• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    A method of manufacturing an acoustic attenuation panel comprising two outer skins (4, 6) made of a ceramic matrix composite material containing fibrous reinforcement, assembled on each side of a central honeycomb core (2) having walls (10) forming acoustic cavities made by at least partial electrochemical conversion of aluminum to aluminum oxide, this method comprising a step of insertion in acoustic cavities of a fugitive filling material leaving free in each cavity, on each side against the skin, an annular space around this cavity, and a sintering step of the composite material achieving an elimination of the fugitive material, with a filling by the composite material spaces around the cavities.
    公开号:FR3039147A1
    申请号:FR1557083
    申请日:2015-07-24
    公开日:2017-01-27
    发明作者:Arnaud Delehouze；Sylvain Sentis；Bertrand Desjoyeaux
    申请人:Aircelle SA；
    IPC主号:
    专利说明:

    The present invention relates to the field of acoustic attenuation panels, in particular intended to equip the hot zones of gas ejection of an aircraft turbojet engine. The invention relates more specifically to a method of manufacturing an acoustic attenuation panel in a ceramic matrix composite material, as well as an acoustic attenuation panel obtained with such a method, and an aircraft turbojet engine comprising a panel of acoustic attenuation according to the invention.
    The turbojet engines comprise aerodynamic guide surfaces for the flow of hot ejected gases, which can be subjected to high temperatures that can exceed 600 ° C., and in some cases reach 1000 ° C.
    To reduce the noise emitted by the turbojet in operation, it is known to produce aerodynamic guide surfaces with acoustic metal panels or non-oxide ceramic matrix composite material comprising a sandwich-type structure composed of an encapsulated core material. between two skins. The central core has transverse walls forming a large number of closed cells, which may in particular have a honeycomb shape.
    The front skin facing the sound source, has gas passages formed by micro-perforations, opening into resonant cavities formed by the closed cells of the central core, to form Helmhoitz resonators performing attenuation of acoustic emissions emitted by the turbojet.
    Acoustic panels of the prior art pose different problems. Mass is relatively important. In addition, it has temperature limitations that can be achieved, especially in turbojets. It also has limitations on the exposure time in some environments.
    It is known as an alternative to produce the ceramic matrix composite sandwich structure "CMC", with a ceramic that is not an oxide. This material is both strong and lightweight. However, it has limitations on the duration of exposure in some environments. In addition, the manufacture of a central core and skins in this material is very complex and expensive.
    The present invention aimed in particular at overcoming the drawbacks of the prior art, relates for this purpose to a method of manufacturing an acoustic attenuation panel comprising two outer skins made of ceramic matrix composite material containing a fiber reinforcement, assembled with each side of an alveolar central core having walls forming acoustic cavities made by at least partial electrochemical conversion of aluminum to aluminum oxide, this process being remarkable in that it comprises a step of insertion into acoustic cavities a fugitive filling material leaving free in each cavity, on each side against the skin, an annular space around this cavity, and a sintering step of the ceramic composite material providing elimination of the fugitive material, with a filling by the composite material of the spaces around the cavities.
    An advantage of this manufacturing process is that by adapting the material as well as the shapes of the fugitive material, during sintering, a protection preserving the internal volume of the cells is obtained, avoiding a deformation of the skins towards this volume and a flow. of the matrix in, which would reduce the volume of the cells by decreasing the acoustic performance of the panels.
    At the same time, it is ensured by the filling with the composite material of spaces around the cavities, the larger areas of adhesion between the skins and the central core greatly increasing the mechanical strength of the panel.
    The manufacturing method according to the invention can comprise one or more of the following characteristics, which can be combined with one another.
    Advantageously, the manufacturing method comprises an additional step intended to perform during the molding of the perforations of one of the skins of composite material. A large number of perforations are quickly obtained.
    This additional step may comprise the production of spikes on the fugitive filling material, in this same material, passing through a fibrous reinforcement of a skin.
    Alternatively the additional step may comprise the removal on the outer side of a fibrous reinforcement provided for a skin, a plate equipped with points passing through this reinforcement. These tips are made of fugitive material, or a material capable of withstanding the sintering step, in which case the inserts have a demoldable form.
    The manufacturing method can be used to make the skins dry fibrous reinforcements then receiving the matrix by filtration, or fibrous reinforcements pre-impregnated with a matrix.
