EP1157372B1 - Method for making a sound reducing panel with resistive layer having structural property and resulting panel - Google Patents

Method for making a sound reducing panel with resistive layer having structural property and resulting panel Download PDF

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Publication number
EP1157372B1
EP1157372B1 EP00993660A EP00993660A EP1157372B1 EP 1157372 B1 EP1157372 B1 EP 1157372B1 EP 00993660 A EP00993660 A EP 00993660A EP 00993660 A EP00993660 A EP 00993660A EP 1157372 B1 EP1157372 B1 EP 1157372B1
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EP
European Patent Office
Prior art keywords
layer
acoustic
properties
fibres
structural
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EP00993660A
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German (de)
French (fr)
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EP1157372A1 (en
Inventor
Robert Andre
Alain Porte
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
    • G10K11/172—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using resonance effects
    • 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
    • Y10T156/00—Adhesive bonding and miscellaneous chemical manufacture
    • Y10T156/10—Methods of surface bonding and/or assembly therefor
    • Y10T156/1052—Methods of surface bonding and/or assembly therefor with cutting, punching, tearing or severing
    • Y10T156/1056—Perforating lamina

Definitions

  • the present invention relates to an acoustic attenuation panel more particularly intended for at least partial absorption of the sound energy of gas flow at high speed.
  • the invention will be described in its application to the production of panels attenuation of the noise generated in particular by aircraft turbine engines, in certain locations of the nacelle, for example at the entrance and at the exit of the fan channel, but it is understood that the invention is likely applications in any other environment where necessary or desirable to use a panel type structure combining lightness, great mechanical resistance and acoustic properties.
  • the panel according to the invention is of the well-known type consisting of sandwich comprising an alveolar structure of the flanked honeycomb type, aerodynamic vein side, an acoustically resistive layer and, on the side opposite, a rear reflector.
  • the honeycomb structure can be simple, i.e. with a single resonator or with a single-layer or multiple cellular core, that is to say with superimposed resonators or with a cellular core formed of several superimposed layers separated or not by septa.
  • the acoustically resistive layer has a dissipative role. When the wave sound passes through it, viscous effects occur which transform partially the acoustic energy in heat.
  • the alveolar structure which behind the resistive layer traps this sound wave thanks to the cells which behave like waveguides perpendicular to the surface of said layer, the wave reflecting on the rear reflector of the panel.
  • such a panel must, because of its environment, withstand severe conditions of use. In particular, he must not present any risk of delamination of the resistive layer even in the presence of strong depression and must be resistant to erosion or abrasion as well as corrosion, have good electrical conductivity and be able to absorb the energy of a mechanical impact.
  • Such a panel must also and of course have properties sufficient structural in particular to receive and transfer efforts aerodynamic, inertial and those related to the maintenance of the nacelle, towards the nacelle / engine structural connections.
  • the surface condition of the resistive layer must finally satisfy the aerodynamic requirements of the environment.
  • Such a panel includes a honeycomb flanked on one side by a acoustic resistive layer consisting of a rigid and thin mesh of material composite and, on the other side, a reflector.
  • Such a structure has the advantage of good control of the percentage of open area of the resistive layer due to the fact that said mesh is formed of orthogonal wicks of fibers for example of carbon delimiting openings between them, the size of which can be adjusted during the process impregnating the fibers with a thermosetting resin and then hardening of the resin, the fabric being subjected to shaping under pressure and under temperature in order to obtain said rigid and thin mesh.
  • the resistive layer thus obtained also exhibits good structural strength and finally has the advantage of being a component monolayer.
  • This layer resistive has a strong acoustic non-linearity which makes its surface impedance varies significantly with the acoustic level.
  • the grazing flow will produce a phenomenon of narrowing of the air passage sections in the holes.
  • the acoustic resistance of this layer will also depend on the speed of this grazing flow.
  • the resistive layer provides a frequency window of efficiency limited, as well as low resistance to erosion.
  • the resistive layer is formed of two components, namely, a layer structural, honeycomb side, and a microporous layer on the surface.
  • the structural layer is formed of a fabric of carbon fibers with relatively wide meshes defining an opening rate of about 30% of the total surface of the layer.
  • the surface microporous layer is a fine mesh fabric of fibers mineral or synthetic or a metallic fabric, acting as a shock absorber acoustic.
  • the panel includes a resistive layer on the surface, two nests superimposed bees separated by a resistive layer, called a septum, usually microporous and a reflector.
  • Such an arrangement makes it possible to obtain panels whose exposed face to aerodynamic flows and which is defined by the tissue association metallic / metallic perforated sheet, has both good properties acoustic and good structural properties.
  • the metal sheet is first prepared then pierced before being put in place and shaped on the assembly, also carried out, of the honeycomb structure, the reflector and the metallic fabric.
  • the shape of the pre-perforated sheet will cause local deformation of parts of the sheet and therefore of the holes located in these parts. These deformations are likely to significantly modify the area of the holes and therefore the rate of local porosity of the perforated sheet, thus causing inhomogeneity of the porosity of the sheet, detrimental to its effectiveness in terms of attenuation acoustic.
  • the invention aims to overcome the various drawbacks of these techniques known by proposing a method of manufacturing attenuation panels acoustic of the honeycomb structure flanked, on the one hand, by a reflector and, on the other hand, an acoustically resistive layer with two components acoustic property and structural property respectively, allowing to obtain panels with complex shapes, in particular with evolving curvatures can be important and in particular of monobloc panels of form general annular with or without splint, such as those intended for entry and nacelle fan channel output, presenting both very good mechanical properties and optimal acoustic properties.
  • the method of the invention makes it possible to obtain an acoustic layer resistive with remarkable acoustic and structural properties, in particular the effectiveness of the acoustic attenuation due to the very good homogeneity of the porosity rate of said acoustically resistive layer, which can be defined precisely.
  • said layer is given to structural property the porosity required by the choice of wire spacing at weaving, in the case of a fabric, the flexibility of the latter allowing to fit the mold shapes without substantial deformation of the mesh of the tissue.
  • the adjustment of the spacing of the son allows to precisely adjust the porosity rate.
  • said layer is given to structural property the porosity required by drilling said layer after autoclave cooking.
  • Drilling is performed to precise diameters and in a workpiece shape and rigid, porosity control is perfectly ensured.
