Method for making a honeycomb core having an open internal conical shape

Abstract

The invention relates to a method for manufacturing a honeycomb core structure (1) for a sound attenuation panel, the structure comprising a first edge (3) and a second edge (5) separated by honeycomb cells (7), the honeycomb cells comprising walls extending from the first and second edges and defining a main duct (11) for circulating the sound waves to be attenuated. According to the invention, the method is notable in that it comprises the following steps aimed at: - covering the first edge or the second edge of the honeycomb core structure with a partition wall (13); - deforming the partition wall so as to define at least one secondary duct (15) for circulating the sound waves to be attenuated, the secondary duct extending at least partially inside the main duct; - forming an opening (17) in the partition wall so as to enable communication between the main duct and the secondary duct.

Description

Technical Field

[0001] The invention relates to a method for manufacturing a honeycomb core structure for a sound attenuation panel. The invention also relates to a honeycomb core structure for a sound attenuation panel obtained by the manufacturing method according to the invention, and a sound attenuation panel according to the invention comprising the honeycomb core structure. Background Art

[0002] Aircraft turbojet engines generate significant noise pollution. There is a strong desire to reduce this pollution, and this desire is increasing as the turbojet engines used become more and more powerful. The design of the nacelle surrounding the turbojet engine contributes to a great extent to reducing this noise pollution.

[0003] In order to further improve the acoustic performance of the aircraft, the nacelle is equipped with sound attenuation panels, the purpose of which is to attenuate the noise generated by the circulation of the airflow through the turbojet engine and the vibrations of the nacelle structure.

[0004] Sound attenuation panels are known sandwich structures that absorb these noises. These panels generally comprise a cellular core structure, which may be in the form of a honeycomb layer comprising honeycomb cells (a structure generally referred to as a "honeycomb").

[0005] The honeycomb core structure is usually coated on one of its faces with an air-impermeable skin, called a “solid” skin, and on the other face with a so-called “acoustic” skin penetrated by a plurality of acoustic holes defining an acoustic pattern.

[0006] Such acoustic attenuation panels constitute acoustic resonators suitable for "catching" noise and thus attenuating acoustic emissions towards the outside of the nacelle. These acoustic attenuation panels are mounted in areas of the nacelle, which may be, for example, the air inlet of the nacelle, the internal fixed structure (IFS) of the nacelle, the core surrounding the turbojet engine, the blocking flaps of the cascade thrust reverser devices.

[0007] In order to acoustically attenuate low frequencies, it is known to form sound attenuating panels whose honeycomb core structure comprises one or more superimposed honeycomb layers separated by membranes, with an increased overall height.

[0008] However, increasing the thickness of the acoustic panel increases its weight, which is contrary to the solution of the general technical problem specific to the aeronautical industry, which is to reduce the mass of the aircraft.

[0009] Another known construction for acoustically attenuating low frequencies consists in forming a cone open at its bottom in each cell of a honeycomb core structure.

[0010] By providing such cones, we increase the length of the path that sound waves entering the acoustic panel travel compared to the distance they would travel without these cones, without increasing the thickness of the panel, as would be the case with a two-stage honeycomb core structure separated by a membrane.

[0011] This type of construction is described, for example, in documents US 2015 / 0041247 A1 and US 2015 / 0041248 A1. These cones are placed in the honeycomb core structure in particular by welding. Therefore, the production of these cones inside the honeycomb cells is extremely complex and the time required to produce the honeycomb core structure is very long. In addition, the honeycomb core structure produced by this type of prior art method is very expensive. Summary of the invention

[0012] The present invention aims to overcome the above-mentioned drawbacks and, for this purpose, relates to a method for manufacturing a honeycomb core structure for a sound attenuation panel, said honeycomb core structure comprising a first edge and a second edge separated by a plurality of honeycomb cells, at least one of said honeycomb cells comprising a plurality of walls extending from said first edge to said second edge and defining a main duct for circulating the sound waves to be attenuated, said method being notable in that it comprises the following steps aimed at:

[0013] - at least partially covering one of the first edge or the second edge of the alveolar core structure with a partition wall;

[0014] - deforming said partition wall so as to define at least one secondary duct for circulating said sound waves to be attenuated, said secondary duct extending at least partially inside said main duct;

[0015] - At least one opening is formed in the partition wall to enable communication between the primary duct and the secondary duct.

