EP1747552A1 - Perforated skin for acoustic element, acoustic element and method for making same - Google Patents

Perforated skin for acoustic element, acoustic element and method for making same

Info

Publication number
EP1747552A1
EP1747552A1 EP05717420A EP05717420A EP1747552A1 EP 1747552 A1 EP1747552 A1 EP 1747552A1 EP 05717420 A EP05717420 A EP 05717420A EP 05717420 A EP05717420 A EP 05717420A EP 1747552 A1 EP1747552 A1 EP 1747552A1
Authority
EP
European Patent Office
Prior art keywords
fibers
unidirectional
skin
pattern
parallel
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP05717420A
Other languages
German (de)
French (fr)
Inventor
Jean-Pierre Jumel
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Safran Nacelles SAS
Original Assignee
Aircelle SA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Aircelle SA filed Critical Aircelle SA
Publication of EP1747552A1 publication Critical patent/EP1747552A1/en
Withdrawn legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/16—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/172—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using resonance effects
    • 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.]
    • Y10T428/24132—Structurally defined web or sheet [e.g., overall dimension, etc.] including grain, strips, or filamentary elements in different layers or components parallel
    • 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.]
    • Y10T428/24802—Discontinuous or differential coating, impregnation or bond [e.g., artwork, printing, retouched photograph, etc.]

Definitions

  • the present invention relates to a perforated skin for an acoustic element, an acoustic element incorporating such a skin, as well as the method for manufacturing said skin.
  • acoustic element is meant an element composed of an external skin / honeycomb / internal skin sandwich, said external skin being intended to be placed on the noise source side.
  • acoustic elements have been proposed formed from an outer skin / honeycomb / inner skin sandwich, in which the outer skin, intended to be located on the source of the noise, is perforated to allow the sound waves to penetrate.
  • to perforate and its declensions, is used in the proper sense of "to pierce right through”, as by punching, mechanical drilling by drill, erosion, laser, etc. and not in the sense of making holes in any way.
  • Composite skins are known, that is to say made of fibers and of resin, perforated to the extent of 10-15%, such a perforation rate sparing enough fiber so that the skin retains an acceptable degree of integrity. Also known are metal skins perforated at 30-40% without the degree of integrity becoming unacceptable, sufficient material remaining between the perforations.
  • Composites are lighter than metallic products and the question of weight is always an extremely important parameter when it comes to In aeronautics, it would be desirable to be able to have composite skins with a perforation rate similar to that which is possible in the case of metallic skins. Unfortunately, this is not possible by simply applying the known technique with either an increase in the density of the perforations, or an increase in the size of the perforations, or both, because, then, there are no longer enough unaffected fibers left. by the perforations and the structural hold of the skin is no longer ensured except by the resin matrix.
  • One solution is, not to perforate a web of pre-impregnated with resin fibers, once polymerized resin, but to arrange 'holes by walk the web, before polymerization, between the points of a "board fakir" , removing the tips from the board, after polymerization, resulting in as many holes in the sheet as there were tips.
  • the fibers follow a sinuous path around the holes instead of being cut by the creation of the holes, and the skin has a suitable integrity even with a high percentage of holes.
  • the invention provides a perforated skin for an acoustic element, consisting of at least one ply of substantially straight fibers associated with a resin and the perforations of which define a regular repeating pattern, characterized in that the perforations affect at least 25%, and preferably 30-40%, of the skin and in that, at least in a major part of the skin thus perforated, fibers of the said ply (s) are uninterrupted by the perforations.
  • the resin in question can be thermosetting as well as thermoplastic and the expression "associated with a resin” intends to cover both the case of a prepreg of fibers, as well as the juxtaposition of a resin film with a web. fibers, or any other technique known in the art. In one.
  • the fibers of at least one ply are substantially parallel to each other and oriented so that they follow a series of parallel passages free of perforations and, better, the water comprises at least two plies, in each of which at least some fibers are substantially parallel to one another, said parallel fibers of one of the plies being oriented so that they follow a first series of parallel corridors free of perforations and the parallel fibers of one other ply being oriented such that they follow a second series of parallel corridors free of perforations, the first series of corridors being intersecting in the second series of corridors.
  • the two plies in question can be independent or constitute, for example, the warp and weft threads of a fabric.
  • the regular repeating pattern of perforation can be any, but it will most often be a pattern in equilateral triangles or of a pattern in rectangles, and more specifically in squares.
  • the skin comprises at least one series of three plies, in each of which at least certain fibers are substantially parallel to each other, each ply having its parallel fibers oriented parallel to one of the sides of the equilateral triangle.
  • the skin comprises at least a series of four plies, in each of which at least certain fibers are substantially parallel to each other, two of the plies having their parallel fibers .oriented parallel to each of the pairs sides of the rectangle and the other two layers having their parallel fibers oriented parallel to each of the diagonals of the rectangle.
  • at least two of said layers belonging to a fabric comprising fibers in a first direction and fibers in a second direction intersecting the first, said 'fabric being oriented so that at least some fibers in the first direction and at least some fibers in the second direction follow corridors free of perforations.
  • the term “quasi-unidirectional fiber sheets” means fibers which are overwhelmingly (90-98%) unidirectional.
  • the fibers can be of any kind as long as they are able to withstand the conditions of use, for example, fibers of. carbon, glass fibers or Kevlar fibers.
  • the resin it will be chosen in particular as a function of the temperature to which the acoustic element in service will be subjected. Thus, an acoustic element equipping a gas outlet will be exposed to temperatures significantly higher than a element equipping an air inlet.
  • an epoxy resin or a bismaleimide resin (BMI) may be used, for example.
  • the invention also relates to an acoustic element incorporating the skin described above and a method of manufacturing said skin.
  • the acoustic element it is formed, as indicated above, of an external skin / honeycomb / internal skin sandwich and said external skin consists of the skin according to the invention.
  • said outer skin is secured, on its face opposite the honeycomb, to a metallic fabric
  • This metallic fabric is made up of fine metallic wires, generally made of stainless steel to avoid "galvanic" corrosion phenomena. The weaving of such a metallic fabric is very tight and can lead to a canvas or, more often, to a rep.
  • the process comprises, prior to the perforation step, a step of depositing said plies on a form for the purpose of shaping, is characterized in that: for deposition, there is, in a first direction, at at least one layer of unidirectional or quasi-unidirectional fibers associated with a resin, and in a second direction intersecting with the first, at least one second layer of unidirectional or quasi-unidirectional fibers associated with a resin, and for the perforation, a pattern of such geometry and such orientation with respect to said first and second directions that at least some fibers of the first and second plies remain unbroken.
  • a pattern is applied in equilateral triangles oriented so that the first direction corresponds to that of one side of an equilateral triangle of the pattern .
  • a first direction 0 °
  • at least a first layer of unidirectional or quasi-unidirectional fibers associated with a resin in a second direction, at + 90 ° relative to the first direction
  • at least a second layer of unidirectional or quasi-unidirectional fibers associated with a resin in a third and a fourth direction along, respectively, each of the diagonals of a rectangle of the future perforation pattern, at least a third and a fourth layer of unidirectional or quasi-unidirectional fibers associated with a resin, and for the perforation
  • a pattern is applied in oriented rectangles so that the third and fourth directions correspond to those.
  • the third and fourth directions will be respectively at + 45 ° and -45 ° relative to the first direction.
  • a second variant applicable to the pattern in squares we have in a first direction, at least a fabric layer associated with a resin and comprising warp threads and weft threads substantially perpendicular to each other, the direction of said warp threads being taken as the first direction; and ' in a second direction, at 45 ° relative to the first direction, at least one layer of fabric associated with a resin and comprising warp threads and weft threads substantially perpendicular to each other, the direction of said threads warp or weft being taken as second direction; and for the perforation, a pattern is applied in oriented squares so that the first direction corresponds to that of a diagonal of a square of the pattern.
  • - Figure 1 is a diagram showing, in enlarged section, an acoustic element to which the invention applies
  • - Figure 2 is a diagram showing the orientations of the fibers in the case of an equilateral triangle perforation pattern
  • - Figure 3 is a diagram showing the orientations of the fibers in the case of a rectangle perforation pattern.
  • the acoustic element comprises a perforated outer skin 1, a honeycomb layer 2 and an unperforated inner skin 3.
  • the skin 1 is perforated so that, taking account of the perforations blocked by la- union of said skin with the honeycomb, there are on average three perforations per cell of the honeycomb.
  • a metal fabric 4, such as a reps, 1 to 2/10 mm thick is glued to the perforated skin 1 to increase the acoustic damping effect. If we come to Figure 2, we see an arrangement of perforations PI, P2 and P3 in equilateral triangle a, b, c (or of perforations PI, P3, P4 in equilateral triangle a, c, d).
  • the perforations can have, for example, a diameter of 1.55 mm and the sides of the triangle have a length of 2.53 mm.
  • the invention provides for respecting a particular relationship between the orientation of the fibers and the geometry of the repeating perforation pattern. So, as we can see, one.
  • first layer NI of unidirectional fibers is arranged so that its fibers, such as FI, are parallel to the side, a, b of the triangle
  • a second layer N2 of unidirectional fibers is arranged so that its fibers F2 are parallel to side b, c of the triangle
  • a third layer N3 of unidirectional fibers is arranged so that its fibers F3 are parallel to side a, c of the triangle.
  • FIG. 3 shows an arrangement of perforations P5, P6, P7 and P8 in rectangle e, f, g, h, the directions XX 'and YY' corresponding to those of the diagonals of said rectangle. To avoid overloading the figure, it has been shown, to illustrate the layers, that the corresponding unbroken fiber corridors.
  • a first layer N4 of unidirectional fibers is arranged so that its fibers are parallel to the sides e, f and h, g of the rectangle
  • a second layer N5 of unidirectional fibers is arranged so that its fibers are parallel to the sides e, h and f, g of the rectangle
  • the production of the perforations P5-P8 will cut fibers in the sheets N4-N7, but there will remain lanes C4-C7 of fibers spared by this operation and the fibers thus uninterrupted will ensure sufficient integrity for the perforated skin.
  • the fibers of the web N4 and those of the web N5 could belong to a fabric of which they respectively constitute the warp and the weft.
  • the layers of N4-N7 fibers are independent of each other.
  • the fibers of two perpendicular layers, such as N4 and N5, or N6 and N7 can in fact be, on the one hand, the weft threads and, on the other hand, the warp threads of a fabric.
  • the skin may include more layers.
  • the skin will comprise six folds oriented at 0 ° / + 60 o / -60 o / -60 o / + 60 o / 0 °.
  • the invention relates to the production of perforated skins in which the perforations define a regular repeating pattern.
  • the patterns which have been specifically described and / or illustrated are only non-limiting examples. It could just as well be, for example, hexagonal, octagonal patterns, etc.

