fibrous preform for reinforcing parts made of composite material with improved local thickness variation

Abstract

A fibrous preform for reinforcing composite parts with improved local thickness variation. A fibrous preform (200) with a three-dimensional weave comprises first (203) and second (208) parts adjacent in a warp direction (DC). The first part (203) has, in a direction perpendicular to the warp (DC) and weft (DT) directions, a thickness (E203) greater than the thickness (E208) of the second part (208). The first part includes a debonding element delimiting an internal housing (240) between a first and second skin (204, 205). The first part (203) further comprises an insertion element present in the internal housing between the first and second skins. The insertion element consists of an open-porosity gyroid structure (10) made of ceramic material. Figure for the abstract: Fig. 3.

Description

Title of the invention: Fibrous preform for reinforcing parts made of composite material with improved local thickness variation. Technical field

[0001] The present invention relates to the production of parts in composite material and more particularly to the production by three-dimensional (3D) or multi-layer weaving of fibrous reinforcement preforms for such parts. Previous technique

[0002] One application of the invention is the production of parts made of ceramic matrix composite (CMC) material that exhibit good mechanical properties, making them suitable for use as structural elements and advantageously retaining these properties at high temperatures. Due to their superior resistance to high temperatures, CMC materials can be used at elevated temperatures. In the field of aircraft engines, CMC materials allow for higher temperatures to which parts are subjected, thereby improving engine efficiency and reducing fuel consumption. Furthermore, their use contributes to optimizing the performance of turbomachinery, particularly by reducing the overall mass of the turbomachine, which further contributes to lower fuel consumption and thus to a significant reduction in pollutant emissions.

[0003] The invention relates more particularly to composite material parts having one or more locally thickened sections, as is the case, for example, with the root of an aircraft engine blade, which corresponds to an area of ​​significant thickness variation in the composite material part. In the case of a composite material part with a variable thickness, the change in thickness is controlled at the level of the fibrous preform intended to form the reinforcement of the part.

[0004] The fabrication of blades from composite material for turbomachinery has already been proposed. Reference is made in particular to US patent 2018 / 038021, which describes a solution consisting of using braids in the thicker sections of the fibrous preform in order to reduce the thickness reduction capacity during the shaping of the 3D fibrous structure under compression. However, during the compression of such a preform in a former, the presence of the braids leads to a failure to maintain the required fiber volume ratio in the parts of the preform intended to form the blade root bearing surfaces, as well as an asymmetry in the ratio volumetric fiber density in these parts along the longitudinal direction of the preform.

[0005] Another solution described in US document 2011 / 0311368 proposes to make the preform part of the blade foot using an insert in order to form a bulb-shaped portion at the level of the part of the blade corresponding to its foot.

[0006] However, the presence of such an insert in the fibrous preform disrupts the implementation of the STM (Slurry Transfer Molding) process, which consists of injecting a powder into the preform via a slurry in order to densify it. In this case, the insert is an obstacle to the powder injection.

[0007] It is therefore desirable to be able to have 3D or multilayer fibrous preforms with parts of extra thickness that do not have the aforementioned disadvantages. Description of the invention

[0008] To this end, according to the invention, a fibrous preform for reinforcing a part made of ceramic matrix composite material is proposed, comprising a plurality of layers of weft yarns and layers of warp yarns linked together in a three-dimensional weave, the fibrous preform comprising at least first and second parts adjacent in the warp direction, the first part having, in a direction perpendicular to the warp and weft directions, a thickness greater than the thickness of the second part, the first part comprising a debonding delimiting an internal housing between a first and a second skin, characterized in that the first part further comprises an insertion element present in the internal housing between the first and second skins, the insertion element being made of a gyroid structure with open porosity made of ceramic material.

[0009] The gyroid structure, not comprising fibers and being rigid, i.e. undeformable, allows better control of the fiber ratio in the parts of the preform compressed against it.

[0010] Furthermore, the gyroid structure comprises a network of interconnected channels defining porosity in all three spatial directions. In the case of impregnation of the preform with a slip (injection molding process, also known as "slurry cast" or "slurry transfer molding" (STM)), the injection and drainage of the slip are greatly facilitated by the gyroid structure, which has orthogonally oriented channels. When particles are injected into the preform, they can circulate freely within the gyroid structure and fill it in all spatial directions.

