METHOD FOR ASSEMBLING TWO PARTS MADE OF A CERAMIC MATRIX COMPOSITE MATERIAL
The method addresses weight and performance issues in CMC part assembly by bonding CMC parts using pre-impregnated composite material, enhancing aerodynamic performance and reducing lightning strike risks.
Patent Information
- Authority / Receiving Office
- FR · FR
- Patent Type
- Applications
- Current Assignee / Owner
- SAFRAN CERAMICS SA
- Filing Date
- 2024-12-19
- Publication Date
- 2026-06-26
Abstract
Description
Title of the invention: METHOD FOR ASSEMBLING TWO PARTS MADE OF A CERAMIC MATRIX COMPOSITE MATERIAL
[0001] The present invention relates to a method for joining two parts made of a ceramic matrix composite material. The invention finds a particularly advantageous, but not exclusive, application in the manufacture of an ejection cone for an aircraft engine or a primary nozzle made in several parts.
[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 (SiO₂).
[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 parts are assembled using mechanical fasteners, such as rivets, or bolted connections. 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 low 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 assembling a first part made of ceramic matrix composite material and a second part made of ceramic matrix composite material comprising: - a step of producing the first part by draping at least one ply of composite material pre-impregnated with a ceramic matrix precursor, autoclaving of the first piece, then pre-consolidation of the first piece at a first pre-consolidation temperature lower than a final sintering temperature applied to the first and second pieces, - a step of producing the second part by draping at least one ply of composite material pre-impregnated with a ceramic matrix precursor, autoclaving the second part, then pre-consolidating the second part at a second pre-consolidation temperature lower than the final sintering temperature, - a step of draping, on an area of the first part, at least one ply of composite material pre-impregnated with a ceramic matrix precursor so as to obtain a draped area, - a step of plating the second piece onto the draped area of the first piece in order to obtain an assembled area in which the first piece and the second piece overlap each other at the draped area of the first piece, - a step of applying an autoclaving cycle to the "first piece-fold of the draped area-second piece" assembly in order to pre-cure the fold of the draped area, and - a step of applying a sintering cycle to the assembly "first piece-fold of the draped area-second piece" at the final sintering temperature to consolidate the area assembled between the first piece and the second piece.
[0006] The invention thus makes it possible, thanks to the bond between the two CMC parts created by means of the ply or layers of composite material pre-impregnated with a ceramic matrix precursor, to eliminate or reduce the number of metallic fasteners in order to reduce the overall mass. The invention also improves aerodynamic performance in the area joined between the parts while reducing the risk of lightning strikes in the case of an aeronautical component.
[0007] According to one embodiment of the invention, an overlap length between the first piece and the second piece expressed in millimeters is greater than a ratio between a desired tensile strength of the assembled area expressed in MegaPascals divided by a desired inter-laminar shear strength of the assembled area expressed in MegaPascals.
[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.
[0011] According to one embodiment of the invention, the ply or plies of composite material pre-impregnated with a ceramic matrix precursor comprise a two-dimensional fiber mesh or a three-dimensional fiber mesh.
[0012] According to one embodiment of the invention, said process includes a step of dressing the assembled area for the autoclaving cycle.
[0013] According to one embodiment of the invention, the autoclaving cycle is carried out at a temperature between 50°C and 250°C and at a pressure between 0.5 and 2.5 MPa.
[0014] According to one embodiment of the invention, the sintering cycle is carried out at the final sintering temperature between 1000°C and 1300°C.
[0015] The invention also relates to an assembly between a first part made of a ceramic matrix composite material and a second part made of a ceramic matrix composite material obtained by implementing the process as previously defined.
[0016] 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:
[0017] [Fig-1] Fig. 1 is a diagram of the different stages of an assembly process between two pieces in sintered CMC according to the invention;
[0018] [Fig.2a] [Fig.2b] [Fig.2c] [Fig.2d] [Fig.2e] Figures 2a to 2e schematically represent the different stages of an assembly process between two sintered CMC parts according to the invention after the production of a first part and a second part by draping, autoclaving and pre-consolidation;
[0019] [Fig.3] The [Fig.3] is a photograph of a cross-sectional view obtained by X-ray tomography in the thickness of an area assembled between two sintered CMC parts obtained by implementing the process according to the invention.
[0020] It should be noted that 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.
[0021] Fig. 1 is a diagram of the different stages of an assembly process according to the invention between a first part 10 made of ceramic matrix composite material and a second part 11 made of ceramic matrix composite material.
