WO2023089289A1

WO2023089289A1 - Method for obtaining a ceramic matrix composite part

Info

Publication number: WO2023089289A1
Application number: PCT/FR2022/052141
Authority: WO
Inventors: Julien André Roger MATEO; Aline Planckeel
Original assignee: Safran Ceramics
Priority date: 2021-11-22
Filing date: 2022-11-21
Publication date: 2023-05-25
Also published as: FR3129392B1; FR3129392A1

Abstract

The invention relates to a method for manufacturing a ceramic matrix composite part, the part exhibiting rotational symmetry, the method comprising: - a step of weaving a fibrous preform (30, 40', 40") by means of a contour weaving method on a mandrel; - placing the fibrous preform on a shaper (70, 73); - a shaping step; the profile defined by the mandrel being obtained by passing through the projection (10, 20) from one of the ends thereof, and: - at each cusp (101, 201, 202), creating a symmetry of the portion of the projection (10, 20) beyond the cusp with respect to the perpendicular to the axis of revolution (R) passing through the cusp; then, after having passed through the entirety of the projection; - proportionally decreasing the distance between each point of the profile (11, 21) thus obtained and the axis of revolution.

Description

Title of the invention: Process for obtaining a part made of composite material with a ceramic matrix.

Technical area

The invention relates to the field of ceramic matrix composite materials, and more specifically to a process for preparing part of a part made of ceramic matrix composite material having rotational symmetry.

Prior technique

Ceramic matrix composite materials (CMC materials) have good thermostructural properties, that is to say high mechanical properties which make them suitable for forming structural parts, and the ability to retain these properties at high temperatures.

Composite materials with a ceramic matrix are generally obtained by a first step of manufacturing a fibrous preform, in particular woven, corresponding to the shape of the desired part, then a second step of filling the preform with a matrix.

Nevertheless, these preparation methods require obtaining a fibrous preform whose shape corresponds to the shape of the final part, and the accessible parts are therefore limited to the geometries that can be obtained either by weaving or by draping.

These constraints on the shape of the part to be obtained impose that certain parts which it would be preferable to produce in composite material for reasons of performance or weight, are traditionally produced in metal, due to technical limitations of the weaving processes which do not do not make it possible to obtain preforms with suitable geometries.

This is particularly the case for parts whose geometry is axisymmetric and includes one or more cusp points. Indeed, when a cusp exists in an axisymmetric part, it is not possible to obtain a fibrous preform therefrom by conventional weaving or draping processes.

For the manufacture of the preforms of such parts, it is currently envisaged to prepare several plies of fabric and to connect the latter to each other by draping them.

Another solution for producing such parts in CMC is to make the preform by connecting together several revolving preforms.

This results in a step for forming the fibrous preform that is more complex due to the connections between the different parts. In addition, the junction points between the different fabrics can pose problems of inhomogeneity, in particular during the infiltration of the preform by a matrix.

The invention aims precisely to propose a method of manufacturing an axisymmetric preform comprising cusps which would not require connecting together several preforms.

Disclosure of Invention

The invention relates to a method of manufacturing a part made of composite material with a ceramic matrix, the part having a symmetry of revolution with respect to an axis (R) and whose projection in a plane (A) comprising the axis of revolution comprises one or more cusp point(s), defined as a point of the projection whose tangent is perpendicular to the axis of revolution and for which the projection does not cross the tangent, the method comprising at least the following steps: a step of weaving a fibrous preform by a contour weaving process and the winding of the fibrous preform on a mandrel of variable diameter, part of which has a predefined profile; the deployment of the fibrous preform on a shaper to the geometry of the part and comprising at least one turning step, for the place or places of the fibrous preform corresponding to cusps; a step of forming the fibrous preform deployed on the shaper to the geometry of the part, the predefined profile of the mandrel of variable diameter being obtained in the plane A by traversing the projection from one of its ends and: by carrying out at each cusp a symmetry of the part of the projection beyond the cusp with respect to the perpendicular to the axis of revolution (R) passing through the cusp; then, after having covered the entire projection, by carrying out a proportional reduction in the distance between each point of the profile thus obtained and the axis of revolution.

