阅读说明：本技术 通过将粉末注入纤维增强件并由复合过滤层排出，制备由复合材料制成的部件的方法 (Method for producing a part made of composite material by injecting powder into a fibrous reinforcement and discharging it from a composite filter layer ) 是由 E·菲利普 M·D·布尼亚 A·科莱拉姆伯格 P·卡米纳提 于 2018-12-21 设计创作，主要内容包括：一种复合材料部件的制备方法,其包括以下步骤：由耐火陶瓷纤维形成纤维织构体(10)；在模具(110)中放置纤维织构体(10),在纤维织构体和排出端口(112)之间插入过滤层(130),该过滤层(130)包括部分致密化的纤维结构；将含有耐火陶瓷颗粒(1500)的浆料(150)加压注入纤维织构体(10)；通过过滤层(130)排出已经通过纤维织构体(10)的浆料的溶剂,并且通过过滤层(130)将耐火陶瓷颗粒的粉末保留在该织构体内,从而获得至少包括填充有耐火陶瓷颗粒(1500)的纤维织构体(10)和过滤层(130)的纤维预制件；对存在于预制件的纤维织构体(10)中的耐火陶瓷颗粒(1500)进行热处理以形成复合材料部件,该复合材料部件至少包括由耐火陶瓷基质致密化的纤维织构体和过滤层。(A method of making a composite part comprising the steps of: forming a fibrous structure (10) from refractory ceramic fibers; placing a fiber structure (10) in a mold (110), inserting a filter layer (130) between the fiber structure and an exit port (112), the filter layer (130) comprising a partially densified fiber structure; injecting a slurry (150) containing refractory ceramic particles (1500) into the fibrous structure (10) under pressure; discharging the solvent of the slurry having passed through the fibrous structure (10) through the filter layer (130) and retaining the powder of refractory ceramic particles within the structure through the filter layer (130), thereby obtaining a fibrous preform comprising at least the fibrous structure (10) filled with refractory ceramic particles (1500) and the filter layer (130); refractory ceramic particles (1500) present in a fibrous structure (10) of a preform are heat treated to form a composite part comprising at least the fibrous structure densified by a refractory ceramic matrix and a filter layer.)

1. A method of making a composite part comprising the steps of:

forming a fibrous structure (10) from refractory ceramic fibres,

-placing a fibrous structure (10) in a mould (110) having at least one injection port (121) and at least one discharge port (112), interposing a filter layer (130) between the fibrous structure and the at least one discharge port, the filter layer (130) comprising a partially densified fibrous structure,

injecting a slurry (150) containing refractory ceramic particles (1500) into the fibrous structure (10) under pressure,

-draining the solvent of the slurry having passed through the fibrous structure (10) through the filter layer (130) and retaining the powder of refractory ceramic particles within said structure through the filter layer (130), thereby obtaining a fibrous preform comprising at least the fibrous structure (10) filled with refractory ceramic particles (1500) and the filter layer (130), the solvent being drained through said at least one drain port (112),

-heat treating refractory ceramic particles (1500) present in a fibrous structure (10) of the preform to form a composite part comprising at least said fibrous structure densified by a refractory ceramic matrix and a filter layer.

2. The method of claim 1, wherein the filter layer (130) comprises refractory ceramic fibers having the same properties as the refractory ceramic fibers of the fibrous structure (10), and wherein the filter layer is partially densified with pre-sintered refractory ceramic particles having the same properties as the refractory ceramic particles (1500) deposited in the fibrous structure.

3. A method according to claim 1 or 2, wherein the filter layer (130) has an average pore size of between 0.1 μm and 20 μm and an average volume porosity of less than 50%.

4. A method as claimed in any one of claims 1 to 3, wherein the fibrous structure (10) comprises a fibrous structure obtained by two-dimensional weaving or three-dimensional or multi-layer weaving or automatic placement of unidirectional fibres.

5. A method according to any one of claims 1 to 3, wherein the fibrous texture corresponds to a fibrous skin (400) placed opposite one face (300a) of the porous structure (300), the fibrous skin and the porous structure being placed in a mould (210) with a filter layer (230) interposed between them, the composite part obtained comprising a fibrous skin densified by a refractory ceramic matrix, a filter layer and a porous structure.

6. A method according to any one of claims 1 to 3, wherein the fibrous texture corresponds to a fibrous skin placed opposite a face of a plurality of bubble-like structures, the fibrous skin and bubble-like structures being placed in a mould, and a filter layer being interposed between the fibrous skin and the bubble-like structures, the resulting composite component comprising a fibrous skin densified by a refractory ceramic matrix, the filter layer and the bubble-like structures.