  • the layer with structural properties consists of several plies of crossed threads, the plies being on either side of the layer to acoustic property.
  • the subject of the invention is also the panels obtained in accordance to the above process.
  • the panel is in one piece, annular without splint or with a single splice and is made using a symbolized mold at M in FIG. 1, of shapes and dimensions appropriate to those of the panel to obtain and on which the layers will be draped, wound or wrapped successive of the panel.
  • the first of these layers is a layer with structural property 1a, on which will then be placed a layer with acoustic property 1 b, the assembly 1a-1b forming the two components of a so-called layer 1 acoustically resistive, on which a structure will be placed alveolar 2, simple as illustrated or multiple as mentioned above.
  • the layer with structural property 1a is formed from wires pre-impregnated with a thermoplastic resin or thermosetting suitable.
  • yarn is meant yarn, fiber, wicks under form of ribbon of square or rectangular section, of carbon, glass, "Kevlar", or other mineral or organic, natural or synthetic fibers.
  • the acoustic property layer 1b is formed from a very fine fabric of carbon, glass, "Kevlar” or other mineral fibers or organic, natural or synthetic, dry or prepreg.
  • the honeycomb structure 2 is for example a paper of aramid fibers such than that known commercially as "NOMEX”.
  • the layer to be structural property constituted by a fabric draped over the mold M, or by wires deposited by winding or wrapping, is produced, then polymerized by autoclave cooking.
  • This open surface rate is advantageously of the order of 30% of the exposed surface of layer 1a.
  • the perforations 4 produced for this purpose in layer 1 a have preferably a ratio of the diameter to the thickness of the layer 1 a greater than 1 to reduce the harmful effects of acoustic non-linearity.
  • the perforations 4 are produced by various mechanical means, by laser or EDM.
  • the layer 1a After perforation of the holes 4, the layer 1a still being in place on the mold M, the acoustic property layer 1b is put in place, with possible interposition of an adhesive layer 5, then the honeycomb structure 2 is put in place with possible interposition of a second adhesive layer 6 and finally the reflector 3.
  • a second polymerization by autoclave cooking can be after layers 1b and 5 have been put in place, then a third polymerization by autoclave cooking is carried out after placement of the layers 2 and 3, a crosslinking adhesive being advantageously interposed between layers 2 and 3. Finally, the mold M is removed to release the panel finished.
  • the choice of adhesives 5, 6 and their installation methods, as well as the choice of fabric for layer 1b and the polymerization methods are determined so as to obtain an open surface rate after bonding in the layer 1b, corresponding to the desired rate, that is to say giving the resistive layer 1 the required non-linearity factor.
  • FIG. 2 is similar to that of FIG. 1, except that the layer with structural property 1'a has the layer acoustically two-component resistive 1 'is made from wicks of deposited fibers along a weft of fabric, namely warl wicks 7 and wicks of frame 8, the mesh thus produced defining passage openings 9 ( Figure 3) rectangular or square, constituting about 30% of the surface of the layer has it.
  • the layer with structural property 1'a has the layer acoustically two-component resistive 1 'is made from wicks of deposited fibers along a weft of fabric, namely warl wicks 7 and wicks of frame 8, the mesh thus produced defining passage openings 9 ( Figure 3) rectangular or square, constituting about 30% of the surface of the layer has it.
  • the fibers of the locks 7, 8 can be of the type indicated above, dry or prepreg. Wicks 7, 8 are deposited individually by winding, wrapping or manual deposit or not on a mold (no shown) similar to mold M of Figure 1. A polymerization is then performed.
  • the spacing between wicks 7, 8 and the polymerization conditions are defined so as to give the layer 1'a the non-linearity factor required.
  • the thickness of the layer with structural property 1a, 1'a is of the order of 10 times the thickness of the acoustic property layer 1b, 1'b.
  • the layer with structural property 1a can be consisting of several plies of pre-impregnated yarn fabrics or of several overlapping plies of wound or wrapped prepreg yarns.
  • the acoustically resistive layers (1, 1 ') of the panels according to the invention although made up of two components, nevertheless have excellent mechanical qualities.
  • the materials of the two components are identical and compatible and lend themselves to good bonding and constitute after polymerization a single composite sheet with almost zero risk of delamination, very resistant to erosion, abrasion, impact and moreover easy to repair.
  • the resistive layers have, due to the precise control of their porosity rate during manufacturing, very good acoustic performance especially in terms of non-linearity, their impedance does not depend on the Mach number of grazing flow.
  • the panels according to the invention are also simple and easy to achieve.
  • Figures 4a to 4d illustrate an embodiment of a panel of the type of Figure 1, on a mold (not shown) similar to the mold M.
  • crosslinking adhesive 6 is placed (FIG. 4c) on the honeycomb structure 2.
  • the adhesive 6 diffuses well in the porous mass of the layer 1 b and the junction between the end edge of the walls of the honeycomb cells 2 and the facing face of the layer 1b is established by constituting good connecting jumps to the right of the honeycomb cell bases defining cross-section bonds increasing in size as we get closer to the face of said layer 1 b.
  • the invention allows to give the acoustic component (layer 1b) a very fine thickness, much lower than that of structural layer 1 a.
  • the layer 1a may have a thickness of one millimeter, while the thickness of the layer 1b can be reduced to 0.1 millimeter without degradation of its acoustic properties.
  • Figure 4e illustrates an alternative embodiment of the assembly of layers 1 a, 1 b and 2, in which the cross-linking adhesive 5 between the layers 1a and 1b is deleted. Due, in fact, to the small thickness and the large porosity of the acoustic layer 1b, it is possible to apply the adhesive 6 than on the receiving side of the honeycomb 2.
  • the only adhesive used (6) is applied only to the right of the feet of the honeycomb cells 2, which limits the obstruction of passage openings 4 through the structural layer 1 a only areas opposite said cell feet.
  • FIGS. 4a to 4e can be used with various variants of panel structure described above.
  • This technique makes it possible to easily design and produce acoustic attenuation panels with mechanical characteristics efficient and homogeneous, adapted to various environments, in particular those mentioned above such as the nacelles of turbo-engines.
  • FIG. 5 also illustrates an alternative embodiment of the holes 4 of the structural layer 1a during their perforation, according to which the the external outlet of said holes 4 is advantageously flared, by all appropriate means, as shown in 11, so as to improve the linearity acoustic.
  • FIG. 6 illustrates another variant embodiment of the method of the invention according to which the layer with structural property is reinforced.
  • the layer with structural property consists of several layers of crossed prepreg yarns arranged on either side of the property layer acoustic 1 "b.
  • FIG. 6 On the left side of Figure 6, there is shown a first distribution of two plies of crossed wires, respectively a ply 13 of chain son, first deposited on a mold (not shown) similar to mold M of FIG. 1 and a web 14 of weft threads deposited over the layer 1 "b, ie after removal of the latter.
  • This assembly is polymerized under pressure before installation of the other components 2, 3.
  • the spacing of the wires of the plies 13, 14, 15, 16 deposited by winding or wrapping determines the porosity rate of the 1 "layer.

