US20110100747A1 - Sandwich element for the sound-absorbing inner cladding of means of transport, especially for the sound-absorbing inner cladding of aircraft - Google Patents

Abstract

A sandwich element for sound-absorbing inner cladding of means of transport, especially aircraft, comprising a three-dimensionally constructed core disposed between two substantially parallel cover layers is provided.

Sound transmission passages are incorporated in the core, and/or in at least one cover layer. At least one sound absorption layer is in the area of a cover layer at least in parts. Passages in the cover layers and core provide good sound absorption and heat insulation. The passages allow transmission of sound. The through channels and the preferably inclined installation of the sandwich element allow foreign bodies to be flushed out by, for example, a cleaning liquid or condensation. Possibly sufficient sound absorption can be achieved without the sound absorption layer. Ventilation of the core prevents the long-term presence of condensation, which could cause corrosion and/or rotting. A fire-retardant layer including metal particles may increase fire protection and electromagnetic insulation.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS
• This application is a continuation-in-part of U.S. patent application Ser. No. 12/227,569, filed on Nov. 19, 2008 which is a national stage of PCT/EP2006/004944 filed on May 24, 2006, the disclosures of each of which are hereby incorporated herein by reference.
BACKGROUND OF THE INVENTION
• The invention relates to a sandwich element for providing a sound-absorbing inner cladding of means of transport, especially for a sound-absorbing inner cladding of aircraft, comprising a three-dimensionally constructed core structure which is disposed between two cover layers which run substantially parallel to one another at a distance.
• Sandwich panels of fibre-reinforced plastic materials are generally used for the inner cladding of aircraft fuselage cells for reasons of saving weight and because of the high strength requirements. The sandwich panels used commonly have a honeycomb-shaped core structure which is provided with cover layers on both sides to form the sandwich panel. As a result of the honeycomb-shaped structure being covered with the cover layers on both sides, the sandwich panels have a plurality of repeated units which are closed in themselves, of small volume and therefore not capable of drainage.
• In addition, sandwich panels are known whose core structures for example have a wavy, trapezoidal or triangular cross-sectional geometry. Core structures of this type comprise a plurality of channels running approximately parallel to one another, which are formed by folding the core structure material. Sandwich panels having this type of core structures are widely used, for example, in ship building and in automobile construction. Core structures of this type are also used in the packaging industry, for example, in the form of corrugated boards. A feature common to said core structures is that, in relation to core structures having honeycomb cores, these generally have continuous drainable channels whose flanks form flat surfaces.
• In addition, core structures with continuous drainable channels are known wherein the flanks of the channels form no continuous flat surfaces. The flanks of the channels of these core structures are formed by a plurality of partial surfaces which adjoin one another at an angle of less than 180° and thus have zigzag-shaped channels or zigzag-shaped apex lines and base lines when viewed from above. In contrast to the core structures folded or structured in only one spatial direction, such as corrugated cardboard cores, for example, these core structures are folded in two spatial directions. Furthermore, core structures of this type are known which, when viewed from above, form approximately trapezoidal channels or trapezoidal apex lines and base lines.
• The cover layers of sandwich panels are formed by so-called “prepregs”. Prepregs are surface structures produced using resin-impregnated glass fibres or resin-impregnated carbon fibres. Alternatively, fabric mats made of carbon fibres or glass fibres may be impregnated with synthetic resin to form prepregs.
• The core structures are manufactured, for example using Nomex® paper, aluminium films or films made of aluminium alloys by folding, by forming waves or the like. The cover layers can be formed of prepregs with carbon fibres or of prepregs with glass fibres. Alternatively, both the cover layers and the core structures can be manufactured using a metal material, for example, using aluminium sheet, sheets of aluminium alloys, steel sheet or titanium sheet. Both the cover layers and the core structures can alternatively consist of a combination of metal materials with plastic materials.
• The bonding of the cover layers to the core structure to form sandwich panels may be effected by means of bonding methods, for example, by gluing or by welding. In particular, the bonding may be effected depending on the material used by hot or cold adhesion methods in autoclaves as also by ultrasound, laser or spot welding.
