Reinforcement materials containing carbon twisted yarns for forming composite parts, methods and uses thereof

Abstract

The present invention relates to a reinforcing material (1) consisting of a unidirectional reinforcing web (2) formed from one or more carbon reinforcing threads (3) and bonded on each side to a veil of polymer fibers (4, 5) selected from among nonwoven materials, the polymer portion of the reinforcing material representing 0.5% to 10% of the total weight of the reinforcing material (1), preferably 2% to 6% of the total weight, the unidirectional reinforcing web (2) comprising one or a series of individually twisted reinforcing threads (3) having a twist of 3 turns / m to 15 turns / m, preferably 6 turns / m to 12 turns / m.

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 a material suitable for manufacturing composite parts in combination with an injected or infused resin, the material comprising a unidirectional web at least partially made using one or more individually twisted reinforcing yarns and having a twist suitable for ensuring the diffusion of the resin injected or infused during the manufacture of the composite part.

Background Art

[0002] The manufacture of composite parts or composites, i.e., firstly, one or more fiber reinforcements of the unidirectional fiber web type in particular, and secondly, a matrix (which is usually mainly thermosetting and can contain one or more thermoplastic substances), can be manufactured, for example, by so-called direct methods or LCM (Liquid Composite Molding) methods. The direct method is defined by the fact that one or more fiber reinforcements are used in a "dry" state (i.e., without using the final matrix), and the resin or matrix is, for example, by injection into a mold containing the fiber reinforcement (Resin Transfer Molding (RTM) method), by injection through the thickness of the fiber reinforcement (Liquid Resin Injection (LRI) method or Resin Film Infusion (RFI) method), or by manual coating / impregnation of each layer of the fiber reinforcement by a roller or brush continuously applied to the form, manufactured individually. Within the scope of manufacturing composite parts, especially in the aerospace field, high mass production speeds can be achieved. For example, for the manufacture of single-aisle aircraft, aerospace customers desire to be able to manufacture dozens of aircraft per month. Direct methods such as injection or infusion are particularly relevant methods that can meet this requirement.

[0003] In the RTM, LRI, or RFI processes, it is generally necessary to first fabricate a fiber preform or stack in the shape of the desired finished part and then impregnate the preform or stack with resin to form a matrix. The resin is injected or infused by a temperature-pressure differential and then, after all the required amount of resin has been incorporated into the preform, the assembly is brought to a higher temperature and cured by performing a polymerization / crosslinking cycle.

[0004] Composite parts, especially those used in the automotive, aerospace, or shipbuilding industries, are subject to very stringent requirements, particularly with regard to mechanical properties. To save fuel and ease part maintenance, the aerospace industry has replaced many metallic materials with lighter composite materials.

[0005] During part manufacturing, especially by injection or infusion, the resin that will subsequently bond with the fiber reinforcement may be, for example, an epoxy-type thermosetting resin. To enable the resin to flow precisely through a preform made from a stack of various layers of fiber reinforcement, this resin is usually very fluid and has a viscosity of, for example, about 50 mPa·s to 200 mPa·s, or even lower, at the injection / infusion temperature. The main drawback of this type of resin is its brittleness after polymerization / crosslinking, resulting in low impact resistance of the manufactured composite part.

[0006] To solve this problem, prior art documents have proposed a porous thermoplastic polymer veil, in particular a fiber-reinforced layer combined with a thermoplastic nonwoven material (also called a ply), in particular a unidirectional web of reinforcing yarns. Such solutions are described in particular 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 / 061114 and EP 2547816, US 2008 / 0289743, US 2007 / 8361262, US 2011 / 9371604, WO 2011 / 048340. The addition of such a porous thermoplastic layer, in particular a nonwoven-type porous thermoplastic layer, makes it possible to improve the mechanical properties of composite parts obtained in a post-impact compression (CAI) test, a test commonly used to characterize the impact resistance of structures. The use of nonwoven materials makes it possible in particular to obtain mechanical performances suitable for the aerospace field.

[0007] To achieve a sufficient production speed of composite parts, the time for impregnating or injecting resin into a stack or preform of the obtained dry reinforcement material should be made as short as possible when applying the dry reinforcement material.

[0008] Furthermore, in the field of aeronautics, it is necessary to provide materials that meet high-level standards in relation to the stresses associated with the electrical environment of aircraft in flight and on the ground, particularly in the case of lightning.

[0009] For this purpose, the following solutions have been proposed in the prior art. - Increasing the permeability of the dry reinforcement material to the liquid resin to be injected or molded; - Providing a sufficient transverse electrical conductivity.

[0010] The applicant has proposed the micro-perforation of the aforementioned materials, which improves the lateral permeability of the materials (International Publication No. WO 2010 / 046609), improves their lateral cohesion, thus facilitating their processing by automatic application (International Publication No. WO 2014 / 076433), and improves the lateral electrical conductivity of the manufactured composite parts (International Publication No. WO 2013 / 160604).

[0011] Nevertheless, from an industrial perspective, this technology requires special tools to produce the micro-perforations and results in complex application operations for the micro-perforated materials, especially for those with a particularly high basis weight.

[0012] Furthermore, International Publication No. WO 2008 / 155504, which is an application in the name of the applicant, describes a method for manufacturing a composite material in which at least one twisted yarn is applied to an application surface, has a track with at least one curved zone on the application surface, and the reinforcing yarn is bonded to the application surface by a polymer binder. This method is used to manufacture preforms or parts with complex shapes that require the application of yarn to the curved zones, and proposes applying a twist to the yarn upstream of the application, which is selected to at least compensate for the difference in length presented by the farthest paths of the yarn on both sides of the width measured parallel to the application surface.

[0013] International Publication No. WO 2013 / 133437 describes a very special material made from carbon yarns containing 50,000 to 60,000 filaments twisted with a twist of 5 turns / m to 50 turns / m and arranged in the same direction so as not to overlap, and provides a carbon sheet with a basis weight of more than 800 g / m and less than or equal to 26,000 g / m suitable for the RTM process. The proposed material is intended for the design of wind turbine blades, vehicles or boats, but is not suitable for the aerospace field.

[0014] Accordingly, the object of the present invention is to propose an alternative solution to the known prior art adapted to the field of aeronautics, aiming to provide new reinforcing materials for manufacturing composite parts by bonding with the injected or infused resin, and these new reinforcing materials have improved application properties, reduced overrun after application, and improved transverse conductivity while maintaining high transverse permeability. Summary of the Invention

[0015] In this regard, the present invention relates to a reinforcing material comprising a unidirectional reinforcing web formed from one or more carbon reinforcing yarns and bonded to a layer of polymer fibers selected from non-woven materials on each side, wherein the polymer portion of the reinforcing material occupies 0.5% to 10% of its total weight, preferably 2% to 6% of its total weight, and the unidirectional reinforcing web comprises one or a series of individually twisted carbon reinforcing yarns having a twist of 3 turns / m to 15 turns / m, preferably 6 turns / m to 12 turns / m.

[0016] According to some embodiments, the unidirectional reinforcing web is formed from a plurality of carbon reinforcing yarns, and at least every 5th reinforcing yarn, preferably at least every 2nd or 3rd reinforcing yarn, preferably all reinforcing yarns are individually twisted to have a twist of 3 turns / m to 15 turns / m, preferably 6 turns / m to 12 turns / m.

[0017] In particular, the unidirectional reinforcing web has a basis weight in the range of 126 g / m 2 ~280 g / m 2 preferably in the range of 126 g / m 2 ~210 g / m 2 or 210 g / m 2 ~280 g / m 2 and has a basis weight within this range.

[0018] Within the scope of the present invention, the layer of polymer fibers is essentially thermoplastic, and in particular, it 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 thermosetting polymer.

[0019] The polymer fiber layer has a hot tack. Also, the bonding with the unidirectional reinforcing web is achieved by this hot tack.

[0020] The layer of polymer fibers is advantageously made of the same nonwoven material.

[0021] Typically, the nonwoven material has a basis weight in the range of 0.2 g / m 2 ~20 g / m 2 and / or a thickness in the range of 0.5 microns to 50 microns, preferably 3 microns to 35 microns.

[0022] Advantageously, the reinforcing material according to the invention is characterized by not being perforated, sewn, knitted or woven.

[0023] Within the scope of the present invention, by using carbon reinforcing yarns that have been pre-twisted so as to have a series of reinforcing yarns with a twist of 3 t / m to 15 t / m within the reinforcing material according to the invention, the following becomes possible. - Obtaining a bond between the upper and lower surfaces of the unidirectional web and increasing the lateral cohesion; - Creating a diffusion continuity of the resin that is injected or poured during the manufacture of the composite part between the two faces of the unidirectional web by means of the twisted reinforcing yarns. The continuity of the filaments of the twisted reinforcing yarns that join the two faces of the unidirectional web contributes to the lateral permeability. Furthermore, the twisted reinforcing yarns can create channels that extend along the filaments of the twisted reinforcing yarns that join the two faces of the unidirectional web. Thus, lateral permeability is obtained by a number of permeabilities that extend at the level of the twisted reinforcing yarns following the filaments that extend from one face of the unidirectional sheet to the other. - Creating an electrical conductivity continuity along the filaments of the twisted reinforcing yarns that join the two faces of the unidirectional sheet by means of the carbon reinforcing yarns that are conductors.

[0024] The present invention relates to a reinforcing material for the manufacture of composite parts by a direct method. That is, in order to manufacture a composite part, the reinforcing material according to the present invention should be combined with a polymer resin that is injected or poured into the reinforcing material or within a stack of the reinforcing material. Further, conventionally, the weight of the polymer portion of the reinforcing material according to the present invention accounts for a maximum of 10% of the total weight of the reinforcing material according to the present invention. Typically, the polymer portion of the reinforcing material accounts for 0.5% to 10%, preferably 2% to 6% of the total weight of the reinforcing material. This polymer portion corresponds to all parts of the polymer(s) present in the reinforcing material according to the present invention, and thus includes or consists of a non-woven material present in the reinforcing material according to the present invention. The advantage of the present invention is obtained without the need to increase the amount of the polymer material in the polymer portion of the material, that is, the layer of polymer fibers formed from the non-woven material present on both sides of the unidirectional web.

[0025] Except for the use of twisted reinforcing yarns, the polymer fiber layer of the reinforcing material corresponds to that described in the prior art, particularly in WO 2010 / 046609, prior to the micro-perforation process.

