Novel strength materials based on s and z twist yarns for manufacturing composite parts, methods and uses

Abstract

The reinforcing material comprises unidirectional reinforcing plies (2) formed from one or more carbon yarns (3) and incorporating on at least one of its faces, and preferably on each of its faces, a porous polymeric layer (4, 5), in which the polymeric part of the reinforcing material represents between 0.5% and 10% of its total mass and preferably between 2% and 6% of its total mass, characterized in that, according to the choice of claim 1, the carbon yarns (3) are individually twisted with a twist of between 3 and 15 turns per meter, preferably between 6 and 12 turns per meter, and comprise at least one S-twisted yarn and at least one Z-twisted yarn.

Description

TECHNICAL FIELD

[0001] The present invention relates to the technical field of reinforcing materials suitable for forming composite parts. More specifically, the present invention relates to reinforcing materials suitable for producing composite parts in combination with injection or infusion of a resin, said reinforcing materials comprising a unidirectional web made at least partially of a series of individually twisted carbon yarns, the twist of said carbon yarns being suitable for ensuring the diffusion of said injected or infused resin during the production of said composite parts. BACKGROUND

[0002] The manufacturing of composite parts or articles, i.e. first comprising one or more fibrous reinforcements, in particular of the unidirectional fibrous web type, and secondly a matrix, said matrix being generally of the thermoset type and can comprise one or more thermoplastics, can be produced for example by so-called direct or liquid composite molding (LCM) methods. Direct methods are defined by the fact that the fibrous reinforcement(s) are used in "dry" state, i.e. without the final matrix, the resin or matrix being used separately, for example by injection into a mold containing the fibrous reinforcement (Resin Transfer Molding (RTM) method), by infusion of the entire thickness of the fibrous reinforcement (Liquid Resin Infusion (LRI) method or Resin Film Infusion (RFI) method), or else by manual coating / impregnation on each individual layer of fibrous reinforcement by means of a roller or brush, applied in succession onto a form. In the context of the manufacturing of composite parts, in particular in the aeronautical field, the batch productivity can be very high. For example, for the manufacturing of single aisle aircraft, the aeronautical customers wish to be able to produce several tens of aircraft per month. Direct methods such as infusion or injection are particularly relevant methods that can meet this requirement.

[0003] For RTM, LRI or RFI methods, it is generally necessary to first produce a fibrous preform or stack in the shape of the finished product desired, and then to impregnate said preform or stack with a resin to form the matrix. The resin is injected or infused by means of a temperature pressure differential, then, after the entire required quantity of resin has been contained in the preform, the assembly is brought to a higher temperature to carry out the polymerization / crosslinking cycle and thereby harden it.

[0004] Composite parts used especially in the automotive, aeronautical or naval industries are subject to very stringent requirements, in particular in terms of mechanical properties. In order to save fuel and facilitate the maintenance of the parts, the aeronautical industry has replaced many metallic materials with lighter composite materials.

[0005] During the production of a part, the resin which is subsequently combined with the fibrous reinforcement, in particular by injection or infusion, can be a thermosetting resin, for example of the epoxy type. In order for the resin to be able to flow properly through the preform consisting of a stack of several layers of fibrous reinforcement, this resin is generally very fluid, for example having a viscosity of the order of 50 mPas. to 200 mPas. or less at the infusion / injection temperature. The main drawback of this type of resin is the brittleness after polymerization / crosslinking, which results in a low impact resistance of the composite parts produced.

[0006] To solve this problem, it has been proposed in the prior art documents to combine the fibrous reinforcement layers, in particular carbon thread unidirectional webs, with a porous thermoplastic polymer layer and in particular with a thermoplastic fibrous woven fabric or nonwoven material, also called veil. Such solutions are in particular described in patent applications or patents EP 1125728, US 6,828,016, WO 00 / 58083, WO 2007 / 015706, WO 2006 / 121961, US 6,503,856, US 2008 / 7435693, WO 2010 / 046609, WO 2010 / 061 1 14 and EP 2,547,816, US 2008 / 0289743, US 2007 / 8361262, US 201 1 / 9371604, WO 201 1 / 048340. The addition of such a porous thermoplastic layer, in particular of a nonwoven type, makes it possible to improve the mechanical properties of the composite parts obtained in Compression After Impact (CAI) tests, which are generally used to characterize the impact resistance of structures. The use of a nonwoven material in particular makes it possible to achieve mechanical properties adapted to the aeronautical field.

[0007] In order to achieve a satisfactory production rate of composite parts, the time for laying up the dry reinforcement material and for impregnating or infusing the resin into the resulting dry reinforcement material stack or preform should be as short as possible.

[0008] In addition, in the aeronautical field, the stresses associated with the electrical environment of the aircraft in flight and on the ground, in particular in the event of a lightning strike, make it necessary to provide a material which meets the high standards in this field.

[0009] To this end, solutions have been proposed in the prior art to:

[0010] - increase the permeability of the dry reinforcement material to the liquid resin injected or infused;

[0011] - provide satisfactory transverse electrical conductivity.

[0012] The Applicant has already proposed a micro-perforation process for the aforementioned materials which increases the transverse permeability of the material (WO 2010 / 046609), increases its transverse cohesion and therefore facilitates its processing by automated lay-up (WO 2014 / 076433) and increases the transverse electrical conductivity of the composite parts produced (WO 2013 / 160604).

[0013] Nevertheless, at an industrial scale, this technique requires special tools to make the micro-perforations and leads to complex lay-up operations of the micro-perforated material, in particular for those having high grammage.

[0014] Furthermore, the micro-perforation technique presents difficulties in being applicable to the manufacture of dry reinforcement materials made of unidirectional nets of high-grammage carbon yarns. Indeed, the amount of polymeric binder present in the woven fabric or non-woven material is generally insufficient to i. obtain a proper cohesion of the dry reinforcement material, which is necessary for a satisfactory lay-up, and ii. have micro-perforations leading to high permeability. However, the manufacture of dry reinforcement materials made of unidirectional high-grammage carbon yarn nets is desirable because such materials make it possible to increase the weight of dry reinforcement material laid up per unit of time.

[0015] In order to increase the cohesion of the unidirectional nets present in the reinforcement material, in WO 2012 / 164014, the Applicant proposes to use a polymeric powder by making it penetrate into the interior of the unidirectional net, which makes homogenization of the dry net possible and can facilitate the manufacture of unidirectional nets having high basis weight.

[0016] The application EP 2 794 221 proposes to treat the unidirectional net with a liquid polymeric binder composition which penetrates into the net, the binder composition representing no more than 15% of the final weight of the reinforcement material obtained. Nevertheless, the use of this method leads to a low permeability, in particular transverse permeability, due to the extreme compression of the reinforcement filaments, leading to a decrease in permeability.

[0017] Furthermore, the transverse electrical conductivity of the parts obtained with such materials in which the reinforcement fibers are carbon fibers is significantly lower than the transverse electrical conductivity obtained with the technique using micro-perforation.

[0018] In addition, the application WO 2008 / 155504 in the name of the applicant describes a method for manufacturing a composite material, in which at least one twisted yarn is applied to a laying surface and has at least one trajectory with a curved region on the laying surface, and in which the reinforcing yarns are bonded to the laying surface by means of a polymeric adhesive. The method is used to produce parts or preforms of complex shape in which it is necessary to lay the yarns on curved regions and it is proposed to apply to the yarns, upstream of their laying, a twist chosen to compensate at least for the difference in length presented by the extreme paths of the yarns on either side of the width of the yarn, measured parallel to the laying surface.

[0019] WO 2013 / 133437 describes a very particular material composed of carbon yarns, comprising 50,000 to 60,000 twisted filaments with a twist of 5 to 50 turns per meter and arranged in the same direction so as not to overlap, to provide a carbon sheet with a basis weight greater than 800 g / m2and less than or equal to 6,000 g / m2, suitable for the RTM process. The proposed material is intended for wind turbine blades, vehicles or boats, but not for the aeronautical field.

[0020] The object of the present application is therefore to provide new reinforcing materials for the production of composite parts in combination with the injection or infusion of a resin, comprising at least one unidirectional reinforcing net of multiple carbon yarns, and which are suitable for the aeronautical field. These reinforcing materials exhibit improved laying performance, reduced overrun after laying and improved transverse electrical conductivity, while retaining a high transverse permeability. They can also be produced at high basis weight, without altering their laying performance, which remains satisfactory and leads to reduced overrun after laying.

[0021] Furthermore, the present application proposes to provide reinforcing materials with a high transverse permeability and which allow satisfactory diffusion of the resin injected or infused therein during the subsequent production of the composite part.

[0022] Another object of the present application is to provide new reinforcing materials for the production of composite parts in combination with the injection or infusion of a resin, with satisfactory transverse electrical conductivity, in particular for the aeronautical field.

[0023] Another object of the present application is to provide new materials whose manufacturing process is easily automatable, while producing reinforcing materials with a satisfactory and controlled quality. The materials according to the present application can therefore be produced in long lengths and at high rates. SUMMARY

[0024] In this context, the present invention relates to a reinforced material comprising a unidirectional reinforcement web formed by a series of at least 3 twisted carbon reinforcement yarns, said unidirectional reinforcement web incorporating on one face or on each face thereof a layer of porous polymeric fibres, the polymeric fraction of said reinforced material representing between 0.5% and 10% of its total weight and preferably between 2% and 6% of its total weight.

[0025] said carbon reinforcement yarns are individually twisted with a twist of between 3 twists per meter and 15 twists per meter, preferably between 6 twists per meter and 12 twists per meter, and comprise at least one twisted carbon reinforcement S twist yarn and at least one twisted carbon reinforcement Z twist yarn, wherein:

[0026] - when the total number of twisted carbon reinforcement yarns forming said unidirectional reinforcement web, called the total number of yarns, is even, the number of twisted carbon reinforcement S twist yarns on one side of the plane Δ and the number of twisted carbon reinforcement S twist yarns on the other side of the plane Δ are each independently an integer within the range {[(total number of yarns) / 4]-35%; [(total number of yarns) / 4]+35%}, each end of said range being rounded to the nearest integer if its defining formula leads to an integer, the other twisted carbon reinforcement yarns being Z twist yarns (definition PI);

[0027] - when the total number of twisted carbon reinforcement yarns forming said unidirectional reinforcement web, called the total number of yarns, is odd, the number of twisted carbon reinforcement S twist yarns on one side of the plane Δ and the number of twisted carbon reinforcement S twist yarns on the other side of the plane Δ are two integers or two half-integers and are each independently within the range {[(total number of yarns) / 4]-35%; [(total number of yarns) / 4]+35%}, each end of said range being rounded to the nearest integer or integer plus half if its defining formula leads to an integer or integer plus half, the other twisted carbon reinforcement yarns being Z twist yarns (definition II);

[0028] the plane Δ is a plane parallel to the general direction of extension of said unidirectional web and divides said unidirectional web into two equal parts perpendicular to its surface. In other words, the number of twisted carbon reinforcement yarns forming the unidirectional reinforcement web, called the total number of yarns for simplicity within the scope of the invention, is equal on either side of the plane Δ, at the neutral fibre level of the unidirectional reinforcement web. Thus, if the unidirectional reinforcement web is composed of n twisted carbon reinforcement yarns, n being an integer greater than 3, there are n / 2 twisted carbon reinforcement yarns on either side of the plane Δ.

[0029] Furthermore, the unidirectional reinforcement web comprises an integer number m of twisted carbon reinforced S-twist yarns, the sum of the number ml of twisted carbon reinforced S-twist yarns located on one side of the plane Δ and the number m2 of twisted carbon reinforced S-twist yarns located on the other side of the plane Δ is an integer number. Similarly, the unidirectional reinforcement web comprises an integer number p of twisted carbon reinforced Z-twist yarns, the sum of the number pl of twisted carbon reinforced Z-twist yarns located on one side of the plane Δ and the number p2 of twisted carbon reinforced Z-twist yarns located on the other side of the plane Δ is an integer number. Thus, for example, in the case of a unidirectional reinforcement web formed by a sequence of twisted carbon reinforced SZSZSZS yarns (twist of the yarns laid continuously) satisfying the definition 11, the number of yarns n / 2 on either side of the plane Δ is 3.5, ml = m2 = 2 and pl = p2 = 1.5.

[0030] According to an advantageous feature, the unidirectional reinforcement web is formed by a series of S-twist twisted carbon reinforced yarns and a series of Z-twist twisted carbon reinforced yarns having one of the configurations (SZ)i, S(ZS)j or Z(SZ)j, wherein i and j are integers, in particular in the range of 2 to 20, preferably in the range of 2 to 10.

[0031] According to certain embodiments, the unidirectional reinforcement web has a grammage in the range of 126 g / m2to 1000 g / m2. 2 to 1000 g / m2 2 , in particular 126 g / m2 2 to 420 g / m2 2 , preferably 126 g / m2 2 to 280 g / m2 2 and most preferably 126 g / m2 2 to 210 g / m2 2 , or 210 g / m2 2 to 280 g / m2 2 .

[0032] In particular, the unidirectional reinforcement web is formed by twisted carbon reinforced yarns having a titre in the range of 3K to 24K, preferably in the range of 6K to 12K.

[0033] According to an embodiment, the one or more porous polymer layer(s) present is a porous membrane, a scrim, a powder coating, a liquid polymer coating, a woven fabric, or preferably a non-woven material or veil.

[0034] Within the scope of the present application, the one or more porous polymer layer(s) advantageously has thermoplastic properties and in particular consists of a thermoplastic polymer, a partially cross-linked thermoplastic polymer, a mixture of such polymers, or a mixture of a thermoplastic polymer and a thermoset polymer.