• In order to meet the increasingly higher requirements for sound protection in aircraft construction, however, in addition to high strength values, the sandwich panels used for inner claddings of aircraft must also have good sound damping properties.
• In previously known embodiments of sandwich panels for inner claddings of aircrafts interiors no appreciable air exchange may be possible between the external environment and the interior region of the sandwich panel. However, the possibility of air exchange may be an essential prerequisite for a good sound transmission effect for this type of sandwich panel which in turn, in conjunction with an additional sound absorption layer, may be the prerequisite for a good sound damping effect. However, providing the possibility for air exchange between the external environment and the inner region of a sandwich panel may involve the risk of foreign bodies being incorporated and the penetration of moisture. The presence of foreign bodies and moisture in the known sandwich panels thus may involve an increased tendency to rotting and/or an increased susceptibility to corrosion during flight, for example, as a result of the cyclic stressing with condensing and re-freezing moisture which takes place there as a result of large external pressure and temperature fluctuations. In addition, permanent incorporation of foreign bodies inside the core structure may be undesirable, for reasons of weight among other things.
SUMMARY OF THE INVENTION
• It is thus an object of the invention to provide a sandwich element for a sound-absorbing inner cladding of aircraft which firstly has a sufficiently good sound absorption property as a result of the possibility of sound transmission through passages incorporated in the core structure and/or at least one cover layer as far as a sound absorption layer, where at the same time, permanent incorporation of foreign bodies penetrating from outside and/or permanent retention of moisture which has penetrated in the area of the core structure is largely avoided. Furthermore, the sandwich element should satisfy specific requirements for application in aircraft such as specific safety requirements.
• According to an exemplary embodiment of the present invention, a sandwich element having the features ofclaim1 is provided.
• Since a plurality of passages for sound transmission are incorporated in the core structure and/or in at least one cover layer, at least in sections, where a sound absorption layer is disposed in at least part of an area of at least one cover layer, the possibility of air exchange and therefore of sound transmission may be provided between the external environment and the sandwich element so that an excellent sound absorption effect of the sandwich layer may be achieved in conjunction with the sound absorption layer. At the same time, the inner region of the sandwich element may be ventilated as a result of passages so that moisture which has penetrated unexpectedly from outside can evaporate again relatively rapidly before rotting processes or corrosion processes may take place in the inner area of the sandwich element.
• The sound absorption layer may also improve the heat insulating properties of the sandwich element.
• According to a further exemplary embodiment of the present invention, the core structure between the cover layers comprises a plurality of through channels disposed adjacent to one another for the drainage of fluids and for flushing out foreign bodies. Within the channels, on the one hand, sound penetrating from outside through the passages is effectively passed through the interior region of the sandwich element and then absorbed in the sound absorption layer. On the other hand, the channels allow active cleaning of the inner region of the sandwich element from foreign bodies by a suitable, externally supplied cleaning agent, for example, in the form of water, or by passive self-cleaning by out-flowing water of condensation.
• To form the inner cladding, the sandwich elements are preferably built in with a sufficient gradient so that a cleaning agent which enters through the passages or by means of the channels can flush out foreign bodies deposited in the core structure through the action of gravity in the course of active cleaning. In parallel with this, an independent, that is, passive cleaning of the sandwich element can optionally also be effected by the through channels acting in the fashion of gutters. During the self-cleaning process, any water of condensation flows off through the channels, entraining at least some, especially smaller and lighter foreign bodies, as it flows off into the outer region.
• Thus, the passages in the core structure and/or in the cover layers in conjunction with the through channels of the core structure may make it possible to achieve a good sound absorption effect of the sandwich element according to the invention and may provide the possibility of being able to remove dirt particles which have undesirably been incorporated, by means of a suitable cleaning agent. Furthermore, as a result of the presence of the passages, moisture which has undesirably penetrated may evaporate and/or flow off as a result of the gradient of the built-in sandwich element by means of the channels formed inside the core structure.