[0026] When a unidirectional reinforcing web is formed from an assembly of carbon reinforcing yarns, the carbon reinforcing yarns are arranged side by side. The twisted reinforcing yarns may be arranged adjacent to each other, or untwisted reinforcing yarn or a plurality of untwisted reinforcing yarns may be interposed between two consecutive twisted reinforcing yarns. After the unidirectional web is formed, it can be combined with a layer of polymer fibers selected from among non-woven materials, particularly by laminating on each side.

[0027] According to an alternative embodiment using a unidirectional reinforcing web called a hybrid S / Z, the reinforcing material is characterized in that all carbon reinforcing yarns forming the unidirectional reinforcing web are individually twisted to have a twist of 3 turns / m to 15 turns / m, preferably 6 turns / m to 12 turns / m, and the fact that the unidirectional reinforcing web includes at least three carbon reinforcing yarns twisted with at least one twisted carbon reinforcing S-twist yarn and at least one twisted carbon reinforcing Z-twist yarn. - When the total number of twisted carbon reinforcement yarns forming the unidirectional reinforcement web (referred to as the total number of yarns) is even, the number of twisted carbon reinforcement S-twisted yarns on one side of the plane Δ and the number of twisted carbon reinforcement S-twisted yarns on the other side of the plane Δ are each independently integers within the range {[(total number of yarns) / 4] - 35%; [(total number of yarns) / 4] + 35%}, and each end point of the range is rounded to the nearest integer (rounded off) so that the formula defining this range becomes an integer, and the other twisted carbon reinforcement yarns are Z-twisted yarns; - When the total number of twisted carbon reinforcement yarns forming the unidirectional reinforcement yarn (referred to as the total number of yarns) is odd, the number of twisted carbon reinforcement S-twisted yarns on one side of the plane Δ and the number of twisted carbon reinforcement S-twisted yarns on the other side of the plane Δ are either two integers or the integer plus 0.5, each independently within this range {[(total number of yarns) / 4] - 35%; [(total number of yarns) / 4] + 35%}, and each end point of the range is rounded to the nearest integer or the integer plus 0.5 so that the formula defining this range becomes an integer or the integer plus 0.5, and the remaining carbon reinforcement twisted yarns are Z-twisted yarns; The plane Δ is a plane parallel to the overall extending direction of the unidirectional web and bisects the unidirectional web perpendicularly to its surface.

[0028] In other words, the number of twisted carbon reinforcement yarns forming the unidirectional reinforcement web (referred to as the "total number of yarns" in the definition of the range of the so-called mixed S / Z web in one direction for simplicity) is equal on both sides of the plane Δ, and this plane is at the intermediate fiber level of the unidirectional reinforcement web. Therefore, if the unidirectional reinforcement web consists of n twisted carbon reinforcement yarns (n is an integer greater than 3 in the case of a unidirectional reinforcement web called mixed S / Z), there are n / 2 twisted carbon reinforcement yarns on both sides of the plane Δ.

[0029] Furthermore, the hybrid S / Z unidirectionally reinforced web includes twisted carbon reinforced S-twisted yarns of an integer m, and the sum of the number m1 of the twisted carbon reinforced S-twisted yarns on one side of the plane Δ and the number m2 of the twisted carbon reinforced S-twisted yarns on the other side of the plane Δ is an integer. Similarly, the unidirectionally reinforced web includes twisted carbon reinforced Z-twisted yarns of an integer p, and the sum of the number p1 of the twisted carbon reinforced Z-twisted yarns on one side of the plane Δ and the number p2 of the twisted carbon reinforced Z-twisted yarns Z on the other side of the plane Δ is an integer. Therefore, for example, in the case of a unidirectionally reinforced web formed of a series of twisted carbon reinforced SZSZSZS yarns (twist of juxtaposed yarns) satisfying Definition I1, the number n / 2 of the yarns on either side of the plane Δ is 3.5, m1 = m2 = 2, and p1 = p2 = 1.5.

[0030] In particular, the material according to the present invention including a unidirectionally reinforced web called a hybrid S / Z web has the advantage that they can be manufactured at high speed over a large length. In this embodiment of the unidirectional, so-called hybrid S / Z reinforced web, the material according to the present invention advantageously has a width greater than 7 mm, preferably greater than 12 mm, preferably in the range of 12 mm to 51 mm, and a length preferably of 2 m to 5000 m, preferably 100 m to 2000 m.

[0031] According to another aspect, the present invention relates to a method for preparing a reinforced material including the following continuous steps: a1) providing a unidirectionally reinforced web formed from one or more reinforcing yarns individually twisted and having a twist of 3 turns / m to 15 turns / m; a2) providing at least two polymer fiber layers selected from among non-woven materials; a3) bonding each layer of the polymer fibers to each face of the unidirectionally reinforced web. The method includes the steps above.

[0032] For example, the preparation method includes a step of producing a unidirectionally reinforced web including adding a twist of 3 turns / m to 15 turns / m to the reinforcing yarn or a series of yarns upstream of step a1), and the twist is added to each yarn individually.

[0033] According to one embodiment, the unidirectional reinforcing web is formed from a plurality of reinforcing yarns, and the preparation method includes, upstream of step a1), i) a step of applying a twist of 3 turns / m to 15 turns / m to a series of reinforcing yarns, the twist being applied individually to each yarn; ii) a step of aligning the thus obtained twisted yarns, optionally together with other reinforcing yarns, and juxtaposing the yarns so as to form a unidirectional reinforcing web. It includes.

[0034] In such a method, the layer of polymer fibers has hot tack properties, and it is advantageous that the bonding in step a3) is obtained by applying each layer of polymer fibers to each side of the unidirectional reinforcing web, the application being accompanied by or subsequent to heating of the polymer fibers to soften or melt the polymer fibers and then cooling.

[0035] The present invention also has, as its object, a preform that is at least partially composed of one or more reinforcing materials according to the present invention.

[0036] Another object of the present invention relates to a method for manufacturing a composite part from at least one reinforcing material according to the present invention. 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 poured into the reinforcing material, a stack of several reinforcing materials according to the present invention, or a preform according to the present invention.

[0037] In particular, such a method includes a step of forming a ply or stack including several reinforcing materials according to the present invention before the injection or pouring of the resin, during which the reinforcing materials are continuously conveyed and circulated within a guide member to ensure their positioning during their application to reach the desired ply or stack. Conventionally, the materials according to the present invention are cut to the desired dimensions, particularly the desired length, to form the folds or stacks to be manufactured.

[0038] This method for manufacturing a composite part advantageously includes an application or molding that utilizes the hot tack properties of the polymer fiber layer present in the reinforcing material(s), preferably before the injection or casting of the resin.

[0039] Another object of the present invention relates to the use of one or more reinforcing materials according to the present invention for the manufacture of preforms or composite parts bonded to a thermosetting or thermoplastic resin or a mixture of a thermosetting resin and a thermoplastic resin.

[0040] For implementing the manufacturing method or use of the reinforcing material according to the present invention, it is advantageous for a thermosetting resin, in particular an epoxy resin, to be injected or cast.

[0041] The present invention will be better understood from the following detailed description with reference to the accompanying drawings.

Brief Description of the Drawings

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[0063] Explanation of the implementation method The object of the present invention relates to a reinforcing material 1 composed of a unidirectional reinforcing web 2 formed from one or more carbon reinforcing yarns 3 bonded to veils corresponding to the layers 4, 5 of polymer fibers forming a non-woven fabric material on each side of the unidirectional reinforcing web 2, as shown in Figure 1A. More precisely, at least a part of the carbon reinforcing yarns 3 are individually twisted, as described in detail in the following explanation.

[0064] "Unidirectional reinforcing web" means a web composed exclusively or almost exclusively of carbon reinforcing yarns arranged parallel to each other.

[0065] Figure 1B shows a unidirectional web 2 composed of several individually twisted carbon reinforcing yarns 3 bonded to veils 4, 5 on each side of the unidirectional web 2. Each twisted reinforcing yarn 3 has an overall extension direction D G (corresponding to the central axis of the yarn) that is straight in the extension plane of the unidirectional sheet. Each twisted reinforcing yarn 3 extends linearly parallel to the extension planes S4 and S5 of the veils 4, 5, which are planar in Figure 1B, in the overall extension direction D G having. In a unidirectional web, the overall extension directions D G of all the reinforcing yarns are all parallel to each other or substantially parallel to each other. The specific overall extension directions D of two reinforcing yarns of 3° or less, preferably 2° or less, preferably 1° or less GIt is generally recognized by those skilled in the art that the deflection between does not change the unidirectional properties of the web. The overall extension direction of the unidirectional web corresponds to the overall extension direction D of the reinforcing yarns when they are all parallel to each other, or, in the rare case where there is no exact parallelism between all the extension directions D of the reinforcing yarns 3 forming the unidirectional web 2, it corresponds to the average of these overall extension directions. G In a unidirectional web, the reinforcing yarns are arranged side by side to ensure an optimal coverage rate of the surface. 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). G In particular, polyamide, copolyamide, polyester, copolyester, ester / ether block copolyamide, polyacetal, polyolefin, thermoplastic polyurethane, or phenoxy-type thermoplastic joining yarns are provided, which can facilitate the handling of the web before bonding to the polymer fiber bundle as required. These joining yarns usually extend transversely to the carbon yarns. The term "unidirectional web" also includes unidirectional fabrics, and the spaced weft yarns are woven together with the carbon yarns that extend parallel to each other to form the warp yarns of the unidirectional fabric. Even in these different cases where such joining, stitching, or weft yarns are present, the carbon yarns parallel to each other account for at least 95% of the weight of the web and are thus classified as "unidirectional". Nevertheless, according to a particular embodiment of the invention, the unidirectional web does not include any weft yarns that weave the carbon yarns so as to avoid any undulations. In particular, the reinforcing material according to the invention does not include perforations, weaving, sewing, or knitting. In a unidirectional web, the carbon reinforcing yarns are preferably not bonded to a polymer binder and are thus classified as dry, i.e., they are not impregnated, coated, or bonded to any polymer binder before bonding to the polymer fiber bundles 4, 5. However, the carbon reinforcing yarns are usually characterized by a standard sizing rate of up to 2% of their weight.

[0066] In a unidirectional web, the reinforcing yarns are arranged side by side to ensure an optimal coverage rate of the surface. 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).

