Fibrous preform fixed by the wrapping material

Abstract

The invention relates to a method for manufacturing a self-supporting fibrous preform (400) for manufacturing a part made of composite material, comprising: - the creation of a fibrous blank (100) by weaving a plurality of wrapped yarns, each wrapped yarn comprising a strand (10) and one or more wrapping yarns (12), the wrapping yarn(s) (12) being made of a wrapping material (21), - the shaping of the fibrous blank (100) in a shaping mold (5) and the diffusion of the wrapping material (21) from the wrapping yarns (12) so as to bind the strands (10) to each other, - the hardening of the wrapping material so as to obtain a fibrous preform (400) fixed by said wrapping material, - the removal of the fixed fibrous preform (400) of the shaping mold (5). Figure for the abbreviation: Fig. 1

Description

Title of the invention: Fibrous preform fixed by the wrapping material. Technical field

[0001] The present invention relates to the manufacture of parts made of composite material, and more particularly of parts made of composite material in which at least part of the fibrous reinforcement is formed by a fibrous preform. Previous technique

[0002] To obtain lightweight turbomachine parts with excellent thermomechanical properties, composite materials are commonly used. The use of composite materials helps optimize turbomachine performance, particularly by reducing the overall mass of the turbomachine, which contributes to lower fuel consumption and therefore a significant reduction in pollutant emissions. Furthermore, due to their superior resistance to high temperatures, ceramic matrix composite materials require less cooling. Since this cooling is traditionally drawn from the compressor, which impacts the turbomachine's efficiency, composite materials allow for further improvements in engine efficiency and a greater reduction in fuel consumption.

[0003] In particular, it is known to produce a fibrous blank by weaving, for example using a Jacquard loom. The fibrous blank is then shaped in a former to produce a fibrous preform, said fibrous preform being intended to form the fibrous reinforcement of the composite part to be obtained. The fibrous preform in the former is then consolidated. Consolidation can be carried out conventionally by gaseous infiltration, for example by chemical vapor infiltration (CVI).

[0004] Once consolidation is complete, the consolidated fibrous preform is removed from the conformer and then densified with a matrix in one or more steps. For example, densification can be carried out in a well-known manner by performing a powder infiltration step, for example according to the so-called "STM" process for "Slurry Transfer Molding", complemented by a liquid infiltration step of a composition comprising molten silicon, called "MI" for "Melt Infiltration".

[0005] The conformer used in such a process must be made of a material suitable for gaseous infiltration and often has a complex, multi-part architecture. Thus, such a conformer is difficult and expensive to manufacture. Furthermore, due to the conformer's complex architecture, the operation of shaping the fibrous blank within said conformer is delicate and time-consuming, and difficult to industrialize at high production rates. Description of the invention

[0006] To overcome the aforementioned drawbacks, the invention proposes using a shaping mold beforehand to shape the fiber blank into a fiber preform, the fiber preform then being placed in the former. This makes it possible to use an inexpensive shaping mold compatible with large-scale industrialization for shaping the fiber blank. Furthermore, since the fiber blank is already shaped into a fiber preform when placed in the former, the architecture of the former receiving the fiber preform can be simplified. Thus, the former used is less expensive and also allows for a higher production rate.

[0007] In order to allow the removal of the fibrous preform from the forming mold and its transport to the former without deformation of said fibrous preform, it is necessary that the fibrous preform be self-supporting. Indeed, the fibrous preform must retain its shape even when it is no longer supported by the forming mold.

[0008] To this end, the invention proposes a method for manufacturing a self-supporting fibrous preform for the manufacture of a part made of composite material comprising:

[0009] - the production of a fibrous blank by weaving a plurality of wrapped yarns, each wrapped yarn comprising a strand and one or more wrapping yarns wound around the strand, the wrapping yarn(s) being made of a wrapping material,

[0010] - shaping the fibrous blank in a shaping mold so as to to obtain a fibrous preform, then

[0011] - the diffusion of the wrapping material of the wrapping yarns in the fibrous preform so that the diffused wrapping material binds the strands together, then

[0012] - the hardening of the diffused wrapping material so as to obtain a preform fibrous material, frozen by the wrapping material,

[0013] - the removal of the fibrous preform fixed by the hardened wrapping material from the mold formatting.

[0014] Thus, the invention makes it possible to valorize the wrapping yarns used for the weaving operation in order to produce a self-supporting fibrous preform. Such a process makes it possible to use an inexpensive mold for shaping, and to facilitate the automation and mass production of composite material parts.