Description

La présente invention a trait à un panneau d'atténuation acoustique plus particulièrement destiné à l'absorption au moins partielle de l'énergie sonore de flux de gaz à grande vitesse.The present invention relates to an acoustic attenuation panel more particularly intended for at least partial absorption of the sound energy of gas flow at high speed.

L'invention sera décrite dans son application à la réalisation de panneaux d'atténuation du bruit engendré notamment par des turbomoteurs d'aéronefs, en certains emplacements de la nacelle, par exemple à l'entrée et à la sortie du canal de fan, mais il est bien entendu que l'invention est susceptible d'applications dans tout autre environnement où s'avère nécessaire ou souhaitable d'utiliser une structure du type panneau alliant légèreté, grande résistance mécanique et propriétés acoustiques.The invention will be described in its application to the production of panels attenuation of the noise generated in particular by aircraft turbine engines, in certain locations of the nacelle, for example at the entrance and at the exit of the fan channel, but it is understood that the invention is likely applications in any other environment where necessary or desirable to use a panel type structure combining lightness, great mechanical resistance and acoustic properties.

Le panneau selon l'invention est du type bien connu constitué d'un sandwich comprenant une structure alvéolaire du type nid d'abeilles flanquée, côté veine aérodynamique, d'une couche acoustiquement résistive et, du côté opposé, d'un réflecteur arrière. La structure alvéolaire peut être simple, c'est-à-dire à résonateur unique ou à âme alvéolaire monocouche, ou bien multiple, c'est-à-dire à résonateurs superposés ou à âme alvéolaire formée de plusieurs couches superposées séparées ou non par des septums.The panel according to the invention is of the well-known type consisting of sandwich comprising an alveolar structure of the flanked honeycomb type, aerodynamic vein side, an acoustically resistive layer and, on the side opposite, a rear reflector. The honeycomb structure can be simple, i.e. with a single resonator or with a single-layer or multiple cellular core, that is to say with superimposed resonators or with a cellular core formed of several superimposed layers separated or not by septa.

La couche acoustiquement résistive a un rôle dissipatif. Lorsque l'onde sonore la traverse, il se produit des effets visqueux qui transforment partiellement l'énergie acoustique en chaleur. La structure alvéolaire qui se trouve derrière la couche résistive piège cette onde sonore grâce aux cellules qui se comportent comme des guides d'onde perpendiculaires à la surface de ladite couche, l'onde se réfléchissant sur le réflecteur arrière du panneau.The acoustically resistive layer has a dissipative role. When the wave sound passes through it, viscous effects occur which transform partially the acoustic energy in heat. The alveolar structure which behind the resistive layer traps this sound wave thanks to the cells which behave like waveguides perpendicular to the surface of said layer, the wave reflecting on the rear reflector of the panel.

Pour obtenir une bonne atténuation acoustique, il est nécessaire de réunir un certain nombre de conditions dont les principales sont une bonne adéquation de la hauteur des cellules de la structure alvéolaire aux fréquences de l'onde sonore que l'on veut traiter et l'adaptation de l'impédance des couches résistives (septum et face avant) de telle sorte qu'elles produisent un maximum de dissipation aux fréquences d'intérêt.To obtain good acoustic attenuation, it is necessary to meet a number of conditions, the main ones being good adequacy of the height of the cells of the alveolar structure at the frequencies of the sound wave that we want to process and the adaptation of the impedance of resistive layers (septum and front side) so that they produce a maximum dissipation at frequencies of interest.

De plus, il est donc essentiel d'avoir une homogénéité acoustique optimale tant au niveau des couches résistives qu'à celui de la structure alvéolaire.In addition, it is therefore essential to have acoustic homogeneity optimal both in terms of the resistive layers and the structure alveolar.

Par ailleurs, un tel panneau doit, du fait de son environnement, résister à des conditions sévères d'utilisation. En particulier il ne doit pas présenter de risque de délamination de la couche résistive même en présence de forte dépression et doit être résistant à l'érosion ou abrasion ainsi qu'à la corrosion, avoir une bonne conductivité électrique et être apte à absorber l'énergie d'un impact mécanique.Furthermore, such a panel must, because of its environment, withstand severe conditions of use. In particular, he must not present any risk of delamination of the resistive layer even in the presence of strong depression and must be resistant to erosion or abrasion as well as corrosion, have good electrical conductivity and be able to absorb the energy of a mechanical impact.

Un tel panneau doit également et bien entendu avoir des propriétés structurales suffisantes pour notamment recevoir et transférer les efforts aérodynamiques, inertiels et ceux liés à la maintenance de la nacelle, vers les liaisons structurales nacelle/moteur.Such a panel must also and of course have properties sufficient structural in particular to receive and transfer efforts aerodynamic, inertial and those related to the maintenance of the nacelle, towards the nacelle / engine structural connections.

L'état de surface de la couche résistive doit enfin satisfaire aux exigences aérodynamiques de l'environnement.The surface condition of the resistive layer must finally satisfy the aerodynamic requirements of the environment.

Les panneaux d'atténuation acoustique connus, notamment ceux utilisés sur les nacelles de turbomoteurs, répondent avec plus ou moins de bonheur à l'ensemble des exigences ci-dessus.Known acoustic attenuation panels, especially those used on turbine engine nacelles, respond with more or less happiness to all of the above requirements.

Parmi ces panneaux, tous constitués sur le même principe d'une structure résonante comprenant une couche avant résistive et une structure alvéolaire fermée par un réflecteur arrière, on peut citer ceux mettant en oeuvre un traitement dit non linéaire à un seul degré de liberté et illustrés par exemple par le brevet européen EP 0 038 746 délivré au nom du Demandeur. Among these panels, all made on the same principle of a resonant structure comprising a resistive front layer and a structure honeycomb closed by a rear reflector, mention may be made of those using a so-called non-linear processing with a single degree of freedom and illustrated for example by European patent EP 0 038 746 issued in the name of the Applicant.

Un tel panneau comprend un nid d'abeilles flanqué, d'un côté, d'une couche résistive acoustique constituée d'un treillis rigide et mince en matériau composite et, de l'autre côté, d'un réflecteur.Such a panel includes a honeycomb flanked on one side by a acoustic resistive layer consisting of a rigid and thin mesh of material composite and, on the other side, a reflector.

Une telle structure présente l'avantage d'une bonne maítrise du pourcentage de surface ouverte de la couche résistive du fait que ledit treillis est formé de mèches orthogonales de fibres par exemple de carbone délimitant entre elles des ouvertures dont on peut régler la taille lors du processus d'imprégnation des fibres à l'aide d'une résine thermodurcissable puis de durcissement de la résine, le tissu étant soumis à une mise en forme sous pression et sous température afin d'obtenir ledit treillis rigide et mince.Such a structure has the advantage of good control of the percentage of open area of the resistive layer due to the fact that said mesh is formed of orthogonal wicks of fibers for example of carbon delimiting openings between them, the size of which can be adjusted during the process impregnating the fibers with a thermosetting resin and then hardening of the resin, the fabric being subjected to shaping under pressure and under temperature in order to obtain said rigid and thin mesh.

La couche résistive ainsi obtenue présente par ailleurs une bonne résistance structurale et présente enfin l'avantage d'être un composant monocouche.The resistive layer thus obtained also exhibits good structural strength and finally has the advantage of being a component monolayer.

Cependant ses inconvénients sont également substantiels. Cette couche résistive présente une forte non-linéarité acoustique qui fait que son impédance de surface varie de façon significative avec le niveau acoustique.However, its drawbacks are also substantial. This layer resistive has a strong acoustic non-linearity which makes its surface impedance varies significantly with the acoustic level.

De plus, pour ce type de couche, l'écoulement rasant va produire un phénomène de rétrécissement des sections de passage de l'air dans les trous. La résistance acoustique de cette couche va également dépendre de la vitesse de cet écoulement rasant.In addition, for this type of layer, the grazing flow will produce a phenomenon of narrowing of the air passage sections in the holes. The acoustic resistance of this layer will also depend on the speed of this grazing flow.

En outre, la couche résistive offre une fenêtre fréquentielle d'efficacité restreinte, ainsi qu'une faible résistance à l'érosion.In addition, the resistive layer provides a frequency window of efficiency limited, as well as low resistance to erosion.

Suivant une autre modalité de traitement dit linéaire, également à simple degré de liberté, illustrée par exemple par le document GB 2 130 963, la couche résistive est formée de deux composants, à savoir, une couche structurale, côté nid d'abeilles, et une couche microporeuse en surface.According to another so-called linear processing method, also simple degree of freedom, illustrated for example by the document GB 2 130 963, the resistive layer is formed of two components, namely, a layer structural, honeycomb side, and a microporous layer on the surface.

La couche structurale est formée d'un tissu de fibres de carbone à mailles relativement larges définissant un taux d'ouverture d'environ 30 % de la surface totale de la couche.The structural layer is formed of a fabric of carbon fibers with relatively wide meshes defining an opening rate of about 30% of the total surface of the layer.