[0035] The one or more polymer fibre layer(s) present has a hot-melt property and its bonding with the unidirectional reinforcement web is achieved by means of this hot-melt property.

[0036] Advantageously, the one or more porous polymer layers are nonwoven materials and, in the case where each face of the unidirectional reinforcement web is associated with a porous polymer layer, these porous polymer layers are preferably identical nonwoven materials.

[0037] Typically, the one or more nonwoven materials have a basis weight ranging from 0.2 g / m 2 to 20 g / m 2 and / or a thickness ranging from 0.5 microns to 50 microns, preferably from 3 microns to 35 microns.

[0038] The reinforcement material according to the application advantageously has no perforation, stitching, knitting or weaving features.

[0039] Within the scope of the application, the use of carbon reinforcement yarns that have previously been subjected to a twisting operation, thereby having a series of carbon yarns with a twist ranging from 3 t / m to 15 t / m in the reinforcement material according to the application, makes it possible:

[0040] - to obtain adhesion between the upper and lower surfaces of the unidirectional web, thereby increasing the transverse cohesion and thus making it possible to integrate high-grammage webs, while preserving the satisfactory properties of the reinforcement material obtained, compatible with its handling and its layup;

[0041] - to create, by means of the twisted reinforcement yarns, a diffusion continuity of resin between the two faces of the unidirectional web, said resin being to be injected or infused during the production of the composite part. The continuity of the filaments of the twisted reinforcement yarns connecting the two faces of the unidirectional web contributes to the transverse permeability. In addition, the twisted carbon yarns are able to create channels extending along the filaments of the twisted carbon yarns connecting the two faces of the unidirectional web. Thus, the transverse permeability is obtained following the filaments extending from one face of the unidirectional web to the other by means of a large number of permeabilities extending in the horizontal of the twisted carbon yarns;

[0042] - to create, by means of the carbon yarns as electrical conductors, a continuity of electrical conductivity along the filaments of the twisted yarns connecting the two faces of the unidirectional web.

[0043] According to the definitions PI and II, by using unidirectional webs formed from more than three twisted carbon reinforcement yarns, with a balance between the number of twisted carbon reinforcement S-twist yarns and the number of twisted carbon reinforcement Z-twist yarns, it is possible to obtain reinforcement materials with fewer defects, even when these reinforcement materials are manufactured on an industrial scale using automated methods. The layup of the reinforcement materials according to the application is also better controlled, as their trajectories can be more easily maintained parallel to the general direction of extension of the unidirectional web.

[0044] The application even more particularly relates to a reinforcement material having a width greater than 7 mm, preferably greater than 12 mm and preferably in the range 12 mm to 51 mm and preferably having a length of 2 m to 5000 m, preferably 100 m to 2000 m.

[0045] The application relates to a reinforcement material for producing a composite part by means of a direct method. That is, in order to produce a composite part, the reinforcement material according to the application is to be combined with a polymeric resin which is to be injected or infused into the reinforcement material or a stack of such reinforcement materials. Furthermore, conventionally, the weight of the polymeric portion of the reinforcement material according to the application represents no more than 10% of the total weight of the reinforcement material according to the application. Typically, the polymeric portion of the reinforcement material represents 0.5% to 10% of the total weight of the reinforcement material and preferably 2% to 6% of its total weight. This polymeric portion corresponds to the total portion of one or more polymers present in the reinforcement material according to the application: it thus comprises or consists of one or more porous polymeric layers present within the reinforcement material according to the application. The achievement of the advantages of the application does not require an increase in the polymeric portion of the material, i.e. in the amount of polymeric material in the one or more porous polymeric layers present on one side of the unidirectional web and advantageously on both sides of the unidirectional web, i.e. on each face thereof.

[0046] In addition to the use of twisted carbon yarns according to the proposal of the application to make unidirectional webs and even high-grammage unidirectional webs, the polymeric porous layer of the material according to the application, before the step of micro-perforation, corresponds to those described in the prior art and in particular those described in the application WO 2010 / 046609.

[0047] The unidirectional reinforcement web consists of an assembly of carbon reinforcement yarns, all of which are twisted and positioned in series. After the unidirectional web is formed, it can be combined with a porous polymeric layer, in particular by lamination, on one face thereof and preferably on each face thereof.

[0048] According to another feature, the application relates to a method for preparing a reinforcement material, said method comprising the following successive steps:

[0049] al) providing a unidirectional reinforcement web formed from a series of at least 3 individual twisted carbon yarns, said individual twisted carbon reinforcement yarns having a twist of 3 to 15 twists per meter, preferably 6 twists per meter to 12 twists per meter and comprising at least one twisted carbon reinforcement S-twist yarn and at least one twisted carbon reinforcement Z-twist yarn, and wherein:

[0050] - when the total number of twisted carbon reinforcing yarns forming the unidirectional reinforcement net is even, the number of twisted carbon reinforcing S-twisted yarns on one side of the plane A and the number of twisted carbon reinforcing S-twisted yarns on the other side of the plane A are each independently an integer number in the range {[(total number of yarns) / 4]-35%; [(total number of yarns) / 4]+35%}, if the defining formula does not lead to an integer number, rounding each end of the range to the nearest integer, the other twisted carbon reinforcing yarns being Z-twisted yarns;

[0051] - when the total number of twisted carbon reinforcing yarns forming the unidirectional reinforcement net is odd, the number of twisted carbon reinforcing S-twisted yarns on one side of the plane A and the number of twisted carbon reinforcing S-twisted yarns on the other side of the plane A are two integer numbers or two half-integers and are each independently in the range {[(total number of yarns) / 4]-35%; [(total number of yarns) / 4]+35%}, if the defining formula does not lead to an integer number or to an integer plus half, rounding each end of the range to the nearest integer or to an integer plus half, the other twisted carbon reinforcing yarns being Z-twisted yarns;

[0052] the plane A is a plane parallel to the general direction of the unidirectional net and dividing the unidirectional net into two equal parts perpendicularly to its surface;

[0053] a2) providing one or two porous polymeric layers;

[0054] a3) associating the porous polymeric layer(s) with one face of the unidirectional reinforcement net, and in the case of two porous polymeric layers, each of them with each face of the unidirectional reinforcement net.

[0055] For example, the preparation method comprises, upstream of step al), a step of producing the unidirectional reinforcement net, said step comprising applying to one or a series of carbon reinforcing yarns having an S-twist a twist of 3 to 15 turns per meter, said twist being applied individually to each carbon reinforcing yarn, and applying to one or a series of carbon reinforcing yarns having a Z-twist a twist of 3 to 15 turns per meter, said twist being applied individually to each carbon reinforcing yarn.

[0056] According to one embodiment, the preparation method comprises, upstream of step al):

[0057] i) applying to one or a series of carbon reinforcing yarns having an S-twist a twist of 3 to 15 turns per meter, said twist being applied individually to each carbon reinforcing yarn, and applying to one or a series of carbon reinforcing yarns having a Z-twist a twist of 3 to 15 turns per meter, said twist being applied individually to each carbon reinforcing yarn,

[0058] ii) aligning the twisted reinforcing yarns thus obtained and arranging said yarns in succession to form a unidirectional reinforcement web comprising at least one S twisted yarn and at least one Z twisted yarn, and wherein:

[0059] - when the total number of twisted carbon reinforcing yarns forming said unidirectional reinforcement web is even, the number of twisted carbon reinforcing S twisted yarns on one side of the plane A and the number of twisted carbon reinforcing S twisted yarns on the other side of the plane A are each independently an integer number within the range {[(total number of yarns) / 4]-35%; [(total number of yarns) / 4]+35%}, if the defining formula does not lead to an integer number, rounding each end of the range to the nearest integer, the other twisted carbon reinforcing yarns being Z twisted yarns;

[0060] - when the total number of twisted carbon reinforcing yarns forming said unidirectional reinforcement web is odd, the number of twisted carbon reinforcing S twisted yarns on one side of the plane A and the number of twisted carbon reinforcing S twisted yarns on the other side of the plane A are two integer numbers or two half-integers and are each independently within the range {[(total number of yarns) / 4]-35%; [(total number of yarns) / 4]+35%}, if the defining formula does not lead to an integer number or to an integer plus half, rounding each end of the range to the nearest integer or to an integer plus half, the other twisted carbon reinforcing yarns being Z twisted yarns;

[0061] The plane A is a plane parallel to the general direction of the unidirectional web and divides said unidirectional web into two equal parts perpendicularly to its surface.

[0062] In such a method, the one or more porous polymeric layers have hot-melt properties and the bonding of step a3) is advantageously obtained by applying one or more of said porous polymeric layers to one or each face of the unidirectional reinforcement web, said laying being accompanied or followed by heating the polymeric fibres, causing them to soften or melt, and then cooling.

[0063] Another object of the present application is a preform at least partially composed of one or more reinforcement materials according to the present application.

[0064] Another object of the present application relates to a method for manufacturing a composite material part from at least one reinforcement material according to the present application. According to this manufacturing method, a thermosetting resin, a thermoplastic resin, or a mixture of a thermosetting resin and a thermoplastic resin is injected or infused into the reinforcement material, a stack of a plurality of reinforcement materials according to the present application or a preform according to the present application.

[0065] In particular, such a method comprises, prior to the infusion or injection of the resin, the step of forming a ply or stack comprising a plurality of reinforcing materials according to the application, during which the reinforcing materials are continuously conveyed within a guide member and cycled, so as to ensure their positioning at the time of their layup to produce the desired ply or stack. Conventionally, the materials according to the application are cut to the desired dimensions, in particular to the desired length, to form the ply or stack to be produced.

[0066] Advantageously, the method for manufacturing a composite part comprises, prior to the infusion or injection of the resin, a layup or shaping, preferably using the hot-melt qualities of the porous polymeric layer present in the reinforcing material(s).

[0067] Another object of the application relates to the use of one or more reinforcing materials according to the application for the production of a preform or a composite part combined with a thermosetting resin, a thermoplastic resin, or a mixture of a thermosetting resin and a thermoplastic resin.

[0068] Advantageously, a thermosetting resin, and in particular an epoxy resin, is infused or transfused.

[0069] The application will be better understood from the following detailed description, with reference to the attached drawings. BRIEF DESCRIPTION OF DRAWINGS

[0070] [ Figure 1A ] Figure 1A is a partial schematic view of a reinforcing material according to the application, the section being parallel to the general direction of extension of the unidirectional web 2.

[0071] [ Figure 1B ] Figure 1B is a partially cutaway schematic perspective view showing a reinforcing material not in accordance with the application, in which the unidirectional web 2’ is formed from a series of twisted yarns having the same twist.

[0072] [ Figure 1C ] Figure 1C is a partially cutaway schematic perspective view showing a reinforcing material according to the application, in which, reading the figure from right to left, the unidirectional web is formed from a series of twisted reinforcing yarns 3 in an SZSZSZ configuration, i.e. an S twisted yarn is laid next to a Z twisted yarn, which in turn is laid next to an S twisted yarn, and so on.

[0073] [ Figure 2 ] Figure 2 is a schematic view showing the twist on a twisted carbon yarn according to the application.

[0074] [ Figure 3 ] Figure 3 is a schematic view illustrating the principle of a twisting machine for applying a twist to a carbon yarn.

[0075] [ Figure 4 ] Figure 4 is a schematic view of a measuring station suitable for measuring the width of carbon yarns, in particular twisted carbon yarns.

[0076] [ Figure 5 ] Figure 5 is a graph showing the average width (mm) of carbon yarns as a function of the twist (tpm) for various carbon yarns.

[0077] [ Figure 6 ] Figure 6 is a graph showing the standard deviation of the average width (mm) of carbon yarns as a function of the twist for various carbon yarns.

[0078] [ Figure 7 ] Figure 7 is a graph showing the percentage of values higher than the target value of the width of carbon yarns as a function of the twist of various carbon yarns for a grammage of 140 g / m2.

[0079] [ Figure 8 ] Figure 8 is a graph showing the percentage of values higher than the target value of the width of carbon yarns as a function of the twist of various carbon yarns for a grammage of 210 g / m2.

[0080] [ Figure 9 ] Figure 9 is a graph showing the percentage of values higher than the target value of the width of carbon yarns as a function of the twist of various carbon yarns for a grammage of 280 g / m2.

[0081] [ Figure 10 ] Figure 10 is a graph showing the percentage of values higher than the target value of the width of carbon yarns as a function of the twist of various carbon yarns for a grammage of 252 g / m2.

[0082] [ Figure 11 ] Figure 11 is a graph showing the percentage of values higher than the target value of the width of reinforcing yarns as a function of the twist of various reinforcing yarns for a grammage of 350 g / m2.

[0083] [ Figure 12 ] Figure 12 is a schematic chart showing the position of the measuring points on the preform.

[0084] [ Figure 13 ] Figure 13 is a schematic chart illustrating the principle of the thickness measurement of a carbon yarn preform.

[0085] [ Figure 14 ] Figure 14 is a graph showing the percentage of values higher than the target value of the thickness of carbon yarn preforms as a function of the twist of various carbon yarns for a grammage of 280 g / m2 Material 2 consisting of a unidirectional carbon yarn web of basis weight 280 g / m2 made of 4 yarns twisted at 10 twists per meter with S twist and the micro-perforated comparative material 1, the graph of the out-of-limit variation as a function of the number of plies applied.

[0086] [ Figure 15 ] is the transverse permeability (m 2 ) of the micro-perforated comparative material or of the material consisting of a unidirectional carbon yarn web all twisted with S twist as a function of the fiber volume ratio (FVR).

