MULTIAXIAL FIBROUS PANEL CONTAINING METALLIC ELEMENTS FOR THE PRODUCTION OF A PART IN COMPOSITE MATERIAL

Abstract

The present invention relates to a multiaxial fiber web (10) for manufacturing a composite material part (100) for a turbomachine, particularly an aircraft turbomachine. The multiaxial fiber web (10) is formed by stacking several layers of fibers (12, 14, 16), each layer comprising unidirectional fibers (12a, 14a, 16a) oriented in directions different from the fibers (12a, 14a, 16a) of the other fiber layers (12, 14, 16). The fiber layers (12, 14, 16) are connected to each other by bonding wires (18), wherein at least one of the fiber layers (12, 14, 16) incorporates metallic elements (40) configured to dissipate an electric current generated by a lightning strike on the multiaxial fiber web (10). (Shortened figure: Figure 4)

Description

Title of the invention: MULTIAXIAL FIBER FABRIC CONTAINING METALLIC ELEMENTS FOR THE PRODUCTION OF A PART MADE OF COMPOSITE MATERIAL Technical field of the invention

[0001] The present invention relates to the general field of composite material parts (for example, for a turbomachine or a propulsion assembly, particularly for an aircraft). More particularly, these composite material parts are non-electrically conductive (or weakly conductive) and are susceptible to being subjected to lightning strikes during their use.

[0002] The present invention also relates to a multiaxial fibrous web comprising metallic elements (playing the role of electrical conductor) for the production of the aforementioned composite material parts, and a method for manufacturing such a multiaxial fibrous web. Technical background

[0003] In the aeronautical or wind energy sectors, certain parts that may be exposed to lightning clouds must be designed to withstand a direct lightning strike. For example, these parts include turbomachine blades (particularly unshrouded blades), turbomachine casings, or nacelle cowlings.

[0004] Furthermore, an increasing number of parts, particularly in the aeronautical sector, are being made of composite materials (such as polymers or ceramics). The use of composite materials is particularly advantageous because they allow for a reduction in component mass combined with good mechanical properties.

[0005] A commonly used composite material comprises a matrix-densified fibrous reinforcement. The fibrous reinforcement can be produced by three-dimensional (3D) weaving or by stacking (or draping) and superimposing several layers / plies (multilayer). It is also known to produce the composite material from multiaxial fiber webs. These multiaxial fiber webs are generally obtained by superimposing unidirectional layers, that is, layers made of yarns or fibers oriented essentially in a single direction. These layers are superimposed with different directions and joined together by seams. The matrix can be obtained by transforming a resin, for example, by heat treatment. The resin can be injected into a fibrous preform (corresponding to the fibrous reinforcement without matrix densification), or the fibrous preform can be pre-impregnated with the resin (also referred to as "pre-impregnated" or "prepreg").

[0006] However, composite materials can have the major drawback of low electrical conductivity. Therefore, a metallic material (having better electrical conductivity) is generally bonded to the surface of a composite material part to help dissipate an electric current generated by a lightning strike.

[0007] Fig. 1 illustrates a first example of a multiaxial fibrous sheet 10 for the production of a part 100 in composite material. This multiaxial fiber web 10 is thus formed by a stacking of several layers of fibers 12, 14, 16. Each of the fiber layers 12, 14, 16 comprises unidirectional fibers 12a, 14a, 16a oriented in directions different from the fibers 12a, 14a, 16a of the other fiber layers 12, 14, 16. These fiber layers 12, 14, 16 are connected to each other by bonding wires 18. The multiaxial fiber web 10 further includes a lightning protection coating 4 arranged on an external surface of an upper layer 12 of fibers of the multiaxial fiber web 10. This coating 4 is in the form of metallic fabric or mesh. Thus, the fiber layers 12, 14, 16 have a structural function and the coating 4 has a lightning protection function.

[0008] However, this type of anti-lightning coating is generally not very deformable and may therefore not facilitate the production of parts with complex geometry (such as the aerodynamic shape of turbomachine blades).

[0009] By way of example, the lightning-resistant coating 4 is generally positioned between the top layer 12 of fibers and a manufacturing mold, and the final part is then obtained after densification of the matrix. When the manufacturing mold has a complex geometry (corresponding to that of the part to be produced), the lightning-resistant coating 4 can be fragile and complex to position, and also difficult to keep in place within the manufacturing mold.

[0010] With reference to [Fig. 2], another solution is to make part 100 from composite material with an additional fabric 11 that incorporates the lightning protection coating 4. This fabric 11 is obtained by co-weaving a mixture of metallic yarns 42 and composite yarns 1. This fabric 11 is also located on the external surface of the fibrous reinforcement of part 100, to achieve a dual structural and lightning protection function. However, this solution requires an additional fabric, which can complicate the production of the part from composite material (i.e., the additional use of materials, operations, tooling, etc.) and increase the weight of the composite part. Indeed, a woven fabric can be heavier than a multiaxial fibrous web for an equivalent gain in stiffness. Thus, this solution may not be sufficient for integrating a reliable lightning protection solution into a part from composite material, nor may it be easy to manufacture.

[0011] Consequently, there is a need to enhance the protection against lightning strikes of a multiaxial fibrous sheet for the production of a part made of composite material, while maintaining a reduced mass. Summary of the invention

[0012] The present invention proposes a simple, effective and economical solution to the aforementioned disadvantages of the prior art.

