EP0897174B1 - Sound absorbing panel featuring at least one acoustically resistive layer, and its manufacturing process - Google Patents

Sound absorbing panel featuring at least one acoustically resistive layer, and its manufacturing process Download PDF

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Publication number
EP0897174B1
EP0897174B1 EP98450013A EP98450013A EP0897174B1 EP 0897174 B1 EP0897174 B1 EP 0897174B1 EP 98450013 A EP98450013 A EP 98450013A EP 98450013 A EP98450013 A EP 98450013A EP 0897174 B1 EP0897174 B1 EP 0897174B1
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EP
European Patent Office
Prior art keywords
sound damping
layer
threads
reinforcing material
panel
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EP98450013A
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German (de)
French (fr)
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EP0897174A1 (en
Inventor
Alain Porte
Robert Andre
Hervé Batard
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Airbus Operations SAS
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Airbus Operations SAS
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    • 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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00—Stock material or miscellaneous articles
    • Y10T428/24—Structurally defined web or sheet [e.g., overall dimension, etc.]
    • Y10T428/24149—Honeycomb-like

Definitions

  • the present invention relates to an acoustically absorbent panel provided with at least one acoustically resistive layer especially for applications in the manufacture of nacelle walls of aircraft engine engines and the method of manufacturing this panel.
  • Helmholtz type resonators that allow reactive attenuation certain radial acoustic components under certain conditions of sizing and material.
  • a resonator includes a structure honeycomb type honeycomb between two resistive layers.
  • the alveolar structure plays the role of a cavity which makes it possible to attenuate in trapping them, some noisy frequencies reactively.
  • the acoustically resistive layer has, in addition to its role of partitioning of the alveolar structure, a dissipative role, i.e. it transforms acoustic energy into heat.
  • the present invention relates more particularly to the production of a acoustically resistive layer which provides attenuation physics by converting acoustic energy into heat, especially incident waves.
  • a first example consists in using a sheet as a resistive layer perforated in metallic or composite material, which allows to obtain a single layer, good structural strength and good control of open area rates.
  • this type of layer has a high non-linearity acoustic, high dependence on tangential flows and low resistance to erosion in the case of a composite layer.
  • a second example is the combination of a perforated sheet with a metallic or composite fabric.
  • the layer is double, which requires a process delicate, long and costly assembly with risks of non-homogeneity acoustics if this assembly presents disparities as well as risks of corrosion.
  • the choice of materials can be imposed by assembly needs.
  • a third example of the prior art consists in combining a mesh and a metallic or composite fabric.
  • the structural strength is good and the acoustic non-linearity and flow dependence phenomena are moderate.
  • the acoustic surface uniformity is open to criticism with risks of aerodynamic relief. Repeatability is difficult to achieve and adjusting the open surface area of the mesh is difficult due to dispersion in manufacturing and especially due to the unavailability of wire mesh adjustable surface area.
  • the object of the present invention is to provide a panel comprising a layer acoustically resistive to open area rate easily and precisely adjustable that meets acoustic objectives, which meets imperatives structural to withstand depressions in flight, the weight of a man in certain parts as well as the aerodynamic and inertial forces of the entry of the air towards the crankcase for example in the particular case of a nacelle of aircraft engine.
  • this material must also allow to resist the phenomenon of "fan blade off", that is to say bursting phenomenon of a blade.
  • the acoustically resistive layer according to the invention must also resist the erosion caused by the penetration of sand into the air flows, at electrical phenomena such as sweeping lightning or corrosion.
  • This resistive layer must also allow adjustment of the properties, both mechanical and acoustic, by the combination of two materials whose assembly does not pose problems.
  • the subject of the present invention is an acoustic panel made with this resistive layer.
  • the present invention also relates to a method of manufacturing a sound absorption panel provided with a resistive layer.
  • the acoustically resistive layer according to the invention comprising at least one layer of acoustic damping fabric and a reinforcing material, is characterized in that this reinforcing material comprises yarns, with an adjustable open area ratio, secured to said fabric acoustic damping.
  • wires are arranged unidirectionally, bidirectionally or still multidirectionally.
  • the invention also relates to a method for manufacturing a panel comprising a layer acoustically resistive which consists in placing the damping fabric acoustic on a mold conforming to the profile of the layer to be obtained and to place on this acoustic damping fabric wires impregnated with a binder by filament winding and removing the layer thus obtained from the mold.
  • the binder will have an adhesion capacity allowing it to remain attached to the acoustic fabric during handling, before hardening end of the panel, without additional operation.
  • the method consists in placing the fabric acoustic damping on a mold conforming to the profile of the layer to obtain and arrange on this acoustic damping fabric the wires impregnated with a binder by removal and application by pressure and to remove the layer thus obtained from the mold.
  • the binder will have a capacity of adhesion allowing it to remain integral with the acoustic fabric during handling, before the final hardening of the panel, without operation additional.
  • the invention also relates to the panels thus obtained which comprise at least one external resistive layer added to one of the faces of a core with honeycomb structure, the other side of which includes a total reflector or several souls with alveolar structure superimposed with interposition between these cores of a septum of the acoustically resistive layer type.
  • the invention also relates to the acoustic damping panel. got.
  • the invention also relates to the acoustic damping panel. obtained by the implementation of this variant of the process.
  • FIG. 1 there is shown an acoustically resistive layer 10 according to the invention which comprises an acoustic damping fabric 12 and a reinforcement ply 14 based on threads 16.
  • wires means wires, bands of yarn, strands, braids or strands of yarn, of square, round or rectangular.
  • mold indifferently a static mold, a mold movable in translation or even a mandrel movable in rotation.
  • tablecloth it can correspond to several thicknesses of mono or multidirectional wires.
  • the acoustic damping fabric 12 is for example a fabric made in stainless steel mesh and sold under the GANTOIS brand.
  • the ply 14 of reinforcement is unique and includes unidirectional wires oriented according to the weft or warp direction of the acoustic damping fabric such as shown in Figure 1 or in a direction making an angle any with the weft or warp threads.
  • the yarn density of the added ply is adjusted according to the rate acoustic opening required, mechanical resistance desired, in depending on the nature of the wires, their cross-section, the damping fabric acoustics whose damping qualities must be preserved, depending on the panel on which said acoustically resistive layer is to be applied and depending on the binder used to attach this layer to the fabric acoustic damping.
  • the acoustically resistive layer 10 with the same acoustic fabric 12 but with a bidirectional sheet 114, the crossing of the wires at an angle of 90 °, oriented parallel to the weft and warp threads of the acoustic damping fabric such as shown in Figure 2 or at any angle.
  • the ply 214 is bidirectional with an orientation wires at an angle other than 90 °, these wires themselves making an angle different from 90 ° with the weft and warp threads of the cushioning fabric acoustic.
  • the ply 314 is multidirectional with different orientations between the ply yarns and the weft and chain of acoustic damping fabric.
  • FIGS. 5A, 5B and 5C a block diagram of the production process has been shown.
  • manufacturing which consists in having a mold 18, in this case that of a nacelle of an aircraft engine, on which the fabric 12 is placed acoustic damping to make the first part of the layer resistive damping.
  • the establishment of this fabric is advantageously carried out by wrapping for example if the fabric is in strips.
  • step 5B winding which makes it possible to carry out a winding according to the steps and the desired angles, including varying them from place to place increase or decrease the density.
  • the threads can be of different natures such as carbon threads, glass or "Kevlar” marketed by the firms BROCHIER or HEXEL.
  • wires are coated with a binder as with a resin referenced 914 and marketed by BROCHIER, which allows a good bond between the fabric and the tablecloth threads.
  • the mold is represented in a simplified manner as being half a pod mold. In this case, the room is stationary and the bench is mobile but the reverse is just as achievable.
  • the shaped layer is then removed from the mold for use in combination with other layers to form a panel having a surface opposite the noise source with resistive damping capacity.
  • This monolithic layer can be added to one of the faces of a preformed panel with a honeycomb structure forming a core 22, of the type NIDA, with a total reflector 24, secured to the opposite side of the panel, of the same type as those shown in Figures 7C and 7D.
  • This panel can also include an acoustic layer resistive, called external, several layers of NIDA superimposed and between two layers of NIDA superimposed, a septum is interposed in the form of a acoustically resistive layer according to the invention. It is therefore advisable to carry out layers with complementary characteristics and suitable for achieve the best depreciation, studies that are within the reach of man art.
  • FIGS. 7A to 7E the block diagram of a method of presentation has been presented. production of a panel having at least one acoustically resistive layer, by using filament winding for the placement of the reinforcement on the acoustic damping fabric. This is how the two first steps of Figures 7A and 7B are identical to steps 5A and 5B.
  • step 7C it is planned to directly wind a core 22 in NIDA, on the sheet of wires, the connection being ensured either by crosslinking prior to NIDA, either by using the binder of the resistive layer.
  • FIGS. 7A to 7E there is shown the pendant of what is shown in FIGS. 7A to 7E but with removal and application of the wires by pressure, and a deposition of the NIDA cores and of the total reflector by draping.
  • the advantages of the resistive layer and of the panels according to the invention using this layer are many. In essence, it is possible to control and adjust the opening rate, carry out the deposits with a high accuracy and excellent repeatability, to meet objectives acoustic and structural requirements.
  • the resistance to erosion is good and the risks of relief aerodynamics are removed.
  • reinforcing wires can be placed directly on the mold and the acoustic damping fabric can be draped or banded on these wires according to the intended use of this panel and according to its conformation.
  • the pitch of the reinforcing wires is not necessarily linked to the weft pitch or the warp pitch of the fabric acoustic damping. So all the reinforcing wire arrangements can be used in the present invention as required.
  • resistive layer thus produced in situ can follow any mold profile having a developable or non-developable shape.
  • the manufacturing process makes it possible to obtain panels having complex shapes with punctual reserves to allow the realization openings or housings, this in all cases of winding the wires the reinforcement ply, plain, bi or multidirectional.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Multimedia (AREA)
  • Soundproofing, Sound Blocking, And Sound Damping (AREA)
  • Laminated Bodies (AREA)