The method makes it possible to prepare fibrous preforms of axisymmetric parts also having cusps. In addition, the particular definition of the profile of the mandrel makes it possible to ensure that the preform can easily be woven. In particular, changes in mandrel diameter can create surfaces nearly perpendicular to the longitudinal direction of the mandrel. Such surfaces are difficult to weave, because the spacing of the warp threads called up by the mandrel becomes too great.

To make the weaving of these zones more reliable, it has been observed that the diameter of the mandrel is not specifically important and that the only thing that counts is that the diameter ratios are preserved between the projection of the preform and the weaving mandrel.

Thus, the proportional reduction of all the distances between the points of the profile of the mandrel and the axis of revolution, makes it possible to soften all the slopes when the diameter of the mandrel varies and makes it possible to weave these areas by reducing the angle formed. between the plane of the warp threads and the plane of the weft threads.

For example, the proportional reduction may be a reduction by a factor of between 1.1 and 2.5, and preferably between 1.8 and 2.2, or even by a factor of 2.

The fibrous preform of the part is woven by contour weaving (or “contour weaving” according to the English name of this weaving technique). The contour weaving method proposes to weave a piece on a mandrel whose diameter is variable. The mandrel is placed at the outlet of the loom and draws the warp threads, which are woven with the weft threads arranged in the perpendicular direction, and therefore in the direction of the longitudinal axis of the mandrel.

Contour weaving makes it possible to obtain, at the end of the weaving process, a fabric wrapped around a mandrel of variable diameter.

It is the choice of the diameter variation of the weaving mandrel, also called the predefined profile of the mandrel in this application, which makes it possible to obtain the desired piece by the contour weaving method. This choice makes it possible to obtain the preform or preforms of the part of revolution to be produced.

Weaving makes it possible to obtain a fabric wound around the mandrel, and it is necessary during a subsequent step to unroll the woven preform obtained, and to roll it up on a shaper reproducing the desired geometry for the final piece.

In one embodiment, the deployment of the fiber preform on the shaper can be achieved by winding the woven preform on a shaper. The final thickness of the desired preform can be obtained by rolling up several successive layers of preform on the former.

During this step of unwinding the fabric on the shaper, the points of the preform are turned over corresponding to the cusps. These reversals operated during the transfer between the mandrel and the shaper can be operated manually, or by means of contact surfaces forcing the reversal of the fabric, for example by presenting a 180° twisted shape causing the fabric to make a half-turn. on itself at the places corresponding to the cusps.

Carrying out the step by means of contact surfaces forcing the reversal of the fabric makes it possible to avoid any handling error and thus makes it possible to facilitate the process.

Once the preform has been rolled up on a shaper, the shaper can be closed by one or more counter-molds if necessary. A step of infiltration, impregnation or densification of the matrix can then be carried out in a conventional, for example by injecting the matrix under pressure through the fibrous preform or by gaseous densification.

In one embodiment, the ratio between the largest and the smallest diameter of the mandrel is less than or equal to 2.

The inventors have found that this maximum value for the difference in diameters makes it possible to prevent the take-up speeds of the warp threads during weaving from being too different between two parts of the mandrel and makes it possible to limit the warp/weft imbalances of the preforms thus produced.

In one embodiment, the mandrel comprises several repetitions of the predefined profile in the longitudinal direction of the mandrel, the method further comprising a cutting step subsequent to the weaving step, so that the preforms from the parts of the mandrel of profiles separate ones are separated before being deployed on the conformers.

In this embodiment, the repetition of several profiles in the longitudinal direction of the mandrel makes it possible to obtain several pieces in a single weaving step. Such a mandrel requires a cutting step before the fibrous preform is placed on the shaper in order to ensure that the preform corresponding to the profile is separated from that which follows it in the longitudinal direction of the mandrel, so that each can be placed on a separate conformer.

In this embodiment, the cutting step is a transverse cutting step, ie the fabric is cut in a direction perpendicular to the longitudinal direction of the mandrel.

The cutting step can be carried out at any time between the end of weaving and the deposition of the preform on a shaper.

For example, the cutting step can be carried out during the unwinding of the weaving mandrel, whether the preforms are then placed on formers or are wound again, for example on transport or storage rolls.

In another example, the cutting step can be carried out just before the deposition of the preforms on the shapers. Such a cutting step can be carried out by a cutting element arranged between two preforms of separate parts, for example when the preform is deployed on the shaper.

