioned parts imply having small preforms, on which it is difficult to produce warp thread exits, which would then be cut according to the trimming process.

[0021] The invention aims to remedy the aforementioned drawbacks in a reliable, simple and inexpensive manner.

[0022] Summary of the invention

[0023] The present document relates first of all to a three-dimensionally woven multilayer fibrous structure having the same number of warp yarns woven at every level along the warp direction, the fibrous structure comprising, in the warp direction, a first part and a second part, the first part having a thickness, measured in a direction perpendicular to the warp and weft directions, greater than the second part, characterized in that the spacing between two weft planes along the warp direction is greater in the second part than in the first part, and in that the number of weft yarns is less in the second part than in the first part.

[0024] Thus, by varying the warp-to-weft ratio by adjusting two parameters—the spacing between two successive weft columns along the warp direction and the local insertion or removal of weft yarns—the thickness of the second part is no longer dependent on the thickness of the first part. The resulting fibrous structure, obtained through three-dimensional weaving, exhibits a first-part thickness greater than the second-part thickness.

[0025] The number of weft threads per weft plane of the second part may be less than the number of weft threads per weft plane of the first part.

[0026] This method is therefore compatible with the production of fibrous structures for CMC parts, as it does not require the use of the trimming method to vary the thickness.

[0027] The first part of the fibrous structure may comprise a first portion and a second portion, the first portion being arranged, along said perpendicular direction, above a second portion and being structurally independent of the second portion, said first portion and second portion of the first part being woven to the second part at a transition from the first part to the second part.

[0028] The first and second portions of the fibrous structure, in particular, constitute the elements of the fibrous structure that, once formed, will constitute the beak and the flange of the ring sector. Forming in directions, preferably perpendicular, of the first and second portions is permitted thanks to this structural independence. The number of weft threads can be greater than the number of warp threads in one or both of the first and second portions.

[0029] Another way to reduce the thickness of the second part is to vary the warp-to-weft ratio in the first part, that is, in the first and second sections of the first part. This reduces the number of warp layers to be woven in the second part.

[0030] In the second part, the number of weft threads can be less than the number of warp threads.

[0031] The non-insertion of certain weft threads, present in the basic weave, is thus carried out in order to modify the warp / weft ratio, by modifying or not the spacing between the weft columns, within the limit of a ratio of 75 / 25, thus allowing the thickness to be reduced compared to the thickness of the first part.

[0032] The spacing between two warp planes can be identical in the first and second parts. In practice, this is simpler to achieve than a variable spacing. The spacing between two weft planes can be identical in the first and second parts, while the spacing between two warp planes can be different.

[0033] In the specific case not illustrated of weaving pieces at 90° to the orientation presented in this document, it is conceivable to play with the spacing between two successive warp planes while keeping the spacing between two successive weft planes constant.

[0034] In practice, it is easier to modify the parameters related to the weft threads on the loom. Thus, it is easier to set the parameters related to the spacing between two successive warp layers and the number of warps in the first and second layers.

[0035] The fibrous structure may include a third part identical to the first part and woven to the second part along the warp direction opposite to the first part.

[0036] The third part of the fibrous structure may comprise a first portion and a second portion, the first portion being arranged, along said perpendicular direction, above a second portion and being structurally independent of the second portion, said first portion and second portion of the third part being woven to the second part at a transition from the first part to the second part.

[0037] The number of weft threads per weft plane in the second part is preferably less than the number of weft threads per weft plane in the third part. In this example, the fibrous structure has an axis of symmetry, similar to the ring sector presented previously. The fibrous structure is therefore shaped into a "Pi" shape, close to the desired ring sector. Thus, such a fibrous structure can form a preform with a thickness in the second part that can be less than or equal to the thickness of the first and third parts. The second part, forming the central or tub section of the fibrous preform, then has a suitable and sufficient thickness with regard to the thermal and mechanical requirements necessary for the use of this part.

[0038] This document also relates to a method of manufacturing a fibrous structure as described above, in which, during the warp direction transition from the first part of the fibrous texture to the second part of the fibrous texture, the number of weft yarns is decreased and the spacing between two successive weft planes along the warp direction is increased.

[0039] Furthermore, this document also relates to a manufacturing process for a fibrous structure as described above, in which, during the warp direction transition from the second part of the fibrous texture to the first part of the fibrous texture, the number of weft yarns is increased and the spacing between two successive weft planes along the warp direction is decreased.

[0040] This document also relates to a manufacturing process for a composite material, comprising the following steps:

[0041] a) Obtaining a fibrous structure using the process as described above; b) Conformation of the fibrous structure;

[0042] c) Obtaining a composite material by injecting a matrix inside the fibrous structure.

