Production of an acoustic panel by bonding, with prior heat treatment
Patent Information
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- SAFRAN SA
- Filing Date
- 2024-07-22
- Publication Date
- 2026-06-10
Smart Images
Figure FR2024051013_06022025_PF_FP_ABST
Abstract
Description
Description Title of the invention: Manufacture of an acoustic panel by gluing with prior heat treatment Technical Field
[0001] The present invention relates to the general field of acoustic attenuation structures. It relates more particularly to acoustic attenuation structures used to reduce noise produced in aircraft engines such as in gas turbines or their exhausts. Prior art
[0002] Acoustic attenuation panels typically consist of an acoustic surface plate or skin permeable to the acoustic waves that are to be attenuated and a reflective solid plate or skin called a "closing plate", a multicellular body being arranged between these two skins. The multicellular body is generally constituted by a set of partitions, for example in the form of a honeycomb, delimiting a plurality of cells. In a well-known manner, such panels form Helmholtz-type resonators that make it possible to attenuate the acoustic waves in a certain frequency range, the height of the cavities making it possible to choose the targeted frequency band. Acoustic attenuation panels of this type are described in particular in documents US 5,912,442 and GB 2,314,526. Thus, the lower the frequency bands to be attenuated, the greater the height of the cavities will be.
[0003] These acoustic attenuation panels, limited to simple cell shapes such as those of the NIDA type honeycomb cells, are not suitable for very low frequencies to be absorbed due to the height of the required cavities and the resulting bulk. This is particularly the case for acoustic attenuation panels present in high bypass ratio turbojets for which the frequencies to be absorbed are between 200 Hz and 400 Hz and for which the possible bulk is limited.
[0004] One solution to handle low frequencies without resorting to an overly thick multicellular body is to place hollow acoustic elements, for example open cone truncates, in the cells of the multicellular body as described in document FR 3 082 987.
[0005] To manufacture such an acoustic panel, it is therefore necessary to assemble the acoustic skin with an acoustic component formed by the hollow acoustic elements, the hollow acoustic elements with the multicellular body and the multicellular body with the possible closing skin.
[0006] These various assemblies can be made by gluing. Indeed, unlike welding, gluing has the advantage of being able to be made with both thermoplastic and thermosetting materials or with combinations of thermoplastic and thermosetting materials.
[0007] However, gluing has many disadvantages. First, the positioning of the glue is difficult, especially on the edges of the acoustic elements or the multi-cellular body. In addition, the glue can flow inside the acoustic elements or cells of the multi-cellular body and partially block them, thus impairing the acoustic performance of the final acoustic panel. Statement of the invention
[0008] The present invention aims to remedy the aforementioned drawbacks by proposing an easy assembly solution for acoustic panels, without risking reducing the acoustic performance of said acoustic panel obtained.
[0009] To this end, the invention proposes a method for manufacturing an acoustic panel comprising the assembly of at least one first element with a second element, the first element comprising a plurality of cells opening onto a first assembly face of said first element so as to form a plurality of first openings on the first assembly face, said first openings being separated from each other by first opening edges, the method being characterized in that it comprises:
[0010] - applying at least one adhesive film comprising a plurality of orifices to the first assembly face of the first element, the centers of the orifices of the adhesive film coinciding with the center of the first openings of the first assembly face,
[0011] - a first heat treatment of the adhesive film applied to the first assembly face of the first element so that said adhesive film shrinks on the first opening edges and hardens, then
[0012] - bringing the second element into contact with the first assembly face of the first element, then
[0013] - a second heat treatment of the adhesive film applied to the first assembly face of the first element so as to fix the first assembly face of the first element to the second element.
[0014] Thus, the use of a film of glue and the carrying out of a first heat treatment of the glue before assembly makes it easier to position the glue and avoids the presence of glue inside the cones of the acoustic component or the cells of the multicellular body. The acoustic performance of the acoustic panel thus obtained is therefore not degraded by the assembly. In addition, the assembly method of the invention also has the advantage of being able to be carried out even with elements to be assembled made of non-thermoplastic material.
[0015] The second heat treatment is preferably carried out with the application of pressure so as to press the first element against the second element. Bonding of the first element to the second element is thus facilitated, and the resulting bond is of better quality.
[0016] According to a particular embodiment of the invention, the orifices of the adhesive film have the same geometric shape as the first openings of the first assembly face.
[0017] Thus, the shrinkage of the glue film during the first heat treatment is done in a homogeneous manner, allowing good positioning of the glue on the edges of the cones of the acoustic component or on the edges of the cells of the multicellular body.
[0018] According to another particular embodiment of the invention, the area of each orifice of the adhesive film associated with a first opening of the first assembly face is between 50% and 75% of the area of said first associated opening of the first assembly face.
[0019] This provides a satisfactory compromise, allowing for a satisfactory amount of glue on the edges of the cones of the acoustic component or on the edges of the cells of the multicellular body, while avoiding an unnecessary surplus of glue. This avoids the disadvantages associated with too much glue, for example glue drips or the appearance of bubbles that would affect acoustic performance.
[0020] According to another particular embodiment of the invention, the first heat treatment of the glue film is carried out in an infrared oven.
[0021] Using an infrared oven allows you to treat large surfaces. An infrared oven also has the advantage of being very responsive, allowing you to quickly reach the desired temperature.
[0022] According to another particular embodiment of the invention, the method further comprises a step of preparing the first assembly surface of the first element by plasma treatment before applying the adhesive film.
[0023] Such a preparation step makes it possible to improve the mechanical resistance of the bond by adhesive, and to break down the additive molecules which harm the bonding.
