WO2010069922A1 - Aircraft part made of a composite material with aluminium protection against the effects of lightning - Google Patents

Aircraft part made of a composite material with aluminium protection against the effects of lightning Download PDF

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Publication number
WO2010069922A1
WO2010069922A1 PCT/EP2009/067083 EP2009067083W WO2010069922A1 WO 2010069922 A1 WO2010069922 A1 WO 2010069922A1 EP 2009067083 W EP2009067083 W EP 2009067083W WO 2010069922 A1 WO2010069922 A1 WO 2010069922A1
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WIPO (PCT)
Prior art keywords
elements
composite material
lightning
aluminum
surface treatment
Prior art date
Application number
PCT/EP2009/067083
Other languages
French (fr)
Inventor
Martine Villatte
Stéphane SUEL
Original Assignee
European Aeronautic Defence And Space Company Eads France
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Filing date
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Application filed by European Aeronautic Defence And Space Company Eads France filed Critical European Aeronautic Defence And Space Company Eads France
Publication of WO2010069922A1 publication Critical patent/WO2010069922A1/en

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B64—AIRCRAFT; AVIATION; COSMONAUTICS
    • B64D—EQUIPMENT FOR FITTING IN OR TO AIRCRAFT; FLIGHT SUITS; PARACHUTES; ARRANGEMENTS OR MOUNTING OF POWER PLANTS OR PROPULSION TRANSMISSIONS IN AIRCRAFT
    • B64D45/00—Aircraft indicators or protectors not otherwise provided for
    • B64D45/02—Lightning protectors; Static dischargers
    • 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
    • B32B15/00—Layered products comprising a layer of metal
    • B32B15/14—Layered products comprising a layer of metal next to a fibrous or filamentary layer
    • 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
    • B32B15/00—Layered products comprising a layer of metal
    • B32B15/20—Layered products comprising a layer of metal comprising aluminium or copper
    • 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 form; Layered products 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 form; Layered products 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 form; Layered products 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 form; Layered products 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 form; Layered products 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 form; Layered products 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
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
    • C25D11/02—Anodisation
    • C25D11/04—Anodisation of aluminium or alloys based thereon
    • C25D11/06—Anodisation of aluminium or alloys based thereon characterised by the electrolytes used
    • C25D11/08—Anodisation of aluminium or alloys based thereon characterised by the electrolytes used containing inorganic acids
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
    • C25D11/02—Anodisation
    • C25D11/04—Anodisation of aluminium or alloys based thereon
    • C25D11/06—Anodisation of aluminium or alloys based thereon characterised by the electrolytes used
    • C25D11/10—Anodisation of aluminium or alloys based thereon characterised by the electrolytes used containing organic acids
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
    • C25D11/02—Anodisation
    • C25D11/04—Anodisation of aluminium or alloys based thereon
    • C25D11/18—After-treatment, e.g. pore-sealing
    • C25D11/24—Chemical after-treatment
    • C25D11/246—Chemical after-treatment for sealing layers
    • 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
    • B32B2260/00—Layered product comprising an impregnated, embedded, or bonded layer wherein the layer comprises an impregnation, embedding, or binder material
    • B32B2260/02—Composition of the impregnated, bonded or embedded layer
    • B32B2260/021—Fibrous or filamentary layer
    • 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
    • B32B2260/00—Layered product comprising an impregnated, embedded, or bonded layer wherein the layer comprises an impregnation, embedding, or binder material
    • B32B2260/04—Impregnation, embedding, or binder material
    • B32B2260/046—Synthetic resin
    • 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
    • B32B2262/00—Composition or structural features of fibres which form a fibrous or filamentary layer or are present as additives
    • B32B2262/10—Inorganic fibres
    • B32B2262/106—Carbon fibres, e.g. graphite fibres
    • 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
    • B32B2307/20—Properties of the layers or laminate having particular electrical or magnetic properties, e.g. piezoelectric
    • B32B2307/202—Conductive
    • 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
    • B32B2307/70—Other properties
    • B32B2307/71—Resistive to light or to UV
    • 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
    • B32B2307/70—Other properties
    • B32B2307/714—Inert, i.e. inert to chemical degradation, corrosion
    • 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

Definitions

  • the present invention is in the field of aircraft parts made with composite materials, and more particularly such parts including means for protection against the effects of lightning strikes, in the form of an array of electrically conductive elements.
  • the invention relates more particularly to the parts made of composite material based on carbon fibers.
  • a composite material is defined throughout the present description in a conventional manner, that is to say as constituted by the assembly of several different elementary components bonded together, more particularly mechanically resistant fibers distributed in an organic polymer resin matrix.
  • the resin is here a polymer compound, which may be of the thermoplastic or thermosetting type, which plays the role of a structural adhesive in which the fibers are dispersed in a more or less organized manner.
  • the fibers are carbon fibers, woven or unidirectional.
  • the composite material thus formed has mechanical properties of its own, quite advantageous in terms of mechanical strength and lightness.
  • Composite materials are electrically insulating or weakly conductive. Therefore, when they are used to produce aircraft structural parts that are subjected, during use of the device, to the external aerodynamic flow of the latter, electric charges tend to accumulate naturally on the surface of the material. In the absence of special precautions, when the differences in electrical potential are locally sufficient, due to the amount of accumulated electrical charges, these charges are discharged into the ambient air, in the form of electric discharges that generate electromagnetic disturbances likely to disrupt the operation of the electronic systems of the aircraft.
  • a metal protection against the effects of lightning in the form of an array of electrically conductive elements.
  • These metal elements are interconnected so as to form a network that covers the entire surface of the piece likely to be subjected to lightning strikes. They are also interconnected from one piece of composite material to another composite material part, or the same conductive metal structure, so as to provide effective protection over the entire structure of the aircraft.
  • the metal elements together ensure the dispersion of the lightning current over the entire surface of the room, which improves the lightning resistance of the latter.
  • the present invention aims to overcome the drawbacks of aircraft structural parts made of carbon-based composite material, including those described above, by providing a composite material part that is effectively protected against the effects of lightning, and which avoids accumulations of electric charges on its surface, with a mass penalty which is reduced compared to previous solutions.
  • an aircraft structure part formed of a structural part made of composite material based on carbon fibers comprises, on one face of this structural part, at least on one side of the part likely to be subjected to to lightning strikes, an array of electrically conductive elements providing protection against the effects of lightning strikes.
  • These elements are formed of aluminum or aluminum alloy, and they have an anti-corrosion protection layer on the surface. They are in direct contact with the structural part of composite material, over substantially their entire surface, that is to say that no intermediate layer, in particular insulating layer, is arranged between each element and the part structural composite material.
  • the protective layer formed on the surface of the elements is an aluminum hydroxide layer, resulting from a treatment of the elements by an anodizing step followed by at least one clogging step .
  • aluminum alloy refers to any aluminum-based alloy itself, as well as aluminum itself.
  • the protective layer against corrosion obtained by a surface treatment of the metal elements, advantageously protects the aluminum alloy from the risks of corrosion on contact with the carbon involved in the constitution of the composite material. It is thus no longer necessary in the part according to the invention, unlike a solution proposed in the prior art, to interpose a protective insulating layer between the elements of the electrically conductive network and the structural part made of composite material.
  • the part including these elements according to the invention advantageously has a much lower mass than those of the prior art, thanks to the intrinsic properties of aluminum and the absence of any other additional interlayer material, for electrical conductivity performance, and thus a protection effectiveness against the effects of lightning strikes, at least equivalent.
  • the anticorrosion protection layer is formed on each network element at least on its surface in contact with the composite material.
  • the presence of this corrosion layer does not significantly increase the surface mass of the element, which retains its advantageous properties in terms of lightness.
  • the invention applies advantageously to all types of elements in aluminum alloy capable of forming a network effectively protecting the room against the effects of lightning strikes and having a low mass per unit area, in particular grids, metals deployed, or thin sheets, perforated or not. These elements are placed on the part so as to come into contact with each other, to ensure the dispersion of the lightning current over the entire surface of the part, whatever the point of impact of the lightning on it.
  • the elements according to the invention prove to be quite advantageous for the protection against the effects of lightning of aircraft structural parts, in particular aircraft fuselage and wing panels, which are frequently subjected in flight to lightning impacts. They exhibit lightning protection performance at least as good as those of the elements used in the prior art, while being lighter, which is particularly advantageous in the aeronautical field. They are effectively protected against corrosion in contact with carbon fibers, so that they have a capacity to protect against the effects of lightning constant over time.
