EP4169013A1 - Acoustic panel and associated manufacturing method - Google Patents

Acoustic panel and associated manufacturing method

Info

Publication number
EP4169013A1
EP4169013A1 EP21742162.7A EP21742162A EP4169013A1 EP 4169013 A1 EP4169013 A1 EP 4169013A1 EP 21742162 A EP21742162 A EP 21742162A EP 4169013 A1 EP4169013 A1 EP 4169013A1
Authority
EP
European Patent Office
Prior art keywords
acoustic panel
cavities
orifice
cavity
structures
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP21742162.7A
Other languages
German (de)
French (fr)
Inventor
Daniel Therriault
Filippo Iervolino
Juliette Pierre
Nicola Piccirelli
Annie ROSS
Josué COSTA BAPTISTA
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Safran SA
Original Assignee
Safran SA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Safran SA filed Critical Safran SA
Publication of EP4169013A1 publication Critical patent/EP4169013A1/en
Pending legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/16—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/172—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using resonance effects
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B1/00—Layered products having a non-planar shape
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/06—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material
    • B32B27/08—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/18—Layered products comprising a layer of synthetic resin characterised by the use of special additives
    • B32B27/20—Layered products comprising a layer of synthetic resin characterised by the use of special additives using fillers, pigments, thixotroping agents
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/34—Layered products comprising a layer of synthetic resin comprising polyamides
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B3/00—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar shape; Layered products comprising a layer having particular features of form
    • B32B3/10—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar shape; Layered products comprising a layer having particular features of form characterised by a discontinuous layer, i.e. formed of separate pieces of material
    • B32B3/12—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar shape; Layered products comprising a layer having particular features of form characterised by a discontinuous layer, i.e. formed of separate pieces of material characterised by a layer of regularly- arranged cells, e.g. a honeycomb structure
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B3/00—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar shape; Layered products comprising a layer having particular features of form
    • B32B3/10—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar shape; Layered products comprising a layer having particular features of form characterised by a discontinuous layer, i.e. formed of separate pieces of material
    • B32B3/18—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar shape; Layered products comprising a layer having particular features of form characterised by a discontinuous layer, i.e. formed of separate pieces of material characterised by an internal layer formed of separate pieces of material which are juxtaposed side-by-side
    • B32B3/20—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar shape; Layered products comprising a layer having particular features of form characterised by a discontinuous layer, i.e. formed of separate pieces of material characterised by an internal layer formed of separate pieces of material which are juxtaposed side-by-side of hollow pieces, e.g. tubes; of pieces with channels or cavities
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B3/00—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar shape; Layered products comprising a layer having particular features of form
    • B32B3/26—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar shape; Layered products comprising a layer having particular features of form characterised by a particular shape of the outline of the cross-section of a continuous layer; characterised by a layer with cavities or internal voids ; characterised by an apertured layer
    • B32B3/266—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar shape; Layered products comprising a layer having particular features of form characterised by a particular shape of the outline of the cross-section of a continuous layer; characterised by a layer with cavities or internal voids ; characterised by an apertured layer characterised by an apertured layer, the apertures going through the whole thickness of the layer, e.g. expanded metal, perforated layer, slit layer regular cells B32B3/12
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/16—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/162—Selection of materials
    • G10K11/168—Plural layers of different materials, e.g. sandwiches
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C64/00—Additive manufacturing, i.e. manufacturing of three-dimensional [3D] objects by additive deposition, additive agglomeration or additive layering, e.g. by 3D printing, stereolithography or selective laser sintering
    • B29C64/10—Processes of additive manufacturing
    • B29C64/106—Processes of additive manufacturing using only liquids or viscous materials, e.g. depositing a continuous bead of viscous material
    • B29C64/118—Processes of additive manufacturing using only liquids or viscous materials, e.g. depositing a continuous bead of viscous material using filamentary material being melted, e.g. fused deposition modelling [FDM]
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2250/00—Layers arrangement
    • B32B2250/03—3 layers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2250/00—Layers arrangement
    • B32B2250/40—Symmetrical or sandwich layers, e.g. ABA, ABCBA, ABCCBA
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2262/00—Composition or structural features of fibres which form a fibrous or filamentary layer or are present as additives
    • B32B2262/10—Inorganic fibres
    • B32B2262/106—Carbon fibres, e.g. graphite fibres
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/10—Properties of the layers or laminate having particular acoustical properties
    • B32B2307/102—Insulating
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2605/00—Vehicles
    • B32B2605/18—Aircraft
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2607/00—Walls, panels
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B33—ADDITIVE MANUFACTURING TECHNOLOGY
    • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
    • B33Y10/00—Processes of additive manufacturing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B33—ADDITIVE MANUFACTURING TECHNOLOGY
    • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
    • B33Y80/00—Products made by additive manufacturing

Definitions

  • TITLE Acoustic panel and associated manufacturing process
  • the present invention relates, in general, to acoustic attenuation and, more particularly, to devices intended for acoustic attenuation, in particular in the aerospace field.
  • the invention relates to an acoustic panel, in particular an acoustic panel for a propulsion unit.
  • the invention also relates to a method of manufacturing such an acoustic panel.
  • State of the art
  • One of the known solutions allowing this reduction consists in the use of acoustic panels, for example on the internal surface of the fan casing of a turbomachine, and whose sound dissipation mechanism is based on the Helmholtz resonance principle.
  • a Helmholtz (HR) resonator consists of a cavity connected to the external environment by a neck. The sound can then enter the resonator through the neck before being dissipated into the cavity.
  • the resonator attenuates the sound at the natural frequency of the resonance chamber by following the following equation: where D n is the opening diameter of the neck; L n is the length of the neck; V c the volume of the cavity; f r is the resonant frequency of the resonator; and v is the speed of sound in air.
  • an existing acoustic panel called a "sandwich panel”, and applying this principle, comprises two substantially parallel skins between which are located and extend cavities forming Helmholtz resonators and for example organized in a honeycomb (hexagonal section ). One of the skins is pierced with orifices opening into the cavities and forming the necks of the resonators.
  • the resonator structures of known acoustic panels can only achieve absorption at a given absorption frequency, and stacking of different panels is necessary for absorption at different frequencies. Disclosure of the invention
  • An acoustic panel comprising two substantially parallel skins between which are arranged cavities forming Helmholtz resonators, one of said skins being pierced with orifices each opening into one of said cavities and forming a neck of the resonators.
  • one or more of said cavities are formed by a hollow structure in the form of a right prism with a triangular base.
  • the acoustic panel can comprise one or more sets of structures in the form of a right prism with a triangular base delimited by side walls and each comprising one or more of said cavities.
  • one or more assemblies comprise at least four structures in the form of a right prism with a triangular base each and a central cavity formed between the structures formed by a right prism with a triangular base.