[0011] According to a particular characteristic, the gyroid structure has a porosity rate between 30% and 70%, preferably 60%.

[0012] According to another particular characteristic, the width of the cells of the gyroid structure is between 200 pm and 1 mm, preferably 500 pm.

[0013] According to another particular characteristic, the gyroid structure has, in a direction perpendicular to the warp and weft directions, a decreasing thickness in the direction of the second part.

[0014] According to another particular feature, the fibrous preform comprises carbon wires or wires of ceramic material.

[0015] According to another particular feature, the gyroid structure is made of a ceramic material selected from one of the following materials; silicon carbide, silicon carbide / silicon and silicon nitride.

[0016] The invention also relates to a part made of ceramic matrix composite material comprising a fibrous reinforcement densified by a matrix at least partially ceramic, said fibrous reinforcement being constituted by a fibrous preform according to the invention.

[0017] The invention also relates to a method for manufacturing a fibrous preform by three-dimensional or multi-layer weaving between a plurality of layers of weft yarns and layers of warp yarns, the fibrous preform comprising at least first and second parts adjacent in the warp direction, the first part having, in a direction perpendicular to the warp and weft directions, a thickness greater than the thickness of the second part, the method further comprising, during the weaving of the first part, the formation of a debonding delimiting an internal housing between a first and a second skin, characterized in that said method further comprises the disposition of an insertion element in the internal housing between the first and second skins, the insertion element being made of a gyroid structure with open porosity in ceramic material.

[0018] A method for manufacturing a part made of ceramic matrix composite material comprising the following steps: - production of a fibrous preform in accordance with the manufacturing process of a fibrous preform according to the invention,

[0019] - placement of the fibrous preform in a mold comprising in its part lower, a piece made of porous material,

[0020] - consolidation of the fibrous preform by chemical infiltration in the gas phase, - placement of the consolidated preform in a mold - injection under pressure of a liquid containing a powder of refractory ceramic particles or particles of a refractory ceramic precursor into the fibrous preform, - drainage through the porous material part of the liquid that has passed through the fibrous preform and retention of the powder of refractory ceramic particles or particles of a refractory ceramic precursor inside said preform by said porous material part so as to obtain a fibrous preform loaded with refractory ceramic particles or particles of a refractory ceramic precursor, the liquid being evacuated by at least one vent present on the bottom of the mold, - drying of the consolidated preform, - demolding of the consolidated preform, and - infiltration of the fibrous preform with a molten silicon-based composition (silicidation) so as to form a dense ceramic matrix in said preform.

[0021] The invention also relates to the use of the manufacturing process of a part made of ceramic matrix composite material according to the invention for the manufacture of a turbomachine blade made of composite material. Brief description of the drawings

[0022] [Fig-1] Fig. 1 illustrates in a very schematic way a woven fibrous blank three-dimensional for producing a fibrous preform according to an embodiment of the invention,

[0023] [Fig.2] The [Fig.2] is a partial schematic view at enlarged scale of a gyroid structure used as an insertion element in the preform obtained from the fibrous blank of the [Fig.1],

[0024] [Fig.3] Fig.3 is a tomography of a portion of a foot preform incorporating a gyroid structure prior to the injection of ceramic particles,

[0025] [Fig.4] The [Fig.4] is a schematic cross-sectional view of an injection tooling used to impregnate the fibrous preform of the [Fig.3],

[0026] [Fig.5] The [Fig.5] is a schematic cross-sectional view showing the steps of impregnation of the fibrous texture preform with a slip loaded in the tooling of the [Fig.4],

[0027] [Fig.6] The [Fig.6] a tomography of the preform foot part of the [Fig.3] after injection of ceramic particles. Description of the implementation methods

[0028] The invention applies generally to the production of fibrous preforms suitable for forming fibrous reinforcements for the manufacture of parts in ceramic matrix composite material, in particular aeronautical engine blades, the parts being obtained by densification of the fibrous textures by a matrix.