7. A method according to any one of claims 1 to 3, wherein the mould has a circular or frustoconical rotating geometry, the fibrous structure and the filter layer being shaped into the circular or frustoconical rotating geometry when placed in the mould.

8. A method according to any one of claims 1 to 7, wherein the yarns of the fibrous structure are yarns formed from fibres consisting of one or more of the following materials: alumina, mullite, silica, aluminosilicate, borosilicate, silicon carbide, and carbon.

9. The method of any one of claims 1 to 8, wherein the refractory ceramic particles are made of a material selected from the group consisting of: alumina, mullite, silica, aluminosilicates, aluminophosphates, zirconia, carbides, borides, silicides and nitrides or mixtures of several of these materials.

10. Composite part obtained by the method according to any one of claims 1 to 9, characterized in that it constitutes the rear body of an aircraft engine, a combustion chamber or a crankcase.

Technical Field

The invention relates to a method for manufacturing a part made of thermostructural composite material, in particular of the oxide/oxide type or Ceramic Matrix Composite (CMC), i.e. comprising a fibrous reinforcement formed of fibres of refractory ceramic material densified by a matrix also made of refractory ceramic material.

Background

Parts made of oxide/oxide composites are generally manufactured by: in the mould a plurality of fibrous layers are laid, which layers are made of refractory oxide fibres, each layer being impregnated beforehand with a slurry filled with refractory oxide particles. The assembly of layers thus arranged is then compacted by means of a counter-convex mould or a vacuum tarpaulin and channels in an autoclave. The thus obtained filled preform is then subjected to a sintering or ceramifying heat treatment, so as to form a refractory oxide matrix in the preform and obtain a part made of an oxide/oxide composite. The technique may also be used to fabricate carbon-based Ceramic Matrix Composite (CMC) components. In this case, the fibre layer is made of silicon carbide (SiC) or carbon fibres and is filled with carbides (for example SiC), borides (for example TiB)₂) Silicide (e.g. MoSi)₂) Or nitride (e.g. Si)₃N₄) The slurry of particles is impregnated.

Another solution for manufacturing parts made of oxide/oxide composite or CMC material by liquid route comprises the following steps: the fibrous structure is impregnated with a slurry, for example with a slurry filled with alumina particles in the case of an oxide/oxide composite, or with a slurry filled with silicon carbide (SiC) particles in the case of a CMC material. The impregnation step is carried out by injecting a filling Slurry (Slurry Transfer molding, or STM) under pressure into the fibrous texture. In this case, the liquid phase of the slurry must be drained or filtered in order to obtain an optimal filling of the residual porosity present in the fibrous structure with the solid filler. Such a process is described in document WO 2016/102839. It is therefore necessary to use a filter element interposed between the fibrous structure and the portion of the mould from which the solvent of the slurry is extracted. The filter element may be formed from a rigid piece of porous material that must be separated from the fibrous texture when the fibrous texture is removed from the mold after the filling slurry is injected and the solvent is filtered.

The use of such filter elements can cause difficulties. In practice, it can be difficult to remove it from the fibrous texture and can lead to degradation of the infused fibrous texture. Furthermore, in the case of fiber structures having complex geometries, filter elements that accommodate both mold geometry and fiber structures may be difficult to design.

Disclosure of Invention

The aim of the present invention is to improve the above drawbacks and to propose a solution that facilitates the production of parts made of Ceramic Matrix Composites (CMC), oxides, carbides or carbon-based composites by injecting a filler slurry in a fibrous texture.

To this end, the invention provides a method of manufacturing a composite part, the method comprising the steps of:

forming a fibrous structure from refractory ceramic fibres,

placing a fibrous structure in a mould having at least one injection port and at least one discharge port, inserting a filter layer between the fibrous structure and the at least one discharge port, the filter layer comprising a partially densified fibrous structure,

injecting a slurry containing refractory ceramic particles under pressure into the fibrous structure,

discharging the solvent of the slurry that has passed through the fibrous structure through the filter layer and retaining the refractory ceramic particles in said structure through the filter layer, thereby obtaining a fibrous preform comprising at least the fibrous structure filled with refractory ceramic particles and the filter layer, the solvent being discharged through said at least one discharge port,

-heat treating the refractory ceramic particles present in the fibrous structure of the preform to form a composite part comprising at least said fibrous structure densified by the refractory ceramic matrix and the filter layer.

Thus, by using a filtration layer as an integral part of the final composite component, the problem of removing the filter elements used in the prior art is eliminated. Furthermore, the filter layer is not rigid and can be shaped into different geometries, which facilitates the production of composite parts having complex shapes.

