Manufacture of an acoustic panel by ultrasonic welding

Abstract

Manufacture of an acoustic panel by ultrasonic welding The invention relates to a method for manufacturing an acoustic panel (100) comprising assembling at least one acoustic component (120) with an acoustic skin (110), said acoustic component (120) comprising a plurality of hollow acoustic elements (121), the bases (121a) of the hollow acoustic elements (121) being connected to each other by connecting edges (122), the assembly comprising bringing the acoustic skin (110) into contact with the connecting edges (122) of said acoustic component (120), the method being characterized in that it further comprises fixing the connecting edges (122) to the acoustic skin (110) by ultrasonic welding. Figure for abstract: Fig. 4

Description

Title of the invention: Manufacture of an acoustic panel by ultrasonic welding 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 are typically made up 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 made up of 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 which make it possible to attenuate the acoustic waves in a certain frequency range. Acoustic attenuation panels of this type are described in particular in documents US 5,912,442 and GB 2,314,526.

[0003] These acoustic attenuation panels are limited to simple cell shapes such as those of the NIDA type honeycomb cells. The attenuated frequency is inversely proportional to the thickness of the panel. Consequently, when it is desired to treat low frequencies, it is necessary to resort to thick multicellular bodies.

[0004] One 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 thus 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] In some configurations, the acoustic panel has a complex and curved shape, for example a double-curved shape. The acoustic component formed by the hollow acoustic elements often cannot be molded directly with a curved shape, so that said hollow acoustic elements remain demoldable. The acoustic component is therefore molded "flat", then shaped to be able to correctly introduce the hollow acoustic elements into the cells of the multicellular body. However, in this way, the hollow acoustic elements do not always position themselves well in the cells of the multicellular body.

[0007] To assemble the hollow acoustic elements with the acoustic skin, glue can be used. However, there is a risk that the glue will fall inside said hollow acoustic elements. However, the presence of glue inside the hollow acoustic elements would lead to a deterioration in the acoustic performance. In addition, the hollow acoustic elements are made of thermoplastic material, possibly including additives to facilitate demolding. However, bonding such thermoplastic materials is more complex to implement than bonding thermosetting materials. Thus, bonding the hollow acoustic elements may require additional surface preparation steps which increase the cost of the process.

[0008] The assembly of the hollow acoustic elements with the acoustic skin can also be carried out by conduction welding. However, the risk of deforming the hollow acoustic elements under the effect of the heat provided by the conduction to carry out the welding is significant, while such deformation would lead to a degradation of the acoustic performance. This risk of deformation under the effect of heat is all the higher when the hollow acoustic elements are thin and thin. Statement of the invention

[0009] The present invention aims to remedy the aforementioned drawbacks by proposing an easy solution for assembling the hollow acoustic elements to the acoustic skin without risking reducing the acoustic performance of the acoustic panel obtained.

[0010] To this end, the invention proposes a method for manufacturing an acoustic panel comprising the assembly of at least one acoustic component with an acoustic skin, said acoustic component comprising a plurality of hollow acoustic elements extending from a base, the bases of the hollow acoustic elements being connected to each other by connecting edges, the assembly comprising bringing the acoustic skin into contact with the connecting edges of said acoustic component, the method being characterized in that it further comprises fixing the connecting edges to the acoustic skin by ultrasonic welding.

[0011] Thus, the assembly is carried out by ultrasonic welding. In addition to being a very rapid welding method, this method has the advantage of being very localized, thus greatly reducing the risk of deformation of the hollow acoustic elements compared to conduction welding. In addition, compared to solutions using glue to fix the connecting edges of the acoustic component to the acoustic skin, This prevents the glue from falling into the hollow acoustic elements and thus reducing the acoustic performance of the acoustic panel.

[0012] Furthermore, in the case where it is desired to produce an acoustic panel of complex and curved shape, the method of the invention makes it possible to facilitate the progressive shaping of the acoustic panel to the correct curvature and to maintain said desired shape.

