Manufacturing acoustic panel by ultrasonic welding

Abstract

The invention relates to a method of manufacturing an acoustic panel (100), the method comprising: 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 each other by connecting edges (122), the assembly comprises bringing the acoustic skin (110) into contact with a connecting edge (122) of the acoustic component (120), characterized in that the method further comprises attaching the connecting edge (122) to the acoustic skin (110) by ultrasonic welding.

Description

TECHNICAL FIELD

[0001] The present invention relates to the general field of acoustic attenuation structures. More particularly, it relates to acoustic attenuation structures for reducing the noise generated by aircraft engines and gas turbines or their exhausts. BACKGROUND

[0002] Acoustic attenuation panels generally comprise a plate or skin having an acoustic surface capable of permeating acoustic waves for which attenuation is desired and a reflective solid plate or skin, called "closed plate", between which a porous body is arranged. The porous body generally comprises a set of partitions, for example in the form of a honeycomb, defining a plurality of cells. It is known that such a panel forms a Helmholtz-type resonator capable of attenuating acoustic waves in a certain frequency range. This type of acoustic attenuation panel is 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, for example the shape of NIDA-type honeycomb cells. The attenuation frequency is inversely proportional to the thickness of the panel. Thus, when it is necessary to treat low frequencies, it is necessary to use a thick porous body.

[0004] A solution to treat low frequencies without using a too thick porous body is to place hollow acoustic elements, for example open truncated cones, in the cells of the porous 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 assembly formed of hollow acoustic elements, to assemble the hollow acoustic elements with the porous body and to assemble the porous body with the optional closed plate.

[0006] In certain configurations, the acoustic panel has a complex and curved shape, for example a double curved shape. The acoustic assembly formed of hollow acoustic elements cannot generally be molded directly in a curved shape so that the hollow acoustic elements remain demoldable. Thus, the acoustic assembly is molded flat and then shaped so as to be able to correctly introduce the hollow acoustic elements into the cells of the porous body. However, this method does not always allow to correctly place the hollow acoustic elements in the cells of the porous body.

[0007] The hollow acoustic elements can be assembled to the acoustic skin using glue. However, there is a risk that the glue can fall inside the hollow acoustic elements. The presence of glue inside the hollow acoustic elements can cause a degradation of the acoustic performance. Furthermore, the hollow acoustic elements are made of thermoplastic material, optionally containing additives to facilitate demolding. However, gluing such thermoplastic materials is more complex than gluing thermoset materials. Thus, gluing the hollow acoustic elements can require additional surface treatment steps, which increases the cost of the method.

[0008] Hollow acoustic elements can also be assembled with the acoustic skin by conduction welding. However, there is a high risk of deformation of the hollow acoustic elements under the heat action provided by the conduction to perform the welding, and this deformation will result in a degradation of the acoustic performance. The risk of deformation under the heat action increases with the decrease of the thickness of the hollow acoustic elements. SUMMARY

[0009] The aim of the present invention is to remedy the aforementioned drawbacks by proposing a simple solution to assemble hollow acoustic elements to an acoustic skin without risking degrading the acoustic performance of the acoustic panel obtained.

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

[0011] Thus, the assembling is performed by ultrasonic welding. In addition to being a very fast welding method, the advantage of this method is that it is very localized, thus greatly reducing the risk of deformation of the hollow acoustic elements compared to conduction welding. Furthermore, compared to the solution of attaching the connecting edge of the acoustic assembly to the acoustic skin using glue, the risk of the glue falling inside the hollow acoustic elements thus degrading the acoustic performance of the acoustic panel is avoided.

[0012] In addition, in the case where it is wished to manufacture an acoustic panel of complex and curved shape, the method of the present invention facilitates the gradual shaping of the acoustic panel to the correct curvature and the maintenance of said desired shape.

[0013] The hollow acoustic elements have a shape that tapers between the base and the apex.