• It has been observed that the passages in the core structure may provide for improved air exchange such that air can easily circulate through the passages of the panel. However, such air circulation may also have negative effects e.g. in case of a fire. Due to a stack-effect, air can be provided to the fire location and the fire propagation may be accelerated. Even in case that the core structure is made from a material which is hardly flammable, the stack-effect may result in increased flammability of the sandwich panel. Therefore, at least the core structure comprising the passages should be coated with a fire-retardant material. The fire-retardant material may provided for retarded fire propagation when compared to non-coated core structures.
• According to a further exemplary embodiment of the present invention, the channels have flanks, wherein the flanks each form a continuous, substantially flat and/or curved surface. This makes the manufacture of the core structure simple and cost-effective. In addition, the flushing out of incorporated foreign bodies is made easier as a result of the rectilinear profile of the channels.
• According to a further exemplary embodiment of the sandwich element according to the invention, the channels have flanks which are formed with a plurality of substantially flat and/or curved partial surfaces, wherein the partial surfaces adjoin one another at an angle of less than 180°.
• By using this type of core structure, it may be possible to produce sandwich elements having higher mechanical strengths compared to sandwich elements formed with core structures merely having rectilinear channels. However, this type of core structure may be more complex to manufactures, more expensive and may also be more difficult to clean of foreign impurities.
• According to a further exemplary embodiment of the sandwich element according to the invention, the core structure has a repetitive triangular, trapezoidal, triangular or wavy cross-sectional geometry. This configuration allows the sandwich element to be manufactured easily whilst at the same time having favourable mechanical properties. Previously known, pre-fabricated semi-finished products may be used in part.
• According to a further exemplary embodiment of the invention, the passages in at least one cover layer and/or in the core structure are disposed approximately uniformly spaced apart, especially in the manner of perforations. By this means, on the one hand, the passages can easily be produced in the cover layers and/or in the core structure, for example, by drilling, punching or the like. On the other hand, the configuration of the passages in the form of a perforation incorporated preferably over the entire area of the cover layers and the core structure may make it possible to achieve very effective sound absorption.
• According to a further exemplary embodiment of the invention, fire retardant layer with which the core structure is coated comprises an intumescent material. An intumescent is a substance which swells as a result of heat exposure, thus increasing in volume, and decreasing in density.
• For example, soft char producers may produce a light char, which is a poor conductor of heat, thus retarding heat transfer. Typically, these materials may also contain a significant amount of hydrates. As the hydrates are spent, water vapour may be released, which has a cooling effect. Once the water is spent, it is only the insulation characteristics of the char that was produced, which can slow down heat transfer from the exposed side to the unexposed side of an assembly. Soft char producers may be used e.g. in thin film intumescents for fireproofing of structural steel as well as firestop pillows. Typically, the expansion pressure that is created for these products is very low, because the soft carbonaceous char has little substance, which may be beneficial if the aim is to produce a layer of insulation.
• As an alternative example, hard expanding char may be produced with sodium silicates and graphite. In some applications, it may be necessary to produce a more substantial char, with a quantifiable expansion pressure. In the case of firestops, a melting, burning plastic pipe must be squeezed together and shut so that there will be no hole for fire to go through an opening in an otherwise fire-resistance rated wall or floor assembly.
• As the core structure is coated with a layer of intumenscent material, this layer is not only hardly flammable but, furthermore, the intumescent material, upon fire impact, may partly or completely close the passages and channels provided by the core. Thus, the closed passages and channels may prevent or reduce stack-effects and may therefore slow down fire propagation.
• According to a further exemplary embodiment of the invention the fire retardant layer comprises a glass forming material. Such glass forming material may be an oxide that may readily form a glass layer upon heating. This glass layer may coat and protect the underlying portions of the core structure when in contact with fire.
• According to a further exemplary embodiment of the invention the fire retardant layer comprises metal particles. The incorporation of metal particles into the fire retardant layer may provide for an electrical conductivity of this layer. Due to this electrical conductivity, the core structure coated with the fire retardant layer may serve as an electromagnetic insulation (EMI). Due to this EMI, the sandwich panel may protect adjacent electrical circuits from the influence of electromagnetic radiation, which may be important especially in high security applications such as in aircraft applications.