Description

La présente invention concerne un panneau acoustiquement absorbant muni d'au moins une couche acoustiquement résistive notamment pour des applications à la fabrication de parois de nacelles de motoréacteurs d'aéronefs ainsi que le procédé de fabrication de ce panneau.The present invention relates to an acoustically absorbent panel provided with at least one acoustically resistive layer especially for applications in the manufacture of nacelle walls of aircraft engine engines and the method of manufacturing this panel.

On sait que les motoréacteurs d'avions génèrent des émissions acoustiques importantes contre lesquelles il convient de lutter avec la plus grande efficacité et de nombreux progrès ont été réalisés.We know that aircraft engine engines generate emissions important acoustics that you should fight with the most great efficiency and a lot of progress has been made.

Comme dans toutes les avancées technologiques, les gains les plus importants sont vite obtenus avec les moyens courants et bien connus mais pour améliorer encore la lutte contre les émissions acoustiques, il faut travailler de façon très pointue sur les combinaisons de matériaux ce qui est le cas dans la présente invention, les résultats obtenus pouvant être améliorés de façon significative.As in all technological advances, the most important are quickly obtained with current and well known means but to further improve the fight against acoustic emissions, we must work very pointedly on the combinations of materials which is the case in the present invention, the results obtained can be improved so significant.

On choisit pour la suite de la description l'exemple des parois de nacelles de motoréacteurs d'aéronefs car les explications peuvent être immédiatement compréhensibles mais il n'en demeure pas moins que les applications sont très nombreuses en aéronautique mais le sont tout autant dans d'autres domaines tels que les turbines à gaz, les moteurs thermiques ou encore les souffleries et plus généralement toutes les machines qui génèrent des bruits importants qu'il convient d'amortir dans des conditions difficiles de températures, de pression et/ou de résistance mécanique.We choose for the rest of the description the example of the walls of aircraft engine nacelles as the explanations can be immediately understandable but the fact remains that there are many applications in aeronautics but they are just as many in other areas such as gas turbines, heat engines or still the wind tunnels and more generally all the machines which generate significant noises that should be muted in difficult conditions temperatures, pressure and / or mechanical resistance.