[0014] According to one particular embodiment of the invention, the ultrasonic welding is performed by bringing at least one ultrasonic welding head in contact with the connecting edge of the acoustic assembly or with the part of the acoustic skin to be welded, the ultrasonic welding head transmitting the ultrasonic waves generated by a transducer to the connecting edge of the acoustic assembly or to the part of the acoustic skin to be welded, thus causing a local heating. Thus, the ultrasonic welding head transmits the ultrasonic waves generated by a transducer to the connecting edge of the acoustic assembly or to the part of the acoustic skin to be welded, thus causing a local heating at the contact interface between the connecting edge and the acoustic skin, such that the connecting edge is welded to the acoustic skin.

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

[0016] According to another particular embodiment of the application, a compacting device is used to press the joining edges against the acoustic skin prior to ultrasonic welding.

[0017] Upstream compacting facilitates welding and improves the quality of the weld and the tightness.

[0018] The compacting device can take the form of at least one roller configured to be in rolling contact with the vertices of the plurality of acoustic elements of the acoustic assembly prior to ultrasonic welding.

[0019] The compacting device can take the form of at least one wheel configured to be in rolling contact with the joining edges of the acoustic assembly prior to ultrasonic welding.

[0020] According to another particular embodiment of the application, ultrasonic welding is performed in such a way as to obtain a continuous weld extending from one side to the other of the acoustic assembly.

[0021] Such an uninterrupted weld provides a seal between the acoustic assembly and the acoustic skin, guaranteeing excellent acoustic performance.

[0022] According to another particular embodiment of the application, ultrasonic welding is performed in such a way as to obtain a discontinuous weld extending from one side to the other of the acoustic assembly, the cumulative length of the discontinuous portions of the weld being less than 50% of the total length of the weld.

[0023] A weld with such short interruptions provides reasonable tightness while allowing fluid passage. For example, if the acoustic panel is intended to be positioned in an aircraft, discontinuities allowing fluid passage during operation are desirable.

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

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

[0026] According to another particular embodiment of the application, at least the part of the acoustic skin to be welded to the joining edges of the acoustic assembly is covered with a layer of thermoplastic resin free of fibers.

[0027] Such a pure resin layer can better control ultrasonic welding, ensuring a satisfactory and uniform amount of material. The pure resin layer can also facilitate the transmission of vibrations and ensure their uniform and controlled propagation.

[0028] According to another particular embodiment of the application, the acoustic skin has a plurality of perforations prior to assembly with the acoustic assembly.

[0029] By creating perforations prior to assembly, the risk of damaging the hollow acoustic elements when creating said perforations is eliminated.

[0030] According to another particular embodiment of the application, the method further comprises assembling at least one porous body with one or more acoustic assemblies, the assembly between the porous body and the acoustic assemblies being made in such a way that the apex of the hollow acoustic elements is arranged in a cell of the porous body. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 is a schematic exploded perspective view of an acoustic panel obtained by the method of the application.

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

[0033] Figure 3 is a schematic cross-sectional view showing the contact of the acoustic assembly with the acoustic skin.

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

[0035] Figure 5 is a schematic top view showing the path of the ultrasonic horn of the ultrasonic welding device. DETAILED DESCRIPTION

[0036] Figure 1 and Figure 2 One example of an acoustic panel 100 is shown, the panel comprising in order: an acoustic skin 110, an acoustic assembly 120 comprising a plurality of hollow acoustic elements 121, a porous body 130 and a closing plate 140.

[0037] The function of the acoustic skin 110 is to allow the passage of the sound waves to be attenuated through the interior of the acoustic panel 100. To this end, the acoustic skin 110 comprises a plurality of perforations 111, as shown in Figure 1 and Figure 2 Each perforation 111 of the acoustic skin 110 preferably corresponds to: one cell of the porous body 130 and one hollow acoustic element 121 of the acoustic assembly 120. The thickness of the acoustic skin 110 can be between 1 and 5 mm, for example 2 mm.

