Method for manufacturing a fibrous preform for reinforcing a part made of composite material with a high local variation in thickness using fiber mat

Abstract

Method for manufacturing a fibrous preform for reinforcing parts in composite material with high local variation in thickness by fiber mat. A method for manufacturing a fibrous preform for a part in composite material, the method comprising at least: - the creation of a fibrous texture (200) by three-dimensional or multi-layer weaving between a plurality of weft layers comprising in part weft yarns or strands and layers of warp yarns or strands, the fibrous texture (200) comprising first and second parts (203, 205) adjacent in a longitudinal direction (DL), the first part (203) having, in a thickness direction (DE), a thickness (E203) greater than the thickness (E205) of the second part (205), - the shaping of the fibrous texture (200) to obtain a fibrous preform (500).During the weaving of the fibrous texture (200), strips (30), each consisting of a mat of fibers, are inserted into weft layers of the first part (203). Figure for the abbreviation: Fig. 3.

Description

Title of the invention: Method for manufacturing a fibrous preform for reinforcing composite material parts with significant local thickness variation using fiber mat. Technical field

[0001] The present invention relates to the production of fibrous preforms intended to form fibrous reinforcements of parts made of composite material. Previous technique

[0002] One application of the invention is the production of parts made of structural composite material, that is, structural parts with fiber reinforcement and densified by a matrix. Composite materials make it possible to produce parts with a lower overall mass than the same parts when made of metallic material. In the field of aircraft engines, composite materials contribute to optimizing the performance of turbomachinery, particularly by reducing the overall mass of the turbomachine, which contributes to lower fuel consumption and therefore to a significant reduction in pollutant emissions. Furthermore, when made of thermostructural composite material, the parts allow for higher operating temperatures, which improves engine efficiency and further reduces fuel consumption.

[0003] The invention relates more particularly to composite material parts having locally one or more parts of extra thickness as is the case for example of the foot of an aeronautical engine blade which corresponds to an area of ​​high variation in thickness in the composite material part.

[0004] In the case of a part made of composite material having an evolving thickness, the change in thickness is controlled at the level of the fibrous texture or the fibrous preform intended to form the reinforcement of the part.

[0005] 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 areas of excess thickness in the fibrous preform in order to reduce the thickness reduction capacity during the shaping of the 3D fibrous structure with compression. It is also possible to replace the braids with yarns having a locally higher fiber count (i.e., a larger cross-sectional size) than the other yarns in the preform. However, during the compression of such preforms in a former, the presence of braids or high-fiber yarns leads to a failure to maintain the fiber volume ratio in the areas of the Preforms designed to form the blade root spans, as well as an asymmetry in the fiber volume ratio in these parts along the longitudinal direction of the preform. Furthermore, the use of high-quality yarns limits the infiltration of gases or powders, for example, during the production of a final CMC material.

[0006] Another solution described in US patent 2011 / 0311368 proposes manufacturing the blade root preform using an insert to create a bulb-shaped portion at the root of the blade. Since the insert is solid, it must have openings to allow gases or powders to pass through during densification, while significantly reducing the specific surface area. The main drawback of this solution is the high manufacturing cost of the insert, particularly in silicon carbide (implemented by additive manufacturing – high-temperature sintering).

[0007] The use of the previous solutions also increases the specific surface area available for gas-borne densification (GBD) in an area with low gas supply. This leads to thin deposits in these areas. Although these areas are not the most stressed in the part, the "pump" effect also generates a gradient and a deposition deficit in the internal layers of the feet.

[0008] Another solution described in WO 2024 / 110703 involves using yarn crossings to locally increase the bulk. However, the use of yarn crossings stiffens the fibrous texture, which complicates its shaping. Description of the invention

[0009] It is therefore desirable to be able to have fibrous preforms having parts of extra thickness which do not have the aforementioned disadvantages.

[0010] To this end, according to the invention, a method for manufacturing a fibrous preform for a part made of composite material is proposed, the method comprising at least:

[0011] - the creation of a fibrous texture by three-dimensional or multilayer weaving between a plurality of weft layers comprising partly weft yarns or strands and layers of warp yarns or strands, the fibrous texture comprising at least first and second parts adjacent in a longitudinal direction, the first part having, in a thickness direction perpendicular to the longitudinal direction, a thickness greater than the thickness of the second part,

[0012] - the shaping of the fibrous texture to obtain a fibrous preform,

[0013] characterized in that, during the weaving of the fibrous texture, strips each made up of a mat of fibers are inserted into weft layers of the first part.