• Thus, due to the metalized coating, the core structure may have both, fire-retardant and electromagnetically insulating properties. Accordingly, even if the core structure itself is made from a cheap and easy to manufacture base material such as plastics or Nomex© paper, the coating provided thereon may enable application of the sandwich panel e.g. in aircraft application.
• Further advantageous embodiment of the arrangement are present in the further claims.
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 shows an isometric diagram of a sandwich element according to the invention,
• FIG. 2 shows an isometric exploded diagram of the sandwich element,
• FIG. 3 shows a plan view of a first exemplary embodiment of a core structure and
• FIG. 4 shows a plan view of a second exemplary embodiment of a core structure.
• FIG. 5 shows a core structure coated with a fire-retardant layer.
DETAILED DESCRIPTION OF THE DRAWINGS
• FIG. 1 shows an isometric diagram of a sandwich element according to the invention. Asandwich element1 comprises, amongst other things, twocover layers2,3 which are applied to both sides of acore structure4. Applied to the side of thecover layer3 facing away from thecore structure4 is asound absorption layer5 to achieve the desired high sound absorption effect of thesandwich element1. In addition, thesound absorption layer5 also enhances the heat insulating capacity of thesandwich element1 according to the invention.
• FIG. 2 shows an isometric exploded diagram of the sandwich element according to the invention.
• Thesandwich element1 comprises, amongst other things, thecore structure4 with the cover layers2,3 applied to both sides. Thesound absorption layer5 is applied to the lower side of thecover layer3. A plurality ofpassages6 are incorporated both in the cover layers2,3 and also in thecore structure4.
• For reasons of better clarity of the drawing, in the diagram inFIG. 2 only threerepresentative passages6 in the area of thecover layer2, thecover layer3 and thecore structure4 have been provided with a reference number. The remaining passages not designated in detail are constructed identically.
• As an example, thepassages6 are constructed in the form of through holes which are incorporated in the cover layers2,3 and in thecore structure4 preferably distributed uniformly with respect to one another. In the exemplary embodiment shown the passages are incorporated in the cover layers2,3 and thecore structure4 in matrix fashion in the form of a full-area perforation. Especially for an effective sound absorption effect of thesandwich element1, thepassages6 pass through the entire material thickness of the cover layers2,3 and the material thickness of thecore structure4. Unlike the diagram inFIG. 2, thepassages6 can have a configuration which differs from cylindrical geometry. Thepassages6 allow very efficient transmission of thesound7 impinging upon thesandwich element1 through the cover layers2,3 and thecore structure4 where the energy of thesound7 is then largely converted by dissipation into heat in thesound absorption layer5.
• In addition, thecore structure4 has a plurality ofadjacent channels8. For the sake of clarity, in the diagram inFIG. 2 only three channels representative of the remaining channels of the core structure have been provided with reference numbers. Thechannels8 are formed by respectively twoflanks9 of which only two which are representative of the remaining flanks, have been provided with a reference number inFIG. 1. The flanks not provided with a reference number are constructed identically to the two provided with a reference number.
• In thecore structure4 theflanks9 do not form a continuous surface. Rather, theflanks9 are formed by a plurality ofpartial surfaces10 which each adjoin one another at an angle of less than 180° and thus form substantially zigzag-shapedchannels8. The partial surfaces10 each form a substantially flat and/or curved surface when considered by itself. In this case, thechannels8 or theflanks9 each have a substantially zigzag-shaped apex line orbase line11,12. Of theapex lines11 or the base lines12, only three, representative of the remainder, have been provided with a reference number.
• In the exemplary embodiment shown, thechannels8 have a substantially triangular cross-sectional geometry which is repeated continuously over the entire length of thesandwich element1. The zigzag-shapedchannels8 allow the formation of acore structure4 having high mechanical strengths. In contrast hereto, core structures which merely have structuring or folding in one spatial direction such as, for example, corrugated cardboard cores, trapezoidal core structures, single folded cores or the like, have lower mechanical strength values.
