Method for manufacturing a fiber-reinforced polymer coating

Abstract

[Title] Method for manufacturing a coating made of fiber-reinforced polymer material. Method for manufacturing at least one coating (6) made of a polymer material reinforced with one or more fibers, in particular comprising at least one cylindrical or spherical portion or cylindrical or spherical segment, the method comprising the following steps: - at least one step of winding (100) at least one fiber around a mandrel (M) to form on the mandrel (M) a drape (7) comprising one layer of wound fibers or several layers of wound and superimposed fibers, - at least one step of removing (300) the drape (7) formed from the mandrel (M), and - at least one step of cutting (200) the drape before or after removal from the mandrel (M).

Description

Title of the invention: Method for manufacturing a fiber-reinforced polymer coating Technical field of the invention

[0001] The present invention relates, in general, to the manufacture of coatings intended to be applied to the surface of a part or the surface of a portion of a part of non-deployable shape, such as a spherical surface, for example a ball joint or the housing of a ball joint.

[0002] More specifically, the invention relates to a method for manufacturing a coating made of polymer material reinforced with one or more fibers, in particular comprising at least one portion of cylindrical or spherical shape or at least one portion of cylindrical or spherical segment shape. Prior art

[0003] Traditionally, in the aeronautical field, connectors such as fittings are used. Such connecting parts serve to connect two members in relative ball-and-socket motion by means of a ball joint interposed between said members and integral with the connecting part. This is the case, for example, of a fitting for attaching a thrust reverser cover of an aircraft turbine.

[0004] It is known to provide a lining, more commonly called a "liner" in Anglo-Saxon terms, between the ball joint and the housing in which the ball joint is mounted. Such a liner helps to reduce the impact of repeated stresses generated during ball joint movement.

[0005] Typical prior art coatings used include a woven fiber fabric combined with a polymer binder to form a composite material that can be attached to bearing surfaces.

[0006] Given the spherical shape of the ball joint, the coating must also have a spherical shape.

[0007] It is known to manufacture these fabric coverings from sheets formed by a layer of woven fibers or a flat stacking of layers of woven fibers bonded by a polymer material.

[0008] The sheets are pleated, folded, or even partially cut to give them the shape of the covering to be manufactured.

[0009] However, the pleating of the sheets leads to mechanical weaknesses which greatly impairs the performance of the coating by reducing its mechanical resistance properties.

[0010] Moreover, such a conformation of the sheets remains complex, which hinders automation and industrialization. Summary of the invention

[0011] The invention therefore aims to remedy these drawbacks and to propose a simple method for manufacturing a composite material coating with a fiber-reinforced polymer matrix of non-deployable shape, in particular cylindrical or spherical, which retains the mechanical properties of the coating.

[0012] A method for manufacturing at least one coating made of polymer material reinforced with one or more fibers is therefore proposed, in particular comprising at least one cylindrical or spherical portion or cylindrical or spherical segment, characterized in that it comprises the following steps:

[0013] - at least one winding step of at least one fiber around a mandrel for to form on the mandrel a drape comprising one layer of wound fibers or several layers of wound and superimposed fibers,

[0014] - at least one step of removing the drape from the mandrel, and

[0015] - at least one draping cutting step before or after removal of the mandrel.

[0016] Such a manufacturing process based on filament winding facilitates obtaining a fiber-reinforced polymer matrix composite coating having a complex non-deployable shape, such as cylindrical or spherical, while preserving its mechanical resistance properties.

[0017] Such a manufacturing process becomes faster, reproducible and industrializable.

[0018] In one embodiment, the fiber wound around the mandrel can be pre-impregnated with a thermosetting material, the process further comprising a step of polymerizing the resulting drape.

[0019] In another embodiment, the fiber wound around the mandrel may be partially pre-impregnated with a thermosetting material, or not impregnated with a thermosetting material, the process further comprising:

[0020] - after removal of the mandrel draping, a step of adding thermosetting material on the draping, and

[0021] - a polymerization step of the drape obtained.

[0022] When the fiber is a pre-impregnated, partially pre-impregnated or unimpregnated fiber of a thermosetting material, one or more preforms can be obtained at the end of the draping cutting step.

[0023] According to one feature, the coating to be manufactured can be obtained directly at the end of the polymerization step of the preforms.

