Manufacturing of an acoustic panel by bonding with prior heat treatment

Abstract

Manufacturing an acoustic panel by bonding with prior heat treatment. The invention relates to a method for manufacturing an acoustic panel (100) comprising the assembly of at least one first element (130) with a second element (120), the method comprising: - the application of at least one adhesive film (520) comprising a plurality of orifices (521) onto an assembly face (130a) of the first element (130) comprising openings, the centers of the orifices (521) of the adhesive film (520) coinciding with the centers of the openings on the assembly face (130a), - a first heat treatment of the adhesive film (520) such that said adhesive film (520) shrinks and hardens, - bringing the second element (120) into contact with the assembly face (130a) of the first element (130), - a second heat treatment of the adhesive film (520) so as to fix the first element (130) to the second element (120). Figure for the abbreviation: Fig. 12

Description

Title of the invention: Manufacturing an acoustic panel by bonding 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 gas turbines or exhausts thereof. Previous technique

[0002] Acoustic attenuation panels typically consist of a plate or skin with an acoustic surface permeable to the acoustic waves to be attenuated and a solid reflective plate or skin, known as the "closing plate," with a multicellular body positioned between these two surfaces. The multicellular body is generally composed of a series of partitions, for example, in the shape of a honeycomb, delimiting a plurality of cells. As is well known, such panels form Helmholtz-type resonators that attenuate acoustic waves within a certain frequency range, the height of the cavities allowing the selection of the targeted frequency band. Acoustic attenuation panels of this type are described in particular in US patent 5,912,442 and GB patent 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 NIDA-type honeycomb cells, are not suitable for very low frequencies due to the required cavity height and resulting bulk. This is particularly true for acoustic attenuation panels in high bypass ratio turbojets, where the frequencies to be absorbed are between 200 Hz and 400 Hz and where the available space is limited.

[0004] A solution for dealing with low frequencies without resorting to an excessively 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 different assemblies can be made by bonding. Indeed, unlike welding, bonding has the advantage of being able to be carried out with both thermoplastic and thermosetting materials or with combinations of thermoplastic and thermosetting materials.

[0007] However, bonding has many drawbacks. First, positioning the adhesive is difficult, especially on the edges of the acoustic elements or the multicellular body. Furthermore, the adhesive can seep into the acoustic elements or the cells of the multicellular body and partially clog them, thus impairing the acoustic performance of the final acoustic panel. Description of the invention

[0008] The present invention aims to remedy the aforementioned drawbacks by proposing an easy assembly solution for acoustic panels, without risking a decrease in 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 edges of openings, the method being characterized in that it comprises:

[0010] - the application of at least one adhesive film comprising a plurality of orifices on the first assembly face of the first element, the centers of the holes in the adhesive film coinciding with the centers of the first openings of the first assembly face,

[0011] - a first heat treatment of the adhesive film applied to the first face assembly of the first element so that the glue film shrinks on the first edges of the opening 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 face assembly 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 an adhesive film and the initial heat treatment of the adhesive before assembly facilitates the positioning of the adhesive and prevents the presence of adhesive inside the cones of the acoustic component or the cells of the multicellular body. The acoustic performance of the panel The acoustic properties thus obtained are therefore not degraded by the assembly. Furthermore, the assembly method of the invention also has the advantage of being applicable even with non-thermoplastic materials used in the assembly.

[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 glue 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, Faire of each orifice of the glue film associated with a first opening of the first assembly face is between 50% and 75% of Faire of said first opening associated with the first assembly face.

[0019] Thus, a satisfactory compromise is achieved, allowing for a sufficient 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 unnecessary excess glue. This avoids the drawbacks associated with too much glue, such as glue drips or the formation 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] The use of an infrared oven makes it possible to treat large surfaces. An infrared oven also has the advantage of being very responsive, thus allowing the desired temperature to be reached quickly.

[0022] According to another particular embodiment of the invention, the process further includes a step of preparing the first assembly surface of the first element by plasma treatment before the application of the adhesive film.

[0023] Such a preparation step makes it possible to improve the mechanical resistance of the bond by gluing, and to break down the additive molecules which impair the bonding.

[0024] According to another particular embodiment of the invention, the method further comprises assembling 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 one another others by edges of openings, the process further comprising:

[0025] - the application of at least one adhesive film comprising a plurality of orifices on the assembly face of the second element, the centers of the holes in the adhesive film coinciding with the centers of the openings on 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 at the edges of the opening 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 face assembly 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 allowing 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 assembling 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] - the application of at least one adhesive film comprising a plurality of orifices on the second assembly face of the first element, the centers of the holes in the adhesive film coinciding with the centers 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 face assembly of the first element so that the glue film shrinks at the edges of the opening 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 face assembly 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 allowing 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 that gradually narrows 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 the 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 that gradually narrows 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 that gradually narrows 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 the openings of the assembly face of said second element, the fixing 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 that gradually narrows 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 the openings of the assembly face of said second element, the fixing 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] Fig.1 is a schematic exploded perspective view of an acoustic panel obtained by the process of the invention.