[0024] According to another particular embodiment of the invention, the method further comprises the assembly of a third element with the second element, the second element comprising a plurality of cells opening onto an assembly face of said second element so as to form a plurality of openings on the assembly face of the second element, said openings being separated from each other by opening edges, the method further comprising:
[0025] - applying at least one adhesive film comprising a plurality of orifices to the assembly face of the second element, the centers of the orifices of the adhesive film coinciding with the center of the openings of the assembly face of the second element,
[0026] - a first heat treatment of the adhesive film applied to the assembly face of the second element so that said adhesive film shrinks on the opening edges and hardens, then
[0027] - bringing the third element into contact with the assembly face of the second element, then
[0028] - a second heat treatment of the adhesive film applied to the assembly face of the second element so as to fix the assembly face of the second element to the third element, this second heat treatment being carried out at the same time as the second heat treatment making it possible to fix the assembly face of the first element to the second element.
[0029] The second heat treatment is preferably carried out with the application of pressure so as to press the third element against the second element. Bonding of the third element to the second element is thus facilitated, and the resulting bond is of better quality.
[0030] According to another particular embodiment of the invention, the method further comprises the assembly of a fourth element with the first element, the cells of the first element opening onto a second assembly face opposite the first assembly face of said first element so as to form a plurality of second openings on the second assembly face of the first element, said second openings being separated from each other by second opening edges, the method then comprising:
[0031] - applying at least one adhesive film comprising a plurality of orifices to the second assembly face of the first element, the centers of the orifices of the adhesive film coinciding with the center of the second openings of the second assembly face of the first element,
[0032] - a first heat treatment of the adhesive film applied to the second assembly face of the first element so that said adhesive film shrinks on the opening edges and hardens, then
[0033] - bringing the fourth element into contact with the second assembly face of the first element, then
[0034] - a second heat treatment of the adhesive film applied to the second assembly face of the first element so as to fix the second assembly face of the first element to the fourth element, this second heat treatment being carried out at the same time as the second heat treatment making it possible to fix the first assembly face of the first element to the second element.
[0035] The second heat treatment is preferably carried out with the application of pressure so as to press the first element against the fourth element. Bonding of the second element to the fourth element is thus facilitated, and the resulting bond is of better quality.
[0036] According to another particular embodiment of the invention, the first element is an acoustic component whose cells are a plurality of hollow acoustic elements having a shape gradually narrowing between a base and a top, the bases of said hollow acoustic elements being connected to each other by connecting edges corresponding to the edges of openings of the assembly face of said first element, and the second element is an acoustic skin.
[0037] According to another particular embodiment of the invention, the first element is a multicellular body, and the second element is an acoustic component comprising a plurality of hollow acoustic elements having a shape gradually narrowing between a base and a top, the bases of said hollow acoustic elements being connected to each other by connecting edges, the attachment of the first element to the second element being carried out so that the tops of the hollow acoustic elements of the second element are arranged in the cells of the first element.
[0038] According to another particular embodiment of the invention, the first element is a multicellular body, the second element is an acoustic component whose cells are a plurality of hollow acoustic elements having a shape gradually narrowing between a base and a top, the bases of said hollow acoustic elements being connected to each other by connecting edges corresponding to the edges of openings of the assembly face of said second element, the attachment of the first element to the second element being carried out so that the tops of the hollow acoustic elements of the second element are arranged in the cells of the first element, and the third element is an acoustic skin.
[0039] According to another particular embodiment of the invention, the first element is a multicellular body, the second element is an acoustic component whose cells are a plurality of hollow acoustic elements having a shape gradually narrowing between a base and a top, the bases of said hollow acoustic elements being connected to each other by connecting edges corresponding to the edges of openings of the assembly face of said second element, the attachment of the first element to the second element being carried out so that the tops of the hollow acoustic elements of the second element are arranged in the cells of the first element, the third element is an acoustic skin and the fourth element is a closing skin. Brief description of the drawings
[0040] [Fig. 1] Figure 1 is a schematic exploded perspective view of an acoustic panel obtained by the method of the invention.
[0041] [Fig. 2] Figure 2 is a schematic sectional view of the acoustic panel of Figure 1.
[0042] [Fig. 3] Figure 3 is a flowchart of the method of the invention for assembling two elements.
[0043] [Fig. 4] Figure 4 is a flowchart of the method of the invention for assembling three elements.
[0044] [Fig. 5] Figure 5 is a flowchart of the method of the invention for assembling three elements.
[0045] [Fig. 6] Figure 6 is a schematic top view of the first element to which a film of glue is applied.
[0046] [Fig. 7] Figure 7 is a schematic sectional view of the first element of Figure 6.
[0047] [Fig. 8] Figure 8 is a schematic top view of the first element of Figures 6 and 7 after a first heat treatment of the glue film.
[0048] [Fig. 9] Figure 9 is a schematic top view of the second element to which a film of glue is applied.
[0049] [Fig. 10] Figure 10 is a schematic sectional view of the second element of Figure 9.
[0050] [Fig. 11] Figure 11 is a schematic top view of the second element of Figures 9 and 10 after a first heat treatment of the glue film.
[0051] [Fig. 12] Figure 12 is a schematic sectional view of the first element of Figure 8, the second element of Figure 11 and the third element brought into contact. Description of the embodiments
[0052] Figures 1 and 2 illustrate an example of an acoustic panel 100 comprising in order an acoustic skin 110, an acoustic component 120 comprising a plurality of hollow acoustic elements 121, a multicellular body 130 and a closing skin 140.
[0053] The acoustic skin 110 has the function of allowing the sound waves to be attenuated to pass through inside the acoustic panel 100. For this purpose, the acoustic skin 110 comprises a plurality of perforations 111, as illustrated in FIGS. 1 and 2. Preferably, each cell of the multicellular body 130 associated with a hollow acoustic element 121 of the acoustic component 120 corresponds to a plurality of perforations 111 of the acoustic skin 110. The perforations 111 may have a diameter of between 2 mm and 5 mm. The acoustic skin 110 may have a thickness of between 1 mm and 5 mm, for example 2 mm.
