METHOD FOR MANUFACTURING A STRUCTURE WITH CELLULAR CORES FOR A TURBOJET NACELLE

Abstract

A method for manufacturing an alveolar core structure includes at least one cell including a secondary duct having a first end defining a sound wave inlet, and an opposite second end, the secondary duct comprising a sound wave outlet. The method also includes a fastening step in which adhesive tapes transverse to the longitudinal direction of said first plate are applied on a first longitudinal plate. The secondary duct in the form of a flattened element is fastened, on the first plate, by gluing at its sound wave inlet. A second plate is applied. A step of deploying the first and second plates so as to form the peripheral wall of the cells and so that the flattened element is deployed.

Claims

1. A method for manufacturing an alveolar core structure for an acoustic attenuation panel, the alveolar core structure including a plurality of adjoining acoustic cells which form the alveolar core, each acoustic cell extending along a main axis (A) corresponding to an axis of propagation of a sound wave, from a front end up to a rear end, and being delimited by a peripheral wall defining a primary duct for circulating the sound wave, at least one cell including a secondary duct for circulating the sound wave, the secondary duct comprising a secondary duct wall, having a first end proximal to the front end of the cell, the first end defining a sound wave inlet, and an opposite second end, the secondary duct comprising a sound wave outlet located near the rear end of the cell, the method comprising: a fastening step in which: adhesive tapes parallel to each other and transverse to a longitudinal direction of said first plate are applied, on a first longitudinal plate, so as to form nodal areas, the secondary duct in the form of a flattened element is fastened, on the first plate between two nodal areas, by gluing at the sound wave inlet, and a second plate is applied and fastened by gluing to the nodal areas, and to the flattened element at the sound wave inlet; and a deployment step in which the first and second plates are moved away from one another so as to form the peripheral wall of the cells and so that the flattened element is deployed to form the secondary duct.

2. The method according to claim 1, wherein the fastening step is repeated by alternating positions of the nodal areas, so as to obtain several superimposed layers of flattened elements between first and second plates, before the deployment step.

3. The method according to claim 1, wherein the flattened element is shaped as two flattened secondary ducts, linked by their respective sound wave inlet.

4. The method according to claim 3, further comprising a step of cutting, transversely to the longitudinal direction of the first and second plates, so as to separate the flattened element to form two distinct assemblies, one including a first secondary duct and the other including a second secondary duct.

5. The method according to claim 4, wherein the cutting step is carried out by machining after the deployment step.

6. The method according to claim 4, wherein the cutting step is carried out before the deployment step.

7. The method according to claim 1, wherein the flattened element has one of a flattened conical and a frustoconical shape so that the secondary duct has the one of a conical and a frustoconical shape.

8. The method according to claim 1, wherein the first and second plates have folds intended to delimit edges to obtain polygonal acoustic cells during the deployment step.

9. The method according to claim 8, wherein the flattened element has folds intended to delimit edges to obtain one of a polygonal conical and a frustoconical-shaped secondary duct.

10. The method according to claim 1, wherein a constituent material of the first and second plates is an aluminum alloy.

11. The method according to claim 1, wherein a constituent material of the first and second plates is a composite material.

12. The method according to claim 11, wherein the composite material includes fibers selected from the group consisting of glass fibers and aramid, and the constituent material of the secondary duct is a thermoplastic material.

13. An alveolar core structure obtained according to the method of claim 1, comprising at least one acoustic cell extending along a main axis corresponding to an axis of propagation of a sound wave, from a front end up to a rear end, and being delimited by a peripheral wall defining a primary duct for circulating the sound wave, the cell including a secondary duct for circulating the sound wave, the secondary duct comprising a secondary duct wall, having a first end proximal to the front end of the cell, the first end defining a sound wave inlet, and an opposite second end, the secondary duct comprising a sound wave outlet located near the rear end of the cell.

14. The alveolar core structure according to claim 13, wherein the sound wave outlet of the secondary duct has a diameter smaller than that of the sound wave inlet.

15. The alveolar core structure according to claim 13, wherein the sound wave outlet of a secondary circuit is disposed at a distal end of the secondary duct.

16. The alveolar core structure according to claim 13, wherein the sound wave outlet of a secondary circuit is disposed in the wall of the secondary duct, in its rear half, that is to say proximal to the rear end of the cell.

17. The alveolar core structure according to claim 13, wherein the sound wave outlet of a secondary circuit is circular in shape.