[0067] In particular, polyamide, copolyamide, polyester, copolyester, ester / ether block copolyamide, polyacetal, polyolefin, thermoplastic polyurethane, or phenoxy-type thermoplastic joining yarns are provided, which can facilitate the handling of the web before bonding to the polymer fiber bundle as required. These joining yarns usually extend transversely to the carbon yarns. The term "unidirectional web" also includes unidirectional fabrics, and the spaced weft yarns are woven together with the carbon yarns that extend parallel to each other to form the warp yarns of the unidirectional fabric. Even in these different cases where such joining, stitching, or weft yarns are present, the carbon yarns parallel to each other account for at least 95% of the weight of the web and are thus classified as "unidirectional". Nevertheless, according to a particular embodiment of the invention, the unidirectional web does not include any weft yarns that weave the carbon yarns so as to avoid any undulations. In particular, the reinforcing material according to the invention does not include perforations, weaving, sewing, or knitting. In a unidirectional web, the carbon reinforcing yarns are preferably not bonded to a polymer binder and are thus classified as dry, i.e., they are not impregnated, coated, or bonded to any polymer binder before bonding to the polymer fiber bundles 4, 5. However, the carbon reinforcing yarns are usually characterized by a standard sizing rate of up to 2% of their weight.

[0068] Carbon reinforcing yarns (which may more simply be referred to within the scope of the present invention as reinforcing yarns or carbon yarns) are generally composed of an assembly of fibers or filaments and generally contain from 1,000 to 320,000 filaments, preferably from 12,000 to 24,000 filaments. The reinforcing yarns used within the scope of the present invention are made of carbon. In a particularly preferred embodiment, within the scope of the present invention, 1K to 24K carbon yarns are used. The constituent fibers are preferably continuous. The 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 a slack yarn that does not come into contact with physical elements, generally, a carbon flat yarn having a titer of 200 tex has a width of 1 mm to 3 mm, a 12K carbon flat yarn having a titer of 446 tex has a width of 2 mm to 5 mm, a 12K carbon flat yarn having a titer of 800 tex has a width of 3 mm to 7 mm, a 24K carbon flat yarn having a titer of 1600 tex has a width of 5 mm to 12 mm, and a 24K carbon flat yarn having a titer of 1040 tex has a width of 5 mm to 10 mm. Thus, carbon flat yarns with 3,000 to 24,000 filaments generally have a width of 1 mm to 12 mm. Among carbon yarns, there are high-resistance (HR) yarns having a tensile modulus of 220 GPa to 241 GPa and a yield strength of 3450 MPa to 4830 MPa, intermediate modulus (IM) yarns having a tensile modulus of 290 GPa to 297 GPa and a yield strength of 3450 MPa to 6200 MPa, and high-modulus (HM) yarns having a tensile modulus of 345 GPa to 448 GPa and a yield strength of 3450 to 5520 Pa (in accordance with "ASM Handbook", ISBN 0-87170-703-9, ASM International 2001). In particular, within the scope of the present invention, the unidirectional reinforcing web 2 may be formed from one or more carbon reinforcing yarns 3 having a titer of 3K to 24K, preferably 6K to 12K.

[0069] According to the present invention, the unidirectional reinforcing web 2 includes one or a series of carbon reinforcing yarns 3 that are individually twisted and have a twist of 3 turns / m to 15 turns / m, preferably 6 turns / m to 12 turns / m. According to the present invention, the twisted carbon reinforcing yarn 3, that is, the relative rotation of the outer edge of the yarn around its intermediate fiber (corresponding to the central axis of the yarn) is used, whereby they follow a helical path, that is, the tangent at each point forms a substantially constant angle with a given direction. As shown in FIG. 2, the twisted carbon reinforcing yarn 3 has, in its core, an intermediate fiber having an overall direction corresponding to the longitudinal direction X (also referred to as the overall extension direction D G of the reinforcing yarn 3), while the filaments follow a helical path around this overall direction. FIG. 2 schematically shows the helical shape of the generatrix h of the twist-reinforced yarn 3 having one turn of twist over a linear distance d along the longitudinal direction X (also referred to as the overall extension direction D G ).

[0070] Each carbon reinforcing yarn 3 is individually twisted. Such twisting can be obtained using a twisting machine such as the machine sold under the Kamitsu Seisakusho Ltd. model UT-1000. FIG. 3 is a diagram showing the twisting process implemented by a twisting machine that enables the twist-reinforced yarn 3 according to the present invention to be obtained. A spool 7 around which the reinforcing yarn to be twisted is wound is attached so as to be rotatable about its axis A, and the reinforcing yarn can be rewound via a yarn guide 8 with respect to a spool 9 for winding the twist-reinforced yarn 3. The spool 7 around which the reinforcing yarn is twisted is attached to a support portion 11 that is rotationally driven by a motor 12 along an axis B perpendicular to the axis of the spool 7. The twist of the reinforcing yarn 3 depends on the linear velocity of the rewinding of the reinforcing yarn and the rotational speed of the support portion 11 of the spool 7.

[0071] It should be understood that the twist results in a change in the width of the twist-reinforced yarn.

[0072] The following description explains the influence of the twisting process on the width of the twist-reinforced yarn.

[0073] Figure 4 shows a method for measuring the width of the reinforcing yarn before and after the twisting operation as described above. The reinforcing yarn having the width to be measured is rewound from spool 13 to ensure that it continuously passes over the first fixed cylindrical rod 14, under the second fixed cylindrical rod 15, and over the third fixed cylindrical rod 16 before being wound up by the take-up spool 17. Typically, the tension of the reinforcing yarn coming out of spool 13 is between 150 g and 300 g. The cylindrical rods 14-16 are mounted to enable the measurement of the width of the reinforcing yarn under reproducible predetermined tension conditions. The reinforcing yarn is tensioned as it passes over the first fixed cylindrical rod 14 and the second fixed cylindrical rod 15, then unfurled by the third cylindrical rod 16, and a matrix camera 18 is disposed above it. 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 distance between the first and second cylindrical rods on one side and the center distance between the second and third cylindrical rods on the other side are 50 mm and 20 mm horizontally and 15 mm and 10 mm vertically respectively. The measurement of the width of the reinforcing yarn is performed by camera 18 during the running of the reinforcing yarn at approximately 5 mm intervals over a length of 100 ml (linear meter).

[0074] The measurements are made on carbon fibers manufactured by HEXCEL Corporation of Stamford, Connecticut, USA, having different linear densities, different numbers of filaments, and different twists, as shown in Table 1 below.

[0075]

Table 1

[0076] Figure 5 shows the measurements made on the carbon reinforcing yarns in Table 1. Figure 5 shows the average width of the reinforcing yarn as a function of twist for various reinforcing yarns. Figure 5 clearly shows that the average width of the reinforcing yarn decreases as the twist increases, which is expected as the twist tightens the filaments of the twisted reinforcing yarn.

[0077] When examining Fig. 6 showing the standard deviation of the average width as a function of twist for various reinforcing yarns in Table 1, it is clear that the standard deviation of the width decreases as the twist increases. In other words, the higher the twist, the more uniformly the twisted reinforcing yarn tends to tighten. Therefore, as the twist increases, the reinforcing yarn with a parallelepiped cross-section tends to become a round reinforcing yarn with a low standard deviation. It should be noted that the untwisted reinforcing yarn has a lower standard deviation compared to the twisted reinforcing yarn, and in order to reduce such width variations, it is necessary to achieve a twist of more than 14 turns per meter (tpm).

[0078] It is important to understand that the width distribution of carbon reinforcing yarns affects the possibility of using carbon reinforcing yarns to produce a web with a given basis weight.

[0079] For example, a 210 gram / square meter web requires the juxtaposition of 12K IMA yarns every 2.12 mm so that the web is theoretically completely covered. The calculation is as follows.

[0080] Width [mm] required for a given basis weight = Tenacity [Tex] of the yarn used / Basis weight [g / m 2 . The unit of measurement for the yarn is Tex, which is the gram weight of 1000 m of yarn.

[0081] In practice, it is possible to produce a web of satisfactory quality when the reinforcing yarn has an average width of at least 75% of this so-called "target" width value. A person skilled in the art can determine this target width value by trial and error.

[0082] Table 2 below lists the values of the target width for each basis weight and for each carbon reinforcing yarn used.

[0083]

Table 2

[0084] Figures 7 to 11 are graphs showing the ratio of values exceeding the target width value as a function of the twist of various carbon reinforcing yarns for various basis weights.

[0085] Figure 7 shows, for a web of 140 g / m 2 : - In the case of IMA-12K fibers, the web can be made only from untwisted reinforcing yarns; - In the case of IM7-6K fibers, the web can be made only from reinforcing yarns having a twist of 8 turns or less per meter.

[0086] Figure 8 shows, for a web of 210 g / m 2 : - In the case of IMA-12K fibers, the web can be made from reinforcing yarns having a twist of 8 turns or less per meter; - In the case of IM7-6K fibers, the web can be made from reinforcing yarns having a twist of up to 14 turns per meter.

[0087] Figure 9 shows that for a web of 280 g / m 2 , the height is sufficient to use reinforcing yarns having all twist values within the range of the basis weight.

[0088] Figure 10 shows that for a web of 252 g / m 2 made of AS7-12K fibers, the web can be made from reinforcing yarns having a twist of 6 turns or less per meter.

[0089] Figure 11 shows that for a web of 350 g / m 2 , the height is sufficient to use reinforcing yarns having all twist values within the range of the basis weight.

[0090] Therefore, it seems possible to define the twist limits that can be used for each type of reinforcing yarn for a given basis weight, thereby enabling the selection of not only the yarns to be used but also the applied twist, particularly according to the desired basis weight of the unidirectional web.

[0091] According to another feature of the object of protection of the present invention, the unidirectional reinforcing web 2 is formed from at least one twisted carbon reinforcing yarn 3 having either an S twist, a Z twist, or a mixture of both. The S-twisted and Z-twisted carbon-reinforced yarns 3 have different twisting directions as shown on the right side of FIG. 17. For the definition of what S twist or Z twist means, refer to the book ''Handbook of Weaving'', p16-17 by Sabit Adanur, Professor, Department of Textile Engineering, Auburn, USA, ISBN 1-58716-013-7.