[0015] According to a particular embodiment of the invention, the covering threads are wound around the strands at a winding rate of between 140 turns and 325 turns per meter of strand.

[0016] Thus, such a winding ratio is a satisfactory compromise between a high winding ratio to have plenty of wrapping material to securely bind the strands without damaging them.

[0017] According to another particular embodiment of the invention, the shaping mold is made of metal or polymer.

[0018] Indeed, the invention makes it possible to use a forming mold made of a low-cost material, which does not need to be adapted for a gaseous infiltration operation. Therefore, the forming mold does not need, for example, to be made of graphite.

[0019] According to another particular embodiment of the invention, the covering material is soluble in water.

[0020] According to another particular embodiment of the invention, the diffusion of the covering material is carried out at least in part by partial dissolution of said covering material with a fluid.

[0021] Preferably, the fluid is water. Indeed, water is a simple and inexpensive fluid to use, and does not cause major damage to the fibers.

[0022] The diffusion of the covering material can be achieved entirely by partial dissolution of the covering material.

[0023] According to another particular embodiment of the invention, the hardening of the diffused wrapping material is achieved at least in part by evaporation of the fluid used for dissolution. Preferably, the fluid used is water.

[0024] According to another particular embodiment of the invention, the diffusion of the covering material is carried out at least in part by heating said covering material.

[0025] The diffusion of the covering material can be achieved entirely by heating the covering material.

[0026] According to another particular embodiment of the invention, the hardening of the diffused covering material is achieved at least in part by cooling said diffused covering material.

[0027] According to another particular embodiment of the invention, the wrapping material comprises polyvinyl alcohol.

[0028] The invention also proposes a method for manufacturing a consolidated fibrous preform comprising:

[0029] - the manufacture of a self-supporting fibrous preform according to the process as described previously,

[0030] - the arrangement of the self-supporting fibrous preform in a conformer, then

[0031] - the removal of the wrapping material from the fibrous preform,

[0032] - consolidation of the fibrous preform by gaseous infiltration.

[0033] Finally, the invention further proposes a method for manufacturing a part in composite material comprising the manufacture of a consolidated preform according to the method as described above, and further comprising the densification of the consolidated fibrous preform so as to fill the porosities of said consolidated fibrous preform with a matrix. Brief description of the drawings

[0034] [Fig.1] Fig.1 is a schematic perspective view of a fibrous blank comprising wrapping yarns.

[0035] [Fig.2] The [Fig.2] is a schematic cross-sectional view of the fibrous blank of the [Fig.1] being shaped in a shaping mold.

[0036] [Fig.3] The [Fig.3] is a schematic cross-sectional view of the impregnated fibrous blank of the [Fig.2] arranged in a shaping mold so as to obtain a fibrous preform partially impregnated by the diffused wrapping material.

[0037] [Fig.4] The [Fig.4] is a schematic cross-sectional view of a self-supporting fibrous preform obtained by hardening the diffused wrapping material of the [Fig.3].

[0038] [Fig.5] The [Fig.5] is a schematic cross-sectional view of the self-supporting fibrous preform of the [Fig.4] arranged in a conformer.

[0039] [Fig.6] The [Fig.6] is a schematic cross-sectional view of the self-supporting fibrous preform of the [Fig.5] after removal of the wrapping material. Description of the implementation methods

[0040] The manufacturing process according to the invention comprises the production of a fibrous blank by weaving. [Fig. 1] illustrates a schematic example of a fibrous blank 100 thus obtained.

[0041] The fibrous blank 100 can be obtained in a well-known manner by weaving on a Jacquard-type loom on which a bundle of warp yarns is arranged in a plurality of layers of several hundred yarns each, the warp yarns being joined by weft yarns. The fibrous blank 100 is preferably woven in a single piece, in order to improve its mechanical properties.

[0042] The fibrous blank 100 can be produced in one piece by three-dimensional weaving. By "three-dimensional weaving," we mean here a weaving method by in which at least some of the warp yarns bind weft yarns across several weft layers. A reversal of roles between warp and weft is possible. A fibrous blank produced by three-dimensional weaving is considered to include another type of weave on its surface, for example, two-dimensional weaving, in order to improve its surface finish.

[0043] Preferably, the three-dimensional weave used is an "interlock" weave. By "interlock" weave, we mean a weave structure in which each layer of weft yarns connects several layers of warp yarns, with all the yarns in the same weft column having the same movement in the plane of the weave.

[0044] Other known types of three-dimensional weaving may be used, such as those described in document WO 2006 / 136755.