[0013] To this end, the invention proposes a multiaxial fiber sheet for the production of a part in composite material, the multiaxial fiber sheet being formed by a stacking of several layers of fibers, each of the layers of fibers comprising unidirectional fibers oriented in directions different from the fibers of the other layers of fibers, the layers of fibers being connected to each other by connecting threads.

[0014] According to the invention at least one of the fiber layers incorporates metallic elements configured to dissipate an electric current generated by a lightning strike on the multiaxial fiber sheet.

[0015] In the present application, a multiaxial fibrous web (also known as "Non Crimp Fabric", NCF) can be defined as a textile fabric having several layers of unidirectional fibers, that is, fibers oriented essentially in a single direction, these fiber layers being superimposed with different directions and bonded together by binding threads (such as sewing or knitting threads). These fiber layers are therefore generally non-woven.

[0016] The multiaxial fiber mat solution of the invention makes it possible to achieve the aforementioned objective. To this end, the invention proposes directly integrating metallic elements into at least one of the fiber layers (in particular the one(s) located on the outer surface) of the multiaxial fiber mat to make this or these fiber layers electrically conductive. Thus, when the multiaxial fiber mat is subjected to a lightning strike during operation, the electrical current generated by the lightning is dissipated more easily through the metallic elements of this or these fiber layers. This significantly improves the resistance of the multiaxial fiber mat to a lightning strike.

[0017] Thus, this lightning protection improves the behavior of the fiber layers with respect to lightning, particularly when the fiber layers comprise carbon fibers or a mixture of carbon fibers and fibers such as glass or Kevlar®. Indeed, carbon fibers are electrically conductive, but they exhibit high contact resistance to electric current. The metallic elements of the fiber layer(s) (particularly on the surface of the part) exhibit low contact resistance to electric current, especially more weaker than that of the composite material's fibers. This contributes to better electrical current transmission from lightning strikes through the fibers, particularly carbon fibers, via multiple contact points between the metal and the fibers. In this way, the multiaxial fiber web is not (or only very slightly) damaged by lightning.

[0018] Integrating the metallic elements directly into the multiaxial fiber sheet reduces the need for additional components, such as a structural and conductive fabric (i.e., made of composite material) and / or a separate metallic coating for lightning protection. In this way, the multiaxial fiber sheet is less bulky and takes up less space during operation.

[0019] Furthermore, this integration of metallic elements is simple to implement during the manufacturing of the multiaxial fiber web (particularly in an automated manner), robust, and difficult to damage during operation. In particular, the invention proposes to simultaneously form the metallic elements and the fibers within at least one layer of fibers, notably by draping. This improves the positioning and retention of the metallic elements within the multiaxial fiber web.

[0020] Furthermore, the metallic elements according to the configuration of the invention are preferably not rigidly bonded to each other, such as in the manner of a wire mesh or a stretched strip. This allows the multiaxial fibrous web to retain flexibility and deformability, enabling the creation of complex geometries.

[0021] The invention therefore has the advantage of being based on a simple design, offering very high reliability, and little penalizing in terms of cost and size of the part made of composite material.

[0022] The multiaxial fibrous web according to the invention may comprise one or more of the following features, taken individually or in combination with each other:

[0023] - the multiaxial fibrous web further comprises at least one metal strip covering and running along at least one edge of said multiaxial fibrous sheet;

[0024] - the metallic elements are held by the connecting wires;

[0025] - the metallic elements are integrated into the surface of said at least one of the layers of fibers;

[0026] - multiaxial fibrous web comprises an upper layer of fibers and a layer lower layer of fibers, and possibly at least one intermediate layer between said upper and lower layers, said metallic elements being integrated into said upper layer of fibers;

[0027] - said metallic elements are integrated into several or all of the layers of fibers of said multiaxial fibrous sheet;

[0028] - said metallic elements of one of the fiber layers are oriented along a direction different from that of the metallic elements of one or the other of the fiber layers;

[0029] - said metallic elements are oriented parallel to the fibers of said au minus one of the fiber layers;

[0030] - said metallic elements are metallic wires and / or metallic ribbons;

[0031] - said metallic ribbons are located on an upper face of the layer upper layer of fibers, or between the upper layer and one of the fiber layers adjacent to this upper layer;

[0032] - each of said metal elements and of the metal strip is made of aluminum, bronze or copper;

[0033] — the fibers are glass fibers, carbon fibers, aramid fibers, polyamide fibers, ceramic fibers (such as silicon carbide, glass, or aramid), metallic fibers, oxide fibers, or a mixture of at least two of these fibers;

[0034] — the fibers are carbon fibers or a mixture of carbon fibers and fiberglass and / or Kevlar®.

[0035] The invention also relates to a composite part comprising a fibrous reinforcement densified by a matrix. The fibrous reinforcement comprises at least one multiaxial fibrous layer according to one of the features of the invention.

[0036] The composite part can be for a turbomachine, in particular for aircraft.

[0037] By way of example, the composite part could be a turbomachine blade, a housing of turbomachine or in general any part of a turbomachine (or of an aircraft propulsion assembly) that may be struck by lightning.

[0038] The invention also relates to a turbomachine, in particular for an aircraft, comprising at least one part made of composite material according to the invention.

[0039] The invention may also relate to a propulsion system for an aircraft comprising a turbomachine and a nacelle surrounding at least a portion of the turbomachine. The turbomachine and / or the nacelle may include at least one part made of composite material according to the invention.

[0040] The invention further relates to a method for manufacturing a multiaxial fibrous web according to one of the features of the invention, the method comprising the following steps: (a) positioning several unidirectional fibers parallel to each other to form one of said fiber layers along a first direction, (b) repeating step (a) and superimposing on the previous fiber layer of step (a) along a second direction different from the first direction, and (c) joining said fiber layers together by joining wires.