  • said skin pierced with orifices may comprise a first orifice and a second orifice opening respectively into a first cavity and into a second cavity among the four cavities formed by a structure in the form of a right prism with a triangular base and a third orifice opening into the central cavity.
  • said skin pierced with orifices comprises a fourth orifice and a fifth orifice opening respectively into a third cavity and a fourth cavity among the four cavities formed by a structure in the form of a right prism with a triangular base.
  • the acoustic panel has two or more different orifice diameters.
  • the structures formed by a right triangular prism are connected to one of said skins by one of their ridges, the interface between the ridge and the skin possibly comprising an enlarged portion.
  • the acoustic panel forms a monolithic structure.
  • the invention also relates to a method of manufacturing an acoustic panel, the method comprising a step of manufacturing by additive manufacturing of an acoustic panel as described above.
  • the step of manufacturing by additive manufacturing is carried out by the technique of deposition of molten filament known as "Fused Filament Fabrication, FFF".
  • FFF Fusion Fabrication
  • FIG 1 illustrates an acoustic panel according to a first embodiment according to the invention, formed by a plurality of sets of cavities in the resonance core and of a pierced skin comprising three orifices per set of cavities.
  • FIG 2 is a perspective view of one set of cavities of the plurality of set of resonant heart cavities of the acoustic panel according to the first embodiment illustrated in Figure 1.
  • FIG 3 is a bottom view of the resonant heart cavity assembly shown in Figure 2.
  • FIG 4 illustrates an acoustic panel according to the first embodiment, in which the cavities of a set of cavities are arranged in an alternative configuration, head to tail.
  • FIG 5 is a graph representing the evolution of the absorption coefficient as a function of the frequency associated with an acoustic panel according to the first embodiment illustrated in Figure 4.
  • FIG 6 illustrates an acoustic panel according to a second embodiment according to the invention, formed by a plurality of sets of cavities in the resonant heart and a pierced skin comprising five orifices per set of cavities.
  • FIG 7 is a graph representing the evolution of the absorption coefficient as a function of the frequency associated with an acoustic panel according to the second embodiment illustrated in Figure 6.
  • FIG. 1 illustrates an acoustic panel 1 for a turbomachine, according to the invention.
  • the acoustic panel 1 is a so-called “sandwich panel” panel. It comprises first and second substantially parallel skins 2 and 3 between which are arranged cavities forming Helmholtz resonators.
  • One of said skins in this example the first skin 2, is pierced with orifices each opening into one of said cavities and forming a neck of the resonators.
  • one or more of said cavities are formed by a hollow structure 4 in the form of a right prism with a triangular base.
  • the structure 4 in the form of a right prism with a triangular base comprises two opposing triangular bases 4a and 4b and two opposite rectangular faces 4c and 4d extending from a common square face 4e.
  • the junction of the two bases 4a and 4b and the two faces 4c and 4d form an edge 5 disposed opposite to the square face 4e.
  • the structure 4 is hollow and thus contains a cavity.
  • All the cavities are preferably formed by structures 4 in the form of a right prism with a triangular base, forming a honeycomb configuration between the two skins 2 and 3.
  • the cavities of the various structures 4 in the form of a right prism with a triangular base are independent of each other and do not communicate.
  • the structures 4 forming the cavities are delimited in several sets or cells by side walls 6.
  • the acoustic panel is thus formed by a plurality of sets of structures 4 in the form of a right prism with a triangular base.
  • each set comprises four structures 4 in the form of a right prism with a triangular base.
  • a perspective view and a bottom view of an assembly are shown in Figures 2 and 3.
  • the four structures 4 shown are arranged at 90 ° relative to each other, relative to an axis passing through the two skins 2 and 3 and perpendicular to the two skins 2 and 3. This arrangement advantageously makes it possible to optimize the space.
  • each edge 5 is arranged opposite the second skin 3.
  • Each assembly also comprises a central cavity 7 formed between the structures 4 formed by a right prism with a triangular base.
  • the central cavity 7 corresponds to the free space within an assembly delimited by the side walls 6, between the structures 4.
  • the skin pierced with orifices which here corresponds to the first skin 2 can include three orifices within the same assembly.
  • a first orifice 8a and a second orifice 8b open out respectively into a first cavity and into a second cavity among the four cavities formed by a structure in right prism shape with triangular base, preferably at the level of the 4th square faces.
  • a third orifice 9 opens into the central cavity 7.
  • the first and second orifices 8a and 8b are, in this example, of different diameters.
  • the diameter of the third orifice 9 is greater than the diameters of the first and second orifices 8a and 8b.
  • first and second orifices 8a and 8b can be arranged so that they open into two of the four structures 4 formed by a right triangular prism, arranged diagonally within the same set of structures 4.
  • two of the four structures 4 formed by a right triangular prism are not used as resonance cavity.
  • the structures 4 formed by a right triangular prism are connected to one of said skins 2 and 3, in this example the second skin 3, by the edge 5.
  • the interface between the edge 5 and the skin comprises an enlarged portion or border reinforcing the mechanical stability of the acoustic panel via the reinforcement of the connection between the structures 4 and the second skin.
  • the four cavities of structures 4 in the form of a right prism with a triangular base thus each form a Helmholtz resonator.
  • the structures 4 in the form of a right prism with a triangular base can be arranged in a head-to-tail configuration in order to optimize the space within the acoustic panel.
  • the graph of FIG. 5 represents the evolution of the absorption coefficient as a function of the frequency, in Hz, measured on an acoustic panel of configuration with three orifices, as illustrated in FIG. 4, the structures arranged head to tail.
  • the thickness of the first pierced skin, and therefore of the neck associated with the orifices 8a, 8b and 9 has been chosen equal to 4mm and the diameter of the first, second and third orifices 8a, 8b and 9 is respectively of 2, 2.5 and 3 mm.
  • three well defined absorption peaks are observable in the figure. In this configuration, the peaks are observable around 500 Hz, 1100 Hz and 1400 Hz.
  • the resonators formed by the central cavity 7, of greater volume than the cavities of the structures 4, generate the low-frequency peak around 500 Hz, while the resonators formed by the two structures 4 in the form of a right prism with a triangular base into which open the orifices 8a and 8b generate the two peaks at high frequencies, around 1100 and 1400 Hz.
  • the use of the two types of cavities is particularly advantageous and makes it possible to obtain a plurality of peaks over a wide range of frequencies between 500 and 1500Hz.
  • FIG. 6 illustrates a second embodiment of acoustic panel 10 in which the pierced skin comprises five orifices.
  • the first skin 2 comprises a first orifice 8a and a second orifice 8b opening respectively into a first cavity and into a second cavity among the four cavities formed by a structure 4 in the form of right triangular prism, preferably at the level of the square faces 4th.
  • the first skin 2 comprises a fourth orifice l ia and a fifth orifice 11b opening respectively into a third cavity and a fourth cavity among the four cavities formed by a structure 4 in the form of a right prism with a triangular base.
  • the different orifices 8a, 8b, 9, 11a and 11b have four or five different diameters.