[0016] Thus, by using deformed partition walls to define at least one secondary duct for circulating the sound waves to be attenuated and extending at least partially inside the primary duct, it is possible to form as many secondary circulation ducts as the honeycomb structure has primary circulation ducts.

[0017] Compared to the prior art solution of providing secondary pipes that are manufactured independently of each other, the complexity and cost of manufacturing the secondary circulation pipes are significantly reduced.

[0018] It should be understood that during the step of at least partially covering one of the first edge or the second edge of the honeycomb core structure with a partition wall, a plurality of honeycomb cells are covered by the partition wall.

[0019] For example, all honeycomb cells of the honeycomb core structure are covered by partition walls.

[0020] It should be understood that in a step, the partition wall is deformed to define at least one secondary duct for circulating the sound waves to be attenuated, and the secondary duct extends at least partially within the main duct. This step is followed by a step in which one of the first edge or the second edge of the honeycomb core structure is at least partially covered by the partition wall.

[0021] Optional features of the manufacturing method according to the invention:

[0022] - said partition wall comprises a deformable and expandable membrane and said manufacturing method comprises, after the step aimed at deforming said partition wall, an additional step aimed at consolidating said partition wall in its deformed position;

[0023] - alternatively, the membrane of the partition wall is reinforced by a deformable and expandable textile structure;

[0024] - before, after or simultaneously with the step aimed at deforming said partition wall, forming an opening in said partition wall;

[0025] - the step aimed at deforming the partition wall is carried out by mechanically deforming the partition wall by means of mechanical deformation means comprising at least one deformation member designed to exert a pressure or tension force on one of the faces of the partition wall;

[0026] - forming said opening in said partition wall while carrying out a step aimed at deforming said partition wall, and said opening is formed by a punch mounted on said deforming member of said mechanical deformation means;

[0027] - alternatively, the step aimed at deforming said partition wall is carried out by applying a pressure difference on either side of said partition wall;

[0028] According to a common arrangement, the partition wall has a gabled, conical or frustoconical shape in its deformed position.

[0029] The invention also relates to a honeycomb core structure for a sound attenuation panel obtained from the manufacturing method according to the invention, notably with a deformed partition wall resting on one of the first edge or the second edge of the honeycomb core structure.

[0030] The invention also relates to a sound attenuation panel comprising an acoustic skin perforated with a plurality of acoustic holes defining an acoustic pattern, a solid skin and a honeycomb core structure according to the invention arranged between the acoustic skin and the solid skin. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Other features and advantages of the present invention will become apparent upon reading the following detailed description, for the understanding of which reference should be made to the accompanying drawings, in which:

[0032] Figure 1 A honeycomb structure according to the invention is shown during manufacture.

[0033] Figure 2 A honeycomb structure obtained by the production method according to the present invention is shown.

[0034] Figure 3 The sound attenuation panel according to the invention is shown in an exploded view.

[0035] Figure 4 A partial longitudinal section is shown Figure 3 Acoustic panels.

[0036] Figure 5 A first embodiment of the manufacturing method according to the present invention is shown.

[0037] Figure 6 A second embodiment of the manufacturing method according to the present invention is shown.

[0038] Figure 7 A first variant of the first embodiment of the step aimed at deforming the partition wall is shown.

[0039] Figure 8 A second variant of the first embodiment of the step aimed at deforming the partition wall is shown.

[0040] Fig. 9 A first variant of the step aimed at forming the opening in the partition wall is shown.

[0041] Fig.10 A second variant of the step aimed at forming the opening in the partition wall is shown.

[0042] Fig.11 The installation of a partition wall in a sound attenuating panel according to the invention is shown according to a first configuration.

[0043] Fig.12 The installation of a partition wall in a sound attenuating panel according to the invention is shown according to a second configuration.

[0044] Fig.13 A first embodiment of a honeycomb unit of a honeycomb core structure according to the present invention is provided.