  • the anodizing treatment is defined in the present description in a conventional manner.
  • This is anodic oxidation of the element, which has the effect of creating a layer of aluminum oxide on its surface.
  • This layer may have, depending on the desired applications, a thickness of a few microns, which can go for applications in an aggressive environment, up to a few tens of microns.
  • the surface layer of corrosion protection has a thickness of between 2.5 and 5 ⁇ m, which advantageously provides effective protection of the aluminum alloy in contact with the fiber-based material. of carbon.
  • the element is immersed in an electrolyte solution.
  • An electric current is applied in the electrolysis cell, in which the element forms the anode.
  • the positive ions H + move towards the cathode where they pick up the electrons and they give rise to the release of hydrogen.
  • the negative ions OH migrate to the anode where they give off electrons, and give rise to incipient oxygen, which reacts with the aluminum to form an oxide on the surface of the element.
  • the anodization can be carried out using any electrolyte conventionally used for carrying out such a surface treatment method, for example sulfuric acid, chromic acid or boric acid, phosphoric acid, etc., or a mixture of such compounds
  • the electrolyte is a mixture of sulfuric acid and tartaric acid, which is particularly preferably at requirements of respect for the environment.
  • the anticorrosion protection layer of the element results from a treatment by an anodizing step followed by a single hydrothermal treatment plugging step.
  • a treatment uses the property that the layer of alumina resulting from anodizing to hydrate in boiling water. Immersion in boiling water has the effect of tightening and clogging the pores. It is obtained on the element a surface layer of sealed aluminum hydroxide, which protects it advantageously effectively against corrosion.
  • a first step of clogging by immersion of the element in an aqueous solution based on metal salts, corrosion inhibitors is implemented before a second clogging step by hydrothermal treatment in boiling water in the presence of additives of the surfactant type.
  • This first step is preferably carried out using a solution based in particular on the salt of chromium III. It also has the effect of blocking the pores of the surface layer of aluminum oxide.
  • the two sealing steps carried out successively make it possible to obtain a substantially complete filling of the pores, by the presence of a corrosion inhibitor, for example the chromium III, which guarantees an effective protection of the element against corrosion on contact with carbon.
  • aluminum alloy network elements are subjected to an anticorrosion surface treatment, as described above, so to form on their surface an anti-corrosion protection layer. These elements are then applied in an array directly against at least the face of said structural part of composite material on the side of the piece likely to be subjected to the impacts of lightning, so as to form a protection against the effects of lightning for the latter .
  • the composite material forming the structural part of the piece is conventional in itself. It consists of carbon fibers held in a polymer organic matrix.
  • the resin used may be both thermoplastic and thermosetting, and the workpiece may be manufactured by any conventional method in itself.
  • the aluminum elements surface-treated so as to be resistant to corrosion can, in the context of the invention, both be assembled to the finished part, in particular by gluing, than be included in the part at the time of its manufacture when the resin is not yet fully cured. They are then fixed on the finished part by the very effect of this resin which plays the role of structural adhesive after hardening.
  • a piece of aircraft structure more particularly intended to be exposed to lightning impacts, in particular a piece of aircraft fuselage or wing panel, comprises a structural part formed of composite material based on carbon fibers, which are held in a polymer organic resin matrix tough.
  • This resin may be of any type, thermoplastic or thermosetting, for example an epoxy resin
  • the structure is for example, but not limited to, formed from stacked folds of woven or unidirectional fibers. It may be monolithic and / or comprise in its thickness a cellular structure, foam or honeycomb, between two coatings made by fibers held in a matrix.
  • the structure is shaped according to the shape of the part during a forming process before curing of the matrix material by polymerization, in the case of so-called thermosetting matrices, or during a forming process.
  • a temperature for which the matrix is in a plastic state in the case of thermoplastic matrices.
  • the part according to the invention comprises on one side of the structural part, at least on one side of the part likely to be subjected to lightning impacts, that is to say on the side exposed to the outside of the body.
  • an array of electrically conductive aluminum alloy elements which scatter the lightning current from the point of impact.
  • the elements are fixed to the piece by any conventional means in itself, in particular by gluing.
  • the network may equally well be formed of a single element, in the case in particular of small parts, or of a plurality of elements, identical or not, in the case of larger and / or non-developable parts. . In this case, these elements are in contact with each other, so as to ensure the transmission of lightning current from one network element to another. Electrically conductive elements can also be present in the form of a mesh, expanded metal, a thin sheet, where appropriate perforated, or any other conventional form in itself for protection against the effects of lightning strikes of aircraft parts .
  • the elements of the network are applied to the part directly against the structural part of composite material, excluding any intermediate layer. Prior to their mounting on the part, they are advantageously protected against corrosion by a surface protection layer.
  • the latter is formed by a surface treatment of the element comprising an anodizing step followed by at least one clogging step.
  • each element is prepared prior to the implementation of the anodizing step, in particular by washing and / or deoxidation.
  • the anodizing process is conventional in itself. It can be implemented using any electrolyte known per se. In preferred embodiments of the invention, it is an anodization known as TSA, in which the electrolyte used is a mixture of sulfuric acid and tartaric acid.
  • TSA an anodization known as TSA, in which the electrolyte used is a mixture of sulfuric acid and tartaric acid.
  • the aqueous solution contains, for example, from 10 to 200 g of sulfuric acid and from 5 to 200 g of tartaric acid, in particular L (+) - tartaric acid, per liter of solution.
  • the use of such a mixture of these acids has the particular advantage of greatly limiting the production of industrial waste harmful to the environment, in particular waste containing chromium. This method is also quick to implement, which results in a saving of time and cost of manufacture.
  • the parameters of the anodizing process are advantageously chosen, according to calculations within the abilities of those skilled in the art, as a function of the thickness of the desired protection layer on the element.
  • the protective layer on each element preferably has a thickness between 2.5 and 5 microns.
  • the voltage applied in the tank is preferably between 10 and 30 V, the temperature between 25 and 43 0 C.
  • the total cycle time is between 5 and 30 min.
  • One or two clogging steps are then performed on the aluminum oxide layer, so as to develop the corrosion resistance of the element.
  • the clogging may be carried out by dipping in water at a temperature of at least 96 ° C., for a time which is a function of the thickness of the protective layer obtained by anodization, for example 30 minutes.
  • the hydrothermal treatment described above is carried out in water containing surfactant compounds, and it is preceded by a prior step of clogging by immersion in an aqueous solution of metal salts with about 10% by volume, containing in particular a salt of Chromium III, at a temperature of 20 to 40 0 C, during 2 to 15 minutes.
  • the aluminum alloy element thus obtained has good electrical conductivity and low weight per unit area, so that it is entirely suitable for forming a protective network that is both light and effective against the effects of the impacts of lightning for aircraft structural parts.
  • Expanded aluminum alloy metal plates 60 mm by 60 mm in size, having a thickness of 100 ⁇ m, a surface density of 100 g / m 2 , and an electrical conductivity of 500 Siemens / m, have been used.
  • Comparative Plate One of these plates, called Comparative Plate, was used as it was, without any particular protection against corrosion.
  • a second plate, designated Plate 1 was subjected to anticorrosion treatment by anodization followed by a sealing step by hydrothermal treatment, according to the conditions stated above.
  • This plate was first subjected, in a conventional manner, to washing and degreasing operations.
  • the anodization was carried out in an electrolytic cell, in which the cathode was formed of stainless steel and had a surface at least equal to that of the plate, with operating parameters selected in the following ranges.
  • the anodization was carried out in the presence of sulfuric acid and tartaric acid in concentrations of 40 g / l for sulfuric acid and 90 g / l for tartaric acid, at a temperature between 35 and 38 ° C. C, at a voltage of 15 V, for a cycle time of 25 minutes.
  • the plate was rinsed with water and then clogged. The latter was carried out by immersion of the plate in demineralized water at a temperature of at least 96 ° C. for a period of 30 minutes.
  • a last plate, called Plate 2 was subjected to an anticorrosion treatment by an anodizing step followed by a step of clogging in an aqueous solution of metal salts, then a clogging step by hydrothermal treatment in the presence of surfactant type additives.
  • the anodization was carried out according to the process described for the
  • the first clogging step was carried out by immersing the element in an aqueous solution based on metal salts at approximately 10% by volume, containing in particular a chromium III salt, at a temperature 40 0 C, for 10 minutes. This step was followed by a second step of clogging by hydrothermal treatment, in the presence of surfactants.