[0022] The process includes a step of producing the first part 10 by draping 101 of at least one ply of composite material pre-impregnated with a matrix precursor ceramic, autoclaving 102 of the first part 10, then pre-consolidation 103 of the first part 10 at a first pre-consolidation temperature Tpi lower than a final sintering temperature Tf applied to the first part 10 and the second part 11
[0023] The process also includes a step of producing the second part 11 by draping 104 of at least one ply of composite material pre-impregnated with a ceramic matrix precursor, autoclaving 105 of the second part 11, then pre-consolidation 106 of the second part 11 at a second pre-consolidation temperature Tp2 lower than the final sintering temperature Tf.
[0024] The draping step 101, 104 of each part 10, 11 is carried out by draping at least one ply of prepreg composite material. A ply consists of a thin strip, in particular between 50 and 350 micrometers, preferably between 100 and 300 micrometers, comprising a fibrous reinforcement and a ceramic matrix precursor arranged between and around the fibers of the fibrous reinforcement. The fibrous reinforcement comprises, for example, fibers of ceramic material, for example, an oxide such as alumina or mullite or other suitable aluminosilicate or ceramic. The fibrous reinforcement may include unidirectional fibers or a two-dimensional fiber mesh with weft and warp fibers or an interlock type weave for example 2.5D or 3D with a three-dimensional fiber mesh including fibers extending into the thickness of the fibrous reinforcement and ensuring a bond between the weft and warp fibers.The ceramic matrix precursor comprises a pre-ceramic resin based on a ceramic material, for example, an oxide such as alumina, mullite, or another aluminosilicate compound, a small proportion of silica, and organic components (solvent, plasticizer) to impart flexibility to the composite ply. Alternatively, the fibers of the fibrous reinforcement and the ceramic matrix precursor can be made from any other type of oxide suitable for the application. The composite ply pre-impregnated with a ceramic matrix precursor can be draped manually or automatically, notably using an AFP (Automatic Fiber Placement) technique.
[0025] The autoclaving step 102, 105 of each part 10, 11 is carried out under a pressure between 0.5 and 2.5 MPa (i.e. between 5 and 25 bar), preferably between 0.5 and 1.5 MPa (i.e. between 5 and 15 bar) and a temperature between 50 and 250°C. The duration of the autoclaving cycle is between 5 and 30 h.
[0026] The pre-consolidation step 103, 106 of each part 10, 11 is carried out at a consolidation temperature Tpi, Tp2 lower than the final sintering temperature Tf. The first consolidation temperature Tpi and the second temperature The consolidation temperatures Tp2 can be equal or different. Each consolidation temperature Tpi, Tp2 is, for example, equal to the final sintering temperature Tf minus a temperature between 50°C and 150°C.
[0027] The pre-consolidation step 103, 106 makes it possible to give a certain mechanical strength to the parts 10 and 11 which is lower than the mechanical strength obtained at the end of the sintering cycle but sufficient to allow the handling of the parts 10, 11 and then the draping of the plies 12.
[0028] The two parts 10, 11 can for example correspond to two parts of an ejection cone or two parts of a primary nozzle of an aircraft engine.
[0029] In this case, as illustrated in [Fig. 2a], the first part 10 with axis XI and the second part 11 with axis X2 each have a tubular shape, that is to say, they each have a hollow shape of revolution. The first part 10 and the second part 11 each have, for example, a hollow frustoconical shape. The first part 10 has a radially internal face 10.1 and a radially external face 10.2 with respect to the axis XL. The second part 11 has a radially internal face 11.1 and a radially external face 11.2 with respect to the axis X2.
[0030] Alternatively, parts 10 and 11 have a hollow cylindrical shape, shapes of revolution with curved faces, or any other non-tubular shape suitable for the application.
[0031] As illustrated in [Fig. 2b], the process includes a draping step 107, on an area of the first part 10, of at least one ply 12 of composite material pre-impregnated with a ceramic matrix precursor so as to obtain a draped area 13. The draped area 13 is disposed on the side of a smaller diameter end of the first part 10. The draped area 13 is disposed on the external face 10.2 of the first part 10. The draped area 13 extends over 360 degrees around the first part 10. In the case of parts not having rotational symmetry, the draped area 13 does not extend over 360 degrees.
[0032] A ply 12 consists of a thin strip, in particular between 50 and 350 micrometers, preferably between 100 and 300 micrometers, comprising a fibrous reinforcement and a ceramic material matrix precursor disposed between and around the fibers of the fibrous reinforcement.