La couche microporeuse de surface est un tissu à mailles fines de fibres minérales ou synthétiques ou un tissu métallique, faisant office d'amortisseur acoustique. The surface microporous layer is a fine mesh fabric of fibers mineral or synthetic or a metallic fabric, acting as a shock absorber acoustic.

Les avantages d'une telle structure sont la possibilité d'ajustement de la résistance acoustique de la couche résistive en jouant sur les deux composants de cette dernière, la réduction de la non-linéarité acoustique entraínant une dépendance moindre de la résistance acoustique vis-à-vis du niveau acoustique et de la vitesse de l'écoulement tangentiel à la surface de la couche résistive. En outre, on obtient une fenêtre fréquentielle d'efficacité plus large en comparaison avec la solution technique précédente.The advantages of such a structure are the possibility of adjusting the acoustic resistance of the resistive layer by playing on both components of the latter, reducing acoustic non-linearity resulting in less dependence of the acoustic resistance on the sound level and the velocity of the tangential flow at the surface of the resistive layer. In addition, a more efficient frequency window is obtained. large in comparison with the previous technical solution.

Par contre, une telle structure présente l'inconvénient majeur d'un assemblage supplémentaire pénalisant en temps et en coût, du fait du caractère bi-composant de la couche résistive. Si les contraintes accrues d'assemblage de cette structure ne sont pas bien maítrisées, il y a des risques d'inhomogénéité acoustique, ainsi que de délamination de la couche résistive.On the other hand, such a structure has the major drawback of additional assembly penalizing in time and cost, due to the bi-component nature of the resistive layer. If the increased constraints of assembly of this structure are not well controlled, there are risks acoustic inhomogeneity, as well as delamination of the resistive layer.

Enfin, il existe également un risque de corrosion de la couche exposée microporeuse imposant des contraintes au niveau du choix des matériaux.Finally, there is also a risk of corrosion of the exposed layer. microporous imposing constraints on the choice of materials.

Suivant une troisième technique de traitement dite à double degré de liberté, le panneau comprend une couche résistive en surface, deux nids d'abeilles superposés séparés par une couche résistive, dite septum, généralement microporeuse et un réflecteur.According to a third treatment technique known as double degree of freedom, the panel includes a resistive layer on the surface, two nests superimposed bees separated by a resistive layer, called a septum, usually microporous and a reflector.

Les avantages de cette structure sont l'obtention d'une fenêtre fréquentielle d'efficacité très importante, la possibilité d'ajustement de la résistance acoustique en jouant sur les deux couches résistives, la non-linéarité acoustique faible ou modérée.The advantages of this structure are the obtaining of a window very important frequency, the possibility of adjusting the acoustic resistance by playing on the two resistive layers, non-linearity low or moderate acoustics.

Par contre, la mise en place de deux structures alvéolaires superposées et séparées par une couche résistive rend le processus de fabrication plus long et coûteux et introduit les risques d'inhomogénéités acoustiques entraínés par de possibles désalignements des nids d'abeilles, cumulés aux effets de colle, ainsi que de propagation sonore transverse dans les zones de désalignement.By cons, the establishment of two superimposed honeycomb structures and separated by a resistive layer makes the manufacturing process longer and expensive and introduces the risks of acoustic inhomogeneities caused by possible misalignments of honeycombs, combined with glue effects, as well as transverse sound propagation in areas of misalignment.

Enfin, par le document EP 0.911.803 on connaít un panneau d'atténuation acoustique formé d'un sandwich comprenant une structure alvéolaire flanquée, d'un côté, d'un réflecteur et, de l'autre côté, d'un tissu métallique lui-même recouvert d'une feuille métallique perforée. Finally, by document EP 0.911.803 we know a panel acoustic attenuation formed of a sandwich comprising a structure honeycomb flanked on one side with a reflector and on the other side with a fabric metal itself covered with a perforated metal sheet.

Un tel agencement permet d'obtenir des panneaux dont la face exposée aux écoulements aérodynamiques et qui est définie par l'association tissu métallique/feuille perforée métallique, présente à la fois de bonnes propriétés acoustiques et de bonnes propriétés structurales.Such an arrangement makes it possible to obtain panels whose exposed face to aerodynamic flows and which is defined by the tissue association metallic / metallic perforated sheet, has both good properties acoustic and good structural properties.

Cependant, de tels panneaux peuvent présenter des inconvénients notables en particulier lorsqu'ils ont une courbure accentuée, ce qui est le cas notamment des panneaux d'entrée et de sortie de canal de fan.However, such panels can have drawbacks noticeable especially when they have an accentuated curvature, which is the case including fan channel inlet and outlet panels.

En effet, selon le document EP 0.911.803, la feuille métallique est d'abord préparée puis percée avant d'être mise en place et en forme sur l'assemblage, réalisé par ailleurs, de la structure alvéolaire, du réflecteur et du tissu métallique.In fact, according to document EP 0.911.803, the metal sheet is first prepared then pierced before being put in place and shaped on the assembly, also carried out, of the honeycomb structure, the reflector and the metallic fabric.

Du fait de la forme du panneau qui n'est pas de révolution et qui peut présenter des convexités ou concavités pouvant être accentuées, la mise en forme de la feuille pré-perforée va entraíner des déformations locales de parties de la feuille et donc des trous situés dans ces parties. Ces déformations sont susceptibles de modifier sensiblement l'aire des trous et donc le taux de porosité local de la feuille perforée, engendrant ainsi une inhomogénéité de la porosité de la feuille, préjudiciable à son efficacité en termes d'atténuation acoustique.Due to the shape of the panel which is not of revolution and which can have convexities or concavities that can be accentuated, the shape of the pre-perforated sheet will cause local deformation of parts of the sheet and therefore of the holes located in these parts. These deformations are likely to significantly modify the area of the holes and therefore the rate of local porosity of the perforated sheet, thus causing inhomogeneity of the porosity of the sheet, detrimental to its effectiveness in terms of attenuation acoustic.

Par ailleurs, une telle mise en forme est difficile car la feuille est relativement rigide.Furthermore, such shaping is difficult because the sheet is relatively rigid.

Enfin, d'une manière générale, les panneaux du type tout métallique, ce qui est le cas du panneau ci-dessus, sont de nature à poser des problèmes de corrosion.Finally, in general, all-metal type panels, this which is the case of the panel above, are likely to cause problems of corrosion.

L'invention vise à pallier les divers inconvénients de ces techniques connues en proposant un mode de fabrication de panneau d'atténuation acoustique du type à structure alvéolaire flanquée, d'une part, d'un réflecteur et, d'autre part, d'une couche acoustiquement résistive à deux composants respectivement à propriété acoustique et à propriété structurale, permettant d'obtenir des panneaux à forme complexe notamment à courbures évolutives pouvant être importantes et notamment des panneaux monoblocs de forme générale annulaire avec ou sans éclisse, tels que ceux destinés aux entrée et sortie de canal de fan de nacelles, présentant à la fois de très bonnes propriétés mécaniques et des propriétés acoustiques optimales.The invention aims to overcome the various drawbacks of these techniques known by proposing a method of manufacturing attenuation panels acoustic of the honeycomb structure flanked, on the one hand, by a reflector and, on the other hand, an acoustically resistive layer with two components acoustic property and structural property respectively, allowing to obtain panels with complex shapes, in particular with evolving curvatures can be important and in particular of monobloc panels of form general annular with or without splint, such as those intended for entry and nacelle fan channel output, presenting both very good mechanical properties and optimal acoustic properties.