  • An impervious surface layer of aluminum hydroxide having a thickness of 2.5 to 5 ⁇ m was obtained on Plate 2.
  • Parts made of composite material based on carbon fibers in an organic epoxy resin have been manufactured conventionally, for example by a process using a mold in which successive folds of fibers pre-impregnated with resin are deposited, and by baking under conditions of temperature and pressure ensuring the crosslinking of the resin and the compacting of the folds.
  • a first salt spray test was carried out on each of the isolated plates for a duration of exposure of 1000 hours.
  • a second test was carried out on each of the plates in direct contact with a piece of carbon-based composite material, during a period of exposure of
  • Plates 1 and 2 corresponding to a treatment by TSA anodization followed by respectively one and two sealing steps, have high performances in terms of anti-corrosion resistance, and superior to those of Comparative Plaque 1 untreated.
  • Plates 1 and 2 have a substantially unchanged surface mass relative to the plates prior to any surface treatment, i.e., about 100 g / m 2 . Their electrical conductivity remains good, and adequate to provide effective protection against the effects of lightning strikes for aircraft structural panels that may be exposed to such impacts.
  • the present invention achieves the objectives it has set for itself.
  • aircraft structure parts made of carbon fiber composite material, which comprise a network of aluminum alloy elements that effectively protect them against lightning, have a low weight per unit area and are resistant to the risk of damage. corrosion on contact with carbon.

Abstract

The invention relates to a part for an aircraft structure consisting of a structural portion made of a carbon fibre composite, said part comprising, on a surface of said structural portion, at least on a side of the part likely to be subjected to impacts from lightning, an array of electrically conducting elements. The substantially entire surface of the elements is in direct contact with the composite material structural portion of the part. The elements are made of aluminium or of an aluminium alloy and have, on the surface thereof, an anticorrosion protection layer resulting from a surface treatment including an anodisation step followed by at least one, preferably two, sealing steps.

Description

PIECE D'AERONEF EN MATERIAU COMPOSITE A PROTECTION CONTRE LES EFFETS DE LA FOUDRE EN ALUMINIUM AIRCRAFT PIECE OF COMPOSITE MATERIAL WITH ALUMINUM LIGHT EFFECT PROTECTION
La présente invention entre dans le domaine des pièces d'aéronefs réalisées avec des matériaux composites, et plus particulièrement de telles pièces incluant des moyens de protection contre les effets des impacts de foudre, sous la forme d'un réseau d'éléments électriquement conducteurs. L'invention concerne plus particulièrement les pièces réalisées en matériau composite à base de fibres de carbone.The present invention is in the field of aircraft parts made with composite materials, and more particularly such parts including means for protection against the effects of lightning strikes, in the form of an array of electrically conductive elements. The invention relates more particularly to the parts made of composite material based on carbon fibers.
L'utilisation des matériaux composites est de nos jours largement répandue dans de nombreux domaines industriels, en particulier dans la construction aéronautique, du fait notamment du gain de masse que ces matériaux permettent d'obtenir par rapport à des matériaux conventionnels, à propriétés mécaniques équivalentes, et de la possibilité de réaliser au moyen de tels matériaux des pièces de formes complexes.The use of composite materials is nowadays widespread in many industrial fields, in particular in the aeronautical construction, in particular because of the mass gain that these materials make possible compared to conventional materials, with equivalent mechanical properties. and the possibility of making such pieces of complex shapes using such materials.
Un matériau composite est défini dans toute la présente description de manière classique, c'est-à-dire comme constitué par l'assemblage de plusieurs composants élémentaires différents liés entre eux, plus particulièrement des fibres mécaniquement résistantes distribuées dans une matrice de résine organique polymère dure. La résine est ici un composé polymère, pouvant être du type thermoplastique ou thermodurcissable, qui joue le rôle d'une colle structurale dans laquelle les fibres sont dispersées de manière plus ou moins organisée. Dans le cadre de l'invention, les fibres sont des fibres de carbone, tissées ou unidirectionnelles. Le matériau composite ainsi formé présente des propriétés mécaniques qui lui sont propres, tout à fait avantageuses en termes de résistance mécanique et de légèreté.A composite material is defined throughout the present description in a conventional manner, that is to say as constituted by the assembly of several different elementary components bonded together, more particularly mechanically resistant fibers distributed in an organic polymer resin matrix. tough. The resin is here a polymer compound, which may be of the thermoplastic or thermosetting type, which plays the role of a structural adhesive in which the fibers are dispersed in a more or less organized manner. In the context of the invention, the fibers are carbon fibers, woven or unidirectional. The composite material thus formed has mechanical properties of its own, quite advantageous in terms of mechanical strength and lightness.
Les matériaux composites sont électriquement isolants ou faiblement conducteurs. De ce fait, lorsqu'ils sont mis en œuvre pour réaliser des pièces de structure d'aéronefs qui sont soumises, lors de l'utilisation de l'appareil, à l'écoulement aérodynamique externe de ce dernier, des charges électriques ont tendance à s'accumuler naturellement à la surface du matériau. En l'absence de précautions particulières, lorsque les différences de potentiel électrique sont localement suffisantes, du fait de la quantité des charges électriques accumulées, ces charges sont évacuées dans l'air ambiant, sous la forme de décharges électriques qui génèrent des perturbations électromagnétiques susceptibles de perturber le fonctionnement des systèmes électroniques de l'aéronef.Composite materials are electrically insulating or weakly conductive. Therefore, when they are used to produce aircraft structural parts that are subjected, during use of the device, to the external aerodynamic flow of the latter, electric charges tend to accumulate naturally on the surface of the material. In the absence of special precautions, when the differences in electrical potential are locally sufficient, due to the amount of accumulated electrical charges, these charges are discharged into the ambient air, in the form of electric discharges that generate electromagnetic disturbances likely to disrupt the operation of the electronic systems of the aircraft.
De plus, les pièces de structure d'aéronefs en vol sont fréquemment soumises à des impacts de foudre, dont l'énergie est suffisante pour provoquer un endommagement local de la structure. On comprend aisément qu'il est essentiel qu'elles soient protégées contre les effets néfastes de ces impacts. Les matériaux composites présentent intrinsèquement un mauvais comportement en réponse aux impacts de foudre, du fait de leur caractère électriquement isolant ou faiblement conducteur, si bien qu'ils sont incapables d'évacuer le courant associé à la foudre. Ceci engendre un fort risque d'endommagement de la structure au droit de l'impact.In addition, structural parts of aircraft in flight are frequently subjected to lightning strikes, the energy of which is sufficient to cause local damage to the structure. It is easy to understand that it is essential that they be protected against the harmful effects of these impacts. Composite materials inherently exhibit poor behavior in response to lightning strikes due to their electrically insulating or poorly conductive nature, so that they are unable to evacuate the current associated with lightning. This generates a high risk of damaging the structure to the right of impact.