[0014] Inserting strips of fiber mat into the portion of the fibrous texture intended to form an additional thickness significantly expands or swells the fibrous texture. This results in a thicker fibrous preform that adapts to sudden thickness variations, and this is achieved with a very low fiber content, allowing for good gas infiltration of this thickened area. Furthermore, the use of fiber mat for the strips is very economical compared to the manufacturing cost of prior art inserts.

[0015] According to a particular feature of the manufacturing process for a fibrous preform, strips made of a fiber mat are inserted into weft layers located in the core of the first part. This minimizes the potential impact of the strips on the mechanical properties of the final part.

[0016] According to another particular feature of the manufacturing process for a fibrous preform, each warp layer comprises the same number of yarns or strands, the yarns or strands present in the warp layers all having the same fiber count. This homogenizes the structure in the fibrous texture and the flexibility of the resulting fibrous preform.

[0017] According to another particular feature of the process for manufacturing a fibrous preform, it further comprises the production of a fiber mat and the cutting of said fiber mat into strips. The strips are thus produced economically. The fiber mat can also be made from fibers derived from weaving scraps, which allows for the recycling of waste or weaving scraps while further reducing the cost of manufacturing the strips.

[0018] The invention also relates to a method for manufacturing a part made of composite material comprising the following steps:

[0019] - production of a fibrous preform according to a manufacturing process of a fibrous preform according to the invention,

[0020] - densification of the fibrous preform.

[0021] The invention also relates to a fibrous preform obtained in accordance with a process for manufacturing a fibrous preform according to the invention.

[0022] The invention also relates to a part made of composite material obtained in accordance with the manufacturing process of a part made of composite material according to the invention. Brief description of the drawings

[0023] [Fig. 1] [Fig. 1] illustrates in a very schematic way a three-dimensional woven fibrous blank intended for the creation of a fibrous texture according to an embodiment of the invention,

[0024] [Fig.2] The [Fig.2] is an enlarged scale warp cross-sectional view partially representing a plane of a weave of a portion of the excess thickness of the fibrous texture of the [Fig.1],

[0025] [Fig.3] The [Fig.3] is a schematic view of a fibrous texture obtained from the fibrous blank of the [Fig.1],

[0026] [Fig.4] The [Fig.4] is a schematic view of a fibrous preform obtained from the fibrous texture extracted from the fibrous blank of the [Fig.1]. Description of the implementation methods

[0027] The invention applies generally to the manufacture of composite material parts, the manufacturing process of which includes one or more processing steps carried out after the densification step. The parts may, in particular, be made of ceramic matrix composite (CMC) or organic matrix composite (CMO).

[0028] The invention finds an advantageous but not exclusive application in the manufacture of blades for aeronautical gas turbine engines.

[0029] An example of an embodiment of the process of the invention applied to the manufacture of a CMC turbine blade is described below.

[0030] The fibrous preform of the invention is obtained from a fibrous texture made at least in part by three-dimensional weaving or by multilayer weaving.

[0031] 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.

[0032] 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.

[0033] The production of the fibrous blank by 3D or multilayer weaving makes it possible to obtain a bond between the layers, thus ensuring good mechanical strength of the fibrous blank and the resulting composite material part, in a single textile operation. The 3D weave can notably be an "interlock" weave. "Interlock weave" here 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.

[0034] An example of the realization of a fibrous texture according to the invention is now described. In this example, the weaving is carried out on a Jacquard-type loom.

[0035] Fig. 1 shows very schematically a fibrous blank 100 from which a fibrous texture 200 is obtained for use in forming the fibrous reinforcement of an aircraft engine blade.

[0036] The blank 100 of the fibrous texture 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, the warp yarns being linked by weft layers 202 also arranged in a plurality of layers, some weft layers further comprising strips of fiber mat as explained in detail below. 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.