[0054] The acoustic skin 110 can be produced in a well-known manner by stamping, by automatic fiber placement known as “AFP” for “Automated Fiber Placement”, or by automatic tape laying known as “ATL” for “Automated Tape Lying”. Other methods can also be used to manufacture the acoustic skin 110, such as manual draping.
[0055] The opening acoustic skin 110 may be made of a thermoplastic material, for example a composite material with a thermoplastic matrix comprising fibers. The fibers may be carbon, glass or aramid. The opening acoustic skin 110 may not comprise fibers. The thermoplastic matrix may be made, for example, of polyaryletherketone (PAEK), polyetherketoneketone (PEKK), polyetherimide (PEI), polyphenylene sulfide (PPS), polyethersulfone (PESU) or polycarbonate (PC). The opening acoustic skin 110 may also be made of a thermosetting material, for example a composite material comprising fibers and a matrix of thermosetting material.
[0056] The closing skin 140 corresponds to a solid surface intended to reflect the sound waves entering the acoustic panel 100. The closing skin 140 may be a constituent element of the acoustic panel, as in the example described here, or correspond to a structure of an object, for example an aircraft engine. In the latter case, the acoustic panel does not have a closing skin and is directly mounted on the structure of the object. The closing skin 140 may have a thickness of between 1 mm and 5 mm, for example 2 mm.
[0057] The closure skin 140 can be produced in a well-known manner by stamping, by automatic fiber placement known as “AFP” for “Automated Fiber Placement”, or by automatic tape draping known as “ATL” for “Automated Tape Lying”. Other methods can also be used to manufacture the closure skin 140. For example, the closure skin can be pre-baked and then assembled by gluing on the multicellular body. In the case where the closure skin 140 is made of thermosetting material, it can be formed and baked directly on the multicellular body.
[0058] The closure skin 140 may be made of a thermoplastic material or a thermosetting material. The closure skin 140 may be made of a composite material comprising fibers, for example a composite material based on carbon fibers impregnated with a thermoplastic or thermosetting resin. The closure skin 140 may not comprise fibers. The acoustic opening skin 110 may be made of a thermoplastic material, for example a thermoplastic matrix composite material comprising fibers. The fibers may be carbon, glass, or aramid. The thermoplastic matrix may be made, for example, of polyaryletherketone (PAEK), polyetherketoneketone (PEKK), polyetherimide (PEI), polyphenylene sulfide (PPS), polyethersulfone (PESU), or polycarbonate (PC).
[0059] The multicellular body 130 comprises a plurality of partitions 131 which form a network of ribs, thus delimiting cells 132. The partitions 131 each extend between an upper edge 131a and a lower edge 131b. The upper edges 131a of the partitions 131 define a first assembly face 130a of the multicellular body 130. The lower edges 131b of the partitions 131 define a second assembly face 130b of the multicellular body 130. Thus, the cells 132 extend from the first assembly face 130a to the second assembly face 130b of the multicellular body 130.
[0060] HI Heights 30 cells 132 of the multicellular body 130 are chosen so as to obtain processing of the frequencies of interest according to the use which will be made of the acoustic panel 100.
[0061] In the example illustrated in Figures 1 and 2, the cells 132 of the multicellular body 130 have a hexagonal section. It is of course within the scope of the invention if the cells 132 of the multicellular body 130 have a square, rectangular, round or other section.
[0062] The multicellular body 130 may be made of polymer, composite or metallic material, by additive manufacturing or by conventional means. The multicellular body 130 may also be made in a well-known manner of thermoplastic material by injection, bending or tube assembly. The thermoplastic material may be filled with short fibers or with long fibers. The multicellular body 130 may not be filled.
[0063] The acoustic component 120 comprises a plurality of hollow acoustic elements 121 each having a shape gradually tapering between a base 121a and a top 121b. The hollow acoustic elements 121 are connected to each other by one or more connecting edges 122. The connecting edges 122 comprise an upper face 122a, located on the same plane as the bases 121a of the hollow acoustic elements 121, and a lower face 122b opposite the upper face 122a. The bases 121a of the hollow acoustic elements 121 and the upper faces 122a of the edges 122 define a first assembly face 120a of the acoustic component 120. The first assembly face 120a of the acoustic component 120 is intended to be assembled in contact with the acoustic skin 110. The lower faces 122b of the edges 122 define a second assembly face 120b of the acoustic component 120. The second assembly face 120b of the acoustic component 120 is intended to be assembled in contact with the multicellular body 130.More precisely, the second assembly face 120b of the acoustic component 120 is intended to be assembled in contact with the first assembly face 130a of the multicellular body 130.
[0064] In the example shown in Figures 1 and 2, the hollow acoustic elements 121 have a pyramidal shape. However, it does not depart from the scope of the invention if the hollow acoustic elements have, for example, a conical, spiral or funnel shape. In the example shown in Figures 1 and 2, the hollow acoustic elements 121 have symmetry. However, it does not depart from the scope of the invention if the hollow acoustic elements are asymmetrical.
[0065] In the example illustrated in Figures 1 and 2, the bases 121a of the hollow acoustic elements 121 have a hexagonal geometry. It is of course not beyond the scope of the invention if the bases of the hollow acoustic elements have another geometry, for example a circular, square or rectangular geometry. In the example illustrated in Figures 1 and 2, the vertices 121b of the hollow acoustic elements 121 have a hexagonal geometry. It is of course not beyond the scope of the invention if the vertices of the hollow acoustic elements have another geometry, for example a circular, square or rectangular geometry.
[0066] The hollow acoustic elements 121 may have a wall thickness of between 0.25 mm and 2 mm. Preferably, the hollow acoustic elements 121 have a thickness of less than 1 mm, for example less than or equal to 0.5 mm, for example between 0.3 mm and 0.5 mm. Such a reduced thickness makes it possible in particular to confer significant flexibility to the acoustic component 120, which makes it easier to shape it and assemble it against the acoustic skin 110. Such a thickness also makes it possible to reduce the mass of the acoustic component 120, and thus the overall mass of the acoustic panel 100.