[0024] In another embodiment, the fiber wound around the mandrel can be pre-impregnated with a thermoplastic material.

[0025] When the fiber is a pre-impregnated thermoplastic material fiber, one or more preforms can be obtained at the end of the draping cutting step.

[0026] According to one feature, the coating to be manufactured can be obtained directly from the preforms.

[0027] Alternatively, the manufacturing process may include at least one folding step to give a final shape to the preform and obtain the coating to be manufactured, in particular an annular shape.

[0028] The annular-shaped coating can be cylindrical or spherical.

[0029] Advantageously, one or more notches can be formed on the edges of the preforms obtained at the end of the draping cutting step to facilitate the folding of each of the preforms towards the final shape of the covering to be manufactured.

[0030] Preferably, the angle formed between the axis of the mandrel and the fibers within the same layer of fibers of the drape is between 50 and 90°, preferably between 70 and 90°, more preferably between 80 and 90°.

[0031] Alternatively, the angle formed between the axis of the mandrel and the fibers within the same layer of fibers of the drape can be between 0 and 40°, preferably between 0 and 20°, more preferably between 0 and 10°.

[0032] Advantageously, the fiber can be wound around a cylindrical mandrel with a diameter equal to the diameter of a cylindrical or spherical portion of the coating to be manufactured.

[0033] According to one feature, the draping cut can be helical.

[0034] In one embodiment, the fiber can be wound around a mandrel having one or more spherical portions.

[0035] Advantageously, the manufacturing process may include the addition of at least one additional drape or coating of fiber-reinforced polymer material on the drape obtained.

[0036] Preferably, the additional draping or covering is manufactured as previously described.

[0037] More preferably, the additional draping or coating comprises fibers of a different nature from the fibers of the draping obtained on which the addition is made.

[0038] In one embodiment, the fiber can be wound onto a woven fabric positioned between the fiber and the mandrel, the woven fabric being formed of one or more fibers partially or totally pre-impregnated with a thermosetting or thermoplastic polymer material or formed of one or more fibers not impregnated with polymer material.

[0039] In one embodiment, the resulting drape may comprise a plurality of layers of wound and superimposed fibers of different types, preferably comprising at least one layer of fibers made of fibers in polytetrafluoroethylene (PTFE) and carbon and / or glass fibers and at least one layer of fibers made of carbon and / or glass fibers. Brief description of the figures

[0040] Other purposes, advantages and features will become apparent from the following description, given for illustrative purposes only and made with reference to the accompanying drawings on which:

[0041] [Fig-1] is a perspective view of a fitting according to an embodiment of the invention.

[0042] [Fig.2] is a cross-sectional view of the fitting illustrated in [Fig. 1].

[0043] [Fig.3] is a detailed view of the coating of the fitting illustrated in [Fig.2].

[0044] [Fig.4A] illustrates a method for manufacturing a coating made of material thermosetting fiber-reinforced material according to an embodiment of the invention.

[0045] [Fig.4B] illustrates a method for manufacturing a fiber-reinforced thermoplastic coating according to another embodiment of the invention.

[0046] [Fig. 5] illustrates a filament winding step of a manufacturing process of a coating according to an embodiment of the invention.

[0047] [Fig.6] illustrates a cutting step according to an embodiment of the invention.

[0048] [Fig.7] illustrates a cutting step according to another embodiment of the invention.

[0049] [Fig.8] illustrates a preform having notches according to an embodiment of the invention.

[0050] [Fig.9] illustrates a filament winding step according to another mode of realization of the invention.

[0051] [Fig. 10] illustrates a filament winding step according to another embodiment of the invention.

[0052] [Fig. 11] illustrates a cutting step according to another embodiment of the invention.

[0053] [Fig. 12] illustrates a filament winding step according to another embodiment of the invention.

[0054] [Fig. 13] illustrates a filament winding step according to another embodiment of the invention.

[0055] [Fig. 14] illustrates a filament winding step according to another embodiment of the invention.

[0056] [Fig. 15] illustrates the addition of an additional drape or covering according to one embodiment of the invention.

[0057] In what follows, the boundaries of a domain of values ​​are included in that domain, in particular in the expression "between".

[0058] Furthermore, the expression "at least one" used in this description is equivalent to the expression "one or more". Detailed description of the invention

[0059] Fig. 1 represents a connector 1 intended to connect first and second members (not shown).