[0037] The fibrous blank 100 is woven as a strip extending generally in a direction Dc corresponding to the direction of the warp yarns 201 and the longitudinal direction of the blade to be produced. In the fibrous blank 100, the fibrous texture has, along a thickness direction DE perpendicular to the longitudinal direction Dc, a variable thickness both in the direction Dc and in a direction DT perpendicular to the direction Dc and corresponding to the direction of the weft yarns 202. The thickness variations are determined according to the longitudinal thickness and the profile of the blade to be produced. In its portion intended to form a foot preform, the fibrous texture 200 has, in the direction Dc, a portion of extra thickness 203 determined according to the thickness of the foot of the blade to be produced.The fibrous texture 200 extends into a section of decreasing thickness 204 intended to form the sail's leading edge, and then into a section 205 intended to form the sail's blade. The fibrous texture 200 is woven in a single piece and, after the fringe yarns are cut from the selvedges, must have the almost final shape and dimensions of the sail ("net shape"). To this end, in the sections of varying thickness in the fibrous texture, as in the section of decreasing thickness 204, the reduction in thickness of the preform is achieved by progressively removing layers of weft during weaving.

[0038] Throughout the following text and in all the drawings, it is mentioned and shown by convention and for the sake of convenience that it is the warp yarns that are diverted from their paths to catch yarns or braids of one or more weft layers. However, a reversal of roles between warp and weft is possible and should be considered as also covered by the claims.

[0039] According to the invention, strips 30 are inserted into the weft layers located in the core of the thicker part 203 of the fibrous texture 200. According to the invention, each strip consists of a fiber mat. "Fiber mat" refers to a non-woven fibrous texture corresponding to an agglomeration of discontinuous fibers, the fibers generally being arranged randomly or loosely. Conversely, the yarns or strands used in the warp and weft layers each comprise continuous fibers oriented in the direction of the yarn or strand.

[0040] Strips made from a fiber mat exhibit a high bulking characteristic, superior to that of the yarns or strands used in the warp and weft layers. This significant bulking of the fiber mat strips allows for a localized increase in the thickness of the fibrous texture while maintaining a low fiber content. The use of such strips therefore makes it possible to significantly and locally increase the thickness of a fibrous preform without substantially altering the average fiber content in the preform.

[0041] Fiber mat strips can be cut from a roll of fiber mat obtained, for example, by wet-laid production. Cutting can be done on a cutting table or with a slit tape cutting machine, or directly at the end of the fiber mat production line. An additional method may consist of joining fiber mat strips by bonding them with a PVA-based adhesive.

[0042] The fiber mat strips thus manufactured can, for example, have a length between 40 m and 200 m. The strips are then packaged into reels for compatible use by the weft selection system (lance) of a 3D loom.

[0043] Advantageously, the source fiber mat from which the strip(s) are obtained can be made from fibers from weaving scraps or waste, such as when trimming a fibrous texture in a woven blank.

[0044] Figure 2 is a partial enlarged view of a cross-sectional plan of a weave of Weaving of the thicker portion 203 of the fibrous texture 200 obtained by 3D weaving. In this example, the fibrous texture 200 comprises, in its thicker portion 203, 48 weft layers, or 24 half-layers t1 to t48. In the core 2103 located between the opposing skins 2032 and 2033, the weft layers are linked together by warp yarns 201 following a 3D weave of the interlock type. In skins 2032 and 2033, the weave between the warp yarns 201 and the weft yarns 202 is two-dimensional with an irregular satin weave. The satin weave only concerns the half-layers of weft t1 and t2 and the half-layers of weft t47 and t48. It should be noted that the 3D interlock weave of the core extends to the extreme half-layers tl, t48 of the hides in order to link these half-layers to those of the core.

[0045] In the example described here, strips of fiber mat 30 are used in the weft layers present in the core 2103 of the fibrous texture 200. The strips of fiber mat 10 are used as bulking elements in the half-layers t21 to t28. The strips of fiber mat 30 have a thickness of 2 mm (between 1 and 3 mm) and a width of 5 mm (between 1 and 8 mm), i.e., a cross-section or diameter of approximately 10 mm². All other weft yarns or strands present in the weft layers of the overweight part 203 have a count corresponding to a section lower than that of the strips 30. The overweight part 203 here includes yarns or strands 20 having respectively a count of 200 Tex, i.e. 0.5K (500 filaments) corresponding to an oval section of 1 mm x 0.15 mm.

[0046] Inserting the fiber mat strips 30 into the thickened portion 203 at the core weft layers of the fibrous texture allows for significant expansion or swelling of the fibrous texture. Without inserting fiber mat strips with a cross-section greater than the cross-section or count of the weft yarns or strands present in the thickened portion, it would be necessary to insert yarns or strands with a large cross-section to achieve the desired thickness, as is the case with prior art solutions. However, in this case, the fiber content in the thickened portion becomes too high and not compatible with optimal densification and mechanical properties. Indeed, if the fiber content is too high, it is more difficult to introduce a matrix precursor throughout the porosity of the fibrous reinforcement.Furthermore, if the fiber content is very high, the amount of matrix deposited will be low, which can degrade the mechanical properties of the resulting composite material.