Description

DRAWINGS

[0056] In order that the disclosure may be well understood, there will now be described various forms thereof, given by way of example, reference being made to the accompanying drawings, in which:

[0057] FIG. 1 is a schematic perspective view of a first form of an acoustic cell obtained according to the method of the present disclosure;

[0058] FIG. 2 is a schematic perspective view of a second form of an acoustic cell obtained according to the method of the present disclosure;

[0059] FIG. 3 is a schematic perspective view illustrating a first step of the method according to another form of the present disclosure;

[0060] FIG. 4 is a schematic perspective view illustrating a second step of the method of the present disclosure according to FIG. 3;

[0061] FIG. 5 is a schematic cross-sectional view illustrating an unexpanded block obtained during the fastening step of the method of yet another form of the present disclosure; and

[0062] FIG. 6 is a schematic view illustrating one variant of the method of the present disclosure illustrated in FIG. 3.

[0063] The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.

DETAILED DESCRIPTION

[0064] The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features.

[0065] In the following description and in the claims, the terms “front”, “rear”, “horizontal”, “vertical”, “upper”, “lower”, etc. will be used in a non-limiting manner and with reference to the drawings in order to facilitate the description.

[0066] FIGS. 1 and 2 represent acoustic cells 10, 10′ of an alveolar core structure for an acoustic attenuation panel, according to variations of the present disclosure. The acoustic cells 10, 10′ extend along a main axis A. The main axis A corresponds to an axis of propagation of a sound wave, so that the alveolar core structure allows attenuating the sound wave. More specifically, the acoustic cells 10, 10′ include a so-called front end 12, and a so-called rear end 14 opposite to the front end 12. The acoustic cells 10, 10′ are delimited by a peripheral wall 16 defining a duct 18, called a primary duct. The primary duct 18 is a duct for circulating the sound wave.

[0067] The acoustic cells can have a deployable polygonal shape, for example a hexagonal shape.

[0068] The peripheral wall 16 can be flat. It can be made of an aluminum alloy or a composite material such as a phenolic, epoxy, bismaleideimide (BMI) or polyimide matrix material and including fibers such as glass fibers, aramid fibers such as those registered under the trademark Nomex® or Kevlar®, or of a composite material of the family of the so-called ceramic materials, based on carbon fibers or SiC or aluminized oxides, and having a ceramic matrix such as geopolymers, Sic or aluminized oxides.

[0069] In a variant that is not shown, the acoustic cells have corrugated peripheral walls.

[0070] As illustrated in FIG. 1, the acoustic cell 10 has a secondary duct 20 comprising a frustoconical-shaped secondary duct wall 22. In addition, the secondary duct 20 may have a polygonal shape.

[0071] Alternatively, as illustrated in FIG. 2, the acoustic cell 10′ has a secondary duct 20′ comprising an ogive-shaped secondary duct wall 22′.

[0072] In variants that are not shown, the duct wall has other shapes such as conical or frustoconical or semi-circular shapes.

[0073] The secondary ducts 20, 20′ comprise a first end 24 proximal to the front end 12 of the acoustic cell, and an opposite second end 24′. The first end 24 defines an opening corresponding to a sound wave inlet. Further, the secondary ducts comprise another opening 26 corresponding to a sound wave outlet.

[0074] In the form shown in FIG. 1, the sound wave outlet 26 is disposed at the second end 24′ of the secondary duct 20.

[0075] In the form shown in FIG. 2, the sound wave outlet 26 is disposed in the wall 22′ of the secondary duct 20′, near the second end 24′.

[0076] The sound wave inlet 24 is located at the front end 12 of the acoustic cell 10, 10′, while the sound wave outlet 26 is located near the rear end 14 of the acoustic cell 10, 10′. The sound wave outlet 26 may have a diameter smaller than that of the sound wave inlet 24. It can be circular in shape.

[0077] The cells 10, 10′ can have a maximum dimension D in the range of 20 mm.

[0078] The constituent material of the secondary ducts 20, 20′ can be an organic material, in one form selected from the groups of thermoplastics, such as, for example, PEI PEEK, PI, Polyester, PA.

[0079] FIGS. 3 to 5 illustrate a method for manufacturing an alveolar core structure for a sound attenuation panel, according to one form of the present disclosure, comprising acoustic cells as previously described.

[0080] This method comprises a so-called fastening step in which a first longitudinal plate 30 is provided, on which a plurality of adhesive tapes 32 parallel to each other and transverse to the longitudinal direction of the first plate 30 are applied.

[0081] During this fastening step, a flattened element 34 shaped as a secondary duct 20, in a flattened form, of an acoustic cell 10 is also provided.

[0082] As illustrated in FIGS. 3 to 5, two elements 34 are provided so as to form two acoustic cells. However, a multitude of elements 34 can be provided, so as to form a multitude of acoustic cells.