[0041] [Fig.2] Fig.2 is a schematic cross-sectional view of the acoustic panel of the [Fig.l].

[0042] [Fig.3] Fig.3 is a flowchart of the method of the invention for assembly of two elements.

[0043] [Fig.4] Fig.4 is a flowchart of the method of the invention for assembly of three elements.

[0044] [Fig. 5] [Fig. 5] is a flowchart of the method of the invention for assembly of three elements.

[0045] [Fig.6] Fig.6 is a schematic top view of the first element on which A film of glue is applied.

[0046] [Fig.7] The [Fig.7] is a schematic cross-sectional view of the first element of the [Fig.6]

[0047] [Fig.8] Fig.8 is a schematic top view of the first element of the figures 6 and 7 after an initial heat treatment of the adhesive film.

[0048] [Fig.9] Fig.9 is a schematic top view of the second element on which A film of glue is applied.

[0049] [Fig. 10] The [Fig. 10] is a schematic cross-sectional view of the second element of the [Fig. 9],

[0050] [Fig. 11] The [Fig. 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] [Fig. 12] is a schematic cross-sectional view of the first element of [Fig. 8], the second element of [Fig. 11], and the third element in contact. Description of 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 functions to allow the sound waves to be attenuated to pass through the acoustic panel 100. To this end, the acoustic skin 110 comprises a plurality of perforations 111, as illustrated in Figures 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 in 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 automated fiber placement (AFP), or by automated tape laying (ATL). Other processes can also be used to manufacture the acoustic skin 110, such as manual laying.

[0055] The acoustic skin with an opening 110 can be made of a thermoplastic material, for example, a thermoplastic matrix composite material comprising fibers. The fibers can be made of carbon, glass, or aramid. The acoustic skin with an opening 110 may not include fibers. The thermoplastic matrix can be made, for example, of polyaryletherketone (PAEK), polyetherketoneketone (PEKK), polyetherimide (PEI), polyphenylene sulfide (PPS), polyethersulfone (PESU), or polycarbonate (PC). The acoustic skin with an opening 110 can also be made of a thermosetting material, for example, a composite material comprising fibers and a thermosetting matrix.

[0056] The closing skin 140 corresponds to a solid surface designed to reflect 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 mounted directly onto 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 automated fiber placement (AFP), or by automated tape laying (ATL). Other processes can also be used to manufacture the closure skin 140. For example, the closure skin can be pre-cured and then bonded to the multicellular body. If the closure skin 140 is made of a thermosetting material, it can be formed and cured directly onto the multicellular body.

[0058] The closing skin 140 can be made of thermoplastic or thermosetting material. The closing skin 140 can 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 closing skin 140 may not comprise fibers. The acoustic opening skin 110 can be made of thermoplastic material, for example, a thermoplastic matrix composite material comprising fibers. The fibers can be carbon, glass, or aramid. The thermoplastic matrix can be made, for example, of po- lyaryletherketone (PAEK), polyetherketoneketone (PEKK), polyetherimide (PEI), polyphenylene sulfide (PPS), polyethersulfone (PESU) or polycarbonate (PC).

[0059] The multicellular body 130 comprises a plurality of septa 131 which form a network of ribs, thus delimiting cells 132. Each septum 131 extends between an upper edge 131a and a lower edge 131b. The upper edges 131a of the septa 131 define a first assembly face 130a of the multicellular body 130. The lower edges 131b of the septa 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] The heights Hnodes cells 132 of the multicellular body 130 are chosen so as to obtain treatment 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 cross-section. Of course, it does not depart from the scope of the invention if the cells 132 of the multicellular body 130 have a square, rectangular, round, or other cross-section.

[0062] The multicellular body 130 can be made of polymer, composite, or metallic material, by additive manufacturing or by conventional means. The multicellular body 130 can also be made in a well-known manner from thermoplastic material by injection molding, bending, or tube assembly. The thermoplastic material can be reinforced with short or long fibers. The multicellular body 130 may be unreinforced.