According to a particular feature of the method according to the invention, the filter layer contains refractory ceramic fibers having the same properties as the refractory ceramic fibers of the fibrous structure, and the filter layer is partially densified by presintered refractory ceramic particles having the same properties as the refractory ceramic particles deposited in the fibrous structure.

According to another particular feature of the method of the invention, the filtering layer has a mean pore size comprised between 0.1 μm and 20 μm and a mean volume porosity of less than 50%.

According to another particular feature of the method according to the invention, the fibrous texture comprises a fibrous structure obtained by two-dimensional weaving or three-dimensional (or multi-layer) weaving or automatic laying of unidirectional fibres.

According to another particular feature of the method according to the invention, the fibrous texture corresponds to a fibrous skin placed opposite one face of the porous or gas-filled structure, the fibrous skin and the porous structure being placed in a mould, and a filter layer being interposed between said fibrous skin and said porous structure, the composite part obtained comprising a fibrous skin densified by a refractory ceramic matrix, a filter layer and a porous structure.

According to another particular feature of the method according to the invention, the fibrous texture corresponds to a fibrous skin placed opposite the face of the plurality of bubbles, the fibrous skin and the bubbles being placed in a mould, and a filter layer being interposed between said fibrous skin and said bubbles, the composite part obtained comprising a fibrous skin densified by a refractory ceramic matrix, a filter layer and a bubble.

According to another particular feature of the method according to the invention, the mould has a circular or frustoconical rotating geometry, the fibrous structure and the filter layer being shaped according to the circular or frustoconical rotating geometry when placed in the mould. In this case, the composite part obtained may constitute, in particular, the rear body of an aircraft engine, a combustion chamber or a crankcase.

The yarns of the preform may be yarns formed from fibres composed of one or more of the following materials: alumina, mullite, silica, aluminosilicate, borosilicate, silicon carbide, and carbon.

The refractory ceramic particles may be made of a material selected from the group consisting of: alumina, mullite, silica, aluminosilicates, aluminophosphates, zirconia, carbides, borides, silicides and nitrides or mixtures of several of these materials.

Drawings

Further characteristics and advantages of the invention will become apparent from the following description of a particular embodiment of the invention, given by way of non-limiting example, with reference to the accompanying drawings, in which:

figure 1 is a schematic exploded perspective view of a tool according to an embodiment of the invention,

FIG. 2 is a schematic cross-sectional view showing the tool of FIG. 1 closed by the fibrous structure and the filter layer located therein,

FIG. 3 is a schematic cross-sectional view showing the step of impregnating a fibrous structure with a slurry filled into the tool of FIG. 2 according to one embodiment of the present invention,

FIG. 4 is a schematic cross-sectional view showing the fiber structure of FIG. 3 filled with refractory ceramic particles,

figure 5 is a schematic exploded perspective view of a tool according to another embodiment of the invention,

FIG. 6 is a schematic cross-sectional view showing the tool of FIG. 5 closed by a fibrous skin, filter layer and honeycomb structure located therein,

fig. 7A to 7C show the manufacture of an expandable fibrous structure intended to form a honeycomb structure;

FIGS. 8A to 8C show the manufacture of another expandable fibrous structure forming a honeycomb structure;

FIG. 9 is a schematic cross-sectional view showing the step of impregnating the fibrous skin with slurry filled into the tool of FIG. 6 according to one embodiment of the present invention,

FIG. 10 is a schematic cross-sectional view showing the fiber skin of FIG. 9 filled with refractory ceramic particles,

fig. 11 is a schematic perspective view showing the resulting preform.

Detailed Description

The method according to the invention for manufacturing a part made of composite material, in particular of CMC type, starts with the manufacture of a fibrous fabric intended to form the reinforcement of the part.

The fiber fabric is produced by weaving in a known manner with a Jacquard type loom (Jacquard type loom) on which a bundle of warp threads or strands is arranged in layers, the warp threads being connected by weft threads and vice versa. The fiber structure may be realized by stacking layers or plies obtained by two-dimensional (2D) weaving. The fibrous texture can also be produced directly in one piece by three-dimensional (3D) weaving. "two-dimensional weaving" is a traditional weaving method by which each weft yarn passes from one side of the yarn of a single warp layer to the other, and vice versa. The method of the invention is particularly suitable for allowing the introduction of a filling slurry in a 2D fiber texture, i.e. a texture obtained by stacking 2D layers or plies having a significant thickness, i.e. a 2D fiber structure having a thickness of at least 0.5mm, preferably at least 1 mm.