Abstract

The invention concerns a perforated skin consisting of at least one layer (N1-N3) of substantially rectilinear fibers associated with a resin and whereof the perforations define a regular repeated pattern (a, b, c), characterized in that the perforations affect at least 25 % of the skin and in that, at least in a major part of the perforated skin, fibers (C1-C3) of said layer(s) (N1-N3) are uninterrupted by the perforations (P1-P3).

Description

Peau perforée pour élément acoustique, élément acoustique et procédé de fabrication La présente invention a pour objet une peau perforée pour élément acoustique, un élément acoustique incorporant une telle peau, ainsi que le procédé de fabrication de ladite peau. Par élément acoustique, on entend un élément composé d'un sandwich peau externe/nid d'abeille/peau interne, ladite peau externe étant destinée à être placée côté source du bruit . Dans le domaine de l'aéronautique, par exemple, il est nécessaire de réduire autant que possible le bruit produit par le réacteur dans l'entrée d'air ou le système d' éjection. A cette fin, il a été proposé des éléments acoustiques formés d'un sandwich peau externe/nid d'abeille/peau interne, dans lesquels la peau externe, destinée à être située côté source du bruit, est perforée pour laisser les ondes sonores pénétrer dans le sandwich et y être amorties, la peau interne étant, elle, pleine. Dans le cadre de la présente description, le verbe "perforer", et ses déclinaisons, est utilisé au sens propre de "percer de part en part", comme par poinçonnage, perçage mécanique par foret, érosion, laser, etc. et non au sens de ménager des trous d'une manière quelconque. On connaît des peaux composites, c'est-à-dire constituées de fibres et de résine, perforées à hauteur de 10-15%, un tel taux de perforation épargnant suffisamment de fibres pour que la peau conserve un degré d'intégrité acceptable . On connaît également des peaux métalliques perforées à hauteur de 30-40% sans que le degré d'intégrité devienne inacceptable, suffisamment de matière restant entre les perforations . Les produits composites étant plus légers que les produits métalliques et la question du poids étant toujours un paramètre extrêmement important s 'agissant d'aéronautique, il serait souhaitable de pouvoir disposer de peaux composites ayant un taux de perforation semblable à celui qu'il est possible d'atteindre dans le cas de peaux métalliques. Malheureusement, cela n'est pas possible en appliquant simplement la technique connue avec soit une augmentation de la densité des perforations, soit une augmentation de la taille des perforations, soit les deux, car, alors, il ne reste plus suffisamment de fibres non affectées par les perforations et la tenue structurale de la peau n'est plus assurée que par la matrice de résine. Une solution est, non pas de perforer une nappe de fibres pré-imprégnées de résine, une fois la résine polymérisêe, mais de ménager' des trous en faisant cheminer la nappe, avant polymérisation, entre les pointes d'une "planche de fakir", le retrait des pointes de la planche, après polymérisation, résultant en autant de trous dans la nappe qu'il y avait de pointes. Dans ce cas, les fibres suivent un chemin sinueux autour des trous au lieu d'être coupées par la création des trous, et la peau a une intégrité convenable même avec un fort pourcentage de trous. Cependant, outre qu'elle est difficile à mettre enThe present invention relates to a perforated skin for an acoustic element, an acoustic element incorporating such a skin, as well as the method for manufacturing said skin. By acoustic element is meant an element composed of an external skin / honeycomb / internal skin sandwich, said external skin being intended to be placed on the noise source side. In the field of aeronautics, for example, it is necessary to reduce as much as possible the noise produced by the reactor in the air intake or the ejection system. To this end, acoustic elements have been proposed formed from an outer skin / honeycomb / inner skin sandwich, in which the outer skin, intended to be located on the source of the noise, is perforated to allow the sound waves to penetrate. in the sandwich and be amortized, the internal skin being full. In the context of the present description, the verb "to perforate", and its declensions, is used in the proper sense of "to pierce right through", as by punching, mechanical drilling by drill, erosion, laser, etc. and not in the sense of making holes in any way. Composite skins are known, that is to say made of fibers and of resin, perforated to the extent of 10-15%, such a perforation rate sparing enough fiber so that the skin retains an acceptable degree of integrity. Also known are metal skins perforated at 30-40% without the degree of integrity becoming unacceptable, sufficient material remaining between the perforations. Composites are lighter than metallic products and the question of weight is always an extremely important parameter when it comes to In aeronautics, it would be desirable to be able to have composite skins with a perforation rate similar to that which is possible in the case of metallic skins. Unfortunately, this is not possible by simply applying the known technique with either an increase in the density of the perforations, or an increase in the size of the perforations, or both, because, then, there are no longer enough unaffected fibers left. by the perforations and the structural hold of the skin is no longer ensured except by the resin matrix. One solution is, not to perforate a web of pre-impregnated with resin fibers, once polymerized resin, but to arrange 'holes by walk the web, before polymerization, between the points of a "board fakir" , removing the tips from the board, after polymerization, resulting in as many holes in the sheet as there were tips. In this case, the fibers follow a sinuous path around the holes instead of being cut by the creation of the holes, and the skin has a suitable integrity even with a high percentage of holes. However, in addition to being difficult to implement
- oeuvre ' lorsqu'il s'agit de réaliser- une peau de forme complexe à double courbure, cette solution n'est pas totalement satisfaisante en ce sens que les trous sont irréguliers avec des amas de résine aux points de divergence/confluence des fibres en amont/aval des trous . Une autre solution consiste à réaliser 1 ' élément acoustique sous la forme d'une cuvette qui constitue la peau interne et sur laquelle se collent -le noyau nid d'abeille et la peau externe perforée. La peau interne est alors le seul support des efforts et cette solution est peu efficace sur le plan structural. Il existe donc un besoin non satisfait en une nappe composite fortement perforée mais ayant une intégrité suffisante, besoin qui est d'autant plus pressant qu'une forte perforation permettrait d'adjoindre à la peau une toile métallique (dite "wiremesh") pour que l'atténuation acoustique soit optimale. A cette fin, l'invention apporte, une peau perforée pour élément acoustique, constituée d'au moins une nappe de fibres sensiblement rectilignes associées à une résine et dont les perforations définissent un motif répétitif régulier, caractérisée en ce que les perforations affectent au moins 25%, et de préférence 30-40%, de la peau et en ce que, au moins dans une partie majeure de la peau ainsi perforée, des fibres de la ou desdites nappes sont ininterrompues par les perforations. La résine dont il est question peut aussi bien être thermodurcissable que thermoplastique et l'expression "associées à une résine" entend couvrir aussi bien le cas d'une pré-imprégnation des fibres, que la juxtaposition d'un film de résine à une nappe de fibres, ou toute autre technique connue dans 1 ' art . Dans un. mode de réalisation préféré de l'invention, au moins certaines des fibres d'au moins une nappe sont sensiblement parallèles les unes aux autres et orientées de telle sorte qu'elles suivent une série de couloirs parallèles exempts de perforations et, mieux, la eau comprend au moins deux nappes, dans chacune desquelles au moins certaines fibres sont sensiblement parallèles les unes aux autres, lesdites fibres parallèles de l'une des nappes étant orientées de telle sorte qu'elles suivent une première série de couloirs parallèles exempts de perforations et les fibres parallèles de 1 ' autre nappe étant orientées de telle sorte qu'elles suivent une seconde série de couloirs parallèles exempts de perforations, la première série