A cet effet, l'invention a pour objet un procédé de fabrication d'un panneau d'atténuation acoustique selon la revendication 1 comprenant une structure alvéolaire flanquée, d'une part, d'un réflecteur et, d'autre part, d'une couche acoutiquement résistive à deux composants respectivement à propriété acoustique et à propriété structurale, caractérisé en ce qu'il consiste à mettre en place sur un moule (M), de forme appropriée au panneau

  • des fils pré-imprégnés d'une résine thermoplastique ou thermodurcissable constituant une couche à propriété structurale. Ladite couche étant constituée par drapage, bobinage ou banderolage de sorte qu'elle présente un taux de surface ouverte de l'ordre de 30 % de la surface totale de la surface exposée,
  • une couche à propriété acoustique par dessus la couche à propriété structurale, ladite couche à propriété acoustique étant constituée d'un tissu microporeux et d'épaisseur de l'ordre du dixième de celle de la couche à propriété structurale,
  • la structure alvéolaire et le réflecteur avec éventuellement adjonction d'un adhésif entre composants,
  • au moins une étape de cuisson en autoclave étant mise en oeuvre à la fin d'au moins une des étapes de mise en place ci-dessus.
To this end, the subject of the invention is a method of manufacturing an acoustic attenuation panel according to claim 1 comprising a honeycomb structure flanked, on the one hand, by a reflector and, on the other hand, an acoustically resistive layer with two components respectively with acoustic property and with structural property, characterized in that it consists in placing on a mold (M), of a shape suitable for the panel
  • wires pre-impregnated with a thermoplastic or thermosetting resin constituting a layer with structural property. Said layer being formed by draping, winding or wrapping so that it has an open surface rate of the order of 30% of the total surface of the exposed surface,
  • a layer with acoustic property over the layer with structural property, said layer with acoustic property consisting of a microporous fabric and with a thickness of the order of one tenth that of the layer with structural property,
  • the honeycomb structure and the reflector with possibly the addition of an adhesive between components,
  • at least one autoclave cooking step being implemented at the end of at least one of the above setting steps.

Le procédé de l'invention permet d'obtenir une couche acoustiquement résistive à propriétés acoustique et structurale remarquables, en particulier l'efficacité de l'atténuation acoustique du fait de la très bonne homogénéité du taux de porosité de ladite couche acoustiquement résistive, qui peut être défini avec précision.The method of the invention makes it possible to obtain an acoustic layer resistive with remarkable acoustic and structural properties, in particular the effectiveness of the acoustic attenuation due to the very good homogeneity of the porosity rate of said acoustically resistive layer, which can be defined precisely.

En effet, le fait d'utiliser des fils pré-impregnés mis en forme sur un moule non seulement permet de réaliser des formes complexes pouvant avoir des courbures prononcées, mais surtout permet une très bonne maítrise de la porosité de la couche à propriété structurale. Indeed, the fact of using pre-impregnated wires shaped on a mold not only allows for complex shapes that can have pronounced curvatures, but above all allows a very good control of the porosity of the layer with structural property.

Suivant un mode de mise en oeuvre, on confère à ladite couche à propriété structurale la porosité requise par le choix de l'écartement des fils au tissage, dans le cas d'un tissu, la souplesse de ce dernier permettant d'épouser les formes du moule sans déformation substantielle des mailles du tissu.According to one embodiment, said layer is given to structural property the porosity required by the choice of wire spacing at weaving, in the case of a fabric, the flexibility of the latter allowing to fit the mold shapes without substantial deformation of the mesh of the tissue.

Dans le cas de fils bobinés ou banderolés, le réglage de l'écartement des fils permet d'ajuster de manière précise le taux de porosité.In the case of wound or wrapped wires, the adjustment of the spacing of the son allows to precisely adjust the porosity rate.

Suivant un autre mode de mise en oeuvre, on confère à ladite couche à propriété structurale la porosité requise par perçage de ladite couche après cuisson en autoclave.According to another embodiment, said layer is given to structural property the porosity required by drilling said layer after autoclave cooking.

Le perçage s'effectuant à des diamètres précis et dans une pièce en forme et rigide, le contrôle de la porosité est parfaitement assuré.Drilling is performed to precise diameters and in a workpiece shape and rigid, porosity control is perfectly ensured.

Avantageusement et suivant un autre mode de mise en oeuvre et à des fins de renfort, la couche à propriété structurale est constituée de plusieurs nappes de fils croisés, les nappes étant de part et d'autre de la couche à propriété acoustique.Advantageously and according to another mode of implementation and at for reinforcing purposes, the layer with structural properties consists of several plies of crossed threads, the plies being on either side of the layer to acoustic property.

L'invention a également pour objet les panneaux obtenus conformément au procédé ci-dessus.The subject of the invention is also the panels obtained in accordance to the above process.

D'autres caractéristiques et avantages ressortiront de la description qui va suivre de divers modes de mises en oeuvre de l'invention, description donnée à titre d'exemple uniquement et en regard des dessins annexés sur lesquels :

  • la figure 1 est une vue en coupe et en éclaté schématique d'une structure de panneau obtenue conformément au procédé de l'invention ;
  • la figure 2 est une vue en coupe similaire illustrant un autre mode de mise en oeuvre du procédé de l'invention ;
  • la figure 3 est une vue partielle de dessus de la couche à propriété structurale du panneau de la figure 2 ;
  • les figures 4a à 4e illustrent différentes étapes de réalisation d'un panneau du type de la figure 1,
  • la figure 5 est une vue en coupe partielle illustrant un mode de collage de la couche acoustique bi-composant sur la structure alvéolaire, et
  • la figure 6 est une vue en coupe partielle illustrant une variante du procédé illustré par la figure 2.
Other characteristics and advantages will emerge from the description which follows of various embodiments of the invention, description given by way of example only and with reference to the appended drawings in which:
  • Figure 1 is a schematic sectional and exploded view of a panel structure obtained according to the method of the invention;
  • Figure 2 is a similar sectional view illustrating another embodiment of the method of the invention;
  • Figure 3 is a partial top view of the structural property layer of the panel of Figure 2;
  • FIGS. 4a to 4e illustrate different stages in the production of a panel of the type of FIG. 1,
  • FIG. 5 is a partial sectional view illustrating a method of bonding the two-component acoustic layer to the cellular structure, and
  • FIG. 6 is a partial sectional view illustrating a variant of the method illustrated in FIG. 2.

Plus précisément, le panneau est d'une seule pièce, annulaire sans éclisse ou avec une seule éclisse et est réalisé à l'aide d'un moule symbolisé en M sur la figure 1, de formes et dimensions appropriés à celles du panneau à obtenir et sur lequel seront drapées, bobinées ou banderolées les couches successives du panneau.More precisely, the panel is in one piece, annular without splint or with a single splice and is made using a symbolized mold at M in FIG. 1, of shapes and dimensions appropriate to those of the panel to obtain and on which the layers will be draped, wound or wrapped successive of the panel.

