METHOD FOR MANUFACTURING A COMPLEX PART MADE FROM A CERAMIC MATRIX COMPOSITE MATERIAL

Abstract

The invention relates to a method for manufacturing a part (10) made of a ceramic matrix composite material, comprising: - a step of producing a first preform (11), - a step of producing a second preform (12), - a step of plating one face of the second preform (12) against one face of the first preform (11) in an assembly zone (23), - a step of applying an autoclaving cycle to the "first preform (11)-second preform (12)" assembly so as to obtain adhesion between the first preform (11) and the second preform (12) in the assembly zone (23), - a step of applying a sintering cycle to the "first preform (11)-second preform (12)" assembly to consolidate a bond between the first preform (11) and the second preform (12) in the assembly zone (23) and obtain a One-piece component made of a ceramic matrix material. Figure for abbreviation: Figure 1c

Description

Title of the invention: METHOD FOR MANUFACTURING A COMPLEX PART MADE FROM A CERAMIC MATRIX COMPOSITE MATERIAL

[0001] The present invention relates to a method for manufacturing a complex part made of a ceramic matrix composite material. The invention finds a particularly advantageous, but not exclusive, application in the manufacture of an ejection cone or a primary nozzle for an aircraft engine equipped with a stiffener. The invention can also be implemented for the production of helicopter engine parts or any other type of part subjected to an environment of high mechanical and / or thermal stress.

[0002] The rear wing components of an aircraft engine are conventionally made of a monolithic metallic material. However, the increase in engine temperatures and the obsolescence of certain metallic materials are driving the use of ceramic matrix composite materials, known as oxide-on-oxide (CMC) materials. These materials comprise a fibrous reinforcement, for example, based on alumina (Al₂O₃), and a matrix, for example, based on alumina and containing a small proportion of silica.

[0003] These materials have the advantage of exhibiting very good oxidation resistance, good mechanical behavior at high temperatures, and low implementation cost. These materials can be used, for example, to manufacture a mixer for a dual-flow turbomachine that mixes a primary airflow (hot air) and a secondary airflow (cold air), an ejection cone that progressively expands the engine's exhaust gases, or a primary nozzle.

[0004] Generally, CMC material parts are manufactured independently of one another through successive operations of draping, autoclaving, sintering, and machining. The parts are then assembled using mechanical fasteners (rivets, bolted assemblies). These different techniques present weight constraints as well as dimensional and geometric requirements for achieving the connection between the parts. Indeed, since CMC materials have little expansion, it is necessary to incorporate complex mechanisms to compensate for the expansion of the fastening systems. Furthermore, when the fastening systems are located in the aerodynamic flow, a loss of aerodynamic performance is observed. There is also a risk of lightning strikes on parts intended for installation in an aircraft engine.

[0005] The invention aims to effectively remedy the aforementioned drawbacks by proposing a method for manufacturing a part made of a ceramic matrix composite material comprising: - a step of creating a first preform by draping at least one ply of composite material pre-impregnated with a ceramic matrix precursor, - a step of creating a second preform by draping at least one ply of composite material pre-impregnated with a ceramic matrix precursor, - a step of plating one face of the second preform against one face of the first preform in an assembly area, - a step involving the application of an autoclaving cycle to the "first preform-second preform" assembly in order to obtain adhesion between the first preform and the second preform in the assembly zone, - a step of applying a sintering cycle to the "first preform-second preform" assembly to consolidate a bond between the first preform and the second preform in the assembly area and obtain a one-piece part made of a ceramic matrix material.

[0006] The invention thus makes it possible, thanks to the bond between the two preforms created during the autoclaving and sintering steps, to eliminate or reduce the number of metallic fasteners in order to reduce the overall mass. The invention also makes it possible to assemble components in areas of limited accessibility for a conventional joint. In the specific case of an aeronautical component, the invention further improves aerodynamic performance in the area joined between the parts while reducing the risk of lightning strikes.

[0007] According to one embodiment of the invention, said method includes a step of setting up a retaining element to maintain a shape of the second preform during the autoclaving cycle.

[0008] According to one embodiment of the invention, the ply or plies of composite material pre-impregnated with a ceramic matrix precursor are automatically draped.

[0009] According to one embodiment of the invention, the ply or plies of composite material pre-impregnated with a ceramic matrix precursor are draped manually.

[0010] According to one embodiment of the invention, the ply or plies of composite material pre-impregnated with a ceramic matrix precursor comprise unidirectional fibers or a two-dimensional or three-dimensional fiber mesh.