[0047] In the example described here, the fibrous texture according to the invention is woven with yarns or strands of ceramic fibers such as silicon carbide, and the fiber mat used for the straps is made of discontinuous ceramic fibers such as silicon carbide. The fibers used in the yarns or strands used for weaving the fibrous texture, as well as the discontinuous fibers used for the fiber mat of the straps, may also, but not exclusively, be carbon fibers or oxide fibers such as alumina.

[0048] Once the weaving of the fibrous texture 200 in the blank 100 is complete, the fringe yarns are cut off the selvedge to extract the fibrous texture. The resulting fibrous texture 200, illustrated in [Fig. 3], is woven in a single piece. The thickened portion 203 has, in the thickness direction DE, a thickness E203 greater than the thickness E205 of the adjacent portion 205.

[0049] The next step, in a known manner, consists of shaping the fibrous texture 200 by compaction to form a fibrous preform ready to be densified. For this purpose, the fibrous texture is placed in a forming tool (not shown in Figure 1). [Fig. 3]) which includes, for example, first and second shells, each with a central cavity corresponding in part to the shape and dimensions of the blade to be produced. Once the forming tool is closed—that is, when the first and second shells are joined together with the fibrous texture positioned in the cavities that together define an internal volume with the shape of the blade to be produced—the forming tool is placed in a compaction press to be subjected to compaction pressure. The application of compaction pressure causes the first and second shells to come together, which allows both the fibrous texture to be compacted to a predetermined compaction ratio in order to obtain a predetermined fiber content and the shaping of the fibrous texture according to the profile of the blade to be manufactured.

[0050] A fibrous preform 500 is then obtained, the lower end of which has an overthickness portion 503 corresponding to the overthickness portion 203 of the fibrous texture 200 intended to form the blade root, extended by a decreasing thickness portion 504 corresponding to the portion 204 of the fibrous texture 200. The preform 500 also includes a blade portion 505 corresponding to the portion 205 of the fibrous texture 200 which extends along the direction DT between a leading edge preform portion 505a and a trailing edge preform portion 505b corresponding respectively to the edges 205a and 205b of the fibrous texture 200.

[0051] Once the fibrous preform 600 has been produced as described above, it is consolidated. In the example described here, the preform 600 is consolidated by depositing an interphase onto the surface of the fibers of said preform by chemical gas infiltration (CVI). For this purpose, the preform, held in a forming tool, for example made of graphite, is placed in a furnace or CVI installation in order to deposit an interphase onto the surface of the preform fibers.

[0052] The next step consists of impregnating the fibrous preform with a slurry using the injection molding process (also known as slurry casting or STM (slurry transfer molding)). For this purpose, and in a known manner, the consolidated fibrous preform is placed in a mold of a tooling into which a liquid loaded with refractory ceramic particles or particles of a refractory ceramic precursor is injected in order to penetrate the porosity of the fibrous preform.

[0053] The loaded liquid may, for example, be a slip containing refractory ceramic particles designed to enable the formation of a refractory ceramic matrix within the porosity of the fibrous preform. The slip may, for example, be a suspension of SiC powder in water.

[0054] During and after the injection of the slip, the liquid is drained or filtered through a piece of porous material so that the refractory ceramic particles are deposited by sedimentation in the porosity of the fibrous preform.

[0055] Once the injection and drainage steps have been carried out, a fibrous preform loaded with refractory ceramic particles, for example SiC particles, is obtained.

[0056] 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").

[0057] The densification of the fibrous preform can also be achieved, in a known manner, by gaseous means through chemical vapor infiltration of the matrix (CVI). The fibrous preform corresponding to the fibrous reinforcement of the blade to be produced is placed in a furnace into which a reactive gaseous phase is admitted. The pressure and temperature prevailing in the furnace and the composition of the gaseous phase are chosen so as to allow the diffusion of the gaseous phase within the porosity of the preform to form the matrix by deposition, at the core of the material in contact with the fibers, of a solid material resulting from the decomposition of a constituent of the gaseous phase or from a reaction between several constituents, unlike the pressure and temperature conditions specific to CVD (Chemical Vapor Deposition) processes which lead exclusively to deposition on the surface of the material.

