Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B3/00—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar shape; Layered products comprising a layer having particular features of form
  • B32B3/02—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar shape; Layered products comprising a layer having particular features of form characterised by features of form at particular places, e.g. in edge regions
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B3/00—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar shape; Layered products comprising a layer having particular features of form
  • B32B3/10—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar shape; Layered products comprising a layer having particular features of form characterised by a discontinuous layer, i.e. formed of separate pieces of material
  • B32B3/12—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar shape; Layered products comprising a layer having particular features of form characterised by a discontinuous layer, i.e. formed of separate pieces of material characterised by a layer of regularly- arranged cells, e.g. a honeycomb structure
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B3/00—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar shape; Layered products comprising a layer having particular features of form
  • B32B3/26—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar shape; Layered products comprising a layer having particular features of form characterised by a particular shape of the outline of the cross-section of a continuous layer; characterised by a layer with cavities or internal voids ; characterised by an apertured layer
  • B32B3/266—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar shape; Layered products comprising a layer having particular features of form characterised by a particular shape of the outline of the cross-section of a continuous layer; characterised by a layer with cavities or internal voids ; characterised by an apertured layer characterised by an apertured layer, the apertures going through the whole thickness of the layer, e.g. expanded metal, perforated layer, slit layer regular cells B32B3/12
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2307/00—Properties of the layers or laminate
  • B32B2307/10—Properties of the layers or laminate having particular acoustical properties
  • B32B2307/102—Insulating
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B2605/00—Vehicles
  • B32B2605/18—Aircraft
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/24—Structurally defined web or sheet [e.g., overall dimension, etc.]
  • Y10T428/24149—Honeycomb-like