"three-dimensional weaving" or "3D weaving" or "multilayer weaving" means a weaving method by which at least some of the weft yarns bind together the warp yarns of several layers of warp yarns in a weaving pattern, which, conversely, may also correspond to a weaving that may be chosen in particular from: interlocking (interlock) weaving, multi-weft (multi-warp) weaving, multi-satin (multi-satin) weaving, and multi-twill (multi-twill) weaving.

The term "interlocking weave" as used herein refers to a 3D weave in which each layer of warp yarns connects several layers of weft yarns, while all yarns of the same warp column have the same motion in the weaving plane.

The term "multiple plain weave" as used herein refers to a 3D weave using multiple layers of weft yarns, each layer having a basic weave (basic weave) equivalent to a conventional plain weave, but with some points in the weave that tie the weft yarn layers together.

The term "multiple satin weave" as used herein refers to a 3D weave using multiple layers of weft yarns, the basic weave of each layer being equivalent to a conventional satin weave, but certain points in the weave tie the layers of weft yarns together.

The term "multi-twill weave" as used herein refers to a 3D weave using multiple layers of weft yarns, the basic weave of each layer being identical to a conventional twill weave, but with certain points in the weave that bind the layers of weft yarns together.

3D textures have a complex geometry in which it is difficult to introduce and uniformly distribute suspended solid particles. The method of the present invention is also well suited for introducing a filler slurry into a 3D woven fibrous structure.

The fibrous texture may also be made from a Unidirectional (UD) layer or web, which is shaped as described in documents US9102571 or US 2015/328799.

The yarns used for weaving the fibrous structure intended to form the fibrous reinforcement of the composite component may in particular be made of refractory ceramic fibres made of one of the following materials: alumina, mullite, silica, aluminosilicate, borosilicate, silicon carbide, carbon or a mixture of several of these materials.

After the fibrous texture is produced, it is placed in a mold containing a filter layer according to the present invention, which allows the fibrous texture to be densified with refractory ceramic particles, as described below.

According to a first example shown in fig. 1 and 2, a fiber texture 10 is placed in a tool 100. In the example described here, the fibrous structure 10 is made of Nextel 610 according to one of the techniques described above (UD or 2D layer stacking or 3D weaving)^TMAlumina yarn. The fiber structure 10 is intended here to form a fiber reinforcement of a component made of an oxide/oxide composite material.

The tool 100 is comprised of a die 110 and a counter die 120. The mold 110 includes a bottom 111 having a channel 112. The mold 110 also includes sidewalls 113 that form a mold cavity 114 with the bottom 111. In the example shown, the tool 100 (in which the fiber structure 10 is present) is closed at its lower part by a die 110 and at its upper part by a counter die 120, which counter die 120 forms a lid closing the tool 100. The die 110 and the counter die 120 are used for dimensioning the preform and thus the obtained part and for adjusting the fibre content in the obtained part.

The counter mould 120 has a plurality of injection ports 121 through which a liquid filled with refractory ceramic particles is intended to be injected to penetrate the pores of the fibrous structure 10 through the first face 10a of the fibrous structure 10. In the example shown in fig. 1 and 2, the filling liquid is intended to be injected through a plurality of injection ports 121 open in different areas of the mold cavity. However, it is not beyond the scope of the present invention when the liquid is injected through a single injection port.

The die 110 in turn has a single liquid channel 112. Of course, it is not beyond the scope of the invention when a plurality of outlet openings are implemented.

According to the invention, a filter layer 130 is inserted between the fibrous structure 10 and the bottom 111 of the mold 110 comprising the openings 112. The filter layer according to the invention corresponds to a fibrous structure obtained by depositing Unidirectional (UD), two-dimensional (2D) or three-dimensional (3D) knitted refractory ceramic fiber yarns made of at least one of the following materials: alumina, mullite, silica, aluminosilicate, borosilicate, silicon carbide, carbon or a mixture of several of these materials. The filter layer is preferably made of refractory ceramic fibers having the same properties as the refractory ceramic fibers of the fibrous structure. The thickness of the filter layer is preferably 0.1mm to 1 mm.

In the example described here, the filter layer 130 corresponds to the filter layer formed by Nextel 610^TMA 2D fabric layer made of alumina yarn.

According to the invention, the filtering layer is partially densified to form a network of pores of a given size in the layer, which allows the filtrate of the slurry (i.e. its liquid phase) to pass through, while retaining the refractory ceramic particles present in the injected slurry.

As an example, the filter layer may have an average pore size of between 0.1 μm and 20 μm and an average volume porosity of less than 50% after being partially densified.