[0029] The fibrous preform of the invention is obtained from a fibrous texture produced by three-dimensional weaving or by multilayer weaving.

[0030] By "three-dimensional weaving" or "3D weaving", we mean here a weaving method in which at least some of the warp yarns bind weft yarns over several weft layers.

[0031] By "multilayer weave" is meant here a 3D weave with several layers of weft, the basic weave of each layer being equivalent to a classic 2D fabric weave, such as a plain weave, satin or twill weave, but with certain points of the weave which link the weft layers together.

[0032] Creating the fibrous texture by 3D or multilayer weaving allows for bonding between the layers, thus ensuring good mechanical strength of both the fibrous texture and the resulting composite material part, all in a single textile operation. 3D weaving can notably be an "interlock" weave. "Interlock" weave refers to a 3D weave structure in which each warp layer connects several weft layers, with all the yarns in the same warp column having the same movement within the plane of the weave.

[0033] An example of the realization of a fibrous preform according to the invention is now described. In this example, the weaving is carried out on a Jacquard-type loom.

[0034] Fig. 1 shows very schematically a fibrous blank 100 from which a fibrous preform 200 is obtained for forming the fibrous reinforcement of an aeronautical engine blade.

[0035] The blank 100 of the fibrous preform 200 is obtained by three-dimensional weaving, or 3D weaving, or by multilayer weaving carried out in a known manner using a Jacquard-type loom on which a bundle of warp yarns or strands 201 is arranged in a plurality of layers and extending in a direction Dc, the warp yarns being linked by weft layers 202 also arranged in a plurality of layers and extending in a direction DT perpendicular to the direction Dc. A detailed example of the realization of a fibrous preform intended to form the fibrous reinforcement of an aircraft engine blade is described in particular in detail in US documents 7,101,154, US 7,241,112 and WO 2010 / 061140.

[0036] The fibrous blank 100 is woven in a single piece as a strip extending generally in the direction Dc corresponding to the direction of the warp threads 201 and the longitudinal direction of the blade to be produced. The fibrous preform comprises, along the direction Dc, a portion of the foot preform 203, a portion of the strut preform 207, and a portion of the airfoil preform 208.

[0037] During weaving, a debinding 206 is made inside the foot preform part 203 of the fibrous blank 100 between two successive layers of warp yarns. The debonding 206 extends along a plane parallel to the surface of the fibrous blank and over a debonding zone delimited by a contour 206a separating the foot preform portion 203 into a first and second skins 204 and 205. Furthermore, the debonding 206 extends in the DT direction between a first lateral edge 2030 and a second lateral edge 2031. The debonding 206 also opens at the free lower end 2032 of the foot preform portion 203. The debonding 206 thus forms an internal recess 240 in the foot preform portion 203 which is accessible via the free lower end 2032.

[0038] The internal housing 240 is intended to receive an insertion element during the shaping of the fibrous blank. According to the invention, the insertion element consists of a gyroid structure with open or through-hole porosity made of ceramic material.

[0039] Figure 2 illustrates part of a gyroid structure 10 constituting the element of insertion. The gyroid structure 10 comprises a network of continuous channels 11 extending along different principal crystallographic axes, each channel being connected to other channels which intersect and which "rotate" along the length of the channel. A gyroid structure is described geometrically by the formula sin(x)*cos(y)+sin(y)*cos(z)+sin(z)*cos(x) = 0.

[0040] The gyroid structure is made of ceramic material compatible with the ceramic material of the part in which it is integrated. The gyroid structure may be made in particular, but not exclusively, of silicon carbide (SiC), silicon carbide / silicon (SiC / Si) and silicon nitride (Si3N4).

[0041] The gyroid structure is preferably manufactured by additive manufacturing. Among the additive manufacturing processes that can be used are, in particular, powder bed fusion or sintering processes, and fused filament 3D printing processes. Powder bed fusion or sintering processes include, in particular, selective laser sintering, selective laser melting, beam laser melting, and electron beam melting.

[0042] The gyroid structure inserted in the internal housing 240 of the fibrous preform 200 has a porosity rate of between 30% and 70%, preferably 60% with a cell width of the gyroid structure of between 200 pm and 1 mm, preferably 500 pm.