[0092] As shown, the unidirectional reinforcing web 2 can be formed by a reinforcing yarn 3 having a twist of 3 turns / m to 15 turns / m, preferably 6 turns / m to 12 turns / m. In this case, as shown in FIG. 2, a single reinforcing yarn 3 has an intermediate fiber (corresponding to the central axis of the yarn) having an overall direction corresponding to the longitudinal direction X of the reinforcing yarn 3, while the filaments follow a helical path around this overall direction, so the web is classified as unidirectional. According to an alternative embodiment, the unidirectional reinforcing web 2 is formed from a plurality of reinforcing yarns 3, at least some of which have a twist of 3 turns / m to 15 turns / m, preferably 6 turns / m to 12 turns / m, respectively. Each yarn has an extending direction D corresponding to the center line of the yarn GIt has. The twisted reinforcing yarns 3 forming the unidirectional reinforcing web 2 are juxtaposed, and since the extending directions of the twisted reinforcing yarns 3 are parallel to each other, a unidirectional web is constituted. According to the latter embodiment, every at least fifth reinforcing yarn 3, preferably every at least second or third reinforcing yarn 3, preferably all the reinforcing yarns 3 are individually twisted to have a twist of 3 turns / m to 15 turns / m, preferably 6 turns / m to 12 turns / m. According to an advantageous embodiment, it should be understood that all the reinforcing yarns 3 forming the unidirectional reinforcing web 2 are individually twisted to have a twist of 3 turns / m to 15 turns / m, preferably 6 turns / m to 12 turns / m. If the unidirectional reinforcing web 2 does not only contain twisted reinforcing yarns, it is advantageous for the unidirectional reinforcing web 2 to contain the same untwisted reinforcing yarns as the reinforcing yarns used under the twist of the present invention.

[0093] According to an alternative embodiment in which all the reinforcing yarns 3 forming the unidirectional web 2 are twisted, it is also possible to use both one or more twisted reinforcing S-twist yarns 3 and one or more twisted reinforcing Z-twist yarns 3 within the same web. That is, the unidirectional web 2 contains twisted reinforcing yarns 3 having different twist directions, and thus the unidirectional web 2 does not consist only of reinforcing Z-twist yarns 3 or reinforcing S-twist yarns 3, but includes at least one reinforcing Z-twist yarn 3 extending adjacent to one or more reinforcing S-twist yarns 3, or includes at least one reinforcing S-twist yarn 3 extending adjacent to one or more reinforcing Z-twist yarns 3. In contrast, each yarn has the same S-twist or the same Z-twist, and thus has the same twist direction over its entire length, as well as the same twist value.

[0094] These alternative embodiments of the unidirectional reinforcing web 2 are referred to herein as "hybrid S / Z unidirectional webs 2" for the sake of simplicity. In a twisting machine as shown in FIG. 3, obtaining a twist-reinforced yarn 3 with an S twist or a twist-reinforced yarn 3 with a Z twist is affected by the direction of rotation applied to the bobbin 7 about the B axis. By using various types of twist-reinforced yarns 3 within the same unidirectional reinforcing web 2, i.e., at least one with an S twist and at least one with a Z twist, it is possible to limit the risk of defects that appear in the resulting unidirectional reinforcing web 2, in particular the risk of gaps or overlaps between juxtaposed yarns, as well as the risk of undulations. Using two types of twists (S twist and Z twist) within the same unidirectional web tends to even out the local undulations induced by the Z twist and S twist having different directions. By combining these two types of yarns in the same unidirectional web, the production and use of hybrid yarns of S twist and Z twist become easier and tend to result in a more acceptable quality with respect to the gaps and overlaps observed in the produced web, as shown in the following examples.

[0095] Examples of particularly suitable twist-reinforced yarns 3 juxtaposed to form the hybrid S / Z unidirectional web 2 include the following arrangements: SZ, SZS, ZSZ, SZZS, SZSZ, SZSZS, SSZZSS, SZSSZS, SZSZSZ, SSZZSSZZ.

[0096] As shown in FIGS. 1B and 1C, a unidirectional web 2 (or 2a) formed from a plurality of carbon-reinforced yarns 3 is bisected and extends on either side of a plane Δ, which extends perpendicular to the surface of the unidirectional web 2 (thus, when the web is joined to two veils 4, 5, it extends perpendicular to the surfaces S4 and S5 of the two veils 4, 5) and extends parallel to the overall extension direction of the unidirectional web 2. According to a particularly advantageous embodiment of the reinforcing material according to the invention, the unidirectional web 2 (of the hybrid S / Z type) comprises more than 3 individually twisted carbon-reinforced yarns 3 having a twist of 3 turns / m to 15 turns / m, preferably 6 turns / m to 12 turns / m, - when the total number of twisted carbon-reinforced yarns 3 forming the unidirectional web 2 is even: · The number of the twisted carbon fiber reinforced S-twisted yarns 3 on one side of the plane Δ and the number of the twisted carbon fiber reinforced S-twisted 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%}, and each end point of the range is rounded to the nearest integer (rounded off) so that the formula defining it becomes an integer. The other twisted carbon fiber reinforced yarns 3 are Z-twisted yarns (definition P1); · This corresponds to the number of the twisted carbon fiber reinforced Z-twisted yarns 3 on one side of the plane Δ and the number of the twisted carbon fiber reinforced Z-twisted yarns 3 on the other side of the plane Δ, which are each independently an integer within the range {[(total number of yarns) / 4] - 35%; [(total number of yarns) / 4] + 35%}, and each end point of the range is rounded to the nearest integer (rounded off) so that the formula defining it becomes an integer. The other twisted carbon fiber reinforced yarns 3 are S-twisted yarns (definition P2); - When the total number of the twisted carbon fiber reinforced yarns 3 forming the unidirectional web 2 is odd: · The number of the twisted carbon fiber reinforced S-twisted yarns 3 on one side of the plane Δ and the number of the twisted carbon fiber reinforced S-twisted yarns 3 on the other side of the plane Δ are each either two integers or an integer plus 0.5, and each is independently within the range {[(total number of yarns) / 4] - 35%; [(total number of yarns) / 4] + 35%}. Each end point of the range is rounded to the nearest integer or an integer plus 0.5 so that the formula defining it becomes an integer or an integer plus 0.5 (rounded off). The remaining twisted carbon fiber reinforced twisted yarns 3 are Z-twisted yarns (definition I1); · This corresponds to the number of the twisted carbon fiber reinforced Z-twisted yarns 3 on one side of the plane Δ and the number of the twisted carbon fiber reinforced Z-twisted yarns 3 on the other side of the plane Δ, which are each either two integers or an integer plus 0.5, and each is independently within the range {[(total number of yarns) / 4] - 35%; [(total number of yarns) / 4] + 35%}. Each end point of the range is rounded to the nearest integer or an integer plus 0.5 so that the formula defining it becomes an integer or an integer plus 0.5 (rounded off). The remaining twisted carbon fiber reinforced twisted yarns 3 are S-twisted yarns (definition I2). The plane Δ is a plane parallel to the overall extending direction of the one-direction web 2 and bisects the one-direction web perpendicularly to its surface. FIG. 1C illustrates a material of the present invention including a one-direction web 2a formed from a series of twist-reinforced SZSZSZ yarns 3, on which the plane Δ is shown. In Definitions P1, P2, I1 and I2, “each independently, being a range” means that the two related numbers are within the range and may be the same or different.

[0097] As a possible configuration example when the total number of twist-reinforced yarns 3 forming the one-direction web 2 is odd, when the total number of these twist-reinforced yarns 3 is 17 (that is, there are 8.5 yarns on each side of the plane Δ), - According to Definition I1, 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)}. After rounding the endpoints, {3; 5.5} is obtained. Therefore, there may be 3 to 5.5 S-yarns on each side of the plane Δ, or a total of 6 to 11 S-twisted yarns, and the remaining yarns are Z-twisted yarns, or a total of 6 to 11 Z-twisted yarns, and there may be 3 to 5.5 Z-twisted yarns on each side of the plane Δ. - According to Definition I2, the same number of possible S-yarns and Z-yarns are reached on each side of the plane Δ.

[0098] With such a configuration, the number of twisted reinforced S-twisted yarns and Z-twisted yarns 3 in the one-direction reinforced web 2 is more balanced, making the manufacturing easier and obtaining a high-quality one-direction web 2. In fact, in such a case, as described by way of example, during the formation of the one-direction reinforced web 2, the alignment between the twist-reinforced yarns 3 becomes easier, and the gaps, ripples (unevenness) and / or overlaps between the twist-reinforced yarns 3 arranged in parallel are reduced. Further, in parallel, during the automatic manufacturing of some reinforcing materials 1, when cutting the non-woven fabric material at the joint between two reinforcing materials 1 manufactured in parallel as described in WO 2010 / 061114, in this case, a sharper edge and a more homogeneous material are obtained.

[0099] Furthermore, the reinforcing material 1 produced from such a hybrid S / Z web is, as a result, of better quality, and thus so are the composite parts produced. Furthermore, application by means of an automatic application device as described in European Patent No. 2376276 can be carried out more precisely using such a reinforcing material. As explained by way of example, such a reinforcing material 1 remains well centered on a guide or guide member (in particular a groove or comb-shaped one) present at the height of the head or application fingers of the automatic application device, while a reinforcing material 1 made from a unidirectional reinforcing web 2 containing only reinforcing S-twisted yarns 3 or only reinforcing Z-twisted yarns 3, or more generally not fulfilling the defined P1, P2, I1 and I2, is eccentric and tends to abut against the edges of the guide or guide members along which they move.

[0100] In particular, a unidirectional reinforcing web 2 containing an array of reinforcing yarns 3 with completely alternating S-twists and Z-twists is preferred, i.e. those corresponding to the configurations (arrangement of juxtaposed yarns) (SZ)i, S(ZS)j, Z(SZ)j, where i and j are integers, in particular in the range from 1 to 20, preferably in the range from 1 to 10. In particular, i and j are in the range from 2 to 20, preferably in the range from 2 to 10.

[0101] Another particularly satisfactory hybrid S / Z unidirectional web configuration is one having the same number of S-twisted yarns on both sides of the plane Δ and thus, implicitly, also the same number of Z-twisted yarns. The following configurations are some examples: SZZS, SZSZ, SZSZS, SZSSZS.

[0102] Another particularly satisfactory hybrid S / Z unidirectional web configuration is one that is symmetric with respect to the plane Δ. Some examples of these configurations are SZZS, SZSZS, SZSSZS, SZSSZSSZS.

