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EP-4736157-A1 - MANUFACTURING AN ACOUSTIC PANEL BY ULTRASONIC WELDING

EP4736157A1EP 4736157 A1EP4736157 A1EP 4736157A1EP-4736157-A1

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.

Inventors

  • LANFANT, Nicolas, Pierre
  • ARNAUD, Fabien

Assignees

  • Safran

Dates

Publication Date
20260506
Application Date
20240621

Claims (11)

  1. [Claim 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 fixing 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 the ultrasonic welding.
  2. [Claim 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. [Claim 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. [Claim 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. [Claim 5] A manufacturing method according to any one of claims 1 to 4, wherein the acoustic component (120) is made of thermoplastic material.
  6. [Claim 6] Manufacturing method according to any one of claims 1 to 5, in which the acoustic skin (110) is made of a thermoplastic matrix composite material.
  7. [Claim 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. [Claim 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. [Claim 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. [Claim 10] A 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. [Claim 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 multicellular body(ies) (130) and the acoustic component(s) (120) being carried out such that the vertices (121b) of the hollow acoustic elements (121) are arranged in the cells (132) of the multicellular body(ies) (130).

Description

Description Title of the invention: Manufacture of an acoustic panel by ultrasonic welding Technical Domain [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 as in gas turbines or exhaust thereof. Previous technique [0002] Acoustic attenuation panels typically consist of an acoustic surface plate or skin permeable to the acoustic waves that are to be attenuated and a reflective solid plate or skin called a "closing plate", a multicellular body being arranged between these two skins. The multicellular body is generally constituted by a set of partitions, for example in the shape 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 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 handling low frequencies without resorting to an overly thick multicellular body is to place hollow acoustic elements, for example open cone truncates, in the cells of the multicellular body as described in document FR 3 082 987. [0005] To manufacture such an acoustic panel, it is 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 an alteration of the acoustic performances. In addition, the hollow acoustic elements are made of thermoplastic material, possibly comprising additives to facilitate demolding. However, the bonding of such thermoplastic materials is more complex to implement than the bonding of thermosetting materials. Thus, the bonding of 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 as the hollow acoustic elements are thin and not very thick. Disclosure 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] For this purpose, the invention proposes a method of 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. Furthermore, compared to solutions using glue to fix the connecting edges of the acoustic component to the acoustic skin, the glue is prevented