[0011] According to one embodiment of the invention, said process includes a step of adding, before the autoclaving cycle, a fibrous ply impregnated with a ceramic matrix precursor at the level of the assembly zone between the first preform and the second preform.

[0012] According to one embodiment of the invention, said process includes a step of adding, before the autoclaving cycle, an interface strip made of a ceramic matrix precursor.

[0013] According to one embodiment of the invention, said process includes a step of dressing the first preform and the second preform for the autoclaving cycle.

[0014] According to one embodiment of the invention, the autoclaving cycle is carried out at a temperature between 60°C and 250°C and at a pressure between 5 and 25 MPa.

[0015] According to one embodiment of the invention, the sintering cycle is carried out at a temperature between 1000°C and 1300°C.

[0016] According to one embodiment of the invention, the first preform has a conical shape and the second preform is a stiffener disposed on an internal face of the first piece.

[0017] According to one embodiment of the invention, the stiffener has a section having a shape chosen from the following shapes: L, T, U.

[0018] The invention also relates to a part made of ceramic matrix composite material obtained by the process as previously defined.

[0019] The present invention will be better understood and other features and advantages will become apparent upon reading the following detailed description, which includes embodiments given by way of illustration with reference to the accompanying figures, presented by way of non-limiting examples, which may serve to complete the understanding of the present invention and the explanation of its implementation and, where appropriate, contribute to its definition, on which:

[0020] [Fig. 1a] [Fig. 1b] [Fig. 1e] [Fig. 1d] Figures 1a to 1d represent in a schematic diagram of the different stages of a manufacturing process for a complex part made of CMC material according to the invention;

[0021] [Fig.2] Fig.2 is a perspective view of an automated draping system suitable for use in implementing the process according to the invention;

[0022] [Fig. 3a] Fig. 3a is a perspective view of a first preform constituting a ejection cone of an aircraft engine;

[0023] [Fig. 3b] Fig. 3b is a perspective view of the second preform constituting a stiffener intended to be fixed on the ejection cone of the [Fig.3a];

[0024] [Fig. 3c] Fig. 3c is a perspective view of the ejection cone fitted with the stiffener arranged on its inner face before the autoclaving step.

[0025] It should be noted that the structural and / or functional elements common to the different embodiments may have the same reference numerals. Thus, unless otherwise specified, such elements have identical structural, dimensional and material properties.

[0026] Figures la-ld show the different stages of a manufacturing process for a complex part 10 made of ceramic matrix composite material.

[0027] As illustrated in [Fig. 1a], the process includes a step of producing a first preform 11 by draping at least one ply of composite material pre-impregnated with a ceramic matrix precursor. The ceramic matrix precursor may be loaded with ceramic powders. The first preform 11 constitutes, for example, an ejection cone or a primary nozzle of an aircraft engine.

[0028] As can be seen in [Fig. 3a], the first preform 11 with axis XI has a tubular shape, that is to say, it has a hollow shape of revolution. The first preform 11 has, for example, a hollow frustoconical shape with axis XL. The first preform 11 has a radially internal face 11.1 and a radially external face 11.2 with respect to the axis XL.

[0029] The process includes a step of producing, independently of the first preform 11, a second preform 12 by draping at least one ply 15 of composite material pre-impregnated with a ceramic matrix precursor. The second preform 12 constitutes, for example, a stiffener for the first preform 11. As can be seen in [Fig. 3b], the second preform 12 with axis X2 has a first hollow frustoconical portion 13. The first portion 13 extends axially with respect to the axis X2 from a first end of small diameter to a second end of large diameter of the preform 12. The second preform 12 has an annular collar 14 extending radially from the first end in the direction of the axis X2. The second preform 12 has an L-shaped cross-section. Alternatively, the second preform 12 may have a U-shaped or T-shaped cross-section.

[0030] Alternatively, the preforms 11,12 have a hollow cylindrical shape, shapes of revolution with curved faces, or any other shape suitable for the application.

[0031] A ply 15 comprises a fibrous reinforcement and a ceramic matrix precursor arranged between and around the fibers of the fibrous reinforcement. A ply 15 may have a thickness of between 100 and 400 micrometers. The fibrous reinforcement comprises, for example, fibers made of alumina or mullite. The fibrous reinforcement may comprise unidirectional fibers or a two-dimensional fiber mesh with weft and warp fibers, or a three-dimensional fiber mesh with fibers extending through the thickness of the fibrous reinforcement and providing a bond between the weft and warp fibers. The matrix precursor comprises alumina, a small proportion of silica, and organic components (solvent, plasticizer) that impart flexibility to the composite ply 15.Alternatively, the fibers of the fibrous reinforcement and the matrix precursor can be made from any other type of oxide suitable for the application.