In one embodiment, between two different profiles, the mandrel can comprise a separation zone, that is to say a part of the mandrel which does not correspond to the profile and which makes it possible to ensure the junction between the two successive profiles .

In this embodiment, if necessary, the strip of fabric corresponding to the separation zone can be cut.

In one embodiment, the mandrel further comprises a part of predefined profile making it possible to obtain a second part having a symmetry of revolution with respect to an axis and its projection in a plane (A) comprising the axis of revolution comprises one or more cusp(s), the predefined profile of the mandrel of variable diameter being obtained in the plane A by traversing the projection from one of its ends and: by realizing at each cusp a symmetry of the part of the projection not yet traveled with respect to the perpendicular to the axis of revolution passing through the cusp point; then, after having covered the entire projection, by carrying out a proportional reduction in the distance between each point of the profile thus obtained and the axis of revolution; the method further comprising a cutting step subsequent to the weaving step, so that the preforms coming from the parts of the mandrel of distinct profiles are separated before being placed on the formers.

In this embodiment, the weaving mandrel makes it possible to obtain several preforms corresponding to several parts, which can, for example, be separated from each other by a cutting step before deployment on shapers. In this embodiment, it may be advantageous to have on the same mandrel several profiles allowing the manufacture of preforms which correspond to several parts of the same final part.

As before, the cutting step can be carried out at any time between the end of weaving and the deployment of the preform on the shapers.

For example, in a method of the invention, it is possible to use the same mandrel of variable diameter comprising a first predefined profile and a second predefined profile, the first and second parts obtained from the preform resulting from the first profile and that from the second profile allowing by meeting to form an aeronautical combustion chamber.

Of course, the invention is not limited to only two profiles in the longitudinal direction of the same mandrel, the number of profiles that can be arranged in the longitudinal direction of the same mandrel is chosen according to the size of each preform and the width of the loom.

For example, a mandrel can comprise 2 and 10 identical or different profiles in its longitudinal direction.

In one embodiment of the method, the weaving step is continued after obtaining a first fibrous preform on a mandrel of variable diameter so that the mandrel of variable diameter comprises, at the end of the weaving step , a plurality of preforms wound around the mandrel; and a cutting step in the longitudinal direction is carried out before the preforms are deployed on the formers.

This embodiment makes it possible to obtain, at the end of the weaving step, several preforms wound one after the other on the same mandrel. That is to say that the length of fabric wound on the weaving mandrel makes it possible to produce more than one fiber preform.

For example, it is possible to wind between 2 and 10 times the length of fabric needed to manufacture a preform around the same mandrel.

The cutting step can be carried out at any time between the end of the weaving step and before the deployment of the preforms on the shapers. For example, the cutting step can take place the first time the weaving mandrel is unwound, either to deploy the preforms on shapers or to roll them up on storage or transport rolls.

In such an embodiment, when the length of fabric corresponding to a single preform has been unwound from the weaving mandrel, a longitudinal cutting step is performed. A longitudinal cutting step is understood as a cutting step in the direction of the axis of rotation of the mandrel.

This embodiment makes it possible to further improve the weaving yields since the same mandrel can be used to manufacture several preforms.

This embodiment is compatible with an embodiment where the same mandrel comprises several profiles corresponding to identical or different preforms as described previously.

In this embodiment, it is possible to leave, between two consecutively woven preforms, a cutting margin, that is to say a weaving strip which does not belong to either of the two preforms, for example less than or equal to 1 cm, to ensure that the cutting step does not risk rendering a preform unusable.

In one embodiment, the forming step can be carried out by resin transfer molding or by consolidation, carried out by liquid or gaseous means.

In one embodiment, the part is part of a turbine engine combustion chamber.

The method of the invention in fact allows part of a combustion chamber to be produced from composite materials with a ceramic matrix. It is particularly advantageous to have a combustion chamber made of composite material with a ceramic matrix. Indeed, due to the constraints in terms of operating temperatures and chemical environment, the combustion chambers are usually made of a metal alloy. It is advantageous to have such parts made of composite materials with a ceramic matrix to improve combustion without degrading the performance of the combustion chambers. The invention makes it possible to produce a combustion chamber in composite material using preforms having symmetries of revolution.