[0067] Preferably, the base 121a of the hollow acoustic elements 121 is included in a circle whose diameter is between 8 mm and 25 mm. For example, the base 121a of the hollow acoustic elements 121 is included in a circle with a diameter of 20 mm. Preferably, the top 121b of the hollow acoustic elements 121 is included in a circle whose diameter is between 1 mm and 10 mm. For example, the top 121b of the hollow acoustic elements 121 is included in a circle with a diameter of 5 mm.
[0068] Preferably, the height H 120 of the hollow acoustic elements 121 is between 5 mm and 100 mm, and preferably between 5 mm and 50 mm. For example, the height H120 of the hollow acoustic elements 121 is 20 mm. The height H120 of the hollow acoustic elements 121 is less than the height Hi 30 132 cells of the multicellular body 130.
[0069] The acoustic component 120 can be produced in a well-known manner by additive manufacturing, injection or stamping.
[0070] The acoustic component 120 can also be produced in a well-known manner by injection-compression of a thermoplastic material. Injection-compression consists of injecting the material into a half-open mold. Thus, even if the material sets quickly upon contact with the mold due to the significant thermal difference between the tooling and the molten material, the cavity of the tooling becomes less obstructed and the pressure necessary for injecting the material remains acceptable. When the volume of material is entirely injected into the cavity and generally distributed over the entire mold, the latter is completely closed by a closing force to migrate the material into the most complex areas and return to the correct dimension. This makes it possible to obtain thinner wall thicknesses for the acoustic components than with a conventional injection process.
[0071] The acoustic component 120 can also be produced in a well-known manner by injection molding with tool temperature control of a thermoplastic material. Injection molding with tool temperature control consists of controlling the temperature of the tool or mold by means of a tool temperature control system, for example with a heat transfer fluid or with air.
[0072] The acoustic component 120 is preferably made of a thermoplastic material to facilitate its manufacture. The acoustic component 120 is preferably made of an amorphous thermoplastic material to facilitate its shaping. The acoustic component 120 may, for example, be made of polyetherimide (PEI) or polyethersulfone (PESU) to facilitate its manufacture and shaping after manufacture.
[0073] In the example illustrated in Figures 1 and 2, the acoustic panel 100 comprises only a single multicellular body 130 and a single acoustic component 120. It is of course not beyond the scope of the invention if the acoustic panel comprises several superimposed multicellular bodies. It is also not beyond the scope of the invention if the acoustic panel comprises several acoustic components. The acoustic panel may also comprise intermediate acoustic skins delimiting different levels of said acoustic panel.
[0074] As illustrated in Figures 3 to 5, the method according to the invention comprises the assembly of at least one first element with a second element, the first element comprising a plurality of cells opening onto a first assembly face of said first element so as to form a plurality of first openings on the first assembly face, said first openings being separated from each other by first opening edges, the method comprising:
[0075] - a first step E1 of applying at least one adhesive film comprising a plurality of orifices on the first assembly face of the first element, the centers of the orifices of the adhesive film coinciding with the center of the first openings of the first assembly face,
[0076] - a second step E2 of first heat treatment of the adhesive film applied to the first assembly face of the first element so that said adhesive film shrinks on the first opening edges and hardens, then
[0077] - a third step E3 of bringing the second element into contact with the first assembly face of the first element, then
[0078] - a fourth step E4 of second heat treatment of the adhesive film applied to the first assembly face of the first element so as to fix the first assembly face of the first element to the second element.
[0079] Optionally, a fifth surface preparation step E5 can be carried out before the first step El.
[0080] According to a first configuration, the first element may be the acoustic component 120 and the second element the acoustic skin 110. In this first configuration, the cells of the first element correspond to the hollow acoustic elements 121 of the acoustic component 120, the first assembly face of the first element corresponds to the first assembly face 120a of the acoustic component 120, and the first opening edges of the first element correspond to the upper faces 122a of the connecting edges 122 of the acoustic component 120.
[0081] According to a second configuration, the first element may be the multicellular body 130 and the second element the acoustic component 120. In this second configuration, the cells of the first element correspond to the cells 132 of the multicellular body 130, the first assembly face of the first element corresponds to the first assembly face 130a of the multicellular body 130, and the first opening edges of the first element correspond to the upper edges 131a of the partitions 131 of the acoustic component 130.
[0082] According to a third configuration, the first element can be the multicellular body 130 and the second element the closing skin 140. In this second configuration, the cells of the first element correspond to the cells 132 of the multicellular body 130, the first assembly face of the first element corresponds to the second assembly face 130b of the multicellular body 130, and the first edges of openings of the first element correspond to the lower edges 131b of the partitions 131 of the acoustic component 130.
[0083] As illustrated in Figures 4 and 5, the method according to the invention may comprise the assembly of three or four elements.
[0084] According to a first embodiment, the method of the invention may comprise the assembly of a third element with the second element, the second element comprising a plurality of cells opening onto an assembly face of said second element so as to form a plurality of openings on the assembly face of the second element, said openings being separated from each other by edges of openings, the method then comprising:
[0085] - a sixth step E6 of applying at least one adhesive film comprising a plurality of orifices on the assembly face of the second element, the centers of the orifices of the adhesive film coinciding with the center of the openings of the assembly face of the second element,
[0086] - a seventh step E7 of first heat treatment of the adhesive film applied to the assembly face of the second element so that said adhesive film shrinks on the opening edges and hardens, then
[0087] - an eighth step E8 of bringing the third element into contact with the assembly face of the second element, then
[0088] - a ninth step E9 of second heat treatment of the adhesive film applied to the assembly face of the second element so as to fix the assembly face of the second element to the third element, the ninth step E9 and the fourth step E4 being carried out simultaneously.