[0045] The fibrous blank 100 may include one or more unbonds. The fibrous blank 100 may have a wide variety of shapes.

[0046] According to the invention, at least some of the yarns used for weaving the fibrous blank 100 are wrapped yarns. For example, only the warp yarns may be wrapped yarns, or only the weft yarns may be wrapped yarns. All of the yarns used for weaving the fibrous blank 100 may also be wrapped yarns.

[0047] A wrapped yarn comprises a strand 10 around which one or more wrapping yarns 12 are wound, as illustrated in [Fig. 1]. The wrapping of the strand 10 is carried out in a well-known manner, for example, using a wrapping machine called a wrapping machine. Setting up the wrapping machine requires the general knowledge and expertise of a person skilled in the art. The strand 10 is preferably straight when wrapped by the wrapping yarns 12.

[0048] The strand 10 is made of a strand material 11. In particular, the strand 10 is conventionally formed from one or more fibers of strand material 11. The strand material 11 is conventionally a refractory material. The strand material 11 may be a ceramic. The invention is particularly relevant when the strand material 11 is silicon carbide. The strand material 11 may also be an oxide. The strand material 11 may be one of the following materials: alumina, mullite, silica, an aluminosilicate, a borosilicate, carbon, or a mixture of several of these materials. The strand material 11 may optionally be glass, carbon, or Kevlar.

[0049] The covering threads 12 protect the strands 10 during weaving. During weaving, the strands are subjected to significant stress, which can cause some uncovered strands to break. Furthermore, the uncovered strands can be contaminated by metallic particles from the machine, which can lead to defects during matrix densification, for example... Silicon carbide outgrowths. The wrapping process thus reduces weaving defects.

[0050] The wrapping threads 12 are made of wrapping material 21. The wrapping material 21 is a fugitive material. By "fugitive material," we mean any material that can be removed without leaving any residue on the strand 10 and without damaging the fibers of said strand 10. In particular, the wrapping material 21 may be a water-soluble material. According to a preferred embodiment of the invention, the wrapping material 21 may comprise polyvinyl alcohol (PVA). The wrapping material 21 may also be a polymer that can be removed by heat treatment, such as polyvinyl acetate or polyethylene.

[0051] Preferably, the winding ratio of each of the covering yarns 12 is between 140 turns and 325 turns per meter of strand 10. Such values ​​for the winding ratio ensure a satisfactory compromise between, on the one hand, a winding ratio sufficient to have enough covering material 21 for the implementation of the invention, and on the other hand, a winding ratio not too high to prevent the covered yarns from being too stiff to be woven.

[0052] In order to facilitate understanding of the invention, the spacing between the strands 10 is deliberately exaggerated in the figures and the weaving is simplified.

[0053] The fibrous blank 100 is then shaped in a shaping mold 5 so as to obtain a fibrous preform 200 as illustrated in [Fig.2].

[0054] The shaping mold 5 can for example comprise two plates 51 and 52 between which the fibrous blank 100 is placed to obtain the fibrous preform 200. The shaping mold 5 is conventionally made of metal.

[0055] The shaping of the fibrous blank 100 is carried out while the covering material 21 is still in the form of covering yarns 12. This gives the fibrous preform 200 comprising the covering yarns 12.

[0056] The diffusion step of the wrapping material 21 is carried out after the shaping of the fibrous blank 100 in the shaping mold 5. Thus, the diffusion step of the wrapping material 21 is carried out while the fibrous preform 200 is arranged in the shaping mold 5. Therefore, the diffusion step of the wrapping material 21 is carried out on the fibrous preform 200 comprising the wrapping yarns 12.

[0057] The wrapping material 21 is diffused to obtain a fibrous preform 300 impregnated by the partially diffused wrapping material 22, as illustrated in [Fig. 3]. The diffusion of the wrapping material can be achieved, in particular, by partial dissolution or melting of the wrapping material, or by both. The diffusion of the wrapping material here corresponds to at least a partial transfer of the wrapping material from the wrapping yarns throughout the entire volume of the fibrous preform.

[0058] The diffusion step of the wrapping material 21 can be carried out at least in part by introducing a fluid into the fibrous preform, said fluid being configured to partially dissolve the wrapping material 21, while retaining said wrapping material inside the fibrous preform. For example, the diffusion step of the wrapping material 21 can be carried out by wetting the fibrous preform comprising the wrapping yarns 12. In this configuration, the application of water partially dissolves the wrapping material 21, while retaining said wrapping material inside the fibrous preform. The wrapping material 21 can also be a thermoplastic material, the diffusion step of the wrapping material 21 being carried out at least in part by heating the wrapping material and retaining it inside the fibrous preform.The diffusion step of the wrapping material 21 can be carried out both by introducing a fluid into the fibrous preform, said fluid being configured to partially dissolve the wrapping material 21, and by heating the wrapping material 21.