[0060] In the illustrated example, the connector is a fitting intended for an application in the aerospace field.

[0061] The connector 1 comprises a body 2 and a ball joint 3 mounted in a housing 4 of the body 2.

[0062] The housing 4, with axis XI, is delimited by an internal surface, or bore of the body 2, spherical so as to cooperate with the ball joint 3.

[0063] The ball joint 3, with axis X2, is able to move by ball joint in the housing 4 of the body 2.

[0064] Advantageously, the ball joint 3 has an outer spherical surface 3a intended to cooperate with the housing 4 for the articulation of the ball joint 3, and an inner surface or bore 3b for the attachment of the second member.

[0065] In the illustrated example, the bore 3b is cylindrical and has axis X2.

[0066] The ball joint 3 can be formed of two parts that can be separated in order to allow mounting the ball joint 3 in the housing 4.

[0067] Connector 1 thus allows the first and second members to be rigidly connected while allowing a possibility of articulation between them, by pivoting the ball joint 3 in the housing 4.

[0068] The body 2 of the connector 1 also includes a fixing area for the first member to be connected which, in the illustrated example, takes the form of a base 5. The means for fixing the first member to the connector 1 may include screws or rivets.

[0069] Advantageously, the body 2 can be made of composite material comprising reinforcing fibers embedded in a plastic matrix.

[0070] Advantageously, the fibers are, for example, made of carbon or glass.

[0071] Preferably, the plastic matrix is ​​a thermosetting resin, for example epoxy, but other materials such as thermoplastic resins, for example PEEK, PEKK, PEAK, can be used.

[0072] Advantageously, the ball joint 3 can be metallic, for example made of titanium, steel, aluminum, bronze or an alloy thereof.

[0073] With reference to figures 2 and 3, the connector 1 also includes a fiber-reinforced polymer coating 6, interposed between the housing 4 of the body 2 and the ball joint 3.

[0074] In the present invention, the term coating refers to a fibrous strip, or liner, formed of one or more layers of fibers impregnated with polymer material.

[0075] The illustrated coating 6 is annular in shape, formed by a sphere segment of diameter 01, and comprising two opposing circular lateral edges 6a and 6b.

[0076] In the illustrated example, the coating 6 obtained by cutting a drape 7 also has two ends 6c and 6d positioned opposite each other to form a ring.

[0077] Fig. 4A illustrates a manufacturing process for the coating 6 according to an embodiment in which the polymer material of the coating 6 made of fiber-reinforced polymer matrix composite material is a thermosetting sand material.

[0078] With reference to [Fig.5], the manufacturing process includes a step of winding 100 a fiber around a mandrel M to form on the mandrel M a drape 7.

[0079] The chuck M is cylindrical, circular and straight.

[0080] The drape 7 formed may comprise a plurality of layers of wound fibers superimposed one on top of the other. Alternatively, the drape 8 may comprise a single layer of wound fibers.

[0081] In the illustrated example, the fiber wound around the mandrel M is a flat fiber forming a strip.

[0082] According to an alternative, several fibers can be wound simultaneously around the mandrel M.

[0083] Each fiber is initially pre-wound onto a head.

[0084] To perform the filament winding, the mandrel M is rotated around its axis Y.

[0085] An initial winding substep of the pre-impregnated fibers around the mandrel M allows a first layer to be formed around the mandrel M. This first layer is formed with the rotation of the mandrel M around its Y axis and the movement of the heads supporting the fibers parallel to the Y axis.

[0086] Then, a succession of fiber winding sub-steps allows the drape 8 to be formed by superimposing layers one on top of the other around the mandrel M.

[0087] Advantageously, step 100 of winding the fibers around the mandrel M can be computer controlled and thus automated.

[0088] For example, the fibers may be glass fibers, carbon fibers, Kevlar® fibers, or any other suitable material.

[0089] Advantageously, a plurality of layers of different types of fibers can be wound and superimposed around the mandrel M.

[0090] According to one embodiment, the fabric 7 may comprise a first side formed by at least one layer of fibers made of polytetrafluoroethylene (PTFE) fibers as well as carbon and / or glass fibers, and a second opposite side formed by at least one layer of fibers made of carbon and / or glass fibers. The first side of the fabric 6, made of fibers with structural properties, may be positioned in contact with the housing 4, and the second side of the fabric 6, further comprising fibers with lubricating properties, may be positioned in contact with the ball joint 3.