• Thesandwich element1 according to the invention may be built in to form inner claddings in aircraft such that in the final built-in position thechannels8 run substantially parallel to anarrow13 which indicates the direction of the action of gravity. This built-in position is preferably to be selected so that undesirable foreign bodies which have penetrated into thecore structure4 through thepassages6, can be conveyed out of the core structure again, for example, by active flushing using a cleaning agent or by passive flushing by means of residual water of condensation. At least, care should be taken to ensure that thechannels8 have a sufficient gradient in relation to the horizontal or a sufficient slope to ensure adequate (self-) cleaning of thecore structure4 from foreign bodies which have penetrated therein. Water to which suitable cleaning aids are optionally added, for example, can be used as cleaning agent.
• Thesound absorption layer5 may be arranged over the entire area or applied thereto underneath thecover layer3. Thesound absorption layer5 is used firstly to achieve the desired sound absorption effect of thesandwich element1 and at the same time as a heat insulating layer. Depending on the area of application, a possibly sufficient sound absorption effect may also be achieved by means of thesandwich element1 according to the invention without the presence of the additionalsound absorption layer5. Alternatively, it is also possible to apply thesound absorption layer5 merely in sections to thecover layer3. Thesound absorption layer5 can furthermore be arranged at a distance from thecover layer3 of thesandwich element1. In this case, an intermediate air space exists between thecover layer3 and thesound absorption layer5.
• Thesound absorption layer5 may, for example be formed using glass or mineral wool. Alternatively, thesound absorption layer5 may also be formed using a spun yarn of fine metal fibres, carbon fibres, plastic fibres and using open-pore foamed plastics.
• Thecore structure4 may be formed using a plastic material, for example, using epoxy resin-impregnated Nomex® paper. Alternatively, thecore structure4 may also be formed using a metal alloy, for example, using aluminium, using an aluminium alloy, using steel or titanium. Thecore structure4 may be produced, for example, by multiple folding or another type of structuring of a surface plastic material or a metal surface material.
• Thecore structure4 may have a geometrical configuration which differs from the triangular cross-sectional geometry shown. For example, rectangular, trapezoidal or wavy cross-sectional geometries of thecore structure4 are possible. In a triangular, rectangular or trapezoidal cross-sectional geometry of thecore structure4, for example, a plurality of angles of inclination or radii of curvature are possible for theflanks9 in relation to the horizontal.
• The cover layers2,3 may likewise be formed using a composite material, for example, using carbon-fibre-reinforced prepregs made of epoxy resin or using a metal material. Aluminium, an aluminium alloy, steel or titanium in particular can be considered as metal material. Furthermore, the cover layers2,3 may be formed using a foamed plastic material or using metal foams which are preferably constructed as open-pored. In addition, both the cover layers2,3 and also thecore structure4 may be formed using any combination of composite materials and/or metal materials, especially according to the type described previously.
• For reasons of weight, the material thicknesses of the cover layers2,3 and thecore structure4 have relatively low values. The material thickness of the cover layers2,3 may be less than 10 mm and the height of thecore structure4 may be less than 50 mm. Thesound absorption layer5 may have a material thickness of less than 100 mm. Thepassages6 in the cover layers2,3 and thecore structure4 may be formed by means of known methods, that is for example by drilling, by stamping, by laser drilling or the like. Thepassages6 in the cover layers2,3 and thecore structure4 may have a cylindrical geometry which may be easy to produce, having a diameter of less than mm. Furthermore, in alternative embodiments cross-sectional geometries of thepassages6 which differ from a cylindrical geometry may also be possible.
• The mechanical bonding of the cover layers2,3 to thecore structure4 and thesound absorption layer5 optionally provided is effected in each case depending on the type of materials to be bonded using known bonding methods, such as for example hot- or cold-setting adhesive methods or general welding methods. Alternatively, the bonding can be effected by riveting, adhesive tape or the like.
• FIG. 3 shows a plan view of a first exemplary embodiment of a core structure.
• Thecore structure4 forms a plurality ofadjacent channels8 having a zigzag structure when viewed from above. For better clarity, only threerepresentative channels8 have a reference number. The remaining channels are constructed identically to these. For reasons of better clarity of the drawing, the passages in thecore structure4 are not shown.