  • the graph of FIG. 7 represents the evolution of the absorption coefficient as a function of the frequency, in Hz, measured on an acoustic panel of configuration with five orifices, as illustrated in FIG. 6.
  • the thickness of the first pierced skin, and therefore of the neck associated with the orifices 8a, 8b and 9 has been chosen equal to 3mm and the diameter of the first, second, third, fourth and fifth orifices 8a, 8b and 9 are respectively 2 , 2.5, 3.5, 3 and 3 mm.
  • Five well-defined absorption peaks can be seen in the figure. In this configuration, the peaks are observed at low frequency around 500 Hz, and at higher frequency around 800 Hz, 1100 Hz, 1400 Hz and 1500 Hz.
  • the resonators formed by the central cavity 7, of greater volume than the cavities of the structures 4, generate the low-frequency peak around 500 Hz, while the resonators formed by the four structures 4 in the form of a right prism with a triangular base into which open the orifices 8a, 8b, 11a and 11b generate the four peaks at the frequencies higher.
  • the use of the two types of cavities is particularly advantageous and makes it possible to obtain a plurality of peaks over a wide frequency range between 500 and 1500Hz.
  • Such an acoustic panel makes it possible to obtain greater absorption than the panel comprising the three orifices, in particular between 600 and 1000 Hz.
  • the acoustic panel could include a different number of three or five different orifice diameters, for example two, four or more than five.
  • the acoustic panel 1, 10 forms a monolithic structure.
  • the invention also relates to a method of manufacturing an acoustic panel 1, 10.
  • the method comprises a manufacturing step by additive manufacturing.
  • Additive manufacturing thus has the advantage of being able to manufacture an acoustic panel, for example acoustic panels 1 and 10, simply and quickly, in a single step.
  • the manufacturing step by additive manufacturing is carried out by the technique of deposition of molten filament known as "Fused Filament. Manufacture, FFF ”, particularly suited to the production of a complex structure as described above, comprising structures 4 formed by right prisms with a triangular base.
  • FFF molten filament
  • additive manufacturing is meant the manufacture of a part by successive deposition or consolidation of layers of material.
  • the acoustic elements are therefore produced in a single operation, and are therefore monolithic.
  • the acoustic panel preferably manufactured by additive manufacturing, can comprise at least one reinforced thermoplastic material and / or at least one unreinforced thermoplastic material.
  • reinforced material is meant a composite material in which fillers improve the properties, for example mechanical properties, of a matrix.
  • the first and second skin 2 and 3 of an acoustic panel can be made of a reinforced thermoplastic material, for example by carbon fibers, while simultaneously, the cavities are made of an unreinforced thermoplastic material.
  • the manufacture by additive manufacturing of such an acoustic panel can be carried out in a single operation, by a device comprising two extrusion heads, preferably by the technique of deposition of molten filament known as "Fused Filament Fabrication, FFF".
  • the acoustic panel is made of a thermoplastic polymer material, for example polyamide, or of a composite material with a polymer matrix, particularly advantageous for additive manufacturing by deposition of molten filament and allowing both to strengthen and to lighten the structure.
  • the composite material with a polymer matrix may include fillers of carbon fibers.
  • the acoustic panel thus combines mechanical strength and high sound absorption capacity.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Multimedia (AREA)
  • Chemical & Material Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Soundproofing, Sound Blocking, And Sound Damping (AREA)

Abstract

Disclosed is an acoustic panel comprising two substantially parallel skins (2, 3) between which cavities forming Helmholtz resonators are arranged, one of said skins (2, 3) being bored with orifices (8a, 8b, 9) each of which opens into one of said cavities and forms a neck of the resonators, the panel being characterised in that one or more of said cavities consists of a hollow structure (4) having the shape of a triangular-based prism.

Description

DESCRIPTION DESCRIPTION
TITRE : Panneau acoustique et procédé de fabrication associé TITLE: Acoustic panel and associated manufacturing process
Domaine technique Technical area
La présente invention concerne, de manière générale, l’ atténuation acoustique et, plus particulièrement les dispositifs destinés à l’ atténuation acoustique, notamment dans le domaine aérospatial. The present invention relates, in general, to acoustic attenuation and, more particularly, to devices intended for acoustic attenuation, in particular in the aerospace field.
Plus précisément, l’invention se rapporte à un panneau acoustique, notamment un panneau acoustique pour un ensemble propulsif. More specifically, the invention relates to an acoustic panel, in particular an acoustic panel for a propulsion unit.
L’invention concerne également un procédé de fabrication d’un tel panneau acoustique. Etat de la technique The invention also relates to a method of manufacturing such an acoustic panel. State of the art
L’une des ambitions majeures de l’industrie aérospatiale est la réduction du bruit émis par les aéronefs. One of the major ambitions of the aerospace industry is the reduction of noise emitted by aircraft.
L’une des solutions connues permettant cette réduction consiste en l’utilisation de panneaux acoustiques, par exemple sur la surface interne du carter de soufflante d’une turbomachine, et dont le mécanisme de dissipation des sons repose sur le principe de résonance de Helmholtz. One of the known solutions allowing this reduction consists in the use of acoustic panels, for example on the internal surface of the fan casing of a turbomachine, and whose sound dissipation mechanism is based on the Helmholtz resonance principle.
Un résonateur de Helmholtz (HR) consiste en une cavité connectée à l’environnement extérieur par un col. Le son peut alors pénétrer dans le résonateur par le col avant d’être dissipé dans la cavité. Le résonateur atténue le son à la fréquence propre de la chambre de résonance en suivant l’équation suivante : où Dn est le diamètre d’ ouverture du col ; Ln est la longueur du col ; Vc le volume de la cavité ; fr est la fréquence de résonance du résonateur ; et v est la vitesse du son dans l’ air. A Helmholtz (HR) resonator consists of a cavity connected to the external environment by a neck. The sound can then enter the resonator through the neck before being dissipated into the cavity. The resonator attenuates the sound at the natural frequency of the resonance chamber by following the following equation: where D n is the opening diameter of the neck; L n is the length of the neck; V c the volume of the cavity; f r is the resonant frequency of the resonator; and v is the speed of sound in air.
Les paramètres géométriques du résonateur déterminent de ce fait la fréquence à laquelle le son est dissipé. Bien qu’un tel résonateur soit particulièrement avantageux pour la dissipation du son à basse fréquence, vers 500-600 Hz, cette plage de fréquence d’ absorption est étroite, de sorte que des travaux visant à multiplier les pics d’ absorption ont été menées. Typiquement, un panneau acoustique existant, dit « panneau sandwich », et appliquant ce principe, comprend deux peaux sensiblement parallèles entre lesquelles sont situées et s’étendent des cavités formant des résonateurs de Helmholtz et par exemple organisées en nid d’abeille (section hexagonale). L’une des peaux est percée d’orifices débouchant dans les cavités et formant des cols des résonateurs. The geometric parameters of the resonator therefore determine the frequency at which the sound is dissipated. Although such a resonator is particularly advantageous for the dissipation of sound at low frequencies, around 500-600 Hz, this absorption frequency range is narrow, so work to multiply the absorption peaks has been carried out. . Typically, an existing acoustic panel, called a "sandwich panel", and applying this principle, comprises two substantially parallel skins between which are located and extend cavities forming Helmholtz resonators and for example organized in a honeycomb (hexagonal section ). One of the skins is pierced with orifices opening into the cavities and forming the necks of the resonators.