Pour amortir les bruits, notamment au niveau de parois, on a recours à des résonateurs de type Helmholtz qui permettent d'atténuer de façon réactive certaines composantes acoustiques radiales dans certaines conditions de dimensionnement et de matériau. Un tel résonateur comprend une structure alvéolaire du type nids d'abeilles comprise entre deux couches résistives.To dampen noise, especially at the walls, we use Helmholtz type resonators that allow reactive attenuation certain radial acoustic components under certain conditions of sizing and material. Such a resonator includes a structure honeycomb type honeycomb between two resistive layers.

La structure alvéolaire joue le rôle d'une cavité qui permet d'atténuer en les piégeant, certaines fréquences bruyantes de façon réactive.The alveolar structure plays the role of a cavity which makes it possible to attenuate in trapping them, some noisy frequencies reactively.

La couche acoustiquement résistive a, en plus de son rôle de cloisonnement de la structure alvéolaire, un rôle dissipatif, c'est à dire qu'elle permet de transformer l'énergie acoustique en chaleur.The acoustically resistive layer has, in addition to its role of partitioning of the alveolar structure, a dissipative role, i.e. it transforms acoustic energy into heat.

La présente invention concerne plus particulièrement la réalisation d'une couche acoustiquement résistive qui permet d'obtenir une atténuation physique par transformation de l'énergie acoustique en chaleur, notamment les ondes incidentes.The present invention relates more particularly to the production of a acoustically resistive layer which provides attenuation physics by converting acoustic energy into heat, especially incident waves.

On connaít déjà des réalisations de telles couches résistives réalisées en combinant une structure alvéolaire du type nids et d'un réflecteur total arrière (FR-A-2 735 064, US-A-3 502 171, US-A-3 166 149, US-A-4 600 619, EP-A-0 367 135) .We already know the achievements of such resistive layers made in combining a honeycomb-type honeycomb structure and a total rear reflector (FR-A-2 735 064, US-A-3 502 171, US-A-3 166 149, US-A-4 600 619, EP-A -0 367 135).

Un premier exemple consiste à utiliser comme couche résistive une tôle perforée en matériau métallique ou composite, ce qui permet d'obtenir une seule et unique couche, une bonne résistance structurale et une bonne maítrise des taux de surfaces ouvertes.A first example consists in using a sheet as a resistive layer perforated in metallic or composite material, which allows to obtain a single layer, good structural strength and good control of open area rates.

Par contre, ce type de couche présente une forte non-linéarité acoustique, une forte dépendance aux écoulements tangentiels et une faible résistance à l'érosion dans le cas d'une couche composite.On the other hand, this type of layer has a high non-linearity acoustic, high dependence on tangential flows and low resistance to erosion in the case of a composite layer.

Un deuxième exemple est la combinaison d'une tôle perforée avec un tissu métallique ou composite. Dans ce cas, on retrouve la maítrise des porosités des constituants et l'ajustement possible des taux ainsi que la bonne résistance structurale avec les avantages supplémentaires d'une non-linéarité acoustique modérée et d'une dépendance modérée à l'écoulement.A second example is the combination of a perforated sheet with a metallic or composite fabric. In this case, we find the mastery of porosity of the constituents and the possible adjustment of the rates as well as the good structural strength with the added benefits of non-linearity moderate acoustics and moderate dependence on flow.

Par contre la couche est double, ce qui nécessite un procédé d'assemblage délicat, long et coûteux avec des risques de non-homogénéité acoustique si cet assemblage présente des disparités ainsi que des risques de corrosion. On note aussi que le choix des matériaux peut être imposé par les besoins de l'assemblage.However, the layer is double, which requires a process delicate, long and costly assembly with risks of non-homogeneity acoustics if this assembly presents disparities as well as risks of corrosion. We also note that the choice of materials can be imposed by assembly needs.

Un troisième exemple de l'art antérieur consiste à combiner un grillage et un tissu métallique ou composite.A third example of the prior art consists in combining a mesh and a metallic or composite fabric.

Dans ce cas, la résistance structurale est de bon niveau et les phénomènes de non-linéarité acoustique et de dépendance à l'écoulement sont modérés.In this case, the structural strength is good and the acoustic non-linearity and flow dependence phenomena are moderate.

Par contre, l'homogénéité acoustique surfacique est critiquable avec des risques de reliefs aérodynamiques. La répétabilité est difficile à obtenir et l'ajustement du taux de surface ouverte du grillage est délicat du fait d'une dispersion en fabrication et surtout du fait de la non disponibilité de grillage à taux de surface ajustable.On the other hand, the acoustic surface uniformity is open to criticism with risks of aerodynamic relief. Repeatability is difficult to achieve and adjusting the open surface area of the mesh is difficult due to dispersion in manufacturing and especially due to the unavailability of wire mesh adjustable surface area.

On peut encore citer un quatrième exemple qui consiste à utiliser un tissu métallique ou synthétique sans renfort structural.We can also cite a fourth example which consists in using a metallic or synthetic fabric without structural reinforcement.

Dans ce mode de réalisation, on se retrouve avec une couche monolithique, une faible non-linéarité, une faible dépendance aux écoulements tangentiels et une bonne maítrise du taux de porosité.In this embodiment, we are left with a layer monolithic, low non-linearity, low dependence on flows tangential and good control of the porosity rate.

Par contre, la résistance structurale est faible malheureusement plus particulièrement avec les tissus qui ont de bonnes propriétés d'amortissement acoustique.On the other hand, the structural resistance is weak unfortunately more especially with fabrics that have good cushioning properties acoustic.

L'invention est définie par les revendications.The invention is defined by the claims.