[0041] The process includes integrating said metallic elements into said at least one of the fiber layers in step (a).

[0042] The method according to the invention simplifies and makes more robust the integration of the lightning protection function into a multiaxial fiber mat. To this end, metallic elements are positioned simultaneously with the fibers to form the fiber layer(s) that dissipate the electrical current generated by a lightning strike. This can be achieved by depositing metallic elements (in the form of wires or ribbons, for example) using methods similar to those used to deposit the structural fibers of the fiber layers. These metallic elements can be unwound and arranged on a manufacturing table from specific reels, or the metallic elements may have been previously bonded to structural fibers (such as glass and / or carbon) for co-winding onto a reel.

[0043] Furthermore, this process is suitable for automated (e.g., by a suitable machine) or manual manufacturing of the multiaxial fiber web. In particular, at least one of the process steps can be carried out automatically.

[0044] The manufacturing process according to the invention may include one or more of the following features, taken individually or in combination with each other:

[0045] — at least one of the steps among steps (a) to (c) is carried out manually or automatically with a suitable machine;

[0046] — the fibers each comprise glass fibers, carbon fibers, fibers aramid, polyamide fibers, ceramic fibers (such as silicon carbide, glass, or aramid), metallic fibers, oxide fibers, or a mixture of at least two of these fibers;

[0047] — the metallic elements are chosen from copper, aluminum, bronze, etc.;

[0048] — the metallic elements have circular cross-sections (such as in the case of wires metallic) or rectangular (such as in the case of metallic ribbons) or a mix of these two sections;

[0049] — the metallic elements are arranged within the multiaxial fibrous sheet between bonding points (called thickness penetration points, particularly of the fiber layers) of the bonding wires, so that the metallic elements can slide during the shaping by layering (or draping) of the fiber layers. Brief description of the figures

[0050] The invention will be better understood and other details, features and advantages of the invention will become more apparent upon reading the following description, given by way of non-limiting example and with reference to the accompanying drawings in which:

[0051] [Fig.1] schematically represents a lightning protection coating arranged on a multiaxial fibrous sheet according to a first example of the prior art;

[0052] [Fig.2] schematically represents a fabric woven with metallic threads according to a second example of the prior art;

[0053] [Fig.3] is a schematic perspective view of an aircraft turbomachine according to the invention;

[0054] [Fig.4] schematically represents a multiaxial fibrous sheet incorporating metallic elements according to a first embodiment of the invention;

[0055] [Fig.5] schematically represents a first variant of the embodiment of the multiaxial fibrous sheet of the first embodiment of the invention;

[0056] [Fig.6] schematically represents a second variant of the embodiment of the multiaxial fibrous sheet of the first embodiment of the invention;

[0057] [Fig.7] schematically represents a multiaxial fibrous sheet incorporating metallic elements according to a second embodiment of the invention;

[0058] [Fig.8] schematically represents a multiaxial fibrous sheet incorporating metallic elements according to a third embodiment of the invention;

[0059] [Fig.9] is a schematic axial cross-section view of the multiaxial fibrous sheet of [Fig.8];

[0060] [Fig. 10] schematically represents a variant embodiment of the multiaxial fibrous sheet of the third embodiment of the invention;

[0061] [Fig.1 1] is a block diagram of a manufacturing process for the multiaxial fibrous web of the invention.

[0062] Elements having the same functions in the different implementations have the same references in the figures. Detailed description of the invention

[0063] By convention, in the following description, the terms "longitudinal" and "axial" refer to the orientation of structural elements extending along a longitudinal axis (such as that of a multiaxial fibrous sheet). The terms "radial" or "vertical" refer to an orientation of structural elements extending in a direction perpendicular to the longitudinal axis. The terms "interior" and "exterior," and "internal" and "external," are used with reference to positioning relative to the longitudinal axis. Thus, a structural element extending along the longitudinal axis has an interior face facing the longitudinal axis and an exterior surface opposite its interior surface.

[0064] Figures 1 and 2 have been described in the technical background of this application, and they illustrate examples of lightning protection solutions according to prior art for a part made of composite material, such as for an aircraft turbomachine.

[0065] The present invention applies generally and not limited to a turbomachine 1, in particular an aircraft turbomachine, illustrated for example in [Fig.3]. The turbomachine may be a turbojet, a turboprop or a turboshaft engine.

[0066] The turbomachine 1 can be integrated into an aircraft propulsion assembly 10 comprising a nacelle 5 surrounding the turbomachine 1. The nacelle 5 can include one or more cowlings 50, 52, 54 that can surround at least one of the turbomachine modules. Each nacelle cowling can be a single-piece, annular cowling or semi-cylindrical half-cowls hinged together. In particular, the nacelle 5 can include an upstream air inlet section (comprising an annular air inlet lip 50), a mid-section (comprising an intermediate annular cowling 52), and a downstream section (comprising an annular thrust reverser cowling 54).

[0067] The turbomachine 1 can extend around a longitudinal axis X.

[0068] Such a turbomachine 1 with reference to [Fig.3] may comprise several modules including, from upstream to downstream in a direction F of gas flow, a blower 2a, one or more stages of compressors 2b (for example a low pressure compressor and a high pressure compressor), a combustion chamber 2c, one or more stages of turbine (for example, a high pressure turbine 2e and a low pressure turbine 2f), and optionally a gas exhaust nozzle.