Definitions

• the present invention relates in particular to a honeycomb core structure formed of at least one cellular unit suitable for use in an acoustic panel for a turbojet nacelle.
• Aircraft turbojets generate significant noise pollution. There is a strong demand to reduce this pollution, especially as the turbojets used become more and more powerful.
• the design of the nacelle surrounding a turbojet contributes to a large extent to the reduction of this noise pollution.
• nacelles are equipped with acoustic panels to reduce the noise generated by the turbojet engine and vibration structures.
• acoustic panels are well known structures for absorbing these noises. These panels usually comprise one or more layers of honeycomb core structures (commonly called “honeycomb” structure). These layers are generally coated on their underside, that is to say not in contact with the air flow inside the nacelle, a skin impermeable to air, called “full”, and on their upper face, that is to say in contact with the air flow inside the nacelle, a perforated skin permeable to air, called “acoustic”.
• the acoustic panel may further comprise several layers of cellular core structures between which is inserted, for example glued, a porous or multi-perforated skin, called "septum".
• Such panels constitute acoustic resonators suitable for
• honeycomb core structure is made from joined honeycomb unit (s), called “honeycomb block (s)".
• honeycomb unit is generally obtained by superimposing several sheets of metal, light alloy or composite on which are arranged punctually bonding means which adhere the sheets together at certain points, called junction pads.
• the cellular unit thus produced is said to be in "compacted” form.
• the unit undergoes a stretching so as to separate the leaves that remain attached between they at the junction pads.
• the alveolar unit thus produced is said to be in the form of "expanded”.
• the acoustic properties of the acoustic panel that is to say its rate of absorption of noise as a function of the frequency and the noise level of the noise, depend in particular on the junction of the cellular unit or units, which form a structure with alveolar soul.
• the junction of the lateral ends of cellular units is currently carried out using a foaming glue, such as the FM 410® glue, which has a large expansion capacity.
• Glue generally in the form of a film, is inserted between the adjacent edges of two cellular units which, during its expansion, obstructs the honeycomb cells by creating extra thicknesses at the cell walls of the junction zone. These extra thicknesses have the disadvantage of reducing the effective acoustic surface of the honeycomb structure and also of causing sudden impedance breaks which contribute to the reduction of the acoustic performance of the acoustic panel, by redistribution of the modal energy of the noise by the rotating parts, during operation of the turbojet engine.
• honeycomb core structure is complex and does not provide a completely homogeneous acoustic treatment.
• An object of the present invention is to provide a honeycomb core structure comprising one or more cellular units, simple to implement and having an effective attenuation of the noise induced by the operation of the turbojet engine.
• the subject of the invention is a honeycomb core structure suitable for use in an acoustic panel for a turbojet engine nacelle comprising at least one cellular unit, each cellular unit comprising two end sheets, characterized in that the end sheets are joined together by junction pads arranged to form honeycomb cells.
• the structure according to the invention comprises one or more alveolar units joined (s) so as not to obstruct the cellular cells.
• the junction zone of the structure according to the invention is limited to the cellular cells formed by the junction pads and the end sheets.
• no honeycomb cell of the structure according to the invention is obstructed totally or partially.
• the junction zone has new cellular cells substantially filled with air, which increases the effective acoustic surface of the structure according to the invention.
• the structure according to the invention advantageously allows an effective reduction of the noise without breaking impedance.
• the structure of the invention offers a higher mechanical strength than the structures of the prior art. Indeed, the structure according to the invention behaves as an unassembled whole block consisting of cellular cells. According to other features of the invention, the structure according to the invention comprises one or more of the following optional features considered alone or according to all the possible combinations:
• the junction pads consist of a material selected from metals, alloys or polymers, in particular an epoxy-based resin, which makes it possible to withstand external stresses and does not critically increase the nacelle in which it is intended to be incorporated the structure according to the invention;
• the structure according to the invention has a surface substantially of revolution in order to optimally constitute an acoustic panel nacelle turbojet in order to mitigate noise pollution from the turbojet engine.
• the subject of the invention is a process for preparing a honeycomb core structure according to the invention comprising at least one cellular unit, characterized in that it comprises the steps aimed at:
• substantially expanded cellular cells By “substantially compacted form” is meant herein alveolar units in which the alveolar cells have not been formed but are likely to be formed after stretching of these cells.
• substantially flattened alveolar cells that can be expanded after stretching.
• stretched cellular cells By “expanded cellular cells” is meant stretched cellular cells capable of forming acoustic attenuation means.