[0091] The thermosetting material of the coating 6 made of fiber-reinforced thermosetting material is, for example, an epoxy resin.

[0092] The fiber wound around the mandrel M can be a fiber pre-impregnated with a thermosetting material.

[0093] In a cutting step 200, the drape 7 obtained at the end of the filament winding step 100 is cut.

[0094] In the example illustrated in [Fig. 6], the drape 7 is cut along two axial directions relative to the axis of the mandrel M so as to form two preforms 8 and 9, each forming a half-cylinder. Each preform 8 and 9 is intended for the formation of a coating 6.

[0095] The preforms 8 and 9 obtained at the end of the cutting step 200 are removed from the mandrel M in a removal step 300. The two ends 10 and 11 of the drape 7 are also cut by cutting in a radial direction and then removed.

[0096] According to one characteristic, the chuck M can, for example, be a fusible or inflatable chuck.

[0097] Alternatively, the mandrel M can be removed before the cutting step 200 of the draping 7.

[0098] When the coating 6 produced is made of fiber-reinforced thermosetting matrix composite material, the manufacturing process further includes a polymerization step 500 of the thermosetting material of the preforms 8 and 9 obtained.

[0099] According to one feature, the polymerization step can be carried out in a mold. The preforms 8 and 9 are then removed from the mold after polymerization.

[0100] Alternatively, the fiber wound around the mandrel M can be partially pre-impregnated with thermosetting material, called powdered fiber, or not impregnated with thermosetting material.

[0101] The manufacturing process then includes an additional step of adding 400 of thermosetting material.

[0102] According to one example, the fiber partially pre-impregnated with thermosetting material may comprise a content of between 1 and 4% by weight of the thermosetting material content of the fiber impregnated with thermosetting material at the end of the additional addition step 400.

[0103] Preferably, the additional step of adding 400 of thermosetting material is carried out after cutting the drape 7 of the mandrel M, on the preforms 8 and 9, more preferably after removal of the mandrel M.

[0104] Fig. 4B illustrates a manufacturing process for the coating 6 according to another embodiment in which the thermosetting material of the coating 6 is replaced by a thermoplastic material.

[0105] The fiber wound around the mandrel M is pre-impregnated with a thermoplastic material.

[0106] Advantageously, the manufacturing process includes a folding step 600 of the preforms 8, 9 obtained after cutting the drape 7 to give them the final shape of the coating 6 to be manufactured.

[0107] In the illustrated example, the final shape of the coating 6 is annular spherical.

[0108] In the example illustrated in [Fig.6], each of the semi-cylindrical preforms 8 and 9 is folded back on itself so as to join its two ends 8c and 8d, 9c and 9d and form the spherical coating 6 visible in [Fig.3]. Two coatings 6 are thus obtained.

[0109] The two ends 8c and 8d, 9c and 9d of each of the preforms 8 and 9 are intended to form the two ends 6c and 6d of the coating 6, and the two lateral edges 8a and 8b, 9a and 9b of each of the preforms 8 and 9 are intended to form the two lateral edges 6a and 6b of the coating 6.

[0110] According to one embodiment, the drape 7 can be cut to form more than two preforms, each forming a half-cylinder, in particular by additional cuts in radial directions. Each half-cylinder forms a preform intended to form a coating 6.

[0111] According to another variant illustrated in [Fig.7], and in order to reduce the rate of waste, the drape 7 can be cut so as to form a plurality of cylindrical segments 17, in particular by a plurality of cuts along radial directions and a plurality of cuts along axial directions with respect to the Y axis of the mandrel M. Each cylindrical segment forms a preform intended to form a coating 6.

[0112] When the polymer matrix is ​​a thermosetting matrix, the folding step 600 is preferably carried out before the polymerization step 500.

[0113] When the fiber wound around the mandrel M is a fiber partially pre-impregnated with thermosetting material or not impregnated with material thermosetting, the 600 folding step can be carried out before or after the addition of thermosetting material.

[0114] As illustrated in [Fig.8], notches 12 can advantageously be formed on the two opposite lateral edges 8a, 8b and 9a, 9b of the preforms 8 and 9 in order to facilitate their folding into the final shape of the coating 6.