The fibrous structure intended to form the filtration layer may be partially densified by several methods. In particular, the fibrous structure may be pre-impregnated or impregnated with a slurry filled with refractory particles. In this case, the porosity is adjusted by adjusting the densification rate in the filter layer after the particle pre-sintering by controlling the particle size, the packing ratio, and the binder in the slurry. The filtration layer may also be obtained by injecting a slurry filled with refractory particles into the fibrous structure, the initially introduced particles controlling the stack thickness and thus the final matrix volume ratio (Tvm). A coating or quenching process may also be used to densify the fibrous texture portion intended to form the filtration layer.

In the example described here, the filter layer 130 is made of a 2D fabric of alumina yarns impregnated with a slurry filled with 25% by volume of alumina particles that have been pre-sintered to partially densify the filter layer.

The filter layer 130 allows the solvent in the slurry to drain from the fibrous structure 10 and out through the outlet cells 112 due to the application of a pressure gradient between the outlet cells 112 and the injection port 121.

Before injecting the slurry into the fibrous structure 10, compaction pressure may be applied by clamping the mold or by a press to compact the fibrous structure 10 between the mold 110 and the counter mold 120, and may be maintained during the injection process. Compaction pressure may also be applied by the compacting liquid through the membrane, such as in the Polyflex process.

Optionally, the compaction pressure may be applied and maintained after the filling liquid injection is initiated. The application of compaction pressure may be used to compact the texture body to help drain liquid and achieve a target thickness of the fibrous preform without damaging the preform.

In the examples described herein, the filling liquid is a slurry containing refractory ceramic particles. Fig. 3 shows the configuration obtained during injection of the slurry 150 and removal of the liquid medium from the slurry. The slurry 150 is injected through the injection port 121 under pressure to penetrate the fibrous structure 10 through the first face 10a of the fibrous structure 10. The refractory ceramic particles 1500 present in the slurry 150 are intended to allow the formation of a refractory ceramic matrix in the pores of the fibrous structure 10. In one example, the refractory ceramic matrix may be a refractory oxide matrix.

The slurry may be, for example, a suspension of alumina powder in water. The average particle size (D50) of the alumina powder may be between 0.1 μm and 2 μm. The alumina powder used may be an alpha-alumina powder.

More generally, the slurry may be a suspension containing refractory ceramic particles having an average particle size between 0.1 μm and 10 μm. The volume content of the particles in the slurry prior to injection may be between 5% and 50%. The refractory ceramic particles may comprise a material selected from the group consisting of: alumina, mullite, silica, aluminosilicates, aluminophosphates, zirconia, carbides, borides, silicides and nitrides or precursors of one or more of these materials. Depending on their basic composition, the refractory ceramic particles may additionally be mixed with alumina particles, zirconia particles, aluminosilicate particles, rare earth oxide particles, rare earth silicate particles (which may be used, for example, for environmental barriers or thermal barriers), or any other filler (such as carbon black, graphite, or silicon carbide) for functionalizing the composite part obtained.

The solvent for the slurry may for example comprise an aqueous phase having an acidic pH (i.e. a pH below 7) and/or an alcohol phase containing for example ethanol. The slurry may include an acidifying agent, such as nitric acid, and the pH of the liquid medium may be, for example, between 1 and 5. The slurry may also include an organic binder, such as polyvinyl alcohol (PVA), which is soluble in water.

As shown in fig. 3, after the slurry 150 is injected into the pores of the fibrous structure 10, refractory ceramic particles 1500 are present. Arrow 151 represents the movement of the slurry 150 injected into the fibrous structure 10. As shown in FIG. 4, arrow 152 represents the movement of the medium or liquid phase of the slurry being discharged by the filter layer 130.

The counter-convex mold 120 exerts pressure on the fibrous texture 10 during and after the injection step.

Furthermore, pumping P may be performed at the outlet port 112 during the discharge, for example using a primary vacuum pump. The pumping improves drainage and dries the fibrous structure more quickly.

In this configuration, the filter layer 130 enables the particles 1500 originally present in the slurry to remain in the fibrous structure 10 and all or part of the particles are deposited in the fibrous structure 10 by filtration.

After the injection and filtration steps, a fiber preform 15 is obtained, which comprises a fibrous texture 10 filled with refractory ceramic particles and a filter layer 130 bonded to the texture 10. During the injection process, a bond is achieved between the filter layer and the fibrous structure. The material is deposited between the filter layer and the fibrous structure and, due to the compaction, the assembly is integral. The sintering heat treatment then forms bridges between the particles, which completes the bond.

The preform obtained, which is then dried and then demoulded, is able to retain the shape adopted in the moulding cavity after demoulding, for example after compaction between the mould and the counter-mould due to the binder (for example PVA) present in the slurry.