[0013] Hollow acoustic elements have a shape that gradually tapers between the base and a top.

[0014] According to a particular embodiment of the invention, ultrasonic welding is carried out by applying at least one sonotrode in contact with the connecting edges of the acoustic component or the portions of the acoustic skin intended to be welded, said sonotrode transmitting to the connecting edges of the acoustic component or to the portions of the acoustic skin intended to be welded ultrasonic waves generated by a converter so as to cause localized heating. Thus, said sonotrode transmits to the connecting edges of the acoustic component or to the portions of the acoustic skin intended to be welded ultrasonic waves generated by a converter so as to cause localized heating at the contact interface between the connecting edges and the acoustic skin causing the welding of said connecting edges to the acoustic skin.

[0015] This ultrasonic welding method is particularly suitable for welding the connecting edges to the acoustic skin.

[0016] According to another particular embodiment of the invention, a compacting device is used to compress the bonding edges against the acoustic skin before ultrasonic welding.

[0017] Carrying out upstream compaction makes welding easier and improves the quality of the weld as well as its sealing.

[0018] The compacting device may take the form of at least one roller configured to roll in contact with the tops of several acoustic elements of the acoustic component prior to ultrasonic welding.

[0019] The compacting device may take the form of at least one roller configured to roll in contact with the bonding edges of the acoustic component prior to ultrasonic welding.

[0020] According to another particular embodiment of the invention, the ultrasonic welding is carried out so as to obtain continuous weld beads extending from one side of the acoustic component to the other.

[0021] Such uninterrupted weld seams make it possible to achieve a seal between the acoustic component and the acoustic skin, which guarantees excellent acoustic performance.

[0022] According to another particular embodiment of the invention, the ultrasonic welding is carried out so as to obtain discontinuous weld beads extending from one side of the acoustic component to the other, the cumulative lengths of the discontinuities of the weld beads representing less than 50% of the total length of the weld beads.

[0023] Weld seams with such short interruptions provide a reasonable seal while still allowing fluids to pass through. For example, if the acoustic panel is to be positioned in an aircraft, discontinuities allowing fluids to pass through in operation are desirable.

[0024] According to another particular embodiment of the invention, the acoustic component is made of thermoplastic material.

[0025] According to another particular embodiment of the invention, the acoustic skin is made of a thermoplastic matrix composite material.

[0026] According to another particular embodiment of the invention, at least the portions of the acoustic skin intended to be welded to the connecting edges of the acoustic component are covered by a layer of thermoplastic resin devoid of fibers.

[0027] Such a layer of pure resin allows better control of ultrasonic welding, by ensuring a satisfactory and homogeneous quantity of material. The layer of pure resin can also facilitate the transmission of vibrations and by ensuring a homogeneous and controlled propagation of said vibrations.

[0028] According to another particular embodiment of the invention, the acoustic skin has a plurality of perforations before being assembled with the acoustic component.

[0029] By making the perforations before assembly, there is no risk of damaging the hollow acoustic elements when making said perforations.

[0030] According to another particular embodiment of the invention, the method further comprises the assembly of at least one multicellular body with one or more acoustic components, the assembly between the multicellular body(ies) and the acoustic component(s) being carried out so that the tops of the hollow acoustic elements are arranged in the cells of the multicellular body(ies). Brief description of the drawings

[0031] [Fig.l] [Fig.l] is a schematic exploded perspective view of an acoustic panel obtained by the method of the invention.

[0032] [Fig.2] [Fig.2] is a schematic sectional view of the acoustic panel of [Fig.l].

[0033] [Fig.3] [Fig.3] is a schematic sectional view illustrating the contacting of the acoustic component with the acoustic skin.

[0034] [Fig.4] [Fig.4] is a schematic sectional view illustrating the welding of the acoustic component to the acoustic skin by means of an ultrasonic welding device.

[0035] [Fig.5] [Fig.5] is a schematic top view illustrating the trajectories of the or the sonotrodes of the ultrasonic welding device. Description of the embodiments

[0036] 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.