[0045] Fig.14 A second embodiment of the honeycomb unit of the honeycomb core structure according to the present invention is provided. DETAILED DESCRIPTION

[0046] In all drawings, the same or similar reference numerals denote the same or similar components or groups of components.

[0047] refer to Figure 1 and2 , respectively show a honeycomb core structure 1 during production and its configuration obtained after applying the production method of the invention.

[0048] The honeycomb core structure comprises a first edge 3 and a second edge 5 separated by a plurality of honeycomb cells 7 .

[0049] The honeycomb cells 7 comprise, in a known manner, a plurality of walls 9 extending transversely between a first edge 3 and a second edge 5 of the honeycomb core structure. The walls 9 of the honeycomb cells 7 extend from the first edge 3 to the second edge 5 of the honeycomb core structure 1. The walls 9 define a main duct 11 for circulating the sound waves to be attenuated from a sound source. For example, the sound source emitting the sound waves to be attenuated may consist of a turbojet engine of an aircraft propulsion assembly.

[0050] According to the first step of the manufacturing method of the present invention, Figure 1 In the deployed position shown, the first edge 3 of the alveolar core structure 1 is completely or partially covered by a so-called partition wall 13. Fig.12 ), the partition wall partially or completely does not cover the first edge 3 of the honeycomb core structure, but its second edge 5.

[0051] The partition wall 13 may also be called a "diaphragm" due to its function in the honeycomb structure, as will be seen in the remainder of the description. According to the second step of the manufacturing method of the invention, the partition wall 13 is deformed so as to define a secondary duct 15 (e.g. Figure 2 The secondary duct 15 extends at least partially within the primary duct 11 defined by the walls 9 of the honeycomb cells 7. The secondary duct is thus obtained by the partition walls 13 in the form of diaphragms in the honeycomb cells 7.

[0052] According to the third step of the manufacturing method of the invention, which may be performed before, during or after the step aimed at deforming the partition wall 13, at least one opening 17 is formed in the partition wall 13. A communication between the primary duct 11 and the secondary duct 15 is then established.

[0053] Then, if Figure 2 As shown, with reference to the geometric shape assumed by the partition walls 13 in their deformed position, a so-called "sub-duct" or "cone" or "conical duct" or "apex-shaped" honeycomb structure 1 is obtained.

[0054] Reference Figure 3 The honeycomb core structure 1 thus manufactured is intended to have a plurality of edges, such as Figure 3At the first edge 3 shown in FIG. , it is covered with an acoustically transparent skin 19, which is pierced with a plurality of acoustic holes 21 defining an acoustic pattern, and at its other edge, for example at the second edge 5, it is covered with a solid skin 23, which reflects sound waves. Thus, the assembly formed by the honeycomb structure 1 sandwiched between the acoustic skin 19 and the solid skin 23 forms Figure 3 The sound attenuation panel 25 is shown in exploded view.

[0055] Reference Figure 4 , which shows Figure 3 2 is a partial longitudinal section through a sound attenuation panel 25 which is installed in an environment in which a sound source 29 (eg an aircraft turbojet engine) emits sound waves 27 to be attenuated.

[0056] The sound waves 27 enter the honeycomb unit 7 through the acoustic holes 21 formed in the acoustic skin 19 (arrow 29 ).

[0057] The sound waves pass through the secondary duct 15 defined by the partition wall 13 and then leave the secondary duct 15 through the opening 17 formed in the partition wall 13 (arrow 31 ).

[0058] The sound waves then penetrate into the interior of the main pipe 11 and are reflected first by the solid skin 23 (arrow 33 ) and then by the walls 9 of the honeycomb cells 7 (arrow 35 ).

[0059] The path for the sound wave 27 to propagate is then increased compared to the path for the sound wave to propagate in a sound attenuation panel not including such a secondary duct, without increasing the thickness of the honeycomb core structure, as is the case in some prior art constructions using a separation membrane between two layers of honeycomb core structure.

[0060] By increasing the distance the sound wave travels, the sound intensity of the wave decreases. The attenuated sound wave 27 then exits again through the opening 17 of the secondary duct (arrow 37).

[0061] Due to this honeycomb core structure, the sound attenuation properties are improved, especially at low frequencies.