The preform is then subjected to a heat treatment, here for example sintering in air at a temperature between 1000 ℃ and 1200 ℃, to pre-sinter the refractory ceramic particles, thereby forming a refractory ceramic matrix in the pores of the fibrous structure and the filter layer integral therewith. A composite component, such as an oxide/oxide composite component, is then obtained having a fiber reinforcement formed from a fiber preform that combines a fiber texture and a filter layer and has a high matrix-to-volume ratio, and a refractory ceramic matrix uniformly distributed throughout the fiber reinforcement.

By preparing fibrous structures and filter layers from silicon carbide and/or carbon fibres, and using fibres filled with carbides (e.g. SiC), borides (e.g. TiB)₂) Silicide (e.g. MoSi)₂) Or nitride (e.g. Si)₃N₄) A slurry of particles, parts made of CMC materials other than oxide/oxide materials can be obtained in the same way.

Alternatively, the filling liquid injected into the texture may contain particles of a refractory ceramic precursor, for example of the sol-gel or polymer type. In this case, the heat treatment comprises at least one step of converting the refractory ceramic precursor into a ceramic material (the so-called ceramization step), possibly followed by another sintering step to further densify the composite part.

Fig. 5 to 9 illustrate a method for preparing a sound attenuating module according to an embodiment of the present invention. As shown in fig. 5 and 6, the honeycomb 300 and the fiber skin 400 are placed in the tool 200 opposite the upper face 300a of the honeycomb. The honeycomb structure 300 may in particular be made of a metallic material or a composite material or a monolithic ceramic. In the case of composite materials, the fiber reinforcement of the honeycomb structure may be achieved in a variety of ways, as described in US5415715, for example, as shown in fig. 7A to 7C, by stacking and bonding fabric layers 311 (e.g., alumina fibers) in a staggered manner to form the blank 310. The bonding between the layers 311 is achieved along parallel strips 312, wherein the strips 312 on one side of the layers are staggered with respect to the strips on the other side (fig. 7A). For example, the tape 312 for the connection layer 311 may be manufactured by gluing or sewing. The laminate is cut into slices 313 (fig. 7B) perpendicular to the glue strips. Each slice is then stretched in a direction perpendicular to the face of the layer (arrow f1 in fig. 7B) to yield, by deformation, a bubble 3100 having hexagonal cells 314 (fig. 7C).

According to another embodiment shown in fig. 8A-8C, a two-dimensional layer 321 (e.g., made of SiC fibers) is layered and needled to form a blank 320 (fig. 8A). For example, layer 321 is a fabric layer or a composite of fabric and fiber fleece that provides fibers that can be easily removed by needles during needling through the layer. As shown in fig. 8B, slit-shaped cuts 322, whose size and location define the size and shape of the honeycomb, are staggered in the blank 320, for example, by water jets or lasers. After the slits are opened, the blank member 320 is stretched in a direction perpendicular to the planes of the slits to form the honeycomb structure 3200 by deformation, where the honeycomb structure 3200 has hexagonal cell channels 324 (arrow f2 in fig. 8C).

According to another embodiment, the fiber structure forming the reinforcement of the honeycomb structure can be achieved by arranging strips of fabric in the plane of the honeycomb walls and connecting these strips at the joints between the honeycombs.

According to another embodiment, the expandable fibrous structure is prepared by three-dimensional or multilayer weaving, as described in US 9631519.

After preparation, the honeycomb fiber reinforcement is densified. In the example described here, the fibrous blank intended to form the fibrous reinforcement of the honeycomb structure 300 is first impregnated with a slurry corresponding to a suspension of alumina powder in water. After removing the liquid phase of the slurry, the preform is expanded to have the shape of a porous structure. The expanded blank is then heat treated to consolidate and form the self-supporting honeycomb structure 300.

In the example described herein, the fiber sheath 400 is made of Nextel 610^TMThe alumina yarn is made by two-dimensional weaving. The fiber skin 400 is intended here to form a fiber reinforcement of a sound module skin made of an oxide/oxide composite material.

The tool 200 includes a die 210 and a counter die 220. The mold 210 includes a base 211 having a plurality of cell channels 212. Mold 210 also includes sidewalls 213 that form a mold cavity 214 with bottom 211. In the example shown, the tool 200 (in which the fibrous skin 400, the filter layer 230 and the honeycomb structure 300 are present) is closed at its lower part by a mould 210 and at its upper part by a counter mould 220, which counter mould 220 forms a lid of the closed tool 200. The die 210 and the counter die 220 are used to determine the dimensions of the preform.

The counter mould 220 has a plurality of injection ports 221, through which injection ports 221 a liquid filled with refractory ceramic particles is intended to be injected to penetrate the pores of the fibre skin 400 through the first face 400a of the fibre skin 400. In the example shown in fig. 5 and 6, the filling liquid is injected through a plurality of injection ports 221 opening in different areas of the mold cavity.