[0087] [ Figure 16 ] Figure 16 The differences observed in the formation of plies made of reinforcing material (6.35 mm wide) consisting of a unidirectional carbon yarn web of basis weight 280 g / m 2 2 twisted at 10 twists per meter with 3 different configurations: SSSS, SZZS and SZSZ are shown. On the right, a partial schematic view of the top of the unidirectional layer present in each case in the reinforcing material used is shown, with above each partial schematic view a section along the yarn is depicted, the S or Z twist direction of the reinforcing yarn of each unidirectional layer.

[0088] [ Figure 17 ] Figure 17 The gap obtained in the production of a unidirectional carbon yarn web of basis weight 210 g / m2 and width 38.1 mm between 7 reinforcing yarns with S twist and 5 reinforcing yarns with Z twist, in the configuration SSSSSSSZZZZZZSSSSSS (7 S-twist yarns, then 5 Z-twist yarns, then 6 S-twist yarns) is shown. Indeed, during the production of the unidirectional web, the S-twist yarn group is driven to the left, while the Z-twist yarn group is driven to the right, which produces a gap at the junction of the 7 S-twist yarns / 5 Z-twist yarns.

[0089] [ Figure 18 ] Figure 18 is a schematic representation of the production line used in the examples. DETAILED DESCRIPTION

[0090] As shown in Figure 1A , one object of the present invention relates to a reinforcing material 1 comprising a unidirectional reinforcing web 2 formed of more than three carbon reinforcing yarns 3, said unidirectional reinforcing web incorporating on at least one of its faces and advantageously on each of its faces a porous polymeric layer 4, 5. According to the invention, an embodiment thereof is shown in Figure 1CIn particular, the reinforcement material 1 according to the application consists of a unidirectional reinforcement web 2 formed of more than three carbon reinforcement yarns 3, said unidirectional reinforcement web incorporating on one of its faces, and advantageously on each of its faces, a porous polymer layer 4, 5.

[0091] More precisely, as will be described in detail in the following description, the carbon reinforcement yarns 3 forming the unidirectional reinforcement web 2 are all individually twisted.

[0092] Figure 1C A unidirectional web 2 made of a plurality of individually twisted carbon reinforcement yarns 3 is shown, said unidirectional web incorporating on each of its faces a veil 4, 5. Each twisted reinforcement yarn 3 has an overall extension direction D G (corresponding to the central axis of the yarn) which is rectilinear in the plane of extension of the unidirectional web. Each twisted reinforcement yarn 3 has an overall extension direction D G which is rectilinear, parallel to the extension surfaces S4 and S5 of the veils 4, 5, which are Figure 1B in this case planar. In the web 2’ shown in Figure 1B , all the yarns are twisted with an S twist, which does not correspond to the juxtaposition (also called the arrangement) of the yarns according to the application.

[0093] By "unidirectional reinforcement web" is meant a web which is uniquely or almost uniquely composed of carbon yarns arranged parallel to one another. By "parallel arrangement" is meant that the overall extension direction D G of the reinforcement yarns are all parallel to one another or substantially parallel to one another. It is generally accepted by those skilled in the art that a deflection of less than or equal to 3°, preferably less than or equal to 2° and more preferentially less than or equal to 1° between certain overall extension directions D G of two reinforcement yarns does not change the unidirectional nature of the web. If the reinforcement yarns are all parallel to one another, the overall extension direction of the unidirectional web corresponds to the overall extension direction D G of the reinforcement yarns, or for the rare cases in which there is no strict parallelism between all the extension directions D G of the reinforcement yarns forming the unidirectional web 2, to the average of these overall extension directions.

[0094] In a unidirectional web, the reinforcement yarns are arranged continuously so as to ensure optimal surface coverage. In particular, it is desirable to avoid local gaps of more than 1 mm perpendicular to the extension direction of the unidirectional web over a length of more than 10 cm, i.e. parallel to the extension direction of the unidirectional web.

[0095] Thermoplastic binder yarns, in particular of the polyamide, copolyamide, polyester, copolyester, copolyamide-block-ester / ether, polyacetal, polyolefin, thermoplastic polyurethane or phenoxy type, can be used to facilitate handling of the unidirectional reinforcement web, if necessary, prior to its combination with one or more porous polymer layers. Such binder yarns generally extend transversely to the carbon yarns. The term "unidirectional web" also includes unidirectional woven fabrics in which spacer weft yarns extend parallel to each other and are interwoven with the carbon yarns which are the warp yarns of the unidirectional fabric. Even in the presence of such interweaving, stitching or weft yarns, the carbon yarns which extend parallel to each other represent at least 95% of the weight of the web and are therefore described as "unidirectional". Nonetheless, according to a particular embodiment of the application, the unidirectional web does not contain any weft yarns interwoven with the carbon yarns in order to avoid any waviness. In particular, the reinforcement material according to the application does not comprise any perforation, braiding, stitching or knitting. In the unidirectional web, the carbon yarns are preferably not combined with a polymeric binder and are therefore described as dry, i.e. they are not impregnated, nor coated, nor combined with any polymeric binder, prior to their combination with the porous polymer layers 4, 5. However, the carbon yarns are typically characterized by a standard sizing basis weight of up to 2% of their weight.

[0096] The carbon reinforcement yarns (which can be more simply referred to as reinforcement yarns or carbon yarns within the scope of the present invention) are generally made from assemblies of fibers or filaments and generally contain from 1,000 to 320,000 filaments, advantageously from 12,000 to 24,000 filaments. In a particularly preferred embodiment, within the scope of the present invention, carbon yarns of 1K to 24K are used. The constituent fibers are preferably continuous. The carbon yarns used generally have a substantially circular cross-section (classified as round yarns), or, preferably, a substantially parallelepiped or elliptical cross-section (classified as flat yarns). These yarns have a certain width and thickness. As an example of loose yarns not in contact with any physical element, a flat carbon yarn of 3K and of 200 Tex generally has a width of 1 mm to 3 mm, a flat carbon yarn of 12K and of 446 Tex has a width of 2 mm to 5 mm, a flat carbon yarn of 12K and of 800 Tex has a width of 3 mm to 7 mm, a 24K carbon flat yarn of 1600 Tex has a width of 5 mm to 12 mm, and a 24K carbon flat yarn of 1040 Tex has a width of 5 mm to 10 mm. Thus, a flat carbon yarn of 3,000 to 24,000 filaments will generally have a width of 1 mm to 12 mm. Among the carbon yarns, there are high resistance (HR) yarns having a tensile modulus of 220 GPa to 241 GPa and a tensile strength of 3450 MPa to 4830 MPa, intermediate modulus (IM) yarns having a tensile modulus of 290 GPa to 297 GPa and a tensile strength of 3450 MPa to 6200 MPa, and high modulus (HM) yarns having a tensile modulus of 345 GPa to 448 GPa and a tensile strength of 3450 Pa to 5520 Pa (according to the "ASM Handbook", ISBN 0-87170-703-9, ASM International 2001). In particular, within the scope of the present invention, the unidirectional reinforcement web 2 can be formed from one or more carbon reinforcement yarns 3 of 3K to 24K, preferably 6K to 12K.

[0097] Within the scope of the present invention, the reinforcement yarns of the unidirectional reinforcement web 2 are made from a series of individually twisted carbon yarns 3 having a twist of 3 twists per meter to 15 twists per meter, preferably 6 twists per meter to 12 twists per meter, the series of yarns comprising at least 3 yarns thus individually twisted. According to the invention, the twisted carbon yarns 3 are carbon yarns to which a twist has been applied, i.e. a relative rotation of the outer edges of the yarn around a neutral fiber thereof (corresponding to the central axis of the yarn) such that these describe a helical trajectory, i.e. the tangent at each point forms a substantially constant angle with a given direction. As shown in the figure, the twisted carbon yarns 3 have a neutral fiber at their core, the general direction of which corresponds to the longitudinal direction X of the carbon yarn 3 (also called the general direction of extension D Figure 2 G ​), while the filaments follow a helical path around this general direction. Figure 2 The helical shape of the generatrix h of the twisted carbon yarn 3 is schematically shown, said twisted reinforcing yarn having a twist of one twist over the linear distance d taken along the longitudinal direction X (also referred to as the general direction of extension D G ).

[0098] Each carbon yarn 3 is individually twisted. Such a twist can be obtained, for example, by using a twisting machine, such as the model UT-1000 machine marketed by Kamitsu Seisakusho Ltd. Figure 3 is a diagram showing the twisting process performed by the twisting machine, which makes it possible to obtain the twisted carbon yarn 3 according to the application. The spool 7 wound with the carbon yarn to be twisted is mounted so that it can rotate about its axis A to allow the carbon yarn to be unwound by means of the guide 8 onto the spool 9 for winding the twisted carbon yarn 3. The spool 7 provided with the carbon yarn to be twisted is mounted on a support 11 which is driven by a motor 12, rotating along an axis B perpendicular to the axis of the spool 7. The twisting of the carbon yarn 3 depends on the linear speed of unwinding of the carbon yarn and on the speed of rotation of the support 11 of the spool 7.

[0099] According to another embodiment object of the application, the unidirectional reinforcing net 2 is formed by at least one twisted carbon S yarn 3 and at least one twisted carbon Z yarn. The twisting direction of the S and Z twisted carbon reinforcing yarns 3 is different, as shown in Figure 16 For the definition of the meaning of S twist or Z twist, reference is made to the book "Handbook of Weaving", pages 16-17, Prof. Sabit Adanur, Department of Textile Engineering, Auburn, USA, ISBN 1-58716-013-7.

[0100] As indicated, the unidirectional reinforcing net 2 is formed by a plurality of carbon yarns 3, of which there are at least 4, each having a twist of 3 to 15 turns per meter, preferably 6 to 12 turns per meter. Each yarn has a direction of extension D G corresponding to the central axis of the yarn. The twisted reinforcing yarns 3 forming the unidirectional reinforcing net 2 are arranged continuously and the direction of extension of the twisted reinforcing yarns 3 is parallel to each other, thereby forming a unidirectional net. It is understood that all the carbon yarns 3 forming the unidirectional reinforcing net 2 are individually twisted, with a twist of 3 to 15 turns per meter, preferably 6 to 12 turns per meter.

[0101] According to the present application, it is possible to use both one or more twisted reinforcing S twisted yarns 3 and one or more twisted reinforcing Z twisted yarns 3 in the same web. That is, the unidirectional web 2 contains twisted reinforcing yarns 3 having different twisting directions: it is therefore not formed only of reinforcing Z twisted yarns 3 or reinforcing S twisted yarns 3, but contains at least one reinforcing Z twisted yarn 3 extending adjacent to one or more reinforcing S twisted yarns 3, or at least one reinforcing S twisted yarn 3 extending adjacent to one or more reinforcing Z twisted yarns 3. By contrast, each yarn has the same S twist or the same Z twist, and therefore the same twisting direction over its entire length, as well as the same twist value. Such unidirectional reinforcing web 2 is referred to in the present description as "hybrid S / Z unidirectional web 2". The obtaining of twisted reinforcing yarns 3 with S twist or twisted reinforcing yarns 3 with Z twist is affected by the direction of rotation applied by the winding axis to the spool 7, in the twisting machine as shown in Figure 3 By using, within the same unidirectional reinforcing web 2, several types of twisted reinforcing yarns 3 as defined within the scope of the present application, i.e. at least one with S twist and at least one with Z twist, it is possible to limit the likelihood of defects occurring within the obtained unidirectional reinforcing web 2, in particular the risk of gaps or overlaps between the yarns laid in succession, as well as the risk of waviness. The use within the same unidirectional web of the two types of twist (S twist and Z twist) proposed within the scope of the present application tends to flatten the local waviness caused by Z twist and S twist having different directions. By combining these two types of yarn in the same unidirectional web, the manufacture and use of hybrid S twist and Z twist yarns is simplified, and tends to produce a more acceptable quality in terms of gaps and overlaps observed in the resulting web, as will be shown in the following examples.

[0102] As shown in Figure 1C The unidirectional web 2 formed by a plurality of carbon reinforcing yarns 3 can be divided into two equal parts, each extending on either side of a plane A extending perpendicular to the surface of said unidirectional web 2 (and therefore extending perpendicular to the surfaces S4 and S5 of the two face yarns 4, 5 when the web is combined with these two face yarns) and parallel to the direction of extension of the unidirectional web 2.

[0103] In the reinforcing material according to the present application, the (hybrid S / Z type) unidirectional web 2 contains more than 3 individually twisted carbon reinforcing yarns 3 having a twist of between 3 twists per meter and 15 twists per meter, preferably between 6 twists per meter and 12 twists per meter, wherein:

[0104] - in the case where the total number of twisted carbon reinforcing yarns 3 forming the unidirectional web 2 is even:

[0105] * the number of twisted carbon-reinforced S-twist yarns 3 on one side of the plane A and the number of twisted carbon-reinforced S-twist yarns 3 on the other side of the plane A are each independently an integer number within the range {[(total number of yarns) / 4]-35%; [(total number of yarns) / 4]+35%}, if the defining formula does not lead to an integer number, each end of the range is rounded to the nearest integer, the other twisted reinforcing yarns 3 being Z-twist yarns (definition PI);

[0106] * this means that the number of twisted reinforcing Z-twist yarns 3 on one side of the plane A and the number of twisted reinforcing Z-twist yarns 3 on the other side of the plane A are each independently an integer number within the range {[(total number of yarns) / 4]-35%; [(total number of yarns) / 4]+35%}, if the defining formula does not lead to an integer number, each end of the range is rounded to the nearest integer, the other twisted reinforcing yarns 3 being S-twist yarns (definition P2);

[0107] - in the case where the total number of twisted carbon-reinforced yarns 3 forming the unidirectional net 2 is an odd number:

[0108] * the number of twisted reinforcing S-twist yarns 3 on one side of the plane A and the number of twisted reinforcing S-twist yarns 3 on the other side of the plane A are two integer numbers or two half-integers and are each independently within the range {[(total number of yarns) / 4]-35%; [(total number of yarns) / 4]+35%}, if the defining formula does not lead to an integer number or to an integer plus half, each end of the range is rounded to the nearest integer or to an integer plus half, the other twisted reinforcing yarns 3 being Z-twist yarns (definition II);

[0109] * this means that the number of twisted reinforcing Z-twist yarns (3) on one side of the plane A and the number of twisted reinforcing Z-twist yarns 3 on the other side of the plane A are two integer numbers or two half-integers and are each independently within the range {[(total number of yarns) / 4]-35%; [(total number of yarns) / 4]+35%}, if the defining formula does not lead to an integer number or to an integer plus half, each end of the range is rounded to the nearest integer or to an integer plus half, the other twisted reinforcing yarns 3 being S-twist yarns (definition I2).