    Advantageously, the fugitive material may be any material capable of disappearing during the sintering operation: the fugitive material may comprise one or more materials chosen from thermoplastic and thermosetting materials.
    Advantageously, the production of the acoustic cavities comprises a step of assembling aluminum lamellae together by means of hardening, crimping, welding or bonding with a preceramic adhesive. The invention also relates to an acoustic attenuation panel made of a ceramic composite material, produced with a method comprising any one of the preceding features.
    Advantageously, the aluminum of the walls of the acoustic cavities is totally converted to aluminum oxide.
    Advantageously, the connection of the ceramic composite material of the skins with the walls of the central core substantially forms a connection radius. The shape of a ray gives with little matter a high resistance.
    Advantageously, the two skins comprise a fibrous reinforcement of metal oxide and a matrix of metal oxide.
    In particular, the matrix and the fiber reinforcement of the skins may comprise at least two different ceramic materials. The local characteristics of the matrix are thus adapted according to the constraints.
    According to one embodiment, the central core has drainage passages between cavities. The central core may have on its sides slots for hanging on the skins. The invention further relates to an aircraft propulsion assembly (that is to say the assembly formed by a turbojet equipped with its nacelle, this assembly may include the engine pylon), the propulsion unit comprising one or more acoustic attenuation panels comprising any of the features defined above. The invention will be better understood and other features and advantages will emerge more clearly on reading the following description given by way of example, with reference to the appended drawings, in which: FIG. 1 is an overall view of FIG. an acoustic panel of composite material according to the invention; Figure 2 is a top view of the walls of the acoustic cavities of this panel, comprising a honeycomb-shaped structure; Figures 2a and 2b are detail views showing two modes of manufacture of this structure; Figures 3, 4 and 5 show variants of these walls; Figure 6 is a front view showing a method of producing this panel; Figure 7 is a detailed view of the connection between a skin and a partition; Figure 8 shows a mechanical assembly of this panel; Figure 9 shows a first method of perforating the upper skin; and Figure 10 shows a second method of perforating the upper skin.
    FIG. 1 shows an acoustic panel comprising a central core 2 of constant or variable thickness, comprising transversely arranged walls delimiting a large number of juxtaposed acoustic cavities.
    The acoustic panel receives on a side conventionally called a rear skin sealed back side 4, and the front side intended to be turned towards the sound source, a front skin 6 having a large number of small perforations 8 opening in principle in all acoustic cavities.
    The skins 4, 6 are made of ceramic matrix composite material "CMC", comprising ceramic material fibers embedded in a matrix also made of ceramic material. The fibers may be long or short fibers. For the fibers and the matrix it is possible in particular to use metal oxides.
    Figure 2 shows the walls 10 arranged transversely in the panel, forming hexagonal resonant cavities 12 arranged in a honeycomb shape. Alternatively the cavities may have other shapes.
    The walls 10 of the cavities 12 are formed in a metal converted by a ceramic electrochemical process having a high melting point. For this purpose aluminum is used which is converted into aluminum oxide or alumina, in order to obtain a structure having a resistance compatible with the method of producing the sandwich panel, in particular the temperature for sintering ceramic matrix skins. . It should be noted that the melting temperature of the aluminum oxide is greater than 2000 ° C.
    In addition, the structure must withstand the different physicochemical constraints in the targeted applications, in particular in the case of aerodynamic guide surfaces for the flow of hot gases from turbojets.
    The method of manufacturing the structure of the central core 2 is as follows.
    Aluminum foils are assembled together by various methods such as work hardening, crimping, friction welding, or bonding with a preceramic adhesive. The shaping of the core material to the shape of the part is performed either prior to this assembly or consecutively.
    The electrochemical treatment of the structure is then carried out, which gives a conversion to aluminum oxide with a swelling of the volume.
    After partial conversion of the aluminum lamellae to alumina, as shown in FIG. 2a, a residual aluminum layer 14 which has not been converted into aluminum oxide is obtained.
    As shown in FIG. 2b, after a total conversion of the aluminum lamellae into alumina, a continuity of the alumina layer at the location of the assembly joints of the aluminum lamellae ensuring the mechanical strength of the material of the aluminum is obtained. soul.
    The shape and dimensions of the resonant cavities 12 may be varied, especially in width and height. We can have a different contour of the hexagonal shape. The characteristics of the resonant cavities can also be varied on the same panel, depending on the location. These different characteristics are adapted to meet in particular at each location the acoustic attenuation needs and the desired mechanical strength.