Néanmoins, les structures des résonateurs des panneaux acoustiques connus ne permettent d’ obtenir l’ absorption qu’ à une fréquence d’ absorption donnée et l’empilement de différents panneaux est nécessaire pour une absorption à différentes fréquences. Exposé de l’invention However, the resonator structures of known acoustic panels can only achieve absorption at a given absorption frequency, and stacking of different panels is necessary for absorption at different frequencies. Disclosure of the invention
L’invention a donc pour but de remédier à ces inconvénients et de proposer un panneau peu coûteux et facile à réaliser, permettant à la fois l’absorption du bruit à des fréquences relativement basses et l’ absorption du bruit sur une plage de fréquence suffisamment large. II est donc proposé un panneau acoustique comprenant deux peaux sensiblement parallèles entre lesquelles sont disposées des cavités formant des résonateurs de Helmholtz, l’une desdites peaux étant percée d’ orifices débouchant chacun dans une desdites cavités et formant un col des résonateurs. En outre, une ou plusieurs desdites cavités sont formées par une structure creuse en forme de prisme droit à base triangulaire. The object of the invention is therefore to remedy these drawbacks and to provide an inexpensive and easy to produce panel, allowing both absorption of noise at relatively low frequencies and absorption of noise over a sufficiently high frequency range. large. An acoustic panel is therefore proposed comprising two substantially parallel skins between which are arranged cavities forming Helmholtz resonators, one of said skins being pierced with orifices each opening into one of said cavities and forming a neck of the resonators. In addition, one or more of said cavities are formed by a hollow structure in the form of a right prism with a triangular base.
Avantageusement, le panneau acoustique peut comprendre un ou plusieurs ensembles de structures en forme de prisme droit à base triangulaire délimitées par des parois latérales et comportant chacun une ou plusieurs desdites cavités. Advantageously, the acoustic panel can comprise one or more sets of structures in the form of a right prism with a triangular base delimited by side walls and each comprising one or more of said cavities.
De préférence, un ou plusieurs ensembles comprennent au moins quatre structures en forme de prisme droit à base triangulaire chacune et une cavité centrale formée entre les structures formées par un prisme droit à base triangulaire. Selon un mode de réalisation, ladite peau percée d’ orifices peut comprendre un premier orifice et un deuxième orifice débouchant respectivement dans une première cavité et dans une deuxième cavité parmi les quatre cavités formées par une structure en forme de prisme droit à base triangulaire et un troisième orifice débouchant dans la cavité centrale. Preferably, one or more assemblies comprise at least four structures in the form of a right prism with a triangular base each and a central cavity formed between the structures formed by a right prism with a triangular base. According to one embodiment, said skin pierced with orifices may comprise a first orifice and a second orifice opening respectively into a first cavity and into a second cavity among the four cavities formed by a structure in the form of a right prism with a triangular base and a third orifice opening into the central cavity.
Selon un autre mode de réalisation, ladite peau percée d’ orifices comprend un quatrième orifice et un cinquième orifice débouchant respectivement dans une troisième cavité et une quatrième cavité parmi les quatre cavités formées par une structure en forme de prisme droit à base triangulaire. According to another embodiment, said skin pierced with orifices comprises a fourth orifice and a fifth orifice opening respectively into a third cavity and a fourth cavity among the four cavities formed by a structure in the form of a right prism with a triangular base.
De préférence, le panneau acoustique comporte deux diamètres ou plus d’ orifice différents. Preferably, the acoustic panel has two or more different orifice diameters.
Avantageusement, les structures formées par un prisme droit à base triangulaire sont connectées à l’une desdites peaux par une de leurs arêtes, l’interface entre l’ arête et la peau pouvant comprendre une portion élargie. Advantageously, the structures formed by a right triangular prism are connected to one of said skins by one of their ridges, the interface between the ridge and the skin possibly comprising an enlarged portion.
De préférence, le panneau acoustique forme une structure monolithique. Preferably, the acoustic panel forms a monolithic structure.
L’invention concerne également un procédé de fabrication d’un panneau acoustique, le procédé comprenant une étape de fabrication par fabrication additive d’un panneau acoustique comme décrit précédemment. The invention also relates to a method of manufacturing an acoustic panel, the method comprising a step of manufacturing by additive manufacturing of an acoustic panel as described above.
De préférence, l’étape de fabrication par fabrication additive est réalisée par la technique de dépôt de filament fondu dite « Fused Filament Fabrication, FFF ». Brève description des dessins Preferably, the step of manufacturing by additive manufacturing is carried out by the technique of deposition of molten filament known as "Fused Filament Fabrication, FFF". Brief description of the drawings
D’ autres buts, avantages et caractéristiques ressortiront de la description qui va suivre, donnée à titre purement illustratif et faite en référence au dessin annexé sur lequel : Other aims, advantages and characteristics will emerge from the following description, given for illustrative purposes only and made with reference to the appended drawing in which:
[Fig 1] illustre un panneau acoustique selon un premier mode de réalisation conforme à l’invention, formé par une pluralité d’ensembles de cavités dans le cœur de résonance et d’une peau percée comportant trois orifices par ensemble de cavités. [Fig 2] est une vue en perspective d’un ensemble de cavités de la pluralité d’ensemble de cavités du cœur de résonance du panneau acoustique selon le premier mode de réalisation illustré à la figure 1. [Fig 1] illustrates an acoustic panel according to a first embodiment according to the invention, formed by a plurality of sets of cavities in the resonance core and of a pierced skin comprising three orifices per set of cavities. [Fig 2] is a perspective view of one set of cavities of the plurality of set of resonant heart cavities of the acoustic panel according to the first embodiment illustrated in Figure 1.
[Fig 3] est une vue de dessous de l’ensemble de cavités du cœur de résonance illustré à la figure 2. [Fig 3] is a bottom view of the resonant heart cavity assembly shown in Figure 2.
[Fig 4] illustre un panneau acoustique selon le premier mode de réalisation, dans lequel les cavités d’un ensemble de cavités sont disposées selon une configuration alternative, tête bêche. [Fig 4] illustrates an acoustic panel according to the first embodiment, in which the cavities of a set of cavities are arranged in an alternative configuration, head to tail.
[Fig 5] est un graphe représentant l’évolution du coefficient d’ absorption en fonction de la fréquence associé à un panneau acoustique selon le premier mode de réalisation illustré à la figure 4. [Fig 5] is a graph representing the evolution of the absorption coefficient as a function of the frequency associated with an acoustic panel according to the first embodiment illustrated in Figure 4.