[0110] The plane A is a plane parallel to the overall direction of extension of the unidirectional net 2, dividing said unidirectional net into two equal parts perpendicularly to its surface. Figure 1C A material according to the application is shown, said material comprising a unidirectional net 2 formed by a series of twisted reinforcing SZSZSZ yarns 3, on which a plane A is shown.

[0111] The "each independently within the range" in the definitions PI, P2, II and I2 means that the two numbers concerned are within the range, but can be the same or different.

[0112] As an example of possible configurations in the case of a total number of twisted reinforcing yarns 3 forming the unidirectional net 2 which is odd, if this total number of twisted reinforcing yarns 3 is 17 (thus, there are 8.5 yarns on each side of the plane Δ), we have:

[0113] - according to definition 11, the range {[(total number of yarns) / 4] - 35%; [(total number of yarns) / 4] + 35%} is equal to {[(17 / 4] - 35%; [(17) / 4] + 35%} = {4.25 - 35% (4.25); 4.25 + 35% (4.25)}, which, rounded to the nearest integer, gives {3; 5.5}. Thus, there can be between 3 and 5.5 S-twisted yarns on each side of the plane Δ, i.e. between 6 and 11 S-twisted yarns in total, the other yarns being Z-twisted yarns, i.e. between 6 and 11 Z-twisted yarns in total, between 3 and 5.5 Z-twisted yarns on each side of the plane Δ;

[0114] - according to definition 12, we obtain the same number of possible S- and Z- twisted yarns on each side of the plane Δ.

[0115] Other examples of particularly suitable sequences of twisted reinforcing yarns 3 laid continuously to form a hybrid S / Z unidirectional net 2 include the following sequences: SZZS, SZSZ, SZSZS, SSZZSS, SZSSZS, SZSZSZ SSZZSSZZ.

[0116] For such configurations, the number of twisted reinforcing S-twisted yarns and the number of twisted reinforcing Z-twisted yarns 3 in the unidirectional reinforcing net 2 are more balanced, resulting in a unidirectional net 2 which is easier to manufacture and of higher quality. Indeed, in this case, the alignment between the twisted reinforcing yarns 3 is facilitated during the formation of the unidirectional reinforcing net 2, and the gaps, ripples and / or overlaps between the twisted reinforcing yarns 3 laid in parallel and continuously are reduced, as explained in the examples. Furthermore, during the automated production of a plurality of reinforcing materials 1 in parallel, as described in the application WO 2010 / 061114, the cutting of the non-woven material at the junction between two reinforcing materials 1 produced in parallel results in sharper edges and a more homogeneous material in this case.

[0117] In addition, the reinforcing material 1 produced from such hybrid S / Z unidirectional nets will thus also have a better quality, and thus the composite parts produced from it. In addition, the laying with the aid of automatic laying devices, such as those described in EP 2 376 276, can use such reinforcing material more precisely. As will be explained in the examples, such reinforcing material 1 better remains centred in the guides or guiding members (of the groove type or particularly of the comb type) present at the level of the head or laying finger of the automatic laying device, whereas the reinforcing material 1 made from reinforcing S twist yarns 3 only or from reinforcing Z twist yarns 3 only or more generally unidirectional reinforcing nets 2 not satisfying the definitions PI, P2, II and I2 tends to deviate from the centre and to abut on the edges of the guides or guiding members on which they travel.

[0118] In particular, the unidirectional reinforcing nets 2 comprising sequences of S twist and Z twist reinforcing yarns 3 alternated completely are preferred, especially those corresponding to the configurations, i.e. sequences of twist reinforcing yarns 3 laid continuously (SZ)i, S(ZS)j, Z(SZ)j, with i and j being integers, in particular in the range 1 to 20, preferably in the range 1 to 10. In particular, i and j are in the range 2 to 20, preferably in the range 2 to 10.

[0119] Other hybrid S / Z unidirectional net configurations that are particularly satisfactory are those having the same number of S twist yarns and thus the same number of Z twist yarns on both sides of the plane Delta. The following configurations are some examples: SZZS, SZSZ, SZSZS, SZSSZS.

[0120] Other hybrid S / Z unidirectional net configurations that are particularly satisfactory are those that are symmetrical about the plane Delta. Some examples of these configurations are SZZS, SZSZS, SZSSZS, SZSSZSSZS.

[0121] The use of hybrid S / Z unidirectional reinforcing nets 2 and in particular those more precisely described within the scope of the application thus solves the double technical problem during the manufacture and laying of the reinforcing material 1 obtained. These materials in particular offer the possibility of being produced and laid using industrial methods.

[0122] The use of hybrid S / Z unidirectional reinforcing nets 2 and in particular those more precisely described within the scope of the application is particularly suitable for producing unidirectional nets 2 and thus reinforcing materials 1 having a width of 5 mm to 60 mm. The width is measured perpendicular to the general direction of extension of the unidirectional net 2. In particular, there are automatic laying devices for applying materials having a width of 6.35 mm, 12.7 mm, 38.1 mm and 50.8 mm and can be used within the scope of the application.

[0123] Advantageously, each twisted carbon yarn 3 that participates in forming the unidirectional reinforcement net 2 has a twist value that is substantially the same over its entire length. Note that all twisted carbon yarns 3 that form the unidirectional reinforcement net 2 can have the same or different twist values. Preferably, all twisted carbon yarns 3 that form the unidirectional reinforcement net 2 have the same twist value, even if their twist direction (S or Z) is different.

[0124] It should be understood that twisting causes a change in the width of the twisted carbon yarn.

[0125] The effect of the twisting process on the width of the twisted carbon yarn is described in the following description.

[0126] Figure 4 A method of measuring the width of the carbon yarn before and after implementing the twisting machine operation explained above is depicted. The carbon yarn whose width is to be measured is unwound from a spool 13 to ensure that it successively passes above a first fixed cylindrical rod 14, below a second fixed cylindrical rod 15 and above a third fixed cylindrical rod 16, before being taken up on a take-up spool 17. Typically, the tension of the carbon yarn leaving the spool 13 is 150 g to 300 g. The cylindrical rods 14-16 are installed so as to enable the width of the carbon yarn to be measured under reproducible and predetermined tension conditions. After being stretched as it passes through the first fixed cylindrical rod 14 and the second fixed cylindrical rod 15, the carbon yarn expands at the third cylindrical rod 16, above which a matrix camera 18 is positioned. For example, the first, second and third cylindrical rods 14-16 have diameters of 40 mm, 20 mm and 30 mm, respectively, while the center-to-center distance first between the first and second cylindrical rods and second between the second and third cylindrical rods is 50 mm and 20 mm in the horizontal direction and 15 mm and 10 mm in the vertical direction, respectively. During the run of the carbon yarn, measurements of the width of the carbon yarn are taken approximately every 5 mm over a length of 100 meters, with the aid of the camera 18.

[0127] Measurements were taken on carbon fibers from HEXCEL Corporation, Stamford, Connecticut, USA, having different linear densities, different numbers of filaments and different twists, as shown in Table 1 below.

[0128] [Table 1]

[0129]

[0130] The measurements taken on the carbon yarns in Table 1 show in Figure 5 that gives the variation of the average width of the carbon yarns as a function of the twist for the various carbon yarns. Figure 5 It is clearly shown that the average width of the carbon yarns decreases as the twist increases, which is to be expected since twisting causes the filaments of the twisted carbon yarn to tighten.

[0131] Figure 6 The examination (which shows the standard deviation of the average width as a function of twist for the various carbon yarns in Table 1) reveals that the standard deviation of the width decreases with increasing twist. In other words, twisted carbon yarns tend to tighten more uniformly with increasing twist. Therefore, with increasing twist, carbon yarns with a parallelepiped cross-section tend to become circular reinforcing yarns with a low standard deviation. It should be noted that untwisted reinforcing yarns have a lower standard deviation than twisted reinforcing yarns, and a twist greater than 14 twists / meter (t / m, twist / meter, or tpm) should be achieved to expect such low width variation.

[0132] It is important to understand that the width distribution of carbon yarns will affect the ability to use them to manufacture a web with a given basis weight.

[0133] For example, a 210 g / m² net would require 12K IMA yarns laid side-by-side every 2.12 mm to theoretically achieve complete net coverage. The calculations are as follows:

[0134] Required width [mm] for a given basis weight = fineness of yarn used [tex] / basis weight [g / m] 2 The unit of measurement for yarn is tex, which is the weight of 1000m of yarn, expressed in grams.

[0135] In practice, if the average width of the carbon yarn is statistically at least 75% of this so-called "target" width value, it is possible to produce a web of satisfactory quality. Those skilled in the art can usually determine this target width value through repeated experimentation.

[0136] Table 2 below provides the target width values ​​by basis weight (gram weight) and by the carbon yarn used:

[0137] [Table 2]

[0138]

[0139] Figure 7 to Figure 11 The graph shows the percentage of values ​​above the target width value for various weights as a function of the twist of various carbon yarns.

[0140] Figure 7 It shows that for 140g / m 2 The website:

[0141] -For IMA-12K fiber, the web can be made solely of untwisted carbon yarn;

[0142] - For IM7-6K fibers, the web can be made solely from carbon yarn with a twist of 8 twists / meter or less.

[0143] Figure 8 It is shown that for a web of 210 g / m 2 :

[0144] - for IMA-12K fibers, the web can be made of carbon yarns with a twist less than or equal to 8 twists per meter;

[0145] - for IM7-6K fibers, the web can be made of carbon yarns with a twist up to 14 twists per meter.

[0146] Figure 9 It is shown that for a web of 280 g / m 2 , the grammage becomes high enough to use carbon yarns with all twist values in the range.

[0147] Figure 10 It is shown that for a web of 252 g / m 2 made of AS7-12K fibers, the web can be made of carbon yarns with a twist less than or equal to 6 twists per meter only.

[0148] Figure 11 It is shown that for a web of 350 g / m 2 , the grammage becomes high enough to use carbon yarns with all twist values in the range.

[0149] Therefore, for a given basis weight, it seems possible to define a limit of available twisting that can be used for each type of carbon yarn, which also makes it possible to choose not only to use a yarn but also to apply a twist, depending on the desired grammage of the unidirectional web.

[0150] Within the scope of the present invention, the unidirectional reinforcement web 2 has a grammage ranging from 126 g / m 2 to 1000 g / m 2 , in particular from 126 g / m 2 to 500 g / m 2 , from 126 g / m 2 to 420 g / m 2 , or from 126 g / m 2 to 280 g / m 2 , from 280 g / m 2 to 500 g / m 2 , or from 420 g / m 2 , or from 210 g / m 2 to 280 g / m 2 .

[0151] The grammage of the unidirectional web within the reinforcement material corresponds to the grammage of the unidirectional web before it is combined with one or more porous polymer layers, typically one or more face veils, but it is not possible to measure the grammage of the unidirectional web before it is combined with the face veils 4, 5, as the carbon yarns have no cohesion between them. The grammage of the carbon fiber reinforced web can be determined from the grammage of the reinforcement material 1, typically the unidirectional web 2 and the two face veils 4, 5. If the basis weight of the one or more porous polymer layers, typically face veils, present is known, then the basis weight of the unidirectional web can be deduced. Advantageously, the basis weight is determined by chemical attack (or also possibly by pyrolysis) of the reinforcement material by one or more porous polymer layers, typically one or more face veils. This type of method is routinely used by the person skilled in the art to determine the carbon fiber content of a woven fabric or composite structure.

[0152] The method for measuring the grammage of the reinforcement material 1 is described below. The grammage of the reinforcement material is measured by weighing a cut sample of 100 cm 2 (i.e. a diameter of 113 mm). To facilitate the cutting of the flexible reinforcement material sample, the reinforcement material is placed between two sheets of 447 g / m2and 0,450 mm thick smooth-faced cardboard from Cartonnage Roset (Saint Julien en Genevois, France) to ensure a certain rigidity of the assembly. A pneumatic circular punch from Novi Profiber (Eybens, France) is used to cut the assembly; 10 samples are taken per manufactured reinforcement product type.

[0153] Generally, the method for preparing the reinforcement material 1 according to the application comprises the following successive steps:

[0154] a1) providing a unidirectional reinforcement web 2 as defined within the scope of the application, called hybrid unidirectional web S / Z,

[0155] a2) providing at least one or two porous polymer layers 4, 5,

[0156] a3) combining the one or each porous polymer layer with each face of the unidirectional reinforcement web.

[0157] Generally, the unidirectional reinforcement web 2 of step a1) will have a grammage equal to the desired grammage in the final reinforcement material 1 and a width equal to the desired width of the final reinforcement material 1.