[0038] The acoustic skin 110 can be manufactured in a well-known manner by stamping, automatic fiber placement (AFP) or automatic tape laying (ATL). Other methods can also be used to manufacture the acoustic skin 110 (for example manual laying).

[0039] ​The acoustic skin 110 can be made of a thermoplastic material, for example a thermoplastic matrix composite comprising fibers. The fibers can be made of carbon, glass or aramid. The acoustic skin 110 can not comprise fibers. The thermoplastic matrix can be made of, for example, polyaryletherketone (PAEK), polyetherketoneketone (PEKK), polyetherimide (PEI), polyphenylene sulfide (PPS), polyether sulfone (PESU) or polycarbonate (PC).

[0040] To facilitate the ultrasonic welding step, at least the part of the acoustic skin 110 to be welded to the acoustic assembly 120 is covered with a layer of thermoplastic resin free of fibers. Indeed, such a layer of thermoplastic resin ensures a satisfactory and homogeneous amount of material for a better controlled welding.

[0041] The closing plate 140 corresponds to a solid surface for reflecting acoustic waves entering the acoustic panel 100. The closing plate 140 can be a constituent element of the acoustic panel, as shown 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 is not provided with a closing plate, but is directly mounted on the structure of the object. The thickness of the closing plate 140 can be between 1 and 5 millimeters, for example 2 millimeters.

[0042] The closing plate 140 can be manufactured in a well-known manner by stamping, automatic fiber placement (AFP) or automatic tape laying (ATL). Other methods can also be used to manufacture the closing plate 140. For example, the closing plate can be pre-consolidated and then assembled to the porous body by adhesion, or can be formed and consolidated directly on the porous body.

[0043] The closing plate 140 can be made of a composite material comprising fibers, for example a composite material based on carbon fibers, impregnated thermoplastic or thermoset resin. The closing plate 140 can not comprise fibers. The acoustic skin 110 can be made of a thermoplastic material, for example a thermoplastic matrix composite comprising fibers. The fibers can be made of carbon, glass or aramid. The thermoplastic matrix can be made of, for example, polyaryletherketone (PAEK), polyetherketoneketone (PEKK), polyetherimide (PEI), polyphenylene sulfide (PPS), polyether sulfone (PESU) or polycarbonate (PC).

[0044] The porous body 130 comprises a plurality of partitions 131 forming a network of ribs, thereby defining 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 porous body 130. The lower edges 131b of the partitions 131 define a second assembly face 130b of the porous body 130. Thus, the cells 132 extend from the first assembly face 130a to the second assembly face 130b of the porous body 130.

[0045] The height H of the cells 132 of the porous body 130 is chosen to obtain the desired frequency processing, depending on the use of the acoustic panel 100. 130 The height H of the cells 132 of the porous body 130 is chosen to obtain the desired frequency processing, depending on the use of the acoustic panel 100.

[0046] In the example shown in Figure 1 and Figure 2 In the example shown in

[0047] The porous body 130 can be made of a polymer, a composite material or a metallic material, by additive manufacturing or according to conventional means. The porous body 130 can also be made of a thermoplastic material by injection, folding or assembling of tubes, in a well-known manner. The thermoplastic material can be filled with short or long fibers. The porous body 130 can not be filled.

[0048] The acoustic assembly 120 comprises a plurality of hollow acoustic elements 121, each having a shape tapering between a base 121a and an apex 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 (lying on the same plane as the base 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 assembly 120. The first assembly face 120a of the acoustic assembly 120 is intended for contact assembly with the acoustic skin 110. The lower faces 122b of the edges 122 define a second assembly face 120b of the acoustic assembly 120. The second assembly face 120b of the acoustic assembly 120 is intended for contact assembly with the porous body 130. More precisely, the second assembly face 120b of the acoustic assembly 120 is intended for contact assembly with the first assembly face 130a of the porous body 130.