Le but de la présente invention est de proposer un panneau comportant une couche acoustiquement résistive à taux de surface ouverte aisément et précisément ajustable qui réponde aux objectifs acoustiques, qui réponde aux impératifs structuraux pour résister aux dépressions en vol, au poids d'un homme dans certaines parties ainsi qu'aux efforts aérodynamiques et inertiels de l'entrée de l'air vers le carter moteur par exemple dans le cas particulier d'une nacelle de motoréacteur d'aéronef. Dans une telle application, ce matériau doit aussi permettre de résister au phénomène de "fan blade off", c'est-à-dire au phénomène d'éclatement d'une pale. The object of the present invention is to provide a panel comprising a layer acoustically resistive to open area rate easily and precisely adjustable that meets acoustic objectives, which meets imperatives structural to withstand depressions in flight, the weight of a man in certain parts as well as the aerodynamic and inertial forces of the entry of the air towards the crankcase for example in the particular case of a nacelle of aircraft engine. In such an application, this material must also allow to resist the phenomenon of "fan blade off", that is to say bursting phenomenon of a blade.

La couche acoustiquement résistive selon l'invention doit aussi résister à l'érosion engendrée par la pénétration de sable dans les flux d'air, à des phénomènes électriques comme la foudre balayante ou encore à la corrosion.The acoustically resistive layer according to the invention must also resist the erosion caused by the penetration of sand into the air flows, at electrical phenomena such as sweeping lightning or corrosion.

Cette couche résistive doit aussi permettre un ajustement des propriétés, tant mécaniques qu'acoustiques, par la combinaison de deux matériaux dont l'assemblage ne pose pas de problèmes.This resistive layer must also allow adjustment of the properties, both mechanical and acoustic, by the combination of two materials whose assembly does not pose problems.

La présente invention a pour objet un panneau acoustique réalisé avec cette couche résistive.The subject of the present invention is an acoustic panel made with this resistive layer.

La présente invention concerne aussi un procédé de fabrication d'un panneau d'absorption acoustique muni d'une couche résistive.The present invention also relates to a method of manufacturing a sound absorption panel provided with a resistive layer.

A cet effet, la couche acoustiquement résistive selon ('invention, comprenant au moins une couche de tissu d'amortissement acoustique et un matériau de renfort, se caractérise en ce que ce matériau de renfort comprend des fils, à taux de surface ouverte ajustable, solidarisés audit tissu d'amortissement acoustique.To this end, the acoustically resistive layer according to the invention, comprising at least one layer of acoustic damping fabric and a reinforcing material, is characterized in that this reinforcing material comprises yarns, with an adjustable open area ratio, secured to said fabric acoustic damping.

Ces fils sont disposés unidirectionnellement, bidirectionnellement ou encore multidirectionnellement.These wires are arranged unidirectionally, bidirectionally or still multidirectionally.

L'invention a aussi pour objet un procédé de fabrication d'un panneau comportant une couche acoustiquement résistive qui consiste à disposer le tissu d'amortissement acoustique sur un moule conforme au profil de la couche à obtenir et à disposer sur ce tissu d'amortissement acoustique des fils imprégnés d'un liant par enroulement filamentaire et à retirer la couche ainsi obtenue du moule. Dans ce cas, le liant aura une capacité d'adhésion lui permettant de rester solidaire du tissu acoustique lors des manipulations, avant le durcissement final du panneau, sans opération supplémentaire.The invention also relates to a method for manufacturing a panel comprising a layer acoustically resistive which consists in placing the damping fabric acoustic on a mold conforming to the profile of the layer to be obtained and to place on this acoustic damping fabric wires impregnated with a binder by filament winding and removing the layer thus obtained from the mold. In this case, the binder will have an adhesion capacity allowing it to remain attached to the acoustic fabric during handling, before hardening end of the panel, without additional operation.

Selon une variante, le procédé consiste à disposer le tissu d'amortissement acoustique sur un moule conforme au profil de la couche à obtenir et à disposer sur ce tissu d'amortissement acoustique des fils imprégnés d'un liant par dépose et application par pression et à retirer la couche ainsi obtenue du moule. Dans ce cas, le liant aura une capacité d'adhésion lui permettant de rester solidaire du tissu acoustique lors des manipulations, avant le durcissement final du panneau, sans opération supplémentaire.According to a variant, the method consists in placing the fabric acoustic damping on a mold conforming to the profile of the layer to obtain and arrange on this acoustic damping fabric the wires impregnated with a binder by removal and application by pressure and to remove the layer thus obtained from the mold. In this case, the binder will have a capacity of adhesion allowing it to remain integral with the acoustic fabric during handling, before the final hardening of the panel, without operation additional.

L'invention porte aussi sur les panneaux ainsi obtenus qui comprennent au moins une couche résistive externe rapportée sur l'une des faces d'une âme à structure alvéolaire dont l'autre face comprend un réflecteur total ou plusieurs âmes à structure alvéolaire superposées avec interposition entre ces âmes d'un septum du type couche acoustiquement résistive.The invention also relates to the panels thus obtained which comprise at least one external resistive layer added to one of the faces of a core with honeycomb structure, the other side of which includes a total reflector or several souls with alveolar structure superimposed with interposition between these cores of a septum of the acoustically resistive layer type.

L'invention concerne aussi un procédé de fabrication d'un panneau acoustique comprenant une couche acoustiquement résistive qui comprend les étapes suivantes dans cet ordre ou dans l'ordre inverse :

  • mise en place d'un moule conforme au profil du panneau à obtenir,
  • dépose d'un tissu d'amortissement acoustique sur le moule,
  • enroulement filamentaire de fils imprégnés d'un liant pour constituer une nappe sur le tissu d'amortissement acoustique,
  • enroulement par banderolage ou drapage d'au moins une âme à structure alvéolaire sur cette nappe de fils, avec interposition d'une couche acoustiquement résistive entre deux âmes successives,
  • enroulement ou drapage d'une couche finale d'un réflecteur acoustique total, et
  • retrait du panneau du moule.
The invention also relates to a method for manufacturing an acoustic panel comprising an acoustically resistive layer which comprises the following steps in this order or in reverse order:
  • establishment of a mold conforming to the profile of the panel to be obtained,
  • depositing an acoustic damping fabric on the mold,
  • filament winding of son impregnated with a binder to form a sheet on the acoustic damping fabric,
  • winding by wrapping or draping at least one core with a honeycomb structure on this layer of wires, with the interposition of an acoustically resistive layer between two successive cores,
  • winding or draping of a final layer of a total acoustic reflector, and
  • removing the panel from the mold.