[0089] Optionally, a tenth surface preparation step E10 can be carried out before the sixth step E6.
[0090] The first, second and third stages E1, E2 and E3 can of course be carried out in parallel with the sixth, seventh and eighth stages E6, E7 and E8.
[0091] In the second configuration described above, the first element is the multicellular body 130 and the second element is the acoustic component 120. Thus, in this second configuration, a third element can also be assembled, which is the acoustic skin 110.
[0092] According to a second embodiment, the method of the invention may comprise the assembly of a fourth element with the first element, the cells of the first element opening onto a second assembly face opposite the first assembly face of said first element so as to form a plurality of second openings on the second assembly face of the first element, said second openings being separated from each other by second opening edges, the method then comprising:
[0093] - an eleventh step Eli of applying at least one adhesive film comprising a plurality of orifices on the second assembly face of the first element, the centers of the orifices of the adhesive film coinciding with the center of the second openings of the second assembly face of the first element,
[0094] - a twelfth step E12 of first heat treatment of the adhesive film applied to the second assembly face of the first element so that said adhesive film shrinks on the opening edges and hardens, then
[0095] - a thirteenth step E13 of bringing the fourth element into contact with the second assembly face of the first element, then
[0096] - a fourteenth step E14 of second heat treatment of the adhesive film applied to the second assembly face of the first element so as to fix the second assembly face of the first element to the fourth element, the fourteenth step E14 and the fourth step E4 being carried out simultaneously.
[0097] Optionally, a fifteenth surface preparation step E15 can be carried out before the eleventh step Eli.
[0098] The first, second and third stages E1, E2 and E3 can of course be carried out in parallel with the eleventh, twelfth and thirteenth stages E1, E12 and E13.
[0099] The first, sixth and eleventh stages E1, E6 and E11 will be similar and may have the same characteristics and parameters. The second, seventh and twelfth stages E2, E7 and E12 will be similar and may have the same characteristics and parameters. The fifth, tenth and fifteenth optional steps E5, E10 and E15 will be similar and may have the same characteristics and parameters.
[0100] In the second configuration described above, the first element is the multicellular body 130 and the second element is the acoustic component 120. Thus, in this second configuration, a fourth element can also be assembled, which is the closing skin 140. In this second configuration, the second assembly face of the first element corresponds to the second assembly face 130b of the multicellular body 130, and the second opening edges of the first element correspond to the lower edges 131b of the partitions 131 of the acoustic component 130.
[0101] In the third configuration described above, the first element is the multicellular body 130 and the second element is the closing skin 140. Thus, in this third configuration, a fourth element can also be assembled, which is the acoustic component 120. In this second configuration, the second assembly face of the first element corresponds to the first assembly face 130a of the multicellular body 130, and the second opening edges of the first element correspond to the upper edges 131a of the partitions 131 of the acoustic component 130.
[0102] The assembly of three elements can be carried out by carrying out the first embodiment without carrying out the second embodiment, as illustrated in Figure 4, or by carrying out the second embodiment without carrying out the first embodiment (variant not illustrated). Thus, the eleventh, twelfth and thirteenth steps E11, E12 and E13 can be carried out without carrying out the sixth, seventh and eighth steps E6, E7 and E8.
[0103] The assembly of four elements can be achieved by performing both the first mode and the second mode, as illustrated in Figure 5.
[0104] In the second configuration described above, the first element is the multicellular body 130 and the second element is the acoustic component 120. Thus, in this second configuration, it is possible to assemble both a third element which is the opening skin 110 and a fourth element which is the closing skin 140.
[0105] In conclusion, the particular adhesive assembly of the invention can be used only to assemble the acoustic component 120 to the acoustic skin 110, only to assemble the multicellular body 130 to the acoustic component 120 or only to assemble the closing skin 140 to the multicellular body 130. The particular adhesive assembly of the invention can also be used only to assemble the acoustic component 120 simultaneously to the acoustic skin 110 and to the multicellular body 130. The particular adhesive assembly of the invention can be used only to assemble the multicellular body 130 simultaneously to the acoustic component 120 and to the closing skin 140. The particular adhesive assembly of the invention can be used to simultaneously assemble the acoustic skin 110, the acoustic component 120, the multicellular body 130 and the closing skin 140.Other combinations can of course be made, for example with one or more intermediate acoustic skins, with a plurality of multicellular bodies or with a plurality of acoustic components.
[0106] We will describe an example of a method according to the invention in which the acoustic component 120 is assembled simultaneously with the acoustic skin 110 and the multicellular body 130. We are thus in the second configuration where the first element is the multicellular body 130, the second element is the acoustic component 120 and the third element is the acoustic skin 110. Thus, the cells of the first element correspond to the cells 132 of the multicellular body 130, the first assembly face of the first element corresponds to the first assembly face 130a of the multicellular body 130, and the first opening edges of the first element correspond to the upper edges 131a of the partitions 131 of the acoustic component 130.The cells of the second element correspond to the hollow acoustic elements 121 of the acoustic component 120, the assembly face of the second element corresponds to the first assembly face 120a of the acoustic component 120, and the opening edges of the. second element correspond to the upper faces 122a of the connecting edges 122 of the acoustic component 120.
[0107] The process can begin with degreasing the surfaces with ethanol.
[0108] The fifth optional step E5 is a plasma treatment carried out at least on the first assembly face 130a of the first element 130. This step aims to improve the mechanical strength of the bond and to break down the additive molecules present in the material of the first element 130 which impair bonding. This step is particularly advantageous when the first element 130 is made of thermoplastic material by molding, because the additives added to the thermoplastic material to facilitate demolding often impair bonding.
[0109] The fifth optional step E5 may also comprise the plasma treatment of the second assembly face 120b of the second element 120, with which the first assembly face 130a of the first element 130 will be assembled. This plasma treatment is particularly advantageous when the second element 120 is made of thermoplastic material by molding, because the additives added to the thermoplastic material to facilitate demolding often impair bonding.