Pour remédier à cet inconvénient, il a été proposé dans l'art antérieur d'inclure dans les pièces en matériaux composites d'aéronefs, au moins sur un côté de la pièce susceptible d'être soumis à des impacts de foudre, en général sur leur surface disposée à l'extérieur de l'aéronef, une protection métallique contre les effets de la foudre, sous forme d'un réseau d'éléments électriquement conducteurs. Ces éléments métalliques sont reliés entre eux de manière à former un réseau qui couvre toute la surface de la pièce susceptible d'être soumise à des impacts de foudre. Ils sont également reliés entre eux d'une pièce en matériau composite à une autre pièce en matériau composite, ou à une même structure métallique conductrice, de manière à assurer une protection efficace sur toute la structure de l'aéronef. Les éléments métalliques assurent ensemble la dispersion du courant de foudre sur toute la surface de la pièce, ce qui améliore la tenue à la foudre de cette dernière. Pour constituer une telle protection, on utilise fréquemment des grillages en bronze ou en alliage de cuivre. Ceux-ci atteignent généralement une masse surfacique comprise entre 150 et 300 g/m2, qui n'est pas satisfaisante pour des pièces utilisées dans le domaine aéronautique, dans lequel on rencontre de fortes exigences d'optimisation de la masse. Afin de pallier cet inconvénient, le choix des concepteurs s'est tourné vers l'utilisation d'un matériau plus léger pour former le réseau métallique, à savoir l'aluminium. Dans le cadre particulier cependant des matériaux composites à base de carbone, ils se sont heurtés au problème de la corrosion, par un phénomène de couplage galvanique, de l'aluminium en présence des fibres de carbone. La solution proposée en réponse à ce problème a été d'intercaler, entre les éléments en alliage d'aluminium et la surface de la pièce en matériau composite, une couche d'un matériau isolant électrique, dans la plupart des cas un tissu de verre, de manière à éviter tout contact entre le métal et les fibres de carbone. Cette couche isolante pénalise cependant la mise en œuvre du réseau métallique, et cette solution reste encore insatisfaisante de ce point de vue.To overcome this drawback, it has been proposed in the prior art to include in composite material parts of aircraft, at least on one side of the part likely to be subjected to lightning impacts, generally on their surface disposed outside the aircraft, a metal protection against the effects of lightning, in the form of an array of electrically conductive elements. These metal elements are interconnected so as to form a network that covers the entire surface of the piece likely to be subjected to lightning strikes. They are also interconnected from one piece of composite material to another composite material part, or the same conductive metal structure, so as to provide effective protection over the entire structure of the aircraft. The metal elements together ensure the dispersion of the lightning current over the entire surface of the room, which improves the lightning resistance of the latter. To constitute such a protection, we often use grilles made of bronze or copper alloy. These usually reach a weight per unit area of between 150 and 300 g / m 2 , which is not satisfactory for parts used in the aeronautical field, in which there are high demands for optimization of the mass. To overcome this disadvantage, the choice of designers has turned to the use of a lighter material to form the metal network, namely aluminum. In the particular context, however, of composite materials based on carbon, they have encountered the problem of corrosion, by a galvanic coupling phenomenon, of aluminum in the presence of carbon fibers. The solution proposed in response to this problem was to interpose, between the aluminum alloy elements and the surface of the composite material part, a layer of an electrical insulating material, in most cases a glass fabric. , so as to avoid any contact between the metal and the carbon fibers. This insulating layer, however, penalizes the implementation of the metal network, and this solution is still unsatisfactory from this point of view.
La présente invention vise à remédier aux inconvénients des pièces de structure d'aéronefs en matériau composite à base de carbone existantes, notamment à ceux exposés ci-avant, en proposant une pièce en matériau composite qui soit protégée efficacement contre les effets de la foudre, et qui évite les accumulations de charges électriques à sa surface, avec une pénalité de masse qui est réduite par rapport aux solutions antérieures.The present invention aims to overcome the drawbacks of aircraft structural parts made of carbon-based composite material, including those described above, by providing a composite material part that is effectively protected against the effects of lightning, and which avoids accumulations of electric charges on its surface, with a mass penalty which is reduced compared to previous solutions.
Selon l'invention, une pièce de structure d'aéronef formée d'une partie structurale en matériau composite à base de fibres de carbone comporte, sur une face de cette partie structurale, au moins sur un côté de la pièce susceptible d'être soumis à des impacts de foudre, un réseau d'éléments électriquement conducteurs formant protection contre les effets des impacts de foudre. Ces éléments sont formés en aluminium ou en alliage d'aluminium, et ils présentent en surface une couche de protection anticorrosion. Ils sont en contact direct avec la partie structurale en matériau composite, sur sensiblement toute leur surface, c'est-à-dire qu'aucune couche intercalaire, notamment isolante, n'est disposée entre chaque élément et la partie structurale en matériau composite.According to the invention, an aircraft structure part formed of a structural part made of composite material based on carbon fibers comprises, on one face of this structural part, at least on one side of the part likely to be subjected to to lightning strikes, an array of electrically conductive elements providing protection against the effects of lightning strikes. These elements are formed of aluminum or aluminum alloy, and they have an anti-corrosion protection layer on the surface. They are in direct contact with the structural part of composite material, over substantially their entire surface, that is to say that no intermediate layer, in particular insulating layer, is arranged between each element and the part structural composite material.
Selon une caractéristique avantageuse de l'invention, la couche de protection formée en surface des éléments est une couche d'hydroxyde d'aluminium, résultant d'un traitement des éléments par une étape d'anodisation suivie d'au moins une étape de colmatage.According to an advantageous characteristic of the invention, the protective layer formed on the surface of the elements is an aluminum hydroxide layer, resulting from a treatment of the elements by an anodizing step followed by at least one clogging step .
Dans toute la présente description, on désignera pour plus de commodité, par le terme alliage d'aluminium, tout alliage à base d'aluminium proprement dit, ainsi que l'aluminium lui-même.Throughout this description, for the sake of convenience, the term "aluminum alloy" refers to any aluminum-based alloy itself, as well as aluminum itself.
La couche de protection contre la corrosion, obtenue par un traitement de surface des éléments métalliques, protège avantageusement l'alliage d'aluminium des risques de corrosion au contact du carbone entrant dans la constitution du matériau composite. Il n'est ainsi plus besoin, dans la pièce selon l'invention, contrairement à une solution proposée dans l'art antérieur, d'interposer une couche isolante protectrice entre les éléments du réseau électriquement conducteur et la partie structurale en matériau composite. La pièce incluant ces éléments selon l'invention présente avantageusement une masse bien inférieure à celles de l'art antérieur, grâce aux propriétés intrinsèques de l'aluminium et à l'absence de tout autre matériau intercalaire supplémentaire, pour des performances de conductivité électrique, et donc une efficacité de protection contre les effets des impacts de foudre, au moins équivalentes.The protective layer against corrosion, obtained by a surface treatment of the metal elements, advantageously protects the aluminum alloy from the risks of corrosion on contact with the carbon involved in the constitution of the composite material. It is thus no longer necessary in the part according to the invention, unlike a solution proposed in the prior art, to interpose a protective insulating layer between the elements of the electrically conductive network and the structural part made of composite material. The part including these elements according to the invention advantageously has a much lower mass than those of the prior art, thanks to the intrinsic properties of aluminum and the absence of any other additional interlayer material, for electrical conductivity performance, and thus a protection effectiveness against the effects of lightning strikes, at least equivalent.
La couche de protection anticorrosion est formée sur chaque élément de réseau au moins sur sa surface en contact avec le matériau composite.The anticorrosion protection layer is formed on each network element at least on its surface in contact with the composite material.
Pour des raisons pratiques, liées à la mise en œuvre de procédés de traitement de surface industriels, elle est avantageusement formée sur l'ensemble de la surface de l'élément.For practical reasons, related to the implementation of industrial surface treatment processes, it is advantageously formed over the entire surface of the element.
La présence de cette couche de corrosion n'augmente avantageusement pas significativement la masse surfacique de l'élément, qui conserve ses propriétés avantageuses en terme de légèreté. L'invention s'applique avantageusement à tous types d'éléments en alliage d'aluminium susceptibles de former un réseau protégeant efficacement la pièce contre les effets des impacts de foudre et présentant une faible masse surfacique, en particulier les grillages, les métaux déployés, ou encore les feuilles minces, perforées ou non. Ces éléments sont placés sur la pièce de manière à entrer en contact les uns avec les autres, pour assurer la dispersion du courant de foudre sur toute la surface de la pièce, quel que soit le point d'impact de la foudre sur cette dernière.The presence of this corrosion layer does not significantly increase the surface mass of the element, which retains its advantageous properties in terms of lightness. The invention applies advantageously to all types of elements in aluminum alloy capable of forming a network effectively protecting the room against the effects of lightning strikes and having a low mass per unit area, in particular grids, metals deployed, or thin sheets, perforated or not. These elements are placed on the part so as to come into contact with each other, to ensure the dispersion of the lightning current over the entire surface of the part, whatever the point of impact of the lightning on it.
Les éléments selon l'invention s'avèrent tout à fait avantageux pour la protection contre les effets de la foudre des pièces de structure d'aéronefs, en particulier des panneaux de fuselage et de voilure d'avions, qui sont fréquemment soumis en vol à des impacts de foudre. Ils présentent des performances de protection contre la foudre au moins aussi bonnes que celles des éléments utilisés dans l'art antérieur, tout en étant plus légers, ce qui est particulièrement avantageux dans le domaine aéronautique. Ils sont protégés de manière efficace contre la corrosion au contact des fibres de carbone, si bien qu'ils présentent une capacité de protection contre les effets de la foudre constante dans le temps.The elements according to the invention prove to be quite advantageous for the protection against the effects of lightning of aircraft structural parts, in particular aircraft fuselage and wing panels, which are frequently subjected in flight to lightning impacts. They exhibit lightning protection performance at least as good as those of the elements used in the prior art, while being lighter, which is particularly advantageous in the aeronautical field. They are effectively protected against corrosion in contact with carbon fibers, so that they have a capacity to protect against the effects of lightning constant over time.