[0059] The wrapping material 21 of the wrapping yarns 12 is treated to allow at least partial diffusion within the fiber blank. This treatment allows the diffusion of said wrapping material 21 between the strands 10. The diffusion of the wrapping material 21 allows the strands 10 to be bonded to one another. The strands 10 are bonded to one another by the diffused wrapping material 22.

[0060] A fibrous preform 300 impregnated with the diffused wrapping material 22 is obtained, as illustrated in [Fig. 3]. The diffused wrapping material 22 is not fixed. The diffused wrapping material 22 is not solid.

[0061] The diffused wrapping material 22 is then hardened, as illustrated in [Fig. 4]. Hardening can be achieved at least partially by evaporation of the fluid used for dissolution. In particular, hardening can be achieved at least partially by evaporation of the water used for humidification. Hardening can also be achieved at least partially by cooling.

[0062] A self-supporting fibrous preform 400 is thus obtained. The self-supporting fibrous preform 400 comprises the strands 10 bonded and held together by the hardened wrapping material 21, as illustrated in [Fig. 4]. The self-supporting fibrous preform 400 is then removed from the forming mold 5. Since the fibrous preform 400 is self-supporting, it retains its shape even when it is no longer held in shape by the forming mold 5. The self-supporting fibrous preform 400 is intended to be consolidated.

[0063] For this purpose, the self-supporting fibrous preform 400 is placed in a former 6, as illustrated in [Fig. 5]. Since the fibrous preform 400 is self-supporting, it can be easily moved into the former 6.

[0064] When the self-supporting fibrous preform 400 is placed in the former 6, the wrapping material 21 present in said self-supporting fibrous preform 400 is removed.

[0065] If the wrapping material 21 is soluble in water, it can be dissolved in water. Preferably, the water is at a temperature above 50°C, preferably above 80°C. Such a method of removal is particularly suitable for a wrapping material 21 comprising polyvinyl alcohol (PVA).

[0066] The wrapping material 21 can also be removed by heat treatment, for example by pyrolysis. Such a removal method can be carried out simultaneously with the preparation for consolidation. Thus, the temperature rise required for consolidation can be used to remove the wrapping material 21.

[0067] A fibrous preform 500 devoid of wrapping material is thus obtained, arranged in the conformer 6, as illustrated in [Fig. 6]. Thus, the fibrous preform 500 devoid of wrapping material exhibits porosities 30 between the strands 10.

[0068] The fibrous preform 500, devoid of wrapping material, can thus be consolidated. In particular, the fibrous preform 500, devoid of wrapping material, can be consolidated by gaseous means, for example by chemical infiltration in the gas phase, known as "CVI".

[0069] The former 6 can be formed by two plates 61 and 62 between which is placed the fibrous preform 500, devoid of wrapping material, as in the example illustrated in Figures 5 and 6. The former 6 can comprise a plurality of retaining elements that define gas flow channels between them. An example of a former of this type is described in particular in document FR 3130852 AL. The use of another type of former does not, of course, depart from the scope of the invention.

[0070] As is well known, the fibrous preform 500 arranged in the former 6 can be placed in a chemical vapor infiltration system. The chemical vapor infiltration system may include an enclosure defining a reaction chamber equipped with a gas inlet duct that may open into a homogenization zone for homogenizing the gas(s) before their diffusion into the reaction chamber. The reaction chamber may include a support on which the fibrous preform 500 loaded in the former 6 is intended to be deposited. Residual gases can be extracted at the top of the system via a discharge duct connected to suction means. Heating is provided, for example, by a susceptor.

[0071] In order to carry out chemical vapor infiltration, one or more reactive gases are introduced into the reaction chamber. The consolidation of the preform 500 is ensured, in a manner well known per se, by deposition within it of the produced material. by decomposition of the precursor(s) contained in the reactive gas(s) diffusing within the accessible internal pores 30 of the preform 500. The reactive gas(s) may contain one or more precursors of an interphase material or one or more precursors of a ceramic matrix. The interphase or ceramic matrix precursor material is intended to coat the strands of the fibrous preform 500. For example, as an interphase precursor, the reactive gas(s) may contain one or more precursors of boron nitride (BN). For example, as a ceramic matrix precursor, the reactive gas(s) may contain one or more precursors of silicon carbide (SiC). Methyltrichlorosilane (MTS) may be used as a precursor of silicon carbide (SiC) in a manner that is well known per se.