For example, the preforms can be chosen from silicon carbide fibers, carbon fibers, alumina fibers, or mixtures of such fibers. The ceramic matrix can be chosen from alumina, mullite, pyrocarbon, or silicon carbide.

Brief description of the drawings

[Fig. 1] Figure 1 schematically represents the steps to obtain a profile of the mandrel obtained for a first part geometry.

[Fig. 2] FIG. 2 schematically represents the steps for obtaining a profile of the mandrel obtained for a second part geometry.

[Fig. 3] FIG. 3 schematically represents a step for unrolling a fibrous preform from a mandrel onto a former.

[Fig. 4] Figure 4 schematically shows a step of unwinding and cutting fiber preforms from a mandrel on two formers.

[Fig. 5] FIG. 5 schematically represents a step for placing a preform on a shaper.

[Fig. 6] FIG. 6 schematically represents a step for placing a preform on a shaper.

Description of embodiments

The invention is now described by means of figures making it possible to explain the invention but which should not be considered as restricting the latter.

As described above, the first step of the method is a step of weaving a preform on a mandrel 31 whose diameter is variable.

Figure 1 shows the steps required to define the profile 12 of the mandrel, from the projection 10 of an axisymmetric part, in a plane A comprising the axis of rotation R. The projection 10 of the coin includes a cusp 101.

To obtain the profile 12 of the mandrel, a first step is to obtain the intermediate profile 11 by realizing at the cusp 101 a symmetry of the part of the projection 10 beyond the cusp 101 with respect to the perpendicular to the axis of revolution R passing through the reversal point 101.

The profile 10' illustrates the initial trace of the profile 10, and makes it possible to identify the part beyond the cusp point 101 having undergone a symmetry.

The intermediate profile 11, recalled by the trace 11' then undergoes a proportional reduction, here by a factor of 2, of all the distances in the direction perpendicular to the axis of rotation R, and the final profile 12 is thus obtained. of the mandrel necessary to obtain the fibrous preform of a part whose projection is the initial curve 10.

Figure 2 illustrates the obtaining of the profile 22 of a mandrel necessary to weave the preform of a part whose projection 20 has two cusps 201 and 202.

In the case of FIG. 2, the intermediate profile 21 corresponds to a stepped shape which differs from the trace 20' of the initial projection 20. The latter undergoes two symmetries ensuring the obtaining of a profile no longer having a cusp .

The final profile of the mandrel 22 corresponds to the intermediate profile 21, recalled by the trace 21' having undergone a proportional reduction, here by a factor of 2, of all the distances perpendicular to the axis of revolution R.

Figures 1 and 2 illustrate the mandrel profiles 12, 22 of variable diameters obtained for the preparation of parts of different geometries.

However, as described above, the mandrel of a process is not limited to a single profile as described above. In particular, a mandrel can comprise a plurality of profiles, which are identical or different, so that contour weaving makes it possible to obtain several different parts. In general, in order to optimize the use of the looms, it is preferable that the mandrel 31, 41 has a length corresponding to the width of the loom, in order to reduce the losses of threads not allowing the obtaining a preform.

In order to optimize the subsequent steps of the method described above, when the mandrel comprises several profiles corresponding to preforms of different parts, spaces can be left between the profiles allowing the separate preforms to be cut.

In one embodiment, the parts of the profile of a mandrel parallel to the axis of revolution R can be lengthened, for example, by between 1% and 10% of their lengths relative to the profile of the desired preform.

This is not shown on the examples of profiles described in FIGS. 1 and 2, but slightly lengthening the parts of the profile of the mandrel parallel to the axis of revolution R makes it possible to reduce the stress generated at the level of the parts of the profile having a component perpendicular to the axis of rotation when the preform is deployed on a former from a mandrel whose diameter is reduced by half compared to the desired real profile.

In addition, it should also be noted that the direction in which the preform is obtained on the profile of the mandrel has no effect on the final part, and when a mandrel has several profiles corresponding to several times the preform of the same part , it is advantageous to arrange the profiles head to tail, since this avoids sudden variations in the diameters of the mandrel and the length of the mandrel serving as a junction between two successive parts is reduced.

Figure 3 illustrates the transfer of a preform 30 from a mandrel 31 to a shaper 32.