According to the invention, the filter layer 230 is inserted between the fibrous skin 400 and the bubble 300, which is located on the bottom 211 of the mold 210 having the tunnels 212. The filter layer according to the invention corresponds to a fibrous structure obtained by Unidirectional (UD) deposition, or two-dimensional (2D) or three-dimensional (3D) weaving of refractory ceramic fiber yarns made of at least one of the following materials: alumina, mullite, silica, aluminosilicate, borosilicate, silicon carbide, carbon or a mixture of several of these materials. The filter layer is preferably made of refractory ceramic fibers having the same properties as the refractory ceramic fibers of the fiber sheath. The thickness of the filter layer is preferably 0.1mm to 1 mm.

In the embodiment described herein, the filter layer 230 corresponds to the Nextel 610 filter^TMA 2D fabric layer made of alumina fiber yarn.

According to the invention, the filtering layer is partially densified to form a network of pores of a given size in the layer, which allows the filtrate of the slurry (i.e. its liquid phase) to pass through, while retaining the refractory ceramic particles present in the injected slurry.

For example, the filter layer may have an average pore size of between 0.1 μm and 20 μm and an average volume porosity of less than 50% after being partially densified.

The fibrous structure intended to form the filtration layer may be partially densified by several methods. In particular, the fibrous structure may be pre-impregnated or impregnated with a slurry filled with refractory particles. In this case, the porosity is adjusted by adjusting the densification rate in the filter layer after the particle pre-sintering by controlling the particle size, the packing ratio, and the binder in the slurry. The filtration layer may also be obtained by injecting a slurry filled with refractory particles into the fibrous structure, the initially introduced particles controlling the stack thickness and thus the final matrix volume ratio (Tvm). A coating or quenching process may also be used to densify the fibrous texture portion intended to form the filtration layer.

In the embodiment described herein, the filter layer 230 is made of a 2D fabric of alumina yarns impregnated with a slurry filled with 25 volume percent alumina particles that have been pre-sintered to partially densify the filter layer. The filter layer 230 allows liquid to drain from the fiber skin 400 and through the outlet cells 212 as a result of the pressure gradient applied between the outlet cells 212 and the injection port 221, the liquid passing through the cells of the honeycomb structure 300 to the outlet cells 212.

In the examples described herein, the filling liquid is a slurry containing refractory ceramic particles. Fig. 9 shows the configuration obtained during the injection of the slurry 250 and the discharge of the liquid medium from the slurry. Slurry 250 is injected through injection port 221 under pressure to penetrate fiber sheath 400 through first face 400a of fiber sheath 400. The refractory ceramic particles 2500 present in the slurry 250 are intended to allow the formation of a refractory ceramic matrix in the pores of the fiber sheath 400. In one example, the refractory ceramic matrix may be a refractory oxide matrix.

The slurry may be, for example, a suspension of alumina powder in water. The average particle size (D50) of the alumina powder may be between 0.1 μm and 2 μm. The alumina powder used may be an alpha-alumina powder.

More generally, the slurry may be a suspension containing refractory ceramic particles or refractory ceramic precursor particles having an average particle size between 0.1 μm and 10 μm. The volume content of the particles in the slurry prior to injection may be between 20% and 50%. The refractory ceramic particles may comprise a material selected from the group consisting of: alumina, mullite, silica, aluminosilicates, aluminophosphates, zirconia, carbides, borides, and nitrides or precursors of one or more of these materials. Depending on their basic composition, the refractory ceramic particles or refractory ceramic precursors may additionally be mixed with alumina particles, zirconia particles, aluminosilicate particles, rare earth oxide particles, rare earth silicate particles (which may be used, for example, for environmental barriers or thermal barriers), or any other filler (such as carbon black, graphite, or silicon carbide) for functionalizing the composite parts obtained.

The liquid medium of the slurry may for example comprise an aqueous phase having an acidic pH (i.e. a pH below 7) and/or an alcohol phase containing for example ethanol. The slurry may include an acidifying agent, such as nitric acid, and the pH of the liquid medium may be, for example, between 1 and 5. The slurry may also include an organic binder, such as polyvinyl alcohol (PVA), which is soluble in water.

As shown in fig. 9, after the slurry 250 is injected into the pores of the fiber skin 400, refractory ceramic particles 2500 are present. Arrow 251 represents the movement of the slurry 250 injected into the fiber sheath 400. As shown in FIG. 10, arrows 252 represent the movement of the medium or liquid phase of the slurry discharged by the filter layer 230.