• the method according to the invention has the advantage of being simple to implement insofar as the alveolar unit (s) is (are) initially manipulated in their compacted form and then they are stretched from one block to another. another step in order to form the structure according to the invention.
• the method according to the invention has the advantage of providing a honeycomb core structure which may have non-regular cellular cells.
• the expansion means can stretch the structure resulting from step B of the process according to the invention in a non-homogeneous manner.
• the method according to the invention comprises one or more of the following optional characteristics considered alone or according to all the possible combinations:
• the method according to the invention also comprises a step (D) in which a perforated acoustic skin and / or a non-perforated skin is reported on at least one face of the cellular core structure obtained at the end of the step (C) for protecting the structure according to the invention and increasing the acoustic attenuation;
• the bonding means consist of a polymer, metal or alloy used for a weld ensuring the structure according to the invention a good mechanical strength;
• the bonding means consist of material whose position and thickness are such that these bonding means induce a non-zero space filled with air between two end sheets allowing the formation of cellular cells, these ideally hexagonal cells being able to take degraded geometries while ensuring their role of acoustic attenuation;
• the expansion means are mechanical means capable of stretching the structure obtained at the end of step (B) in a direction substantially perpendicular or radial to the inner and outer faces for finely stretching the structure from step B to the desired shape.
• step B 1 is attached in step B 1 alongside the end sheets so as to obtain a surface structure substantially of revolution, which allows to optimally achieve acoustic attenuation panel, in particular an acoustic panel turbojet air intake.
• the invention relates to an acoustic panel for nacelle comprising at least one honeycomb core structure according to the invention or obtainable by the method according to the invention.
• the acoustic panel comprises a plurality of cellular core structures arranged in layers between which is a porous or multi-perforated skin, preferably a septum.
• the invention relates to a turbojet engine nacelle comprising an acoustic panel according to the invention.
• FIG. 1a is a partial schematic cross section of the structure according to the invention.
• FIG. 2 is a perspective view of one embodiment of the structure according to the invention.
• FIGS. 3a to 3c are schematic and partial sections of embodiments of the steps of the method according to the invention.
• FIG. 1a illustrates an embodiment of a honeycomb core structure 10 according to the invention intended to be used in an acoustic panel for a turbojet engine nacelle, not shown.
• the structure 10 of the invention may consist of a honeycomb unit joined to itself or a plurality of honeycomb units joined together edge to edge, in particular two or three.
• the structure 10 according to the invention consists of two cellular units 12 and 14.
• the cellular units 12 and 14 typically comprise intermediate sheets 15 and 16 and two end sheets, one of which 18, 20 of each cellular unit 12, 14 is shown, as well as junction pads 22 and 24.
• the end sheets 18 and 20 are joined together by the junction pads 24 arranged, particularly punctually, over extended areas or substantially continuously, so as to form cells alveolar.
• the sheets 15 and 16 form the walls of honeycomb cells 26 whose vertices are located at the junction pads 22.
• the junction zone 30 between the alveolar units 12 and 14 is formed of cellular cells 32 coming from the point junction of the end sheets 18 and 20 at the junction pads 24.
• the cellular cells 32 participate, like the other cells 26 in the noise attenuation of the structure 10 according to the invention since they are not obstructed or clogged but in addition these cells alveolar 32 increase the attenuation capacity noise of the structure 10 according to the invention.
• the alveolar cells 26 and 32 are, for example, alveolar cells of geometric shape, in particular hexagonal, or else curved.
• the alveolar cells 26 and 32 are of regular shape.
• the honeycomb cells 26 and 32 typically have a width d of between 3 mm and 40 mm, in particular between 8 mm and 12 mm and a height h in particular between 3 mm and 100 mm, in particular between 8 mm and 40 mm.
• the cellular cells 26 and 32 are empty of material and typically filled with air.
• junction pads 24 are preferably made of a material chosen from metals, alloys or polymers, in particular an epoxy-based resin.
• the intermediate sheets 15 and 16 and the end sheets 18 and 20 are made of a material resistant to external stresses and do not critically increase the nacelle in which the structure 10 according to the invention is intended to be incorporated.
• the intermediate sheets 15 and 16 and the end sheets 18 and 20 are made of the same material.
• the intermediate sheets 15 and 16 and the end sheets 18 and 20 are made of a material selected from metals, light alloys and thermoplastic polymers, including aluminum, titanium and a composite.
• the junction pads 24 may have a thickness, in particular, greater than that of the end sheets 18 and 20.
• the end sheets 18 and 20 have a thickness substantially identical to intermediate sheets 15 and 16, in particular between 10 microns and 200 microns.
• the thickness of the junction pads 24 is between 5 microns and 1 mm, in particular between 0.1 mm and 0.4 mm.
• the thickness of a unit 12 and 14 corresponds to that of the structure 10 according to the invention and is in particular between 3 mm and 100 mm or between 8 mm and 40 mm.