[0103] Thus, the use of hybrid S / Z unidirectional webs, in particular those more precisely described within the scope of the present invention, solves twofold technical problems both during production and during the application of the resulting reinforcing material 1. These materials offer the possibility of being produced and applied, in particular, according to industrial processes.

[0104] The use of a hybrid S / Z unidirectional web, particularly as more precisely described within the scope of the present invention, is particularly suitable for the manufacture of the unidirectional web 2 and thus for the manufacture of the reinforcement 1 having a width in the range of more than 7 mm, preferably more than 12 mm, preferably from 12 mm to 51 mm. Furthermore, the present invention using a hybrid S / Z unidirectional web is also particularly suitable for reinforcements having a length of more than 2 m, particularly from 2 m to 5000 m, preferably from 100 m to 2000 m. Thus, according to such a preferred embodiment within the scope of the present invention, the reinforcement according to the present invention has a width of more than 7 mm and a length of more than 2 m, advantageously a width in the range of 12 mm to 51 mm and a length in the range of 2 m to 5000 m, preferably from 100 m to 2000 m. The width of the material is the average width taken perpendicular to the overall extension direction of the unidirectional sheet, and this width can be measured by performing measurements every 10 cm over the entire length of the material using any suitable means, particularly a camera, and taking the arithmetic mean of the measured values obtained. The length of the material is preferably measured on the plane Δ. In particular, the width of the reinforcement 1 is measured by running it at a constant tension of 200 cN to 400 cN at a constant speed of 1.2 m per minute, at a distance of 265 mm, without support at this point, in front of a camera, for example, Baumer Optronic Type FWX 20, focal length 20 mm, 1624×1236 pixels (Baumer Optronic Gmbh, Germany - the calibration of the camera is as follows: 1 pixel corresponds to 0.05 mm), or in front of another camera more suitable for a wider width of the reinforcement. In particular, there are automatic application devices for applying materials having widths of 6.35 mm, 12.7 mm, 38.1 mm, and 50.8 mm and can be implemented within the scope of the present invention.

[0105] Furthermore, this embodiment of the present invention using a hybrid S / Z unidirectional web is particularly suitable for the manufacture of the reinforcement 1 by continuously bonding a non - woven material to each side of the unidirectional reinforcement web using an electric transport system or device, and for the manufacture by passing the reinforcement during production.

[0106] Advantageously, each of the twisted reinforcing yarns 3 that enter into the formation of the unidirectional reinforcing web 2 has substantially the same twist value over its entire length. It should be noted that all of the twisted reinforcing yarns 3 forming the unidirectional reinforcing web 2 can have the same or different twist values. Preferably, all of the twisted reinforcing yarns 3 forming the unidirectional reinforcing web 2 have the same twist value.

[0107] Within the scope of the present invention, the unidirectional reinforcing web 2 has a basis weight in the range of 126 g / m 2 to 280 g / m 2 , particularly 126 g / m 2 to 210 g / m 2 , preferably 210 g / m 2 to 280 g / m 2 .

[0108] The basis weight of the unidirectional web in the reinforcing material corresponds to the basis weight of the unidirectional web before the unidirectional web is joined to the veil, but it is impossible to measure the weight of the unidirectional web before the unidirectional web is joined to the veils 4, 5 because the reinforcing yarns do not agglomerate between them. The basis weight of the carbon fiber reinforced web can be determined from the basis weight of the reinforcing material 1 (the unidirectional web 2 and the two veils 4, 5). If the basis weight of the veil is known, it is possible to estimate the basis weight of the unidirectional web. Advantageously, the basis weight is determined from the reinforcing material by chemical attack of the veil (optionally also by pyrolysis). This kind of method is classically used by those skilled in the art to determine the carbon fiber content of a fabric or composite structure.

[0109] A method for measuring the basis weight of the reinforcing material 1 will be described below. The basis weight of the reinforcing material is measured by weighing a cut sample of 100 cm 2 (i.e., diameter 113 mm). To facilitate cutting of the sample of the flexible reinforcing material, the reinforcing material is 447 g / m from Cartonnage Roset (Saint Julien en Genevois, France) 2It is placed between two sheets of glossy cardboard with a thickness of 0.450 mm to ensure a certain overall rigidity. The assembly is cut using an air pressure circular die from Novi Profibre (Urbens, France); 10 samples are taken for each type of manufactured reinforced product.

[0110] From the foregoing description, it is clear that it is advantageous for the reinforcing material 1 to consist of a unidirectionally reinforced web 2 bonded to a veil or layer of polymer fibers 4, 5 selected from nonwoven materials on each side of the unidirectionally reinforced web 2. Generally speaking, the method for preparing the reinforcing material 1 according to the present invention comprises the following successive steps: a1) providing a unidirectionally reinforced web formed from one or more individually twisted reinforcing yarns 3 having a twist of 3 turns / m to 15 turns / m; a2) providing at least two layers of polymer fibers 4, 5 selected from nonwoven materials; a3) bonding each layer of polymer fibers to each side of the unidirectionally reinforced web. It includes.

[0111] Generally, the unidirectionally reinforced web 2 of step a1) has a basis weight equal to the desired basis weight of the final reinforcing material 1 and a width equal to the desired width of the final reinforcing material 1.

[0112] The preparation method advantageously includes a step of producing a unidirectionally reinforced web 2 including adding a twist of 3 turns / m to 15 turns / m to the reinforcing yarn or series of reinforcing yarns 3 upstream of step a1), and the twist is added individually to each reinforcing yarn 3.

[0113] According to an alternative embodiment of the preparation method, the unidirectionally reinforced web 2 is formed from a plurality of reinforcing yarns, and the method comprises, upstream of step a1), i) adding a twist of 3 turns / m to 15 turns / m to a series of reinforcing yarns, the twist being added individually to each yarn; ii) aligning the thus obtained twisted yarns, optionally together with other reinforcing yarns, and juxtaposing the yarns to form a unidirectionally reinforced web. It includes.

[0114] In the case of a web consisting only of the twist-reinforced yarn 3, the use of yarns that are not all of the same S-twist or Z-twist type facilitates the alignment and arrangement of the yarns during step ii). Thus, in step ii), advantageously, the selection of the aligned yarns is made so as to obtain one of the mixed S / Z unidirectional webs described in the present invention.

[0115] Thus, according to one embodiment, a method for preparing the reinforcing material 1 according to the present invention comprises the following successive steps: a1) providing a unidirectional reinforcing web defined within the scope of the present invention, called a mixed unidirectional web S / Z; a2) providing two polymer layers which are nonwoven materials 4, 5; a3) proceeding to bond each of the nonwoven materials to one of the faces of the unidirectional reinforcing web. It includes.

[0116] Advantageously, the preparation method includes, upstream of step a1), a step for manufacturing the unidirectional reinforcing web 2, which step comprises, firstly, applying a twist of 3 turns / m to 15 turns / m to the yarn or a series of carbon S-twist yarns 3 (the twist being applied individually to each carbon yarn 3), and secondly, applying a twist of 3 turns / m to 15 turns / m to the Z-twist yarn carbon yarns 3 or a series of Z-twist carbon yarns 3 (the twist being applied individually to each carbon yarn 3).

[0117] According to an advantageous feature, the layers 4, 5 of polymer fibers which are nonwoven materials have hot tack properties, and the bonding in step a3) is obtained by applying each layer of polymer fibers to each face of the unidirectional reinforcing web, this application being accompanied by or followed by heating of the polymer fibers to soften or melt the polymer fibers and then cooling them.

[0118] As shown in Figure 1A, the unidirectional web 2 is bonded on each side to the veil of polymer fibers 4, 5 in order to produce the reinforcing material 1. The use of a symmetric reinforcing material makes it possible to avoid lamination errors during manual or automatic laying (placement) for forming composite parts, and thus makes it possible to limit the occurrence of defects, especially between layers without a veil. This is advantageously the reason why the unidirectional web 2 is bonded to the polymer fiber veils 4, 5 on each side and the two veils 4, 5 are identical.

[0119] The "porous polymer layer" means a permeable layer that allows a liquid such as a resin to pass through the material and be injected or infused through the material during the formation of the preform or composite part. In particular, the openness factor of such a layer determined according to the method described in WO 2011 / 086266 is in the range of 30% to 99%, preferably in the range of 40% to 70%. A particularly advantageous example of such a layer is a nonwoven material or web.

[0120] Within the scope of the present invention, the "polymer fiber layer" means a veil or nonwoven material.

[0121] The "nonwoven material" or "ply" conventionally means a set of continuous or short fibers that are randomly arranged optionally. These nonwoven materials or veils can be produced, for example, by dry, wet or spunlace methods, such as extrusion ("spunbond"), meltblown extrusion ("meltblown"), fiberizing spray applicator or solvent spinning ("electrospinning", "flash spinning", "force spinning"), all of which are well known to those skilled in the art. In particular, the constituent fibers of the nonwoven material can have an average diameter in the range of 0.5 μm to 70 μm, preferably 0.5 μm to 20 μm. The nonwoven material can be made of short fibers or preferably continuous fibers. In the case of a nonwoven material formed from short fibers, the fibers can have a length of, for example, 1 mm to 100 mm. Preferably, the nonwoven material used provides a random and preferably isotropic coating.

[0122] Within the scope of the present invention, since the reinforcing material is classified as dry, the total weight represented by the non-woven materials 4 and 5 does not exceed 10% of the total weight of the reinforcing material 1 according to the present invention, and typically occupies 0.5% to 10% of the total weight of the reinforcing material 1, preferably 2% to 6% of its total weight.

[0123] Within the scope of the present invention, it is advantageous that the non-woven material or veil used is essentially thermoplastic, and in particular, it 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 thermosetting polymer. The thermoplastic or thermosetting non-woven material or veil is preferably a polyamide (PA: PA6, PA12, PA11, PA6,6, PA6,10, PA6,12, etc.), a copolyamide (CoPA), a polyamide-block ether or ester (PEBAX, PEBA), a polyphthalamide (PPA), a polyester (polyethylene terephthalate - PET -, polybutylene terephthalate - PBT -, etc.), a copolyester (CoPE), a thermoplastic polyurethane (TPU), a polyacetal (POM), a polyolefin (PP, HDPE, LDPE, LLDPE, etc.), a polyethersulfone (PES), a polysulfone (PSU), a polyphenylene sulfone (PPSU), a polyetheretherketone (PEEK), a polyetherketoneketone (PEKK), a poly(phenylene sulfide) (PPS), or a polyetherimide (PEI), a thermoplastic polyimide, a liquid crystal polymer (LCP), a phenoxy, a block copolymer such as a styrene-butadiene-methyl methacrylate (SBM) copolymer, a methyl methacrylate-butyl methacrylate (MAM) copolymer, etc., a thermoplastic material selected from these, or a mixture of fibers made from these thermoplastic materials. Naturally, the material is suitable for various types of thermosetting systems used for matrix formation during the subsequent manufacture of composite parts.