[0037] 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. Each perforation 111 of the acoustic skin 110 preferably corresponds to a cell of the multicellular body 130 and to a hollow acoustic element 121 of the acoustic component 120. The acoustic skin 110 may have a thickness of between 1 mm and 5 mm, for example 2 mm.

[0038] 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 draping known as “ATL” for “Automated Tape Lying”. Other methods can also be used to manufacture the acoustic skin 110, such as manual draping.

[0039] The acoustic skin 110 may be made of thermoplastic material, for example a composite material with a thermoplastic matrix comprising fibers. The fibers may be carbon, glass or aramid. The 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).

[0040] In order to facilitate the ultrasonic welding step, at least the portions of the acoustic skin 110 intended to be welded to the acoustic component 120 are covered by a layer of thermoplastic resin devoid of fibers. Indeed, such a layer of thermoplastic resin makes it possible to ensure a satisfactory and homogeneous quantity of material, in order to obtain better controlled welding.

[0041] 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.

[0042] The closure skin 140 can be produced in a well-known manner by stamping, by automatic fiber placement called “AFP” for “Automated Fiber Placement”, or by automatic tape draping called “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 then assembled by gluing on the multicellular body, or can be formed and baked directly on the multicellular body.

[0043] The closing 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 closing skin 140 may not comprise fibers. The 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 thermoplastic matrix may be made for example of polyaryletherketone (PAEK), polyetherketoneketone (PEKK), polyetherimide (PEI), polyphenylene sulfide (PPS), polyethersulfone (PESU) or polycarbonate (PC).

[0044] 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.

[0045] The heights of the 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.

[0046] 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 not departing from the scope of the invention if the cells 132 of the multicellular body 130 have a square, rectangular, round or other section.

[0047] 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 in 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.

[0048] The acoustic component 120 comprises a plurality of hollow acoustic elements 121 each having a shape gradually narrowing 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.

[0049] 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.

[0050] 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 tops 121b of the hollow acoustic elements 121 have a hexagonal geometry. It is of course not beyond the scope of the invention if the tops of the hollow acoustic elements have another geometry, for example a circular, square or rectangular geometry.

[0051] 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 on the acoustic component 120, which makes it easier to shape it and assemble it against the acoustic skin 110.

[0052] 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.

[0053] 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 H^o of the hollow acoustic elements 121 is 20 mm. The height H^o of the hollow acoustic elements 121 is less than the height Hnodes cells 132 of the multicellular body 130.

[0054] The acoustic component 120 can be produced in a well-known manner by additive manufacturing, injection or stamping.

[0055] 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, the channels become less obstructed. When the material is distributed throughout the mold, the latter is completely closed by a closing force to return to the correct dimension. This makes it possible to obtain thinner wall thicknesses for the acoustic components than with a conventional injection process.

[0056] The acoustic component 120 can also be produced in a well-known manner by injection with control of the temperature of the tooling of a thermoplastic material. Injection with control of the temperature of the tooling consists of controlling the temperature of the tooling or the mold by means of a system for controlling the temperature of the tooling, for example with a heat transfer fluid or with air.

[0057] The acoustic component 120 is preferably made of thermoplastic material to facilitate its manufacture. The acoustic component 120 is preferably made of 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 its shaping after manufacture.

[0058] In the example illustrated in Figures 1 and 2, the acoustic panel 100 comprises only a single multicellular body and a single acoustic component. 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. In this configuration, an acoustic component may have a width of between between 200 mm and 1000 mm and a length between 200 mm and 1000 mm. The acoustic panel may also include intermediate acoustic skins delimiting different levels of said acoustic panel.

[0059] The assembly of the acoustic component 120 with the acoustic skin 110 comprises a contacting step, possibly a position holding step and a welding step.

[0060] During the contacting step, the acoustic component 120 is placed in contact with the acoustic skin 110, as illustrated in [Fig. 3]. More precisely, the first assembly face 120a of the acoustic component 120 is placed in contact with the acoustic skin 110, that is to say the upper faces 122a of the edges 122 are placed in contact with the acoustic skin 110.