La première de ces couches est une couche à propriété structurale 1a, sur laquelle sera ensuite mise en place une couche à propriété acoustique 1 b, l'ensemble 1a-1b formant les deux composants d'une couche 1 dite acoustiquement résistive, sur laquelle sera mise en place une structure alvéolaire 2, simple comme illustré ou multiple comme évoqué plus haut.The first of these layers is a layer with structural property 1a, on which will then be placed a layer with acoustic property 1 b, the assembly 1a-1b forming the two components of a so-called layer 1 acoustically resistive, on which a structure will be placed alveolar 2, simple as illustrated or multiple as mentioned above.

Enfin, par dessus la structure alvéolaire 2 est mis en place un réflecteur conventionnel 3.Finally, over the honeycomb structure 2 is put in place a reflector conventional 3.

Conformément à l'invention, la couche à propriété structurale 1a est formée à partir de fils pré-imprégnées d'une résine thermoplastique ou thermodurcissable appropriée. Par fils, on entend des fils, fibres, mèches sous forme de ruban de section carrée ou rectangulaire, de carbone, verre, «Kevlar», ou autres fibres minérales ou organiques, naturelles ou synthétiques.According to the invention, the layer with structural property 1a is formed from wires pre-impregnated with a thermoplastic resin or thermosetting suitable. By yarn is meant yarn, fiber, wicks under form of ribbon of square or rectangular section, of carbon, glass, "Kevlar", or other mineral or organic, natural or synthetic fibers.

La couche à propriété acoustique 1b est formée d'un tissu très fin de fibres de carbone, de verre, de «Kevlar » ou autres fibres minérales ou organiques, naturelles ou synthétiques, sèches ou pré-imprégnées.The acoustic property layer 1b is formed from a very fine fabric of carbon, glass, "Kevlar" or other mineral fibers or organic, natural or synthetic, dry or prepreg.

La structure alvéolaire 2 est par exemple un papier de fibres aramides tel que celui dénommé commercialement « NOMEX ».The honeycomb structure 2 is for example a paper of aramid fibers such than that known commercially as "NOMEX".

Dans le mode de mise en oeuvre illustré par la figure 1, la couche à propriété structurale constituée par un tissu drapé sur le moule M, ou par des fils déposés par bobinage ou banderolage, est réalisée, puis polymérisée par cuisson en autoclave.In the embodiment illustrated in FIG. 1, the layer to be structural property constituted by a fabric draped over the mold M, or by wires deposited by winding or wrapping, is produced, then polymerized by autoclave cooking.

On obtient ainsi une tôle composite, rigide, lisse et en forme, qui est ensuite percée selon le taux de surface ouverte recherché.This produces a composite sheet, rigid, smooth and shaped, which is then pierced according to the desired open surface rate.

Ce taux de surface ouverte est avantageusement de l'ordre de 30% de la surface exposée de la couche 1a. This open surface rate is advantageously of the order of 30% of the exposed surface of layer 1a.

Les perforations 4 réalisées à cet effet dans la couche 1 a présentent de préférence un rapport du diamètre à l'épaisseur de la couche 1 a supérieur à 1 pour réduire les effets néfastes de la non-linéarité acoustique.The perforations 4 produced for this purpose in layer 1 a have preferably a ratio of the diameter to the thickness of the layer 1 a greater than 1 to reduce the harmful effects of acoustic non-linearity.

Les perforations 4 sont réalisées par divers moyens mécaniques, par laser ou par électroérosion.The perforations 4 are produced by various mechanical means, by laser or EDM.

Après perforation des trous 4, la couche 1a étant toujours en place sur le moule M, la couche à propriété acoustique 1b est mise en place, avec interposition éventuelle d'une couche adhésive 5, puis la structure alvéolaire 2 est mise en place avec interposition éventuelle d'une seconde couche adhésive 6 et enfin le réflecteur 3.After perforation of the holes 4, the layer 1a still being in place on the mold M, the acoustic property layer 1b is put in place, with possible interposition of an adhesive layer 5, then the honeycomb structure 2 is put in place with possible interposition of a second adhesive layer 6 and finally the reflector 3.

Une deuxième polymérisation par cuisson en autoclave peut être effectuée après mise en place des couches 1b et 5, puis une troisième polymérisation par cuisson en autoclave est effectuée après mise en place des couches 2 et 3, un adhésif de réticulation étant avantageusement interposé entre les couches 2 et 3. Enfin, le moule M est retiré pour dégager le panneau fini.A second polymerization by autoclave cooking can be after layers 1b and 5 have been put in place, then a third polymerization by autoclave cooking is carried out after placement of the layers 2 and 3, a crosslinking adhesive being advantageously interposed between layers 2 and 3. Finally, the mold M is removed to release the panel finished.

Le choix des adhésifs 5, 6 et leurs modalités de mise en place, ainsi que le choix du tissu de la couche 1b et les modalités de polymérisation sont déterminés en sorte d'obtenir un taux de surface ouverte après collage dans la couche 1b, correspondant au taux recherché, c'est-à-dire conférant à la couche résistive 1 le facteur de non-linéarité requis.The choice of adhesives 5, 6 and their installation methods, as well as the choice of fabric for layer 1b and the polymerization methods are determined so as to obtain an open surface rate after bonding in the layer 1b, corresponding to the desired rate, that is to say giving the resistive layer 1 the required non-linearity factor.

Le mode de réalisation de la figure 2 est similaire à celui de la figure 1, excepté que la couche à propriété structurale 1'a de la couche acoustiquement résistive bi-composant 1 ' est constituée à partir de mèches de fibres déposées suivant une trame de tissu, à savoir des mèches de chaíne 7 et des mèches de trame 8, le maillage ainsi réalisé définissant des ouvertures de passage 9 (figure 3) rectangulaires ou carrées, constituant environ 30 % de la surface de la couche 1'a.The embodiment of FIG. 2 is similar to that of FIG. 1, except that the layer with structural property 1'a has the layer acoustically two-component resistive 1 'is made from wicks of deposited fibers along a weft of fabric, namely warl wicks 7 and wicks of frame 8, the mesh thus produced defining passage openings 9 (Figure 3) rectangular or square, constituting about 30% of the surface of the layer has it.

Les fibres des mèches 7, 8 peuvent être du type indiqué plus haut, sèches ou pré-imprégnées. Les mèches 7, 8 sont déposées unitairement par bobinage, banderolage ou dépose manuelle ou non sur un moule (non représenté) analogue au moule M de la figure 1. Une polymérisation est ensuite effectuée.The fibers of the locks 7, 8 can be of the type indicated above, dry or prepreg. Wicks 7, 8 are deposited individually by winding, wrapping or manual deposit or not on a mold (no shown) similar to mold M of Figure 1. A polymerization is then performed.

L'espacement entre mèches 7, 8 et les conditions de polymérisation sont définis en sorte de conférer à la couche 1'a le facteur de non-linéarité requis.The spacing between wicks 7, 8 and the polymerization conditions are defined so as to give the layer 1'a the non-linearity factor required.

Dans les exemples illustrés par les figures 1 et 2, l'épaisseur de la couche à propriété structurale 1a, 1'a est de l'ordre de 10 fois l'épaisseur de la couche à propriété acoustique 1 b, 1'b.In the examples illustrated by FIGS. 1 and 2, the thickness of the layer with structural property 1a, 1'a is of the order of 10 times the thickness of the acoustic property layer 1b, 1'b.

Il est à noter que la couche à propriété structurale 1a peut être constituée de plusieurs plis de tissus de fils pré-imprégnées ou de plusieurs nappes superposées de fils pré-imprégnés bobinés ou banderolés.It should be noted that the layer with structural property 1a can be consisting of several plies of pre-impregnated yarn fabrics or of several overlapping plies of wound or wrapped prepreg yarns.