[0124] The thickness of the veil before bonding to the unidirectional web is selected according to how they are bonded to the unidirectional web. In most cases, their thickness is very close to the thickness of the desired reinforcement material. It is also possible to select a thicker veil that is laminated at a predetermined temperature during the bonding step so as to obtain the desired thickness. Preferably, the unidirectional web is bonded to two substantially identical veils on each of its large faces in order to obtain a completely symmetrical reinforcement material. The thickness of the veil before bonding on the unidirectional carbon web is, in particular, from 0.5 μm to 200 μm, preferably from 10 μm to 170 μm. In the reinforcement material 1 according to the invention, the thickness of each of the veils 4, 5 after bonding to the unidirectional web is in the range from 0.5 micron to 50 microns, preferably in the range from 3 microns to 35 microns. The thicknesses of the various non-woven materials before bonding are determined by method A with a test area of 2827 mm 2 (disc with a diameter of 60 mm) and an applied pressure of 0.5 kPa.

[0125] Furthermore, advantageously, the areal weight of the veils 4, 5 is in the range of 2 0.2 g / m 2 to 20 g / m.

[0126] The bonding of the unidirectional web 2 to the veils 4, 5 can be carried out in a discontinuous manner, for example only at specific points or zones, but is preferably carried out by a bond that extends over the entire surface of the web classified as continuous.

[0127] The joining of the unidirectional web 2 with the two veils 4, 5 is advantageously carried out according to one of the methods described in patent application WO2010 / 046609 or the method described in application WO2010 / 061114. Continuous production machines and lines such as those described in these documents or in the examples of the present invention can be used. Within the scope of the present invention, especially when a hybrid S / Z unidirectional web is used, by passing the reinforcing material resulting from the joining through an electric conveying system or device, it is possible to produce a reinforcing material by continuously combining the nonwoven materials present on each side of the unidirectional reinforcing web. Such a device is, for example, a conveyor belt driven by one or more drive rollers, through which the reinforcing material circulates after the unidirectional web is placed between the two nonwoven materials, ensuring its application to the nonwoven materials.

[0128] Furthermore, the unidirectional web can be adhered to the two webs by an adhesive layer selected, for example, from epoxy adhesives, polyurethane adhesives, thermosetting adhesives, polymerizable monomer-based adhesives, structural acrylic adhesives or modified acrylic adhesives, and hot melt adhesives. However, the joining is usually achieved by the hot tack properties of the heated veil during a hot compression step that ensures the joining between, for example, the unidirectional web and the ply. This step causes the softening of the thermoplastic fibers of the ply and allows the unidirectional web to be joined to the veil after cooling. The heating and pressure conditions are adapted to the materials of the veils and their thicknesses. The hot compression step is usually carried out over the entire surface of the unidirectional web at a temperature in the range of Tf_veil - 15 °C to Tf_veil + 60 °C (where Tf_veil indicates the melting temperature of the web) and under a pressure of 0.1 MPa to 0.6 MPa. Thus, a compression ratio of the veil before and after joining in the range of 1 to 10 can be achieved. The step of laminating the veil onto the unidirectional carbon web 2 is also essential for accurately controlling the final thickness of the reinforcing material 1. In fact, depending on the temperature and pressure conditions, especially during lamination, it is possible to correct and thus adjust the thickness of the veil present on each side of the reinforcing material.

[0129] The reinforcing material according to the invention is easy to handle due to the presence of thermoplastic veils laminated on each side of the unidirectional web. This structure also facilitates cutting, particularly without fraying, in a direction not parallel to the fibers of the unidirectional web, especially in the transverse or diagonal directions.

[0130] The reinforcing material 1 according to the invention is flexible and can be wound up. The reinforcing material 1 can be manufactured in a large length corresponding to the available length of the carbon yarns. After manufacture and before being used for the subsequent manufacture of preforms and parts, the reinforcing material 1 is usually wound in the form of a roll around a spool.

[0131] To manufacture composite parts, a stack or drape of the reinforcing material (also called ply) according to the invention is produced. In the conventional manner, the reinforcing material according to the invention is cut to the desired size for the manufacture of the parts, plies, stacks or preforms to be produced. In a stack, several plies of the reinforcing material are stacked on top of each other.

[0132] When the reinforcing material has a sufficient width to produce the desired part and the part is slightly complex, the ply can be made from a single reinforcing material according to the invention. However, more often, in the case of large or complex parts, the ply is made from an assembly of reinforcing materials 1 according to the invention juxtaposed so as to cover the entire surface required to produce the desired part. In this case, the exact placement of the reinforcing material is required. In an automated method, the device for transporting and applying the reinforcing material comprises one or more guide members or guides along which the reinforcing material is transported and conveyed. Devices comprising an application head provided with such guide members or guides are described in particular in WO 2006 / 092514 and EP 2376276. Coriolis Composites SASU (56530 Quai Condorcet, Kevan, France), MTorres Disenos Industriales SAU (Torres de Erroltz, Navarra, Spain), ElectroImpact Inc (98275 Mukilteo, Washington, USA), Mikrosam DOO (7500 Prilep, Macedonia) also offer such devices. Within the scope of the invention, a more accurate placement is achieved by centering the reinforcing material 1 according to the invention, including a mixed S / Z unidirectional web, in particular one of those more precisely described within the scope of the invention, and thus it has been found that the risk of defects such as gaps, overlaps, wrinkles or undulations during application is reduced. Thus, parts manufactured using the reinforcing material 1 according to the invention, including a mixed S / Z unidirectional web, in particular one of those more precisely described within the scope of the invention, are particularly satisfactory.

[0133] Furthermore, in order to manufacture a composite part, several plies are stacked on top of each other to produce a stack of plies. Thus, the imperfections of reinforcement 1 are reproduced in each ply and thus accentuated in the stack. Thus, again, the reinforcement 1 according to the invention comprising a hybrid S / Z unidirectional web with more homogeneous and reproducible properties is particularly advantageous. In the resulting stack, the plies are generally arranged such that at least two unidirectional webs of the ply are oriented in different directions. From one ply to another, all or only some of the unidirectional webs may have different directions, while others may have the same direction. The preferred orientations are most often at an angle of 0°, +45° or -45° (equivalent to +135°), and +90° with respect to the main axis of the part to be manufactured. The main axis of the part is generally the largest axis of the part, and 0° is integrated with this axis. For example, by choosing a folding orientation, it is possible to create a pseudo-isotropic, symmetric, or oriented stack. As an example of a pseudo-isotropic laminate, the laminate may have an angle of 45° / 0° / 135° / 90°, or 90° / 135° / 0° / 45°. Examples of symmetric laminates include 0° / 90° / 0°, or 45° / 135° / 45°. Before adding the resin required to manufacture the part, it is possible to join the plies to each other within the stack, thereby producing a preform, by means of an intermediate step of preforming or welding under temperature and vacuum, in particular at several points after each ply has been added. In particular, assemblies of 2 to 300 plies, in particular 16 to 100 plies, can be considered.

[0134] Advantageously, the stacks are joined not by sewing or knitting together, but by welds produced by the polymer properties of the veil present in the stack, in particular the thermoplastic properties. For this purpose, the heating / cooling operation is carried out over the entire surface of the stack or at least in certain zones of the surface of the stack. Heating melts or at least softens the veil. Such bonding using the thermoplastic properties of the veil is advantageous in order to avoid all the drawbacks of the presence of sewing or knitting threads, in particular problems such as waviness, microcracks and the subsequent reduction in the mechanical properties of the composite parts obtained.

[0135] The lamination can be achieved by adding each ply one by one and joining each ply after it has been added. One example is automatic ply application as described in International Publication No. WO 2014 / 076433 and International Publication No. WO 2014 / 191667 of patent applications. Also, for example, in order to obtain a preform formed from a ply applied flat, the applied ply can be reheated in its entirety (either by preheating each ply one by one or without heating). Then, a person skilled in the art can apply a predetermined temperature and pressure (for example, vacuum or press system) and use conventional means for hot forming. In particular, the application of the reinforcing material according to the invention can be carried out continuously while applying a pressure perpendicular to the application surface according to a method known by the abbreviations AFP (Automated Fiber Placement) or ATL (Automated Tape Laying), as described in International Publication No. WO 2014 / 076433A1 or International Publication No. WO 2014 / 191667 of the above documents, for example, in order to apply it.

[0136] To manufacture the composite part, a thermosetting or thermoplastic mold resin or matrix, or a mixture of thermosetting resins, is then added into the mold containing the ply, for example by injection (resin transfer molding process), or by infusion (through the thickness of the ply: liquid resin infusion process or resin film infusion process). According to a less preferred embodiment, it is also possible to perform manual coating / impregnation with a roller or brush on each ply continuously applied to the shape of the mold used before lamination.

[0137] The matrix used is of the thermosetting or thermoplastic type, or a mixture of a thermoplastic resin and a thermosetting resin. The resin to be injected is selected, for example, from the following thermosetting polymers: epoxides, unsaturated polyesters, vinyl esters, phenolics, polyimides and bismaleimides.

[0138] Then, the composite part is obtained after the heat treatment step. In particular, the composite part is generally obtained by performing a heat treatment according to the conventional curing cycles of the polymers under consideration, i.e., as recommended by the suppliers of these polymers and known to those skilled in the art. This step of curing the desired part is carried out by polymerizing / crosslinking according to a defined cycle under a given temperature and pressure, followed by 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.

[0139] The above-described lamination and bonding methods can also be carried out with any type of reinforcing material intended to be bonded to the thermosetting resin for the manufacture of the composite part. The composite part is made on each side from a unidirectional web of carbon fibers bonded to a veil of thermoplastic fibers and a reinforcing material other than, in particular, those defined in the claims of this patent application. In fact, such laminates are advantageous in terms of drapability and permeability, regardless of the unidirectional veils and webs used. Of course, preferably, the reinforcing material conforms to that described within the scope of the present invention in terms of thickness and areal weight, considering that vacuum infusion enables the achievement of a high fiber volume ratio (FVR).