On peut aussi prévoir une opération intermédiaire de durcissement du liant.It is also possible to provide an intermediate operation for hardening the binder.

L'invention concerne également le panneau d'amortissement acoustique obtenu.The invention also relates to the acoustic damping panel. got.

Selon une variante, le procédé comprend les étapes suivantes :

  • mise en place d'un moule conforme au profil du panneau à obtenir,
  • dépose d'un tissu d'amortissement acoustique sur le moule,
  • dépose et application par pression de fils imprégnés d'un liant pour constituer une nappe sur le tissu d'amortissement acoustique, ,
  • enroulement par banderolage ou drapage d'au moins une âme à structure alvéolaire sur cette nappe de fils, avec interposition d'une couche acoustiquement résistive entre deux âmes successives,
  • enroulement ou drapage d'une couche finale d'un réflecteur acoustique total, et
  • retrait du panneau du moule.
According to a variant, the method comprises the following steps:
  • establishment of a mold conforming to the profile of the panel to be obtained,
  • depositing an acoustic damping fabric on the mold,
  • removal and application by pressure of threads impregnated with a binder to form a sheet on the acoustic damping fabric,,
  • winding by wrapping or draping at least one core with a honeycomb structure on this layer of wires, with the interposition of an acoustically resistive layer between two successive cores,
  • winding or draping of a final layer of a total acoustic reflector, and
  • removing the panel from the mold.

On peut aussi prévoir une opération intermédiaire de durcissement du liant.It is also possible to provide an intermediate operation for hardening the binder.

L'invention concerne également le panneau d'amortissement acoustique obtenu par la mise en oeuvre de cette variante du procédé.The invention also relates to the acoustic damping panel. obtained by the implementation of this variant of the process.

L'invention est maintenant décrite en regard des dessins annexés qui représentent plusieurs modes de réalisation, ceci à travers les différentes figures sur lesquelles :

  • la figure 1 représente un premier mode de réalisation de type unidirectionnel,
  • la figure 2 représente un deuxième mode de type bidirectionnel avec un angle de croisement de 90°,
  • la figure 3 représente un troisième mode de type bidirectionnel avec un angle de croisement identique mais de valeur quelconque,
  • la figure 4 représente un quatrième mode de réalisation de type multidirectionnel,
  • les figures 5A à 5C représentent un synoptique des étapes du procédé pour la réalisation d'une couche acoustiquement résistive selon l'invention par enroulement filamentaire,
  • les figures 6A à 6C représentent un synoptique des étapes du procédé pour la réalisation d'une couche acoustiquement résistive selon l'invention par dépose et application par pression,
  • les figures 7A à 7E représentent un synoptique des étapes du procédé pour la réalisation d'un panneau d'absorption acoustique ayant une couche acoustiquement résistive selon l'invention par enroulement filamentaire, et
  • les figures 8A à 8E représentent un synoptique des étapes du procédé pour la réalisation d'un panneau d'absorption acoustique ayant une couche acoustiquement résistive selon l'invention par dépose et application par pression.
The invention is now described with reference to the appended drawings which represent several embodiments, this through the various figures in which:
  • FIG. 1 represents a first embodiment of the unidirectional type,
  • FIG. 2 represents a second bidirectional type mode with a crossing angle of 90 °,
  • FIG. 3 represents a third mode of bidirectional type with an identical crossing angle but of any value,
  • FIG. 4 represents a fourth embodiment of the multidirectional type,
  • FIGS. 5A to 5C represent a block diagram of the steps of the method for producing an acoustically resistive layer according to the invention by filament winding,
  • FIGS. 6A to 6C represent a block diagram of the steps of the method for producing an acoustically resistive layer according to the invention by removal and application by pressure,
  • FIGS. 7A to 7E represent a block diagram of the steps of the method for producing an acoustic absorption panel having an acoustically resistive layer according to the invention by filament winding, and
  • FIGS. 8A to 8E represent a block diagram of the steps of the method for producing an acoustic absorption panel having an acoustically resistive layer according to the invention by removal and application by pressure.

Sur la figure 1, on a représenté une couche 10 acoustiquement résistive selon l'invention qui comprend un tissu 12 d'amortissement acoustique et une nappe 14 de renfort à base de fils 16.In Figure 1, there is shown an acoustically resistive layer 10 according to the invention which comprises an acoustic damping fabric 12 and a reinforcement ply 14 based on threads 16.

On entend pour la suite de la description par "fils", des fils, des bandes de fils, des mèches, des tresses ou des brins de fils, à section carrée, ronde ou rectangulaire. De même, afin d'homogénéiser les termes, on appelle "moule" indifféremment un moule statique, un moule mobile en translation ou encore un mandrin mobile en rotation. Quant au terme "nappe" il peut correspondre à plusieurs épaisseurs de fils mono ou multidirectionnels.For the remainder of the description, the term "wires" means wires, bands of yarn, strands, braids or strands of yarn, of square, round or rectangular. Similarly, in order to standardize the terms, we call "mold" indifferently a static mold, a mold movable in translation or even a mandrel movable in rotation. As for the term "tablecloth" it can correspond to several thicknesses of mono or multidirectional wires.

Le tissu 12 d'amortissement acoustique est par exemple un tissu réalisé en grillage inoxydable et commercialisé sous la marque GANTOIS.The acoustic damping fabric 12 is for example a fabric made in stainless steel mesh and sold under the GANTOIS brand.