[0058] The formation of a SiC matrix can be obtained with methyltrichlorosilane (MTS) giving SiC by decomposition of MTS.

[0059] The densification of the fibrous preform intended to form the fibrous reinforcement of the part to be manufactured can also be carried out in a manner known per se using the liquid-based process (CVL). The liquid-based process consists of impregnating the preform with a liquid composition containing a precursor of the matrix material. The precursor is usually in the form of a polymer, such as a high-performance epoxy resin, possibly diluted in a solvent. The preform is placed in a mold that can be sealed tightly with a cavity having the shape of the final molded blade. The mold is then closed, and the liquid matrix precursor (for example, a resin) is injected into the entire cavity to impregnate the entire fibrous portion of the preform.

[0060] The transformation of the precursor into a matrix, namely its polymerization, is carried out by heat treatment, generally by heating the mold, after removal of any solvent and crosslinking of the polymer, the preform always being kept in the mold having a shape corresponding to that of the part to be produced.

[0061] In the case of the formation of a ceramic matrix, the heat treatment consists of pyrolyzing the precursor to transform the matrix into a ceramic matrix depending on the precursor used and the pyrolysis conditions. For example, liquid ceramic precursors, particularly SiC, can be polycarbosilane (PCS) or polytitanocarbosilane (PTCS) type resins or polysilazane (PSZ).

[0062] In particular, for the formation of an organic matrix, the densification of the fibrous preform can be achieved by the well-known resin transfer molding (RTM) process. According to the RTM process, the fibrous preforms are placed in a mold having the external shape of the part to be produced. A thermosetting resin is injected into the internal space of the mold, which contains a fibrous preform. A pressure gradient is generally established in this internal space between the point where the resin is injected and the resin discharge ports in order to control and optimize the impregnation of the preform by the resin.

[0063] A densification combining liquid and gaseous route can also be used to facilitate implementation, limit costs and manufacturing cycles while obtaining satisfactory characteristics for the intended use.

[0064] At the end of the densification process of the fibrous preform, a part made of composite material is obtained comprising at least first and second parts adjacent with the first part having a thickness much greater than the first part.

[0065] In the examples described here, the composite material part corresponds to a gas turbine blade. Thus, the first part corresponds to a blade root while the second part corresponds to an aerodynamic profile.

[0066] The densification processes described above make it possible to produce, from the fibrous texture of the invention, mainly parts made of organic matrix composite material (CMO), carbon matrix composite (C / C) and ceramic matrix composite (CMC).

[0067] The fibrous preform and its manufacturing process according to the present invention can in particular be used to produce turbomachine blades with a more complex geometry, such as blades also comprising one or more platforms enabling the performance of functions such as flow sealing, anti-tipping, etc.

Claims

Demands

1. A method for manufacturing a fibrous preform for a part made of composite material, the method comprising at least: - the creation of a fibrous texture (200) by three-dimensional or multilayer weaving between a plurality of weft layers (tl-t48) comprising partly weft yarns or strands (202) and layers of warp yarns or strands (201), the fibrous texture (200) comprising at least first and second parts (203, 205) adjacent in a longitudinal direction (DL), the first part (203) having, in a thickness direction (De) perpendicular to the longitudinal direction, a thickness (E203) greater than the thickness (E2os) of the second part (205), - the shaping of the fibrous texture (200) to obtain a fibrous preform (500), characterized in that, during the weaving of the fibrous texture (200),strips (30), each consisting of a mat of fibres, are inserted into weft layers (t21-t28) of the first part (203).

2. A method according to claim 1, wherein the strips (30) made of a fiber mat are inserted into weft layers (t21-t28) located in the core (2103) of the first part (203).

3. A method according to claim 1 or 2, wherein each warp layer comprises the same number of yarns or strands, the yarns or strands present in the warp layers all having the same count.

4. A method according to any one of claims 1 to 3, further comprising the production of a fibre mat and cutting said fibre mat into strips (30).

5. A method according to claim 4, wherein the fibre mat is made from fibre from weaving scraps.

6. A method for manufacturing a part made of composite material comprising the following steps: - production of a fibrous preform in accordance with the method for manufacturing a fibrous preform according to claims 1 to 5, - densification of the fibrous preform.

7. Fibrous preform obtained in accordance with the process for manufacturing a fibrous preform according to claims 1 to 5.

8. Composite material part obtained in accordance with the process for manufacturing a composite material part according to claim 6.

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