de couloirs étant sécante à la -seconde série de couloirs . Les deux nappes en question peuvent être indépendantes ou constituer, par exemple, les fils de chaîne et de trame d'un tissu. Le motif répétitif régulier de perforation peut être quelconque, mais il s'agira le plus souvent d'un motif en triangles équilatéraux ou d'un .motif en rectangles, et plus spécifiquement en carrés. Dans le cas d'un motif en triangles équilatéraux, la peau comprend au moins une série de trois nappes, dans chacune desquelles au moins certaines fibres sont sensiblement parallèles les unes aux autres, chaque nappe ayant ses fibres parallèles orientées parallèlement à l'un des côtés du triangle équilatéral. Dans le cas d'un motif en rectangles, la peau comprend au moins une série de quatre nappes, dans chacune desquelles au moins certaines fibres sont sensiblement parallèles les unes aux autres, deux des nappes ayant leurs fibres parallèles .orientées parallèlement à chacune des paires de côtés du rectangle et les deux autres nappes ayant leurs fibres parallèles orientées parallèlement à chacune des diagonales du rectangle . Dans une forme d'exécution possible, au moins deux desdites nappes appartiennent à un tissu comportant des fibres selon une première direction et des fibres selon une seconde direction sécante à la première, ledit' tissu étant orienté de telle sorte qu'au moins certaines fibres selon la première direction et au moins certaines fibres selon la seconde direction suivent des couloirs exempts de perforations. Par nappes de fibres quasi-unidirectionnelles, on entend des fibres qui sont en très grande majorité (90-98%) unidirectionnelles. Il s'agira par exemple de fibres de carbone renforcées par 2% de fibres de verre orientées perpendiculairement aux fibres de carbone. Les fibres peuvent être de nature quelconque pour autant qu'elles soient capables de résister aux conditions d'utilisation, par exemple, des fibres de. carbone, des fibres de verre ou des fibres de Kevlar. La résine, quant à elle, sera choisie notamment en fonction de la température à laquelle sera soumis l'élément acoustique en service. Ainsi, un élément acoustique équipant une sortie de gaz sera exposé à des températures nettement plus élevées qu'un élément équipant une entrée d'air. Selon le cas, on pourra utiliser une résine époxy ou une résine bismaléimide (BMI) , par exemple . Comme indiqué plus haut, l'invention • concerne également un élément acoustique incorporant la peau décrite ci-dessus et un procédé de fabrication de ladite peau. S ' agissant de l'élément acoustique, il est formé, comme indiqué plus haut, d'un sandwich peau externe/nid d'abeille/peau interne et ladite peau externe est constituée par la peau selon l'invention. De préférence, ladite peau externe est solidarisée, sur sa face opposée au nid d'abeille, à un tissu métallique- work ' when it comes to making - a skin of complex shape with double curvature, this solution is not completely satisfactory in the sense that the holes are irregular with lumps of resin at the points of divergence / confluence of the fibers upstream / downstream of the holes. Another solution consists in making the acoustic element in the form of a bowl which constitutes the internal skin and on which the honeycomb core and the perforated external skin stick. The internal skin is then the only support for efforts and this solution is not very effective on the structural level. There is therefore an unmet need for a highly perforated composite sheet but having sufficient integrity, a need which is all the more pressing as a strong perforation would make it possible to add to the skin a metallic fabric (called "wiremesh") so that the acoustic attenuation is optimal. To this end, the invention provides a perforated skin for an acoustic element, consisting of at least one ply of substantially straight fibers associated with a resin and the perforations of which define a regular repeating pattern, characterized in that the perforations affect at least 25%, and preferably 30-40%, of the skin and in that, at least in a major part of the skin thus perforated, fibers of the said ply (s) are uninterrupted by the perforations. The resin in question can be thermosetting as well as thermoplastic and the expression "associated with a resin" intends to cover both the case of a prepreg of fibers, as well as the juxtaposition of a resin film with a web. fibers, or any other technique known in the art. In one. preferred embodiment of the invention, at least some of the fibers of at least one ply are substantially parallel to each other and oriented so that they follow a series of parallel passages free of perforations and, better, the water comprises at least two plies, in each of which at least some fibers are substantially parallel to one another, said parallel fibers of one of the plies being oriented so that they follow a first series of parallel corridors free of perforations and the parallel fibers of one other ply being oriented such that they follow a second series of parallel corridors free of perforations, the first series of corridors being intersecting in the second series of corridors. The two plies in question can be independent or constitute, for example, the warp and weft threads of a fabric. The regular repeating pattern of perforation can be any, but it will most often be a pattern in equilateral triangles or of a pattern in rectangles, and more specifically in squares. In the case of a pattern in equilateral triangles, the skin comprises at least one series of three plies, in each of which at least certain fibers are substantially parallel to each other, each ply having its parallel fibers oriented parallel to one of the sides of the equilateral triangle. In the case of a rectangular pattern, the skin comprises at least a series of four plies, in each of which at least certain fibers are substantially parallel to each other, two of the plies having their parallel fibers .oriented parallel to each of the pairs sides of the rectangle and the other two layers having their parallel fibers oriented parallel to each of the diagonals of the rectangle. In a possible embodiment, at least two of said layers belonging to a fabric comprising fibers in a first direction and fibers in a second direction intersecting the first, said 'fabric being oriented so that at least some fibers in the first direction and at least some fibers in the second direction follow corridors free of perforations. The term “quasi-unidirectional fiber sheets” means fibers which are overwhelmingly (90-98%) unidirectional. It will, for example, be carbon fibers reinforced with 2% glass fibers oriented perpendicularly to the carbon fibers. The fibers can be of any kind as long as they are able to withstand the conditions of use, for example, fibers of. carbon, glass fibers or Kevlar fibers. As for the resin, it will be chosen in particular as a function of the temperature to which the acoustic element in service will be subjected. Thus, an acoustic element equipping a gas outlet will be exposed to temperatures significantly higher than a element equipping an air inlet. Depending on the case, an epoxy resin or a bismaleimide resin (BMI) may be used, for example. As indicated above, the invention also relates to an acoustic element incorporating the skin described above and a method of manufacturing said skin. As regards the acoustic element, it is formed, as indicated above, of an external skin / honeycomb / internal skin sandwich and said external skin consists of the skin according to the invention. Preferably, said outer skin is secured, on its face opposite the honeycomb, to a metallic fabric