Le traitement par anodisation est défini dans la présente description de façon classique. Il s'agit d'une oxydation anodique de l'élément, qui a pour effet de créer une couche d'oxyde d'aluminium sur sa surface. Cette couche peut présenter, selon les applications souhaitées, une épaisseur de quelques microns, pouvant aller, pour des applications en milieu agressif, jusqu'à quelques dizaines de microns. Dans des modes de réalisation préférés de l'invention, la couche superficielle de protection anticorrosion présente une épaisseur comprise entre 2,5 et 5 μm, qui assure avantageusement une protection efficace de l'alliage d'aluminium au contact du matériau à base de fibres de carbone.The anodizing treatment is defined in the present description in a conventional manner. This is anodic oxidation of the element, which has the effect of creating a layer of aluminum oxide on its surface. This layer may have, depending on the desired applications, a thickness of a few microns, which can go for applications in an aggressive environment, up to a few tens of microns. In preferred embodiments of the invention, the surface layer of corrosion protection has a thickness of between 2.5 and 5 μm, which advantageously provides effective protection of the aluminum alloy in contact with the fiber-based material. of carbon.
Pour la mise en œuvre de l'étape d'anodisation, l'élément est immergé dans une solution d'électrolyte. Un courant électrique est appliqué dans la cuve d'électrolyse, dans laquelle l'élément forme l'anode. Sous l'action du champ électrique, les ions positifs H+ se dirigent vers la cathode où ils captent les électrons et ils donnent lieu au dégagement d'hydrogène. Les ions négatifs OH" migrent vers l'anode où ils cèdent des électrons, et donnent lieu à de l'oxygène naissant. Ce dernier réagit avec l'aluminium pour former un oxyde à la surface de l'élément. Selon l'invention, l'anodisation peut être effectuée au moyen de tout électrolyte utilisé de façon classique pour la mise en œuvre d'un tel procédé de traitement de surface, par exemple de l'acide sulfurique, de l'acide chromique, de l'acide borique, de l'acide phosphorique, etc., ou un mélange de tels composés. Dans des modes de réalisation préférés de l'invention, l'électrolyte est un mélange d'acide sulfurique et d'acide tartrique, qui répond notamment avantageusement au mieux à des exigences de respect de l'environnement.For the implementation of the anodization step, the element is immersed in an electrolyte solution. An electric current is applied in the electrolysis cell, in which the element forms the anode. Under the action of the electric field, the positive ions H + move towards the cathode where they pick up the electrons and they give rise to the release of hydrogen. The negative ions OH " migrate to the anode where they give off electrons, and give rise to incipient oxygen, which reacts with the aluminum to form an oxide on the surface of the element. the anodization can be carried out using any electrolyte conventionally used for carrying out such a surface treatment method, for example sulfuric acid, chromic acid or boric acid, phosphoric acid, etc., or a mixture of such compounds In preferred embodiments of the invention, the electrolyte is a mixture of sulfuric acid and tartaric acid, which is particularly preferably at requirements of respect for the environment.
La couche superficielle d'alumine ainsi formée étant poreuse, l'élément est ensuite soumis à au moins une étape de colmatage visant à en obturer les pores, de manière à assurer que cette couche présente les propriétés de protection de l'élément contre la corrosion requises.The surface layer of alumina thus formed being porous, the element is then subjected to at least one sealing step intended to seal the pores, so as to ensure that this layer has the protective properties of the element against corrosion required.
Dans des modes de réalisation préférés de l'invention, la couche de protection anticorrosion de l'élément résulte d'un traitement par une étape d'anodisation suivie d'une unique étape de colmatage par traitement hydrothermal. Un tel traitement utilise la propriété qu'a la couche d'alumine issue de l'anodisation de s'hydrater dans l'eau bouillante. Une immersion dans l'eau bouillante a pour effet de resserrer et colmater les pores. Il est obtenu sur l'élément une couche superficielle d'hydroxyde d'aluminium étanche, qui le protège avantageusement efficacement contre la corrosion.In preferred embodiments of the invention, the anticorrosion protection layer of the element results from a treatment by an anodizing step followed by a single hydrothermal treatment plugging step. Such a treatment uses the property that the layer of alumina resulting from anodizing to hydrate in boiling water. Immersion in boiling water has the effect of tightening and clogging the pores. It is obtained on the element a surface layer of sealed aluminum hydroxide, which protects it advantageously effectively against corrosion.
Dans d'autres modes de réalisation préférés de l'invention, après l'étape d'anodisation, une première étape de colmatage par immersion de l'élément dans une solution aqueuse à base de sels métalliques, inhibiteurs de corrosion, est mise en œuvre avant une seconde étape de colmatage par traitement hydrothermal dans de l'eau bouillante en présence d'additifs de type agents tensioactifs. Cette première étape est de préférence réalisée au moyen d'une solution à base notamment de sel de Chrome III. Elle a également pour effet de bloquer les pores de la couche superficielle d'oxyde d'aluminium. Dans un tel mode de réalisation, les deux étapes de colmatage réalisées successivement permettent d'obtenir une obturation sensiblement complète des pores, par la présence d'un inhibiteur de corrosion, par exemple le Chrome III, qui garantit une protection efficace de l'élément contre la corrosion au contact du carbone.In other preferred embodiments of the invention, after the anodizing step, a first step of clogging by immersion of the element in an aqueous solution based on metal salts, corrosion inhibitors, is implemented before a second clogging step by hydrothermal treatment in boiling water in the presence of additives of the surfactant type. This first step is preferably carried out using a solution based in particular on the salt of chromium III. It also has the effect of blocking the pores of the surface layer of aluminum oxide. In such an embodiment, the two sealing steps carried out successively make it possible to obtain a substantially complete filling of the pores, by the presence of a corrosion inhibitor, for example the chromium III, which guarantees an effective protection of the element against corrosion on contact with carbon.
Tout autre procédé de colmatage classique en lui-même, ou toute succession de tels procédés, entre également dans le cadre de l'invention.Any other conventional clogging method itself, or any succession of such methods, is also within the scope of the invention.
Selon un procédé de fabrication d'une pièce en matériau composite à base de fibres de carbone selon l'invention, des éléments de réseau en alliage d'aluminium sont soumis à un traitement de surface anticorrosion, tel que décrit ci-avant, de manière à former sur leur surface une couche de protection anticorrosion. Ces éléments sont ensuite appliqués en réseau directement contre au moins la face de ladite partie structurale en matériau composite du côté de la pièce susceptible d'être soumis aux impacts de foudre, de manière à former une protection contre les effets de la foudre pour cette dernière.According to a method of manufacturing a piece of carbon fiber composite material according to the invention, aluminum alloy network elements are subjected to an anticorrosion surface treatment, as described above, so to form on their surface an anti-corrosion protection layer. These elements are then applied in an array directly against at least the face of said structural part of composite material on the side of the piece likely to be subjected to the impacts of lightning, so as to form a protection against the effects of lightning for the latter .
Le matériau composite formant la partie structurale de la pièce est classique en lui-même. Il est constitué de fibres de carbone maintenues dans une matrice organique polymère. La résine utilisée peut aussi bien être du type thermoplastique que thermodurcissable, et la pièce peut être fabriquée au moyen de tout procédé classique en lui-même. Les éléments en aluminium traités en surface de manière à être résistants à la corrosion peuvent, dans le cadre de l'invention, aussi bien être assemblés à la pièce finie, notamment par collage, qu'être inclus dans la pièce au moment de sa fabrication, lorsque la résine n'est pas encore entièrement durcie. Ils sont alors fixés sur la pièce finie par l'effet même de cette résine qui joue le rôle de colle structurale après durcissement.The composite material forming the structural part of the piece is conventional in itself. It consists of carbon fibers held in a polymer organic matrix. The resin used may be both thermoplastic and thermosetting, and the workpiece may be manufactured by any conventional method in itself. The aluminum elements surface-treated so as to be resistant to corrosion can, in the context of the invention, both be assembled to the finished part, in particular by gluing, than be included in the part at the time of its manufacture when the resin is not yet fully cured. They are then fixed on the finished part by the very effect of this resin which plays the role of structural adhesive after hardening.