[Fig 6] illustre un panneau acoustique selon un deuxième mode de réalisation conforme à l’invention, formé par une pluralité d’ensembles de cavités dans le cœur de résonance et d’une peau percée comportant cinq orifices par ensemble de cavités. [Fig 6] illustrates an acoustic panel according to a second embodiment according to the invention, formed by a plurality of sets of cavities in the resonant heart and a pierced skin comprising five orifices per set of cavities.
[Fig 7] est un graphe représentant l’évolution du coefficient d’ absorption en fonction de la fréquence associé à un panneau acoustique selon le deuxième mode de réalisation illustré à la figure 6. [Fig 7] is a graph representing the evolution of the absorption coefficient as a function of the frequency associated with an acoustic panel according to the second embodiment illustrated in Figure 6.
Exposé détaillé d’un premier mode de réalisation La figure 1 illustre un panneau acoustique 1 pour turbomachine, conforme à l’invention. Detailed description of a first embodiment FIG. 1 illustrates an acoustic panel 1 for a turbomachine, according to the invention.
Le panneau acoustique 1 est un panneau dit « panneau sandwich ». Il comprend des première et deuxième peaux 2 et 3 sensiblement parallèles entre lesquelles sont disposées des cavités formant des résonateurs de Helmholtz. The acoustic panel 1 is a so-called “sandwich panel” panel. It comprises first and second substantially parallel skins 2 and 3 between which are arranged cavities forming Helmholtz resonators.
L’une desdites peaux, dans cet exemple la première peau 2, est percée d’ orifices débouchant chacun dans l’une desdites cavités et formant un col des résonateurs. One of said skins, in this example the first skin 2, is pierced with orifices each opening into one of said cavities and forming a neck of the resonators.
De plus, une ou plusieurs desdites cavités sont formées par une structure 4 creuse en forme de prisme droit à base triangulaire. In addition, one or more of said cavities are formed by a hollow structure 4 in the form of a right prism with a triangular base.
Comme on peut le voir sur les figures 2 et 3, la structure 4 en forme de prisme droit à base triangulaire comporte deux bases triangulaires 4a et 4b opposées et deux faces rectangulaires 4c et 4d opposées s’étendant depuis une face carrée commune 4e. La jonction des deux bases 4a et 4b et des deux faces 4c et 4d forme une arête 5 disposée à l’ opposé de la face carrée 4e. La structure 4 est creuse et renferme ainsi une cavité. As can be seen in Figures 2 and 3, the structure 4 in the form of a right prism with a triangular base comprises two opposing triangular bases 4a and 4b and two opposite rectangular faces 4c and 4d extending from a common square face 4e. The junction of the two bases 4a and 4b and the two faces 4c and 4d form an edge 5 disposed opposite to the square face 4e. The structure 4 is hollow and thus contains a cavity.
Toutes les cavités sont de préférence formées par des structures 4 en forme de prisme droit à base triangulaire, formant une configuration en nid d’ abeille entre les deux peaux 2 et 3. All the cavities are preferably formed by structures 4 in the form of a right prism with a triangular base, forming a honeycomb configuration between the two skins 2 and 3.
Les cavités des différentes structures 4 en forme de prisme droit à base triangulaire sont indépendantes les unes des autres et ne communiquent pas. The cavities of the various structures 4 in the form of a right prism with a triangular base are independent of each other and do not communicate.
De préférence, les structures 4 formant les cavités sont délimitées en plusieurs ensembles ou cellules par des parois latérales 6. Le panneau acoustique est ainsi formé par une pluralité d’ensembles de structures 4 en forme de prisme droit à base triangulaire. Preferably, the structures 4 forming the cavities are delimited in several sets or cells by side walls 6. The acoustic panel is thus formed by a plurality of sets of structures 4 in the form of a right prism with a triangular base.
A la figure 2, seules deux des quatre parois latérales 6 d’un ensemble ont été représentées pour une compréhension plus aisée de l’ arrangement des structures 4. In Figure 2, only two of the four side walls 6 of a set have been shown for an easier understanding of the arrangement of the structures 4.
Dans l’exemple illustré à la figure 1 , chaque ensemble comprend quatre structures 4 en forme de prisme droit à base triangulaire. Une vue en perspective et une vue de dessous d’un ensemble sont représentées aux figures 2 et 3. Les quatre structures 4 représentées sont disposées à 90° les unes par rapport aux autres, par rapport à un axe passant par les deux peaux 2 et 3 et perpendiculaires aux deux peaux 2 et 3. Cette agencement permet avantageusement d’ optimiser l’espace. In the example illustrated in Figure 1, each set comprises four structures 4 in the form of a right prism with a triangular base. A perspective view and a bottom view of an assembly are shown in Figures 2 and 3. The four structures 4 shown are arranged at 90 ° relative to each other, relative to an axis passing through the two skins 2 and 3 and perpendicular to the two skins 2 and 3. This arrangement advantageously makes it possible to optimize the space.
De plus, les quatre structures 4 d’un ensemble sont disposées de sorte que chaque arête 5 est disposée en regard de la deuxième peau 3. In addition, the four structures 4 of a set are arranged so that each edge 5 is arranged opposite the second skin 3.
Chaque ensemble comprend également une cavité centrale 7 formée entre les structures 4 formées par un prisme droit à base triangulaire. En d’ autres termes, la cavité centrale 7 correspond à l’espace libre au sein d’un ensemble délimité par les parois latérales 6, entre les structures 4. Selon le premier mode de réalisation représenté, la peau percée d’ orifices, qui ici correspond à la première peau 2, peut comprendre trois orifices au sein d’un même ensemble. Un premier orifice 8a et un deuxième orifice 8b débouchent respectivement dans une première cavité et dans une deuxième cavité parmi les quatre cavités formées par une structure en forme de prisme droit à base triangulaire, de préférence au niveau des faces carrées 4e. Each assembly also comprises a central cavity 7 formed between the structures 4 formed by a right prism with a triangular base. In other words, the central cavity 7 corresponds to the free space within an assembly delimited by the side walls 6, between the structures 4. According to the first embodiment shown, the skin pierced with orifices, which here corresponds to the first skin 2, can include three orifices within the same assembly. A first orifice 8a and a second orifice 8b open out respectively into a first cavity and into a second cavity among the four cavities formed by a structure in right prism shape with triangular base, preferably at the level of the 4th square faces.
En outre, un troisième orifice 9 débouche dans la cavité centrale 7.In addition, a third orifice 9 opens into the central cavity 7.
Les premier et deuxième orifices 8a et 8b sont, dans cet exemple, de diamètres différents. De plus, le diamètre du troisième orifice 9 est supérieur aux diamètres des premier et deuxième orifices 8a et 8b. The first and second orifices 8a and 8b are, in this example, of different diameters. In addition, the diameter of the third orifice 9 is greater than the diameters of the first and second orifices 8a and 8b.