[0110] Plasma treatment can be performed using atmospheric plasma. A plasma nozzle or head can be used. [YES] If the plasma-treated element is the first assembly surface 130a of the multicellular body 130, the second assembly surface 130b of the multicellular body 130 or the first assembly surface 120a of the acoustic component 120, a rotary nozzle, for example a Plasmatreat® 22826 nozzle, will be preferred. The plasma treatment can be carried out by moving back and forth on the assembly surface 130a, 130b or 120a, preferably with overlaps between the different trajectories, for example overlaps of approximately 1 mm. The plasma treatment can be carried out with a distance from the source of between 10 mm and 50 mm. The plasma treatment can be carried out with a distance from the source of approximately 20 mm for an acoustic component 120 made of polyetherimide (PEI). The feed rate of the nozzle can be between between 25 mm.s' 1 and 100 mm.s' 1Plasma treatment can be carried out with a feed rate of approximately 50 mm.sl for a 120 acoustic component made of polyetherimide (PEI).
[0112] If the plasma-treated element is the second assembly surface of the acoustic component 120, a static nozzle will be preferred, for example a Plasmatreat® 16609 nozzle. The nozzle may have an opening of approximately 1.5 mm. The nozzle may allow treatment along a strip whose width is between 3 mm and 4 mm. The plasma treatment may be carried out with trajectories along two main guidelines on the first assembly surface 130a or 120a, following rectilinear trajectories or following trajectories along the lower faces 122b of the connecting edges 122 of the acoustic component 120. The plasma treatment may be carried out with a distance from the source of between 10 mm and 50 mm. The plasma treatment may be carried out with a distance from the source of approximately 20 mm for an acoustic component 120 made of polyetherimide (PEI). The feed rate of the nozzle may be between 25 mm.s 1 and 100 mm.s 1Plasma treatment can be carried out with a feed rate of approximately 25 mm.sl for a 120 acoustic component made of polyetherimide (PEI).
[0113] As illustrated in Figures 6 and 7, the first step E1 is carried out by applying at least one adhesive film 520 comprising a plurality of orifices 521 to the first assembly face 130a of the first element 130, the centers of the orifices 521 of the adhesive film 520 coinciding with the center of the first openings 132 of the first assembly face 130a. Thus, the first edges of openings 131a of the first element 130 are completely covered by the adhesive film(s) 520. Preferably, the adhesive film(s) 520 comprise the orifices 521 before being applied to the first element 130.
[0114] The adhesive film can have a weight of 300 gm' 2 The adhesive film can be an epoxy adhesive film, for example Redux® 322 adhesive.
[0115] In the example illustrated in Figures 6 and 7, the orifices 521 of the adhesive film 520 have the same geometric shape as the first openings 132 of the first assembly face 130a. Thus, the orifices 521 of the adhesive film 520 and the first openings 132 of the first assembly face 130a have a hexagonal shape. The use of the same geometric shape allows for more uniform retraction of the adhesive film 520 on the first opening edges 131a.
[0116] It is of course not departing from the scope of the invention if the orifices 521 of the adhesive film 520 and the first openings 132 of the first assembly face 130a have different geometric shapes. For example, the first openings 132 of the first assembly face 130a may have a hexagonal shape and the orifices 521 of the adhesive film 520 may have a circular shape.
[0117] Preferably, the area of each orifice 521 of the adhesive film 520 associated with a first opening 132 of the first assembly face 130a is between 25% and 80% of the area of said associated first opening 132.
[0118] The second step E2 is then carried out, in which a first heat treatment of the glue film 520 is carried out so that the glue film 520 shrinks on the first opening edges 131a and hardens. This produces crosslinking of the glue. As illustrated in FIG. 8, a crosslinked glue film 620 is thus obtained comprising a plurality of orifices 621 having a larger area than the area of the orifices 521 of the glue film 520 before the first heat treatment.
[0119] The first heat treatment can be carried out in an infrared oven. The first heat treatment can also be carried out in an oven, or by any other suitable means.
[0120] The first heat treatment is carried out with a temperature, pressure and duration adapted to the first element 130 and to the chosen adhesive film 520, in order to obtain satisfactory crosslinking. The choice of these parameters does not present any difficulties for those skilled in the art. For example, the first heat treatment can be carried out in an infrared oven for a duration of between 2 minutes and 5 minutes at a temperature of 180°C.
[0121] Before proceeding to the third step, the sixth, seventh and eighth steps E6 and E7, and possibly the tenth step E10, are preferably carried out.
[0122] The tenth optional step E10 is a plasma treatment carried out at least on the first assembly face 120a of the second element 120. This step aims to improve the mechanical strength of the connection and to break the functions of any additives present in the material of the second element 120 which impair bonding. This step is particularly advantageous when the second element 120 is made of thermoplastic material by molding, because the additives added to the thermoplastic material to facilitate demolding often impair bonding.
[0123] The optional tenth step E10 may also comprise the plasma treatment of the third element 110, with which the first assembly face 120a of the second element 120 will be assembled.
[0124] Plasma treatment can be performed using atmospheric plasma. A plasma nozzle or head can be used.
[0125] If the plasma-treated element is the first assembly surface 130a of the multicellular body 130, the second assembly surface 130b of the multicellular body 130 or the first assembly surface 120a of the acoustic component 120, a rotary nozzle, for example a Plasmatreat® 22826 nozzle, will be preferred. The plasma treatment can be carried out by moving back and forth on the assembly surface 130a, 130b or 120a, preferably with overlaps between the different trajectories, for example overlaps of approximately 1 mm. The plasma treatment can be carried out with a distance from the source of between 10 mm and 50 mm. The plasma treatment can be carried out with a distance from the source of approximately 20 mm for an acoustic component 120 made of polyetherimide (PEI). The feed rate of the nozzle can be between 25 mm.s -1 and 100 mm.s' 1Plasma treatment can be carried out with a feed rate of approximately 50 mm.sl for a 120 acoustic component made of polyetherimide (PEI).