Les couches acoustiquement résistives (1, 1') des panneaux selon l'invention, bien que constituées de deux composants, présentent néanmoins d'excellentes qualités mécaniques.The acoustically resistive layers (1, 1 ') of the panels according to the invention, although made up of two components, nevertheless have excellent mechanical qualities.

En effet, les matériaux des deux composants, structural et acoustique, sont identiques et compatibles et se prêtent à un bon collage et constituent après polymérisation une tôle unique composite à risque quasi nul de délamination, très résistante à l'érosion, à l'abrasion, aux chocs et de surcroít facile à réparer.Indeed, the materials of the two components, structural and acoustic, are identical and compatible and lend themselves to good bonding and constitute after polymerization a single composite sheet with almost zero risk of delamination, very resistant to erosion, abrasion, impact and moreover easy to repair.

En outre, les couches résistives ont, du fait du contrôle précis de leur taux de porosité lors de la fabrication, une très bonne performance acoustique notamment en terme de non-linéarité, leur impédance ne dépendant pas du nombre de Mach de l'écoulement rasant.In addition, the resistive layers have, due to the precise control of their porosity rate during manufacturing, very good acoustic performance especially in terms of non-linearity, their impedance does not depend on the Mach number of grazing flow.

Les panneaux selon l'invention sont également simples et faciles à réaliser.The panels according to the invention are also simple and easy to achieve.

Les figures 4a à 4d illustrent un mode de réalisation d'un panneau du type de la figure 1, sur un moule (non représenté) analogue au moule M.Figures 4a to 4d illustrate an embodiment of a panel of the type of Figure 1, on a mold (not shown) similar to the mold M.

Après constitution et mise en forme de la composante structurale 1 a, avec le taux de surface ouverte désiré, par exemple 30 %, on applique (figure 4a) la couche d'adhésif de réticulation 5, puis on place la couche acoustique 1 b (figure 4b) et on polymérise à chaud sous pression pour assembler les deux couches 1 a, 1 b. After constitution and shaping of the structural component 1 a, with the desired open surface rate, for example 30%, we apply (figure 4a) the cross-linking adhesive layer 5, then the acoustic layer is placed 1 b (Figure 4b) and hot polymerization under pressure to assemble the two layers 1 a, 1 b.

Ensuite, on met en place (figure 4c) l'adhésif de réticulation 6 sur la structure alvéolaire 2.Next, the crosslinking adhesive 6 is placed (FIG. 4c) on the honeycomb structure 2.

Enfin (figure 5d), on assemble tous les éléments du panneau par une nouvelle étape de polymérisation sous pression à chaud, un adhésif 10 étant également mis en place sur l'autre face du nid d'abeilles au droit des pieds des cellules pour le collage de la couche réflectrice arrière 3 qui est elle-même mono ou multi-couche et dont la structure est conventionnelle.Finally (Figure 5d), we assemble all the elements of the panel by a new hot pressure polymerization step, adhesive 10 being also placed on the other side of the honeycomb in line with the feet of the cells for bonding the rear reflective layer 3 which is itself mono or multi-layer and whose structure is conventional.

Du fait de la grande porosité de la couche acoustique 1 b, on obtient une très bonne adhérence entre nid d'abeilles 2 et couche 1 b.Due to the high porosity of the acoustic layer 1 b, a very good adhesion between honeycomb 2 and layer 1 b.

En effet, l'adhésif 6 diffuse bien dans la masse poreuse de la couche 1 b et la jonction entre le bord d'extrémité des parois des alvéoles du nid d'abeilles 2 et la face en regard de la couche 1b s'établit en constituant de bons pontages de raccordement au droit des pieds de cellule du nid d'abeilles définissant des liaisons à section allant en s'accroissant au fur et à mesure que l'on se rapproche de la face de ladite couche 1 b.Indeed, the adhesive 6 diffuses well in the porous mass of the layer 1 b and the junction between the end edge of the walls of the honeycomb cells 2 and the facing face of the layer 1b is established by constituting good connecting jumps to the right of the honeycomb cell bases defining cross-section bonds increasing in size as we get closer to the face of said layer 1 b.

Il est également à noter que, d'une manière générale, l'invention permet de donner à la composante acoustique (couche 1b) une épaisseur très fine, bien inférieure à celle de la couche structurale 1 a. A titre d'exemple, la couche 1a pourra avoir une épaisseur de un millimètre, alors que l'épaisseur de la couche 1b pourra être réduite à 0,1 millimètre sans dégradation de ses propriétés acoustiques.It should also be noted that, in general, the invention allows to give the acoustic component (layer 1b) a very fine thickness, much lower than that of structural layer 1 a. For example, the layer 1a may have a thickness of one millimeter, while the thickness of the layer 1b can be reduced to 0.1 millimeter without degradation of its acoustic properties.

La figure 4e illustre une variante de réalisation de l'assemblage des couches 1 a, 1 b et 2, dans laquelle l'adhésif de réticulation 5 entre les couches 1a et 1 b est supprimé. Du fait, en effet, de la faible épaisseur et de la grande porosité de la couche acoustique 1b, il est possible de n'appliquer l'adhésif 6 que sur la face réceptrice du nid d'abeilles 2.Figure 4e illustrates an alternative embodiment of the assembly of layers 1 a, 1 b and 2, in which the cross-linking adhesive 5 between the layers 1a and 1b is deleted. Due, in fact, to the small thickness and the large porosity of the acoustic layer 1b, it is possible to apply the adhesive 6 than on the receiving side of the honeycomb 2.

L'adhésif 6, comme illustré par la figure 5, migre lors de la polymérisation dans toute l'épaisseur de la couche poreuse 1b et vient en contact avec la face en regard de la couche externe structurale 1 a. L'ensemble 1 a, 1 b, 2 est ainsi solidement fixé.The adhesive 6, as illustrated in FIG. 5, migrates during the polymerization throughout the thickness of the porous layer 1b and comes into contact with the opposite face of the structural outer layer 1 a. All 1 a, 1 b, 2 is thus securely fixed.

Dans cet ensemble, le seul adhésif utilisé (6) est déposé uniquement au droit des pieds des cellules du nid d'abeilles 2, ce qui limite l'obstruction des ouvertures de passage 4 au travers de la couche structurale 1 a aux seules zones en regard desdits pieds de cellule.In this set, the only adhesive used (6) is applied only to the right of the feet of the honeycomb cells 2, which limits the obstruction of passage openings 4 through the structural layer 1 a only areas opposite said cell feet.

La technique illustrée par les figures 4a à 4e est utilisable avec les diverses variantes de structure de panneau décrites plus haut.The technique illustrated in FIGS. 4a to 4e can be used with various variants of panel structure described above.

Cette technique permet de concevoir et réaliser facilement des panneaux d'atténuation acoustique à caractéristiques mécaniques performantes et homogènes, adaptés à divers environnements, notamment ceux mentionnés plus hauts tels que les nacelles de turbo-moteurs.This technique makes it possible to easily design and produce acoustic attenuation panels with mechanical characteristics efficient and homogeneous, adapted to various environments, in particular those mentioned above such as the nacelles of turbo-engines.