[0069] One or more modules of the turbomachine can be housed within an annular casing extending around the X-axis. For example, the fan 2a can be surrounded by a first annular casing 3a, called the fan casing, and the compressor 2b can be surrounded by a second annular casing 3b, called the intermediate casing. The fan 2a can include movable blades 20a extending around the X-axis and surrounded by the first fan casing 3a. The turbomachine 1 can include outlet guide vanes for the fan 2a, called OGVs (Outlet Guide Vanes), extending around the X-axis. These OGVs are surrounded by the second intermediate casing 3b and are not shown in the figures.

[0070] The turbomachine 1 may include at least one part 100 made of composite material because of their mechanical performance, the possibility of creating complex shapes and the reduction in mass (especially compared to a metallic material).

[0071] By way of example, part 100 may be at least one of the turbomachine blades (such as the 20a blades and / or the OGV blades), unshod turbomachine blades and / or at least one of the annular hoods 50, 52, 54 of the nacelle.

[0072] The composite material part 100 may comprise (or be formed by) a fibrous reinforcement densified by a matrix. This fibrous reinforcement may comprise at least one multiaxial fibrous layer 10.

[0073] Figures 4 to 10 illustrate several examples of a multiaxial fibrous web 10 according to the invention. The multiaxial fibrous web 10 (simplified by the term web below) can extend along: - a first axis A, called the elongation axis (or vertical axis in the figures), - a second axis B, called the longitudinal axis (or horizontal axis in the figures), extending perpendicularly to the first axis A, and - a third axis C, called transverse, extending perpendicularly to the first A and second B axes.

[0074] The multiaxial fibrous sheet 10 can extend axially between first 10a and second 10b edges (with respect to the second axis B). These edges 10a, 10b can have an elongated shape along the third axis C. The multiaxial fibrous sheet 10 can have a first radial dimension (or in other words, thickness) Ei0 measured with respect to the first axis A.

[0075] The multiaxial fibrous sheet 10 is formed by a stacking (in particular along the first axis A) of several layers of fibers 12, 14, 16.

[0076] By way of example, the multiaxial fibrous sheet 10 may include at least one upper layer 12 of fibers and a lower layer 16 of fibers (with respect to axis A), and optionally one or more intermediate layers 14 of fibers arranged between these upper layer 12 and lower layer 16 of fibers.

[0077] Each of the fiber layers 12, 14, 16 comprises unidirectional fibers 12a, 14a, 16a oriented in directions (or, in other words, orientations) different from the fibers 12a, 14a, 16a of the other fiber layers 12, 14, 16. The fibers 12a, 14a, 16a of each of the fiber layers 12, 14, 16 can each be oriented at an orientation angle a[2, aM, ai6]. These orientation angles a[2, ai4, ai6] can vary according to the desired stiffness properties of the multiaxial fiber web 10. Each of the orientation angles a[2, ai6], ai6 can vary between 0° and 90° with respect to the length of the fiber layers (i.e., with respect to axis B or axis C). For example, these orientation angles a[2, aM, ai6 can each be chosen from the values ​​of 0°, +30°, -30°, +45°, -45°, +60°, -60°, +90° and -90°.

[0078] Each of the fiber layers 12, 14, 16 can have a top face 122 (with respect to the first axis A) and a bottom face 124 which is opposite to the top face 122. The figures illustrate the top face 122 and bottom face 124 of the top layer 12 of the multiaxial fiber sheet 10.

[0079] Each of the fiber layers 12, 14, 16 can comprise a thickness E[2, EM, Ei6 measured along the first axis A. The thickness Ei2, Ew, Ei6 can be similar between the fiber layers 12, 14, 16. Alternatively, the thickness E[2, EM, Ei6 of one of the fiber layers can be different from the thickness of one or more of the other fiber layers 12, 14, 16 of the multiaxial fiber web 10.

[0080] Each of the fiber layers 12, 14, 16 may comprise fibers 12a, 14a, 16a which may be selected from glass fibers, carbon fibers, aramid fibers (such as Kevlar®), polyamide fibers, ceramic fibers (such as silicon carbide, aluminum oxide), or a mixture of at least two of these fibers.

[0081] The fiber layers 12, 14, 16 are linked together by bonding threads 18. The bonding threads 18 may extend along the third axis C. The bonding threads 18 may be sewing threads or knitting threads. Each bonding thread 18 may have a distance d[8, corresponding to a sewing or knitting gauge, between two bonding points 180, which may be constant. This distance d[8 may be between 2 and 10 mm. For example, the distance d[8 may be approximately 5 mm. The distance d[8 may be measured along the third axis C.

[0082] One of the features of the invention is that at least one of the fiber layers 12, 14, 16 incorporates metallic elements 40. These metallic elements 40 are configured to dissipate an electric current generated by a lightning strike on the multiaxial fiber web 10.

[0083] The metallic elements 40 can be retained by the connecting wires 18. In other words, the connecting wires 18 allow the metallic elements 40 to be trapped at the same time as the fibers 12a, 14a, 16a in the layer 10. Thus, the metallic elements 40 can be embedded in the corresponding layer(s) of fiber(s).

[0084] Each bonding wire 18 can form a bonding row of the fiber layer(s) 12, 14, 16 and the metal elements 40. Without limitation, the examples in Figures 4 to 6 illustrate six bonding rows from the bonding wires 18 extending along the third axis C. Each bonding wire 18 (or bonding row) can comprise at least two lines of bonding points 180. Preferably, the points 180 can be arranged in a staggered (or zigzag) pattern.