[0043] The gyroid structure 10 has the advantage of exhibiting a porosity that is both communicating and open (which opens onto the surface of the structure) in all three spatial directions X, Y, Z. Thus the ceramic particles injected during the densification of the fibrous preform will be able to travel and therefore fill the insertion element in the 3 directions of space.

[0044] Fig. 3 illustrates the fibrous preform 200 after insertion of the gyroid structure 10 into the internal housing 240 so that the foot preform part 203 has, in a direction perpendicular to the warp and weft directions, a thickness E203 greater than the thickness E20s of the aerodynamic profile preform part 208.

[0045] The gyroid structure 10 has, in a direction perpendicular to the warp and weft directions, a thickness Ei0 decreasing towards the preform part of the aerodynamic profile 208. The gyroid structure 10 thus includes a tapered part 12 which is housed in the bottom of the internal housing 240. The gyroid structure 10 being rigid, it allows both shaping of the foot preform part 203 and of the stilt preform part 207 and control of the fiber content in these preform parts.

[0046] Once the fibrous preform 200 is produced, it is consolidated. In the example described here, the preform is consolidated by depositing an interphase onto the surface of the preform fibers using chemical gas infiltration (CVI). For this purpose, the preform, held in a shaping tool, for example made of graphite, is placed in a furnace or CVI system to deposit an interphase onto the surface of the fibers of the texture. This interphase is based, in particular, on boron nitride (BN) or pyrocarbon (PyC). The thickness of the interphase is preferably between 10 nm and 1000 nm.

[0047] The next step consists of impregnating the preform with a slurry following the injection molding process (“Slurry Cast” in English) or STM transfer molding (for “Slurry Transfer Molding” in English).

[0048] As illustrated in Figures 4 and 5, the fibrous preform 200, consolidated with the gyroid structure present in the internal housing 240, is placed in a tool 300 comprising a mold 310 and a counter-mold 320. The mold 310 includes a bottom 311 equipped with a vent 312. The mold 310 also includes a side wall 313 which, together with the bottom 311, forms a molding cavity 314. In the illustrated example, the tool 300, in which the fibrous preform 200 is present, is closed at its lower part by the mold 310 and at its upper part by the counter-mold 320, forming a lid that closes the tool 300. The mold 310 and the counter-mold 320 serve to dimension the preform and thus the part to be obtained, as well as to adjust the fiber content in the part to be obtained.The presence of the gyroid structure 10 in the internal housing 240 contributes to the molding of the foot and stilt parts of the blade to be manufactured, while allowing good control of the fiber content in these parts.

[0049] In the example described here, the side wall 313 has a plurality of injection ports 321 (only one of which is shown in the cross-section in Figures 4 and 5) through which a liquid loaded with refractory ceramic particles or particles of a refractory ceramic precursor is intended to be injected in order to penetrate the porosity of the fibrous preform 200 through a slice thereof via the gyroid structure 10. In the example illustrated in Figures 4 and 5, the loaded liquid is intended to be injected through a plurality of injection ports 321 opening into different areas of the gyroid structure. The mold 310, for its part, includes a liquid discharge vent 312.

[0050] A porous material part 330 is present in the molding cavity 314 between the mold 310 and the fibrous preform 200. The porous material part 330 has an upper face 330a in contact with a second face of the fibrous preform 200 through which the liquid is intended to drain. In the example illustrated in Figures 4 and 5, the second face of the fibrous preform 200 is located on the opposite side from the first face.

[0051] The part made of porous material 330 can, for example, be made of microporous polytetrafluoroethylene (PTFE) such as the "microporous PTFE" products sold by Porex®. For example, the PM 0130 material marketed by Porex®, with a pore size between 1 µm and 2 µm, can be used to make the part from porous material 330.

[0052] The porous material part 330 allows the drainage of the liquid outside the fibrous preform 200 and its evacuation through the outlet vent 312 due to the application of a pressure gradient between the outlet vent 312 and the injection ports 321.

[0053] By way of example, the porous material part 330 may have a thickness greater than or equal to 1 mm, or even several millimeters. The average porosity of the porous material part 330 may be approximately 30%. The average pore size (D50) of the porous material part may, for example, be between 1 µm and 2 µm.