[0072] Chemical vapor infiltration allows the consolidation of the fibrous preform 500. Chemical vapor infiltration thus makes it possible to obtain a consolidated fibrous preform, which is self-supporting.

[0073] The fibrous preform 500 can be subjected to several chemical infiltrations in the gas phase, for example to a first chemical infiltration in the gas phase to deposit an interphase and then to a second chemical infiltration in the gas phase to deposit ceramic matrix material.

[0074] Consolidation can allow the formation of a satisfactory matrix within the pores of the fibrous preform, enabling the production of a final part made of composite material. However, generally, after consolidation of the fibrous preform, it is densified by means of a matrix.

[0075] When the fibrous preform is consolidated, it can be densified by a matrix to obtain the final composite material part.

[0076] For example, a powder infiltration step can be carried out in a well-known manner. Powder infiltration can be carried out in a well-known manner using a slurry, for example according to the so-called "STM" process for "Slurry Transfer Molding". This step allows a portion of the matrix to be rapidly formed within the pores of the fibrous preform.

[0077] An additional liquid infiltration step, called "MI" for "Melt Infiltration," can also be carried out. This additional liquid infiltration step is preferably carried out after the powder infiltration step. This additional step is conventionally carried out by introducing a composition comprising molten silicon into the remaining pores of the fibrous preform to obtain the final matrix.

[0078] This yields a composite material part whose fibrous reinforcement is formed by the fibrous preform comprising the strands 10. The resulting composite material part is preferably ceramic matrix. In particular, the resulting composite material part is preferably of the SiC / SiC type.

[0079] The composite material part thus obtained can be a turbomachine part, for example a turbomachine blade or an aircraft casing.

Claims

Demands

1. A method for manufacturing a self-supporting fibrous preform (300) for manufacturing a part made of composite material, comprising: - producing a fibrous blank (100) by weaving a plurality of wrapped yarns, each wrapped yarn comprising a strand (10) and one or more wrapping yarns (12) wound around the strand (10), the wrapping yarn(s) (12) being made of a wrapping material (21), - shaping the fibrous blank in a shaping mold (5) so as to obtain a fibrous preform (200), then - diffusing the wrapping material (21) from the wrapping yarns (12) into the fibrous preform (200) so that said diffused wrapping material (22) binds the strands (10) together, then - hardening the diffused wrapping material (22) so as to obtain a fixed fibrous preform (400) by the wrapping material (21),- the removal of the fixed fibrous preform (400) by the hardened wrapping material (22) from the forming mold (5).

2. A manufacturing method according to claim 1, wherein the covering yarns (12) are wound around the strands (10) at a winding rate of between 140 turns and 325 turns per meter of strand (10).

3. A manufacturing method according to claim 1 or 2, wherein the shaping mold (5) is made of metal or polymer.

4. A manufacturing method according to any one of claims 1 to 3, wherein the wrapping material (21) is soluble in water.

5. A manufacturing method according to any one of claims 1 to 4, wherein the diffusion of the wrapping material (21) is carried out at least in part by partial dissolution of said wrapping material with a fluid.

6. A manufacturing method according to claim 5, wherein the hardening of the diffused wrapping material (22) is achieved at least in part by evaporation of the fluid used for dissolution.

7. A manufacturing method according to any one of claims 1 to 6, wherein the diffusion of the wrapping material (21) is carried out at least in part by heating said wrapping material.

8. A manufacturing method according to claim 7, wherein the hardening of the diffused wrapping material (22) is carried out at least in part by cooling said diffused wrapping material.

9. A manufacturing method according to any one of claims 1 to 8, wherein the wrapping material (21) comprises polyvinyl alcohol.

10. A method for manufacturing a consolidated fibrous preform comprising: - manufacturing a self-supporting fibrous preform (400) according to any one of claims 1 to 9, - arranging the self-supporting fibrous preform (400) in a former (6), then - removing the wrapping material (21) from the fibrous preform (400), - consolidating the fibrous preform (500) by gaseous infiltration.

11. A method for manufacturing a part made of composite material comprising manufacturing a consolidated preform according to claim 10, and further comprising densifying the consolidated fibrous preform so as to fill the porosities of said consolidated fibrous preform with a matrix.

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