Sur la figure 5, on a également illustré une variante de réalisation des trous 4 de la couche structurale 1a lors de leur perforation, selon laquelle le débouché externe desdits trous 4 est avantageusement évasé, par tous moyens appropriés, comme représenté en 11, en sorte d'améliorer la linéarité acoustique.FIG. 5 also illustrates an alternative embodiment of the holes 4 of the structural layer 1a during their perforation, according to which the the external outlet of said holes 4 is advantageously flared, by all appropriate means, as shown in 11, so as to improve the linearity acoustic.

La figure 6 illustre une autre variante de réalisation du procédé de l'invention selon laquelle la couche à propriété structurale est renforcée. A cet effet, la couche à propriété structurale est constituée de plusieurs nappes de fils pré-imprégnés croisés disposées de part et d'autre de la couche à propriété acoustique 1"b.FIG. 6 illustrates another variant embodiment of the method of the invention according to which the layer with structural property is reinforced. In this Indeed, the layer with structural property consists of several layers of crossed prepreg yarns arranged on either side of the property layer acoustic 1 "b.

Sur la partie gauche de la figure 6, on a représenté une première distribution de deux nappes de fils croisés, respectivement une nappe 13 de fils de chaíne, déposée en premier sur un moule (non représenté) analogue au moule M de la figure 1 et une nappe 14 de fils de trame déposée par dessus la couche 1"b, c'est à dire après dépose de cette dernière.On the left side of Figure 6, there is shown a first distribution of two plies of crossed wires, respectively a ply 13 of chain son, first deposited on a mold (not shown) similar to mold M of FIG. 1 and a web 14 of weft threads deposited over the layer 1 "b, ie after removal of the latter.

Sur la partie droite de la figure 6, on a représenté une seconde distribution de trois nappes à savoir deux nappes croisées suivant une trame de tissage 15, déposées en premier sur le moule et une troisième nappe 16 de fils parallèles aux fils de l'une des nappes de la trame 15, déposée par dessus la couche à propriété acoustique 1"b.On the right side of Figure 6, a second is shown distribution of three layers, namely two layers crossed in a weft of weaving 15, deposited first on the mold and a third ply 16 of wires parallel to the wires of one of the layers of the weft 15, deposited on top the acoustic layer 1 "b.

L'ensemble des composants 13, 14, 15, 16, 1"b forme ainsi une couche acoustiquement résistive 1" à propriétés à la fois structurale et acoustique. All the components 13, 14, 15, 16, 1 "b thus form a 1 "acoustically resistive layer with both structural and acoustic.

Cet ensemble est polymérisé sous pression avant mise en place des autres composants 2, 3.This assembly is polymerized under pressure before installation of the other components 2, 3.

L'espacement des fils des nappes 13, 14, 15, 16 déposés par bobinage ou banderolage détermine le taux de porosité de la couche 1".The spacing of the wires of the plies 13, 14, 15, 16 deposited by winding or wrapping determines the porosity rate of the 1 "layer.

Claims (9)

  1. A method of manufacturing an acoustic attenuation panel comprising an alveolar structure (2) flanked on the one hand by a reflector (3) and on the other hand by an acoustically resistive layer (1, 1', 1") with two components, respectively, with acoustic properties and structural properties, characterised in that it comprises placing on a mould (M), with a shape appropriate to the panel
    fibres preimpregnated with a thermoplastic or thermosetting resin forming a layer with structural properties (1a, 1'a, 13, 15), said layer being formed by stretch forming, winding or hoop casing so that it has an open surface ratio of around 30% of the exposed surface,
    a layer with acoustic properties on top of the layer with structural properties, said layer with acoustic properties being formed of a microporous fabric with a thickness of around one tenth of that of the structural layer,
    the alveolar structure and the reflector with possibly the addition of an adhesive between components,
    at least one step of curing in an autoclave being implemented at the end of at least one of the above placing steps.
  2. A method according to claim 1, characterised in that the required porosity is conferred on said layer with structural properties (1'a) by the separation of the fibres (7, 8) at the time of weaving or when the fibres are wound or hoop cased.
  3. A method according to claim 1, characterised in that the required porosity is conferred on said layer with structural properties (1a) by piercing said layer after curing in an autoclave, the layer with acoustic properties (1b) being put in place thereafter.
  4. A method according to claims 1 and 2, characterised in that the layers with structural properties (1'a) and acoustic properties (1'b) are assembled with the possible interposing of a cross-linking adhesive (5) and subjected to curing in an autoclave, and then the whole is assembled on the structure with an alveolar core (2) and on the reflector (3), with the possible interposing of a cross-linking adhesive (6), and subjected to a further curing in an autoclave.
  5. A method according to one of claims 1 to 4, characterised in that the layer with the structural properties is formed of several layers of crossed fibres.
  6. A method according to claim 3, characterised in that the piercing holes (4) in the layer with structural properties (1a) have a diameter greater than the thickness of said layer and their external outlet (11) is splayed.
  7. A method according to claim 5, characterised in that a layer of crossed fibres is put in place on top of the layer with acoustic properties.
  8. A method according to one of claims 1 to 7, characterised in that the layer with acoustic properties (1b, 1'b, 1"b) is formed from a fabric of fibres chosen from the group comprising carbon, glass or "Kevlar" fibres, mineral or organic, natural or synthetic, dry or preimpregnated fibres.
  9. A method according to claim 4, characterised in that the cross-linking adhesive (6) interposed between the structure with an alveolar core (2) and the layer with acoustic properties (1b) is placed in line with the bottoms of the cells of said structure with an alveolar core (2).
EP00993660A 1999-12-24 2000-12-21 Method for making a sound reducing panel with resistive layer having structural property and resulting panel Expired - Lifetime EP1157372B1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
FR9916447A FR2803078B1 (en) 1999-12-24 1999-12-24 ACOUSTIC MITIGATION PANEL WITH RESISTIVE LAYER WITH STRUCTURAL PROPERTY AND METHOD FOR OBTAINING SAME
FR9916447 1999-12-24
PCT/FR2000/003648 WO2001048734A1 (en) 1999-12-24 2000-12-21 Method for making a sound reducing panel with resistive layer having structural property and resulting panel

Publications (2)

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EP1157372A1 EP1157372A1 (en) 2001-11-28
EP1157372B1 true EP1157372B1 (en) 2004-03-10

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EP00993660A Expired - Lifetime EP1157372B1 (en) 1999-12-24 2000-12-21 Method for making a sound reducing panel with resistive layer having structural property and resulting panel

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US (1) US20020157764A1 (en)
EP (1) EP1157372B1 (en)
CA (1) CA2365100C (en)
DE (1) DE60008861T2 (en)
ES (1) ES2217038T3 (en)
FR (1) FR2803078B1 (en)
WO (1) WO2001048734A1 (en)

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FR2821788B1 (en) * 2001-03-09 2004-04-02 Eads Airbus Sa METHOD FOR MANUFACTURING A PANEL WITH A SOUND ACOUSTIC LAYER LAYER AND ACOUSTIC PANEL THUS OBTAINED
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Publication number Publication date
DE60008861T2 (en) 2005-03-03
EP1157372A1 (en) 2001-11-28
ES2217038T3 (en) 2004-11-01
CA2365100A1 (en) 2001-07-05
US20020157764A1 (en) 2002-10-31
WO2001048734A1 (en) 2001-07-05
FR2803078B1 (en) 2002-07-26
CA2365100C (en) 2010-02-23
DE60008861D1 (en) 2004-04-15
FR2803078A1 (en) 2001-06-29

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