[0032] The ply or plies 15 of composite material pre-impregnated with a ceramic matrix precursor can be automatically draped, in particular by a technique known as AFP (for "Automatic Fiber Placement" according to Anglo-Saxon terminology). As shown in [Fig. 2], according to this technique, a drill bit dispensing head 16 mounted on a robotic arm 17 and a mandrel 18 are capable of moving relative to each other along several degrees of freedom in rotation and / or translation. The drill bits, having a width between 5 and 25 mm, are deposited in strips 28, each strip 28 consisting of 1 to 16 drill bits. A ply 15 results from the covering of the draping surface of the workpiece around the mandrel 18. A ply 15 may have gaps or overlaps between the strips 28.

[0033] This technique is particularly well suited to unidirectional fiber plies 15. The fibers can be oriented at a variable angle relative to an axis of the mandrel 18. The plies 15 are deposited in several layers superimposed one on top of the other. It is possible to use a technical fabric 19 to facilitate the adhesion of a first layer of plies 15, as well as a technical fabric 20 made of a waterproof material that promotes the release of the preform 11, 12 from the mandrel 18.

[0034] Alternatively, the ply or plies 15 of composite material pre-impregnated with a ceramic matrix precursor are draped manually. This technique is particularly well-suited for two- or three-dimensional fiber-mesh plies 15. In this case, layers (ply 15) with dimensions on the order of magnitude of the part to be manufactured are draped.

[0035] The preforms 11,12 can be obtained by the same draping technique or different draping techniques, for example an AFP technique to produce one preform and a manual 2D or 3D draping technique to produce the other preform.

[0036] As illustrated in [Fig. 1b] and [Fig. 3c], the process includes a step of plating one face of the second preform 12 against one face of the first preform 11 in an assembly zone 23. In this case, an external face of the conical portion 13 of the stiffener is plated against the internal face 11.1 of the ejection cone 11.

[0037] As illustrated in [Fig.1e], the process includes a dressing step consisting of placing a technical fabric 21 on the internal and external faces of the first preform 11 and the second preform 12. The technical fabric 21 allows the evacuation of gases generated by the pre-firing of the ceramic matrix precursor during the autoclaving phase.

[0038] If necessary, a retaining element 22 is put in place to maintain the shape of the second preform 12 during the autoclaving cycle. In this case, It is possible to position an annular retaining element 22 having an external periphery in contact with the internal face of the ejection cone 11 and an axial face in contact with a face of the annular collar 14 turned on the opposite side to the frustoconical portion 13.

[0039] After placing a membrane 25 around the technical fabric 21 and the "first preform 11-second preform 12" assembly, an autoclaving cycle is applied with a vacuum under a pressure between 5 and 25 MPa and a temperature between 60°C and 250°C. The autoclaving cycle has a duration between 1h and 50h.

[0040] The autoclaving cycle allows adhesion between the first preform 11 and the second preform 12 in the assembly zone 23 due to the fining capacity of the matrices of the preforms 11, 12 in the fibrous reinforcements of the preforms 11, 12 located in the assembly zone 23.

[0041] The autoclaving cycle also makes it possible to increase a volumetric ratio of fibers in the plies 15 of the preforms 11, 12 due to the partial evacuation of the organic components contained in the precursor of the ceramic matrix.

[0042] As illustrated in [Fig. Id], the process includes a step of applying a sintering cycle to the "first preform 11-second preform 12" assembly to consolidate a bond between the first preform 11 and the second preform 12 in the assembly zone 23.

[0043] The sintering cycle can be carried out in a furnace 26 at a temperature between 1000°C and 1300°C. The sintering cycle can last between 5h and 300h.

[0044] Under the effect of heat, the grains of the ceramic matrix of the preforms 11, 12 bond together, which forms the cohesion between the two preforms 11, 12. During the sintering phase, the remaining organic components of the ceramic matrix precursor are burned.

[0045] At the end of the sintering cycle, a one-piece part 10 made of a ceramic matrix material is obtained. There is a continuity of material in the assembly zone 23 between the first preform 11 and the second preform 12. The one-piece part 10 has the following composition: ceramic fibers comprising between 40% and 55% by volume, ceramic matrix comprising between 20% and 40% by volume and porosity comprising between 15% and 30% by volume.

[0046] The process can be implemented with several parts in series on the same cycle or in parallel with one or more parts on several autoclaving or sintering cycles taking place simultaneously.