[0054] In one embodiment, the porous material part 330 can be rigid and have a shape corresponding to the shape of the preform and the composite material part to be obtained. In this case, the porous material part can, for example, be produced by thermoforming. Alternatively, the porous material part can be deformable and can take the shape of the mold, which corresponds to the shape of the preform and the composite material part to be obtained.

[0055] Before injecting a slip into the fibrous preform 200, a compaction pressure is applied to compact the fibrous preform between the mold 310 and the counter-mold 320 can be applied by clamping the mold or by means of a press, this compaction pressure being able to be maintained during injection.

[0056] Alternatively, compaction pressure can be applied after the start of the injection of the loaded liquid and can then be maintained. Applying compaction pressure can compact the preform to aid in liquid drainage and achieve a target thickness for the fibrous preform without damaging it.

[0057] In the example described here, the loaded liquid corresponds to a slurry containing refractory ceramic particles. Figure 5 illustrates the configuration obtained during the injection of a slurry 350 and the drainage of the liquid medium thereof. The slurry 350 was injected under pressure through the injection ports 321 so as to penetrate the fibrous preform 200 through the gyroid structure. The refractory ceramic particles 3500 present in the slurry 350 are intended to enable the formation of a refractory ceramic matrix within the porosity of the fibrous preform 200.

[0058] Slip can for example be a suspension of SiC powder in water.

[0059] The liquid medium of the slip may, for example, comprise an aqueous phase having an acidic pH (i.e., a pH less than 7) and / or an alcoholic phase comprising, for example, ethanol. The slip may contain an acidifier such as nitric acid, and the pH of the liquid medium may, for example, be between 1.5 and 4. The slip may also contain an organic binder such as polyvinyl alcohol (PVA), which is notably soluble in water.

[0060] As illustrated in [Fig. 5], the refractory ceramic particles 3500 are present after injection of the slip 350 into the porosity of the fibrous preform 200, including that of the gyroid structure 10. The arrows 351 represent the movement of the slip 350 injected into the fibrous preform 200. The arrows 352 represent the movement of the medium or liquid phase of the slip drained by the porous material part 330.

[0061] The counter-mold 320 exerts pressure on the fibrous preform 200 during and after the injection step.

[0062] Pumping P can also be carried out at the outlet vent 312 during drainage, for example by means of a primary vacuum pump. Performing such pumping improves drainage and allows the fibrous texture to dry more quickly.

[0063] As an alternative or in combination, during drainage the liquid medium still present in the porosity of the fibrous texture can be heated in order to evaporate it through the second face of the fibrous texture and the part made of porous material. For example, the temperature of the liquid medium can be raised to a temperature between 80°C and 105°C.

[0064] In this configuration, the porous material part 330 allows the refractory ceramic particles 3500 initially present in the slip to be retained in the fibrous preform 200 and all or part of these particles to be deposited by filtration in the fibrous preform.

[0065] Once the injection and drainage steps have been carried out, a fibrous preform 200 loaded with refractory ceramic particles, for example SiC particles as illustrated in [Fig.6], is obtained.

[0066] The preform obtained is then dried and demolded, the preform being able to retain after demolding the shape adopted in the molding cavity, for example its shape adopted after compaction between the mold and the counter-mold thanks to the presence of a binder in the slip such as PVA.

[0067] The preform is then infiltrated with a molten silicon-based composition (silicidation) so as to form a ceramic matrix, a densification process known as the MI process ("Melt Infiltration").

[0068] The steps of impregnating the preform with a slip and silicifying, implemented for densification, can be replaced by a densification process called "PIP" (for "Polymer Impregnation & Pyrolysis"). This process, known to exist, involves impregnating the preform with a pre-ceramic polymer followed by pyrolysis, with these two cycles being repeated several times.

[0069] The densified preform can optionally be machined after densification.

[0070] A CMC composite material part is then obtained, equipped with a fibrous reinforcement formed by the fibrous preform and having a high volumetric matrix ratio with a homogeneous distribution of the refractory ceramic matrix throughout the fibrous reinforcement.

[0071] A coating may be deposited on the part in order to improve its surface condition and / or to form a protective layer on the surface of the part.