- poreux de 1 à 2/10 mm d'épaisseur et ayant une résistance à la .traversée des gaz comprise entre 20 et 40 Pa.s/m (rayls) . Ce tissu métallique est constitué par des fils métalliques fins, en général en acier inoxydable pour éviter des phénomènes de corrosion "galvanique". Le tissage d'un tel tissu métallique est très serré et peut déboucher sur une toile ou, plus souvent, sur un reps. S ' agissant du procédé, il comprend, préalablement à l'étape de perforation, une étape de dépôt desdites nappes sur une forme à des fins de conformation, est caractérisé en ce que : pour le dépôt, on dispose selon une première direction, au moins une nappe de fibres unidirectionnelles ou quasi-unidirectionnelles associées à une résine, et selon une deuxième direction sécante à la première, au moins une deuxième nappe de fibres unidirectionnelles ou quasi-unidirectionnelles associées à une résine, et pour la perforation, on applique un motif d'une géométrie telle et d'une orientation telle par rapport auxdites première et deuxième directions qu'au moins certaines fibres des première et deuxième nappes demeurent ininterrompues . S'il s'agit de fabriquer une peau ayant un motif de perforations en triangle équilatéral, pour le dépôt, on dispose selon une première direction, 0°, au moins une première nappe de fibres unidirectionnelles ou quasi-unidirectionnelles associées à une résine, selon une deuxième direction, à +60° par rapport à la première direction, au moins une deuxième nappe de fibres unidirectionnelles ou quasi-unidirectionnelles associées à une résine, selon une troisième direction, à -60° par rapport à la première direction, au moins une troisième nappe de fibres unidirectionnelles ou quasi-unidirectionnelles associées à une résine, et pour la perforation, on applique un motif en triangles équilatéraux orienté de telle sorte que la première direction correspond à celle d'un côté d'un triangle équilatéral du motif. S'il s'agit de fabriquer une peau ayant un motif de perforations en rectangle, selon une première variante pour le dépôt, on dispose selon une première direction, 0°, au moins une première nappe de fibres unidirectionnelles ou quasi-unidirectionnelles associées à une résine, selon une deuxième direction, à +90° par rapport à la première direction, au moins une deuxième nappe de fibres unidirectionnelles ou quasi-unidirectionnelles associées à une résine, et selon une troisième et une quatrième directions suivant, respectivement, chacune des diagonales d'un rectangle du futur motif de perforation, au moins une troisième et une quatrième nappes de fibres unidirectionnelles ou quasi-unidirectionnelles associées à une résine, et pour la perforation, on applique un motif en rectangles orientés de telle sorte que les troisième et quatrième directions correspondent à celles.' des diagonales d'un rectangle du motif. Un cas particulier de rectangle est bien évidemment le carré. Dans ce cas, les troisième et quatrième directions seront respectivement à +45° et-45° par rapport à la première direction Selon une seconde variante applicable au cas du motif en carrés : pour le dépôt, on dispose selon une première direction, au moins une couche tissu associé à une résine et comportant des fils de chaîne et des fils de trame sensiblement perpendiculaires les uns aux autres, la direction desdits fils de chaîne étant prise comme première direction ; et ' selon une deuxième -direction, à 45° par rapport à la première direction, au moins une couche de tissu associé à une résine et comportant des fils de chaîne et des fils de trame sensiblement perpendiculaires les uns aux autres, la direction desdits fils de chaîne ou de trame étant prise comme deuxième- direction ; et pour la perforation, on applique un motif en carrés orientés de telle sorte que la première direction correspond à celle d'une diagonale d'un carré du motif. Dans tous les cas, lors du dépôt, on prend soin d'orienter au moins certaines des fibres qui resteront ininterrompues après perforation dans une direction correspondant à une direction de contrainte maximale de l'élément, une fois en service. Bien entendu, le dépôt sur des formes non planes fait que les fibres n'ont pas une orientation constante et il y a lieu, en conséquence, de .programmer convenablement la machine de perforation pour que l'opération tienne en permanence compte des changements d'orientation des fibres. L'invention sera mieux comprise à la lecture de la description suivante faite en référence aux dessins annexés, dans lesquels : - la figure 1 est un schéma représentant, en coupe agrandie, un élément acoustique auquel s'applique 1 ' invention ; - la figure 2 est un schéma montrant les orientations des fibres dans le cas d'un motif de perforation en triangle équilatéral, et - la figure 3 est un schéma montrant les orientations des fibres dans le cas d'un motif de perforation en rectangle . Comme il ressort de la figure 1, l'élément acoustique comporte une peau externe perforée 1, une couche nid d'abeille 2 et une peau interne non perforée 3. La peau 1 est perforée de telle sorte que, compte tenu des perforations bouchées par la- réunion de ladite peau avec le nid d'abeille, il y ait en moyenne trois perforations par alvéole du nid d'abeille. Une toile métallique 4, tel qu'un reps, de 1 à 2/10 mm d'épaisseur est collée à la peau perforée 1 pour augmenter l'effet d'amortissement acoustique . Si l'on en vient à la figure 2, on voit une disposition, de perforations PI, P2 et P3 en triangle équilatéral a,b,c (ou de perforations PI, P3 , P4 en triangle équilatéral a,c,d). Les perforations peuvent avoir, par exemple, un diamètre de 1,55 mm et les côtés du triangle avoir une longueur de 2,53 mm. On comprend que, pour une telle densité de perforation, des fibres distribuées de manière aléatoire seraient inévitablement coupées pour la plupart et qu'il en résulterait une intégrité insuffisante de la peau. Pour éviter qu'il en soit ainsi, l'invention prévoit de respecter une relation particulière entre l'orientation des fibres et la géométrie du motif répétitif de perforation. Ainsi, comme on le voit, une. première nappe NI de fibres unidirectionnelles est disposée de telle sorte que ses fibres, telles que FI, soient parallèles au côté, a,b du triangle, une seconde nappe N2 de fibres unidirectionnelles est disposée de telle sorte que ses fibres F2 soient parallèles au côté b,c du triangle, et une troisième nappe N3 de fibres unidirectionnelles est disposée de telle sorte que ses fibres F3 soient parallèles au côté a,c du triangle. Naturellement, la réalisation des perforations PI, P2 et P3 coupera des fibres dans les nappes NI, N2 et N3 , mais il demeurera des couloirs Cl, C2 et C3 , de largeur z, de fibres épargnées par cette opération et les fibres ainsi ininterrompues assureront une intégrité suffisante à la peau perforée. La figure 3 montre une disposition de perforations P5, P6, P7 et P8 en rectangle e,f,g,h, les directions X-X' et YY' correspondant à celles des diagonales dudit rectangle. Pour ne pas surcharger la figure, il n'a été représenté, pour illustrer les nappes, que les couloirs de fibres ininterrompues correspondants. Comme on le voit, une première nappe N4 de fibres unidirectionnelles est disposée de telle sorte que ses fibres soient parallèles aux côtés e,f et h, g du rectangle, une seconde nappe N5 de fibres unidirectionnelles est disposée de telle sorte que ses fibres soient parallèles aux côtés e,h et f,g du rectangle, une troisième nappe N6 de fibres unidirectionnelles est disposée de telle sorte que ses fibres soient parallèles à la diagonale e,g (= Y, Y') et une quatrième nappe N7 de fibres unidirectionnelles est disposée de telle sorte que ses fibres soient parallèles à la diagonale f,h (= X,X.') . Là encore, la réalisation des perforations P5-P8 coupera des fibres dans les nappes N4-N7, mais il demeurera des couloirs C4-C7 de fibres épargnées par cette opération et les fibres ainsi ininterrompues assureront une intégrité suffisante à la peau perforée. On comprend que les fibres de la nappe N4 et celles de la nappe N5 pourraient appartenir à un tissu dont elles constitueraient respectivement la chaîne et la trame. Dans une première variante d'exécution, les nappes de fibres N4-N7 sont indépendantes les unes des autres. Dans une seconde variante, les fibres de deux- nappes perpendiculaires, telles que N4 et N5 , ou N6 et N7 , peuvent en fait être, d'une part, les fils de trame et, d'autre part., les fils de chaîne d'un tissu. Dans la description qui précède, on s'est référé à l'usage de trois nappes de fibres à propos du motif en triangles équilatéraux et à quatre nappes de fibres à propos du motif en rectangles, mais la peau peut comporter davantage de nappes. Ainsi, dans une forme d'exécution préférée de perforations à motif en triangles équilatéraux, la peau comportera six plis orientés à 0°/+60o/-60o/-60o/+60o/0° . En outre, comme indiqué plus haut, l'invention concerne la réalisation de peaux perforées dans lesquelles les perforations définissent un motif répétitif régulier. Les motifs qui ont été spécifiquement décrits et/ou illustrés ne sont que des exemples non limitatifs. Il pourrait tout aussi bien s'agir, par exemple, de motifs hexagonaux, octogonaux, etc. - porous from 1 to 2/10 mm thick and having a resistance to gas crossing between 20 and 40 Pa.s / m (rayls). This metallic fabric is made up of fine metallic wires, generally made of stainless steel to avoid "galvanic" corrosion phenomena. The weaving of such a metallic fabric is very tight and can lead to a canvas or, more often, to a rep. As regards the process, it comprises, prior to the perforation step, a step of depositing said plies on a form for the purpose of shaping, is characterized in that: for deposition, there is, in a first direction, at at least one layer of unidirectional or quasi-unidirectional fibers associated with a resin, and in a second direction intersecting with the first, at least one second layer of unidirectional or quasi-unidirectional fibers associated with a resin, and for the perforation, a pattern of such geometry and such orientation with respect to said first and second directions that at least some fibers of the first and second plies remain unbroken. If it is a question of manufacturing a skin having a pattern of perforations in an equilateral triangle, for the deposition, there is available in a first direction, 0 °, at least a first layer of unidirectional or almost unidirectional fibers associated with a resin, in a second direction, at + 60 ° relative to the first direction, at least one second layer of unidirectional or quasi-unidirectional fibers associated with a resin, in a third direction, at -60 ° relative to the first direction, at minus a third layer of unidirectional or quasi-unidirectional fibers associated with a resin, and for the perforation, a pattern is applied in equilateral triangles oriented so that the first direction corresponds to that of one side of an equilateral triangle of the pattern . If it is a question of manufacturing a skin having a rectangle perforation pattern, according to a first variant for deposition, there is available in a first direction, 0 °, at least a first layer of unidirectional or quasi-unidirectional fibers associated with a resin, in a second direction, at + 90 ° relative to the first direction, at least a second layer of unidirectional or quasi-unidirectional fibers associated with a resin, and in a third and a fourth direction along, respectively, each of the diagonals of a rectangle of the future perforation pattern, at least a third and a fourth layer of unidirectional or quasi-unidirectional fibers associated with a resin, and for the perforation, a pattern is applied in oriented rectangles so that the third and fourth directions correspond to those. ' of the diagonals of a rectangle of the pattern. A special case of a rectangle is obviously the square. In this case, the third and fourth directions will be respectively at + 45 ° and -45 ° relative to the first direction. According to a second variant applicable to the pattern in squares: for the deposit, we have in a first direction, at least a fabric layer associated with a resin and comprising warp threads and weft threads substantially perpendicular to each other, the direction of said warp threads being taken as the first direction; and ' in a second direction, at 45 ° relative to the first direction, at least one layer of fabric associated with a resin and comprising warp threads and weft threads substantially perpendicular to each other, the direction of said threads warp or weft being taken as second direction; and for the perforation, a pattern is applied in oriented squares so that the first direction corresponds to that of a diagonal of a square of the pattern. In all cases, during deposition, care is taken to orient at least some of the fibers which will remain uninterrupted after perforation in a direction corresponding to a direction of maximum stress of the element, once in service. Of course, the deposition on non-planar shapes means that the fibers do not have a constant orientation and it is therefore necessary to program the perforating machine appropriately so that the operation constantly takes account of changes in fiber orientation. The invention will be better understood on reading the following description made with reference to the accompanying drawings, in which: - Figure 1 is a diagram showing, in enlarged section, an acoustic element to which the invention applies; - Figure 2 is a diagram showing the orientations of the fibers in the case of an equilateral triangle perforation pattern, and - Figure 3 is a diagram showing the orientations of the fibers in the case of a rectangle perforation pattern. As can be seen from FIG. 1, the acoustic element comprises a perforated outer skin 1, a honeycomb layer 2 and an unperforated inner skin 3. The skin 1 is perforated so that, taking account of the perforations blocked by la- union of said skin with the honeycomb, there are on average three perforations per cell of the honeycomb. A metal fabric 4, such as a reps, 1 to 2/10 mm thick is glued to the perforated skin 1 to increase the acoustic damping effect. If we come to Figure 2, we see an arrangement of perforations PI, P2 and P3 in equilateral triangle a, b, c (or of perforations PI, P3, P4 in equilateral triangle a, c, d). The perforations can have, for example, a diameter of 1.55 mm and the sides of the triangle have a length of 2.53 mm. It is understood that, for such a density of perforation, fibers distributed randomly would inevitably be cut for the most part and that this would result in insufficient integrity of the skin. To avoid this being so, the invention provides for respecting a particular relationship between the orientation of the fibers and the geometry of the repeating perforation pattern. So, as we can see, one. first layer NI of unidirectional fibers is arranged so that its fibers, such as FI, are parallel to the side, a, b of the triangle, a second layer N2 of unidirectional fibers is arranged so that its fibers F2 are parallel to side b, c of the triangle, and a third layer N3 of unidirectional fibers is arranged so that its fibers F3 are parallel to side a, c of the triangle. Naturally, the realization of the perforations PI, P2 and P3 will cut fibers in the sheets NI, N2 and N3, but there will remain corridors Cl, C2 and C3, of width z, of fibers spared by this operation and the fibers thus uninterrupted will ensure sufficient integrity to the perforated skin. FIG. 3 shows an arrangement of perforations P5, P6, P7 and P8 in rectangle e, f, g, h, the directions XX 'and YY' corresponding to those of the diagonals of said rectangle. To avoid overloading the figure, it has been shown, to illustrate the layers, that the corresponding unbroken fiber corridors. As can be seen, a first layer N4 of unidirectional fibers is arranged so that its fibers are parallel to the sides e, f and h, g of the rectangle, a second layer N5 of unidirectional fibers is arranged so that its fibers are parallel to the sides e, h and f, g of the rectangle, a third layer N6 of unidirectional fibers is arranged so that its fibers are parallel to the diagonal e, g (= Y, Y ') and a fourth layer N7 of fibers unidirectional is arranged so that its fibers are parallel to the diagonal f, h (= X, X '.). Here again, the production of the perforations P5-P8 will cut fibers in the sheets N4-N7, but there will remain lanes C4-C7 of fibers spared by this operation and the fibers thus uninterrupted will ensure sufficient integrity for the perforated skin. It is understood that the fibers of the web N4 and those of the web N5 could belong to a fabric of which they respectively constitute the warp and the weft. In a first variant, the layers of N4-N7 fibers are independent of each other. In a second variant, the fibers of two perpendicular layers, such as N4 and N5, or N6 and N7, can in fact be, on the one hand, the weft threads and, on the other hand, the warp threads of a fabric. In the foregoing description, reference has been made to the use of three layers of fibers in connection with the pattern in equilateral triangles and to four layers of fibers in connection with the pattern in rectangles, but the skin may include more layers. Thus, in a preferred embodiment of perforations with a pattern in equilateral triangles, the skin will comprise six folds oriented at 0 ° / + 60 o / -60 o / -60 o / + 60 o / 0 °. In addition, as indicated above, the invention relates to the production of perforated skins in which the perforations define a regular repeating pattern. The patterns which have been specifically described and / or illustrated are only non-limiting examples. It could just as well be, for example, hexagonal, octagonal patterns, etc.

