Manufacturing an acoustic panel by ultrasonic welding

Abstract

The invention relates to a method for manufacturing an acoustic panel (100), which comprises assembling at least one acoustic component (120) with an acoustic skin (110), the acoustic component (120) comprising a plurality of hollow acoustic elements (121), the bases (121a) of the hollow acoustic elements (121) being connected to one another by connecting edges (122), the assembly comprising placing the acoustic skin (110) in contact with the connecting edges (122) of the acoustic component (120), the method being characterised in that it further comprises attaching the connecting edges (122) to the acoustic skin (110) by ultrasonic welding.

Description

Description Title of the invention: Manufacturing an acoustic panel by ultrasonic welding Technical Field

[0001] The present invention relates to the general field of acoustic attenuation structures. More particularly, it relates to acoustic attenuation structures used to reduce noise produced in aircraft engines, such as gas turbines or exhaust systems. Previous technique

[0002] Acoustic attenuation panels typically consist of a surface plate or skin with acoustic permeability to the sound waves to be attenuated, and a solid, reflective plate or skin known as the "closing plate," with a multicellular body sandwiched between these two surfaces. The multicellular body is generally composed of a series of partitions, for example, in a honeycomb pattern, delimiting a plurality of cells. As is well known, such panels form Helmholtz resonators that attenuate sound waves within a specific frequency range. Acoustic attenuation panels of this type are described in US patent 5,912,442 and GB patent 2,314,526.

[0003] These acoustic attenuation panels are limited to simple cell shapes, such as the honeycomb structure of the NIDA type. The attenuated frequency is inversely proportional to the panel thickness. Consequently, when treating low frequencies, thick multi-cell panels are necessary.

[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 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] In some configurations, the acoustic panel has a complex, curved shape, such as a double-curvature. The acoustic component formed by the hollow acoustic elements often cannot be molded directly into a curved shape to ensure the hollow elements remain demoldable. Therefore, the acoustic component is molded flat and then shaped to allow the hollow acoustic elements to be correctly inserted into the cells of the multicellular body. However, this method does not always result in the hollow acoustic elements being positioned correctly within the cells of the multicellular body.

[0007] To bond the hollow acoustic elements to the acoustic skin, adhesive can be used. However, there is a risk that the adhesive may seep inside the hollow acoustic elements. The presence of adhesive inside the hollow acoustic elements would impair their acoustic performance. Furthermore, the hollow acoustic elements are made of thermoplastic material, possibly containing additives to facilitate demolding. Bonding such thermoplastic materials is more complex than bonding thermosetting materials. Therefore, bonding the hollow acoustic elements may require additional surface preparation steps, increasing the cost of the process.

[0008] The hollow acoustic elements can also be joined to the acoustic skin by conduction welding. However, there is a significant risk of deforming the hollow acoustic elements due to the heat generated during the welding process, and such deformation would lead to a degradation of acoustic performance. This risk of heat-induced deformation is even greater when the hollow acoustic elements are thin and of low thickness. Description of the invention

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

[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 using ultrasonic welding. In addition to being a very fast welding method, this method has the advantage of being highly localized, thereby significantly reducing the risk of deformation of the hollow acoustic elements compared to conduction welding. Furthermore, compared to solutions using adhesive to fix the bonding edges of the acoustic component to the acoustic skin, this method prevents the adhesive 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 process 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 narrows between the base and a top.

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

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

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

[0017] Performing upstream compaction makes welding easier and improves weld quality and sealing.

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

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

[0020] According to another particular embodiment of the invention, ultrasonic welding is carried out in such a way as to obtain continuous weld beads extending through and through the acoustic component.

[0021] Such uninterrupted weld beads 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, ultrasonic welding is carried out so as to obtain discontinuous weld beads extending through the entire acoustic component, the cumulative lengths of discontinuities in weld beads representing less than 50% of the total length of the weld beads.

[0023] Weld seams with such short interruptions provide reasonable sealing while allowing fluid passage. For example, if the acoustic panel is intended for use in an aircraft, discontinuities allowing fluid passage during 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 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 fiber-free thermoplastic resin.

[0027] Such a layer of pure resin allows for better control of ultrasonic welding by ensuring a sufficient and homogeneous amount of material. The pure resin layer can also facilitate vibration transmission, 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, we eliminate the risk of damaging the hollow acoustic elements during the making of said perforations.

[0030] According to another particular embodiment of the invention, the method further comprises assembling 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 such that the vertices of the hollow acoustic elements are arranged in the cells of the multicellular body or bodies. Brief description of the drawings

[0031] [Fig. 1] Figure 1 is a schematic exploded perspective view of an acoustic panel obtained by the process of the invention.

[0032] [Fig. 2] Figure 2 is a schematic cross-sectional view of the acoustic panel in Figure 1.

[0033] [Fig. 3] Figure 3 is a schematic cross-sectional view illustrating the contact of the acoustic component with the acoustic skin.

[0034] [Fig. 4] Figure 4 is a schematic cross-sectional view illustrating the welding of the acoustic component to the acoustic skin using an ultrasonic welding device.