L'invention sera maintenant plus précisément décrite dans le cadre de modes de réalisation particuliers, qui n'en sont nullement limitatifs, qui font l'objet de l'exemple ci-après. Selon l'invention, une pièce de structure d'aéronef, plus particulièrement destinée à être exposée aux impacts de foudre, notamment une pièce de panneau de fuselage ou de voilure d'un avion, comporte une partie structurale formée en matériau composite à base de fibres de carbone, qui sont maintenues dans une matrice de résine organique polymère dure. Cette résine peut être de tout type, thermoplastique ou thermodurcissable, par exemple une résine époxyThe invention will now be more specifically described in the context of particular embodiments, which are in no way limiting, which are the subject of the example below. According to the invention, a piece of aircraft structure, more particularly intended to be exposed to lightning impacts, in particular a piece of aircraft fuselage or wing panel, comprises a structural part formed of composite material based on carbon fibers, which are held in a polymer organic resin matrix tough. This resin may be of any type, thermoplastic or thermosetting, for example an epoxy resin
La structure est par exemple, mais non limitativement, formée à partir de plis empilés de fibres tissées ou unidirectionnelles. Elle peut être monolithique et/ou comporter dans son épaisseur une structure alvéolaire, mousse ou nid d'abeille, entre deux revêtements réalisés par des fibres maintenues dans une matrice.The structure is for example, but not limited to, formed from stacked folds of woven or unidirectional fibers. It may be monolithic and / or comprise in its thickness a cellular structure, foam or honeycomb, between two coatings made by fibers held in a matrix.
De manière connue, la structure est conformée à la forme de la pièce au cours d'un processus de formage avant durcissement par polymérisation du matériau de la matrice, dans le cas des matrices dites thermodurcissables, ou au cours d'un processus de formage à une température pour laquelle la matrice est dans un état plastique, dans le cas des matrices thermoplastiques.In known manner, the structure is shaped according to the shape of the part during a forming process before curing of the matrix material by polymerization, in the case of so-called thermosetting matrices, or during a forming process. a temperature for which the matrix is in a plastic state, in the case of thermoplastic matrices.
La pièce selon l'invention comporte sur une face de la partie structurale, au moins sur un côté de la pièce susceptible d'être soumis aux impacts de foudre, c'est-à-dire sur le côté exposé vers l'extérieur de l'appareil, un réseau d'éléments électriquement conducteurs en alliage d'aluminium, qui assurent la dispersion du courant de foudre depuis le point de l'impact. Les éléments sont fixés à la pièce par tout moyen classique en lui-même, notamment par collage.The part according to the invention comprises on one side of the structural part, at least on one side of the part likely to be subjected to lightning impacts, that is to say on the side exposed to the outside of the body. apparatus, an array of electrically conductive aluminum alloy elements, which scatter the lightning current from the point of impact. The elements are fixed to the piece by any conventional means in itself, in particular by gluing.
Le réseau peut aussi bien être formé d'un seul élément, dans le cas notamment de pièces de petite taille, que d'une pluralité d'éléments, identiques ou pas, dans le cas de pièces de plus grande taille et/ou non développables. Dans ce cas, ces éléments sont en contact les uns avec les autres, de manière à assurer la transmission du courant de foudre d'un élément du réseau à un autre. Les éléments électriquement conducteurs peuvent aussi bien se présenter sous forme d'un grillage, d'un métal déployé, d'une feuille mince, le cas échéant perforée, ou de toute autre forme classique en elle-même pour la protection contre les effets des impacts de foudre des pièces d'aéronefs.The network may equally well be formed of a single element, in the case in particular of small parts, or of a plurality of elements, identical or not, in the case of larger and / or non-developable parts. . In this case, these elements are in contact with each other, so as to ensure the transmission of lightning current from one network element to another. Electrically conductive elements can also be present in the form of a mesh, expanded metal, a thin sheet, where appropriate perforated, or any other conventional form in itself for protection against the effects of lightning strikes of aircraft parts .
Les éléments du réseau sont appliqués sur la pièce directement contre la partie structurale en matériau composite, à l'exclusion de toute couche intercalaire. Préalablement à leur montage sur la pièce, ils sont avantageusement protégés contre la corrosion par une couche de protection de surface. Cette dernière est formée par un traitement de surface de l'élément comprenant une étape d'anodisation suivie d'au moins une étape de colmatage.The elements of the network are applied to the part directly against the structural part of composite material, excluding any intermediate layer. Prior to their mounting on the part, they are advantageously protected against corrosion by a surface protection layer. The latter is formed by a surface treatment of the element comprising an anodizing step followed by at least one clogging step.
Dans des modes de mise en œuvre préférés du procédé de traitement de surface selon l'invention, chaque élément est préparé préalablement à la mise en œuvre de l'étape d'anodisation, notamment par lavage et/ou désoxydation. Le procédé d'anodisation est classique en lui-même. Il peut être mis en œuvre au moyen de tout électrolyte connu en soi. Dans des modes de réalisation préférés de l'invention, il s'agit d'une anodisation dite TSA, dans laquelle l'électrolyte utilisé est un mélange d'acide sulfurique et d'acide tartrique. Un tel traitement est par exemple décrit dans le document EP 1 233 084. Il a pour effet de former à la surface de l'élément, utilisé en tant qu'anode d'une cellule électrolytique, en présence d'une solution aqueuse acide, une couche d'oxyde d'aluminium. La solution aqueuse contient par exemple de 10 à 200 g d'acide sulfurique et de 5 à 200 g d'acide tartrique, en particulier d'acide L(+)-tartrique, par litre de solution. L'utilisation d'un tel mélange de ces acides présente notamment l'avantage de limiter fortement la production de déchets industriels nocifs pour l'environnement, en particulier de déchets contenant du chrome. Ce procédé est également rapide à mettre en œuvre, ce qui résulte en un gain de temps et de coût de fabrication.In preferred embodiments of the surface treatment method according to the invention, each element is prepared prior to the implementation of the anodizing step, in particular by washing and / or deoxidation. The anodizing process is conventional in itself. It can be implemented using any electrolyte known per se. In preferred embodiments of the invention, it is an anodization known as TSA, in which the electrolyte used is a mixture of sulfuric acid and tartaric acid. Such a treatment is for example described in document EP 1 233 084. It has the effect of forming on the surface of the element, used as an anode of an electrolytic cell, in the presence of an acidic aqueous solution, a layer of aluminum oxide. The aqueous solution contains, for example, from 10 to 200 g of sulfuric acid and from 5 to 200 g of tartaric acid, in particular L (+) - tartaric acid, per liter of solution. The use of such a mixture of these acids has the particular advantage of greatly limiting the production of industrial waste harmful to the environment, in particular waste containing chromium. This method is also quick to implement, which results in a saving of time and cost of manufacture.
Les paramètres du procédé d'anodisation sont avantageusement choisis, selon des calculs à la portée de l'homme du métier, en fonction de l'épaisseur de la couche de protection souhaitée sur l'élément. Pour l'application préférée de l'invention qui est la protection contre les effets de la foudre des pièces d'aéronefs, la couche de protection sur chaque élément présente de préférence une épaisseur comprise entre 2,5 et 5 μm.The parameters of the anodizing process are advantageously chosen, according to calculations within the abilities of those skilled in the art, as a function of the thickness of the desired protection layer on the element. For the preferred application of the invention which is the protection against the effects of lightning of aircraft parts, the protective layer on each element preferably has a thickness between 2.5 and 5 microns.
A titre d'exemple, des plages de paramètres opératoires particulièrement avantageuses dans le cadre de l'invention sont les suivantes.By way of example, particularly advantageous ranges of operating parameters in the context of the invention are as follows.
La tension appliquée dans la cuve est de préférence comprise entre 10 et 30 V, la température entre 25 et 43 0C. La durée totale de cycle est comprise entre 5 et 30 min.The voltage applied in the tank is preferably between 10 and 30 V, the temperature between 25 and 43 0 C. The total cycle time is between 5 and 30 min.
Une ou deux étapes de colmatage sont ensuite réalisées sur la couche d'oxyde d'aluminium, de manière à développer la résistance à la corrosion de l'élément.One or two clogging steps are then performed on the aluminum oxide layer, so as to develop the corrosion resistance of the element.
Le colmatage peut être réalisé par un trempage dans de l'eau à une température au moins égale à 96 0C, pendant une durée qui est fonction de l'épaisseur de la couche de protection obtenue par anodisation, par exemple de 30 minutes.The clogging may be carried out by dipping in water at a temperature of at least 96 ° C., for a time which is a function of the thickness of the protective layer obtained by anodization, for example 30 minutes.