[0043] The resulting composite material then contains a reduced amount of fibrous material, thereby reducing its production cost and mass.

[0044] The invention will be better understood and other details, features and advantages of the invention will become apparent upon reading the following description, given by way of non-limiting example with reference to the accompanying drawings.

[0045] Brief description of the figures

[0046] [Fig. 1] described previously, is a perspective view of a ring sector according to the prior art;

[0047] [Fig. 2] described previously, is a schematic representation of a fibrous structure for the fabrication of the ring sector of figure 1 obtained according to the previous technique; [Fig. 3] described previously, is a schematic representation of the 3D Pi conformation of the fibrous structure of a ring sector;

[0048] [Fig. 4] is a schematic illustration of the fibrous structure according to the invention;

[0049] [Fig. 5] is a schematic of a ring sector incorporating the fibrous structure of Figure 4. Detailed description of the invention

[0050] In the embodiments detailed below, the woven fibrous structure, preferably made from SiC fibers, has a target fiber volume fraction between 25 and 50%. Figure 5 is a diagram of a fibrous structure 20 according to the invention, showing a warp direction C, a weft direction T, and a direction E, these directions being perpendicular to each other. This fibrous structure 20 has the same number of warp yarns woven at every level of the fibrous structure along the warp direction C.

[0051] The fibrous structure 20 comprises a first part 22, a second part 24, and a third part 26 along the warp direction C, best seen in the schematic illustration of the fibrous structure 20 before shaping. The first 22, second 24, and third 26 parts each have a thickness ei, b2, q3 measured along a direction E perpendicular to the warp and weft directions. In this example, the fibrous structure 20 includes a second part 24 whose thickness e2 is less than the thickness ei, e2 of each of the first part 22 and the third part 26.

[0052] The first 22 and third 26 parts each comprise a first portion 16 and a second portion 18. Once the fibrous structure 20 is shaped into Pi as seen in Figure 5, the first portions 16 of the first 22 and third 26 parts are arranged to form a non-zero angle, preferably between 0° and 45°, with the second portions 18 of the first 22 and third 26 parts respectively.

[0053] Before this conformation of the fibrous structure 20, that is, at the end of the three-dimensional weaving, for each of the first 22 and third 26 parts, the first portion 16 is arranged above the second portion 18 along direction E, also called the thickness direction. The first 16 and second 18 portions, although woven simultaneously, are structurally independent, that is, they are not woven to each other, which allows for an arrangement of the first portions 16, forming a non-zero angle with the second portions 18 and the second part 24. The first 16 and second 18 portions of the first 22 and third 26 parts each have a thickness, along direction E, respectively epu, brA2, br3A, and ep32, such that e pii + e p ±2 = e i e p 3i e p 32 = e3- For the remainder, we will assume that the thicknesses of the first and second portions are identical for the first and third parts, that is to say that e pll = e p31 summer pl2 = e p32 Of course, it is possible that the thicknesses e and e3 are different, and also that the thicknesses e pll , e p31 , e pl2 summer p32are different from each other in pairs. The first portion 16 and the second portion 18 of the first part 22 are woven into the second part 24 at a transition from the first part 22 to the second part 24. Similarly, the first portion 16 and the second portion 18 of the third part 26 are woven into the second part 24 at a transition from the third part 26 to the second part 24. These transitions, indicated by two boxes A and B, correspond to an interlacing of the threads from the first portion 16 and the second portion 18 of the first part 22, to form the second part 24.

[0054] The fibrous structure 20 is characterized by the spacing between two weft planes along the warp direction C, which is greater in the second part 24 than in the first part 22 and the third part 26. Furthermore, the number of weft yarns is lower in the second part 24 than in the first part 22 and the third part 26. More specifically, the number of weft yarns per weft plane in the second part is lower than the number of weft yarns per weft plane in the first part. Similarly, the number of weft yarns per weft plane in the second part can be lower than the number of weft yarns per weft plane in the third part. This allows the warp-to-weft ratio of the first 22 and third 26 parts to be influenced relative to that of the second part 24, thus limiting the thickness of the second part 24 without trimming.The second part 24 of the fibrous structure 20 thus has a thickness such that e2< e and e2< e3.

[0055] Table 1 below illustrates an example of a fibrous structure 12 according to the prior art, comprising a first part and a second part comprising a first portion 16 and a second portion 18, according to the prior art, where the second part 14 has a thickness e2> e pl2 and in particular where e = e2.