[0126] If the plasma-treated element is the second assembly surface of the acoustic component 120, a static nozzle will be preferred, for example a Plasmatreat® 16609 nozzle. The nozzle may have an opening of approximately 1.5 mm. The nozzle may allow treatment along a strip whose width is between 3 mm and 4 mm. The plasma treatment may be carried out with trajectories along two main guidelines on the first assembly surface 130a or 120a, following rectilinear trajectories or following trajectories along the lower faces 122b of the connecting edges 122 of the acoustic component 120. The plasma treatment may be carried out with a distance from the source of between 10 mm and 50 mm. The plasma treatment may be carried out with a distance from the source of approximately 20 mm for an acoustic component 120 made of polyetherimide (PEI). The feed rate of the nozzle may be between 25 mm.s -1 and 100 mm.s' 1Plasma treatment can be carried out with a feed rate of approximately 25 mm.sl for a 120 acoustic component made of polyetherimide (PEI).
[0127] As illustrated in Figures 9 and 10, the sixth step E6 is carried out by applying at least one adhesive film 510 comprising a plurality of orifices 511 to the assembly face 120a of the second element 120, the centers of the orifices 511 of the adhesive film 510 coinciding with the center of the openings of the assembly face 120a of the second element 120. Thus, the edges of openings 122a of the second element 120 are completely covered by the adhesive film(s) 510. Preferably, the adhesive film(s) 510 comprise the orifices 511 before being applied to the second element 120.
[0128] The adhesive film can have a weight of 300 gm' 2 The adhesive film can be an epoxy adhesive film, for example Redux® 322 adhesive.
[0129] In the example illustrated in Figures 9 and 10, the orifices 511 of the adhesive film 510 have the same geometric shape as the openings of the assembly face 120a of the second element 120. Thus, the orifices 511 of the adhesive film 510 and the openings of the assembly face 120a have a hexagonal shape. The use of the same geometric shape allows a more homogeneous retraction of the adhesive film 510 on the opening edges 122a.
[0130] It is of course not departing from the scope of the invention if the orifices 511 of the adhesive film 510 and the openings of the assembly face 120a have different geometric shapes. For example, the openings of the assembly face 120a may have a hexagonal shape and the orifices 511 of the adhesive film 510 may have a circular shape.
[0131] Preferably, the area of each orifice 511 of the adhesive film 510 associated with an opening of the assembly face 120a is between 25% and 80% of the area of said associated opening.
[0132] The seventh step E7 is then carried out, in which a first heat treatment of the glue film 510 is carried out so that the glue film 510 shrinks on the edges of openings 122a and hardens. This produces crosslinking of the glue. As illustrated in FIG. 11, a crosslinked glue film 610 is thus obtained comprising a plurality of orifices 611 having a larger area than the area of the orifices 511 of the glue film 510 before the first heat treatment.
[0133] The first heat treatment can be carried out in an infrared oven. The first heat treatment can also be carried out in an oven, or by any other suitable means.
[0134] The first heat treatment is carried out with a temperature, a pressure and a duration adapted to the second element 120 and to the chosen adhesive film 510, in order to obtain satisfactory crosslinking. The choice of these parameters does not present any difficulties for those skilled in the art. For example, the first heat treatment can be carried out in an infrared oven for a duration of between 2 minutes and 5 minutes at a temperature of 180°C. These parameters are particularly suitable for the treatment of an adhesive film 510 applied to an acoustic component 120 made of polyetherimide (PEI) or polyethersulfone (PESU).
[0135] The second step E2 and the seventh step E7 can be carried out simultaneously. For example, the second step E2 and the seventh step E7 can be carried out in the same oven.
[0136] The third step E3 and the eighth step E8 are then carried out. This brings the first assembly face 130a of the first element 130 into contact with the second element 120 and the assembly face 120a of the second element 120 into contact with the third element 110, as illustrated in FIG. 12. Thus, the first assembly face 130a of the multicellular body 130 on which the crosslinked adhesive film 620 is applied is brought into contact with the second assembly face 120b of the acoustic component. The first assembly face 120a of the acoustic component 120 on which the crosslinked adhesive film 610 is applied is brought into contact with the acoustic skin 110.
[0137] The fourth step E4 and the ninth step E9 are then carried out. A second heat treatment of the crosslinked adhesive films 610 and 620 is thus carried out, so as to fix the first element 130 to the second element 120 and the second element 120 to the third element 110.
[0138] The second heat treatment can be carried out in an autoclave. The second heat treatment can also be carried out in an infrared oven, or by any other suitable means.
[0139] The second heat treatment is carried out with a temperature, pressure and duration adapted to the first element 130, to the second element 120 and to the third element 110, as well as to the crosslinked adhesive films 610 and 620 chosen, in order to obtain satisfactory bonding. The choice of these parameters does not present any difficulties for those skilled in the art. For example, the second heat treatment can be carried out in an autoclave for a duration of between 1 hour and 6 hours at a temperature of 180°C and at a pressure of between 1 bar and 5 bars. A vacuum tank can be used.For example, the second heat treatment may include ramping the temperature at 1°C per minute until 105°C is reached, then maintaining the temperature at approximately 105°C for 1 hour and 30 minutes, then ramping the temperature at 2°C per minute until 180°C is reached, then maintaining the temperature at approximately 180°C for two hours, before cooling and removing the bonded assembly.
[0140] This produces an assembly of two, three, four or more elements made by gluing. The assembly is then completed to obtain the desired 100 acoustic panel.