[0063] The acoustic component 120 comprises a plurality of hollow acoustic elements 121, each having a shape that gradually narrows 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 to the . contact of 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 exhibit 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. Of course, it remains within the scope of the invention if the bases of the hollow acoustic elements have a different 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. Of course, it remains within the scope of the invention if the vertices of the hollow acoustic elements have a different 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 give the acoustic component 120 significant flexibility, which facilitates its shaping and assembly 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 contained within a circle with a diameter between 8 mm and 25 mm. For example, the base 121a of the hollow acoustic elements 121 is contained within a circle with a diameter of 20 mm. Preferably, the apex 121b of the hollow acoustic elements 121 is contained within a circle with a diameter between 1 mm and 10 mm. For example, the apex 121b of the hollow acoustic elements 121 is contained within a circle with a diameter of 5 mm.

[0068] Preferably, the height H^o 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 Hno of the hollow acoustic elements 121 is 20 mm. The height H^o of the hollow acoustic elements 121 is less than the height Hi30 of the cells 132 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 made in a well-known manner by Injection-compression molding of a thermoplastic material. Injection-compression involves injecting the material into a partially open mold. Thus, even though the material solidifies rapidly upon contact with the mold due to the significant temperature difference between the tooling and the molten material, the mold cavity becomes less clogged, and the pressure required for injection remains manageable. Once the entire volume of material is injected into the cavity and evenly distributed throughout the mold, the mold is completely closed by a closing force to force the material into the most complex areas and return to the correct dimensions. This allows for thinner wall thicknesses for acoustic components than with a conventional injection molding process.

[0071] The acoustic component 120 can also be produced in a well-known manner by injection molding with temperature control of the molding from a thermoplastic material. Injection molding with temperature control of the molding consists of controlling the temperature of the molding or the mold by means of a mold 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 can, for example, be made of polyetherimide (PEI) or polyethersulfone (PESU) to facilitate its manufacture and shaping after fabrication.

[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, still within the scope of the invention if the acoustic panel comprises several superimposed multicellular bodies. Nor is it within the scope of the invention if the acoustic panel comprises several acoustic components. The acoustic panel may also include intermediate acoustic skins delimiting different layers of said acoustic panel.

[0074] As illustrated in Figures 3 to 5, the method according to the invention comprises assembling 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 edges of openings, the method comprising:

[0075] - a first step El of applying at least one adhesive film comprising a plurality of holes on the first assembly face of the first element, the centers of the holes in the adhesive film coinciding with the centers of the first openings on the first assembly face,

[0076] - a second step E2 of first heat treatment of the applied adhesive film on the first assembly face of the first element so that said adhesive film shrinks on the first edges of the opening 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 applied adhesive film on 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 can 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 can 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 edges of openings 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 include the assembly of three or four elements.

[0084] According to a first embodiment, the process 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 process then comprising:

[0085] - a sixth step E6 of applying at least one adhesive film comprising a plurality of holes on the assembly face of the second element, the centers of the holes in the adhesive film coinciding with the centers of the openings on the assembly face of the second element,

[0086] - a seventh step E7 of first heat treatment of the applied adhesive film on the assembly face of the second element so that said adhesive film shrinks at the opening edges and hardens, then

[0087] - an eighth step E8 of bringing the third element into contact with the face assembly of the second element, then

[0088] - a ninth step E9 of second heat treatment of the applied adhesive film on 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 steps E1, E2 and E3 can of course be carried out in parallel with the sixth, seventh and eighth steps 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, which is the acoustic skin 110, can be assembled in addition.

[0092] According to a second embodiment, the process 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 edges of openings, the process then comprising:

[0093] - an eleventh step Eli of applying at least one adhesive film comprising a plurality of holes on the second assembly face of the first element, the centers of the holes in the adhesive film coinciding with the centers of the second openings on the second assembly face of the first element,

[0094] - a twelfth step E12 of first heat treatment of the applied adhesive film on the second assembly face of the first element so that said adhesive film shrinks at 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 steps El, E2 and E3 can of course be carried out in parallel with the eleventh, twelfth and thirteenth steps Ell, E12 and E13.

[0099] The first, sixth, and eleventh steps E1, E6, and E1 will be similar and may have the same characteristics and parameters. The second, seventh, and twelfth steps E2, E7, and E12 will be similar and may have the same characteristics and parameters. The optional fifth, tenth, and fifteenth 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, which is the closing skin 140, can be assembled in addition. 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, which is the acoustic component 120, can be further assembled. 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 performing the first embodiment without performing the second embodiment, as illustrated in [Fig. 4], or by performing the second embodiment without performing the first embodiment (variant not illustrated). Thus, the eleventh, twelfth, and thirteenth steps E1, E12, and E13 can be performed without performing the sixth, seventh, and eighth steps E6, E7, and E8.