Claims

REVENDICATIONS 1. Peau perforée pour élément acoustique, constituée d'au moins une nappe (N1-N3 ; N4-N7) de fibres sensiblement rectilignes associées à une résine et dont les perforations définissent un motif répétitif régulier (a,b,c ; e,f,g,h), caractérisée en ce que les perforations (P1-P3 ; P5-P8) affectent au moins 25% de la peau et en ce que, au moins dans une partie majeure de la peau ainsi perforée, des fibres (C1-C3 ; C4-C7) de la ou desdites nappes (N1-N3 ; N4-N7) ' sont ininterrompues par les perforations (P1-P3 ; P5-P8) . CLAIMS 1. Perforated skin for acoustic element, consisting of at least one ply (N1-N3; N4-N7) of substantially straight fibers associated with a resin and the perforations of which define a regular repeating pattern (a, b, c; e , f, g, h), characterized in that the perforations (P1-P3; P5-P8) affect at least 25% of the skin and in that, at least in a major part of the skin thus perforated, fibers (C1-C3; C4-C7) of said ply (s) (N1-N3; N4-N7) 'are uninterrupted by the perforations (P1-P3; P5-P8).
2. Peau selon la revendication 1, caractérisée en ce qu'elle est perforée à 30-40%2. Skin according to claim 1, characterized in that it is 30-40% perforated
3. Peau selon la revendication 1 ou 2 , caractérisée en ce qu'au moins certaines des fibres d'au moins une nappe (N1-N3 ; N4-N7) sont sensiblement parallèles les unes aux autres et orientées de telle sorte qu'elles suivent une série de couloirs (Cl ou C2 ou C3 ; C4 ou C5 ou Cδ ou C7) parallèles exempts de perforations . 3. Skin according to claim 1 or 2, characterized in that at least some of the fibers of at least one ply (N1-N3; N4-N7) are substantially parallel to each other and oriented so that they follow a series of parallel (C1 or C2 or C3; C4 or C5 or Cδ or C7) corridors free of perforations.
4. Peau selon l'une quelconque des revendications 1 à 3, caractérisée en ce qu'elle comprend au moins deux nappes, dans chacune desquelles au moins certaines fibres sont sensiblement parallèles les unes aux autres, lesdites fibres parallèles de l'une des nappes étant orientées de telle sorte qu'elles suivent une première série de couloirs (Cl ; C4) parallèles exempts de perforations et les fibres parallèles de l'autre nappe étant orientées de telle sorte qu'elles suivent une seconde série de couloirs (C2 ou C3 ;4. Skin according to any one of claims 1 to 3, characterized in that it comprises at least two plies, in each of which at least some fibers are substantially parallel to each other, said fibers parallel to one of the plies being oriented so that they follow a first series of parallel lanes (Cl; C4) free of perforations and the parallel fibers of the other ply being oriented so that they follow a second series of lanes (C2 or C3 ;
C5 ou C6 ou C7) parallèles exempts de perforations, la première série de couloirs (Cl ; C4) étant sécante à la seconde série de couloirs (C2 ou C3 ; C5 ou C6 ou C7) . C5 or C6 or C7) parallel without perforations, the first series of lanes (Cl; C4) intersecting the second series of lanes (C2 or C3; C5 or C6 or C7).
5. Peau selon l'une quelconque des revendications 1 à 4 dans laquelle le motif répétitif régulier est un triangle équilatéral (a,b,c), caractérisée en ce qu'elle comprend au moins une série de trois nappes (N1-N3), dans chacune desquelles au moins certaines fibres sont sensiblement parallèles les unes aux autres, chaque happe ayant ses fibres parallèles orientées parallèlement à l'un des côtés (a-b, b-c, c-a) du triangle équilatéral. 5. Skin according to any one of claims 1 to 4 in which the regular repeating pattern is an equilateral triangle (a, b, c), characterized in that it comprises at least one series of three layers (N1-N3) , in each of which at least some fibers are substantially parallel to each other, each snap having its parallel fibers oriented parallel to one of the sides (ab, bc, ca) of the equilateral triangle.
6. Peau selon l'une quelconque des revendications 1 à 4, dans laquelle le motif répétitif régulier est un rectangle (e,f,g,h,), caractérisée en ce qu'elle comprend au moins une série de quatre nappes (N4-N7) , dans chacune desquelles au moins certaines fibres sont sensiblement parallèles les unes aux autres, deux des nappes (N4,N5) ayant leurs fibres parallèles orientées parallèlement à chacune des paires de côtés (e-f et g-h, e-h et f-g) du rectangle et les deux autres nappes (N6, N7) ayant leurs fibres parallèles orientées parallèlement à chacune des diagonales (e-g, f-'h) du rectangle. 6. Skin according to any one of claims 1 to 4, in which the regular repeating pattern is a rectangle (e, f, g, h,), characterized in that it comprises at least one series of four layers (N4 -N7), in each of which at least certain fibers are substantially parallel to each other, two of the sheets (N4, N5) having their parallel fibers oriented parallel to each of the pairs of sides (ef and gh, eh and fg) of the rectangle and the other two layers (N6, N7) having their parallel fibers oriented parallel to each of the diagonals (eg, f-'h) of the rectangle.
7. Peau selon l'une quelconque des revendications 1 à 6, caractérisée en ce que la ou lesdites nappes sont des nappes de fibres unidirectionnelles ou quasi- unidirectionnelles. 7. Skin according to any one of claims 1 to 6, characterized in that the said ply (s) are plies of unidirectional or quasi-unidirectional fibers.
8. Peau selon l'une quelconque des revendications l à 6, caractérisée en ce qu'au moins deux desdites nappes (N4,N5) appartiennent à un tissu comportant des fibres selon ' une première direction et des fibres selon une seconde direction sécante à la première, ledit tissu étant orienté de telle sorte qu'au moins certaines fibres selon la première direction et au moins certaines fibres selon la seconde direction suivent des couloirs (C4, C5) exempts de perforations . 8. Skin according to any one of claims l to 6, characterized in that at least two of said plies (N4, N5) belong to a fabric comprising fibers in ' a first direction and fibers in a second secant direction to the first, said fabric being oriented so that at least some fibers in the first direction and at least some fibers in the second direction follow corridors (C4, C5) free of perforations.
9. Elément acoustique formé d'un sandwich peau externe (1) /nid d'abeille (2)/peau interne (3),. ladite peau externe étant destinée à être placée côté source du bruit, caractérisée en ce que ladite peau externe (1) est une peau selon l'une quelconque des revendications 1 à 8. 9. Acoustic element formed by an outer skin (1) / honeycomb (2) / inner skin (3) sandwich. said external skin being intended to be placed on the noise source side, characterized in that said external skin (1) is a skin according to any one of claims 1 to 8.
10. Elément acoustique selon la revendication 9, caractérisé en ce que ladite peau externe (1) est solidarisée, sur sa face opposée au nid d'abeille (2), à un tissu métallique (4) poreux de 1 à 2/10 mm d'épaisseur et ayant une résistance à la traversée des gaz comprise entre 20 et 40 Pa.s/m. 10. Acoustic element according to claim 9, characterized in that said outer skin (1) is secured, on its face opposite to the honeycomb (2), to a metallic fabric (4) porous from 1 to 2/10 mm thick and having a resistance to gas passage between 20 and 40 Pa.s / m.