In the example presented, the shaper has a diameter twice as large as the mandrel, so that the preform deployed on the shaper has the desired size.

In one embodiment, the weaving mandrel 31 can be unwound onto another roll, for example and either a storage or transport roll. This which is described below for a storage roll also applies to a transport roll.

In a method of the invention, between the weaving step and the step of unfolding on a shaper, it is possible to carry out a storage step, by unwinding the weaving mandrel onto a storage roll.

For example, the storage roll may have the same profile as the weaving mandrel.

This step advantageously makes it possible to release the weaving mandrel, which can then be used again for weaving, and the downtime of the loom is thus reduced.

In addition, once placed on a storage roll, the preforms can be processed without risk of damaging the weaving mandrel.

Finally, it is possible to process a large number of preforms simply and more reliably when the latter are arranged on storage rolls; they can all be processed at the same time.

What is described concerning the deployment of a preform on a shaper applies equally well whether the preform comes from a weaving mandrel or from a transport or storage roller. For example, if a cutting step is necessary, the latter can either be carried out on leaving the weaving mandrel or on leaving the transport or storage roller.

Such a transport or storage roller is however not essential, and it is possible to use only the weaving mandrel for all the steps up to the deployment of the preform on the shaper. Using the weaving mandrel directly simplifies the process, as it is then no longer necessary to use transport or storage rollers. Of course, when only the weaving mandrel is used for all the stages of transport and/or processing of the preforms and/or of their storage before forming the latter, the weaving mandrel will be chosen so that it is not not damaged by the treatments applied to the preform. In an alternative embodiment, shown in Figure 4, in which the mandrel 41 comprises along its longitudinal direction several repetitions of a profile, the fabric can be separated into two distinct preforms 40' and 40" by a cutting element 47, each of the preforms then being called up by a different shaper 45, 46. Such an embodiment makes it possible, from a weaving mandrel 41 comprising a profile whose thickness allows the weaving of several preforms, to separate said preforms and to arrive at two shapers 45, 46 which each correspond to only one piece.

The shaper 45, 46 has the profile of the preform that is desired, and its diameter is therefore, as shown, twice as large as the diameter of the weaving mandrel 41.

Also in this embodiment, it is possible to unwind the preforms from the weaving mandrel 41 onto separate storage or processing rolls to obtain the same advantages as previously described. In this case, the deployment of the preforms from the storage or treatment rollers on the shapers will take place subsequently and possibly after one or more treatments of the preform and after transport and/or storage.

Of course, the invention is not limited to an initial mandrel 41 comprising only the repetition of two profiles allowing the manufacture of two identical preforms. In other embodiments, the mandrel can comprise more than two repetitions of the same profile, or even a succession of several identical or different profiles.

The shape of the shapers 32, 45, 46 is extremely schematic and will be shown more representatively in Figures 5 and 6. However, none of these figures should be interpreted in a limiting manner.

The forming process is described for example in FIG. 5 in the case of a preform having a single cusp.

A first part of the former 70 is prepared with the desired geometry for the final part. A preform 71, woven by a mandrel whose profile of variable diameter has been prepared as described above, is deployed on the shaper 70, and the necessary folds are made. In the example of FIG. 5, the general “C” shape of the shaper corresponds to the shape proposed in FIG. 1 for the profile 10. and as the preform is placed on the shaper.

During a subsequent step, a counter-mold 72 is arranged so that the preform 71 is sandwiched between the shaper 70 and the counter-mold 72.

The whole of the shaper 70, of the preform 71 and of the counter-mold 72 can be directly subjected to a process of impregnation, injection or densification of the preform, in order to obtain, after impregnation, injection or densification after the removal of the shaper 70 and the counter-mold 72 the part made of composite material with the desired ceramic matrix to the desired geometry.

FIG. 6 schematically represents a forming process for a preform having two cusps, with an “S” geometry similar to that proposed in FIG. 2 for profile 20.

The preform coming from a mandrel whose proposed profile corresponds to the curve 22, is first placed on a shaper 73 comprising a first cusp.