• the structure 10 according to the invention has a suitable form to constitute an acoustic panel turbojet nacelle to best mitigate the noise pollution from the latter.
• the structure 10 has a substantially axis-revolution surface 34.
• the structure 10 according to the invention is not of regular shape and is for example of non-regular "barrel" shape, namely that the radius of the cross section is not constant neither along nor radially with respect to the axis of revolution 34 of the structure 10 according to the invention.
• This geometry typically corresponds to a turbojet air intake acoustic conduit.
• the method according to the invention advantageously comprises three steps A, B and C, simple to implement in order to prepare the structure 10 according to the invention.
• FIG. 3a illustrates an embodiment of step A of the method according to the invention in which at least one alveolar unit is selected, two cellular units 112 and 114 being represented here, in a substantially compacted and substantially flat form.
• Each honeycomb unit 112 and 114 typically comprises two end sheets, one of each honeycomb unit 112, 114 is shown respectively 118, 120, intermediate sheets 115 and 116 and junction pads 122 located between the intermediate sheets 115 and 116 .
• the end sheets 118 and 120 have a free surface 124 and 126 capable of being joined on which gluing means are intended to be arranged.
• step B of the method according to the invention shown in FIG. 3b the end sheets 118 and 120 are joined in facing relation by means of gluing means 200 arranged on a of the end sheets 118 or 120 so as to form substantially compacted cellular cells 202.
• the gluing means 200 may be deposited on one of the end sheets 118 or 120 punctually, over wide areas or even substantially continuously.
• one of the two insulated units 112 or 114 may have on the free surface of its end sheet 118 or 120 to be joined gluing means previously arranged in step B.
• the bonding means 200 are typically made of material whose position and thickness are such that these bonding means 200 induce a non-zero space 203 filled with air between two end sheets 118 and 120, which makes it possible to form alveolar cells.
• This space 203 has a thickness substantially equal to the thickness of the bonding means 200.
• the bonding means 200 are preferably made of polymers, metal or alloy used for welding.
• the bonding means 200 become junction pads which delimit with the end sheets 118 and 120 substantially compacted cellular cells 202.
• a structure 204 having an internal surface, not shown, intended to be the closest to the axis of the motor not shown, and an external face not shown, intended to be furthest from the motor axis.
• step B the end sheets 118 and 120 are joined edge to edge so as to obtain a structure 204 of substantially circular surface, in particular substantially cylindrical or barrel-shaped surface.
• the inner face is intended to be the closest radially to the axis of the motor not shown and the outer face intended to be furthest radially from the axis of the motor.
• step C of the process according to the invention shown in FIG. 3c the structure 204 obtained in step B is stretched by an expansion means to form expanded cellular cells 332 in order to obtain the honeycomb core structure 310 according to the invention.
• the expansion means are unrepresented mechanical means able to stretch the structure 204 in a direction radial or perpendicular to the internal and external faces of the structure 204.
• the method according to the invention also comprises a step D in which a perforated acoustic skin and / or a non-perforated skin, full skin, is reported on at least one face of the structure 310 obtained at the end of step C.
• the acoustic skin is generally perforated substantially uniformly.
• the acoustic skin and the solid skin are usually made of a multilayer composite material consisting of a reinforcing fiber impregnated with a polymerized resin.
• the acoustic panel may further comprise several structures 10 according to the invention or 310 obtained according to the method of the invention arranged in layers between which is a porous or multiperforated skin, preferably a septum, in order to constitute a multi-stage resonator.
• the septum consists of a porous layer or a microperforated skin of holes having a diameter of between 0.1 mm and 1 mm.
• the acoustic panel is then assembled by arranging the various layers, namely internal acoustic skin, structure (s) 10 according to the invention or 310 obtained (s) according to the invention, possibly septum and full skin, glued on a mold to the form required.
• the assembly undergoes an assembly cycle so as to clamp the layers and form a sandwich assembly using for example an autoclave to polymerize the adhesives.
• the full skin can be made and glued in one operation on the acoustic panel.

Landscapes

• Soundproofing, Sound Blocking, And Sound Damping (AREA)
• Laminated Bodies (AREA)
• Structures Of Non-Positive Displacement Pumps (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=39322794

Family Applications (1)

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• 2007
  • 2007-10-16 FR FR0707247A patent/FR2922152B1/fr not_active Expired - Fee Related
• 2008
  • 2008-09-10 WO PCT/FR2008/001263 patent/WO2009066036A2/fr active Application Filing
  • 2008-09-10 CN CN200880112028.7A patent/CN101827702B/zh not_active Expired - Fee Related
  • 2008-09-10 EP EP08852512A patent/EP2200818A2/de not_active Withdrawn
  • 2008-09-10 CA CA2700183A patent/CA2700183A1/fr not_active Abandoned
  • 2008-09-10 US US12/738,550 patent/US8245815B2/en not_active Expired - Fee Related
  • 2008-09-10 BR BRPI0818630 patent/BRPI0818630A2/pt not_active IP Right Cessation
  • 2008-09-10 RU RU2010119056/05A patent/RU2477223C2/ru not_active IP Right Cessation

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