• Any water of condensation or cleaning agent which has additionally been introduced may flow out from thechannels8 in the direction of thearrow13 which symbolises the direction of the action of gravity and at the same time, any foreign bodies which have penetrated into thecore structure4 can be flushed out from thechannels8. Thechannels8 also have a plurality offlanks9 of which only two, representative of the remainder, are provided with reference numbers. Thechannels8 each have respectively oneapex line11 and abase line12 which each have an approximately zigzag-shaped profile and run approximately uniformly spaced from one another. Theflanks9 are formed by a plurality ofpartial surfaces10 which each adjoin one another at anangle14 having a value of less than 180° to form theflanks9. In the diagram inFIG. 3 theangle14, for example, has a value of about 90°. Different values for theangle14 are also possible to form alternative embodiments of core structures. In principal, smaller values for theangle12 facilitate the flow of condensation and/or cleaning agents which have additionally been introduced, from thechannels8 in the direction of thearrow11, although the attainable mechanical strength decreases.
• In another exemplary embodiment, which is not shown, theapex lines11 and the base lines12 of thecore structure4 each have a substantially trapezoidal, repeating profile. Other geometrical profiles of theapex lines11 andbase lines12 of thecore structure4 are likewise possible.
• In addition, theapex lines11 and the base lies12 of thechannels8 can have almost any feasible, for example, wavy, curved or washboard-like geometrical shape other than the zigzag-shaped profile illustrated inFIG. 3, whereby in conjunction with the possibilities for forming the cross-sectional geometries of thecore structure4 indicated, an almost unlimited range of variation of the design of three-dimensional core structures4 with throughchannels8 is obtained. In this connection, for example, it is feasible to have a profile ofapex lines11 orbase lines12 corresponding to a plurality of semicircles arranged in rows.
• In acore structure4 having a wavy cross-sectional geometry and also having wavyapex lines11 andbase lines12, thechannels8 can be formed, for example by a sectional compression or stretching of the material used to form thecore structure4. This procedure is especially possible for metallic materials, especially using aluminium or aluminium alloys.
• FIG. 4 shows a plan view of a second exemplary embodiment of a core structure with rectilinear channels.
• Thecore structure15 is formed by a plurality of substantiallyrectilinear channels16 arranged adjacent to one another, each having an approximately rectangular cross-sectional geometry. For reasons of better clarity of the drawing, the passages in thecore structure15 are not shown in detail. In this embodiment of thecore structure15 theflanks17 each form substantially flat surfaces. The channels each haveapex lines18 and base lines19.
• As a result of the substantially rectilinear formation of thechannels16, in this embodiment of thecore structure15 any water of condensation can easily flow out from thechannels16 in the direction of thearrow13 and at the same time flush out any foreign bodies which have been incorporated. The same applies to any cleaning agent which has additionally been introduced into thecore structure15, such as water with suitable cleaning additions or the like. Compared with thecore structure4 according toFIG. 3, only inferior mechanical strengths can be achieved although the manufacturing expenditure is reduced.
• As a result of the excellent sound absorption properties, the sandwich element according to the invention may be suited to the formation of inner claddings in aircraft. In this case, an almost arbitrary range of variation of core structures with respectively different geometrical configurations can be used, a configuration comprising three-dimensional, drainable and therefore through channels being common to the core structures.
• FIG. 5 shows an exemplary embodiment of acore structure4 which is coated with a fire-retardant layer21. Thefire retardant layer21 covers the entire surface of thecore structure4 including thepassages6. Thus, thechannels8,16 formed by thecore structure4 are coated with the fire-retardant layer21. The fire-retardant layer comprises an intumescent material which enlarges its volumes upon application of fire and heat. Thus, in case of fire, thechannels8,16 may be closed by the enlarging intumescent material and a stack-effect in thechannels8, may be prevented. Pyro-Safe DG-HF, Pyrotarp PB333 may be used as intumescent material. Pyro-Safe DG-HF can be obtained e.g. from svt Brandschutzvertriebsgeselschaft mbh international which is located in Seevetal (Germany). Pyrotarp PB333 may be obtained from Bradford Industries which is located in Lowell, Mass. 01851 (USA). Both intumescent materials are admitted for aircraft applications.
• Furthermore, the fire-retardant layer21 comprisesmetal particles22 which provide for an electrical conductivity of thelayer21 and therefore provide for an electromagnetic insulation of thecore4 covered with thelayer21. With such electromagnetic insulation, the sandwich panel may furthermore act as an electromagnetical shield and protect adjacent electrical circuits. Bronze (CuSn6), Copper (99, 90%), Aluminium (99, 90%) may be used as metal particles.
REFERENCE LIST
• 1 Sandwich element
• 2 Cover layer
• 3 Cover layer
• 4 Core structure
• 5 Sound absorption layer
• 6 Passage
• 7 Sound
• 8 Channel
• 9 Flank
• 10 Partial surface
• 11 Apex line
• 12 Base line
• 13 Arrow
• 14 Angle
• 15 Core structure
• 16 Channel
• 17 Flank
• 18 Apex line
• 19 Base line
• 21 fire-retardant layer
• 22 metal particles