[0085] In particular, the metallic elements 40 can be located on a surface, called external (with respect to the first axis A), of the multiaxial fibrous sheet 10. For example, the metallic elements 40 can be located at least in the upper layer 12 or more particularly at least on the upper face 122 of the upper layer 12.

[0086] Advantageously, these metallic elements 40 can be integrated into a single upper layer 12. Alternatively, the metallic elements 40 can be integrated into several layers of fibers (preferably forming upper layers of the web 10) or into all the fiber layers 12, 14, 16 of the web 10. For example, the upper layer 12 of fibers and one of the fiber layers adjacent to this upper layer 12 can comprise the metallic elements 40. According to another example, the upper layer 12 of fibers and several fiber layers close to this upper layer 12 can comprise the metallic elements 40. Finally, the metallic elements 40 can be integrated into all the fiber layers, particularly when the multiaxial fiber web 10 comprises a limited number of fiber layers 12, 14, 16 (for example, between two and five fiber layers).

[0087] The metallic elements 40 can be oriented in a similar direction to that of the fibers 12a, 14a, 16a of the corresponding fiber layer. In other words, the metallic elements 40 can be oriented parallel to the fibers 12a, 14a, 16a of the corresponding fiber layer. Thus, the metallic elements 40 of one of the fiber layers 12, 14, 16 can be oriented in a different direction from that of the metallic elements 40 of one or more of the other fiber layers 12, 14, 16.

[0088] The metal element 40 can be arranged between at least two fibers 12a, 14a, 16a. Advantageously, the fiber layer(s) comprising the metal elements 40 can include a pitch p402, P404 (or a gap) between two adjacent (or close) metal elements 40, in particular without contact between them. This pitch p402, P404 is measured according to the orientation of the metal elements 40 in the corresponding fiber layer. The distance d[8] can be less than or greater than the pitch p402, p404. The pitch p402, P404 can be between 2 and 15 mm. Preferably, the pitch p402, p404 can be between 3 and 8 mm.

[0089] The metal elements 40 can be arranged between the bonding points 180 of the connecting wires 18. This allows the metal elements 40 to slide during the layering (or draping) of the fiber layers. These points 180 can be designated as thickness penetration points, particularly of the fiber layers 12, 14, 16.

[0090] The metallic elements 40 can be made of aluminium, bronze, copper, etc.

[0091] The metallic elements 40 may each have a circular cross-section (such as in the case of 402 metal wires), a rectangular section (such as in the case of 404 metal tapes) or a mixture of these two sections.

[0092] The metallic elements 40 may be metallic wires 402 and / or metallic ribbons 404. The multiaxial fibrous web 10 may simultaneously comprise the metallic wires 402 and metallic ribbons 404 within the same layer of fibers or at least two adjacent layers of fibers, so as to increase the dissipation of electric current.

[0093] The metal wires 402 can be oriented parallel to the fibers 12a, 14a, 16a of the corresponding fiber layer. This allows the metal wires to be embedded in the corresponding fiber layer.

[0094] The 402 metal wires can have a circular or polygonal cross-section.

[0095] The metal wires 402 can each have a diameter D measured with respect to the First axis A. This diameter D of the 402 metal wire can be identical to the thickness E12, E14, Ei6 of the corresponding fiber layer. Alternatively, the diameter D can be between 0.5 and 1.5 times the thickness E[2, Ew, Ei6 of the fiber layer containing this 402 metal wire. Preferably, the diameter D can be between 0.8 and 1.2 times the thickness E[2, Eu, Ei6 of the corresponding fiber layer.

[0096] The metal wires 402 can be spaced apart from each other by a first pitch p402 measured with respect to the second axis B or the third axis C. This first pitch p402 can be between 2 and 15 mm. Preferably, the first pitch p402 can be between 3 and 8 mm.

[0097] 402 metal wires can be made of aluminium, bronze, copper, etc.

[0098] The 404 metal strips can be flat.

[0099] The metallic ribbons 404 of one of the fiber layers 12, 14, 16 can be oriented along a direction (or orientation) different from that of the 12a, 14a, 16a fibers of the corresponding fiber layer or those of the adjacent fiber layers.

[0100] Each metal ribbon 404 can be located between the 180 bonding (or stitching) points, so that these points 180 pass only through the fiber layers 12, 14, 16 without passing through and piercing the metal ribbon 404.

[0101] Advantageously, the metal ribbons 404 can be located on the surface of the layer 10. For example, the metal ribbons 404 can be on the upper face 122 of the upper layer 12 or between the upper layer 12 (in particular its lower face 124) and one of the layers adjacent to this upper layer 12 (namely the intermediate layer 14 or the lower layer 16 depending on the number of fiber layers composing the layer 10).

[0102] The 404 metal strips may have a second radial dimension E404 (or thickness) measured along the first axis A. This second radial dimension E404 may be between 0.03 and 0.15 mm. Preferably, the second radial dimension E404 may be between 0.05 and 0.10 mm.

[0103] The 404 metal strips may have an axial dimension l404 (or width) measured along the second axis B. This axial dimension l404 may be between 1 and 5 mm. Preferably, the axial dimension l404 may be between 1.5 and 3 mm.

[0104] Preferably, the metal ribbons 404 can be positioned in one or more orientations parallel to the bonding stitch lines 180 that pass through the thickness of the fiber layers 12, 14, 16. Even more preferably, the metal ribbons 404 can be limited in width between two parallel bonding stitch lines 180. In other words, the width 1404 can be identical to the width measured between two bonding stitches 180 of the same bonding row of the bonding yarn 18. Thus, the metal ribbons 404 may not be perforated and therefore not damaged during the bonding (for example, by sewing) of the fiber layers 12, 14, 16 and the metal ribbons 404.