[0033] The fibrous reinforcement comprises, for example, fibers made of ceramic material, for example, an oxide such as alumina or mullite or other suitable aluminosilicate or ceramic. The fibrous reinforcement may comprise unidirectional fibers or a two-dimensional fiber mesh with weft and warp fibers or an interlock weave, for example, 2.5D or 3D with a mesh of three-dimensional fibers comprising fibers extending into the thickness of the fibrous reinforcement and ensuring a bond between the weft fibers and the warp fibers.
[0034] The ceramic material matrix precursor comprises a pre-ceramic resin based on a ceramic material, for example an oxide such as alumina, mullite, or another aluminosilicate compound, a small proportion of silica, and organic components (solvent, fluidizer) to impart flexibility to the composite material ply 12. Alternatively, the fibers of the fibrous reinforcement and the ceramic matrix precursor can be made from any other type of oxide suitable for the application.
[0035] The ply or plies 12 of composite material pre-impregnated with a ceramic matrix precursor can be automatically draped, in particular by an AFP (Automatic Fiber Placement) technique. According to this technique, a fiber dispensing head mounted on a robotic arm and a mandrel on which the first part 10 is placed are capable of moving relative to each other along several degrees of freedom in rotation and / or translation, so as to automatically deposit at least one layer of fibers around the first part 10 to form at least one ply. This technique is particularly well suited to plies 12 with unidirectional fibers.
[0036] Alternatively, the ply or plies 12 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 12.
[0037] As illustrated in [Fig.2c], the process includes a step of plating 108 of the second part 11 onto the draped area 13 of the first part 10 so as to obtain an assembled area 15 in which the first part 10 and the second part 11 overlap at the draped area 13 of the first part 10. The first part 10 and the second part 11 overlap axially with respect to each other. For this purpose, the first piece 10 is inserted by its smaller diameter end inside the larger diameter end of the second piece 11 so that a part of the inner face 11.1 of the second piece 11 covers a part of the outer face 10.2 of the first piece 10 at the draped area 13. The first piece 10 and the second piece 11 are then coaxial with respect to each other.
[0038] An overlap length L between the first part 10 and the second part 11 is sufficient for the inter-laminar shear strength to transfer the tensile load applied to the assembly of the two parts 10 and 11.
[0039] Advantageously, the overlap length L between the first part 10 and the second part 11, expressed in millimeters, is greater than a ratio between a hold The desired tensile strength of the assembled zone 15, expressed in MegaPascals, is divided by the desired interlaminar shear strength of the assembled zone 15, also expressed in MegaPascals. Following an example of process implementation, for a tensile strength of the assembled zone 15 of 250 MPa and a shear strength of the assembled zone 15 of 20 MPa, an axial overlap length L between the first part 10 and the second part 11 of at least 75 mm is required.
[0040] As illustrated in [Fig. 2d], the process includes a dressing step 109 of the assembled area 15. The dressing step consists of placing at least one technical fabric 17 on the inner periphery of the assembled area 15 and on the outer periphery of the assembled area 15. The technical fabric(s) 17 may be of different types. Their role is to drain any excess matrix initially present in the prepreg fabric, and to allow solvent evacuation, ultimately reducing the porosity of the ply(ies) in the assembled area 15 while ensuring a good bond between the parts 10, 11 and the ply 12 of the draped area 13.
[0041] After placing a membrane 18 or any other flexible compaction system such as a tarpaulin around the technical fabric 17 and the assembly "first piece 10-fold 12 of the draped area 13-second piece 11", an autoclaving cycle is applied in a step 110 under a pressure between 0.5 and 2.5 MPa (i.e., between 5 and 25 bar), preferably between 0.5 and 1.5 MPa (i.e., between 5 and 15 bar) and a temperature between 50 and 250°C. By way of example, the autoclaving cycle may last between 5 and 30 hours.
[0042] The autoclaving cycle allows the matrix of the freshly draped ply 12 to creep into the porosity of the pre-consolidated CMC parts 10, 11. This improves the mechanical bond between the ply 12 of the draped area 13 and the parts 10, 1 and therefore the mechanical performance of the assembly.
[0043] As illustrated in [Fig. 2e], the process includes a step 111 of applying a sintering cycle to the assembly "first part 10-fold 12 of the draped area 13-second part 11" to consolidate the assembled area 15 between the first part 10 and the second part 11. The sintering cycle can be carried out in a furnace 19 at a temperature between 1000°C and 1300°C, and can include lower temperature stages, for example, between 200°C and 600°C. By way of example, the sintering cycle lasts between 5 and 30 hours. It is possible to adjust the time / temperature combination of the last stage to obtain the same or nearly the same material integrity of the final assembly.