[0158] Advantageously, said production process comprises, upstream of step a1 ), a step of production of said unidirectional reinforcement net 2, said step comprising, first, applying to one or to a series of carbon yarns 3 having S twist a twist of 3 turns / m to 15 turns / m, said twist being applied individually to each carbon yarn 3, and, second, applying to one or to a series of carbon yarns 3 having Z twist a twist of 3 turns / m to 15 turns / m, said twist being applied individually to each carbon yarn 3.

[0159] In particular, said process comprises, upstream of step a1 ), a step of production of said unidirectional reinforcement net 2, said step comprising, first, applying to one or to a series of carbon yarns 3 having S twist a twist of 3 turns / m to 15 turns / m, said twist being applied individually to each carbon yarn 3, and, second, applying to one or to a series of carbon yarns 3 having Z twist a twist of 3 turns / m to 15 turns / m, said twist being applied individually to each carbon yarn 3.

[0160] i) first, applying to one or to a series of carbon yarns 3 having S twist a twist of 3 turns / m to 15 turns / m, said twist being applied individually to each carbon yarn 3, and, second, applying to one or to a series of carbon yarns 3 having Z twist a twist of 3 turns / m to 15 turns / m, said twist being applied individually to each carbon yarn 3.

[0161] ii) aligning the twisted reinforcement yarns thus obtained and arranging said yarns in succession so as to form a unidirectional reinforcement net as defined within the scope of the present application, referred to as hybrid S / Z unidirectional net, having any of the configurations described herein.

[0162] Within the scope of the present application, the use of yarns not all having the same S twist or Z twist type as previously defined facilitates the alignment and arrangement of the yarns in step ii). Thus, in step ii), the aligned yarns will be selected so as to obtain one of the hybrid S / Z unidirectional nets as described herein.

[0163] Furthermore, within the scope of the present application, the production of the reinforcement material by passing the reinforcement material through motorized conveying systems or devices during production can be used to incorporate one or more porous polymeric layers on one face of the unidirectional reinforcement net in a continuous manner.

[0164] According to one advantageous feature, the one or more porous polymeric layers 4, 5 used, which can in particular be non-woven materials, have hot-melt qualities, and the incorporation of step a3) is obtained by laying one or more porous polymeric layers respectively on one or each face of the unidirectional reinforcement net, said laying being accompanied or followed by heating the polymeric fibers, causing them to soften or melt, and then cooling.

[0165] Advantageously, the unidirectional net 2 has incorporated on each of its faces a porous polymeric layer 4, 5 to produce a reinforcement material 1, an example of which is shown in Figure 1A and Figure 1CThe use of symmetrical reinforcement materials makes it possible to avoid any stacking errors during their manual or automatic lay-up to form a composite part and thus limit the creation of defects, in particular of intermediate plies without veil. This is the reason why the unidirectional web 2 advantageously incorporates a porous polymer layer and in particular a polymer fibrous veil 4, 5 on each of its faces, the two porous polymer layers (typically veils) 4, 5 being identical.

[0166] By "porous polymer layer" is meant a permeable layer allowing the passage of a liquid, such as a resin, through the material or the stack containing it during the formation of the composite part. In particular, the openness factor of such a layer, determined according to the method described in the application WO 2011 / 086266, is in the range of 1% to 70%, preferably in the range of 30% to 60%. Examples of porous layers include porous membranes, scrim made by interlacing of yarns, layers obtained by powder coating, layers obtained by application of a liquid polymer, woven fabrics and nonwoven materials. The porous layer is said to be polymeric in that it is composed of a polymer or a mixture of polymers. In particular, the porous polymer layer can be made of one or more thermoplastic polymers, one or more thermosetting polymers, one or more partially cross-linked thermoplastic polymers, a mixture of such polymers, or a mixture of thermosetting or thermoplastic polymers. Examples of thermoplastic polymers classically used in dry stacks (and therefore for the formation of the porous layer(s) present) are chosen from: polyamides (PA: PA6, PA12, PA11, PA6,6, PA6,10, PA 6,12...), copolyamides (CoPA), polyamide-block-ethers or esters (PEBAX, PEBA), polyphthalamides (PPA), polyesters (polyethylene terephthalate - PET -, polybutylene terephthalate - PBT -...), copolyesters (CoPE), thermoplastic polyurethanes (TPU), polyacetals (POM...), polyolefins (PP, HDPE, LDPE, LLDPE... polyether sulfone (PES), polysulfone (PSU...), polyphenylsulfone (PPSU...), polyether ether ketone (PEEK), polyether ketone ketone (PEKK), poly(phenylene sulfide) (PPS), polyetherimide (PEI), thermoplastic polyimides, liquid crystal polymers (LCP), phenoxy-based, block copolymers such as styrene-butadiene-methyl methacrylate (SBM) copolymers, methyl methacrylate-butyl methacrylate (MAM) copolymers and mixtures thereof. The porous polymer layer can also be composed of or contain partially cross-linked thermoplastic polymers, as described in WO 2019 / 102136. The person skilled in the art can adjust the choice of the polymer(s) constituting the polymer part of the dry stack according to the choice of the resin that will be injected or infused when the composite part is subsequently produced. Within the scope of the present invention, the nonwoven material or veil or more generally the porous polymer layer used advantageously has thermoplastic properties and in particular consists of a thermoplastic polymer, a partially cross-linked thermoplastic polymer, a mixture of such polymers, or a mixture of thermoplastic and thermosetting polymers. The nonwoven material or veil is preferably made of a thermoplastic material as described above.

[0167] Within the scope of the present application, the total weight of the porous polymer layer 4 or 5 present, when there is only one according to the reinforcing material 1 of the application, or the weight of all the porous polymer layers 4, 5 present, when there are several according to the reinforcing material 1 of the application, represents no more than 10% of the total weight of the reinforcing material 1 according to the application, typically between 0.5% and 10% of the total weight of the reinforcing material 1 and preferably between 2% and 6% of its total weight.

[0168] A particularly advantageous embodiment of the porous polymer layer is a nonwoven material, preferably identical.

[0169] "Nonwoven" or "veil" conventionally means an assembly of continuous or staple fibres that can be arranged randomly. These nonwoven materials or veils can be produced, for example, by dry-laid, wet-laid or spun-laid processes, for example by extrusion ("spunbond"), melt-blown extrusion ("melt-blown"), fibreising spray or solvent spinning ("electrospinning", "flash spinning", "force spinning"), all well known to the person skilled in the art. In particular, the average diameter of the constituent fibres of the nonwoven material can be in the range 0.5 pm to 70 pm and preferably 0.5 pm to 20 pm. The nonwoven material can be made of staple fibres or preferably continuous fibres. In the case of a nonwoven material made of staple fibres, the fibres can have, for example, a length of 1 mm to 100 mm. Preferably, the nonwoven material used provides a random and preferably isotropic coverage.

[0170] The thickness of the veils before their combination with the unidirectional web will be chosen according to the way in which the veils will be combined with the unidirectional web. Generally, their thickness will be very close to the desired thickness of the reinforcing material. It is also possible to choose to use veils of greater thickness that will be laminated at the temperature in the combination stage in order to reach the desired thickness. Preferably, the unidirectional web is combined on each of its large faces with two veils that are substantially identical in order to obtain a perfectly symmetrical reinforcing material. The thickness of the veils before their combination with the unidirectional carbon web is in particular 0.5 pm to 200 pm, preferably 10 pm to 170 pm. On the reinforcing material 1 according to the application, the thickness of each veil 4, 5 after its combination with the unidirectional web is in the range 0.5 pm to 50 pm, preferably in the range 3 pm to 35 pm. The thickness of the various veils before combination is determined using method A of NF EN ISO 9073-2 with a test area of 2827 mm 2 (60 mm diameter disc) and an applied pressure of 0.5 kPa.

[0171] Furthermore, the basis weight of the veil or veils 4, 5 is advantageously between 0.2 g / m 2 and 20 g / m2 within the range of 10 to 1000 g / m2.

[0172] The bond between the unidirectional web 2 and the one or more porous polymeric layers, typically one or more nonwoven materials, 4, 5, can be realized in a discontinuous manner, for example only at certain points or in certain areas, but preferably it is realized according to a bond extending over the entire surface of the web, classified as continuous.

[0173] The bond of the unidirectional web 2 with the two face veils 4, 5 is advantageously carried out according to one of the methods described in the patent application WO 2010 / 046609 or in the application WO 2010 / 061114. It is possible to use continuous production machines and production lines as described in these documents or in the inventive examples. In particular, it is within the scope of the present application to produce the reinforcement material by continuously carrying out the bond of the one or each porous polymeric layer on one face of the unidirectional reinforcement web and passing the reinforcement material produced by said bond by means of motorized conveying systems or devices. Such devices are, for example, conveyor belts driven by one or more drive rollers, after the unidirectional web has been laid on the porous polymeric layer or between the two porous polymeric layers, depending on the material produced, the reinforcement material circulates between the conveyor belts to ensure its or their application thereon.

[0174] Moreover, the bond of the unidirectional web with the two face veils can be realized by means of an adhesive layer, for example selected from epoxy adhesives, polyurethane adhesives, thermosetting glues, adhesives based on polymerizable monomers, structural acrylic or modified acrylic adhesives and hot-melt adhesives. However, most commonly, the bond is realized by means of the hot-melt qualities of the face veils when the latter are hot, for example during a hot compression step which allows to ensure the adhesion between the unidirectional web and the face veils. This step causes the thermoplastic fibers of the face veils to soften so that the unidirectional web can be adhered to the face veils upon cooling. The heating and pressure conditions are adapted to the material of the face veils as well as to their thickness. Typically, the hot compression step is carried out at a temperature within the range of Tf veil - 15 °C to Tf veil + 60 °C (where Tf veil designates the melting temperature of the face veils) and at a pressure of 0.1 MPa to 0.6 MPa over the entire surface of the unidirectional web. It is thus possible to realize a face veil compression ratio in the range of 1 to 10 before and after the bond. The step of laminating the face veils to the unidirectional carbon web 2 is also essential to properly control the final thickness of the reinforcement material 1. Indeed, depending on the temperature and pressure conditions, in particular during the lamination process, it is possible to vary and thus adjust the thickness of the face veils present on each side of the reinforcement material.

[0175] The reinforcement material according to the application is easy to handle because of the presence of one or more porous polymer layers and in particular thermoplastic veils laminated on each face of the unidirectional web. This architecture also facilitates cutting along non-parallel directions of the fibers of the unidirectional web, in particular transversely or obliquely to the fibers of the unidirectional web, without particular abrasion.

[0176] The reinforcement materials 1 according to the application are flexible and spoolable. They can be produced in long lengths, corresponding to the length of carbon yarn available. Typically, after manufacture, they are spooled in the form of a roll on a spool, then used for the subsequent manufacture of preforms and parts.

[0177] The application even more particularly relates to reinforcement materials having a width greater than 7 mm, preferably greater than 12 mm and more preferentially in the range 12 mm to 51 mm. Furthermore, the application is also particularly suitable for reinforcement materials having a length greater than 2 m, in particular a length of 2 m to 5000 m, preferably 100 m to 2000 m. Thus, according to a preferred embodiment within the scope of the application, the reinforcement material according to the application has a width greater than 7 mm and a length greater than 2 m, and advantageously a width in the range 12 mm to 51 mm and a length in the range 2 m to 5000 m, preferably 100 m to 2000 m. The width of the material is its average width taken perpendicularly to the plane Δ, i.e. taken perpendicularly to the general direction of extension of the unidirectional web: the width can be measured using any appropriate device, in particular a camera, by taking a measurement every 10 cm over the entire length of the material and taking the arithmetic mean of the measurements obtained. The length of the material is preferably measured on the level of the plane Δ. In particular, the width of the reinforcement material 1 can be measured by making it run at a constant speed of 1.2 m / min under a constant tension of 200 cN to 400 cN and by making it pass in front of a camera (for example of the Baumer Optronic Type FWX 20 type, focal length 20 mm, 1624 x 1236 pixels (Germany Baumer Optronic Gmbh - calibration of the camera as follows: 1 pixel corresponds to 0.05 mm)) or another camera suitable for larger widths of reinforcement material, at a distance of 265 mm and without support at this point.

[0178] For the production of composite material parts, stacks or layups of reinforcement material according to the application are manufactured, also called plies. Conventionally, the material according to the application is cut to the desired dimensions for the production of the part, the ply, the stack or the preform to be manufactured. In the stack, a plurality of plies of reinforcement material are stacked on top of one another.

[0179] When the width of the reinforcement material is sufficient to produce the desired part and when the part is not extremely complex, the ply can be made from a single reinforcement material according to the application. But generally, in the case of large or complex parts, the ply is composed of an assembly of reinforcement materials 1 according to the application arranged in succession to cover the entire surface necessary to produce the desired part. In this case, precise placement of the reinforcement materials must be achieved. In automated processes, the device for conveying and applying the reinforcement materials comprises one or more guide members or guides in which the reinforcement materials are conveyed and transported. The devices comprising a layup head equipped with such guide members or guides are particularly described in documents WO 2006 / 092514 and EP 2 376 276. The companies Coriolis Composites SASU (rue Condorcet 56530 Queven, France), MTorres Disenos Industriales SAU (Torrez de Elorz, Navarra, Spain), ElectroImpact Inc (Mukilteo WA 98275, USA), Mikrosam DOO (7500 Prilep Macedonia) also provide such devices. Within the scope of the application, the central reinforcement material 1 according to the application comprising hybrid S / Z unidirectional webs and in particular one of those more precisely described within the scope of the application leads to more precise placement and thus reduces the likelihood of defects such as gaps, overlaps, wrinkles or ripples during the layup process. Thus, the parts made from the reinforcement material 1 according to the application comprising hybrid S / Z unidirectional webs and in particular one of those more precisely described within the scope of the application are particularly satisfactory.