[0062] Compared with the prior art solution of providing secondary pipes obtained independently of each other within the main pipe, the complexity of manufacturing the secondary circulation pipe is significantly reduced due to the manufacturing method of the present invention, by using a single-piece partition wall, which is deformed to form a secondary circulation pipe within the main circulation pipe defined by the walls of the honeycomb unit.

[0063] Furthermore, the cost of manufacturing this type of "sub-duct" honeycomb core structure is significantly reduced compared to the prior art.

[0064] according to Figure 5 In the first embodiment of the manufacturing method of the invention shown, the partition wall 13 is constituted by a deformable and expandable membrane 39 suitable for being cured.

[0065] According to a preferred embodiment, the membrane 39 consists of an organic material of the thermosetting, thermoplastic or elastomeric type.

[0066] According to a first variant, the film 39 has a high elongation at break, for example between about 10% and about 300%. This is the case, for example, for polyurethane films or elastomers.

[0067] According to a second variant, the film 39 has a low elongation at break, for example in the range of a few percentage points. This is the case, for example, with films obtained from polymerized epoxy or phenolic resins.

[0068] The manufacturing method according to the invention comprises, after the step aimed at deforming the partition wall 13 formed by the membrane 39 , an additional step aimed at consolidating the partition wall in its deformed position.

[0069] In the case of a membrane 39 formed from a thermosetting or elastomeric material, the membrane is not crosslinked until after the deformation and consolidation steps of the partition walls formed from the membrane 39 are complete.

[0070] Thus, the membrane is cross-linked when the dividing wall is in its deformed position, according to which the membrane defines at least one secondary duct extending at least partially inside at least one primary duct.

[0071] In the case of a film 39 obtained from a thermoplastic material, the film is first thermally fluidized to allow its deformation, after it has at least partially covered one of the edges 3, 5 of the alveolar core structure 1. Once the steps aimed at deforming the partition walls formed by the film 39 have been completed, steps aimed at consolidating the partition walls in their deformed position are carried out.

[0072] According to another embodiment of the membrane 39 , the latter consists of an inorganic material, such as a metal or a ceramic material. After completion of the step aimed at deforming the partition wall, no step aimed at consolidating the partition wall 13 is required.

[0073] The step of the manufacturing method of the invention aimed at covering one of the edges of the alveolar core structure with a partition wall defined by the film 39 is accomplished by installing the film 39 alone on one edge of the alveolar core structure 1 .

[0074] Alternatively, this step can be done when the honeycomb core structure is already glued to one of the skins of the sound attenuation panel.

[0075] according to Figure 6In the second embodiment of the manufacturing method of the invention shown, the partition wall 13 is constituted by a deformable and expandable membrane 39 suitable for being cured and consolidated by a likewise deformable and expandable fabric structure 41. For example, the fabric structure is chosen so as to have an elongation capacity comprised between about 100% and about 400% of the static length.

[0076] According to this second embodiment, the membrane 39 forms the basis of a composite material 43 formed from the membrane or basis 39 and the textile structure 41 .

[0077] When the film or matrix 39 is made of a thermoplastic material, the matrix is ​​hot fluidized before covering at least a portion of one of the edges 3, 5 of the honeycomb core structure 1. Once the fluidized matrix 39 impregnates the fabric structure 41, the matrix 39 expands and the composite material 43 defining the partition wall 13 deforms to define at least one secondary duct extending at least partially within the primary duct.

[0078] Alternatively, the matrix 39 is mixed beforehand with the textile structure 41 to form a pre-impregnated composite material 43. The composite material 43 defining the dividing wall 13 is then deformed to define at least one secondary duct extending at least partially within the primary duct.

[0079] When the membrane or matrix 39 is made of a thermosetting or elastomeric material, the matrix is ​​not cross-linked until the textile structure 41 is infiltrated by the matrix.

[0080] The manufacturing method of the invention comprises, after the step aimed at deforming the partition wall 13 , defined here by the composite material 43 , an additional step aimed at consolidating the partition wall in its deformed position.

[0081] Preferably, the fabric structure 41 used for reinforcing membrane 39 has a texture such that its elongation capacity is completed under the effect of the applied deformation. Its amplitude is defined as a function of the size of the honeycomb cells 7 of the honeycomb core structure to be manufactured, so as to form a bell shape in each honeycomb cell.