[0049] In the example shown in Figure 1 and Figure 2 In the example shown in Figure 1 Figure 2 In the example shown in

[0050] In the example shown in Figure 1 Figure 2 ​​In the example shown, the base 121a of the hollow acoustic elements 121 has a hexagonal geometry. Of course, it would not go beyond the scope of the application if the base of the hollow acoustic elements had other geometrical shapes, such as a circular, square or rectangular geometry. Figure 1 and Figure 2 In the example shown, the apex 121b of the hollow acoustic elements 121 has a hexagonal geometry. Of course, it would not go beyond the scope of the application if the apex of the hollow acoustic elements had other geometrical shapes, such as a circular, square or rectangular geometry.

[0051] The wall thickness of the hollow acoustic elements 121 can be between 0.25 mm and 2 mm. Preferably, the thickness of the hollow acoustic elements 121 is 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 in particular enables to impart a considerable flexibility to the acoustic assembly 120, which makes it easier to shape and assemble to the acoustic skin 110.

[0052] Preferably, the base 121a of the hollow acoustic elements 121 is comprised within a circle having a diameter between 8 mm and 25 mm. For example, the base 121a of the hollow acoustic elements 121 is comprised within a circle having a diameter of 20 mm. Preferably, the apex 121b of the hollow acoustic elements 121 is comprised within a circle having a diameter between 1 mm and 10 mm. For example, the apex 121b of the hollow acoustic elements 121 is comprised within a circle having a diameter of 5 mm.

[0053] Preferably, the height H 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 of the hollow acoustic elements 121 is 20 mm. 120 120 120 130 .

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

[0055] The acoustic assembly 120 can also be manufactured in a well-known manner by injection compression molding of a thermoplastic material. Injection compression molding consists in injecting the material into a partially open mold. Thus, even if the material solidifies, the passages are less easily clogged. Once the material is distributed throughout the mold, the mold is fully closed by a closing force to restore the correct dimensions. This can result in a thinner wall thickness of the acoustic assembly compared to a conventional injection process.

[0056] ​​​The acoustic component 120 can also be manufactured in a well-known manner by injection molding of a thermoplastic material with tooling temperature control. Injection molding with tooling temperature control includes controlling the temperature of the tooling or mold via a servo control system for the tooling temperature (e.g., using a heat transfer fluid or air).

[0057] 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 molding. The acoustic component 120 may be made, for example, of polyetherimide (PEI) or polyethersulfone (PESU) to facilitate its manufacture and subsequent molding.

[0058] exist Figure 1 and Figure 2 In the example shown, the acoustic panel 100 comprises only one porous body and one acoustic component. Of course, it is not beyond the scope of the invention to include multiple stacked porous bodies in the acoustic panel. Similarly, it is not beyond the scope of the invention to include multiple acoustic components in the acoustic panel. In this configuration, the width of the acoustic component can be between 200 mm and 1000 mm, and its length can also be between 200 mm and 1000 mm. The acoustic panel may also include intermediate acoustic skins defining different stages of the acoustic panel.

[0059] The assembly of acoustic component 120 and acoustic skin 110 includes: a contact step, an optional position holding step, and a welding step.

[0060] During the contact step, the acoustic component 120 contacts the acoustic skin 110, such as Figure 3 As shown. More precisely, the first assembly surface 120a of the acoustic component 120 contacts the acoustic skin 110, that is, the upper surface 122a of the edge 122 is positioned to contact the acoustic skin 110.

[0061] Preferably, the acoustic skin 110 has perforations 111 before being assembled to the acoustic assembly 120. In this configuration, the acoustic assembly 120 contacts the acoustic skin 110 such that the perforations 111 open inside the hollow acoustic element 121 rather than on the connecting edge 122. By forming the perforations 111 in the acoustic skin 110 before assembly, the risk of the hollow acoustic element 121 being damaged by the perforation step after assembly is avoided.

[0062] Contact can be made manually or via robots and grippers. Using robots enables automated assembly. The acoustic skin 110 can be placed on fixed or moving tooling.