[0072] The filled liquid injected into the preform may, alternatively, contain particles of a refractory ceramic precursor, for example of the sol-gel or polymeric type. In this case, the heat treatment includes at least one step of transforming the refractory ceramic precursor into a ceramic material (the so-called ceramization step), possibly followed by an additional sintering step to further densify the composite part.

[0073] Figure 6 illustrates the fibrous preform 200 after the injection of refractory ceramic particles. It can be seen that the porosity of the textile parts of the preform as well as the gyroid structure is uniformly and perfectly filled by the ceramic particles.

Claims

Demands

1. A fibrous preform (200) for reinforcing a part made of a ceramic matrix composite material, comprising a plurality of layers of weft yarns and layers of warp yarns bonded together in a three-dimensional or multilayer weave, the fibrous preform (200) comprising at least two adjacent first (203) and second (208) parts in the warp direction (Dc), the first part (203) having, in a direction perpendicular to the warp (Dc) and weft (DT) directions, a thickness (E203) greater than the thickness (E2os) of the second part (208), the first part comprising a debonding (206) delimiting an internal housing (240) between a first and a second skin (204, 205), characterized in that the first part (203) further comprises an insertion element present in the internal housing between the first and second skins, the insertion element being made of a gyroid structure (10) with open porosity ceramic material.

2. Fibrous preform according to claim 1, wherein the gyroid structure (10) has a porosity rate between 30% and 70%.

3. Fibrous structure according to claim 1 or 2, wherein the width of the cells of the gyroid structure (10) is between 200 pm and 1 mm.

4. Fibrous preform according to any one of claims 1 to 3, wherein the gyroid structure (10) has, in a direction perpendicular to the warp and weft directions, a thickness (Ei0) decreasing in the direction of the second part (208).

5. Fibrous preform according to any one of claims 1 to 4, wherein the fibrous preform (200) comprises carbon fibers or ceramic material fibers.

6. Fibrous preform according to any one of claims 1 to 5, wherein the gyroid structure (10) is made of a ceramic material selected from one of the following materials: silicon carbide, silicon carbide / silicon and silicon nitride.

7. Part made of ceramic matrix composite material comprising a fibrous reinforcement densified by a matrix at least partially ceramic, said fibrous reinforcement being constituted by a fibrous preform (200) according to any one of claims 1 to 6.

8. A method for manufacturing a fibrous preform (200) by three-dimensional or multi-layer weaving between a plurality of layers of weft yarns and layers of warp yarns, the fibrous preform (200) comprising at least first (203) and second (208) parts adjacent in the warp direction (Dc), the first part (203) having, in a direction perpendicular to the warp (Dc) and weft (DT) directions, a thickness (E203) greater than the thickness (E2os) of the second part (208), the first part comprising a debonding (206) delimiting an internal housing (240) between a first and a second skin (204, 205), characterized in that said method further comprises the disposition of an insertion element in the internal housing between the first and second skins (204, 205), the insertion element being made of a gyroid structure (10) with open porosity of ceramic material.

9. A method for manufacturing a part made of a ceramic matrix composite material comprising the following steps: - production of a fibrous preform (200) according to the method of claim 8, - consolidation of the fibrous preform by chemical infiltration in the gas phase, - placement of the consolidated fibrous preform (200) in a mold (310) having in its lower part a part made of a porous material (330), - injection under pressure of a liquid (350) containing a powder of refractory ceramic particles or particles of a refractory ceramic precursor into the fibrous preform (200),- drainage through the porous material part (330) of the liquid that has passed through the fibrous preform (200) and retention of the powder of refractory ceramic particles or particles of a refractory ceramic precursor inside said preform by said porous material part (330) so as to obtain a fibrous preform loaded with refractory ceramic particles or particles of a refractory ceramic precursor, the liquid being discharged through at least one vent present on the bottom of the mold, - drying of the fibrous preform, - demolding of the fibrous preform, and,

10. - infiltration of the fibrous preform with a molten silicon-based composition so as to form a refractory ceramic matrix in said preform. Use of the process according to claim 9 for the manufacture of a turbomachine blade from composite material.