[0061] Preferably, the acoustic skin 110 already has the perforations 111 before being assembled to the acoustic component 120. In this configuration, the acoustic component 120 is arranged in contact with the acoustic skin 110 so that the perforations 111 open inside the hollow acoustic elements 121 and not on the connecting edges 122. By making the perforations 111 of the acoustic skin 110 before assembly, the risk of the hollow acoustic elements 121 being damaged by a perforation step after assembly is avoided.

[0062] The contacting can be carried out manually, or by means of a robot and grippers. The use of a robot makes it possible to automate the assembly. The acoustic skin 110 can be arranged on fixed or mobile tooling.

[0063] The acoustic component 120 is then held in position in contact with the acoustic skin 110, i.e. the upper faces 122a of the edges 122 are held in position in contact with the acoustic skin 110. This holding in position will continue during the welding step, in order to ensure satisfactory welding. Preferably, the holding in position is achieved by applying pressure so that the upper faces 122a of the edges 122 are pressed against the acoustic skin 110. Welding is thus facilitated.

[0064] The positioning can be carried out manually, or by means of a robot and grippers. The use of a robot makes it possible to automate the assembly. The robot used for positioning is preferably the same as that used for contacting. The acoustic skin 110 can be arranged on fixed or mobile tooling, preferably on the same tooling as that used for contacting.

[0065] The ultrasonic welding step is then carried out, as illustrated in Figures 4 and 5.

[0066] The ultrasonic welding step is preferably carried out by means of one or more sonotrodes 61. The welding step can be carried out by means of a device 60 ultrasonic welding comprising at least one sonotrode 61, a converter 63 and a generator 64.

[0067] The generator 64 is configured to supply the converter 63 with energy, preferably with electrical energy. The converter 63 is configured to convert the energy supplied by the generator 64 into mechanical energy. The converter 63 may conventionally be a piezoelectric converter. The sonotrode 61 is configured to transmit the mechanical movement supplied by the converter 63 to the part to be welded, here to the acoustic component 120. The converter 63 may generate ultrasonic mechanical waves whose frequency is between 16 kHz and 10,000 kHz.

[0068] The ultrasonic welding device 60 may further comprise, in a well-known manner, an amplifier 62 arranged between the sonotrode 61 and the converter 63. The amplifier 62 is configured to amplify the mechanical movement transmitted by the converter 63 to the sonotrode 61.

[0069] The sonotrode(s) 61 are configured to be able to move between the hollow acoustic elements 121 in contact with the lower faces 122b of the connecting edges 122 of the acoustic component 120. Thus, the width of the sonotrode 61 allows the passage of said sonotrode 61 between the hollow acoustic elements 121.

[0070] The sonotrode(s) 61 may be provided with a tip 61a at their end. The tip 61a is configured to be in direct contact with the acoustic component 120 and to transmit the mechanical movement to said acoustic component 120. The tip(s) 61a may be interchangeable. The tip 61a may have several shapes. In the example illustrated in [Fig. 4], the tip 61a comprises a flared shape whose width increases from the end of the sonotrode 61. It is of course not departing from the scope of the invention if the tip 61a has another shape, for example a conical shape, a pyramidal shape, a stepped shape, a rounded shape, a pointed shape, a shovel shape, a bell shape or a rectangular shape. The end of the tip 61a corresponding to the end of the sonotrode 61 can be included in a circle whose diameter is between 1 mm and 2 mm.

[0071] The welding device 60 may further comprise a parameterization system (not shown). The parameterization system is configured to control the energy transferred to the workpiece, or to control the welding time, or both.

[0072] Ultrasonic welding is a fast welding method. The ultrasonic welding performed in the present invention may allow a welding speed of between 0.1 mm.s 1 and 50 mm.s *. For example, the sonotrode(s) 61 may perform the welding of the acoustic component 120 to the acoustic skin 110 by moving at a welding speed of between 0.1 mm.s 1 and 50 mm.s '.