[0056] [Table 1]

[0057]

[0058] This fibrous structure 12, produced according to the prior art, from 21 textile layers by a three-dimensional multilayer weaving of the fibrous structure 12, has a warp-to-weft ratio of 50 / 50 that is invariant in the different parts of the fibrous structure 12. In this case, the number of layers, warp planes, and weft planes of the second part 14 is equal to the sum, respectively, of the number of layers, warp planes, and weft planes of the first 16 and second 18 portions of the second part 14 (and of the third part, if applicable). The fibrous structure 20 according to the invention makes it possible to limit the thickness e2 of the second part 24, intended to form the bathtub, so that its thickness e2 is close to the thickness e pl2 of the second portion 18 of the first part 22 (and the third part 26 where applicable). In other words, e x, e2 and e3 can thus be different, and this without trimming. Table 2 illustrates a fibrous structure 20 according to a first embodiment of the invention, comprising a first part 22 and a second part 24 itself comprising a first 16 and a second 18 portion:

[0059] [Table 2]

[0060]

[0061] The thickness e2 of the second part 24 of this fibrous structure 20, once formed, is reduced to 4.1 mm, with parameters for the first 16 and second 18 portions of the first part 22 unchanged from those in Table 1 illustrating the prior art. To achieve this, the spacing between two weft planes along the warp direction is increased from 1.25 mm to 1.5 mm, so as to make it greater than the spacing between two consecutive weft planes in the first part 22, particularly in the first 16 and second 18 portions of the first part 22.Furthermore, the number of weft threads in the second part 24 is less than the sum of the weft thread numbers in the first part 22, i.e., the sum of the weft threads in the first 16 and second 18 portions of the first part 22, by locally disengaging weft threads at the transition A between the first 22 and second 24 parts, in order to achieve a warp-to-weft ratio close to the limit of 75 / 25. Thus, the combination of increasing the spacing between two consecutive weft planes and the local non-insertion of weft threads, so as to reduce the weft planes, unbalances the warp-to-weft ratio, in the illustrated example at 74 / 26. This makes it possible to reduce by 1.9 mm the thickness e2 of the second part 24 of the fibrous structure 20 intended to form the tub of the ring sector compared to the fibrous structure 12 of the prior art illustrated by table 2.Thus, in the second part 24 of the fibrous structure 20, the number of weft threads is less than the number of warp threads, at 9 and 21 respectively. For practical reasons, the imbalance in the warp-to-weft ratio is achieved by adjusting the spacing between two successive weft planes, and not the spacing between two successive warp planes. As a result, the spacing between two warp planes is identical between the first part 22 and the second part 24.

[0062] In the specific case not illustrated of weaving pieces at 90° to the orientation presented in this document, it is conceivable to play with the spacing between two successive warp planes while keeping the spacing between two successive weft planes constant.

[0063] Although the example illustrated here describes the particular situation with a fibrous structure 20 having a first 22 and second 24 part, the fibrous structure 20 may include a third part 26 identical to the first part 22 and woven to the second part 24 along the warp direction opposite to the first part 22.

[0064] Table 3 illustrates the characteristics of a fibrous structure 20 according to a second embodiment of the invention, comprising a first part 22 and a second part 24 itself comprising a first 16 and a second 18 portion:

[0065] [Table 3]

[0066]

[0067] In this structure 20, the warp-weft ratio is varied in the first 16 and second 18 portions of the first part 22, in order to reduce the number of textile layers subsequently woven in the second part 24.

[0068] Thus, in the second portion 18 of the first part 22, the number of weft planes is greater than the number of warp planes. In the first portion 16 of the first part 22, the number of weft planes is equal to 1.5 times the number of warp planes. The spacing between two successive weft planes in the first 16 and second 18 portions is reduced to 1 mm.

[0069] The modification of these parameters, unbalancing the warp-weft ratio of the first 16 and second 18 portions respectively at 41 / 59 and 35 / 65, combined with an increase in the spacing between two successive weft planes, therefore makes it possible to obtain, for a thickness of 2.1 mm and 4.1 mm respectively for the first 16 and second 18 portions of the conformed fibrous structure 20, a thickness e2 of the second part 24 equal to 4.2 mm.

[0070] In this example of fibrous structure 20, the number of weft yarns is greater than the number of warp yarns in the first portion 16 and in the second portion 18 of the first part 22 of the fibrous structure 20.

[0071] The invention also relates to a fibrous structure 22, the thickness e2 of the second part 24 of which is less than the thickness of the first part 22, that is to say, the sum of the thicknesses of the first 16 and second 18 portions. Table 4 illustrates a third embodiment of the invention:

[0072] [Table 4]

[0073]

[0074] Keeping the parameters of the first 16 and second 18 portion of the first part 22 of the fibrous structure 20 of the example in Table 3, the thickness of the second part 24 is further reduced, by changing the warp-weft ratio to 73 / 27 by reducing the number of frame planes of the second part 24 of the fibrous structure 20, from 16 to 7.