Dans le premier mode de réalisation de la figure 1, la nappe 14 de renfort est unique et comprend des fils unidirectionnels orientés suivant le sens de trame ou de chaíne du tissu d'amortissement acoustique comme montré sur la figure 1 ou encore suivant une direction faisant un angle quelconque avec les fils de trame ou de chaíne.In the first embodiment of FIG. 1, the ply 14 of reinforcement is unique and includes unidirectional wires oriented according to the weft or warp direction of the acoustic damping fabric such as shown in Figure 1 or in a direction making an angle any with the weft or warp threads.

La densité en fils de la nappe rapportée est réglée en fonction du taux d'ouverture acoustique requis, des résistances mécaniques souhaitées, en fonction de la nature des fils, de leur section, du tissu d'amortissement acoustique dont on doit préserver les qualités d'amortissement, en fonction du panneau sur lequel ladite couche acoustiquement résistive doit être rapportée et en fonction du liant utilisé pour rapporter cette nappe sur le tissu d'amortissement acoustique.The yarn density of the added ply is adjusted according to the rate acoustic opening required, mechanical resistance desired, in depending on the nature of the wires, their cross-section, the damping fabric acoustics whose damping qualities must be preserved, depending on the panel on which said acoustically resistive layer is to be applied and depending on the binder used to attach this layer to the fabric acoustic damping.

On peut aussi réaliser la couche 10 acoustiquement résistive avec le même tissu acoustique 12 mais avec une nappe 114 bidirectionnelle, le croisement des fils se faisant suivant un angle de 90°, orientée parallèlement aux fils de trame et de chaíne du tissu d'amortissement acoustique comme montré sur la figure 2 ou suivant un angle quelconque. It is also possible to produce the acoustically resistive layer 10 with the same acoustic fabric 12 but with a bidirectional sheet 114, the crossing of the wires at an angle of 90 °, oriented parallel to the weft and warp threads of the acoustic damping fabric such as shown in Figure 2 or at any angle.

Sur la figure 3, la nappe 214 est bidirectionnelle avec une orientation des fils suivant un angle différent de 90°, ces fils faisant eux-mêmes un angle différent de 90° avec les fils de trame et de chaíne du tissu d'amortissement acoustique.In FIG. 3, the ply 214 is bidirectional with an orientation wires at an angle other than 90 °, these wires themselves making an angle different from 90 ° with the weft and warp threads of the cushioning fabric acoustic.

Sur la figure 4, la nappe 314 est multidirectionnelle avec des orientations différentes entre les fils de la nappe et les fils de trame et de chaíne du tissu d'amortissement acoustique.In FIG. 4, the ply 314 is multidirectional with different orientations between the ply yarns and the weft and chain of acoustic damping fabric.

Sur les figures 5A, 5B et 5C, on a montré un synoptique du procédé de fabrication qui consiste à disposer d'un moule 18, en l'occurrence celui d'une nacelle d'un motoréacteur d'aéronef, sur lequel on dispose le tissu 12 d'amortissement acoustique pour réaliser la première partie de la couche d'amortissement résistif. La mise en place de ce tissu est avantageusement réalisée par banderolage par exemple si le tissu se présente en bandes.In FIGS. 5A, 5B and 5C, a block diagram of the production process has been shown. manufacturing which consists in having a mold 18, in this case that of a nacelle of an aircraft engine, on which the fabric 12 is placed acoustic damping to make the first part of the layer resistive damping. The establishment of this fabric is advantageously carried out by wrapping for example if the fabric is in strips.

Ensuite, on procède à l'enroulement filamentaire des fils comme montré à l'étape 5B, enroulement qui permet de réaliser un bobinage suivant les pas et les angles souhaités, y compris en les faisant varier suivant l'endroit en sorte d'augmenter ou de diminuer la densité.Then we proceed to the filament winding of the wires as shown in step 5B, winding which makes it possible to carry out a winding according to the steps and the desired angles, including varying them from place to place increase or decrease the density.

Les fils peuvent être de différentes natures comme des fils en carbone, verre ou "Kevlar" commercialisés par les firmes BROCHIER ou HEXEL.The threads can be of different natures such as carbon threads, glass or "Kevlar" marketed by the firms BROCHIER or HEXEL.

Ces fils sont enduits d'un liant comme par une résine référencée 914 et commercialisée par BROCHIER, ce qui permet une bonne liaison entre le tissu et les fils de la nappe.These wires are coated with a binder as with a resin referenced 914 and marketed by BROCHIER, which allows a good bond between the fabric and the tablecloth threads.

Il convient ensuite de retirer le moule 18. Pour cela, avantageusement, on réalise un moule rétractable et réutilisable ou un moule perdu qui est détruit lors de la récupération de la couche finie.It is then necessary to remove the mold 18. For this, advantageously, we make a retractable and reusable mold or a lost mold which is destroyed when recovering the finished layer.

Dans le cas de certaines formes de pièces avec des moules présentant des contre-dépouilles ou n'ayant pas un profil de révolution, il peut être nécessaire de réaliser la nappe 14, 114, 214 ou 314 de fils par une dépose et par une application par pression. Ceci est avantageusement réalisé avec un banc 20 et un mouvement relatif suivant les axes nécessaires entre le moule et ledit banc. In the case of certain shapes of parts with molds having undercuts or not having a profile of revolution, it can be necessary to make the sheet 14, 114, 214 or 314 of son by removing and by pressure application. This is advantageously achieved with a bench 20 and a relative movement along the axes necessary between the mold and said bench.

Sur la figure 6A, le moule est représenté de façon simplifiée comme étant un demi-moule de nacelle. Dans ce cas, la pièce est immobile et le banc est mobile mais l'inverse est tout aussi réalisable.In FIG. 6A, the mold is represented in a simplified manner as being half a pod mold. In this case, the room is stationary and the bench is mobile but the reverse is just as achievable.