    Figure 3 shows a variant of the walls 10 of the cavities 12, having at the base of each side of the walls a rectangular cut in this example, forming a drainage passage 20 between two cavities.
    The drainage passage 20 has a height sufficient to maintain a passage between the cavities 12 once the skin is assembled on these walls 10, so as to drain a liquid entering these cavities in progress when the panel is used. Alternatively the drainage holes may have other shapes.
    Alternatively, when the ceramic matrix is infiltrated, these holes are previously filled by the insertion of fugitive filling material. These volumes of fugitive filling material can be integrated into those used to fill the volumes left free by the cavities of the core material.
    FIG. 4 shows a variant of the walls 10 of the cavities 12, comprising at the top of each face of the walls a series of small rectangular cutouts in this example, forming crenels 22, designed to ensure penetration into the skin arranged opposite, in order to obtain a better mechanical anchoring of this skin on the central core 2.
    FIG. 5 shows a central core 2 combining the two previous variants, having below the drainage passages 20 and above the crenellations 22.
    In addition one can realize all combinations of these variants, including for example crenellations 22 on both sides of the central core 2.
    Figure 6 shows a method of manufacturing acoustic panels, by filtering the matrix in the fibers.
    A first ceramic fiber reinforcement 34 is deposited in a mold 38.
    The central core 2 is then deposited, which has previously received in each cavity 12 a fugitive filling material 30 filling the entire volume from one side to the other and, where appropriate, the drainage holes. In a variant, the cavities 12 can be filled after this removal of the central core 2.
    The filling material 30 of each cavity 12 has on each side a connecting radius R forming the contour of the cavity, connecting the horizontal faces with the vertical faces of this material. The connecting radius R forms the equivalent of a convex meniscus on each side of the filling material 30.
    In this way there remains for each side of the cavity 12 a small space forming its contour, between the walls 10 and the horizontal plane receiving a skin 4, 6.
    Finally, the second reinforcement of dry ceramic fibers 36 is deposited, then an upper pressing means is put in place to clamp the stack on the central core 2.
    Filtration of the ceramic matrix in the two fiber reinforcements 34, 36 is then carried out by the powdered ceramic material forming a slip carried by a fluid which is a vector for the addition of the powders, and then drying to remove this fluid, or polymerization in the case where the final ceramic matrix is provided by a preceramic resin. In particular, a fluid compatible with the fugitive filling material 30 is chosen so as not to mix or dissolve.
    In particular, the matrix and the fiber reinforcement of the skins may comprise at least two different ceramic materials to adapt the local characteristics of this matrix according to the constraints.
    Finally, a temperature sintering of the matrix is performed to aggregate the entire matrix and fibers, and to assemble with the central core 2.
    The fugitive filling material 30 is chosen to obtain its elimination, at least partial and preferably total, during the sintering operation in temperature, in particular by combustion, melting, oxidation, sublimation, evaporation. In particular, the fugitive material can be any material capable of disappearing during the sintering operation: one can use in particular one or more materials chosen from thermoplastic plastics (such as polyethylene), thermosetting plastics (for example epoxy-based example), or low-melting metals (for example based on aluminum, lead or tin).
    The skins are chosen to allow during this operation a passage to the outside of the filling material 30, to let it escape.
    The fugitive filling material 30 avoids collapse of the outer skins in the cavities 12 in the case of preimpregnated fibrous reinforcements. In the case of filtration, it also avoids filling the cavities 12 with the matrix.
    It will be noted that, thanks to the upper pressing of the stack on the central core 2, a matrix filling of all the available volumes is obtained, in particular spaces left free by the connecting radii R on the turn of each cavity. .
    FIG. 7 shows the matrix of the skin 4 then coming for each side of the panel, covering the ends of each face of the walls 10 with a radius R identical to that of the fugitive filling material 30, which forms a large distance. contact surface between this matrix and the central core 2. A very strong adhesion between the skins 4, 6, and this central core 2 is obtained.
    Alternatively, a method of manufacturing acoustic panels may be used by using preimpregnated fibrous reinforcements for making the skins 4, 6.