[0063] The acoustic assembly 120 is then held in position in contact with the acoustic skin 110, i.e. the upper face 122a of the edge 122 is held in position in contact with the acoustic skin 110. This position holding will last during the welding step to ensure a satisfactory welding. Preferably, the position is held by applying a pressure so that the upper face 122a of the edge 122 is pressed against the acoustic skin 110. This facilitates the welding.

[0064] The position can be held manually or by a robot and a gripper. The use of a robot makes it possible to automate the assembly. The robot used for the position holding is preferably the same as the robot used for the contact. The acoustic skin 110 can be placed on a fixed or mobile tool, preferably on the same tool as the tool used for the contact.

[0065] The ultrasonic welding step is then performed, as shown in Figure 4 and Figure 5 .

[0066] The ultrasonic welding step is preferably performed by one or more ultrasonic horns 61. The welding step can be performed by an ultrasonic welding device 60 comprising at least one ultrasonic horn 61, a transducer 63 and a generator 64.

[0067] The generator 64 is configured to provide energy, preferably electrical energy, to the transducer 63. The transducer 63 is configured to convert the energy provided by the generator 64 into mechanical energy. The transducer 63 can typically be a piezoelectric transducer. The ultrasonic horn 61 is configured to transmit the mechanical motion provided by the transducer 63 to the parts to be welded (here to the acoustic assembly 120). The transducer 63 can generate ultrasonic mechanical waves at a frequency between 16 kHz and 10,000 kHz.

[0068] The ultrasonic welding device 60 can also comprise, in a well-known manner, an amplifier 62 arranged between the ultrasonic horn 61 and the transducer 63. The amplifier 62 is configured to amplify the mechanical motion transmitted by the transducer 63 to the ultrasonic horn 61.

[0069] The ultrasonic horn 61 is configured to be able to move between the hollow acoustic elements 121 in contact with the lower face 122b of the connecting edge 122 of the acoustic assembly 120. The width of the ultrasonic horn 61 thus allows it to pass between the hollow acoustic elements 121.

[0070] The ultrasonic horn 61 can be equipped with a tip 61a at its end. The tip 61a is configured to come into direct contact with the acoustic assembly 120 and to transmit the mechanical motion to said acoustic assembly 120. The tip 61a can be interchangeable. The tip 61a can have various shapes. In Figure 4In the illustrated example, the tip 61a comprises a horn shape, the width of which increases from the end of the ultrasonic horn 61. Of course, it is not beyond the scope of the application if the tip 61a has another shape (e.g. conical, pyramidal, stepped, circular, pointed, spade-shaped, bell-shaped or rectangular). The end of the tip 61a corresponding to the end of the ultrasonic horn 61 can be contained within a circle having a diameter of between 1 mm and 2 mm.

[0071] The welding device 60 can also comprise a parameter setting system (not shown). The parameter setting system is configured to control the energy delivered to the parts to be welded, or to control the welding time, or both.

[0072] Ultrasonic welding is a fast welding method. The ultrasonic welding carried out in the present application can achieve a welding speed of between 0.1 mm / s and 50 mm / s. For example, the ultrasonic horn 61 can weld the acoustic assembly 120 to the acoustic skin 110 by moving at a welding speed of between 0.1 mm / s and 50 mm / s.

[0073] Within the scope of the present application, several ultrasonic welding modes can exist.

[0074] According to a first welding mode, the ultrasonic welding is carried out so as to obtain a continuous weld extending from one side of the acoustic assembly 120 to the other side (i.e. in an uninterrupted manner through the acoustic assembly). A seal is thus obtained between the base 121a of the hollow acoustic element 121 and the acoustic skin 110, which allows excellent acoustic performance.