[0075] A thickness of 3.1 mm is then obtained for this second part 24 against 4.2 mm for the structure described in reference to table 3.

[0076] Thus, the invention also relates to the manufacturing process of fibrous structures 20 as described with reference to Tables 2 to 4. The manufacturing process of weaving a fibrous structure 20 according to the invention, thus includes a step consisting of reducing the spacing between two successive weft planes along the warp direction and reducing the number of weft yarns during a transition along the warp direction from a first part of the fibrous texture to a second part 24 of the fibrous texture 20 having a thickness greater than that of the first part 22.

[0077] The manufacturing process also includes a step of increasing the number of weft yarns and decreasing the spacing between two successive weft planes along the warp direction, during the transition in warp direction from the second part 24 of the fibrous texture 20 to the first part 22 of the fibrous texture 20.

[0078] The resulting fibrous structures 20 can then be used to manufacture a composite part, for example, a stator sector 12, as described above. Thus, the invention also relates to a method for manufacturing a composite material, comprising the following steps:

[0079] a) Obtain a fibrous structure 20 by means of the process as presented above; b) Shape the fibrous structure 20;

[0080] c) Obtaining a composite material by injecting or densifying a matrix inside the fibrous structure.

[0081] Step b) consists of obtaining a fibrous preform from the fibrous structure 20, intended to form the fibrous reinforcement of the composite part. This fibrous preform has a shape close to that of the composite part. Thus, in the example of a stator sector 12 as described previously, the woven fibrous structure 20 is shaped in a "Pi" configuration; that is, the first portions 16 of the first 22 and third 26 parts of the fibrous structure 20 are arranged to form an angle with the second portions 18 of the first 22 and third 26 parts and with the second part 24 (the latter three being substantially aligned). This is achieved using shaping tools, which maintain the preform in a shape close to that of the part to be manufactured.

[0082] The composite part is then obtained by densifying the fibrous preform, that is, by injecting a matrix inside the formed fibrous structure. The matrix can be a resin or, in the case of a so-called thermostructural composite material, a refractory material such as carbon or ceramic.

[0083] Matrix injection can be carried out for example by chemical vapor infiltration (CVI), by the process known by the English acronym PIP for Polymer Infiltration And Pyrolysis or any other process classically known for the design of CMC parts.

Claims

DEMANDS 1. A three-dimensionally woven, multilayer fibrous structure (20) having the same number of warp yarns woven at every level along the warp direction, the fibrous structure (20) comprising, in the warp direction, a first part (22) and a second part (24), the first part (22) having a thickness, measured in a direction perpendicular to the warp and weft directions, greater than that of the second part (24), characterized in that the spacing between two weft planes along the warp direction is greater in the second part than in the first part (22), and in that the number of weft yarns per weft plane of the second part is less than the number of weft yarns per weft plane of the first part, the first part (22) of the fibrous structure (20) comprising a first portion (16) and a second portion (18), the first portion (16) being arranged, along said perpendicular direction,above a second portion (18) and being structurally independent of the second portion (18), said first portion (16) and second portion (18) of the first part (22) being woven into the second part (24) at the level of a transition from the first part (22) to the second part (24).

2. Fibrous structure (20) according to claim 1, wherein the number of weft yarns is greater than the number of warp yarns in one and / or the other of the first portion (16) and the second portion (18).

3. Fibrous structure (20) according to claim 1 or 2, wherein, in the second part (24), the number of weft yarns is less than the number of warp yarns.

4. Fibrous structure (20) according to any one of claims 1 to 3, wherein the spacing between two warp planes is identical between the first part (22) and the second part (24).

5. Fibrous structure (20) according to any one of claims 1 to 3, wherein the spacing between two warp planes is different.

6. Fibrous structure (20) according to any one of claims 1 to 5, comprising a third part (26) identical to the first part (22) and woven to the second part (24) along the warp direction opposite the first part (22).

7. Method for manufacturing a fibrous structure (20) according to any one of claims 1 to 6, wherein during the transition in the warp direction from the first part (22) of the fibrous texture (20) to the second part (24) of the fibrous texture (20), the number of weft threads is decreased and the spacing between two successive weft planes along the warp direction is increased.

8. Method of manufacturing a fibrous structure (20) according to any one of claims 1 to 6, wherein during the warp direction transition of the second part (24) of the fibrous texture (20) to the first part (22) of the fibrous texture (20), the number of weft yarns is increased and the spacing between two successive weft planes along the warp direction is decreased.

9. A process for manufacturing a composite material, comprising the following steps: a) Obtaining a fibrous structure (20) by means of the process according to claim 7 or 8; b) Conform the fibrous structure (20); c) Obtaining a composite material by injecting a matrix inside the fibrous structure (20).