[0105] According to a first example, a set of metal ribbons 404 can be installed in a so-called longitudinal direction (i.e., along the third axis C) parallel to the connecting point lines 180. The metal ribbons 404 are located between two connecting point lines 180. When the metal ribbons 404 are on the upper face 122, they are thus held in place by the zigzag configuration of the connecting wires 18.

[0106] According to a second example, a set of metal strips 404 can be installed in a so-called transverse direction (i.e., along the second axis B), preferably the width l404 of the metal strips 404 being less than the pitch between the connecting points 180 in a zigzag configuration. In this way, the metal strips 404 are held in place by the zigzag configuration of the connecting wires 18.

[0107] According to a third example, a set of metal strips 404 can be installed in a direction between the second B and third C axes so as to be parallel to the connection points 180, preferably in this case, the width l404 of the metal strips 404 is reduced to be less than the distance between two successive lines of connection points 180 in the orientation considered.

[0108] The metal strips 404 can be separated from each other by a second pitch p404. In the case where the metal strips 404 extend at an orientation angle of 0° (as in the first example mentioned above), the second pitch p404 is measured with respect to the second axis B when the metal strips 404 extend along the third axis C (Figures 7 to 10). In the case where the metal strips 404 extend at an orientation angle of 90° (as in the second example mentioned above), the second pitch p404 is measured with respect to the third axis C when the metal strips 404 extend along the second axis B (not shown in the figures).

[0109] The metal ribbons 404 can be arranged between each row of connecting wires 18 (Figures 7 and 9) or between every two to four rows of connecting wires 18 (not shown in the figures).

[0110] The second pitch p404 can be between 2 and 15 mm. Preferably, the second pitch p404 can be between 3 and 8 mm.

[0111] 404 metal ribbons can be made of aluminium, bronze, copper, etc.

[0112] The multiaxial fibrous sheet 10 may further comprise at least one metal strip 406 covering and running along at least one of the first 10a and second 10b edges. Advantageously, the first 10a and second 10b edges may each be covered by the metal strip 406.

[0113] The metal strip 406 may have a third radial dimension E406 equal to or less than the first radial dimension Ei0 of the sheet 10. The third radial dimension E406 is measured along the first axis A.

[0114] The 406 metal strip can be made of aluminium, bronze or copper.

[0115] The metal strip 406 can be attached to the edge(s) 10a, 10b of the sheet 10.

[0116] The metal strip 406 can be in contact with at least part of the metal elements 40. This allows the metal elements 40 of the different layers of fibers 12, 14, 16 to be electrically connected and thus distribute the electrical current to be dissipated.

[0117] The present application will now describe the different possible configurations of the multiaxial fibrous web 10 of the invention with reference to Figures 4 to 10.

[0118] Figures 4 to 6 illustrate a first embodiment of the multiaxial fibrous web 10, in which the metallic elements 40 are metallic wires 402.

[0119] The various characteristics described above with reference to the fiber layers 12, 14, 16, the metal wires 402 and / or the metal strips 406 can be applied to the multiaxial fiber sheet 10 of the first embodiment.

[0120] Figures 4 to 6 illustrate, without limitation, a multiaxial fiber sheet 10 comprising three layers of fibers stacked one on top of the other (along the first axis A) and connected to each other by the bonding strands 18. These three layers of fibers are formed by the upper layer 12 of fibers, the middle layer 14 of fibers, and the lower layer 16 of fibers. The upper layer 12 may have a first thickness E12, the middle layer 14 may have a second thickness EM, and the lower layer 16 may have a third thickness E16. The thicknesses E12, EM, and E16 may be substantially identical in the examples in Figures 4 to 6.

[0121] The fibers 12a, referred to as upper fibers, of the upper layer 12 can each be oriented with an orientation angle a12 of approximately -45° with respect to the second axis B. The fibers 14a, referred to as intermediate fibers, of the intermediate layer 14 can each be oriented with an inclination angle (approximately) of -90° or +90° with respect to the third axis C. The fibers 16a, referred to as lower fibers, of the lower layer 16 can each be oriented with an inclination angle ai6 of approximately +45° with respect to the second axis B. The upper layer 12 forms the outermost fiber layer of the layer 10 and therefore the one most likely to be in direct contact with the lightning strike.

[0122] In the examples in Figures 4 to 6, the upper layer 12 may comprise the metal wires 402. The metal wires 402 may be oriented parallel to the upper fibers 12a. These metal wires 402 may have a circular or polygonal cross-section. In particular, two fibers 12a are arranged between two metal wires 402. Each bonding wire 18 may retain one or two metal wires 402. The diameter D of the metal wires 402 may be substantially equal to the first thickness En of the upper layer 12.

[0123] In the example of [Fig.4], the metal wires 402 are integrated only in the upper layer 12. Thus, the intermediate layers 14 and lower layer 16 do not integrate any metal wires 402. The metal wires 402 can be oriented parallel to the upper fibers 12a, that is to say at an angle of inclination of -45° (with respect to the second axis B).