[0083] The element 34 comprises a wall corresponding to the wall 22 of the secondary duct, a so-called front opening corresponding to the sound wave inlet 24 and a so-called rear opening corresponding to the sound wave outlet 26.

[0084] The element 34 can be fastened by gluing on the first plate 30 between two adhesive tapes 32. More particularly, the element 34 can be fastened by gluing on the first plate 30, at its sound wave inlet 24. The sound wave outlet 26 of the element 34 is disposed in a non-glued portion of the element 34.

[0085] In this form of the present disclosure, the elements 34 are fastened by gluing between two adhesive tapes so as to allow forming two adjoining acoustic cells.

[0086] Finally, during this fastening step, a second plate 36 is applied on the first plate 30, so as to sandwich the element 34. The second plate 36 can be fastened by gluing on the adhesive tapes 32 and on the element 34 at its sound wave inlet 24. A substantially flat assembly, comprising the first plate 30, the second plate 36 and the element 34, is then obtained.

[0087] The adhesive tapes 32 correspond to nodal areas, that is to say junction areas between the first 30 and second 36 plates.

[0088] Then, the method comprises a deployment step in which the first 30 and second 36 plates are moved away from one another so as to deploy the element 34 to form the secondary duct 20. The first 30 and second 36 plates glued at the nodal areas correspond to the peripheral wall 16 of the acoustic cells 10. Thus, the adhesive tapes 32 allow forming the peripheral walls of the acoustic cells. During the deployment step, the first 30 and second 36 plates are moved away so as to form the primary duct 18 of the acoustic cells.

[0089] Before the deployment step, the fastening step can be reproduced on the second plate 36, so as to obtain a superposition of plates 30, 36, 36′, 36″ (FIG. 5) which sandwich elements 34 corresponding to flattened secondary ducts. From one plate to another, the elements 34 may be disposed in a staggered way. An unexpanded block 38, also called an unexpanded honeycomb block, is obtained.

[0090] The non-glued portion of the element 34 may have a perimeter smaller than the perimeter of the glued portion, called an attachment perimeter. The attachment perimeter can be in the range of 150 mm.

[0091] The adhesive tapes 32 can be any gluing means such as glue films or any other sticky element.

[0092] In one form, the adhesive tapes 32 are organic tapes that are polymerized prior to the deployment step. This polymerization step is called the consolidation step.

[0093] The adhesive tapes 32 can be spaced apart by a distance d of about 50 mm.

[0094] In one form, the spacing distance d between two adhesive tapes is variable along a plate.

[0095] The first 30 and second 36 plates may have folds intended to delimit the edges of the acoustic cells so as to obtain polygonal acoustic cells such as hexagonal cells.

[0096] In addition, the element 34 may have folds intended to delimit edges to form a polygonal secondary duct.

[0097] The constituent material of the first 30 and second 36 plates may be an aluminum alloy, so as to form acoustic cell peripheral walls made of aluminum alloy.

[0098] Alternatively, the constituent material of the first 30 and second 36 plates can be:

[0099] a composite material such as a phenolic, epoxy, bismaleideimide (BMI) or polyimide matrix material and including fibers such as glass fibers, aramid fibers such as those registered under the trademark Nomex® or Kevlar®, or

[0100] a composite material of the family of so-called ceramic materials, based on carbon fibers or SiC or aluminized oxides, and having a ceramic matrix such as geopolymers, Sic or aluminized oxides,

[0101] so as to form acoustic cell peripheral walls in one of these materials.

[0102] The constituent material of the element 34 can be an organic material, in one form selected from the groups of thermoplastics, such as, for example, PEI PEEK, PI, Polyester, PA, so as to form acoustic cell secondary ducts made of an organic material.

[0103] As illustrated in FIG. 6, during the fastening step, an element 34′ shaped as two flattened secondary ducts, linked by their sound wave inlet 24, is provided. As illustrated in FIGS. 3 to 5, this element 34′ can be fastened by gluing on the first plate 30, between two adhesive tapes 32, at the sound wave inlets 24, then a second plate 36 is applied on the first plate 30, so as to sandwich this element 34′.

[0104] In FIG. 6, the method includes a step of cutting along an axis B transverse to the longitudinal direction of the plates, so as to separate the element 34′ to form two distinct assemblies, one of which includes a flattened element corresponding to a secondary duct and the other includes another flattened element corresponding to a secondary duct.

[0105] This cutting step can be carried out before the deployment step.

[0106] Alternatively, this cutting step can be carried out after the deployment step, by machining.

[0107] The description of the disclosure is merely exemplary in nature and, thus, variations that do not depart from the substance of the disclosure are intended to be within the scope of the disclosure. Such variations are not to be regarded as a departure from the spirit and scope of the disclosure.