11. Procédé de fabrication d'une peau- selon la revendication 4, qui comprend, préalablement à l'étape de perforation, une étape de dépôt desdites nappes sur une forme à des fins de conformation, caractérisé en ce que : pour le dépôt, on dispose selon une première direction, au moins une nappe (NI ; N4) de fibres unidirectionnelles ou quasi- unidirectionnelles associées à une résine, et selon une deuxième direction sécante à la première, au moins une deuxième nappe (N2 ou N3 ; N5 ou N6 ou N7) de fibres unidirectionnelles ou quasi-unidirectionnelles associées à une résine, et pour la perforation, on applique un motif d'une géométrie telle et d'une orientation telle par rapport auxdites première et deuxième directions qu'au moins certaines fibres [Cl et (C2 ou C3) ; C4 et (C5 ou C6 ou C7) ] des première et deuxième nappes demeurent ininterrompues . 11. A method of manufacturing a skin according to claim 4, which comprises, prior to the perforation step, a step of depositing said plies on a form for the purpose of shaping, characterized in that: for deposition, at least one layer (NI; N4) of unidirectional or almost unidirectional fibers associated with a resin is arranged in a first direction (NI; N4) and in a second direction intersecting with the first, at least one second layer (N2 or N3; N5 or N6 or N7) of unidirectional or quasi-unidirectional fibers associated with a resin, and for the perforation, a pattern of such geometry and such orientation with respect to said first and second directions is applied that at least certain fibers [ Cl and (C2 or C3); C4 and (C5 or C6 or C7)] of the first and second layers remain uninterrupted.
12. Procédé de fabrication selon la revendication 11 d'une peau selon la revendication 5, caractérisé en ce que: pour le dépôt, on dispose selon une première direction, 0°, au moins une première nappe (NI) de fibres unidirectionnelles ou quasi-unidirectionnelles associées à une résine, selon une deuxième direction, à +60° par rapport à la première direction, au moins une deuxième nappe (N2) de fibres unidirectionnelles ou quasi-unidirectionnelles associées à une résine, et selon une troisième direction, à -60° par rapport à la première direction, au moins une troisième nappe (N3) de fibres unidirectionnelles ou quasi-unidirectionnelles associées à une résine, et pour la perforation, on applique un motif en triangles équilatéraux (a,b,c) orientés de telle sorte que la première direction correspond à celle d'un côté (a-b) d'un triangle équilatéral du motif. 12. The manufacturing method according to claim 11 of a skin according to claim 5, characterized in that: for deposition, there is available in a first direction, 0 °, at least a first sheet (NI) of unidirectional or quasi fibers -unidirectional associated with a resin, in a second direction, at + 60 ° relative to the first direction, at least one second layer (N2) of unidirectional or quasi-unidirectional fibers associated with a resin, and in a third direction, -60 ° relative to the first direction, at least a third layer (N3) of unidirectional or quasi-unidirectional fibers associated with a resin, and for the perforation, a pattern is applied in equilateral triangles (a, b, c) oriented so that the first direction corresponds to that of a side (ab) of an equilateral triangle of the pattern.
13. Procédé de fabrication selon la revendication 11 d'une peau selon la revendication 6, caractérisé en ce qu'il consiste : pour le dépôt, on dispose selon une première direction, 0°, au moins une première "nappe (N4) de fibres unidirectionnelles ou quasi-unidirectionnelles associées à une résine, selon une deuxième direction, à +90° par rapport à la première direction, au moins une deuxième nappe (N5) de fibres unidirectionnelles ou quasi-unidirectionnelles associées à une résine, selon une troisième et une ' quatrième directions (X-X1, Y, Y') suivant, respectivement, chacune des diagonales d'un rectangle du futur motif de perforation, au moins une troisième et une quatrième nappes (N6,N7) de fibres unidirectionnelles ou quasi-unidirectionnelles associées à une résine, "et pour la perforation, on applique un motif en rectangles (e,f,g,h), orientés de telle sorte que les troisième et quatrième directions (X-X', Y, Y') correspondent à celles des diagonales (e-g, f-h) d'un rectangle du motif. 13. The manufacturing method according to claim 11 of a skin according to claim 6, characterized in that it consists: for the deposition, in a first direction, 0 °, there is at least a first " sheet (N4) of unidirectional or quasi-unidirectional fibers associated with a resin, in a second direction, at + 90 ° relative to the first direction, at least a second ply (N5) of unidirectional or quasi-unidirectional fibers associated with a resin, according to a third and a ' fourth direction (XX 1 , Y, Y') following, respectively, each of the diagonals of a rectangle of the future perforation pattern, at least a third and a fourth ply (N6, N7) of unidirectional or quasi-fibers unidirectional associated with a resin, " and for the perforation, we apply a pattern in rectangles (e, f, g, h), oriented so that the third and fourth directions (X-X ', Y, Y') correspond to those of the diago nales (eg, fh) of a rectangle of the pattern.
14. Procédé de fabrication selon la revendication 11 d'une peau selon la revendication 6 dans le cas où le motif en rectangles est un motif en carrés, caractérisé - en ce qu'il consiste : pour le dépôt, on dispose selon une première direction, au moins une couche tissu associé à une résine et comportant des fils de chaîne et des fils de trame sensiblement perpendiculaires les uns aux autres, la direction desdits fils de chaîne étant prise comme première direction ; et selon une deuxième direction, à 45° par rapport à la première direction, au moins une couche de tissu associé à une résine et comportant des fils de chaîne et des fils de trame sensiblement perpendiculaires les uns aux autres, la direction desdits fils de chaîne ou de trame étant prise comme deuxième direction ; et pour la perforation, on applique un motif en carrés orientés de telle sorte que la première direction correspond à celle d'une diagonale d'un carré du motif. 14. The manufacturing method according to claim 11 of a skin according to claim 6 in the case where the rectangular pattern is a square pattern, characterized - in that it consists: for the deposit, it is arranged in a first direction , at least one fabric layer associated with a resin and comprising warp threads and weft threads substantially perpendicular to each other, the direction of said warp threads being taken as the first direction; and in a second direction, at 45 ° relative to the first direction, at least one layer of fabric associated with a resin and comprising warp threads and weft threads substantially perpendicular to each other, the direction of said warp or weft threads being taken as a second direction; and for the perforation, a pattern is applied in oriented squares so that the first direction corresponds to that of a diagonal of a square of the pattern.
15. Procédé de fabrication d'une peau selon l'une quelconque des revendications 1 à 8, caractérisé en ce qu'il consiste, lors du dépôt, à orienter au moins certaines des fibres qui resteront ininterrompues après perforation (C1-C3 ; C4-C7) dans une direction correspondant à une direction de contrainte maximale de l'élément, une fois en service. 15. A method of manufacturing a skin according to any one of claims 1 to 8, characterized in that it consists, during deposition, in orienting at least some of the fibers which will remain uninterrupted after perforation (C1-C3; C4 -C7) in a direction corresponding to a direction of maximum stress of the element, once in service.
EP05717420A 2004-01-15 2005-01-14 Perforated skin for acoustic element, acoustic element and method for making same Withdrawn EP1747552A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR0400334A FR2865309B1 (en) 2004-01-15 2004-01-15 PERFORATED SKIN FOR ACOUSTIC ELEMENT, ACOUSTIC ELEMENT AND METHOD OF MANUFACTURE
PCT/FR2005/000085 WO2005073956A1 (en) 2004-01-15 2005-01-14 Perforated skin for acoustic element, acoustic element and method for making same