The preform 74 is unfolded as it is deployed on the shaper 73. A first counter-mold part 75 is then placed on the preform 74. As shown, the first counter-mold part 75 comprises a second cusp, on which the preform 74 is then unfolded. A second counter-mold part 76 is then added, and the whole of the shaper 73, of the preform 74 and of the counter-mold 75, 76 allows the impregnation, the injection or the densification of the preform 74 by a resin , an interphase or by the matrix. The part obtained after impregnation, injection or densification of the preform 74 and after removal of the shaper and the counter-mold 75, 76 corresponds to the part made of ceramic material obtained which directly has the desired shape. In one embodiment of the invention, it is possible to manufacture, on the same weaving mandrel, preforms of separate parts which, once assembled together, make it possible to obtain a more complex part.

Such an example can be represented by the combination of the parts obtained at the end of the processes represented in FIGS. 5 and 6, which make it possible to obtain by assembly a part having the geometry of a combustion chamber made of ceramic material with a composite matrix.

Claims

[Claim 1] Method of manufacturing a part made of composite material with a ceramic matrix, the part having a symmetry of revolution with respect to an axis (R) and whose projection (10, 20) in a plane (A) comprising the the axis of revolution (R) comprises one or more cusps (101, 201, 202), defined as a point of the projection (10, 20) whose tangent is perpendicular to the axis of revolution (R ) and for which the projection (10, 20) does not cross the tangent, the method comprising at least the following steps: a step of weaving a fiber preform (30, 40', 40") by a method of weaving outline and winding of the fibrous preform on a mandrel of variable diameter (31, 41) part of which has a predefined profile (12, 22); unfolding of the fibrous preform on a shaper (70, 73) with the geometry of the part and comprising at least one turning step, for the place(s) of the fibrous preform corresponding to the turning points; a step of forming the fiber preform deployed on the shaper to the geometry of the part, the predefined profile (12, 22) of the variable-diameter mandrel (31, 41) being obtained in the plane (A) by traversing the projection ( 10, 20) from one of its ends and: by realizing at each cusp (101, 201, 202) a symmetry of the part of the projection (10, 20) beyond the cusp with respect to the perpendicular to the axis of revolution (R) passing through the cusp point; then, after having covered the entire projection, by carrying out a proportional reduction in the distance between each point of the profile (11, 21) thus obtained and the axis of revolution.

[Claim 2] Manufacturing process according to claim 1 wherein the ratio between the largest and the smallest diameter of the mandrel is less than or equal to 2.

[Claim 3] Method of manufacture according to claim 1 or 2, in which the mandrel (31, 41) comprises several repetitions of the profile (12, 22) in the longitudinal direction of the mandrel, the method further comprising a step of cutting subsequent to the weaving step, so that the preforms (40', 40") from the parts of the mandrel of distinct profile are separated before being deployed on the shapers.

[Claim 4] Manufacturing process according to any one of Claims 1 to 3, in which the mandrel (31, 41) further comprises a part of predefined profile (12, 22) allowing the production of a second part having a symmetry of revolution with respect to an axis (R) and its projection in a plane comprising the axis of revolution (A) comprises one or more cusps (101, 201, 202), the predefined profile of the mandrel of variable diameter being obtained in the plane (A) by traversing the projection from one of its ends and: by realizing at each cusp (101, 201, 202) a symmetry of the part of the projection not yet traversed by relative to the perpendicular to the axis of revolution passing through the cusp; then, after having covered the entire projection, by carrying out a proportional reduction in the distance between each point of the profile thus obtained and the axis of revolution; the method further comprising a cutting step subsequent to the weaving step, so that the preforms (40', 40") coming from the parts of the mandrel of distinct profiles are separated before being deployed on the shapers. [Claim 5] Manufacturing process according to any one of claims 1 to 4, wherein the weaving step is continued after obtaining a first fiber preform (30, 40 ', 40 ") on a mandrel of variable diameter (31, 41) so that the variable diameter mandrel comprises, at the end of the weaving step, a plurality of preforms wound around the mandrel; and wherein a step of cutting in the longitudinal direction is carried out before the preforms are deployed on formers (70, 73). [Claim 6] Manufacturing process according to any one of claims 1 to 5, in which the forming step is carried out by resin transfer molding or by consolidation, carried out by a liquid or gaseous process. [Claim 7] A manufacturing method according to any one of claims 1 to 6, wherein the part is part of a turbomachine combustion chamber.

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