[0140] The following examples are provided to illustrate the present invention and are not intended to be limiting.

[0141] A first series of tests was conducted to obtain the data shown in Table 3 below.

[0142] Part A

[0143] [Table 3]

[0144] In Table 3 above, the reinforced material 1 tested includes a unidirectional reinforcing web bonded to a veil on each side.

[0145] For the unidirectional reinforcing web, 12K intermediate modulus (IM) carbon yarn sold by HEXCEL Corporation of Stamford, Connecticut, USA was used. Materials 1 to 3 use such untwisted carbon reinforcing yarn. Materials 4 to 12 are the reinforcing materials of the present invention having individually twisted carbon reinforcing yarns (twisted yarns) as described above. Materials 13 to 18 are reinforcing materials made of twisted yarns having a twist larger than that envisioned by the present invention, and the materials cannot be produced because they are separated at any of the manufacturing stage, handling stage, or application stage and thus become unusable.

[0146] For the layer of polymer fibers selected from non-woven materials, 4 g / m 2 of the copolyamide non-woven fabric 1R8 D04 sold by Protechnic was used. According to International Publication No. WO 2010 / 046609, the veil was bonded to the unidirectional web of carbon reinforcing yarns. More precisely, the reinforcing material 1 according to the present invention was manufactured on a production line using the machines and parameters as described in International Publication No. WO 2010 / 061114 of the application and described below with reference to FIG. 19.

[0147] The desired twisted carbon yarn 3 is unwound from the corresponding spool 30 of the carbon yarn attached to the creel 40, passes through the comb 50, and is supplied to the machine shaft by the guide roller 60, the comb 70, and the guide bar 80a.

[0148] After being preheated by the heating bar 90, the carbon yarn 3 is expanded by the expanding bar 80b and the heating bar 100 so as to have the desired carbon basis weight of the unidirectional web 2. The veil rolls 13a and 13b are unwound without tension and conveyed by the continuous belts 15a and 15b fixed between the freely rotating non-electric rolls 14a, 14b, 14c, 14d and the heated bars 12a, 12b.

[0149] The veils 4 and 5 are preheated in zones 11a and 11b before contacting the carbon yarn 3 and are laminated on each side of the two heated bars 12a and 12b with controlled gaps. The calendar 16 can be cooled and then applies pressure to the unidirectional web having veils on each side to produce the reinforcing material 1 in the form of a tape. The deflector roller 18 redirects the reinforcing material 1 towards the traction system comprising the motor-driven winding trio 19 and then towards the winding device 20, enabling the formation of a roll of the reinforcing material 1 thus formed.

[0150] Note that in this production line, the belts are not electric and are pulled by the reinforcing yarn itself.

[0151] Furthermore, as described in International Publication No. WO 2010 / 061114 of the application and presented in its Figure 8, some reinforcing materials of the present invention presented in the form of a tape were manufactured simultaneously. Each carbon twisted yarn forming the unidirectional web to be formed was drawn from a roll of selected twisted yarns pre-manufactured. A unidirectional web of a desired width was made parallel to a selected number of yarns and spaced apart with sufficient space left between each unidirectional web. A single nonwoven material (corresponding to veils 4 and 5) covering the various unidirectional webs and the gaps was thus bonded to all the unidirectional webs and on each of their surfaces. After the nonwoven material was laminated to the webs, it was cut by a cutting element heated between each of the formed unidirectional webs, and thus various reinforcing materials according to the present invention were obtained, which were manufactured side by side. The gap between each unidirectional web was in the range of 0.5 mm to 2 mm so that cutting could be performed along the edge between each unidirectional web, and various reinforcing materials manufactured continuously and in parallel were obtained.

[0152] 1) Vacuum thickness:

[0153] During the automatic application of complex shapes or thick preforms, it is important to have a material that swells as little as possible and thus has an applied material thickness close to the final thickness of the composite part. In fact, if the material exhibits a significant overrun and thus a thickness much higher than the final thickness after the manufacture of the laminate, there are significant defects in the part. The defects are mainly due to excessive length and generate wrinkles. This is unacceptable to those skilled in the art. To characterize this property, the thickness of the preform is measured after automatic application before and after being placed under vacuum.

[0154] As illustrated in FIG. 12, a 200×200 mm preform P having a symmetric pseudo-isotropic laminate, more precisely a [+45 / 0 / -45 / 90]3s drape, was formed. The preform P was placed on a plate. The thickness was measured using a FANUC robot and a HEIDENHAIN / ST3077 LVDT probe. The tip of the probe is a circular key with a diameter of 50 mm. The probe measures the thickness of the preform at five points P1 to P5, thereby obtaining the average thickness value of the preform. The measurement is performed every 50 mm in the x direction and every 50 mm in the y direction.

[0155] Next, using a vacuum bag and a pump, the preform is placed under vacuum (residual pressure less than 15 mbar). Then, the thickness of the assembly is measured and the thickness of the consumables is subtracted to obtain the thickness of the preform under vacuum.

[0156] Next, the ratio of the thickness under non-vacuum to the thickness under vacuum is calculated. The higher this ratio, the greater the thickness under non-vacuum compared to the thickness under vacuum, and the greater the risk of defects in the final part. The goal is to minimize this ratio.

[0157] Table 4 below summarizes the ratio of the thickness (under non-vacuum) to the theoretical thickness (under vacuum) of Materials 2 to 12.

[0158]

Table 4

[0159] Compared with prior art Materials 2 and 3, Materials 4 to 12 according to the present invention enable minimization of the ratio of the thickness under non-vacuum to the thickness under vacuum. Therefore, the inventive concept of the present invention enables reduction of overrun.

[0160] 2) Influence of twist on the quality of automatic dispensing.

[0161] The automated preform application process must not cause defects in the preform. The structure of the reinforcing yarn can potentially affect the quality of the application. Therefore, it is necessary to determine whether the twist of the reinforcing yarn affects the quality of the preform after application.

[0162] More precisely, the twist of the reinforcing yarn can affect the so-called "shearing" phenomenon. When laying up the reinforcing materials (uniaxial webs 2 and veils 4, 5) by overlapping them, due to the pressure and movement of the robot head during laying up, the reinforcing yarn of the ply located directly below the next ply is subjected to shearing. This shearing is most dominant in the initial part of the layup. As several plies are applied, this in-ply shearing may increase, resulting in a local increase in the thickness of the preform, the appearance of defects (such as wrinkles, fraying, delamination, etc.), and a decrease in the quality of the preform.

[0163] Industrial-scale automatic ply application tests were conducted using twisted reinforcing yarns. The layup was carried out using a Coriolis C1 robot equipped with a Coriolis 16 ply 1 / 4-inch AFP head and 12 kw laser-type heating means. In this particular case, only 8 out of 16 webs were applied simultaneously and side by side. The following heating rules are described in Table 5 below.

[0164]

Table 5

[0165] On the suction table, a ply made of twisted reinforcing yarn was continuously draped at 0° to form a 500 mm (0° direction) × 150 mm preform. The start of the reinforcing yarn laying, which is carried out according to the radar down direction represented by arrow F, is always located at the same place (rectangular zone Z1 in Figure 13) on the preform. Therefore, the thickness studied was located in this zone Z1.

[0166] After draping each ply, thickness measurements were taken in the area of the start of the preform layup (points P’1, P’2, P’3 within zone Z1) using a grid draw, a support made from an aluminum bar, and a 1 kg weight indicating a pressure of 0.02 bar applied to the preform during thickness measurement. During the measurement, the thickness measuring device was always located in the same place. This thickness measuring device is removed in order to allow the robot to pass through and then be repositioned after application of each ply. If it is determined that the quality of the preform is insufficient, the draping is stopped.

[0167] Materials 4 and 8 according to the present invention (Table 3) were compared with comparative materials 2 and 3, respectively.

[0168] Figures 14 and 15 show the change in overrun as a function of the number of plies applied for comparative material 3 and material 8 according to the present invention (Figure 14), and for comparative material 2 and material 4 according to the present invention (Figure 15).

[0169] Note that the overrun is defined as the ratio of the total thickness of the preform having the plies applied to X to the number X of plies applied.

[0170] Overrun (mm) = total thickness of the preform (mm) / number of plies applied.

[0171] This gives an indication of the average thickness of the ply and thus enables quantification of the overrun phenomenon. To maximize the inflation phenomenon, a stack of reinforcing materials is made using a unidirectional web extending at 0°.

[0172] As shown in Figures 14 and 15, the change in thickness per ply as a function of the number of plies applied is smaller for the twisted reinforcing yarns (material 8 or 4 of the present invention, respectively) than for the microperforation method (comparative material 3 or 2, respectively). The results using the twisted reinforcing yarns demonstrate a reduction in overrun after application and better quality of the preform compared to equivalent materials having untwisted and microperforated reinforcing yarns according to the prior art.

[0173] 3) Influence of twist on the transverse permeability of the reinforcement:

[0174] It is important to verify that the present invention maintains the transverse permeability of the reinforcement at the same level as that obtained using a prior art microperforated reinforcement. This can be defined as the ability of a fluid to pass through the fibrous material. This is measured in m 2 and is shown in the following Table 6. The values shown in Table 6 were measured using the apparatus and measurement techniques described in the paper "Problematique de la mesure de la permeabilite transverse de preformes fibreuses pour la fabrication de structures composites" [Measuring the transverse permeability of fibrous preforms for the manufacture of composite structures] by Romain Nunez, supported by the Ecole Nationale Superieure des Mines de Saint Etienne on October 16, 2009, for further details.

[0175] In particular, the measurement is carried out using two identical cylindrical chambers to monitor the thickness of the sample during the test, making it possible to reduce the influence of "race tracking" (the passage of fluid adjacent to or on the "sides" of the material through which the permeability is measured). The fluid used is water and the pressure is 1 bar + / - 0.01 bar. A preform with a diameter of 270 mm was fabricated according to a symmetric pseudo-isotropic layup, [+45 / 0 / 135 / 90]S, 8 plies.

[0176] Table 6 below lists the lateral transmission values measured for Comparative Materials 1, 2, and 3, and Materials 4 to 12 according to the present invention (see Table 3) at fiber volume ratios (FVR) of 50%, 55%, and 60%. The lateral transmission values in Table 6 found for three samples with different fiber volume ratios for each material are summarized in FIG. 16.