Sur ce moule on dépose le tissu d'amortissement acoustique par tout moyen adapté tel que le drapage ou le compactage.On this mold we place the acoustic damping fabric by all suitable means such as draping or compaction.

Une fois le tissu en place, on procède à la dépose et à l'application par pression de fils imprégnés, de même type que précédemment.Once the fabric is in place, we proceed to the removal and application by pressure of impregnated wires, of the same type as above.

On retrouve là les mêmes avantages de la dépose de fils avec des densités variables en fonction des besoins.Here we find the same advantages of removing wires with varying densities as required.

La couche en forme est ensuite retirée du moule pour une utilisation en combinaison avec d'autres couches pour former un panneau ayant une surface en vis à vis de la source de bruit à capacité d'amortissement résistif.The shaped layer is then removed from the mold for use in combination with other layers to form a panel having a surface opposite the noise source with resistive damping capacity.

Cette couche monolithique peut être rapportée sur une des faces d'un panneau préformé avec une structure alvéolaire formant une âme 22, du type NIDA, avec un réflecteur 24 total, solidarisé sur la face opposée du panneau, du même type que ceux montrés sur les figures 7C et 7D.This monolithic layer can be added to one of the faces of a preformed panel with a honeycomb structure forming a core 22, of the type NIDA, with a total reflector 24, secured to the opposite side of the panel, of the same type as those shown in Figures 7C and 7D.

Ce panneau peut aussi comprendre une couche acoustiquement résistive, dite extérieure, plusieurs couches de NIDA superposées et entre deux couches de NIDA superposées, on interpose un septum sous forme d'une couche acoustiquement résistive, selon l'invention. Il convient alors de réaliser des couches ayant des caractéristiques complémentaires et adaptées pour atteindre les meilleurs amortissements, études qui sont à la portée de l'homme de l'art.This panel can also include an acoustic layer resistive, called external, several layers of NIDA superimposed and between two layers of NIDA superimposed, a septum is interposed in the form of a acoustically resistive layer according to the invention. It is therefore advisable to carry out layers with complementary characteristics and suitable for achieve the best depreciation, studies that are within the reach of man art.

Sur les figures 7A à 7E, on a présenté le synoptique d'un procédé de réalisation d'un panneau ayant au moins une couche acoustiquement résistive, en recourant à l'enroulement filamentaire pour la mise en place des fils de renfort sur le tissu d'amortissement acoustique. C'est ainsi que les deux premières étapes des figures 7A et 7B sont identiques aux étapes 5A et 5B.In FIGS. 7A to 7E, the block diagram of a method of presentation has been presented. production of a panel having at least one acoustically resistive layer, by using filament winding for the placement of the reinforcement on the acoustic damping fabric. This is how the two first steps of Figures 7A and 7B are identical to steps 5A and 5B.

Par contre, à l'étape 7C, il est prévu d'enrouler directement une âme 22 en NIDA, sur la nappe de fils, la liaison étant assurée soit par réticulation préalable du NIDA, soit en utilisant le liant de la couche résistive. On the other hand, in step 7C, it is planned to directly wind a core 22 in NIDA, on the sheet of wires, the connection being ensured either by crosslinking prior to NIDA, either by using the binder of the resistive layer.

Dans ce mode de réalisation d'un produit ayant un axe de révolution, on effectue cette opération par banderolage.In this embodiment of a product having an axis of revolution, we does this by wrapping.

Sur cette âme en NIDA, on vient rapporter de façon définitive un réflecteur total, voir figure 7D.On this soul in NIDA, we come to report definitively a total reflector, see figure 7D.

Il convient dans ce cas de prévoir un liant disposé à l'interface entre le NIDA et ce réflecteur 24 total.In this case it is necessary to provide a binder arranged at the interface between the NIDA and this reflector 24 total.

Le retrait du moule permet, comme montré sur la figure 7E, de disposer d'un panneau d'amortissement acoustique du type cellules de HELMHOLTZ avec au moins une couche d'amortissement de type résistif.The removal of the mold allows, as shown in Figure 7E, to have of an acoustic damping panel of the cell type of HELMHOLTZ with at least one resistive type damping layer.

Il est aussi possible de réaliser un panneau avec plusieurs couches de NIDA superposées et dans ce cas, on enroule autant d'autres âmes de NIDA que nécessaire pour obtenir les effets souhaités en prenant soin d'intercaler si besoin des septums entre chaque superposition d'âmes, sous forme d'autres couches acoustiquement résistives telles que celles qui viennent d'être décrites, unidirectionnelles, bidirectionnelles ou multidirectionnelles.It is also possible to make a panel with several layers of NIDA superimposed and in this case, we wind as many other souls of NIDA as necessary to obtain the desired effects, taking care to interpose if need the septums between each superposition of souls, in the form of others acoustically resistive layers such as those just described, unidirectional, bidirectional or multidirectional.

Sur les figures 8A à 8E, on a représenté le pendant de ce qui est montré sur les figures 7A à 7E mais avec une dépose et une application des fils par pression, et un dépôt des âmes en NIDA et du réflecteur total par drapage.In Figures 8A to 8E, there is shown the pendant of what is shown in FIGS. 7A to 7E but with removal and application of the wires by pressure, and a deposition of the NIDA cores and of the total reflector by draping.

Le retrait du moule permet d'obtenir un panneau conformé ayant des qualités d'amortissement intéressantes.Removal of the mold makes it possible to obtain a shaped panel having interesting damping qualities.

Les avantages de la couche résistive et des panneaux selon l'invention utilisant cette couche sont nombreux. Essentiellement, il est possible de maítriser et d'ajuster le taux d'ouverture, de réaliser les déposes avec un grande précision et une excellente répétabilité, pour satisfaire les objectifs acoustiques et les exigences structurales.The advantages of the resistive layer and of the panels according to the invention using this layer are many. In essence, it is possible to control and adjust the opening rate, carry out the deposits with a high accuracy and excellent repeatability, to meet objectives acoustic and structural requirements.