[0082] Furthermore, the fabric structure 41 is elastic. Its elasticity is obtained, on the one hand, by the elastic textile fibers and, on the other hand, by the type of mesh produced. To this end, the fabric structure has a mesh of continuous fibers connected together by a knitting or crocheting pattern.

[0083] According to another embodiment, the grids are continuous row by row, the rows being connected by grids one by one.

[0084] According to yet another embodiment, the grids are of discontinuous or mesh type and are connected by grid groups.

[0085] The fibers of the textile structure 41 are made of organic material, such as nylon, polyester, polyamide.

[0086] Alternatively, the fibers are made of metal or mineral material.

[0087] The step of the manufacturing method of the invention aimed at covering one edge of the honeycomb core structure by a partition wall defined by a membrane or matrix 39 reinforced by a fabric structure 41 is achieved by mounting the membrane or matrix 39 reinforced by a fabric structure 41 alone on one edge of the honeycomb core structure 1. Alternatively, this step can be done when the honeycomb core structure is already glued to one of the skins of the sound attenuation panel.

[0088] refer to Figure 7 and 8 , which shows a first variant of the step aimed at deforming the partition wall 13 so as to define at least one auxiliary duct 15 for the circulation of the sound waves to be attenuated.

[0089] The step aimed at deforming the partition wall 13 can be achieved by mechanical deformation of the partition wall 13 formed by the membrane 39 or by a membrane or matrix 39 reinforced by a textile structure 41 .

[0090] according to Figure 7 In the first embodiment shown, the mechanical deformation can be obtained by means of a mechanical deformation device 45 comprising a plurality of deformation members 47 designed to exert a pressure on a surface 49 of the partition wall 13 .

[0091] The deformation member 47 is composed of a block having a curved lower surface 51 for giving a desired shape to the partition wall 13 .

[0092] To this end, the deforming member 47 is designed to have a size capable of penetrating into the interior of the honeycomb unit 7 .

[0093] During activation of the mechanical deformation device 45 , the deformation member 47 moves according to the arrow 53 in order to push the partition wall 13 , which is initially arranged flat on the edge 3 of the honeycomb core structure 1 , towards the edge 5 of the honeycomb cell 7 .

[0094] according to Figure 8 In the second embodiment shown, the mechanical deformation can be obtained by a mechanical deformation device 55, which includes a plurality of deformation members 57, each of which is connected to a face 59 of the partition wall 13, which face is located inside the honeycomb core structure 1 when the partition wall 13 is positioned on the honeycomb core structure.

[0095] Activation of the mechanical deformation device 55 causes displacement of the deformation member 57 according to arrow 61 , which then exerts a tensile force on the partition wall 13 , thereby deforming said wall towards the edge 5 of the alveolar core structure 1 , opposite the edge 3 on which said partition wall is initially arranged.

[0096] According to the common arrangement of the first and second embodiments of the mechanical deformation device, the deformation members 47, 57 preferably operate synchronously, which makes it possible to deform the partition walls 13 in the honeycomb cells simultaneously. This makes it possible to deform the partition walls 13 in one single step.

[0097] Alternatively, the deforming members 47, 57 may be operated asynchronously, which makes it possible to deform the partition walls 13 in the cells non-simultaneously. This may be interesting when it is desired that the shape given to the partition walls after deformation varies from one cell to another.

[0098] According to a second variant that is not shown, the step aimed at deforming the partition wall is carried out by applying a pressure difference on either side of said partition wall.

[0099] According to a first embodiment, applying a pressure difference across the dividing wall is achieved by forming two separate divided volumes on either side of the dividing wall, which are adapted to be pressurized.

[0100] A deformable and expandable membrane 39 may be used to partition the volumes defined on either side of the dividing wall in this manner.

[0101] When the membrane 39 is reinforced by the textile structure 41 , the membrane 39 must be selected so as to remain sufficiently adhesive during the deformation step of the method to maintain a waterproof barrier with the textile structure 41 .