[0115] Advantageously, each notch 12 can be made by cutting and removing a triangular portion on the lateral edges 8c, 8d, 9c, 9d of the preforms 8, 9.

[0116] In order to limit damage to the fibre network by cutting the fibre, the cutting is carried out so that the angle of each cut triangular portion corresponds to the angle formed between the fibre and that the sides of the triangular portions extend parallel or perpendicular to the fibre.

[0117] The notches 12 make it easier to conform the preforms 8 and 9 to the final shape of the coating 6, limiting the bending of the fibers so as to better preserve the mechanical properties of the coating 6.

[0118] In one embodiment, and with reference to [Fig. 9], the diameter of the mandrel M is preferably equal to the diameter 01 of the sphere formed by the coating 6 to be manufactured, visible in [Fig. 3]. This makes it possible to reduce the pleating of the fibers on the preform 8, 9 during the bending step 600 and thus to further preserve the final mechanical properties of the coating 6.

[0119] Alternatively, the diameter of the mandrel M can be equal to the diameter of the annular portion formed by the coating 6 to be manufactured.

[0120] Unlike a textile fabric coating made of woven fibers that cross only to form a right angle, the angle formed between the fibers of the coating 6 made from the manufacturing process according to the invention can be adjusted.

[0121] Advantageously, the winding step 100 can be carried out so that the angle formed between the axis Y of the mandrel M and the fibers, within at least one layer of fibers of the drape 7, preferably within all the superimposed layers of fibers, is between 50 and 90°. Preferably, the angle is between 70 and 90°, and more preferably between 80 and 90°.

[0122] In the illustrated example, the covering 6 made from the draping 7 is intended to be integrated between the ball joint 3 and the housing 4 of the fitting 1.

[0123] Such ranges of values ​​are particularly advantageous for preventing delamination of the coating 7 of the fitting 1.

[0124] Fig. 10 illustrates a first layer of fibre wound around the mandrel M and close to the circumference of the mandrel M.

[0125] The closer the fibers are extended in a plane close to the circumference of the mandrel M, the easier the folding of the preforms 8, 9 can be carried out without creasing the fibers, particularly when the two ends of each preform 8, 9 are brought together to obtain the annular-shaped coating 6.

[0126] In the illustrated example, the combination of an angle formed between the Y axis of the mandrel M and the fibers of between 50 and 90° and a diameter of the mandrel equal to the diameter of the sphere of the coating 6 to be manufactured is particularly advantageous for preserving the mechanical properties of coating 6.

[0127] In the examples illustrated in Figures 6 and 7, the drape 7 is cut in longitudinal and radial directions, i.e., parallel or perpendicular to the Y-axis of the mandrel M. Alternatively, the drape 7 can be cut helically around the Y-axis of the mandrel M in order to produce a coating in large series, as illustrated in [Fig. 11]. In this case, the helical preform resulting from the helical cutting can be cut into multiple coatings.

[0128] The cut drape can be wound around a reel 13.

[0129] According to another embodiment, the fiber can be wound onto a fabric woven 14 illustrated in [Fig. 12], positioned between the fiber and the mandrel M, in contact with the mandrel M.

[0130] The woven fabric 14 can be formed of one or more fibers partially or totally pre-impregnated with a thermosetting or thermoplastic polymer material or formed of one or more fibers not impregnated with polymer material.

[0131] The coating 6 obtained comprises the drape 7 formed by filament winding and the woven fabric 14.

[0132] Such an addition of the woven fabric 14 makes it possible to add, for example, fibers of different natures and new properties to the draping 7 carried out by filament winding.

[0133] Advantageously, the manufacturing process may include a heating step after the winding step 100 around the mandrel M or after the step of adding 400 thermosetting material so that the polymer material of the impregnated fibers of the drape 7 sticks to the woven fabric 14 to form a cohesion.

[0134] In another embodiment illustrated in [Fig. 13], the fibre can be wound around a mandrel M having a spherical portion 15 of diameter 01.

[0135] Preferably, the mandrel M is a fusible or inflatable mandrel in order to retain the entirety of the spherical portion 15.

[0136] A cut in the draping 7 can be made on the edges of the spherical portion to give it the final annular shape of the covering 6.

[0137] Advantageously, the mandrel M can comprise a plurality of spherical portions 16 of diameter 01 in order to manufacture a plurality of coating 6 in a single operation, as illustrated in [Fig. 14].