    The first pre-impregnated reinforcement 34 is then deposited in the mold 38, then the central core 2 containing the filling material 30, or receiving this material after, and finally the second pre-impregnated reinforcement 36. The sintering operation remains similar, with an equivalent function for the filling material, avoiding a local depression of the skins in the cavities 12, and ensuring a large contact surface with the walls 10 thanks to the spaces left free by the connecting rays R.
    In addition, a thin layer of preceramic adhesive can be deposited between the fibrous reinforcements 34, 36 and the central core 2, which improves the bonding.
    Alternatively one can use a method of manufacturing acoustic panels using consolidated or already sintered skins, which are glued to the central core 2 by an intermediate preceramic glue coating which is then polymerized.
    For this process the temporary filling material 30 fulfills the same role, avoiding a filling of the cavities 12 by the glue, and by forming a large contact surface with the walls 10 thanks to the spaces left free by the connecting radii R of this material.
    FIG. 8 additionally presents a mechanical assembly, by a screw 40 having a wide head, which clamps the stack of the components of the panel by means of a nut 42 placed below, resting on a large surface.
    In particular, it is possible to reinforce the central core 2 at the level of the clamping screw 40 by filling, to avoid crushing the panel at this point. Alternatively any other clamping means may be used.
    Figure 9 shows a first method of making the perforations on the upper skin 36 during the manufacture of the panel.
    At the top of the filling material 30 are placed in each cavity 12, upwardly facing tips 50 formed of a material which is eliminated during the sintering of the ceramic material. When removing the upper fibrous reinforcement 36, which may be pre-impregnated with the ceramic matrix, or subsequently receive this matrix by filtration, the tips 50 pierce this reinforcement and pass through it completely.
    After the sintering operation, the tips 50 disappear leaving in the upper skin equivalent perforations.
    Figure 10 shows a second method of making the perforations on the upper skin 36.
    After having completed the stacking of the two fibrous reinforcements 34, 36 and the central core 2, there is placed on the upper reinforcement a plate 52 having a series of tips 54 facing downwards, completely through this reinforcement.
    After the sintering operation of the ceramic matrix of the skins, the plate 52 is removed, its tips 54 leaving equivalent perforations in the upper skin. It is also possible to place on the plate 52 tips 54 made of a material that disappears during the sintering operation.
    For these methods of producing perforations, the height of the tips 50, 54 can be adjusted to the thickness of the fibrous reinforcement 36 to be crossed.
    Alternatively the length of the tips 50, 54 may be larger with a passing of the other side of the fiber reinforcement 36, to ensure complete perforation of the upper skin. In this case for the first embodiment method, it is possible to level the ends of the tips 50 protruding before closing the mold, or to introduce these ends into housings provided in the mold cover. For the second manufacturing method the end of the tips 54 can penetrate into the fugitive filling material 30.
    It will be noted that these methods of producing the perforations spread the fibers during the introduction of the tips 50, 54 without cutting them, which does not degrade the mechanical strength of the skin thus perforated.
    Alternatively the perforations can be made by any other method, such as mechanical drilling, or laser beam drilling.
    权利要求:
    Claims (15)
    [1" id="c-fr-0001]
    1. A method of manufacturing an acoustic attenuation panel comprising two outer skins (4, 6) made of ceramic matrix composite material containing a fibrous reinforcement (34, 36), assembled on each side of a central honeycomb core (2). ) comprising walls (10) forming acoustic cavities (12) made by at least partial electrochemical conversion of aluminum to aluminum oxide, characterized in that it comprises a step of insertion into acoustic cavities (12) d a fugitive filling material (30) leaving free in each cavity, on each side against the skin, an annular space around this cavity, and a sintering step of the ceramic composite material providing elimination of the fugitive material, with a filling the composite material with spaces around the cavities.
    [2" id="c-fr-0002]
    2. The manufacturing method according to claim 1, characterized in that it comprises an additional step for performing, during the sintering step, perforations (8) of one of the skins of composite material (6).
    [3" id="c-fr-0003]
    3. Manufacturing method according to claim 2, characterized in that the additional step comprises the realization of spikes (50) on the fugitive filling material (30), in the same material, passing through a fibrous reinforcement (36) of a skin.
    [4" id="c-fr-0004]
    4. Manufacturing method according to claim 2, characterized in that the additional step comprises the removal on the outer side of a fibrous reinforcement (36) provided for a skin, a plate (52) equipped with spikes (54). ) crossing this reinforcement.