In addition, pumping may be performed at the outlet port 212 during evacuation, for example using a primary vacuum pump. The pumping improves drainage and dries the fibrous structure more quickly.

In this configuration, the filter layer 230 enables particles 2500 originally present in the slurry to remain in the fiber skin 400, and all or a portion of the particles are deposited in the fiber skin 400 by filtration.

After the injection and filtration steps, a preform 35 is obtained, which comprises a fibrous skin 400 filled with refractory ceramic particles or refractory ceramic precursor particles, a filter layer 230 and a honeycomb structure 300, the filter layer 230 being bonded to the fibrous skin 400 and the honeycomb structure 300. During the injection process, a bond is achieved between the filter layer and the fibrous skin. The material is deposited between the filter layer and the fibrous skin and, as a result of the compaction, the whole is firmly bonded together. The sintering heat treatment then forms bridges between the particles, which completes the bond. The obtained preform is then dried and then demoulded, the preform being able to retain the shape adopted in the mould cavity after demoulding.

The preform is then subjected to a heat treatment, here for example pre-sintering in air at a temperature between 1000 ℃ and 1200 ℃, to bridge the refractory ceramic particles to each other, thereby forming a refractory ceramic matrix in the pores of the fibrous structure and the filter layer integral therewith.

The result is a sound attenuation module made of composite materials, such as an oxide/oxide composite component with fiber reinforcement formed from fiber preforms, which incorporates a fiber fabric, a filter layer, and a honeycomb structure.

By preparing fibrous skins, filter layers and honeycomb structures from silicon carbide and/or carbon fibres and using fibres filled with carbides (e.g. SiC), borides (e.g. TiB)₂) Silicide (e.g. MoSi)₂) Or nitride (e.g. Si)₃N₄) A slurry of particles, parts made of CMC materials other than oxide/oxide materials can be obtained in the same way.

Alternatively, the filling liquid injected into the fiber sheath may contain particles of refractory ceramic precursors, such as sol-gel or polymer types. In this case, the heat treatment comprises at least one step of converting the refractory ceramic precursor into a ceramic material (the so-called ceramization step), possibly followed by another sintering step to further densify the composite part.

The preparation of the sound attenuating module may also be supplemented by forming a second skin on the underside of the honeycomb structure. To this end, the silencing module is placed in a mould having a similar configuration to the previously described tool 200, by: a lower fibrous skin similar to the previously described upper fibrous skin 400 is placed opposite the underside of the honeycomb structure and a filter layer similar to filter layer 230 is inserted between the fibrous skin and the honeycomb structure. In this case the mould used differs from the tool 200 in that the filling slurry is injected on the opposite side, i.e. on the side of the tool 200 where the portholes 212 are present, the portholes are then replaced by injection ports, and the liquid phase of the slurry is drained from the side of the tool where the injection ports 221 are present, the injection ports are then replaced by portholes. In addition, perforations are made in the top skin in order to allow the liquid phase of the slurry that has passed through the filter layer and the honeycomb structure to exit. These perforations may be advantageously applied in the subsequent operation of the sound attenuating module. Indeed, it is common to perforate one of the skins of such modules to facilitate the capture of acoustic waves in bubbles of the bubble-like structure.

In another embodiment of the sound attenuating module, the upper and lower fiber skins and the honeycomb located therebetween are placed in a tool having a similar geometry as the tool 200 described above. In this case, the filling slurry is injected simultaneously into the upper and lower fibrous skins, and the solvent in the slurry is drained over the edges of the bubble (against which the filter layer or layers rest).

In another embodiment of the sound attenuating module, the fiber skin is placed against a plurality of adjacent bubbles in a tool similar to tool 200 described above, and a filter layer is interposed between the fiber skin and the bubbles. As in tool 200, the mold cavity may have a straight or curved shape. The mold cavity may also be in the shape of a complete ring or ring segment in which the honeycomb, fibrous skin, and filter layer are placed. In this way, a sound attenuating module may be formed in a single operation, which may be installed around a device such as an aircraft engine, for example.

In another embodiment, the honeycomb structure may be replaced with a ventilation structure, such as corrugated sheet metal or similar forms of ventilation structures.

The process of the invention can also be advantageously used for the preparation of composite parts with complex geometries, in particular parts with semi-toroidal, toroidal and frustoconical shapes. The method of the invention can therefore be used to prepare parts made of composite material, such as the crankcase, the combustion chamber or the rear body (plug) of an aircraft engine. In this case, the mould filled with the slurry and the injection tool match the shape of the part to be prepared, the injected fibrous structure and the associated filtering layer easily conforming to the geometry of the mould of the tool, which is more complicated if a rigid part made of porous material is used to evacuate the liquid phase of the slurry.