[0124] As illustrated in Figures 5 and 6, the metal wires 402 are integrated into each of the fiber layers 12, 14, 16 of the web 10. In particular, the metal wires 402 in the intermediate layer 14 can be oriented parallel to the intermediate fibers 14a, i.e., at an angle of inclination ai4 of approximately + / -90° (with respect to the third axis C), and the metal wires 402 in the lower layer 16 can be oriented parallel to the lower fibers 16a, i.e., at an angle of inclination (insensible) of +45° (with respect to the second axis B). This integration of metal wires 402 into several fiber layers 12, 14, 16 creates contact zones Z between the metal wires 402 in the different fiber layers 12, 14, 16 to increase the dissipation of electrical current.These contact zones Z can thus create a mesh (or network) of 402 metal wires which are embedded in the fibers 12a, 14a, 16a of the web 10, so as to distribute the current to be dissipated in the web 10, while preserving the deformability of the web 10.

[0125] As in [Fig. 6], the multiaxial fibrous sheet 10 further comprises the metal strips 406 which are located at the first 10a and second 10b edges of the sheet 10. Each of the metal strips 406 can cover and run along the edges 10a, 10b along the third axis C. Preferably, the metal strips 406 can be in contact with at least part of the metal wires 402 of the fiber layers 12, 14, 16 to increase the contact areas Z.

[0126] Figure 7 illustrates a second embodiment of the multiaxial fibrous web 10 which differs from the web 10 of the first embodiment by the metallic elements 40. In particular, the metallic elements 40 of the web 10 of the second embodiment are metallic ribbons 404.

[0127] The various characteristics described above with reference to the fiber layers 12, 14, 16, the metal ribbons 404 and / or the metal strips 406 can be applied to the multiaxial fiber sheet 10 of the second embodiment.

[0128] [Fig. 7] illustrates, without limitation, the three layers of fibers 12, 14, 16 similar to those of [Fig. 4]. In particular, the upper layer 12 may include the metal ribbons 404. These metal ribbons 404 are located on the surface of the layer 10, preferably on the upper face 122 of the upper layer 12. The metal ribbons 404 are flat.

[0129] The metal ribbons 404 can extend longitudinally along the third axis C. Thus, the metal ribbons 404 extend in a different orientation from that of the upper fibers 12a of the upper layer. Indeed, the upper fibers 12a are oriented with the orientation angle a12 which is approximately -45° and the metal ribbons are oriented with an orientation angle of 0° in the example of [Fig. 7].

[0130] The metal ribbons 404 can be held by the connecting wires 18. In the example of [Fig.7], each connecting wire 18 can hold a single metal ribbon 404.

[0131] The multiaxial fibrous sheet 10 of the second embodiment may also include one or more metal strips 406 on the edges 10a, 10b, as described above in particular with reference to [Fig.6].

[0132] Figures 8 to 10 illustrate a third embodiment of the multiaxial fibrous web which differs from the web 10 of the first and second embodiments by the metallic elements 40. In particular, the metallic elements 40 of the web 10 of the third embodiment comprise both metallic wires 402 and metallic ribbons 404.

[0133] The various characteristics described above with reference to the fiber layers 12, 14, 16, the metal wires 402, the metal ribbons 404 and / or the metal strips 406 can be applied to the multiaxial fiber sheet 10 of the third embodiment.

[0134] Figures 8 to 10 illustrate, without limitation, the three layers of fibers 12, 14, 16 similar to those in Figures 4 and 7. In particular, the top layer 12 can including the metal wires 402 and / or the metal ribbons 404. As described with reference to [Fig. 4], the metal wires 402 are oriented parallel to the upper fibers 12a, in particular at the orientation angle a12 of -45°. The diameter D of the metal wires 402 and the first thickness En of the upper layer 12 may be similar.

[0135] In the example of Figures 8 and 9, the metal ribbons 404 are arranged on the upper face 122 of the upper layer 12 and oriented in a different orientation from that of the upper fibers 12a (as described with reference to [Fig.7]) and from that of the metal wires 402.

[0136] As in [Fig. 10], the metal ribbons 404 can be located between the upper layer 12 and the intermediate layer 14. In particular, the metal ribbons 404 are located between the lower face 124 of the upper layer and an upper face 142 of the intermediate layer 14. The metal ribbons 404 can be oriented with a different orientation from the upper fibers 12a and the intermediate fibers 14a. Indeed, the upper fibers 12a are oriented with an orientation angle of approximately -45°, the intermediate fibers 14a are oriented with an orientation angle of + / -90°, and the metal ribbons 404 are oriented with an orientation angle of 0° (with respect to the third axis C).

[0137] In the examples in Figures 8 to 10, the metal wires 402 and the metal ribbons 404 can be retained by the connecting wires 18. In particular, each connecting wire 18 can retain a single metal ribbon 404 and one or two metal wires 402.

[0138] The simultaneous integration of the metal wires 402 and the metal ribbons 404 also makes it possible to increase the contact areas Z between the metal elements within the same fiber layer or between different fiber layers to enhance the dissipation of the electric current.

[0139] The multiaxial fibrous sheet 10 of the third embodiment may also include one or more metal strips 406 on the edges 10a, 10b, as described above in particular with reference to [Fig.6].

[0140] The present application will now describe a method for manufacturing the multiaxial fibrous web 10 of the invention, the successive steps of which are summarized for example in [Fig. 11].

[0141] According to the invention, the method comprises the following steps: (a) positioning several unidirectional fibers 12a, 14a, 16a parallel to each other to form one of the fiber layers 12, 14, 16 along a first direction, (b) repeating step (a) and superimposing the fiber layer from step (a) onto the previous fiber layer along a second direction different from the first direction, and (c) bonding of the fibre layers 12, 14, 16 together by bonding threads 18.

[0142] Step (b) can be repeated several times so as to form all the layers of fibers 12, 14, 16 stacked one on top of the other of the multiaxial fiber web 10. By way of example, the multiaxial fiber web 10 can comprise between two and five layers of fibers 12, 14, 16.