[0075] In this first welding mode, the ultrasonic horn 61 welds the acoustic assembly 120 to the acoustic skin 110 by following a path extending from one edge of the acoustic assembly 120 to the other edge of said acoustic assembly 120. The path followed by the ultrasonic horn 61 can extend along at least two main directions so as to weld all the connecting edges 122. Thus, a plurality of first paths extend along a first direction, while a plurality of second paths extend along a second direction.

[0076] In Figure 5 In the illustrated schematic example, the ultrasonic horn 61 welds the acoustic assembly 120 along a plurality of first paths T1 along a first direction D1 and a plurality of second paths T2 along a second direction D2. The first direction D1 and the second direction D2 constitute main directions. The first paths T1 followed by the ultrasonic horn 61 extend from a first edge 120e of the acoustic assembly 120 to a second edge 120f of the acoustic assembly 120. The second paths T2 followed by the ultrasonic horn 61 extend from a third edge 120c of the acoustic assembly 120 to a fourth edge 120d of the acoustic assembly 120.

[0077] According to the second welding mode, ultrasonic welding is performed to obtain a discontinuous weld extending from one side of the acoustic component to the other, wherein the cumulative length of the discontinuous portion of the weld is less than 50% (or even less than 20% of the total weld length). Preferably, the length of the discontinuous portion in each weld is less than or equal to 2 mm. Therefore, ultrasonic welding is performed to obtain a weld that passes through the acoustic component but has a short interruption. This achieves a certain seal between the base 121a of the hollow acoustic element 121 and the acoustic skin 110, which allows for good acoustic performance while allowing fluid to escape when the acoustic panel 100 is placed on a running machine or system (e.g., an aircraft).

[0078] This type of weld with interruptions can follow the same path and direction as described in the first welding mode.

[0079] In the context of the method of the present invention, a compaction device can be used to compress the connecting edge 122 against the acoustic skin 110 before the ultrasonic welding head 61 passes through.

[0080] According to a first embodiment of the invention, the compaction device may take the form of one or more rollers configured to roll into contact with the apex 121b of the acoustic element 121 of the acoustic assembly 120 before the ultrasonic welding head 61 passes through. The width of the roller is greater than the diameter of the circle inscribed in the base 121a of the hollow acoustic element 121 of the acoustic assembly 120. Therefore, the roller can be configured to simultaneously completely or partially cover multiple hollow acoustic elements 121. For example, the roller can be configured to simultaneously completely or partially cover two to ten hollow acoustic elements 121. The roller is flexible to avoid damaging the apex 121b of the acoustic element 121. In the case where the acoustic assembly 120 is welded to the acoustic skin 110 to form, for example, a curved shape assembly with hyperbolic curvature, the flexibility of the roller allows it to adapt to the curvature of the acoustic assembly 120. The pressure applied by the roller can be between 1 bar and 5 bar. This pressure can apply satisfactory welding pressure without the risk of damaging or deforming the hollow acoustic element 121.

[0081] according to Figure 5 In the second embodiment shown, the compaction device may take the form of one or more wheels 71 configured to roll into contact with the underside 122b of the connecting edge 122 of the acoustic assembly 120 before the ultrasonic welding head 61 passes through. Therefore, the width of the wheels 71 allows them to pass between the hollow acoustic elements 121 and contact the underside 122b of the connecting edge 122. The pressure applied by the wheels can be between 1 bar and 5 bar. This pressure can apply satisfactory welding pressure without the risk of damaging or deforming the acoustic assembly 120.

[0082] To manufacture the acoustic panel 100, the acoustic assembly 120 is assembled with the porous body 130 such that the upper edge 131a of the partition 131 is in fixed contact with the lower face 122b of the connection edge 122 of the acoustic assembly 120. Thus, the second assembly face 120b of the acoustic assembly 120 is in fixed contact with the first assembly face 130a of the porous body 130. For example, the acoustic assembly 120 can be connected to the porous body 130 by welding or adhesion.