Dans d'autres modes de réalisation préférés de l'invention, le traitement hydrothermal décrit ci-avant est réalisé dans de l'eau contenant des composés tensioactifs, et il est précédé d'une étape préalable de colmatage par immersion dans une solution aqueuse de sels métalliques à environ 10% en volume, contenant notamment un sel de Chrome III, à une température de 20 à 40 0C, pendant 2 à 15 minutes.In other preferred embodiments of the invention, the hydrothermal treatment described above is carried out in water containing surfactant compounds, and it is preceded by a prior step of clogging by immersion in an aqueous solution of metal salts with about 10% by volume, containing in particular a salt of Chromium III, at a temperature of 20 to 40 0 C, during 2 to 15 minutes.
L'élément d'alliage d'aluminium ainsi obtenu présente une bonne conductivité électrique et une faible masse surfacique, si bien qu'il est tout à fait adapté pour former un réseau de protection à la fois léger et efficace contre les effets des impacts de foudre pour des pièces de structure d'aéronefs.The aluminum alloy element thus obtained has good electrical conductivity and low weight per unit area, so that it is entirely suitable for forming a protective network that is both light and effective against the effects of the impacts of lightning for aircraft structural parts.
Ses propriétés de résistance à la corrosion ont été évaluées par la mise en œuvre du test décrit ci-après.Its corrosion resistance properties were evaluated by the implementation of the test described below.
Des plaques de métal expansé en alliage d'aluminium, de dimensions de 60 mm par 60 mm, présentant une épaisseur de 100 μm, une masse surfacique de 100 g/m2, et une conductivité électrique de 500 Siemens/m, ont été utilisées.Expanded aluminum alloy metal plates, 60 mm by 60 mm in size, having a thickness of 100 μm, a surface density of 100 g / m 2 , and an electrical conductivity of 500 Siemens / m, have been used.
Une de ces plaques, désignée Plaque Comparative, a été utilisée telle quelle, sans protection particulière contre la corrosion.One of these plates, called Comparative Plate, was used as it was, without any particular protection against corrosion.
Une deuxième plaque, désignée Plaque 1 , a été soumise à un traitement anticorrosion par anodisation suivie d'une étape de colmatage par traitement hydrothermal, selon les conditions énoncées ci-avant. Cette plaque a tout d'abord été soumise, de façon classique, à des opérations de lavage et de dégraissage. L'anodisation a été réalisée dans une cellule électrolytique, dans laquelle la cathode était formée en acier inoxydable et présentait une surface au moins égale à celle de la plaque, avec des paramètres opératoires choisis dans les plages suivantes. L'anodisation a été réalisée en présence d'acide sulfurique et d'acide tartrique dans des concentrations de 40 g/l pour l'acide sulfurique et 90 g/l pour l'acide tartrique, à une température comprise entre 35 et 38 0C, sous une tension de 15 V, pendant une durée de cycle de 25 minutes.A second plate, designated Plate 1, was subjected to anticorrosion treatment by anodization followed by a sealing step by hydrothermal treatment, according to the conditions stated above. This plate was first subjected, in a conventional manner, to washing and degreasing operations. The anodization was carried out in an electrolytic cell, in which the cathode was formed of stainless steel and had a surface at least equal to that of the plate, with operating parameters selected in the following ranges. The anodization was carried out in the presence of sulfuric acid and tartaric acid in concentrations of 40 g / l for sulfuric acid and 90 g / l for tartaric acid, at a temperature between 35 and 38 ° C. C, at a voltage of 15 V, for a cycle time of 25 minutes.
La plaque a été rincée à l'eau, puis soumise au colmatage. Ce dernier a été réalisé par immersion de la plaque dans de l'eau déminéralisée à une température au moins égale à 96 0C, pendant une durée de 30 minutes.The plate was rinsed with water and then clogged. The latter was carried out by immersion of the plate in demineralized water at a temperature of at least 96 ° C. for a period of 30 minutes.
On a ainsi obtenu sur la Plaque 1 une couche superficielle imperméable d'hydroxyde d'aluminium, présentant une épaisseur comprise entre 2,5 et 5 μm.An impervious surface layer of aluminum hydroxide having a thickness of between 2.5 and 5 μm was thus obtained on Plate 1.
Une dernière plaque, désignée Plaque 2, a été soumise à un traitement anticorrosion par une étape d'anodisation suivie d'une étape de colmatage dans une solution aqueuse de sels métalliques, puis d'une étape de colmatage par traitement hydrothermal en présence d'additifs de type tensioactif.A last plate, called Plate 2, was subjected to an anticorrosion treatment by an anodizing step followed by a step of clogging in an aqueous solution of metal salts, then a clogging step by hydrothermal treatment in the presence of surfactant type additives.
L'anodisation a été mise en œuvre selon le procédé exposé pour laThe anodization was carried out according to the process described for the
Plaque 1. La première étape de colmatage a été réalisée par immersion de l'élément dans une solution aqueuse à base de sels métalliques à environ 10 % en volume, contenant notamment un sel de Chrome III, à une température de 40 0C, pendant 10 minutes. Cette étape a été suivie d'une seconde étape de colmatage par traitement hydrothermal, en présence d'agents tensioactifs.Plate 1. The first clogging step was carried out by immersing the element in an aqueous solution based on metal salts at approximately 10% by volume, containing in particular a chromium III salt, at a temperature 40 0 C, for 10 minutes. This step was followed by a second step of clogging by hydrothermal treatment, in the presence of surfactants.
On a obtenu sur la Plaque 2 une couche superficielle imperméable d'hydroxyde d'aluminium, présentant une épaisseur de 2,5 à 5 μm. Des pièces en matériau composite à base de fibres de carbone dans une résine organique époxy ont été fabriquées de façon classique, par exemple par un procédé mettant en œuvre un moule dans lequel sont déposés des plis successifs de fibres pré-imprégnées de résine, et par cuisson dans des conditions de température et de pression assurant la réticulation de la résine et le compactage des plis.An impervious surface layer of aluminum hydroxide having a thickness of 2.5 to 5 μm was obtained on Plate 2. Parts made of composite material based on carbon fibers in an organic epoxy resin have been manufactured conventionally, for example by a process using a mold in which successive folds of fibers pre-impregnated with resin are deposited, and by baking under conditions of temperature and pressure ensuring the crosslinking of the resin and the compacting of the folds.
Chacune des plaques décrites ci-avant a été soumise à un essai de Brouillard Salin, seule ou maintenue en contact, notamment par pression mécanique, sur la surface d'une telle pièce en matériau composite.Each of the plates described above was subjected to a salt spray test alone or kept in contact, in particular by mechanical pressure, on the surface of such a piece of composite material.
Cet essai a été réalisé de manière connue en soi, conformément à la procédure exposée dans la Norme NF ISO 9227. Les plaques ont été exposées, pendant un temps prédéterminé, à un brouillard d'une solution aqueuse de chlorure de sodium, puis le niveau de corrosion de la pièce a été évalué au terme de cette durée d'exposition.This test was carried out in a manner known per se, in accordance with the procedure set out in Standard NF ISO 9227. The plates were exposed, for a predetermined time, to a mist of an aqueous solution of sodium chloride, then the level corrosion of the part was evaluated at the end of this exposure time.
Un premier essai de Brouillard Salin a été réalisé sur chacune des plaques isolées, pendant une durée d'exposition de 1 000 heures. Un second essai a été réalisé sur chacune des plaques en contact direct avec une pièce en matériau composite à base de carbone, pendant une durée d'exposition deA first salt spray test was carried out on each of the isolated plates for a duration of exposure of 1000 hours. A second test was carried out on each of the plates in direct contact with a piece of carbon-based composite material, during a period of exposure of
500 heures.500 hours.
Le niveau de corrosion a été observé visuellement, et qualifié de : - « Sans » si aucune piqûre de corrosion n'est apparue sur la plaque,The level of corrosion was observed visually, and described as: - "Without" if no pitting of corrosion appeared on the plate,
- « Faible » si quelques piqûres de corrosion sont apparues sur la plaque,- "Low" if some pits of corrosion appeared on the plate,
- « Elevé » si de nombreuses piqûres de corrosion sont apparues sur l'ensemble de la plaque (corrosion généralisée). Les résultats de ces essais sont montrés dans le Tableau 1 ci-après.- "High" if many pits of corrosion have appeared on the whole plate (generalized corrosion). The results of these tests are shown in Table 1 below.