[0073] Several ultrasonic welding modes are possible within the scope of the present invention.

[0074] According to a first welding method, the ultrasonic welding is carried out so as to obtain continuous weld beads extending from one side of the acoustic component 120 to the other, i.e. passing through the acoustic component uninterruptedly. This provides a seal between the bases 121a of the hollow acoustic elements 121 and the acoustic skin 110, which allows for excellent acoustic performance.

[0075] In this first welding mode, the sonotrode 61 welds the acoustic component 120 to the acoustic skin 110 by following paths extending from one edge of the acoustic component 120 to another edge of said acoustic component 120. The paths followed by the sonotrode(s) 61 may extend in at least two general directions, so as to weld all the connecting edges 122. Thus, a plurality of first paths extend in a first direction and a plurality of second paths extend in a second direction.

[0076] In the schematic example illustrated in [Fig. 5], the sonotrode 61 welds the acoustic component 120 along a plurality of first paths Ti directed along a first direction Db and along a plurality of second paths T2 directed along a second direction D2. The first and second directions Di and D2 constitute general directions. The first paths Ti followed by the sonotrode 61 extend from a first edge 120e of the acoustic component 120 to a second edge 120f of the acoustic component 120. The second paths T2 followed by the sonotrode 61 extend from a third edge 120c of the acoustic component 120 to a fourth edge 120d of the acoustic component 120.

[0077] According to a second welding method, the ultrasonic welding is carried out so as to obtain discontinuous weld beads extending from one side of the acoustic component to the other, the cumulative lengths of the discontinuities of the weld beads representing less than 50% of the total length of the weld beads, or even representing less than 20% of the total length of the weld beads. Preferably, each discontinuity in a weld bead has a length less than or equal to 2 mm. Thus, the ultrasonic welding is carried out so as to obtain weld beads passing through the acoustic component with short interruptions.This provides a certain seal between the bases 121a of the hollow acoustic elements 121 and the acoustic skin 110, which provides good acoustic performance, while allowing the evacuation of fluids when the acoustic panel 100 is placed on a machine or system in operation, for example an aircraft.

[0078] Such weld beads with interruptions can follow the same paths and directions as those described in the first welding method.

[0079] In the context of the method of the invention, a compacting device can be used to compress the connecting edges 122 against the acoustic skin 110 before the passage of the sonotrode 61.

[0080] According to a first embodiment of the invention, the compacting device may take the form of one or more rollers configured to roll in contact with the tops 121b of the acoustic elements 121 of the acoustic component 120 before the sonotrode 61 passes. The roller has a width greater than the diameter of the circle in which the base 121a of a hollow acoustic element 121 of the acoustic component 120 is inscribed. Thus, the roller may be configured to cover, completely or partially, several hollow acoustic elements 121 simultaneously. For example, the roller may be configured to cover, completely or partially, two to ten hollow acoustic elements 121 simultaneously. The roller is flexible so as not to damage the tops 121b of the acoustic elements 121.In the case where the acoustic component 120 is welded to the acoustic skin 110 so as to form a curved assembly, for example with double curvature, the flexibility of the roller makes it possible to adapt to the curvatures of the acoustic component 120. The pressure applied by the roller can be between 1 bar and 5 bars. Such pressures make it possible to apply a satisfactory pressure for welding, while not risking damaging or deforming the hollow acoustic elements 121.

[0081] According to a second embodiment illustrated in [Fig. 5], the compacting device may take the form of one or more rollers 71 configured to roll in contact with the lower faces 122b of the connecting edges 122 of the acoustic component 120 before the sonotrode 61 passes. Thus, the width of the roller 71 allows the passage of said roller 71 between the hollow acoustic elements 121 in contact with the lower faces 122b of the connecting edges 122. The pressure applied by the roller may be between 1 bar and 5 bars. Such pressures make it possible to apply a satisfactory pressure for welding, while not risking damaging or deforming the acoustic component 120.