[0035] [Fig. 5] Figure 5 is a schematic top view illustrating the trajectories of the sonotrode(s) of the ultrasonic welding device. Description of the implementation methods

[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 the acoustic panel 100. For this purpose, the acoustic skin 110 comprises a plurality of perforations 111, as illustrated in Figures 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 can 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 way 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 processes can also be used to manufacture the acoustic skin 110, such as manual draping.

[0039] The acoustic skin 110 can be made of thermoplastic material, for example, a thermoplastic matrix composite material containing fibers. The fibers can be carbon, glass, or aramid. The acoustic skin 110 may also be made without fibers. The thermoplastic matrix can be made, for example, of polyaryletherketone (PAEK), polyetherketoneketone (PEKK), polyetherimide (PEI), polyphenylene sulfide (PPS), polyethersulfone (PESU), or polycarbonate (PC).

[0040] 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 coated with a layer of fiber-free thermoplastic resin. This layer of thermoplastic resin ensures a sufficient and homogeneous amount of material, resulting in more controlled welding.

[0041] The closing skin 140 is a solid surface designed to reflect sound waves entering the acoustic panel 100. The closing skin 140 can be an integral part of the acoustic panel, as in the example described here, or it can be part of the structure of an object, such as an aircraft engine. In the latter case, the acoustic panel does not have a closing skin and is mounted directly onto the object's structure. The closing skin 140 can have a thickness between 1 mm and 5 mm, for example, 2 mm.

[0042] The 140 closure skin can be manufactured using well-known methods such as stamping, automated fiber placement (AFP), or automated tape laying (ATL). Other processes can also be used to manufacture the 140 closure skin. For example, the closure skin can be pre-cured and then bonded to the multicellular body, or it can be formed and cured directly onto the multicellular body.

[0043] The closing skin 140 can be made of a composite material containing fibers, for example, a composite material based on carbon fibers impregnated with a thermoplastic or thermosetting resin. The closing skin 140 may also be made without fibers. The acoustic skin 110 can be made of a thermoplastic material, for example, a thermoplastic matrix composite material containing 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 septa 131 which form a network of ribs, thus delimiting cells 132. Each septum 131 extends between a superior edge 131a and a inferior edge 131b. The superior edges 131a of the septa 131 define a first assembly face 130a of the multicellular body 130. The inferior 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.

[0045] HI heights 30 cells 132 of the multicellular body 130 are chosen so as to obtain processing of interesting frequencies 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 cross-section. Of course, it remains within the scope of the invention if the cells 132 of the multicellular body 130 have a square, rectangular, round, or other cross-section.

[0047] The 130 multicellular body can be manufactured from polymer, composite, or metallic materials, either by additive manufacturing or conventional methods. It can also be produced using well-known thermoplastic techniques such as injection molding, bending, or tube assembly. The thermoplastic material can be reinforced with short or long fibers. Alternatively, the 130 multicellular body can be manufactured unreinforced.

[0048] 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 specifically, 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 exhibit 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. 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.

[0051] The hollow acoustic elements 121 can have a wall thickness ranging from 0.25 mm to 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 allows, in particular, for significant flexibility in the acoustic component 120, which facilitates its shaping and assembly against the acoustic skin 110.

[0052] 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.

[0053] Preferably, the height H120 of the hollow acoustic elements 121 is between 5 mm and 100 mm, and preferably between 5 mm and 50 mm. For example, the height H120 of the hollow acoustic elements 121 is 20 mm. The height H120 of the hollow acoustic elements 121 is less than the height Hi 30 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 120 acoustic component can also be manufactured using a well-known injection-compression process with a thermoplastic material. Injection-compression involves injecting the material into a partially open mold. This means that even if the material solidifies, the channels become less obstructed. Once the material is distributed throughout the mold, it is completely closed by a clamping force to return to the correct dimensions. This allows for thinner wall thicknesses for acoustic components than with a conventional injection molding process.

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

[0057] Acoustic component 120 is preferably made of thermoplastic material to facilitate its manufacture. Acoustic component 120 is preferably made of amorphous thermoplastic material to facilitate its shaping. For example, acoustic component 120 can be made of polyetherimide (PEI) or polyethersulfone (PESU) to facilitate its manufacture and shaping after fabrication.

[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. Of course, the invention remains within the scope of the invention if the acoustic panel comprises several superimposed multicellular bodies. Nor does the invention depart from the scope of the invention if the acoustic panel comprises several acoustic components. In this configuration, an acoustic component may have a width 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 layers of said acoustic panel.

[0059] The assembly of the acoustic component 120 with the acoustic skin 110 includes a contacting step, possibly a holding-in-position 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 Figure 3. More specifically, the first assembly face 120a of the acoustic component 120 is placed in contact with the acoustic skin 110, i.e. 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 positioned in contact with the acoustic skin 110 of so that the perforations 111 open into the hollow acoustic elements 121 and not onto 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 contact can be made manually, or using a robot and grippers. Using a robot automates the assembly process. The 110 acoustic skin can be mounted on fixed or mobile tooling.