[0102] Alternatively, a deformable waterproof membrane applied along the partition wall may be installed in addition to the membrane 39. The waterproof membrane is selected so as not to adhere to the membrane 39. The waterproof membrane is removed at the end of the deformation step.

[0103] According to the second embodiment, by forming a surface 59 ( Figure 8 The pressure difference applied on the partition wall 13 is obtained by a depression on the side of the partition wall 13 (shown in FIG. 1 ). The depression can be obtained by drawing a partial air vacuum, the depression level varying according to the geometrical parameters and the materials used.

[0104] According to a third embodiment, by blowing pressurized fluid onto the face 49 ( Figure 7 A pressure difference is applied on the partition wall 13 to obtain the pressure difference.

[0105] According to a third variant not shown, the step aimed at deforming the partition walls is obtained by a so-called "spin forming" method or by a "centrifugal forming" method, which is a method of rotating the alveolar core structure so as to deform the partition walls by centrifugal forces.

[0106] According to a fourth variant that is not shown, the step aimed at deforming the partition wall is obtained by magnetic or electromagnetic deformation.

[0107] According to a common arrangement applicable to all variants aiming to carry out a step of deforming the partition walls 13 in the honeycomb cells 7 , at least when the membrane 39 of said wall requires consolidation, as is the case when it is made of organic material, deformation of the partition walls is applied until consolidation of said partition walls is obtained.

[0108] Reference Fig. 9 , which shows a first variant of the step aimed at forming the opening 17 in the partition wall 13 so as to enable communication between the primary duct 11 and the secondary duct 15 .

[0109] According to this first variant, the opening is formed in the partition wall 13 simultaneously with the step aimed at deforming the partition wall.

[0110] The opening 17 can be obtained by mounting a punch 63 on the deforming member 47 of the mechanical deforming device 45. Thus, by moving the deforming member 47, the punch 63 forms the opening in the partition wall 13.

[0111] According to an alternative not shown, it is possible to use an external piercing device which can be used regardless of the deformation method implemented and regardless of the embodiment of the partition wall 13 used. To this end, the external piercing device can, for example, include a punch mounted on an automatic arm or consist of a punching device or a laser cutting device.

[0112] The piercing device is also designed so that the openings 17 can be positioned at different locations in the honeycomb cells relative to one another, depending on the geometrical deviations of the honeycomb cells.

[0113] Reference Fig.10 , which shows a second variant of the step aimed at forming the opening 17 in the partition wall 13 so as to enable communication between the primary and secondary ducts.

[0114] According to this second variant, an opening is made in the partition wall 13 before the step aimed at deforming said wall.

[0115] This variant is applicable regardless of the deformation method implemented and regardless of the embodiment adopted of the partition wall 13 .

[0116] For example, when the partition wall 13 comprises a membrane or a matrix reinforced by a fabric structure, the fabric structure is connected to provide the opening 17 which is not coated with the membrane or the matrix.

[0117] Furthermore, the meshes of the fabric structure may be organized to form openings 17 in the partition wall 13 by extending the connecting meshes therebetween.

[0118] The position of the openings 17 in the partition walls can be chosen so that the position of the openings in the cells can vary from one cell to another depending on geometrical deviations of the cells.

[0119] According to a third variant embodiment (not shown) of the step aimed at forming an opening in the partition wall to enable communication between the primary and secondary ducts, the opening is formed in the partition wall after the step aimed at deforming said partition wall.

[0120] The opening can be obtained by using external piercing means which can be used regardless of the deformation method implemented and regardless of the remaining embodiment of the partition wall.

[0121] For this purpose, the external piercing device can, for example, comprise a punch mounted on a robotic arm or consist of a punching device or a laser cutting device.

[0122] The piercing device is also designed to allow the openings to be positioned at different locations between the honeycomb cells depending on the geometric deviations of the honeycomb cells.

[0123] According to a common arrangement applicable to all variants, the variants aim to carry out a step aiming at forming an opening in the partition wall to enable communication between the primary duct and the secondary duct, the opening being formed at the top of the deformed partition wall to form a top opening. When the deformed partition wall adopts a conical shape in the honeycomb cell, after the opening has been formed, a truncated conical partition wall is obtained in the honeycomb cell. Instead of or in addition to the top opening, the opening can also be formed at the side wall of the partition wall. Regardless of the position of the opening, the latter defines an acoustic neck allowing the passage of sound waves between the primary duct and the secondary duct.