    [5" id="c-fr-0005]
    5. Manufacturing process according to any one of the preceding claims, characterized in that it uses to make the skins (4, 6) dry fibrous reinforcements then receiving the matrix by filtration, or fibrous reinforcements pre-impregnated with a matrix .
    [6" id="c-fr-0006]
    6. Manufacturing process according to any one of the preceding claims, characterized in that it uses for the fugitive filling material (30) one or more materials selected from thermoplastic and thermosetting plastics.
    [7" id="c-fr-0007]
    7. Manufacturing process according to any one of the preceding claims, characterized in that the embodiment of the acoustic cavities (12) comprises a step of assembling them together with aluminum strips by means of hardening, crimping , a solder, or a bonding with a preceramic adhesive.
    [8" id="c-fr-0008]
    8. Acoustic attenuation panel made of ceramic composite material, characterized in that it is made with a process according to any one of the preceding claims.
    [9" id="c-fr-0009]
    Acoustic attenuation panel according to claim 8, characterized in that the aluminum of the walls (10) of the acoustic cavities (12) is completely converted to aluminum oxide.
    [10" id="c-fr-0010]
    10. sound attenuation panel according to claim 8 or 9, characterized in that the connection of the ceramic composite material of the skins (4, 6) with the walls (10) of the central core (2) substantially forms a radius connection (R).
    [11" id="c-fr-0011]
    11. acoustic attenuation panel according to any one of claims 8 to 10, characterized in that the two skins (4, 6) comprise a fibrous reinforcement (34, 36) of metal oxide and a metal oxide matrix.
    [12" id="c-fr-0012]
    12. acoustic attenuation panel according to claim 11, characterized in that the matrix and the fibrous reinforcement (34, 36) of the skins (4, 6) comprise at least two different ceramic materials.
    [13" id="c-fr-0013]
    13. sound attenuation panel according to any one of claims 8 to 12, characterized in that the central core (2) has drainage passages (20) between cavities (12).
    [14" id="c-fr-0014]
    14. Sound attenuation panel according to any one of claims 8 to 13, characterized in that the central core (2) has on its sides slots (22) for hooking on the skins (6,8).
    [15" id="c-fr-0015]
    15. Aircraft propulsion unit comprising one or more acoustic attenuation panels according to any one of claims 8 to 13.
    类似技术:
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    同族专利:
    公开号 | 公开日
    US20180166058A1|2018-06-14|
    EP3325271A1|2018-05-30|
    WO2017017369A1|2017-02-02|
    EP3325271B1|2019-02-27|
    FR3039147B1|2017-08-25|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
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    法律状态:
    2016-06-30| PLFP| Fee payment|Year of fee payment: 2 |
    2017-01-27| PLSC| Search report ready|Effective date: 20170127 |
    2017-06-29| PLFP| Fee payment|Year of fee payment: 3 |
    2018-03-02| CD| Change of name or company name|Owner name: SAFRAN NACELLES, FR Effective date: 20180125 |
    2018-06-28| PLFP| Fee payment|Year of fee payment: 4 |
    2020-06-23| PLFP| Fee payment|Year of fee payment: 6 |
    2021-06-23| PLFP| Fee payment|Year of fee payment: 7 |
    优先权:
    申请号 | 申请日 | 专利标题
    FR1557083A|FR3039147B1|2015-07-24|2015-07-24|ACOUSTICAL ATTENUATION PANEL IN CERAMIC OXIDE COMPOSITE MATERIAL WITH ELECTROCHIMICALLY CONVERTED METALLIC MATERIAL|FR1557083A| FR3039147B1|2015-07-24|2015-07-24|ACOUSTICAL ATTENUATION PANEL IN CERAMIC OXIDE COMPOSITE MATERIAL WITH ELECTROCHIMICALLY CONVERTED METALLIC MATERIAL|
    EP16760523.7A| EP3325271B1|2015-07-24|2016-07-25|Acoustic attenuation panel in oxide cmc with a metallic core electrochemically converted into an oxide|
    PCT/FR2016/051936| WO2017017369A1|2015-07-24|2016-07-25|Acousitc attenuation panel made from ceramic oxide material with a core made from an electrochemically converted metal material|
    US15/878,431| US20180166058A1|2015-07-24|2018-01-24|Acoustic attenuation panel made of an oxide ceramic composite material with a core made of an electrochemically-converted metal material|
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