[0141] The acoustic panel 100 is thus obtained. The acoustic panel 100 can, for example, be used for acoustic attenuation in a nacelle or an aircraft engine, for a blade platform, for an aeronautical sleeve. The acoustic panel 100 can, for example, be used to cover the internal fixed part (IFS) of a nacelle, the cowl of an aircraft fan, a sliding aeronautical sleeve, an aircraft air intake or an aircraft wing part. The acoustic panel 100 is particularly suitable for the treatment of low frequencies.
[0142] The expression "between ... and ..." must be understood as including the limits.
Claims
Claims
1. A method of manufacturing an acoustic panel (100) comprising assembling at least one first element (130) with a second element (120), the first element (130) comprising a plurality of cells (132) opening onto a first assembly face (130a) of said first element (130) so as to form a plurality of first openings on the first assembly face (130a), said first openings being separated from each other by first opening edges (131a), the method being characterized in that it comprises: - (El) applying at least one adhesive film (520) comprising a plurality of orifices (521) to the first assembly face (130a) of the first element (130), the centers of the orifices (521) of the adhesive film (520) coinciding with the center of the first openings of the first assembly face (130a), - (E2) a first heat treatment of the adhesive film (520) applied to the first assembly face (130a) of the first element (130) so that said adhesive film (520) shrinks on the first opening edges (131a) and hardens, then - (E3) bringing the second element (120) into contact with the first assembly face (130a) of the first element (130), then - (E4) a second heat treatment of the adhesive film (620) applied to the first assembly face (130a) of the first element (130) so as to fix the first assembly face (130a) of the first element (130) to the second element (120).
2. Manufacturing method according to claim 1, wherein the orifices (521) of the glue film (520) have the same geometric shape as the first openings of the first assembly face (130a).
3. Manufacturing method according to claim 1 or 2, wherein the area of each orifice (521) of the glue film (520) associated with a first opening of the first assembly face (130a) is between 50% and 75% of the area of said associated first opening of the first assembly face (130a).
4. A manufacturing method according to any one of claims 1 to 3, wherein the first heat treatment of the glue film (520) is carried out in an infrared oven.
5. Manufacturing method according to any one of claims 1 to 4, further comprising a step (E5) of preparing the first assembly surface (130a) of the first element (130) by plasma treatment before applying the adhesive film (520).
6. A manufacturing method according to any one of claims 1 to 5, further comprising assembling a third element (110) with the second element (120), the second element (120) comprising a plurality of cells (121) opening onto an assembly face (120a) of said second element (120) so as to form a plurality of openings on the assembly face (120a) of the second element (120), said openings being separated from each other by opening edges (122a), the method further comprising: - (E6) applying at least one adhesive film (510) comprising a plurality of orifices (511) to the assembly face (120a) of the second element (120), the centers of the orifices (511) of the adhesive film (510) coinciding with the center of the openings of the assembly face (120a) of the second element (120), - (E7) a first heat treatment of the adhesive film (510) applied to the assembly face (120a) of the second element (120) so that said adhesive film (510) shrinks on the opening edges (122a) and hardens, then - (E8) bringing the third element (110) into contact with the assembly face (120a) of the second element (120), then - (E9) a second heat treatment of the adhesive film (610) applied to the assembly face (120a) of the second element (120) so as to fix the assembly face (120a) of the second element (120) to the third element (110), this second heat treatment being carried out at the same time as the second heat treatment making it possible to fix the assembly face (130a) of the first element (130) to the second element (120).
7. A manufacturing method according to any one of claims 1 to 6, further comprising assembling a fourth element (140) with the first element (130), the cells (132) of the first element (130) opening onto a second assembly face (130b) opposite the first assembly face (130a) of said first element (130) so as to form a plurality of second openings on the second assembly face (130b) of the first element (130), said second openings being separated from each other by second opening edges (131b), the method then comprising: - (Eli) applying at least one adhesive film comprising a plurality of orifices on the second assembly face (130b) of the first element (130), the centers of the orifices of the adhesive film coinciding with the center of the second openings of the second assembly face (130b) of the first element (130), - (E12) a first heat treatment of the adhesive film applied to the second assembly face (130b) of the first element (130) so that said adhesive film shrinks on the opening edges (131b) and hardens, then - (E13) bringing the fourth element (140) into contact with the second assembly face (130b) of the first element (130), then - (E14) a second heat treatment of the adhesive film applied to the second assembly face (130b) of the first element (130) so as to fix the second assembly face (130b) of the first element (130) to the fourth element (140), this second heat treatment being carried out at the same time as the second heat treatment making it possible to fix the first assembly face (130a) of the first element (130) to the second element (120).
8. A manufacturing method according to any one of claims 1 to 7, wherein: - the first element is an acoustic component (120) whose cells are a plurality of hollow acoustic elements (121) having a shape gradually narrowing between a base (121a) and a top (121b), the bases (121a) of said hollow acoustic elements (121) being connected to each other by connecting edges (122) corresponding to the edges of openings of the assembly face of said first element, and - the second element is an acoustic skin (110).
9. A manufacturing method according to any one of claims 1 to 7, wherein: - the first element is a multicellular body (130) and - the second element is an acoustic component (120) comprising a plurality of hollow acoustic elements (121) having a shape gradually narrowing between a base (121a) and a top (121b), the bases (121a) of said hollow acoustic elements (121) being connected to each other by connecting edges (122), the attachment of the first element to the second element being carried out so that the tops (121b) of the hollow acoustic elements (121) of the second element are arranged in the cells (132) of the first element.
10. A manufacturing method according to claim 6 or 7, wherein: - the first element is a multicellular body (130), - the second element is an acoustic component (120) whose cells are a plurality of hollow acoustic elements (121) having a shape gradually narrowing between a base (121a) and a top (121b), the bases (121a) of said hollow acoustic elements (121) being connected to each other by connecting edges (122) corresponding to the edges of openings in the assembly face of said second element, the attachment of the first element to the second element being carried out so that the tops (121b) of the hollow acoustic elements (121) of the second element are arranged in the cells (132) of the first element, and - the third element is an acoustic skin (110).