Claims (12)

1. A sandwich element for providing a sound-absorbing inner cladding of means of transport, especially for a sound-absorbing inner cladding of aircraft, the sandwich element comprising:

a three-dimensionally constructed core structure which is disposed between two cover layers which run substantially parallel to one another at a distance;

wherein a plurality of passages for sound transmission, disposed in a perforation-like manner, are incorporated respectively in the core structure and in both cover layers;

wherein the core structure comprises a plurality of through channels disposed adjacent to one another and parallel to the cover layers;

wherein the trough channels are adapted for drainage of fluids and for flushing out foreign bodies;

wherein the core structure is coated with a fire retardant layer;

and wherein at least one sound absorption layer is disposed in at least part of an area of a cover layer.

2. The sandwich element according toclaim 1, wherein the channels have flanks;

wherein the flanks each form a continuous, substantially flat and/or curved surface.

3. The sandwich element according toclaim 1, wherein the channels have flanks which are formed with a plurality of substantially flat and/or curved partial surfaces, wherein the partial surfaces adjoin one another at an angle of less than 180°.

4. The sandwich element according toclaim 1, wherein the core structure has a repetitive triangular, trapezoidal, rectangular or wavy cross-sectional geometry.

5. The sandwich element according toclaim 1, wherein the passages are especially constructed as cylindrical, elliptical or polygonal openings.

6. The sandwich element according toclaim 1, wherein the sound absorption layer is constructed as thermally insulating.

7. The sandwich element according toclaim 1, wherein the core structure and/or the cover layers are formed with a plastic material.

8. The sandwich element according toclaim 1, wherein the core structure and/or the cover layers are formed with a fibre-reinforced plastic material.

9. The sandwich element according toclaim 1, wherein the core structure and/or the cover layers are formed with a metal material.

10. The sandwich element according toclaim 1, wherein the fire retardant layer comprises an intumescent material.

11. The sandwich element according toclaim 1, wherein the fire retardant layer comprises a glass forming material.

12. The sandwich element according toclaim 1, wherein the fire retardant layer comprises metal particles.

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