[0083] If the assembled acoustic skin 110 and acoustic assembly 120 have a curved shape, the porous body 130 can already have the appropriate curved shape before assembly, or can be directly shaped in contact with the acoustic assembly 120. The fact that the acoustic assembly 120 has been assembled and connected to the acoustic skin 110 before the assembly of the porous body in this curved configuration facilitates the assembly of the porous body 130 such that the hollow acoustic elements 121 are present in the cells 132 of the porous body 130. If the porous body 130 is assembled to the acoustic assembly 120 by adhesion, the adhesion interface can also be better controlled.

[0084] If the closing plate 140 is present, the closing plate 140 is assembled with the porous body 130 such that the lower edge 131b of the partition 131 is in fixed contact with the closing plate 140. Thus, the second assembly face 130b of the porous body 130 is in fixed contact with the acoustic skin 140. The assembly of the closing plate 140 with the porous body 130 can for example be carried out by welding or adhesion. The closing plate 140 can also be directly formed by automated fiber placement on the porous body 130, the heating tool of the placement head making it possible for the placed strip to be welded to the lower edge 131b of the partition 131.

[0085] The acoustic panel 100 is thus obtained. For example, the acoustic panel 100 can be used for acoustic attenuation in aircraft nacelles or engines, for blade platforms or for aeronautical sleeves. For example, the acoustic panel 100 can be used to cover the internal fixed structure (IFS) of a nacelle, an aircraft fan case, a sliding aeronautical sleeve, an aircraft intake or a portion of aircraft wing. The acoustic panel 100 is particularly suitable for treating low frequencies.

[0086] The expression "between... and..." is to be understood as including the boundary values.

Claims

1. A method for manufacturing an acoustic panel (100), comprising: At least one acoustic component (120) is assembled with an acoustic skin (110), the 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: contacting the acoustic skin (110) with the connecting edges (122) of the acoustic component (120), The method is characterized in that it further includes attaching the connecting edge (122) to the acoustic skin (110) by ultrasonic welding, and a compaction device (71) for pressing the connecting edge (122) against the acoustic skin (110) prior to ultrasonic welding.

2. The manufacturing method according to claim 1, wherein, Ultrasonic welding is performed by contacting at least one ultrasonic welding head (61) with the connecting edge (122) of the acoustic component (120) or the portion of the acoustic skin (110) to be welded, wherein the ultrasonic welding head (61) transmits ultrasonic waves generated by the transducer (63) to the connecting edge (122) of the acoustic component (120) or the portion of the acoustic skin (110) to be welded, thereby causing localized heating.

3. The manufacturing method according to claim 1 or 2, wherein, Ultrasonic welding is performed to obtain a continuous weld extending from one side of the acoustic component (120) to the other side.

4. The manufacturing method according to claim 1 or 2, wherein, Ultrasonic welding is performed to obtain a discontinuous weld extending from one side of the acoustic component (120) to the other side, wherein the cumulative length of the discontinuous portion of the weld is less than 50% of the total weld length.

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

6. The manufacturing method according to any one of claims 1 to 5, wherein, The acoustic skin (110) is made of thermoplastic matrix composite material.

7. The manufacturing method according to any one of claims 1 to 6, wherein, At least the portion of the acoustic skin (110) to be welded to the connection edge (122) of the acoustic assembly (120) is covered with a fiber-free thermoplastic resin layer.

8. The 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. The method according to any one of claims 1 to 8, wherein, The compaction device is formed by at least one roller, which is configured to roll into contact with the apex (121b) of the acoustic element (121) of the acoustic assembly (120).

10. The method according to any one of claims 1 to 8, wherein, The compaction device is formed by at least one wheel (71) configured to roll into contact with the connecting edge (122) of the acoustic component (120).

11. The method according to any one of claims 1 to 10, further comprising: At least one porous body (130) is assembled with one or more of the acoustic components (120), and the assembly between the porous body (130) and the acoustic components (120) is carried out in such a way that the apex (121b) of the hollow acoustic element (121) is arranged in the cell (132) of the porous body (130).

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