Method for manufacturing a complex-shaped part made of a ceramic matrix composite material

Abstract

The invention relates to a method for manufacturing a part (10) made of a ceramic matrix composite material, the method comprising: • - a step of producing a first preform (11); • - a step of producing a second preform (12); • - a step of pressing a face of the second preform (12) against a face of the first preform (11) in a joining zone (23), the first preform (11) and the second preform (12) not having undergone any autoclaving cycle or sintering cycle before carrying out 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 joining zone (23); • - a step of applying a sintering cycle to the "first preform (11) - second preform (12)" assembly in order to consolidate a connection between the first preform (11) and the second preform (12) in the joining zone (23) and obtain a one-piece part made of a ceramic matrix ceramic material.

Description

DESCRIPTION TITLE: 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 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 environments with high mechanical and / or thermal stresses.

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

[0003] These materials offer the advantage of excellent oxidation resistance, good mechanical behavior at high temperatures, and low implementation costs. They can be used, for example, to create a mixer for a turbofan engine 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, parts made of CMC material are produced independently through successive operations of draping, autoclaving, sintering, and machining. The parts are then assembled using mechanical fasteners (rivets, bolted assemblies). These different These techniques present mass constraints as well as dimensional and geometric requirements for joining the parts. Indeed, since CMC materials have low expansion, complex mechanisms are necessary to compensate for the expansion of the fastening systems. Furthermore, when 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 overcome the aforementioned drawbacks by proposing a method for manufacturing a part made from 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 stages, to eliminate or reduce the number of metallic fasteners in order to reduce the overall mass. The invention also allows for assembly in areas with 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 process 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 part.

[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. 1c] [Fig. 1d] Figures 1a to 1d schematically represent the different stages of a manufacturing process for a complex part made of CMC material according to the invention;

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

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

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

[0024] [Fig. 3c] Figure 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 structural and / or functional elements common to the different embodiments may have the same references. Thus, unless otherwise specified, such elements have identical structural, dimensional, and material properties.

[0026] Figures 1a-1d show the different stages of a manufacturing process for a complex part 10 made of ceramic matrix composite material.

[0027] As illustrated in Figure 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 can 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 Figure 3a, the first preform 11 with axis X1 has a tubular shape, that is, it has a hollow shape of revolution. The first preform 11, for example, has a hollow frustoconical shape with axis X1. The first preform 11 has a radially internal face 11.1 and a radially external face 11.2 with respect to axis X1.

[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 Figure 3b, the second preform 12, with axis X2, has a first hollow frustoconical portion 13. This first portion 13 extends axially with respect to 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 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, preforms 11, 12 have a hollow cylindrical shape, shapes of revolution with curved faces, or any other shape suitable for the application.

[0031] A 15-ply composite material comprises a fibrous reinforcement and a ceramic matrix precursor arranged between and around the fibers of the reinforcement. A 15-ply composite material can have a thickness ranging from 100 to 400 micrometers. The fibrous reinforcement may consist of alumina or mullite fibers. It can be unidirectional, a two-dimensional fiber mesh with warp and weft fibers, or a three-dimensional fiber mesh with fibers extending throughout the thickness of the reinforcement and bonding the warp and weft fibers. The matrix precursor contains alumina, a small proportion of silica, and organic components (solvent, plasticizer) to impart flexibility to the 15-ply composite material.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, notably by a technique known as AFP (Automatic Fiber Placement). As shown in Figure 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 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 stacked one on top of the other. A technical fabric 19 can be used to facilitate the adhesion of the 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 15 plies of pre-impregnated composite material (1) containing a ceramic matrix precursor are draped manually. This technique is particularly well-suited for 15 plies with two- or three-dimensional fiber mesh. In this case, layers (15 plies) 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 make one preform and a manual 2D or 3D draping technique to make the other preform.

[0036] As illustrated in Figure 1b and Figure 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 Figure 1c, 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 outer periphery in contact with the inner face of the ejection cone 11 and an axial face in contact with a face of the annular collar 14 facing away from 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 draw under a pressure of between 5 and 25 MPa and a temperature between 60°C and 250°C. The autoclaving cycle lasts between 1 and 50 hours.

[0040] The autoclaving cycle enables adhesion between the first preform 11 and the second preform 12 in the assembly zone 23 due to the creep 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 allows an increase in the volumetric rate of defibrates in the folds 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 Figure 1d, 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 5 and 300 hours.

[0044] Under the effect of heat, the grains of the ceramic matrix of the preforms 11, 12 weld 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 off.

[0045] At the end of the sintering cycle, a single-piece part 10 is obtained, made of a ceramic matrix material. There is a continuity of material in the assembly zone 23 between the first preform 11 and the second preform 12. The single-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 stage 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 reducing the need for support or shimming tools. Under this scenario, 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 be to position a preform already draped and demolded onto 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, to the assembly zone 23 between the first preform 11 and the second preform 12 (see Figure 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 bond. 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 associated with each other. others according to various combinations 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 variations that a person skilled in the art may envision within the scope of the present invention, and in particular all combinations of the different modes of operation described above, which may be considered 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), - the first preform (11) and the second preform (12) not having undergone any autoclaving cycle or sintering cycle before carrying out a step of applying an autoclaving cycle to the assembly "first preform (11)-second preform (12)" 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. Method according to claim 1, characterized in that it comprises a step of setting up a retaining element (22) allowing to maintain a shape of the second preform (12) 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. 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.

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