[0082] In order to manufacture the acoustic panel 100, the acoustic component 120 is assembled with the multicellular body 130, so that the upper edges 131a of the partitions 131 are fixed in contact with the lower faces 122b of the connecting edges 122 of the acoustic component 120. Thus, the second assembly face 120b of the acoustic component 120 is fixed in contact with the first assembly face 130a of the multicellular body 130. The assembly of the acoustic component 120 to the multicellular body 130 can for example be carried out by welding or by gluing.

[0083] If the assembled acoustic skin 110 and acoustic component 120 have a curved shape, the multicellular body 130 may already have a suitable curved shape before assembly, or may be shaped directly in contact with the acoustic component 120. The fact that the acoustic component 120 is already assembled and bonded to the acoustic skin 110 before assembly of the multicellular body in this curved configuration makes it easier to assemble the multicellular body 130 so that the hollow acoustic elements 121 are present in the cells 132 of the multicellular body 130. If the multicellular body 130 is assembled to the acoustic component 120 by gluing, better control of the glued interfaces is also obtained.

[0084] If a closure skin 140 is present, the skin of the closures 140 is assembled with the multicellular body 130, so that the lower edges 131b of the partitions 131 are fixed in contact with the closure skin 140. Thus, the second assembly face 130b of the multicellular body 130 is fixed in contact with the acoustic skin 140. The assembly of the closure skin 140 to the multicellular body 130 can for example be carried out by welding or by gluing. The closure skin 140 can also be formed directly by automatic deposition of fibers on the multicellular body 130, the heating tooling of the deposition head allowing the welding of the deposited strips with the lower edges 131b of the partitions 131.

[0085] 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.

[0086] 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 acoustic component (120) with an acoustic skin (110), said acoustic component (120) comprising a plurality of hollow acoustic elements (121) extending from a base, the bases (121a) of the hollow acoustic elements (121) being connected to each other by connecting edges (122), the assembly comprising bringing the acoustic skin (110) into contact with the connecting edges (122) of said acoustic component (120), the method being characterized in that it further comprises attaching the connecting edges (122) to the acoustic skin (110) by ultrasonic welding and in that a compacting device (71) is used to compress the connecting edges (122) against the acoustic skin (110) before ultrasonic welding.

2. Manufacturing method according to claim 1, wherein the ultrasonic welding is carried out by applying at least one sonotrode (61) in contact with the connecting edges (122) of the acoustic component (120) or the portions of the acoustic skin (110) intended to be welded, said sonotrode (61) transmitting to the connecting edges (122) of the acoustic component (120) or to the portions of the acoustic skin (110) intended to be welded ultrasonic waves generated by a converter (63) so as to cause localized heating.

3. A manufacturing method according to claim 1 or 2, wherein the ultrasonic welding is carried out so as to obtain continuous weld beads extending throughout the acoustic component (120).

4. A manufacturing method according to claim 1 or 2, wherein the ultrasonic welding is carried out so as to obtain discontinuous weld beads extending throughout the acoustic component (120), the cumulative lengths of the discontinuities of the weld beads representing less than 50% of the total length of the weld beads.

5. A manufacturing method according to any one of claims 1 to 4, wherein the acoustic component (120) is made of thermoplastic material.

6. Manufacturing method according to any one of claims 1 to 5, in which the acoustic skin (110) is made of thermoplastic matrix composite material.

7. Manufacturing method according to any one of claims 1 to 6, in which at least the portions of the acoustic skin (110) intended to be welded to the connecting edges (122) of the acoustic component (120) are covered by a layer of thermoplastic resin devoid of fibers.

8. A method according to any one of claims 1 to 7, wherein the acoustic skin (110) has a plurality of perforations (111) before being assembled with the acoustic component (120).

9. A method according to any one of claims 1 to 8, the method further comprising assembling at least one multicellular body (130) with one or more acoustic components (120), the assembly between the at least one multicellular body (130) and the at least one acoustic component (120) being carried out such that the tops (121b) of the hollow acoustic elements (121) are arranged in the cells (132) of the at least one multicellular body (130).

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