En outre, l'utilisation de nappes, du fait de leur forme aplatie, augmente la surface de liaison, ce qui assure une bonne qualité à l'assemblage.In addition, the use of tablecloths, due to their flattened shape, increases the bonding surface, which ensures good quality in the assembly.

De telles couches permettent d'obtenir une bonne homogénéité acoustique mais aussi des non-linéarité et dépendance à l'écoulement tangentiel modérées.Such layers make it possible to obtain good homogeneity acoustics but also non-linearity and dependence on flow moderate tangential.

La résistance à l'érosion est bonne et les risques de relief aérodynamique sont supprimés. The resistance to erosion is good and the risks of relief aerodynamics are removed.

On note aussi que les fils de renfort peuvent être disposés à même le moule et que le tissu d'amortissement acoustique peut être drapé ou banderolé sur ces fils suivant l'usage prévu de ce panneau et suivant sa conformation.It is also noted that the reinforcing wires can be placed directly on the mold and the acoustic damping fabric can be draped or banded on these wires according to the intended use of this panel and according to its conformation.

On peut aussi noter un avantage important qui découle du procédé selon la présente invention, celui de réaliser le panneau acoustique en un seul morceau. En effet, le nombre de jonctions est réduit, ce qui conduit à augmenter la surface efficace acoustique, à diminuer la masse et simultanément à réduire les coûts de fabrication.One can also note an important advantage which results from the process according to the present invention, that of making the acoustic panel in a single piece. Indeed, the number of junctions is reduced, which leads to increase the effective acoustic surface, decrease the mass and simultaneously reduce manufacturing costs.

Sur les différentes figures, on a simplifié la représentation des fils de renfort sur le tissu acoustique, essentiellement pour des raisons de clarté et pour faciliter la compréhension de ces figures.In the various figures, the representation of the wires of reinforcement on the acoustic fabric, mainly for reasons of clarity and to facilitate the understanding of these figures.

Il est bien entendu que le pas des fils de renfort n'est pas nécessairement lié au pas de trame ou au pas de chaíne du tissu d'amortissement acoustique. Donc toutes les dispositions de fils de renfort sont utilisables dans la présente invention en fonction des besoins.It is understood that the pitch of the reinforcing wires is not necessarily linked to the weft pitch or the warp pitch of the fabric acoustic damping. So all the reinforcing wire arrangements can be used in the present invention as required.

On remarque aussi que la couche résistive ainsi réalisée in situ peut suivre tout profil de moule ayant une forme développable ou non développable.We also note that the resistive layer thus produced in situ can follow any mold profile having a developable or non-developable shape.

Le procédé de fabrication permet l'obtention de panneaux ayant des formes complexes avec réserves ponctuelles pour permettre la réalisation d'ouvertures ou de logements, ceci dans tous les cas d'enroulement des fils de la nappe de renfort, uni, bi ou multidirectionnel.The manufacturing process makes it possible to obtain panels having complex shapes with punctual reserves to allow the realization openings or housings, this in all cases of winding the wires the reinforcement ply, plain, bi or multidirectional.

Claims (8)

  1. A sound damping panel comprising at least one core (22) with an alveolar structure, a total reflector (24) attached to one face of a core (32) opposite to the incident sound wave and at least one acoustically resistive layer, one of which is attached to one face of a core oriented towards the incident sound wave, said acoustically resistive layer comprising a layer (12) of sound damping cloth and a reinforcing material fixed to said sound damping cloth, characterised in that the reinforcing material is formed of at least one layer of non-woven threads (16) whose density is adjusted according to the level of open surface required.
  2. A sound damping panel according to claim 1, characterised in that it comprises several cores (22) with an alveolar structure, superimposed with the interposing between these cores of a septum consisting of a layer of sound damping cloth (12) and at least one layer of non-woven threads (16) whose density is adjusted according to the level of open surface required, fixed to said sound damping cloth.
  3. A sound damping panel according to claim 1 or 2, characterised in that the threads of the reinforcing material are disposed unidirectionally.
  4. A sound damping panel according to claim 1 or 2, characterised in that the threads of the reinforcing material are disposed bidirectionally.
  5. A sound damping panel according to claim 1 or 2, characterised in that the threads of the reinforcing material are disposed multidirectionally.
  6. A method of manufacturing a sound damping panel, including the following steps, in this order or in a different order:
    placing a mould in accordance with the profile of the panel to be obtained,
    placing a sound damping cloth on the mould,
    placing a reinforcing material fixed to said sound damping cloth,
    winding at least one core with an alveolar structure on this layer of threads by hoop casing or draping, with possibly the interposing of an acoustically resistive layer between two successive cores,
    winding or draping a final layer of a total acoustic reflector, and
    removing the panel from the mould,
    characterised in that the deposition of the reinforcing material includes depositing threads impregnated with a binder in order to constitute on the sound damping cloth a layer of non-woven threads (16) whose density is adjusted according to the level of open surface required.
  7. A method of manufacturing a sound damping panel according to claim 6, characterised in that the depositing of threads of the reinforcing material is carried out by filament winding.
  8. A method of manufacturing a sound damping panel according to Claim 6 or 7, characterised in that an intermediate operation of hardening the binder is carried out.
EP98450013A 1997-08-13 1998-08-06 Sound absorbing panel featuring at least one acoustically resistive layer, and its manufacturing process Expired - Lifetime EP0897174B1 (en)

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FR9710490A FR2767411B1 (en) 1997-08-13 1997-08-13 ACOUSTICALLY RESISTIVE LAYER, METHOD FOR MANUFACTURING THE SAME AND ACOUSTICALLY ABSORBING PANEL PROVIDED WITH AT LEAST ONE SUCH LAYER
FR9710490 1997-08-13

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FR2767411A1 (en) 1999-02-19
DE69819424D1 (en) 2003-12-11
US6268038B1 (en) 2001-07-31
ES2210694T3 (en) 2004-07-01
EP0897174A1 (en) 1999-02-17
DE69819424T2 (en) 2004-09-09
FR2767411B1 (en) 2001-11-16

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