Par exemple, les premier et deuxième orifices 8a et 8b peuvent être disposés de sorte qu’ils débouchent dans deux des quatre structures 4 formées par un prisme droit à base triangulaire, disposées en diagonale au sein d’un même ensemble de structures 4. For example, the first and second orifices 8a and 8b can be arranged so that they open into two of the four structures 4 formed by a right triangular prism, arranged diagonally within the same set of structures 4.
Dans ce mode de réalisation, deux des quatre structures 4 formées par un prisme droit à base triangulaire ne sont pas utilisées comme cavité de résonance. In this embodiment, two of the four structures 4 formed by a right triangular prism are not used as resonance cavity.
Les structures 4 formées par un prisme droit à base triangulaire sont connectées à l’une des desdites peaux 2 et 3, dans cet exemple la deuxième peau 3, par l’arête 5. De préférence, l’interface entre l’ arête 5 et la peau comprend une portion élargie ou bordure renforçant la stabilité mécanique du panneau acoustique via le renforcement de la connexion entre les structures 4 et la deuxième peau. Les quatre cavités des structures 4 en forme de prisme droit à base triangulaire forment ainsi chacune un résonateur de Helmholtz. The structures 4 formed by a right triangular prism are connected to one of said skins 2 and 3, in this example the second skin 3, by the edge 5. Preferably, the interface between the edge 5 and the skin comprises an enlarged portion or border reinforcing the mechanical stability of the acoustic panel via the reinforcement of the connection between the structures 4 and the second skin. The four cavities of structures 4 in the form of a right prism with a triangular base thus each form a Helmholtz resonator.
Selon une alternative illustrée à la figure 4, les structures 4 en forme de prisme droit à base triangulaire peuvent être disposées selon une configuration tête bêche afin d’ optimiser l’espace au sein du panneau acoustique. According to an alternative illustrated in Figure 4, the structures 4 in the form of a right prism with a triangular base can be arranged in a head-to-tail configuration in order to optimize the space within the acoustic panel.
Le graphe de la figure 5 représente l’évolution du coefficient d’ absorption en fonction de la fréquence, en Hz, mesurée sur un panneau acoustique de configuration à trois orifices, telle qu’illustrée à la figure 4, les structures disposées tête bêche. Dans l’exemple illustré, l’épaisseur de la première peau percée, et donc du col associé aux orifices 8a, 8b et 9 a été choisie égale à 4mm et le diamètre des premier, deuxième et troisième orifices 8a, 8b et 9 est respectivement de 2, 2.5 et 3 mm. Dans cette configuration, trois pics d’ absorption bien définis sont observables sur la figure. Dans cette configuration, les pics sont observables autour de 500 Hz, 1100 Hz et 1400 Hz. The graph of FIG. 5 represents the evolution of the absorption coefficient as a function of the frequency, in Hz, measured on an acoustic panel of configuration with three orifices, as illustrated in FIG. 4, the structures arranged head to tail. In the example illustrated, the thickness of the first pierced skin, and therefore of the neck associated with the orifices 8a, 8b and 9 has been chosen equal to 4mm and the diameter of the first, second and third orifices 8a, 8b and 9 is respectively of 2, 2.5 and 3 mm. In this configuration, three well defined absorption peaks are observable in the figure. In this configuration, the peaks are observable around 500 Hz, 1100 Hz and 1400 Hz.
Les résonateurs formés par la cavité centrale 7, de volume supérieur aux cavités des structures 4, génèrent le pic à basse fréquence autour de 500 Hz, alors que les résonateurs formés par les deux structures 4 en forme de prisme droit à base triangulaire dans lesquels débouchent les orifices 8a et 8b génèrent les deux pics à des fréquences élevées, autour de 1 100 et 1400 Hz. L’utilisation des deux types de cavités est particulièrement avantageuse et permet d’obtenir une pluralité de pics sur une large plage de fréquences comprise entre 500 et 1500Hz. The resonators formed by the central cavity 7, of greater volume than the cavities of the structures 4, generate the low-frequency peak around 500 Hz, while the resonators formed by the two structures 4 in the form of a right prism with a triangular base into which open the orifices 8a and 8b generate the two peaks at high frequencies, around 1100 and 1400 Hz. The use of the two types of cavities is particularly advantageous and makes it possible to obtain a plurality of peaks over a wide range of frequencies between 500 and 1500Hz.
Exposé détaillé d’un deuxième mode de réalisation Detailed description of a second embodiment
La figure 6 illustre un deuxième mode de réalisation de panneau acoustique 10 dans lequel la peau percée comprend cinq orifices. De manière similaire au premier mode de réalisation illustré à la figure 1 , la première peau 2 comprend un premier orifice 8a et un deuxième orifice 8b débouchant respectivement dans une première cavité et dans une deuxième cavité parmi les quatre cavités formées par une structure 4 en forme de prisme droit à base triangulaire, de préférence au niveau des faces carrées 4e. FIG. 6 illustrates a second embodiment of acoustic panel 10 in which the pierced skin comprises five orifices. In a similar manner to the first embodiment illustrated in FIG. 1, the first skin 2 comprises a first orifice 8a and a second orifice 8b opening respectively into a first cavity and into a second cavity among the four cavities formed by a structure 4 in the form of right triangular prism, preferably at the level of the square faces 4th.
En outre, la première peau 2 comprend un quatrième orifice l ia et un cinquième orifice 1 1b débouchant respectivement dans une troisième cavité et une quatrième cavité parmi les quatre cavités formées par une structure 4 en forme de prisme droit à base triangulaire. In addition, the first skin 2 comprises a fourth orifice l ia and a fifth orifice 11b opening respectively into a third cavity and a fourth cavity among the four cavities formed by a structure 4 in the form of a right prism with a triangular base.
De préférence, les différents orifices 8a, 8b, 9, l i a et 1 1b possèdent quatre ou cinq diamètres différents. Preferably, the different orifices 8a, 8b, 9, 11a and 11b have four or five different diameters.