[0180] Furthermore, to produce a composite part, a plurality of plies are placed one on top of the other to obtain a ply stack. Flaws on the reinforcement material 1 are thus reproduced in each ply and are thus exacerbated on the stack. For this reason, again, the reinforcement material 1 according to the application comprising hybrid S / Z unidirectional webs, which has more homogeneous and reproducible characteristics, is particularly advantageous. In the resulting stack, the plies are generally arranged so that at least two unidirectional webs of the plies are oriented in different directions. From one ply to another, all the unidirectional webs or only some of them can have a different direction, while others can have the same direction. The preferred orientations are generally the directions at 0°, +45° or -45° (also corresponding to +135°) and +90° angles with the main axis of the part to be produced. The main axis of the part is generally the largest axis of the part and 0° merges with this axis. It is possible, for example, to manufacture a quasi-isotropic, symmetrical or oriented stack by choosing the orientations of the plies. Examples of quasi-isotropic stacks include stacks according to the angles 45° / 0° / 135° / 90° or 90° / 135° / 0° / 45°. Examples of symmetrical stacks include 0° / 90° / 0° or 45° / 135° / 45°. Before the addition of the resin necessary to produce the part, it is possible to join the plies within the stack together, in particular by an intermediate step of preforming under temperature and vacuum or welding at several points after each addition of a ply, and thus to produce a preform. In particular, assemblies of 2 to 300 plies, in particular 16 to 100 plies, can be considered.

[0181] Advantageously, the stack is not attached by stitching or knitting, but instead by welding resulting from the polymer properties and in particular the thermoplastic properties of the porous polymer layer present within the stack. To this end, a heating / cooling operation is carried out on the entire surface of the stack or at least in some areas of the surface of the stack. The heating causes the polymer porous layer to melt or at least soften. This bonding using the thermoplastic properties of the polymer porous layer is advantageous because it makes it possible to avoid all the drawbacks of the presence of the stitching or knitting yarns, such as in particular the problem of waviness, microcracks and a reduction in the mechanical properties of the composite part subsequently obtained.

[0182] The stacking can be achieved by adding the plies one at a time and ensuring the adhesion after each ply addition. In particular, one example is the automatic ply lay-up as described in patent applications WO 2014 / 076433 and WO 2014 / 191667. In addition, all the plies applied (by pre-heating the plies, one at a time, or not) can be reheated all at once, in order to obtain a shaped preform, for example, from flat laid plies. Then, the person skilled in the art can use the conventional means for thermoforming, with the application of temperature and pressure (for example, vacuum or pressure systems). In particular, the lay-up of the reinforcement material according to the application can be carried out continuously according to the known methods abbreviated as AFP (Automated Fiber Placement) or ATL (Automated Tape Lay-up), for example as described in the above-mentioned documents WO 2014 / 076433 Al and WO 2014 / 191667, with the application of pressure perpendicular to the laying surface in order to apply it thereto.

[0183] In order to produce the composite part, a thermosetting or thermoplastic type resin or matrix or a mixture of thermosetting and thermoplastic resins is then added, for example by injection into the mold containing the plies (Resin Transfer Molding (RTM) method) or by infusion (through the thickness of the plies: Liquid Resin Infusion (LRI) method or Resin Film Infusion (RFI) method). According to one non-preferred embodiment, it is also possible to carry out a manual coating / impregnation on each ply with the aid of a roller or brush, applied successively to the form of the mold used, before the stacking.

[0184] The matrix used is of the thermosetting or thermoplastic type, or a mixture of thermoplastic and thermosetting resins. The injected resin is chosen, for example, from the following thermosetting polymers: epoxides, unsaturated polyesters, vinyl esters, phenol formaldehyde resins, polyimides and bismaleimides.

[0185] The composite part is then obtained after a heat treatment step. In particular, the composite part is generally obtained by carrying out a heat treatment as recommended by the suppliers of the polymers considered and known to the person skilled in the art, with the aid of the conventional hardening cycle of the polymers considered. This hardening step, which consolidates the desired part, is carried out by polymerization / crosslinking according to a defined cycle under temperature and pressure, then cooling. The pressure applied during the treatment cycle is low in the case of vacuum infusion and higher in the case of injection into an RTM mold.

[0186] The method for bonding the above-mentioned stack can also be implemented with any type of reinforcement material intended to be combined with a thermosetting resin to produce a composite part, made of a unidirectional carbon fiber web combined on each of its faces with a thermoplastic fiber veil and in particular with a reinforcement material other than those defined in the claims of the present patent application. Indeed, regardless of the unidirectional web and veil used, such stacks are valuable in terms of drape and permeability. Of course, preferably, the reinforcement material enables a high fiber volume ratio (FVR) to be achieved by means of vacuum infusion, in terms of thickness and grammage, in line with those described within the scope of the present application.

[0187] The following examples illustrate the present application but are not intended to be limiting.

[0188] Part A

[0189] A first series of tests was carried out to obtain the data presented in Table 3 below. In this series of tests, the so-called twisted material has only twisted S yarns.

[0190] [Table 3]

[0191]

[0192]

[0193] In Table 3 above, the reinforcement materials tested comprise a unidirectional reinforcement web combined with a veil on each side.

[0194] The 12K intermediate modulus (IM) carbon yarns sold by the company HEXCEL, Stanford, Connecticut, USA, were used for the unidirectional reinforcement web. Comparative material 1 uses such carbon yarns which are not twisted but micro-perforated after the combination of the unidirectional web with the veil. Materials 2 to 6 are reinforcement materials in which the unidirectional web consists of individually twisted carbon yarns (twisted yarns) as described above with a twist value according to the present application, all having an S twist, which does not correspond to the present application. Comparative materials 7 to 10 are reinforcement materials made of twisted yarns having a twist greater than that envisaged by the present application and cannot be manufactured because the material separates during the production phase or during the handling or lay-up phase, thus making it unusable.

[0195] For the porous polymer layer chosen from non-woven materials, a 4 g / m2 copolyamide non-woven material 1R8 D04 sold by Protechnic was used. According to the patent application WO 2010 / 046609, the veil is combined with the unidirectional carbon yarn web. More precisely, the reinforcement material 1 according to the present application was manufactured on a production line using the machine and parameters as described in the application WO 2010 / 061 114 and is described hereinafter with reference to Figure 18 is described.

[0196] The carbon yarns 3 of the desired twist are unwound from the respective bobbins 30 of carbon yarns attached to the creel 40, pass through the comb 50, are fed into the machine axis by means of the guide rollers 60, the comb 70 and the guide bars 80a.

[0197] The carbon yarns 3 are preheated by means of the heating bars 90 and then spread to the desired carbon basis weight of the unidirectional web 2 by means of the spreading bars 80b and the heating bars 100. The rolls 13a and 13b of the face yarns 4, 5 are unwound without tension and transported by means of the continuous belts 15a and 15b fixed between the freely rotating non-motorized rolls 14a, 14b, 14c and 14d and the heating bars 12a, 12b.

[0198] The face yarns 4 and 5 are preheated in the regions 11a and 11b before contact with the carbon yarns 3 and are laminated on either side of the two heating bars 12a and 12b in which the air gap is controlled. The calender 16 can be cooled and then exerts pressure to the unidirectional web with the face yarns on each side to produce the reinforcement material 1 in the form of a tape. The deflection rolls 18 enable the reinforcement material 1 to be redirected to a traction system comprising a motor-driven take-up triad 19 and then to a winding arrangement 20 to form a roll of the reinforcement material 1 thus formed.

[0199] It should be noted that in this production line the belts are not motorized, but are instead pulled by the reinforcement yarns 3 themselves.

[0200] Furthermore, as explained in the application WO 2010 / 061114 and presented in its Figure 8 In the meantime, a plurality of reinforcement materials according to the application in the form of a tape are manufactured. Each twisted carbon yarn to form a unidirectional web to be formed is drawn from a selected twisted yarn roll previously manufactured. The unidirectional webs of the desired width are made parallel and spaced so that there is enough space left between the unidirectional webs. Thus, a single non-woven fabric covering each unidirectional web 2 and the gap (corresponding to the face yarns 4 and 5) is combined with all the unidirectional webs 2 on each of their faces. After the non-woven material is laminated to the webs, cutting is then performed between each unidirectional web formed by means of a heated cutting element, resulting in various reinforcement materials according to the application produced continuously. The gap between each unidirectional web is in the range of 0.5 mm to 2 mm, so that cutting can be performed between each unidirectional web along their edges, resulting in various reinforcement materials produced continuously and in parallel.

[0201] 1) Thickness under vacuum:

[0202] In the automated layup process of complex shapes or thick preforms, it is important to minimize material over-limits and therefore achieve an application material thickness close to the final thickness of the composite part. Indeed, if the material exhibits significant over-limits, resulting in a thickness much greater than the final thickness after lamination, significant defects will appear on the part. These defects will primarily be due to excessive length and will introduce wrinkles. This is unacceptable to those skilled in the art. To characterize this property, the thickness of the preform is measured before and after placement under vacuum, and after automated layup.

[0203] like Figure 12 As shown, a 200x200mm preform P is formed with a quasi-isotropic symmetrical stack, more precisely with a layup of [+45 / 0 / -45 / 90]3s. The preform P is placed on a plate. Thickness is measured using a FANUC robot and a HEIDENHAIN / ST3077 LVDT probe. The probe tip is a 50mm diameter round key. The probe measures the preform thickness at five points P1 to P5, thus obtaining the average thickness value of the preform. Measurements are taken every 50mm along the x-axis and every 50mm along the y-axis.

[0204] The preform is then placed under vacuum (residual pressure less than 15 mbar) using a vacuum bag and pump. The thickness of the assembly is then measured and subtracted from the thickness of the consumables to obtain the thickness of the preform under vacuum.

[0205] Then, the ratio of the thickness without vacuum to the thickness under vacuum is calculated. The higher the ratio, the greater the thickness without vacuum compared to the thickness under vacuum, and the greater the likelihood of defects appearing on the final part. The goal is to minimize this ratio.

[0206] Table 4 below summarizes the ratio of thickness (without vacuum thickness) to theoretical thickness (in vacuum) for materials 1 to 6.

[0207] [Table 4]

[0208]

[0209] Compared to material 1 in the prior art, materials 2 to 6 using twisted yarns allow for minimizing the ratio of thickness without vacuum to thickness under vacuum. This, in turn, reduces the risk of exceeding limits.

[0210] 2) The effect of twisting on the quality of automatic layup.

[0211] Importantly, the automated lay-up process on the preform should not introduce defects. The structure of the carbon yarn can affect the quality of the lay-up. Therefore, it is necessary to determine whether the twisting of the carbon yarn affects the quality of the preform after lay-up.

[0212] More precisely, the twisting of the carbon yarns can have an impact on the so-called "shearing" phenomenon. During the superimposed laying-up of the reinforcement materials (unidirectional webs 2 and veils 4, 5), the carbon yarns of the plies located just below the next ply are subjected to shearing due to the pressure and movement of the robot head during the laying-up. This shearing is most prevalent in the area where the laying-up is initiated. This intra-ply shearing can intensify when laying-up several plies, which can lead to a local increase in the thickness of the preform and the appearance of defects such as wrinkles, abrasions, ply separations, etc., thus leading to poor quality preforms.

[0213] Industrial type automatic ply laying-up tests were carried out with twisted carbon yarns. The laying-up was carried out using a Coriolis C1 robot equipped with a Coriolis 161 / 4" AFP head and a 12 kw laser type heating arrangement. In this particular case, only 8 of the 16 webs were laid continuously at the same time. The heating rules followed are described in Table 5 below.

[0214] [Table 5]

[0215] V min (m / s) V max (m / s) P min (W) P max (W) Heating law, 1 ply 0.01 0.6 250 800 Heating law, X plies (X>1) 0.01 0.6 180 680

[0216] The plies of twisted carbon yarns were laid continuously at 0° on a vacuum table to form a preform of 500 mm (in the 0° direction) x 150 mm. The start of the laying of the carbon yarns according to the laying direction represented by the arrow F was always located in the same position on the preform (rectangular zone Z1 on the drawing). Figure 13 The thickness studied was therefore located in this zone Z1.

[0217] After the laying-up of each ply, the thickness measurement at the start of the laying-up of the preform (points P'1, P'2, P'3 within the Z1 zone) was carried out by means of a marked gauge, a support consisting of an aluminium bar and a 1 kg weight (representing a pressure of 0.02 bar applied to the preform at the time of the thickness measurement). During the measurement, the thickness measurement device was always positioned in the same position. After each ply laying-up, it was removed in order to allow the robot to pass and then repositioned after the laying-up. The laying-up was stopped when the quality of the preform was judged to be unsatisfactory.

[0218] The material 2 (Table 3) was compared with the comparative material 1.

[0219] Figure 14 The variation of the overrun as a function of the number of laid plies is shown for the comparative material 1 and the material 2.

[0220] Note that the overrun is defined as the ratio of the total thickness of the preform with X laid plies to the number of laid plies X, or:

[0221] Overrun (mm) = Total thickness of the preform (mm) / number of plies laid up

[0222] This indicates the ply average thickness and thus makes it possible to quantify the overrun phenomenon. In order to maximize the overrun phenomenon, the reinforcement material stack is composed of unidirectional layers extending at 0°.

[0223] As Figure 14 shown, in the case of twisted carbon yarns (material 2), the variation in thickness of each ply as a function of the number of plies laid up is lower than in the case of the microperforation method (comparative material 1). According to the results, the overrun of the preform after laying up is reduced and the quality is better in the case of twisted carbon yarns compared to the equivalent material made with non-twisted carbon yarns and microperforated according to the prior art.