Figure imgf000014_0001
Figure imgf000014_0001
Tableau 1 - Niveau de corrosion observé en essai de Brouillard SalinTable 1 - Corrosion Level Observed in Salt Spray Test
Comme on peut l'observer dans ce tableau, les Plaques 1 et 2, correspondant à un traitement par anodisation TSA suivie de respectivement une et deux étapes de colmatage, présentent des performances élevées en terme de résistance anti-corrosion, et supérieures à celles de la Plaque Comparative 1 non traitée.As can be seen in this table, Plates 1 and 2, corresponding to a treatment by TSA anodization followed by respectively one and two sealing steps, have high performances in terms of anti-corrosion resistance, and superior to those of Comparative Plaque 1 untreated.
Ce résultat est obtenu y compris lorsque les plaques sont en contact direct avec une pièce en matériau composite à base de fibres de carbone. En particulier, la Plaque 2, ayant été soumise à deux étapes de colmatage successives, s'avère tout à fait performante du point de vue de la résistance anticorrosion. Les Plaques 1 et 2 présentent une masse surfacique sensiblement inchangée par rapport aux plaques avant tout traitement de surface, c'est-à- dire d'environ 100 g/m2. Leur conductivité électrique reste bonne, et adéquate pour constituer une protection efficace contre les effets des impacts de foudre pour des panneaux de structure d'aéronefs susceptibles d'être exposés à de tels impacts.This result is obtained even when the plates are in direct contact with a piece of composite material based on carbon fibers. In particular, the plate 2, having been subjected to two successive sealing steps, is quite efficient from the point of view of corrosion resistance. Plates 1 and 2 have a substantially unchanged surface mass relative to the plates prior to any surface treatment, i.e., about 100 g / m 2 . Their electrical conductivity remains good, and adequate to provide effective protection against the effects of lightning strikes for aircraft structural panels that may be exposed to such impacts.
La description ci-avant illustre clairement que par ses différentes caractéristiques et leurs avantages, la présente invention atteint les objectifs qu'elle s'était fixés. En particulier, elle fournit des pièces de structure d'aéronef en matériau composite à base de fibres de carbone, qui comportent un réseau d'éléments en alliage d'aluminium les protégeant efficacement contre la foudre, de faible masse surfacique et résistant aux risques de corrosion au contact du carbone. The above description clearly illustrates that by its different characteristics and advantages, the present invention achieves the objectives it has set for itself. In particular, it provides aircraft structure parts made of carbon fiber composite material, which comprise a network of aluminum alloy elements that effectively protect them against lightning, have a low weight per unit area and are resistant to the risk of damage. corrosion on contact with carbon.

Claims

REVENDICATIONS
1. Pièce de structure d'aéronef formée d'une partie structurale en matériau composite à base de fibres de carbone, qui comporte sur une face de ladite partie structurale, au moins sur un côté de la pièce susceptible d'être soumis à des impacts de foudre, un réseau d'éléments électriquement conducteurs, caractérisée en ce que lesdits éléments sont formés en aluminium ou en alliage d'aluminium et présentent en surface une couche de protection anticorrosion d'hydroxyde d'aluminium résultant d'un traitement de surface desdits éléments par une étape d'anodisation suivie d'au moins une étape de colmatage, et en ce qu'ils sont en contact direct avec ladite partie structurale en matériau composite.1. Aircraft structure part formed of a structural part made of composite material based on carbon fibers, which comprises on one side of said structural part, at least on one side of the part likely to be subjected to impacts. lightning conductor, an array of electrically conductive elements, characterized in that said elements are formed of aluminum or aluminum alloy and have on the surface a corrosion protection layer of aluminum hydroxide resulting from a surface treatment of said elements by an anodizing step followed by at least one clogging step, and in that they are in direct contact with said structural part made of composite material.
2. Pièce selon la revendication 1 , caractérisée en ce que la couche d'hydroxyde d'aluminium résulte d'un traitement de surface desdits éléments par une étape d'anodisation réalisée au moyen d'un mélange d'acide sulfurique et d'acide tartrique.2. Part according to claim 1, characterized in that the aluminum hydroxide layer results from a surface treatment of said elements by an anodizing step carried out using a mixture of sulfuric acid and acid tartaric.
3. Pièce selon la revendication 1 ou 2, caractérisée en ce que la couche d'hydroxyde d'aluminium résulte d'un traitement de surface desdits éléments par une étape d'anodisation suivie d'une unique étape de colmatage par traitement hydrothermal.3. Part according to claim 1 or 2, characterized in that the aluminum hydroxide layer results from a surface treatment of said elements by an anodizing step followed by a single step of sealing by hydrothermal treatment.
4. Pièce selon la revendication 1 ou 2, caractérisée en ce que la couche d'hydroxyde d'aluminium résulte d'un traitement de surface desdits éléments par une étape d'anodisation suivie d'une première étape de colmatage par immersion dans une solution aqueuse à base de sels métalliques, contenant de préférence un sel de Chrome III, et d'une seconde étape de colmatage par traitement hydrothermal en présence d'agents tensioactifs.4. Part according to claim 1 or 2, characterized in that the aluminum hydroxide layer results from a surface treatment of said elements by an anodizing step followed by a first step of sealing by immersion in a solution aqueous metal salt based, preferably containing a salt of chromium III, and a second clogging step by hydrothermal treatment in the presence of surfactants.
5. Pièce selon l'une quelconque des revendications 1 à 4, caractérisée en ce que les éléments de réseau sont des métaux déployés, des grillages ou des feuilles minces, le cas échéant perforées.5. Part according to any one of claims 1 to 4, characterized in that the network elements are expanded metals, meshes or thin sheets, where appropriate perforated.
6. Pièce selon l'une quelconque des revendications 1 à 5, caractérisée en ce que ladite couche de protection anticorrosion présente une épaisseur comprise entre 2,5 et 5 μm.6. Part according to any one of claims 1 to 5, characterized in that said anticorrosion protection layer has a thickness between 2.5 and 5 microns.
7. Procédé de fabrication d'une pièce selon l'une quelconque des revendications 1 à 6, comprenant des étapes dans lesquelles :A method of manufacturing a part according to any one of claims 1 to 6, comprising steps in which:
- des éléments de réseau en aluminium ou en alliage d'aluminium sont soumis à un traitement de surface par une étape d'anodisation suivie d'au moins une étape de colmatage, de manière à former sur leur surface ladite couche de protection anticorrosion,- Aluminum or aluminum alloy network elements are subjected to a surface treatment by an anodizing step followed by at least one sealing step, so as to form on their surface said anticorrosion protection layer,
- lesdits éléments sont appliqués en réseau directement contre au moins ladite face de ladite partie structurale en matériau composite sur ledit côté de la pièce susceptible d'être soumis à des impacts de foudre.said elements are applied in an array directly against at least said face of said structural part made of composite material on said side of the part likely to be subjected to lightning strikes.
8. Procédé selon la revendication 7, caractérisé en ce que ladite étape d'anodisation est réalisée au moyen d'un mélange d'acide sulfurique et d'acide tartrique.8. Process according to claim 7, characterized in that said anodizing step is carried out using a mixture of sulfuric acid and tartaric acid.
9. Procédé selon la revendication 7 ou 8, caractérisé en ce que ladite étape d'anodisation est suivie de deux étapes de colmatage. 9. The method of claim 7 or 8, characterized in that said anodizing step is followed by two clogging steps.
PCT/EP2009/067083 2008-12-15 2009-12-14 Aircraft part made of a composite material with aluminium protection against the effects of lightning WO2010069922A1 (en)

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EP2746161A1 (en) 2012-12-21 2014-06-25 EADS Construcciones Aeronauticas, S.A. Lightning resistant aircraft structure
CN106757264A (en) * 2016-11-23 2017-05-31 南昌航空大学 A kind of aluminum alloy environment-friendly type temperature anodic oxidation electrolyte wide and method for oxidation
CN109457145A (en) * 2018-12-25 2019-03-12 有研工程技术研究院有限公司 A kind of ultra-thin breadth lightning protection micropore aluminium net and preparation method thereof

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WO2006069997A1 (en) * 2004-12-30 2006-07-06 Airbus España, S.L. Device for electrical bonding of electrical cables shielding on composite structures
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