[0103] The assembly of four elements can be carried out by carrying out both the first mode and the second mode, as illustrated in [Fig.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, one can 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 specific bonding assembly of the invention can be used solely for assembling the acoustic component 120 to the acoustic skin 110, solely for assembling the multicellular body 130 to the acoustic component 120, or solely for assembling the closing skin 140 to the multicellular body 130. The specific bonding assembly of the invention can also be used solely for assembling the acoustic component 120 simultaneously to the acoustic skin 110 and the multicellular body 130. The specific bonding assembly of the invention can be used solely for assembling the multicellular body 130 simultaneously to the acoustic component 120 and the closing skin 140. The specific bonding 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 achieved, 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 thus place ourselves 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 edges of the openings 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 optional fifth 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 optional fifth step E5 may also include 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 the bonding.

[0110] Plasma treatment can be carried out using atmospheric plasma. A plasma nozzle or head can be used.

[0111] If the element treated by plasma 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, is preferred. The plasma treatment can be carried out by making back-and-forth passes over 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 nozzle feed speed can be between 25 mm.s and 100 mm.s. Plasma treatment can be carried out with a feed speed of approximately 50 mm.s 1 for an acoustic component 120 made of polyetherimide (PEI). .

[0112] If the element treated by plasma is the second assembly surface of the acoustic component 120, a static nozzle is 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 band with a width between 3 mm and 4 mm. The plasma treatment may be carried out with trajectories along two principal directions on the first assembly surface 130a or 120a, along straight trajectories, or along trajectories along the lower faces 122b of the bonding 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 nozzle feed speed can be between 25 mm.s and 100 mm.s.Plasma treatment can be carried out with a feed rate of approximately 25 mm.s 1 for an acoustic component 120. 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 centers of the first openings 132 of the first assembly face 130a. Thus, the first edges of the openings 131a of the first element 130 are completely covered by the adhesive film(s) 520. Preferably, the adhesive film(s) 520 include the orifices 521 before being applied to the first element 130.

[0114] The adhesive film may have a basis weight of 300 g.m2. The adhesive film may 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 shrinkage of the adhesive film 520 on the first edges of the openings 131a.

[0116] It is of course not beyond 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 first associated opening 132.

[0118] The second step E2 is then carried out, in which the adhesive film 520 undergoes a first heat treatment so that the adhesive film 520 shrinks at the first edges of the openings 131a and hardens. This results in cross-linking of the adhesive. As illustrated in [Fig. 8], a cross-linked adhesive film 620 is thus obtained, comprising a plurality of openings 621 with a larger area than the area of ​​the openings 521 of the adhesive film 520 before the first heat treatment.

[0119] The first heat treatment can be carried out in an infrared furnace. 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 at a temperature, pressure, and duration adapted to the first element 130 and the chosen adhesive film 520, in order to obtain satisfactory curing. The selection of these parameters presents no difficulties for those skilled in the art. For example, the first heat treatment can be carried out in an infrared oven for a period of between 2 minutes and 5 minutes at a temperature of 180°C.

[0121] Before proceeding to the third step, steps six, seven and eighth E6 and E7 are preferably carried out, and possibly step ten E10.

[0122] The optional tenth step E10 is a plasma treatment performed at least on the first assembly face 120a of the second element 120. This step aims to improve the mechanical strength of the bond and to break down the functions of any additives present in the material of the second element 120 that impair the 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 the bonding.

[0123] The optional tenth step E10 may also include 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 carried out using atmospheric plasma. A plasma nozzle or head can be used.

[0125] If the element treated by plasma 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, is preferred. The plasma treatment can be carried out by making back-and-forth passes over 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 nozzle feed speed can be between 25 mm.s and 100 mm.s. Plasma treatment can be carried out with a feed speed of approximately 50 mm.s 1 for an acoustic component 120 made of polyetherimide (PEI). .

[0126] If the element treated by plasma is the second assembly surface of the acoustic component 120, a static nozzle is 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 band with a width between 3 mm and 4 mm. The plasma treatment may be carried out with trajectories along two principal directions on the first assembly surface 130a or 120a, along straight trajectories, or along trajectories along the lower faces 122b of the bond 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 This can be achieved with a source distance of approximately 20 mm for a 120 mm acoustic component made of polyetherimide (PEI). The nozzle travel speed can be between 25 mm / s and 100 mm / s. Plasma treatment can be performed with a travel speed of approximately 25 mm / s for a 120 mm 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 centers of the openings in the assembly face 120a of the second element 120. Thus, the edges of the openings 122a of the second element 120 are completely covered by the adhesive film(s) 510. Preferably, the adhesive film(s) 510 include the orifices 511 before being applied to the second element 120.