[0124] refer to Fig.11 and 12 , which provide two examples of illustration of partition walls 13 installed in a sound attenuation panel 25 comprising a honeycomb core structure 1 obtained according to the manufacturing method of the invention.

[0125] like Fig.11 As shown, the partition wall 13 rests on the first edge 3 of the honeycomb core structure 1, on which the acoustic skin 19 is mounted. Adhesion is obtained due to the diffusion of the film adhered to the foil of the honeycomb core structure. The partition wall 13 is anchored in some way at the edge 3, that is, on one side of the acoustic skin 19.

[0126] according to Fig.12 In the variant shown in , the partition wall 13 rests on the second edge 5 of the honeycomb core structure 1, on which the solid skin 23 is mounted. Due to the spreading of the film adhered to the foil of the honeycomb core structure, adhesion is also obtained and the partition wall 13 is anchored in some way at the edge 5, that is to say on one side of the solid skin 23.

[0127] refer to Fig.13 and 14, two examples of the geometric shapes of the honeycomb cells 7 of the honeycomb core structure 1 obtained according to the manufacturing method of the present invention are provided. As non-limiting examples, the honeycomb cells can be of Fig.13 The hexagon shown or Fig.14 Of course, the honeycomb cells may have polygonal, circular, elliptical shapes other than those shown.

[0128] The sound attenuation panel obtained by installing a solid skin and an acoustic skin on either side of a honeycomb core structure can be particularly but not limited to equipping an aircraft, in particular a propulsion assembly of an aircraft, more particularly a nacelle of an aircraft turbojet engine, and even more particularly can be an air inlet of the nacelle, an internal fixed structure of the nacelle, an area of ​​the nacelle of a blocking flap of a cascade thrust reverser device.

[0129] It goes without saying that the invention is not limited to the embodiments of the manufacturing method described above merely by way of illustrative example, but rather comprises all variants and combinations thereof relating to technical equivalents of the device falling within the scope of the invention.

Claims

1. A method for manufacturing a honeycomb core structure for a sound attenuation panel, the honeycomb core structure comprising a first edge and a second edge separated by a plurality of honeycomb cells, each of the honeycomb cells comprising a plurality of walls extending between the first edge (3) and the second edge (5) and defining a main duct for circulating sound waves to be attenuated, wherein: The method comprises: - at least partially covering the first edge of the honeycomb core structure with a partition wall; - deforming the partition wall from the first edge so as to form with the partition wall at least two secondary ducts for circulating the sound waves to be attenuated, each secondary duct extending from the first edge and at least partially inside one of the main ducts; - forming openings in the partition wall to provide communication between each secondary conduit and the primary conduit and the secondary conduit in which the secondary conduit is formed.

2. The manufacturing method according to claim 1, wherein: The partition wall comprises a deformable and expandable membrane, and wherein the manufacturing method further comprises, after deforming the partition wall, the step of consolidating the partition wall in its deformed position.

3. The manufacturing method according to claim 2, wherein: The membrane of the partition wall is reinforced by a deformable and expandable textile structure.

4. The manufacturing method according to any one of claims 1 to 3, wherein: The opening is formed in the partition wall before, after or simultaneously with deforming the partition wall.

5. The manufacturing method according to any one of claims 1 to 3, wherein: Deforming the partition wall is obtained by mechanically deforming the partition wall by means of mechanical deformation means comprising at least one deformation member configured to exert a pressure or tension on one of the faces of the partition wall.

6. The manufacturing method according to claim 5, wherein: The opening is formed in the partition wall while deforming the partition wall, and the opening is formed by a punch mounted on the deformation member of the mechanical deformation device.

7. The manufacturing method according to any one of claims 1 to 3, wherein: Deforming the partition wall is obtained by applying a pressure difference on either side of the partition wall.

8. The manufacturing method according to any one of claims 1 to 3, wherein: Each secondary duct formed in the partition wall has a pointed arch, conical or frustoconical shape in its deformed position.

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