[0224] 3) Effect of twisting on the transverse permeability of the reinforcement material:

[0225] It is important to verify that the present invention maintains the transverse permeability of the reinforcement material at the same level as that obtained with microperforated reinforcement material according to the prior art. This can be defined as the ability of a fluid to pass through a fibrous material. It is measured in m2. The values given in Table 6 below, which can be consulted for further details, were measured with the equipment and measurement technique described in the thesis entitled “Problématique de la mesure de la perméabilité transverse de préformes fibreuses pour la fabrication de structures composites” [Measuring the transverse permeability of fibrous preforms for the manufacture of composite structures] by Romain Nunez, defended on 16 October 2009 at the Ecole Nationale Supérieure des Mines de Saint Etienne.

[0226] In particular, the measurements were made by monitoring the thickness of the sample using two co-cylindrical chambers during the test, so that it is possible to reduce the “race-tracking” effect (fluid passing adjacent to or on “one side” of the material to be measured for permeability). The fluid used was water and the pressure was 1 bar + / - 0.01 bar. The preforms of diameter 270 mm were made according to the symmetrical orthotropic stack [+45 / 0 / 135 / 90] S, with 8 plies.

[0227] Table 6 below provides the transverse permeability values measured for 50%, 55% and 60% of fiber volume ratio (FVR) on Comparative Material 1 and Materials 2 to 6 using twisted yarns (see Table 3). Figure 15 The transverse permeability values for three samples with different fiber volume ratios for each material are summarized in Table 6.

[0228] [Table 6]

[0229]

[0230]

[0231] For a carbon fiber areal weight of 280 g / m 2 , a carbon yarn twisted at 10 twists per meter appears to produce a better average transverse permeability than a micro-perforated material according to the prior art.

[0232] For a carbon fiber areal weight of 350 g / m 2 , a carbon yarn twisted at 14 twists per meter appears to produce an average transverse permeability comparable to that of a micro-perforated material according to the prior art.

[0233] When the number of twists per meter is reduced (Material 3 compared to Material 2), the transverse permeability of the material decreases.

[0234] 4) Effect of carbon yarn twisting on the mechanical properties of the composite:

[0235] A 430 mm x 430 mm preform composed of a stacking sequence appropriate for the carbon weight was placed in a pressurized injection mold. A frame of known thickness surrounding the preform was used to achieve the desired FVR (fiber volume ratio). An epoxy resin sold under the reference HexFlow RTM6 by HEXCEL Corporation, Stanford, Connecticut, USA, was injected at 80°C at 2 bars into the preform, which was maintained at 120°C inside the press. The pressure applied by the press was 5.5 bars. When the preform was filled and the resin came out of the mold, the outlet pipe was closed and the curing cycle was started (3°C / min to 180°C, then 2 hours of post-cure at 180°C and cooling at 5°C / min).

[0236] The samples were then cut to appropriate dimensions for the open hole (OHC) and un-notched compact (UNC) compression tests summarized in Table 7 below.

[0237] [Table 7]

[0238]

[0239] Tests were performed with reinforcement materials 2 to 5 and comparative material 1 (Table 3). The results of the open hole compression (OHC) test are shown in Table 8 below.

[0240] [Table 8]

[0241]

[0242] In the prior art, it is known that the carbon weight can influence the mechanical properties. Generally speaking, the higher the carbon weight, the lower the mechanical compression properties. In the present case, the results were compared with the carbon equivalent grammage.

[0243] For a grammage of 210 g / m2, there is no difference between the open hole compression test (OHC) results of the comparative material and the so-called twisted material. The same conclusion can be drawn for a grammage of 280 g / m2. For a grammage of 350 g / m2, it is not possible to compare with the micro-perforated material because this option is not possible. 2 2 2

[0244] The results of the un-notched compression test (UNC) are shown in Table 9 below.

[0245] [Table 9]

[0246]

[0247]

[0248] The results of Table 9 allow the same conclusions to be drawn as for the open hole test.

[0249] 5) Effect of carbon yarn twisting on the transverse electrical conductivity:

[0250] 335 mm x 335 mm preforms were made from reinforcement plies, the number of which depends on the grammage of the carbon yarn. The stacking sequence is [0 / 90]ns, where ns is an integer number which depends on the grammage of the carbon reinforcement yarn in order to produce a panel with a final thickness of 3 mm and a fiber volume of 60%. The preforms were then placed in an injection mold under pressure. In the same way as for the mechanical compression test (see paragraph 4 above), the composite panels of reinforcement material / RTM6 were formed by means of an injection method (same parameters as for the compression plates).

[0251] ​​​Twenty four 40mm x 40mm coupons were pre-cut using a water jet cutter, evenly distributed across the panel. The two surfaces of the pre-cut panel were then sandblasted to expose the carbon fibre. Next, the front and back surfaces of the panel were treated and then an electrically conductive metal layer, typically tin and zinc, was applied by means of the electric arc method. The metal coating should be removed from the coupon area by sanding or sanding. This application of electrically conductive metal allows a low contact resistance between the sample and the measuring instrument. Individual coupons were then cut from the panel.

[0252] A power supply capable of varying the current and voltage (TTi EL302P programmable 30V / 2A power supply, Thurlby Thandar Instruments, Cambridge, UK) was used to determine the resistance. The sample was in contact with two electrodes of the power supply; these electrodes were placed in contact by means of clamps. Care had to be taken to ensure that the electrodes did not come into contact with each other or with any other metal element. A current of 1 A was applied and the resistance was measured by means of two other electrodes connected to a voltmeter / ohmmeter. The test was carried out on each sample to be measured. The conductivity value was then calculated from the resistance value using the dimensions of the sample and the following formula:

[0253] Resistivity (Ohm.m) = Resistance (Ohm) x Surface (m 2 ) / Thickness (m)

[0254] Conductivity (S / m) = 1 / Resistivity

[0255] Part B

[0256] The results of the second series of tests are presented in Table 10 below. Materials 12, 13, 15 and 17 were produced according to the application. The materials obtained are not micro-perforated, except for comparative material 19.

[0257] [Table 10]

[0258]

[0259]

[0260] Manufacture of the reinforced material according to the application

[0261] The second series of tests were carried out on a new production line, in line with the requirements of industrial scale production, with a higher production rate, with the aim of reducing the production line stoppages and wear of the constituent parts thereof and increasing the safety level. This increase in rate increases the overall inertia of the production line, generating a greater number of material friction events at the various points / rolls of the production line and, therefore, notably on the force required to drive the belts. Therefore, the previous combination of the use of a motorized drive of the continuous belts 15a and 15b and the use of a motorized drive of the continuous belts 15a and 15b was introduced. Figure 18The production line described is modified. Belts 15a and 15b are motorized independently of each other by means of rollers 14a and 14c, rollers 14b and 14d remaining free to rotate.

[0262] This increase in productivity highlights the difficulties encountered in the production of unidirectional webs, the use of twisted reinforcing yarns all having the same type of twist, S or Z, minimizing the presence of defects such as gaps between the yarns, overlaps or waviness. Indeed, despite the use of combs or guide rollers, the trajectory of the reinforcing yarns is not perfectly controlled, which leads to the appearance of defects. As set out in the context of the present invention, by using hybrid S / Z unidirectional webs, these risks can be minimized and even avoided.

[0263] Several materials 11 are manufactured in parallel on this industrial-scale production line and therefore with higher productivity.

[0264] As in the first series of tests, several reinforcing materials according to the invention in the form of a tape are manufactured simultaneously.

[0265] Similarly, several materials 12 and 13 according to the invention are manufactured in parallel. It is observed that the materials 12 and 13 obtained are more regular compared to the material 11, especially at the edges. Indeed, in the case of materials 12 and 13, the quality of the alignment of the yarns is better during the formation of the unidirectional web. As a result, the distance between the two unidirectional webs manufactured in succession is more regular, facilitating the cutting of the two laminated face yarns on their two faces between the two formed unidirectional webs.

[0266] The same observations are made for materials 14 and 15 and 16 and 17. In the case of material 14 comprising only S-twisted yarns, more defects are observed than in the case of material 15 using the sequence of SZSZSZ yarns, such as wrinkles, gaps or overlaps between the yarns and irregularities at the edges. Similarly, in the case of material 16 comprising only Z-twisted yarns, more defects are observed than in the case of material 17 using the sequence of SSZZSS yarns, such as wrinkles, gaps or overlaps between the yarns and irregularities at the edges.

[0267] In addition, in the case of material 18 comprising 18 yarns (sequence of 7 S-twisted yarns, 5 Z-twisted yarns then 6 S-twisted yarns), the formation of the unidirectional web by the aforementioned method results in a web as shown in Figure 8, which is not satisfactory. Figure 17The unidirectional net is shown. As can be seen from this figure, there is a clear gap at the junction of 7 S twisted yarns / 5 Z twisted yarns, which constitutes a quality defect, creating a continuous gap greater than 1 mm wide along the entire length of the net. The group of Z twisted yarns is stretched to the right, while the group of S twisted yarns is stretched to the left. This leads to an unsatisfactory continuous gap. This sequence does not correspond to the definition PI, P2, II and I2 given for the hybrid S / Z unidirectional net within the scope of the present invention, which leads to a more balanced unidirectional net in terms of the number of S twisted and Z twisted yarns and a greater coverage due to the reduced risk of inter-yarn gaps.

[0268] Thus, within the scope of the present invention, although using a guide device or comb, a deflection phenomenon of the trajectory of the reinforcing yarns is observed during the formation of a twisted reinforcing yarn having the same twist or having a configuration of a unidirectional net that does not correspond to the definition PI, P2, II and I2 given for the hybrid S / Z unidirectional net within the scope of the present invention. These phenomena do not appear for unidirectional nets comprising only 3 or fewer yarns. The use of the hybrid S / Z unidirectional net proposed within the scope of the present invention solves the problem of unidirectional nets consisting of more than 3 yarns.

[0269] Moreover, the deflection phenomenon is aggravated with the increase in the width of the reinforcing material produced. This problem is even more prominent for productions of greater than 7 mm or 12 mm width. The deflection problem of the reinforcing yarns, which is solved by the hybrid unidirectional S / Z net proposed within the scope of the present invention, appears regardless of the polymer porous layer used and also regardless of the manufacturing method, i.e. whether multiple reinforcing materials are manufactured in parallel or not. Indeed, the deflection phenomenon, if it occurs, also causes difficulties during the application of the material according to the present invention, leading to unsatisfactory positioning.

[0270] Automated lay-up of the reinforced material according to the application

[0271] The materials 11 to 17 are laid by means of an automatic laying device comprising a guide made of a guide groove in which the material circulates before being applied to the laying surface. This guide makes it possible to ensure that the net is positioned correctly at the outlet of the laying head of the device, which will then enable the laying head to control the trajectory of the reinforcing material and its positioning on the laying surface correctly. As Figure 16 To evaluate the materials, laying is carried out by applying one after the other on a flat surface in order to obtain a series of joint layings of parallel strips 11 of material (SSSS). The same procedure is followed with the material 12 (SZZS) and the material 13 (SZSZ). With these two materials, the laying is better controlled, which leads to a reduction in the gaps and undulations on the laying surface, as in Figure 16The same findings were observed for materials 14 and 15 first and for materials 16 and 17 second. The lay-up was not as satisfactory in the case of material 14, which contained only S-twist yarns, compared to the use of material 15, which used a sequence of SZSZSZ yarns. Similarly, more gaps were observed in the case of material 16, which contained only Z-twist yarns, compared to the case of material 17, which used a sequence of SSZZSS yarns. Table 11 shows the average gap width obtained between the two bands, measured with a ruler, in the case of lay-up of materials 16 and 17.

[0272] The same findings were observed for materials 14 and 15 first and for materials 16 and 17 second. The lay-up was not as satisfactory in the case of material 14, which contained only S-twist yarns, compared to the use of material 15, which used a sequence of SZSZSZ yarns. Similarly, more gaps were observed in the case of material 16, which contained only Z-twist yarns, compared to the case of material 17, which used a sequence of SSZZSS yarns. Table 11 shows the average gap width obtained between the two bands, measured with a ruler, in the case of lay-up of materials 16 and 17.

[0273] [Table 11]

[0274] Material 17 (SSZZSS) 16 (ZZZZZZ) Number of strips applied 8 8 Average gap (mm) 0.1 mm 1.5 mm

[0275] It is clear that the use of a SSZZSS net, composed of both S-twist and Z-twist twist yarns, results in a significant reduction of the areas of the resulting unidirectional net in which there are no reinforcing yarns.

[0276] Performance of the material according to the application

[0277] The performance of the materials according to the application was evaluated according to the method described in section A.

[0278] The advantages in terms of reduction of the ratio of vacuum thickness to non-vacuum thickness, reduction of overruns, increase in the transverse permeability of the material and increase in the transverse electrical conductivity of the material, using the twist yarns proposed in the application, are preserved regardless of whether the unidirectional net is composed only of twist S-twist or Z-twist yarns or whether the unidirectional net is composed of both S-twist and Z-twist twist yarns.

[0279] In contrast, the mechanical performance of the materials with unidirectional nets composed of both S-twist and Z-twist twist yarns, as proposed within the scope of the application, is very satisfactory, since the defects in the resulting reinforcing material are reduced.

[0280] The results obtained are presented in the following table 12:

[0281] [Table 12]

[0282]

[0283] The out-of-plane performance of the unidirectional net consisting of both S-twisted and Z-twisted yarns is improved compared to the comparative micro-perforated material 19. Therefore, the out-of-plane performance is improved whether the material has a unidirectional net consisting of a sequence of yarns twisted along the same direction or a unidirectional net consisting of a mixture of S-twisted and Z-twisted yarns. The results obtained are presented in the following table 13.