[0128] The adhesive film may have a basis weight of 300 g.m2. The adhesive film may 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 in the assembly face 120a of the second element 120. Thus, the orifices 511 of the adhesive film 510 and the openings in the assembly face 120a have a hexagonal shape. The use of the same geometric shape allows for more uniform shrinkage of the adhesive film 510 at the edges of the openings 122a.

[0130] It is of course not beyond 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] Next, the seventh step E7 is carried out, in which the adhesive film 510 undergoes a first heat treatment so that the adhesive film 510 shrinks at the edges of the openings 122a and hardens. This results in cross-linking of the adhesive. As illustrated in [Fig. 11], a cross-linked adhesive film 610 is thus obtained, comprising a plurality of openings 611 with a larger area than the openings 511 of the adhesive film 510 before the first heat treatment.

[0133] The first heat treatment can be carried out in an infrared furnace. 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 at a temperature, pressure, and duration adapted to the second element 120 and the chosen adhesive film 510, in order to obtain satisfactory curing. The selection of these parameters presents no 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 and 5 minutes at a temperature of 180°C. These parameters are particularly suitable for treating 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 furnace.

[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, to which the cross-linked 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, to which the cross-linked adhesive film 610 is applied, is brought into contact with the acoustic skin 110.

[0137] Next, the fourth step E4 and the ninth step E9 are carried out. A second heat treatment is thus performed on the crosslinked glue films 610 and 620, 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 furnace, or by any other suitable means.

[0139] The second heat treatment is carried out at a temperature, pressure, and duration adapted to the first element 130, the second element 120, and the third element 110, as well as to the selected crosslinked adhesive films 610 and 620, in order to obtain satisfactory bonding. The selection of these parameters presents no 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 and 6 hours at a temperature of 180°C and a pressure of between 1 and 5 bar. A vacuum bag may be used. For example, the second heat treatment may include applying a temperature ramp of 1°C per minute until reaching 105°C, then maintaining the temperature at approximately 105°C for 1 hour and 30 minutes, and then applying a temperature ramp of 2°C per minute until reaching 180°C. then maintaining the temperature at approximately 180°C for two hours, before cooling and removing the glued assembly.

[0140] This results in an assembly of two, three, four or more elements created by gluing. The assembly is then completed to obtain the desired acoustic panel 100.

[0141] This yields the acoustic panel 100. The acoustic panel 100 can, for example, be used for acoustic attenuation in an aircraft nacelle or engine, for a blade platform, or for an aircraft sleeve. The acoustic panel 100 can, for example, be used to cover the internal fixed section (IFS) of a nacelle, the cowling of an aircraft fan, a sliding aircraft sleeve, an aircraft air intake, or an aircraft wing component. The acoustic panel 100 is particularly suitable for processing low frequencies.

[0142] The expression "between ... and ..." should be understood as including the boundaries.

Claims

Demands

1. A method for 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: - (11) the application of at least one adhesive film (520) comprising a plurality of orifices (521) on 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. A manufacturing method according to claim 1, wherein the orifices (521) of the adhesive film (520) have the same geometric shape as the first openings of the first assembly face (130a).

3. A manufacturing method according to claim 1 or 2, wherein the area of ​​each orifice (521) of the adhesive film (520) associated with a first opening of the first assembly face (130a) is between 50% and 75% of the area of ​​said first opening associated with 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. A manufacturing method according to any one of claims 1 to 4,

6.

7. including further a step (E5) of preparing the first assembly surface (130a) of the first element (130) by plasma treatment before the application of the adhesive film (520). 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) the application of at least one adhesive film (510) comprising a plurality of orifices (511) on 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) such 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 glue 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 allowing the assembly face (130a) of the first element (130) to the second element (120). 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 edges of openings (131b), the method then comprising: - (E11) applying at least one adhesive film comprising a plurality of orifices to the second assembly face (130b) of the first element (130), the centers of the orifices in the adhesive film coinciding with the centers 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) such that said adhesive film shrinks at the edges of the opening (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 is carried out simultaneously with the second heat treatment that fixes 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 that gradually narrows 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 the 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 that gradually narrows between a base (121a) and a vertex (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 such that the vertices (121b) 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 that gradually narrows between a base (121a) and a vertex (121b), the bases (121a) of said hollow acoustic elements (121) being connected to each other by connecting edges (122) corresponding to the edges of the openings of the assembly face of said second element, the attachment of the first element to the second element being carried out such that the vertices (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).

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