[0063] The acoustic component 120 is then held in position against the acoustic skin 110, that is, the upper surfaces 122a of the edges 122 are held in contact with the acoustic skin 110. This positioning will continue during the welding stage to ensure a satisfactory weld. Preferably, the positioning is achieved by applying pressure so that the upper surfaces 122a of the edges 122 are pressed against the acoustic skin 110. This facilitates welding.

[0064] Positioning can be performed manually or using a robot and grippers. Using a robot automates the assembly process. The robot used for positioning is preferably the same one used for contacting the components. The acoustic skin 110 can be mounted on fixed or mobile tooling, preferably the same tooling used for contacting the components.

[0065] The next step is ultrasonic welding, as illustrated in figures 4 and 5.

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

[0067] The generator 64 is configured to supply power to the converter 63, preferably electrical power. The converter 63 is configured to convert the power supplied by the generator 64 into mechanical power. Converter 63 can typically be a piezoelectric converter. The sonotrode 61 is configured to transmit the mechanical motion provided by converter 63 to the workpiece, in this case the acoustic component 120. Converter 63 can generate ultrasonic mechanical waves with frequencies ranging from 16 kHz to 10,000 kHz.

[0068] The ultrasonic welding device 60 may further include, in a well-known manner, an amplifier 62 disposed between the sonotrode 61 and the converter 63. The amplifier 62 is configured to amplify the mechanical motion 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 fitted 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 motion of said acoustic component 120. The tip(s) 61a may be interchangeable. The tip 61a may have several shapes. In the example illustrated in Figure 4, the tip 61a has a flared shape whose width increases from the end of the sonotrode 61. Of course, it does not depart 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 include 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 can achieve a welding speed of between 0.1 mm / s 1 and 50 mm.s' 1 For example, the sonotrode(s) 61 can 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 1 .

[0073] Several ultrasonic welding methods are possible within the framework of the present invention.

[0074] According to a first welding method, ultrasonic welding is performed to obtain continuous weld beads extending through the entire acoustic component 120, i.e., passing uninterrupted through the acoustic component. This creates a seal between the bases 121a of the hollow acoustic elements 121 and the acoustic skin 110, resulting in excellent acoustic performance.

[0075] In this first welding method, the sonotrode 61 welds the acoustic component 120 to the acoustic skin 110 along 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 can extend in at least two general directions, so as to weld all the bonding 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 Figure 5, the sonotrode 61 welds the acoustic component 120 along a plurality of first paths Ti directed along a first direction Di, 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, ultrasonic welding is performed to obtain discontinuous weld beads extending throughout the acoustic component. The cumulative length of these discontinuities in the weld beads represents less than 50% of the total weld bead length, or even less than 20% of the total weld bead length. Preferably, each discontinuity in a weld bead has a length of 2 mm or less. Thus, ultrasonic welding is performed to obtain weld beads that traverse 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 allows for 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 process of the invention, a compaction device can be used to compress the bonding edges 122 against the acoustic skin 110 before the passage of the sonotrode 61.

[0080] According to a first embodiment of the invention, the compaction device may take the form of one or more rollers configured to roll in contact with the peaks 121b of the acoustic elements 121 of the acoustic component 120 before the passage of the sonotrode 61. 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 can be configured to cover, completely or partially, several hollow acoustic elements 121 simultaneously. For example, the roller can 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 peaks 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 shape assembly, for example with a double curvature, the flexibility of the roller allows. 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 allow for the application of sufficient pressure for welding, without risk of damaging or deforming the hollow acoustic elements 121.

[0081] According to a second embodiment illustrated in Figure 5, the compaction device can 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 passage of the sonotrode 61. Thus, the width of the roller 71 allows the roller 71 to pass between the hollow acoustic elements 121 in contact with the lower faces 122b of the connecting edges 122. The pressure applied by the roller can be between 1 bar and 5 bar. Such pressures make it possible to apply sufficient pressure for welding, without risking damage to or deformation of the acoustic component 120.

[0082] 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 it 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 the assembly of the multicellular body in this curved configuration facilitates the assembly of 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 bonded to the acoustic component 120, this also provides better control of the bonded interfaces.

[0084] If a closure skin 140 is present, the closure skin 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 bonding. The closure skin 140 can also be formed directly by automatic fiber deposition onto the multicellular body 130, the heating tooling of the deposition head enabling the bonding of the deposited strips to the lower edges 131b of the partitions 131.

[0085] This results in the Acoustic Panel 100. The Acoustic Panel 100 can be used, for example, for acoustic attenuation in an aircraft nacelle or engine, for a blade platform, or for an aircraft sleeve. The Acoustic Panel 100 can also 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 well-suited for treating low frequencies.

[0086] The expression "between ... and ..." should be understood as including the boundaries.

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, wherein the compacting device is formed by at least one roller configured to roll in contact with the tops (121b) of the acoustic elements (121) of the acoustic component (120).

10. Method according to any one of claims 1 to 8, wherein the compacting device is formed by at least one roller (71) configured to roll in contact with the connecting edges (122) of the acoustic component (120).

11. A method according to any one of claims 1 to 10, 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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