Publications (1)

Publication Number Publication Date
EP1747552A1 true EP1747552A1 (en) 2007-01-31

Family

ID=34707861

Family Applications (1)

Application Number Title Priority Date Filing Date
EP05717420A Withdrawn EP1747552A1 (en) 2004-01-15 2005-01-14 Perforated skin for acoustic element, acoustic element and method for making same

Country Status (5)

Country Link
US (1) US20080118699A1 (en)
EP (1) EP1747552A1 (en)
CA (1) CA2552920A1 (en)
FR (1) FR2865309B1 (en)
WO (1) WO2005073956A1 (en)

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2912833B1 (en) * 2007-02-20 2009-08-21 Airbus France Sas PANEL FOR ACOUSTIC TREATMENT
JP2009062977A (en) * 2007-08-15 2009-03-26 Rohr Inc Linear acoustic liner
CN102089801B (en) * 2008-05-22 2013-05-29 3M创新有限公司 Multilayer sound absorbing structure comprising mesh layer
GB201301702D0 (en) 2013-01-31 2013-03-20 Rolls Royce Plc Exhaust cone
DE102013226792A1 (en) * 2013-12-19 2015-06-25 Volkswagen Aktiengesellschaft A method for acoustic and / or fluidic perforation of a component made of a fiber composite plastic

Family Cites Families (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3767499A (en) * 1971-09-09 1973-10-23 M Koss Method of making porous laminate
US3960236A (en) * 1974-06-17 1976-06-01 Mcdonnell Douglas Corporation Lock core panel
FR2300384A1 (en) * 1975-02-07 1976-09-03 Lockheed Aircraft Corp Sound absorbing panel effective in two frequency domains - combines action of Helm holtz resonator with that of laminar honeycomb absorber
FR2480741A1 (en) * 1980-04-18 1981-10-23 Aerospatiale POROUS LAYER FOR COMPOSITE STRUCTURE FOR ABSORPTION OF SOUND ENERGY AND METHOD OF MANUFACTURING THE SAME
US4600619A (en) * 1984-12-31 1986-07-15 The Boeing Company Continuously wound filament structure for use in noise attenuation element
FR2767411B1 (en) * 1997-08-13 2001-11-16 Aerospatiale ACOUSTICALLY RESISTIVE LAYER, METHOD FOR MANUFACTURING THE SAME AND ACOUSTICALLY ABSORBING PANEL PROVIDED WITH AT LEAST ONE SUCH LAYER
SE525812C2 (en) * 2002-06-12 2005-05-03 Saab Ab Acoustic lining, use of a lining and ways of producing an acoustic lining

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO2005073956A1 *

Also Published As

Publication number Publication date
FR2865309A1 (en) 2005-07-22
CA2552920A1 (en) 2005-08-11
US20080118699A1 (en) 2008-05-22
WO2005073956A1 (en) 2005-08-11
FR2865309B1 (en) 2006-09-08

Similar Documents

Publication Publication Date Title
EP2504832B1 (en) Acoustic panel for an aircraft nacelle and corresponding manufacturing process
CA2441477C (en) Sound attenuation panel comprising a resistive layer with reinforced structural component
EP1398473B1 (en) Acoustic attenuation layer for an acoustic attenuation panel, and a panel with such a layer
EP1239454B1 (en) Method of manufacturing a panel with an adapted, acoustically resistive layer and resulting panel
CA2425364C (en) Acoustically resistive multi-component layer for a sound attenuation panel and panel so obtained
EP1201420B1 (en) Sound absorbing panel particularly for aircraft engine
CA2682306C (en) Method for producing an acoustically resistive structure, resulting acoustically resistive structure and skin using one such structure
EP2393651B1 (en) Method for manufacturing a structure with cellular cores for a turbojet nacelle
CA2365100C (en) Method for making a sound reducing panel with resistive layer having structural property and resulting panel
WO2005073956A1 (en) Perforated skin for acoustic element, acoustic element and method for making same
EP2200818A2 (en) Cellular-core structure for an acoustic panel
WO2011018163A1 (en) Method for repairing a wall consisting of a plurality of layers
CA2488818C (en) Method for making a soundproofing panel with at least one double resonator
FR2839075A1 (en) Adhesive film for bonding a wall to a honeycomb structure comprises holes in front of the cells of the honeycomb structure
FR2767411A1 (en) ACOUSTICALLY RESISTIVE LAYER, METHOD FOR MANUFACTURING THE SAME AND ACOUSTICALLY ABSORBING PANEL PROVIDED WITH AT LEAST ONE SUCH LAYER
FR3036061A1 (en) COMPOSITE PANEL AND AIRCRAFT TURBOBOREACTEUR NACELLE COMPRISING SUCH A PANEL
WO2009133009A1 (en) Improved acoustic panel
EP3723081B1 (en) Method for manufacturing a porous layer of an acoustic absorption structure, porous layer of an acoustic absorption structure thus obtained and acoustic absorption structure including said porous layer
EP3683056A1 (en) Method for manufacturing an acoustically resistive structure, acoustically resistive structure thus obtained, acoustic absorption panel comprising said acoustically resistive structure
EP4002352B1 (en) Shell made of resistive covering comprising perforated metallic layers, and internal acoustic wall of an air entry of an aircraft based on such shells
WO2010119203A1 (en) Cellular panel
WO2024089342A1 (en) Method for forming a sound attenuation structure provided with s-shaped cells
WO2021176182A1 (en) Method for manufacturing a structure with cellular cores for a turbojet nacelle
EP3945518A1 (en) Acoustic material in strips with integrated flange and internal wall of an air intake of an aircraft made using said material
FR3026981A1 (en) INSERT STRUCTURE FOR IMPROVING THERMAL AND ELECTRIC ISOTROPY WITH HEART AND INTERFACES OF COMPOSITE PARTS

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

17P Request for examination filed

Effective date: 20060623

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): DE ES GB IT

DAX Request for extension of the european patent (deleted)
RBV Designated contracting states (corrected)

Designated state(s): DE ES GB IT

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: THE APPLICATION IS DEEMED TO BE WITHDRAWN

18D Application deemed to be withdrawn

Effective date: 20100803