[0044] Under the effect of heat, the grains of the ceramic matrix of parts 10, 11, as well as the grains of the matrix of the fold 12 of the draped zone 13, fuse together, forming cohesion between the two parts 10 and 11. During the sintering cycle, the organic components of the matrix precursor undergo pyrolysis. At the end of the process, an assembly of parts 10-11 is obtained having, including in the assembled area 15, a volume percentage of fibers between 35% and 55%, preferably between 40% and 50%, a volume percentage of matrix between 30% and 40%, preferably between 32% and 37%, and a volume percentage of porosity less than 30%, preferably less than 25% and even more advantageously as low as 20%.
[0045] The process can be implemented with several assemblies of parts 10,11 in series on the same cycle or in parallel with one or more assemblies of parts on several autoclaving or sintering cycles taking place simultaneously.
[0046] Figure 3 is a cross-sectional photograph obtained by X-ray tomography through the thickness of the bonded area 15 between the two sintered CMC parts 10 and 11 obtained after the sintering cycle. This photograph highlights the sound material condition of the bond between the two parts 10-11, free from delamination, which gives the assembly good mechanical strength.
[0047] It should be noted that the different draping steps mentioned for making the first part 10, the second part 11 and the draped area 13 can be carried out using the same technique or different techniques.
[0048] The different autoclaving stages of the first part 10, the second part 11 and the assembly "part 10-fold 12-part 11" can be carried out in an analogous way with identical or close temperature and pressure parameters.
[0049] 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.
[0050] 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 assembling a first part (10) made of a ceramic matrix composite material and a second part (11) made of a ceramic matrix composite material, characterized in that said method comprises: - a step of producing the first part (10) by draping at least one ply of composite material pre-impregnated with a ceramic matrix precursor, autoclaving the first part (10), then pre-consolidating the first part (10) at a first pre-consolidation temperature (Tpi) lower than a final sintering temperature (Tf) applied to the first part (10) and the second part (H), - a step of producing the second part (11) by draping at least one ply of composite material pre-impregnated with a ceramic matrix precursor, autoclaving the second part (11), then pre-consolidating the second part (11) at a second pre-consolidation temperature lower than the final sintering temperature (Tf),- a draping step, on an area of the first part (10), of at least one ply (12) of composite material pre-impregnated with a ceramic matrix precursor so as to obtain a draped area (13), - a plating step of the second part (11) onto the draped area (13) of the first part (10) so as to obtain an assembled area (15) in which the first part (10) and the second part (11) overlap each other at the draped area (13) of the first part (10), - a step of applying an autoclaving cycle to the assembly "first part (10)-ply (12) of the draped area (12)-second part (11)" so as to pre-bake the ply (12) of the draped area (13), and - a step of applying a sintering cycle to the assembly "first part (10)-fold (12) of the draped zone (13)-second piece (11)" at the final sintering temperature (Tf) to consolidate the assembled zone (15) between the first piece (10) and the second piece (11).
2. A method according to claim 1, characterized in that an overlap length (L) between the first part (10) and the second part (11), expressed in millimeters, is greater than a ratio between a desired tensile strength of the assembled zone (15) expressed in MegaPascals divided by a desired inter-laminar shear strength of the assembled zone (15) expressed in MegaPascals.
3. A method according to claim 1 or 2, characterized in that the ply or plies (12) of composite material pre-impregnated with a ceramic matrix precursor are automatically draped.
4. A method according to claim 1 or 2, characterized in that the ply or plies (12) 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 (12) of composite material pre-impregnated with a ceramic matrix precursor comprise unidirectional fibers.
6. A method according to any one of claims 1 to 4, characterized in that the ply or plies (12) of composite material pre-impregnated with a ceramic matrix precursor comprise a two-dimensional fiber mesh or a three-dimensional fiber mesh.
7. A method according to any one of claims 1 to 6, characterized in that it comprises a step of dressing the assembled area (15) for the autoclaving cycle.
8. A method according to any one of claims 1 to 7, characterized in that the autoclaving cycle is carried out at a temperature between 50°C and 250°C and at a pressure between 0.5 and 2.5 MPa.
9. A method according to any one of claims 1 to 8, characterized in that the sintering cycle is carried out at the final sintering temperature between 1000°C and 1300°C.
10. Assembly between a first part (10) made of a ceramic matrix composite material and a second part (11) made of a ceramic matrix composite material obtained by implementing the process defined according to any one of the preceding claims.