Le graphe de la figure 7 représente l’évolution du coefficient d’ absorption en fonction de la fréquence, en Hz, mesurée sur un panneau acoustique de configuration à cinq orifices, telle qu’illustrée à la figure 6. Dans l’exemple illustré, l’épaisseur de la première peau percée, et donc du col associé aux orifices 8a, 8b et 9 a été choisi égal à 3mm et le diamètre des premier, deuxième, troisième, quatrième et cinquième orifices 8a, 8b et 9 sont respectivement de 2, 2.5, 3.5, 3 et 3 mm. Cinq pics d’ absorption bien définis sont observables sur la figure. Dans cette configuration, les pics sont observés à basse fréquence autour de 500 Hz, et à fréquence plus élevée autour de 800 Hz, 1100 Hz, 1400 Hz et 1500 Hz. Les résonateurs formés par la cavité centrale 7, de volume supérieur aux cavités des structures 4, génèrent le pic à basse fréquence autour de 500 Hz, alors que les résonateurs formés par les quatre structures 4 en forme de prisme droit à base triangulaire dans lesquels débouchent les orifices 8a, 8b, l i a et 11b génèrent les quatre pics aux fréquences plus élevées. The graph of FIG. 7 represents the evolution of the absorption coefficient as a function of the frequency, in Hz, measured on an acoustic panel of configuration with five orifices, as illustrated in FIG. 6. In the example illustrated, the thickness of the first pierced skin, and therefore of the neck associated with the orifices 8a, 8b and 9 has been chosen equal to 3mm and the diameter of the first, second, third, fourth and fifth orifices 8a, 8b and 9 are respectively 2 , 2.5, 3.5, 3 and 3 mm. Five well-defined absorption peaks can be seen in the figure. In this configuration, the peaks are observed at low frequency around 500 Hz, and at higher frequency around 800 Hz, 1100 Hz, 1400 Hz and 1500 Hz. The resonators formed by the central cavity 7, of greater volume than the cavities of the structures 4, generate the low-frequency peak around 500 Hz, while the resonators formed by the four structures 4 in the form of a right prism with a triangular base into which open the orifices 8a, 8b, 11a and 11b generate the four peaks at the frequencies higher.
L’utilisation des deux types de cavités est particulièrement avantageuse et permet d’obtenir une pluralité de pics sur une large plage de fréquences comprise entre 500 et 1500Hz. The use of the two types of cavities is particularly advantageous and makes it possible to obtain a plurality of peaks over a wide frequency range between 500 and 1500Hz.
Un tel panneau acoustique permet d’ obtenir une absorption supérieure au panneau comportant les trois orifices, en particulier entre 600 et 1000 Hz. Une large plage de fréquence d’ absorption, entre 500 et 1500 Hz, est obtenue. Such an acoustic panel makes it possible to obtain greater absorption than the panel comprising the three orifices, in particular between 600 and 1000 Hz. A wide absorption frequency range, between 500 and 1500 Hz, is obtained.
Bien entendu, on pourra prévoir que le panneau acoustique comprenne un nombre différent de trois ou cinq diamètres d’ orifices différents, par exemple deux, quatre ou plus de cinq. Of course, provision could be made for the acoustic panel to include a different number of three or five different orifice diameters, for example two, four or more than five.
De préférence, le panneau acoustique 1 , 10 forme une structure monolithique. Preferably, the acoustic panel 1, 10 forms a monolithic structure.
Par monolithique, on entend au sens de l’invention une structure formée d’un seul bloc. Comme cela a été développé ci-avant, les panneaux acoustiques 1 ,By monolithic is meant within the meaning of the invention a structure formed from a single block. As has been developed above, the acoustic panels 1,
10 selon l’invention permettent une absorption du bruit sur une large plage de fréquence 600- 1500 Hz, via de multiples pics d’ absorption. 10 according to the invention allow noise absorption over a wide frequency range 600-1500 Hz, via multiple absorption peaks.
L’invention concerne également un procédé de fabrication d’un panneau acoustique 1, 10. Le procédé comprend une étape de fabrication par fabrication additive. La fabrication additive a ainsi pour avantage de pouvoir fabriquer un panneau acoustique, par exemple les panneaux acoustiques 1 et 10, simplement et rapidement, en une seule étape. The invention also relates to a method of manufacturing an acoustic panel 1, 10. The method comprises a manufacturing step by additive manufacturing. Additive manufacturing thus has the advantage of being able to manufacture an acoustic panel, for example acoustic panels 1 and 10, simply and quickly, in a single step.
De préférence, l’étape de fabrication par fabrication additive est réalisée par la technique de dépôt de filament fondu dite « Fused Filament Fabrication, FFF », particulièrement adaptée à la réalisation d’une structure complexe telle que décrite précédemment, comprenant des structures 4 formées par des prismes droits à base triangulaire. Preferably, the manufacturing step by additive manufacturing is carried out by the technique of deposition of molten filament known as "Fused Filament. Manufacture, FFF ”, particularly suited to the production of a complex structure as described above, comprising structures 4 formed by right prisms with a triangular base.
Par fabrication additive, on entend la fabrication d’une pièce par dépôt ou consolidation successif des couches de matière. By additive manufacturing is meant the manufacture of a part by successive deposition or consolidation of layers of material.
Les éléments acoustiques sont donc réalisés en une seule opération, et sont donc monolithiques. The acoustic elements are therefore produced in a single operation, and are therefore monolithic.
Le panneau acoustique, fabriqué de préférence par fabrication additive, peut comprendre au moins un matériau thermoplastique renforcé et/ou au moins un matériau thermoplastique non renforcé. The acoustic panel, preferably manufactured by additive manufacturing, can comprise at least one reinforced thermoplastic material and / or at least one unreinforced thermoplastic material.
Par matériau renforcé, on entend un matériau composite dans lequel des charges viennent améliorer les propriétés, par exemple mécanique, d’une matrice. By reinforced material is meant a composite material in which fillers improve the properties, for example mechanical properties, of a matrix.
Selon un exemple, les première et deuxième peaux 2 et 3 d’un panneau acoustique peuvent être réalisées en un matériau thermoplastique renforcé, par exemple par des fibres de carbone, alors que simultanément, les cavités sont réalisées en un matériau thermoplastique non renforcé. La fabrication par fabrication additive d’un tel panneau acoustique peut être réalisée en une seule opération, par un dispositif comprenant deux têtes d’extrusion, de préférence par la technique de dépôt de filament fondu dite « Fused Filament Fabrication, FFF ». According to one example, the first and second skin 2 and 3 of an acoustic panel can be made of a reinforced thermoplastic material, for example by carbon fibers, while simultaneously, the cavities are made of an unreinforced thermoplastic material. The manufacture by additive manufacturing of such an acoustic panel can be carried out in a single operation, by a device comprising two extrusion heads, preferably by the technique of deposition of molten filament known as "Fused Filament Fabrication, FFF".
De préférence, le panneau acoustique est fabriqué en un matériau polymère thermoplastique, par exemple le polyamide, ou en un matériau composite à matrice polymère, particulièrement avantageux pour la fabrication additive par dépôt de filament fondu et permettant à la fois de renforcer et d’ alléger la structure. Selon un exemple de réalisation, le matériau composite à matrice polymère pourra comporter des charges de fibres de carbone. Preferably, the acoustic panel is made of a thermoplastic polymer material, for example polyamide, or of a composite material with a polymer matrix, particularly advantageous for additive manufacturing by deposition of molten filament and allowing both to strengthen and to lighten the structure. According to an exemplary embodiment, the composite material with a polymer matrix may include fillers of carbon fibers.
Le panneau acoustique combine ainsi tenue mécanique et capacité d’ absorption des bruits élevées. The acoustic panel thus combines mechanical strength and high sound absorption capacity.