[0284] [table 13]

[0285]

[0286] The transverse permeability performance of the material 15 according to the application was also measured and compared with the comparative material 19 and is presented in the following table 14. The transverse permeability obtained for both materials is comparable.

[0287] [table 14]

[0288]

[0289] The transverse conductivity performance of the material 15 according to the application was also measured and is presented in the following table 15:

[0290] [table 15]

[0291] Material Material 15 of the application Transverse electrical conductivity (S / m) 12.3

[0292] The material 15 according to the application provides good electrical properties, especially compared to those obtained with the comparative material 1.

Claims

1. A reinforcing material comprising a unidirectional reinforcing web (2) formed by a series of at least three twisted carbon reinforcing yarns (3), the unidirectional reinforcing web having a porous polymer layer (4, 5) bonded to at least one surface thereof, the polymer portion of the reinforcing material comprising 0.5% to 10% of its total weight, characterized in that, The carbon-reinforced yarn (3) is individually twisted with a twist of 3 to 15 twists per meter, and comprises at least one carbon-reinforced yarn (3) with an S-twist and at least one carbon-reinforced yarn (3) with a Z-twist, wherein: - When the total number of twisted carbon reinforcing yarns (3) forming the unidirectional reinforcing net (2) is even, the number of twisted carbon reinforcing S-twist yarns (3) on one side of the plane Δ and the number of twisted carbon reinforcing S-twist yarns (3) on the other side of the plane Δ are each independently an integer within the range {[(total number of yarns) / 4]-35%; [(total number of yarns) / 4]+35%}, if the definition formula cannot be an integer, then each endpoint of the range is rounded to the nearest integer, and the other twisted carbon reinforcing yarns (3) are Z-twist yarns; - When the total number of twisted carbon reinforcing yarns (3) forming the unidirectional reinforcing net (2) is odd, the number of twisted carbon reinforcing S-twist yarns (3) on one side of plane Δ and the number of twisted carbon reinforcing S-twist yarns (3) on the other side of plane Δ are two integers or two half-integers and are each independently within the range {[(total number of yarns) / 4]-35%; [(total number of yarns) / 4]+35%}. If the definition formula does not exceed an integer or an integer plus half, then each endpoint of the range is rounded to the nearest integer or an integer plus half. Other twisted carbon reinforcing yarns (3) are Z-twist yarns. The plane Δ is a plane parallel to the overall extension direction of the unidirectional reinforcing mesh (2) and divides the unidirectional reinforcing mesh (2) into two equal parts perpendicular to its surface.

2. The reinforcing material (1) according to claim 1, characterized in that, The unidirectional reinforcing mesh (2) has porous polymer layers (4, 5) bonded to each of its faces.

3. The reinforcing material (1) according to claim 1, characterized in that, The polymer portion of the reinforcing material accounts for 2% to 6% of its total weight.

4. The reinforcing material (1) according to claim 1, characterized in that, The carbon-reinforced yarn (3) has a twist of 6 to 12 twists per meter.

5. The reinforcing material (1) according to claim 1, characterized in that, The unidirectional reinforcing mesh (2) is formed by a sequence of twisted carbon-reinforced S-twist yarns (3) and twisted carbon-reinforced Z-twist yarns (3), having one of the configurations (SZ)i, S(ZS)j or Z(SZ)j, wherein i and j are integers in the range of 2 to 20, or the same number of S-twist yarns on both sides of the plane Δ are equal, or the unidirectional reinforcing mesh is symmetrical with respect to the plane Δ.

6. The reinforcing material (1) according to claim 5, characterized in that, i and j are integers in the range of 2 to 10.

7. The reinforcing material (1) according to any one of claims 1 to 6, characterized in that, The reinforcing material has a width greater than 7 mm and a length from 2 m to 5000 m.

8. The reinforcing material (1) according to claim 7, characterized in that, The reinforcing material has a width greater than 12 mm.

9. The reinforcing material (1) according to claim 7, characterized in that, The reinforcing material has a width ranging from 12 mm to 51 mm.

10. The reinforcing material (1) according to claim 7, characterized in that, The reinforcing material has a length of 100m to 2000m.

11. The reinforcing material according to any one of claims 1 to 6, characterized in that, The one or more porous polymer layers present are porous membranes, loose fabrics, powder coatings, liquid polymer coatings, woven fabrics, or veils.

12. The reinforcing material (1) according to claim 11, characterized in that, The one or more porous polymer layers present are nonwoven materials.

13. The reinforcing material according to any one of claims 1 to 6, characterized in that, The unidirectional reinforcing mesh (2) has a strength of 126 g / m 2 Up to 1000g / m 2 The weight within the range.

14. The reinforcing material according to any one of claims 1 to 6, characterized in that, The unidirectional reinforcing mesh (2) has a strength of 126 g / m 2 Up to 280g / m 2 The weight within the range.

15. The reinforcing material according to any one of claims 1 to 6, characterized in that, The unidirectional reinforcing mesh (2) has a strength of 126 g / m 2 Up to 210g / m 2 The weight within the range.

16. The reinforcing material (1) according to any one of claims 1 to 6, characterized in that, The unidirectional reinforcing mesh (2) is formed from twisted carbon-reinforced yarns (3) with a fineness of 3K to 24K.

17. The reinforcing material (1) according to any one of claims 1 to 6, characterized in that, The unidirectional reinforcing mesh (2) is formed from twisted carbon-reinforced yarns (3) with a fineness of 6K to 12K.

18. The reinforcing material according to any one of claims 1 to 6, characterized in that, The present one or more porous polymer layers (4, 5) have thermoplastic properties and are composed of thermoplastic polymers, partially cross-linked thermoplastic polymers, mixtures of such polymers, or mixtures of thermoplastic polymers and thermosetting polymers.

19. The reinforcing material according to any one of claims 1 to 6, characterized in that, The one or more porous polymer layers (4, 5) have a heat-melting property, and the bonding of the one or more porous polymer layers with the unidirectional reinforcing mesh is achieved through this heat-melting property.

20. The reinforcing material according to any one of claims 1 to 6, characterized in that, One or more porous polymer layers (4, 5) are nonwoven materials, and when two porous polymer layers are present, they are the same nonwoven material.

21. The reinforcing material according to claim 20, characterized in that, The one or more nonwoven materials have a content of 0.2 g / m 2 Up to 20g / m 2 Basis weight and / or thickness from 0.5 micrometers to 50 micrometers.

22. The reinforcing material according to claim 20, characterized in that, The one or more nonwoven materials have a content of 0.2 g / m 2 Up to 20g / m 2 Basis weight and / or thickness from 3 micrometers to 35 micrometers within the range.

23. The reinforcing material according to any one of claims 1 to 6, characterized in that, The reinforcing material is neither perforated, nor sewn, nor knitted, nor woven.

24. A method for preparing the reinforcing material according to any one of claims 1 to 23, characterized in that, The method comprises the following sequential steps: a1) Provides a unidirectional reinforcing web (2) formed by a series of at least three individually twisted carbon-reinforced yarns (3), the individually twisted carbon-reinforced yarns having a twist of 3 twists / meter to 15 twists / meter and comprising at least one carbon-reinforced S-twist yarn (3) and at least one carbon-reinforced Z-twist yarn (3), wherein: - When the total number of twisted carbon reinforcing yarns (3) forming the unidirectional reinforcing net (2) is even, the number of twisted carbon reinforcing yarns (3) on one side of the plane Δ and the number of twisted carbon reinforcing yarns (3) on the other side of the plane Δ are each independently an integer within the range {[(total number of yarns) / 4]-35%; [(total number of yarns) / 4]+35%}, if the definition formula cannot be an integer, then each endpoint of the range is rounded to the nearest integer, and the other twisted carbon reinforcing yarns (3) are Z-twist yarns; - When the total number of twisted carbon reinforcing yarns (3) forming the unidirectional reinforcing net (2) is odd, the number of twisted carbon reinforcing S-twist yarns (3) on one side of plane Δ and the number of twisted carbon reinforcing S-twist yarns (3) on the other side of plane Δ are two integers or two half-integers and are each independently within the range {[(total number of yarns) / 4]-35%; [(total number of yarns) / 4]+35%}. If the definition formula does not exceed an integer or an integer plus half, then each endpoint of the range is rounded to the nearest integer or an integer plus half. Other twisted carbon reinforcing yarns (3) are Z-twist yarns. The plane Δ is a plane parallel to the overall extension direction of the unidirectional reinforcing mesh (2) and divides the unidirectional reinforcing mesh (2) into two equal parts perpendicular to its surface; a2) Provide one or two porous polymer layers (4, 5); a3) Combine the porous polymer layer (4 or 5) with one face of the unidirectional reinforcing mesh (2), and in the case of two porous polymer layers (4, 5), combine each of them with each face of the unidirectional reinforcing mesh (2).

25. The method according to claim 24, characterized in that, The individually twisted carbon-reinforced yarn (3) has a twist of 6 twists / meter to 12 twists / meter.

26. The method according to claim 24 or 25, characterized in that, The method includes, upstream of step a1), the step of producing the unidirectional reinforcing web (2), which includes applying a twist of 3 to 15 twists per meter to one or a series of carbon reinforcing yarns (3) with an S twist, the twist being applied individually to each carbon reinforcing yarn, and applying a twist of 3 to 15 twists per meter to one or a series of carbon reinforcing yarns (3) with a Z twist, the twist being applied individually to each carbon reinforcing yarn.

27. The method according to claim 24 or 25, characterized in that, The method includes the following upstream of step a1): i) Apply a twist of 3 twists / meter to 15 twists / meter to a carbon-reinforced yarn with S twist or a series of carbon-reinforced yarns with S twist (3), the twist being applied individually to each carbon-reinforced yarn; and apply a twist of 3 twists / meter to 15 twists / meter to a carbon-reinforced yarn with Z twist or a series of carbon-reinforced yarns with Z twist (3), the twist being applied individually to each carbon-reinforced yarn. ii) Align the resulting twisted reinforcing yarns and arrange them continuously to form a unidirectional reinforcing web comprising at least one carbon-reinforced S-twist yarn (3) and at least one carbon-reinforced Z-twist yarn (3), wherein: - When the total number of twisted carbon reinforcing yarns (3) forming the unidirectional reinforcing net (2) is even, the number of twisted carbon reinforcing S-twist yarns (3) on one side of the plane Δ and the number of twisted carbon reinforcing S-twist yarns (3) on the other side of the plane Δ are each independently an integer within the range {[(total number of yarns) / 4]-35%; [(total number of yarns) / 4]+35%}, if the definition formula cannot be an integer, then each endpoint of the range is rounded to the nearest integer, and the other twisted carbon reinforcing yarns (3) are Z-twist yarns; - When the total number of twisted carbon reinforcing yarns (3) forming the unidirectional reinforcing net (2) is odd, the number of twisted carbon reinforcing S-twist yarns (3) on one side of plane Δ and the number of twisted carbon reinforcing S-twist yarns (3) on the other side of plane Δ are two integers or two half-integers and are each independently within the range {[(total number of yarns) / 4]-35%; [(total number of yarns) / 4]+35%}. If the definition formula does not exceed an integer or an integer plus half, then each endpoint of the range is rounded to the nearest integer or an integer plus half. Other twisted carbon reinforcing yarns (3) are Z-twist yarns. The plane Δ is a plane parallel to the overall extension direction of the reinforcing yarn (3) of the unidirectional reinforcing net (2) and divides the unidirectional reinforcing net (2) into two equal parts perpendicular to its surface.

28. The method according to claim 24 or 25, characterized in that, The one or more porous polymer layers (4, 5) have thermomeltable properties, and the combination in step a3) is achieved by applying one or more of the porous polymer layers to one or each face of the unidirectional reinforcing mesh (2), the application of the one or more of the porous polymer layers being accompanied by or followed by heating the polymer fibers to soften or melt them, and then cooling them.

29. A preform consisting at least in part of one or more reinforcing materials according to any one of claims 1 to 23.

30. A method for manufacturing composite material parts from at least one reinforcing material according to any one of claims 1 to 23, characterized in that, Thermosetting resin, thermoplastic resin, or a mixture of thermosetting and thermoplastic resins are injected or infused into the reinforcing material, a stack of multiple reinforcing materials according to any one of claims 1 to 23, or a preform according to claim 29.

31. A method for manufacturing a composite material part according to claim 30, characterized in that, The method includes the following steps prior to infusing or injecting the resin: forming a sheet or stack comprising a plurality of reinforcing materials (1) according to any one of claims 1 to 23, during which the reinforcing materials (1) are continuously conveyed within a guide member and circulated, thereby ensuring their positioning during their layup to produce the desired sheet or stack.

32. The method for manufacturing composite material parts according to claim 30 or 31, characterized in that, The method includes laying or molding before pouring or injecting the resin.

33. The method for manufacturing composite material parts according to claim 32, characterized in that, The layup or molding utilizes the hot-melt properties of porous polymer layers present in the one or more reinforcing materials.

34. The method for manufacturing composite material parts according to claim 30 or 31, characterized in that, Inject or pour thermosetting resin.

35. The method for manufacturing composite material parts according to claim 30 or 31, characterized in that, Inject or pour epoxy resin.

36. Use of one or more reinforcing materials according to any one of claims 1 to 23 for manufacturing preforms or composite parts in combination with thermosetting resins, thermoplastic resins, or mixtures of thermosetting and thermoplastic resins.

37. The use according to claim 36, characterized in that, Inject or pour thermosetting resin.

38. The use according to claim 36, characterized in that, Inject or pour epoxy resin.

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