[0047] Preferably, the first preform 11 and the second preform 12 do not undergo an autoclaving cycle or a sintering cycle before the common autoclaving step of the two preforms 11, 12. In other words, the common autoclaving step of the two preforms 11, 12 occurs right after the draping step of the preforms 11, 12.

[0048] Alternatively, it is possible to assemble preforms 11, 12 at different stages of curing, for example, one preform obtained after the draping step and another autoclaved, or even sintered, preform. In this case, the advantage may be to use a sintered preform as a geometric reference for the assembly, thus limiting the need for support or shimming tools. Under this assumption, differences in behavior compared to the demolded preform may exist and lead to unsatisfactory results, particularly when using a preform that has already been sintered.

[0049] An alternative may consist of positioning a preform already draped and demolded on a draping tool to integrate it into the preform of the other preform directly during draping.

[0050] Another alternative is to add, before the autoclaving cycle, a fibrous ply 27, for example non-woven, impregnated with a ceramic matrix precursor at the joint zone 23 between the first preform 11 and the second preform 12 (see [Fig. 1b]). This fibrous ply 27 is impregnated with the same matrix precursor as the plies 15. Thus, the matrix of the bonding tape 27 can flow into the fibrous reinforcements on either side of the joint. Alternatively, the fibrous ply 27 can be replaced by an interface strip made of a ceramic matrix precursor.

[0051] Of course, the different features, variants and / or embodiments of the present invention can be combined with each other in various ways insofar as they are not incompatible or mutually exclusive.

[0052] Furthermore, the invention is not limited to the embodiments described above and provided solely by way of example. It encompasses various modifications, alternative forms, and other variants that a person skilled in the art may consider within the scope of the present invention, and in particular all combinations of the different modes of operation described above, which may be taken separately or in combination.

Claims

Demands

1. A method for manufacturing a part (10) made of a ceramic matrix composite material, characterized in that it comprises: - a step of producing a first preform (11) by draping at least one ply (15) of composite material pre-impregnated with a ceramic matrix precursor, - a step of producing a second preform (12) by draping at least one ply (15) of composite material pre-impregnated with a ceramic matrix precursor, - a step of plating one face of the second preform (12) against one face of the first preform (11) in an assembly zone (23), - a step of applying an autoclaving cycle to the "first preform (11)-second preform (12)" assembly so as to obtain adhesion between the first preform (11) and the second preform (12) in the assembly zone (23),- a step of applying a sintering cycle to the "first preform (11)-second preform (12)" assembly to consolidate a bond between the first preform (11) and the second preform (12) in the assembly zone (23) and obtain a one-piece part made of a ceramic matrix material.

2. A method according to claim 1, characterized in that it includes a step of setting up a retaining element (22) allowing a shape of the second preform (12) to be maintained during the autoclaving cycle.

3. Method according to claim 1 or 2, characterized in that the ply or plies 15 of composite material pre-impregnated with a ceramic matrix precursor are automatically draped.

4. A method according to any one of claims 1 to 3, characterized in that the ply or plies (15) of composite material pre-impregnated with a ceramic matrix precursor are draped manually.

5. A method according to any one of claims 1 to 4, characterized in that the ply or plies (15) of composite material pre-impregnated with a ceramic matrix precursor comprise unidirectional fibers or a two-dimensional or three-dimensional fiber mesh.

6. A method according to any one of claims 1 to 5, characterized in that it comprises a step of adding, before the autoclaving cycle, a fibrous ply (27) impregnated with a ceramic matrix precursor at the level of the assembly zone (23) between the first preform (11) and the second preform (12).

7. A method according to any one of claims 1 to 5, characterized in that it comprises a step of adding, before the autoclaving cycle, an interface strip made of a ceramic matrix precursor.

8. A method according to any one of claims 1 to 7, characterized in that it comprises a step of dressing the first preform (11) and the second preform (12) for the autoclaving cycle.

9. A method according to any one of claims 1 to 8, characterized in that the autoclaving cycle is carried out at a temperature between 60°C and 250°C and at a pressure between 5 and 25 MPa.

10. A process according to any one of claims 1 to 9, characterized in that the sintering cycle is carried out at a temperature between 1000°C and 1300°C.

11. A method according to any one of claims 1 to 10, characterized in that the first preform (11) has a conical shape and the second preform (12) is a stiffener disposed on an internal face of the first piece.

12. A method according to any one of claims 1 to 11, characterized in that the stiffener has a section having a shape chosen from the following shapes: L, T, U.

13. Part made of ceramic matrix composite material obtained by the process defined according to any one of the preceding claims.

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