[0138] Advantageously, at least one additional drape or coating 16 of fiber-reinforced polymer material can be added to the drape 7 obtained to form a patch, as illustrated in [Fig. 15].

[0139] The draping or additional coating 16 allows, for example, the addition of fibers of different natures and new properties to the draping 7.

[0140] Advantageously, the additional draping or covering 16 is manufactured according to a manufacturing process as previously described.

[0141] According to one example, the additional draping or coating 16 comprises fibers of a different nature from the fibers of the draping 7 obtained on which the addition is made.

[0142] The coating can be fixed to the ball joint or, preferably, to the housing 4 of the body 5 of the connector 1.

[0143] In one embodiment, the coating is fixed to the housing 4 of the body 2 by impregnation of the polymer matrix between the body 2 and the coating 6. Preferably, the polymer matrix of the coating 6 and the polymer matrix of the body 2 are identical in order to improve the cohesion between the coating 6 and the body 2.

[0144] In another embodiment, the coating 6 can be fixed to the contact of the housing 4 or the ball joint 3 by means of an adhesive.

[0145] In the described embodiment, the coating produced by the manufacturing process according to the invention is a coating for a fitting. The invention is not limited to such use and can be applied to the manufacture of a coating for a type of plain bearing other than a fitting, for example a connecting rod end or a shackle.

[0146] Moreover, the invention is not limited to the aerospace field and can be applied to any other technical field.

Claims

Demands

1. A method for manufacturing at least one coating (6) made of polymer material reinforced with one or more fibers, in particular comprising at least one cylindrical or spherical portion or cylindrical or spherical segment, characterized in that it comprises the following steps: - at least one winding step (100) of at least one fiber around a mandrel (M) to form on the mandrel (M) a drape (7) comprising one layer of wound fibers or several layers of wound and superimposed fibers, - at least one withdrawal step (300) of the drape (7) formed from the mandrel (M), and - at least one cutting step (200) of the drape before or after withdrawal from the mandrel (M).

2. A method according to claim 1, wherein the fiber wound around the mandrel (M) is pre-impregnated with a thermosetting material, the method further comprising a polymerization step (400) of the drape (7) obtained.

3. A method according to claim 1, wherein the fiber wound around the mandrel (M) is partially pre-impregnated with a thermosetting material or not impregnated with a thermosetting material, the method further comprising: - after removal of the drape (7) from the mandrel (M), a step of adding (400) thermosetting material to the drape (7), and - a step of polymerizing the drape (7) obtained.

4. A method according to claim 1, wherein the fiber wound around the mandrel (M) is pre-impregnated with a thermoplastic material.

5. A method according to any one of the preceding claims, wherein the angle formed between the axis (Y) of the mandrel M and the fibers within the same layer of fibers of the drape (7) is between 50 and 90°, preferably between 70 and 90°, more preferably between 80 and 90°.

6. A method according to any one of the preceding claims, wherein the fiber is wound around a cylindrical mandrel (M) of diameter equal to the diameter (01) of a cylindrical or spherical portion of the coating (6) to be manufactured.

7. A method according to any one of the preceding claims, wherein the cutting of the drape (7) is helical.

8. A method according to any one of claims 1 to 5, wherein the fibre is wound around a mandrel (M) comprising one or more spherical portions (15).

9. A method according to any one of the preceding claims, comprising the addition of at least one additional drape or coating (16) of fiber-reinforced polymer material to the drape (7) obtained, preferably manufactured according to any one of claims 1 to 8, more preferably, the added drape or coating (16) comprising fibers of a different nature from the fibers of the drape (7) obtained on which the addition is made.

10. A method according to any one of the preceding claims, wherein the fiber is wound onto a woven fabric (14) positioned between the fiber and the mandrel (M), the woven fabric (14) being formed of one or more fibers partially or totally pre-impregnated with a thermosetting or thermoplastic polymer material or formed of one or more fibers not impregnated with polymer material.

11. A method according to any one of the preceding claims, wherein the resulting drape (7) comprises a plurality of layers of wound and superimposed fibers of different types, preferably comprising at least one layer of fibers made of polytetrafluoroethylene (PTFE) fibers and carbon and / or glass fibers and at least one layer of fibers made of carbon and / or in glass.

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