Il est à noter que l’ on pourra également prévoir que la réalisation des différents orifices 8a, 8b, 9, l i a et 11b soit effectuée dans une seconde étape, suivant l’étape de fabrication par fabrication additive du panneau acoustique 1 , 10, par un procédé mécanique. It should be noted that provision could also be made for the production of the various orifices 8a, 8b, 9, 11a and 11b to be carried out in a second step, following the step of manufacturing by additive manufacturing of the acoustic panel 1, 10, by a mechanical process.

Claims

REVENDICATIONS
1. Panneau acoustique comprenant deux peaux (2, 3) sensiblement parallèles entre lesquelles sont disposées des cavités formant des résonateurs de Helmholtz, l’une desdites peaux (2, 3) étant percée d’orifices (8a, 8b, 9) débouchant chacun dans l’une desdites cavités et formant un col des résonateurs, caractérisé en ce qu’une ou plusieurs desdites cavités sont formées par une structure (4) creuse en forme de prisme droit à base triangulaire. 1. Acoustic panel comprising two skins (2, 3) substantially parallel between which are arranged cavities forming Helmholtz resonators, one of said skins (2, 3) being pierced with orifices (8a, 8b, 9) each opening in one of said cavities and forming a neck of the resonators, characterized in that one or more of said cavities are formed by a hollow structure (4) in the form of a right prism with a triangular base.
2. Panneau acoustique selon la revendication 1 , caractérisé en ce qu’il comprend un ou plusieurs ensembles de structures (4) creuses en forme de prisme droit à base triangulaire délimitées par des parois latérales (6) et comportant chacun une ou plusieurs desdites cavités. 2. Acoustic panel according to claim 1, characterized in that it comprises one or more sets of hollow structures (4) in the form of a right prism with a triangular base delimited by side walls (6) and each comprising one or more of said cavities. .
3. Panneau acoustique selon la revendication 2, caractérisé en ce qu’un ou plusieurs ensembles comprennent au moins quatre structures (4) creuses en forme de prisme droit à base triangulaire et une cavité centrale (7) formée entre les structures (4) creuses en forme de prisme droit à base triangulaire. 3. Acoustic panel according to claim 2, characterized in that one or more sets comprise at least four hollow structures (4) in the form of a right prism with a triangular base and a central cavity (7) formed between the structures (4) hollow. in the form of a right prism with a triangular base.
4. Panneau acoustique selon la revendication 3, caractérisé en ce que ladite peau (2) percée d’ orifices comprend un premier orifice (8a) et un deuxième orifice (8) débouchant respectivement dans une première cavité et dans une deuxième cavité parmi les quatre cavités formées par une structure (4) en forme de prisme droit à base triangulaire et un troisième orifice (9) débouchant dans la cavité centrale (7). 4. Acoustic panel according to claim 3, characterized in that said skin (2) pierced with orifices comprises a first orifice (8a) and a second orifice (8) opening respectively into a first cavity and into a second cavity among the four. cavities formed by a structure (4) in the form of a right prism with a triangular base and a third orifice (9) opening into the central cavity (7).
5. Panneau acoustique selon la revendication 4, caractérisé en ce que ladite peau (2) percée d’orifices comprend un quatrième orifice (l ia) et un cinquième orifice (11b) débouchant respectivement dans une troisième cavité et une quatrième cavité parmi les quatre cavités formées par une structure (4) en forme de prisme droit à base triangulaire. 5. Acoustic panel according to claim 4, characterized in that said skin (2) pierced with orifices comprises a fourth orifice (l ia) and a fifth orifice (11b) opening respectively into a third cavity and a fourth cavity among the four. cavities formed by a structure (4) in the form of a right prism with a triangular base.
6. Panneau acoustique selon l’une quelconque des revendications précédentes, caractérisé en ce qu’il comporte deux diamètres ou plus d’ orifice différents. 6. Acoustic panel according to any one of the preceding claims, characterized in that it comprises two or more diameters of different orifice.
7. Panneau acoustique selon l’une quelconque des revendications précédentes, caractérisé en ce que les structures (4) formées par un prisme droit à base triangulaire sont connectées à l’une des desdites peaux (2, 3) par une de leurs arêtes, l’interface entre l’ arête (5) et la peau (2) comprenant une portion élargie (5). 7. Acoustic panel according to any one of the preceding claims, characterized in that the structures (4) formed by a right triangular prism are connected to one of said skins (2, 3) by one of their edges, the interface between the ridge (5) and the skin (2) comprising an enlarged portion (5).
8. Panneau acoustique selon l’une quelconque des revendications précédentes, caractérisé en ce qu’il forme une structure monolithique. 8. Acoustic panel according to any one of the preceding claims, characterized in that it forms a monolithic structure.
9. Procédé de fabrication d’un panneau acoustique, le procédé comprenant une étape de fabrication par fabrication additive d’un panneau acoustique (1 , 10) selon l’une quelconque des revendications précédentes. 9. A method of manufacturing an acoustic panel, the method comprising a step of manufacturing by additive manufacturing of an acoustic panel (1, 10) according to any one of the preceding claims.
10. Procédé de fabrication d’un panneau acoustique selon la revendication 9, caractérisé en ce que les première et deuxième peaux (2, 3) sont réalisées en un matériau thermoplastique renforcé et les cavités sont réalisées en un matériau thermoplastique non renforcé. 10. A method of manufacturing an acoustic panel according to claim 9, characterized in that the first and second skins (2, 3) are made of a reinforced thermoplastic material and the cavities are made of an unreinforced thermoplastic material.
11. Procédé de fabrication selon la revendication 9 ou 10, caractérisé en ce que l’étape de fabrication par fabrication additive est réalisée par la technique de dépôt de filament fondu dite « Fused Filament Fabrication, FFF ». 11. The manufacturing method according to claim 9 or 10, characterized in that the manufacturing step by additive manufacturing is carried out by the molten filament deposition technique called "Fused Filament Fabrication, FFF".
EP21742162.7A 2020-06-23 2021-06-07 Acoustic panel and associated manufacturing method Pending EP4169013A1 (en)

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CA3084631A CA3084631A1 (en) 2020-06-23 2020-06-23 Acoustic panel and associated manufacturing method
PCT/FR2021/051015 WO2021260286A1 (en) 2020-06-23 2021-06-07 Acoustic panel and associated manufacturing method

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EP (1) EP4169013A1 (en)
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BE554083A (en) * 1956-02-18
US3734234A (en) * 1971-11-08 1973-05-22 Lockheed Aircraft Corp Sound absorption structure
GB0016149D0 (en) * 2000-06-30 2000-08-23 Short Brothers Plc A noise attenuation panel
US9978354B2 (en) * 2016-04-15 2018-05-22 Rohr, Inc. Acoustic panel with vertical stiffeners
US11059559B2 (en) * 2018-03-05 2021-07-13 General Electric Company Acoustic liners with oblique cellular structures

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