[0143] Step (b) allows for the stacking of several layers of fibers oriented in different directions.

[0144] In step (a), the process includes the integration of the metallic elements 40 into at least one of the fiber layers 12, 14, 16.

[0145] Depending on the possible configurations of the metallic elements 40 in the layer 10 of the invention, the metallic elements 40 can be positioned (or deposited) parallel to the fibers 12a, 14, 16a of the corresponding fiber layer (case of the metallic wires 402 of figures 4 to 5 and 8 to 10) and / or following a different orientation from that of the fibers 12a, 14a, 16a (case of the metallic ribbons 404 of figures 7 to 10).

[0146] The process of the invention can be adapted for automated (e.g., by a suitable machine) or manual manufacturing of the multiaxial fiber web. In particular, at least one of steps (a) to (c) can be carried out manually or automatically. By way of example, steps (a) and (b) can be carried out by draping.

[0147] The multiaxial fibrous web 10 of the invention can thus be used to produce the part 100 in composite material, for example, by a liquid composite molding technique known as LCM (Liquid Composite Molding), such as a resin transfer molding technique known as RTM (Resin Transfer Molding), or by infusion, such as LRI (Liquid Resin Infusion), RFI (Resin Film Infusion), or by the English term "wet lay-up," also called contact impregnation. For this purpose, one or more webs 10 can be placed and shaped in a manufacturing mold having, for example, the shape of the part to be produced.The densification matrix - or resin - is applied simultaneously or all at once and infiltrated throughout the structures; the composite part is obtained by solidification of the matrix.

[0148] The present application describes the invention above (namely the multiaxial fiber web and the composite material part comprising this multiaxial fiber web) in a non-limiting manner as it applies in a turbomachine, particularly an aircraft turbomachine, or more generally in an aircraft propulsion system. However, the invention can also be applied in a general to any part made of composite material, in particular whose fibrous reinforcement densified by a matrix includes at least one multiaxial fibrous layer.

[0149] The present invention can also be applied in the field of wind turbines (land or sea) which may include parts that are susceptible to being impacted by lightning.

Claims

Demands

1. A multiaxial fiber web (10) for making a part (100) out of composite material, the multiaxial fiber web (10) being formed by a stack of several layers of fibers (12, 14, 16), each of the fiber layers (12, 14, 16) comprising unidirectional fibers (12a, 14a, 16a) oriented in directions different from the fibers (12a, 14a, 16a) of the other fiber layers (12, 14, 16), the fiber layers (12, 14, 16) being connected to each other by bonding wires (18), characterized in that at least one of said fiber layers (12, 14, 16) incorporates metallic elements (40) configured to dissipate an electric current generated by a lightning strike on the multiaxial fiber web (10), the fiber web multiaxial (10) comprises an upper layer (12) of fibers and a lower layer (16) of fibers, and optionally at least one intermediate layer (14) between said upper and lower layers (12, 16),said metallic elements (40) being integrated into said upper layer (12) of fibers, said metallic elements (40) are metallic ribbons (404) and optionally metallic wires (402), and said metallic ribbons (404) are located on an upper face (122) of the upper layer (12) of fibers, or between the upper layer (12) and one of the layers (14, 16) of fibers adjacent to this upper layer (12).

2. Multiaxial fibrous sheet according to claim 1, characterized in that it further comprises at least one metal strip (406) covering and running along at least one edge (100a) of said multiaxial fibrous sheet (10).

3. Multiaxial fibrous mat according to claim 1 or 2, characterized in that the metallic elements (40) are retained by the connecting wires (18).

4. Multiaxial fibrous sheet according to any one of the preceding claims, characterized in that the metallic elements (40) are integrated into the surface of said at least one of the fiber layers (12, 14, 16).

5. Multiaxial fibrous sheet according to any one of claims 1 to 4, characterized in that said elements metallic (40) are integrated into several or all of the fiber layers (12, 14, 16) of said multiaxial fibrous web (10).

6. Multiaxial fibrous sheet according to any one of claims 1 to 5, characterized in that said metallic elements (40) of one of the layers of fibers (12, 14, 16) are oriented in a direction different from that of the metallic elements (40) of one or the other of the layers of fibers (12, 14, 16).

7. Multiaxial fibrous sheet according to any one of the preceding claims, characterized in that said metallic elements (40) are oriented parallel to the fibers (12a, 14a, 16a) of said at least one of the fiber layers (12, 14, 16).

8. Multiaxial fibrous sheet according to any one of claims 1 to 7, characterized in that each of said metal elements (40) and of the metal strip (406) is made of aluminum, bronze or copper.

9. Part (100) of composite material comprising a fibrous reinforcement densified by a matrix, characterized in that said fibrous reinforcement comprises at least one multiaxial fibrous sheet (10) according to any one of the preceding claims.

10. Turbomachine (1), in particular aircraft, comprising at least one part (100) of composite material according to the preceding claim.

11. A method for manufacturing a multiaxial fiber web (10) according to any one of claims 1 to 8, said method comprising the following steps: (a) positioning several unidirectional fibers (12a, 14a, 16a) parallel to each other to form one of said fiber layers (12, 14, 16) along a first direction, (b) repeating step (a) and superimposing on the previous fiber layer of step (a) along a second direction different from the first direction, and (c) joining said fiber layers (12, 14, 16) together by joining wires (18), characterized in that the method comprises integrating said metallic elements (40) into said at least one of the fiber layers (12, 14, 16) in step (a).

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