[0177]

Table 6

[0178] When all the reinforcing yarns are twisted either at 8 turns per meter or 10 turns per meter, the lateral transmission of the materials according to the present invention (Materials 4 and 5) is equivalent to that of the comparative micro-perforated material (Comparative Material 2) for the three volume ratios studied. The choice of twist depends on the titer and the number of filaments of the yarn. Different twists can yield similar results for yarns with different titers and filament numbers.

[0179] 280g / m 2 For a carbon fiber basis weight of, it appears that by twisting the reinforcing yarn at 10 turns per meter, a better average lateral transmission is obtained than that of the prior art micro-perforated material.

[0180] As the number of turns per meter decreases (Material 6 compared to Materials 4 and 5, and Material 9 compared to Material 8), the lateral transmission of the material decreases. However, it remains higher than that of the comparative material without micro-perforations (Comparative Material 1).

[0181] The fewer the number of twisted reinforcing yarns, the lower the lateral transmission (Material 7) even if the number of turns per meter is high (compared to Material 4). To improve the lateral transmission by twisting the reinforcing yarns, it is more effective to twist all the reinforcing yarns together rather than trying to increase the number of turns per meter of each individual twisted reinforcing yarn.

[0182] 4) Effect of twist of reinforcing yarns on mechanical properties of composite materials:

[0183] A 430 mm × 430 mm preform with a stacking sequence suitable for carbon weight per unit area was placed under pressure in an injection mold. A frame of known thickness surrounding the preform was used to achieve the desired fiber volume ratio (FVR). An epoxy resin sold by HEXCEL Corporation, Stanford, Connecticut, USA, as reference HexFlow RTM6, was injected at 80 °C under 2 bar through the preform maintained at 120 °C in a press. The pressure applied by the press was 5.5 bar. After filling the preform and the resin exiting the mold, the outlet tube was closed and the curing cycle was initiated (heating to 180 °C at 3 °C / min, followed by post-curing at 180 °C for 2 hours and cooling at 5 °C / min).

[0184] The specimens were then cut to appropriate sizes and subjected to the open-hole (OHC) compression test and the solid plate (UNC) compression test summarized in Table 7 below.

[0185] [Table 7]

[0186] The tests were conducted using eight reinforcing materials 4 - 11 according to the present invention and comparative materials 2 and 3 (Table 3). The results of the open-hole compression (OHC) test are shown in Table 8 below.

[0187] [Table 8]

[0188] In the prior art, it is known that the carbon weight per unit area can affect the mechanical results. Generally, the higher the carbon weight, the lower the mechanical compression properties tend to be. In this application, the results are compared with the carbon weight.

[0189] When the weight per unit area is 210 g / m 2 there is no difference between the comparative materials and the materials according to the present invention for the open-hole compression test (OHC). When the weight per unit area is 280 g / m 2The same conclusion can be drawn for the basis weight. At a basis weight of 350 g / m 2 it is not possible to compare with the micro-perforated material, as this is not achievable.

[0190] The results of the compression tests for the solid plate (UNC) are shown in Table 9 below.

[0191] (Missing)

[0192]

Table 9

[0193] From the results in Table 9, it is possible to draw the same conclusion with respect to the open-hole test.

[0194] 5) Influence of the twist of the reinforcing yarn on the transverse electrical conductivity:

[0195] The 335 mm × 335 mm preform is composed of reinforcing plies, the number of which depends on the basis weight of the carbon reinforcing yarn. The stacking sequence is [0 / 90]ns, where ns is an integer depending on the basis weight of the carbon reinforcing yarn in order to obtain a panel with a final thickness of 3 mm and a fiber volume of 60%. The preform was then placed in an injection mold under a given pressure. In the same way as the mechanical compression test (see paragraph 4 above), a panel of composite reinforcement / RTM6 was formed by the injection method (same parameters as for the compression plate).

[0196] Twenty-four 40 mm × 40 mm specimens, uniformly distributed over the whole panel, were pre-cut using a water jet cutter. Next, the carbon fibers were exposed on both sides of the pre-cut panel by sandblasting. Next, the front and back of the panel were treated to apply a layer of conductive metal, typically tin and zinc, by an electric arc process. The application of the metal can be removed from the sample field by sandblasting or sanding. This application of the conductive metal enables a low contact resistance between the sample and the measuring equipment. The individual samples were then cut out from the panel.

[0197] The resistance was determined using a power supply (TTi EL302P programmable 30V / 2A power supply, Thurlby Thandar Instruments, Cambridge, UK) that can vary current and voltage. The sample was in contact with two electrodes of the power supply. These electrodes were brought into contact by means of clamps. Care must be taken to ensure that the electrodes do not come into contact with each other or with other metals. A current of 1 A was applied and the resistance was measured by two other electrodes connected to a voltmeter / ohmmeter. The test was carried out for each sample measured. Subsequently, the conductivity value was calculated from the resistance value using the dimensions of the sample and the following formula.

[0198] Resistivity (ohm·m) = Resistance (ohm) × Area (m 2 ) / Thickness (m)

[0199] Conductivity (S / m) = 1 / Resistivity

[0200] Lateral electrical conductivity tests were carried out using Comparative Material 2 and Materials 4 and 5 according to the present invention (Table 3). The test results are shown in Table 10 below.

[0201]

Table 10

[0202] Comparative Material 2 and Materials 4 and 5 according to the present invention have the same fiber basis weight. The average lateral electrical conductivity of Material 4 according to the present invention is higher than the average lateral electrical conductivity of Comparative Material 2 micro-perforated according to the prior art. By twisting the reinforcing yarns, the lateral electrical conductivity of the reinforcing material is improved.

[0203] (Missing)

[0204] Part B

[0205] The results of a second series of tests carried out are shown in Table 11 below. The materials obtained were not micro-perforated except for Comparative Material 27.

[0206]

Table 11

[0207] Manufacture of the reinforcing material according to the present invention

[0208] These tests were carried out on a new production line that meets the requirements of industrial-scale production, which requires not only a higher production speed but also higher safety in order to reduce production line stoppages and wear of line components. Such an increase in speed also increases the overall inertia of the line, generating more friction events of the material with the force required to drive the various points / rollers of the line, and thus especially the belt. As a result, the manufacturing line described above in connection with FIG. 19 was modified by introducing the electrification of the continuous belts 15a and 15b. The belts 15a and 15b are independently motor-driven by the rollers 14a and 14c, and the rollers 14b and 14d remain free to rotate.

[0209] This increase in production speed highlights the difficulties encountered in the production of unidirectional webs with minimized defects such as gaps, overlaps, or undulations between the yarns, using twist-reinforced yarns all having the same type of S-twist or Z-twist. In fact, despite the use of combs or guide rollers, the trajectory of the reinforcing yarns is not fully controlled, resulting in the appearance of defects. As proposed within the scope of the present invention, these risks can even be minimized or avoided by using a mixed S / Z unidirectional web.

[0210] In this industrial-scale production line, several materials 19 were manufactured in parallel, resulting in a higher production speed.

[0211] Similar to the first series of tests, several reinforcing materials according to the invention in tape form were manufactured simultaneously.

[0212] Similarly, several materials 20 and several materials 21 were manufactured in parallel. The obtained materials 20 and 21 were found to be more regular, especially at the edges, compared to material 19. In fact, the quality of the yarn alignment was better during the formation of the unidirectional web in the case of materials 20 and 21. As a result, the distance between the two unidirectional webs manufactured side by side was more regular, thereby facilitating the cutting of the two veils laminated on the two surfaces between the two formed unidirectional webs.

[0213] Similar observations were made for materials 22 and 23, and 24 and 25. In the case of material 22 with only S-twisted yarns, more defects such as wrinkles, gaps or overlaps between yarns, and irregularities at the edges were observed compared to the case of material 23 using a series of SZSZSZ yarns. Similarly, in the case of material 24 containing only Z-twisted yarns, more defects such as wrinkles, gaps or overlaps between yarns, and irregularities at the edges were observed compared to the case of material 25 using a series of SSZZSS yarns.

[0214] Furthermore, in the case of material 26 containing 18 yarns having an arrangement of 7 S-twisted yarns, 5 Z-twisted yarns, and then 6 S-twisted yarns, the formation of the unidirectional web by the aforementioned method resulted in a unidirectional web as shown in FIG. 18. As can be seen from this figure, there is a significant gap at the junction of 7 S-twisted yarns / 5 Z-twisted yarns, which constitutes a quality defect by causing a continuous gap with a width of more than 1 mm along the entire length of the web. The group of Z-twisted yarns is drawn to the right and the group of S-twisted yarns is drawn to the left. As a result, an unsatisfactory continuous gap occurs. This order does not correspond to the definitions P1, P2, I1, and I2 of the mixed S / Z unidirectional web provided in accordance with the present invention, which results in a more balanced unidirectional web with respect to the number of S-twisted and Z-twisted yarns and has a greater coverage due to a reduced risk of inter-yarn gaps.

[0215] Therefore, within the scope of the present invention, during the formation of a unidirectional web using a guide device or a comb, or despite the use of a comb, a twist-reinforced yarn having the same twist or a configuration not corresponding to the definitions P1, P2, I1, and I2 for a hybrid S / Z unidirectional web provided within the scope of the present invention was observed to have a deflection phenomenon in the trajectory of the reinforcing yarn. These phenomena do not occur in unidirectional webs having three or fewer yarns. The use of the hybrid S / Z unidirectional web proposed within the scope of the present invention solves the problems of unidirectional webs consisting of more than three yarns.

[0216] Furthermore, the deflection phenomenon worsened with an increase in the width of the manufactured reinforcing material. This problem is even more pronounced for manufacturing widths exceeding 7 mm and further exceeding 12 mm. The risk of deflection of the reinforcing yarn, which is solved by the hybrid unidirectional S / Z web proposed within the scope of the present invention, occurs regardless of the manufacturing method used, i.e., whether a plurality of reinforcing materials are manufactured in parallel. In fact, when the deflection phenomenon occurs, it causes problems during the application of the material according to the present invention, leading to insufficient positioning.

[0217] Automatic application of the reinforcing material according to the present invention

[0218] Materials 19 to 25 were applied by an automatic application device comprising a guide consisting of guide grooves through which the materials circulate before being applied to the application surface. This guide enables the web to be reliably and properly positioned at the outlet of the application head of the device, thereby enabling the application head to better control the trajectory of the reinforcement material and its positioning on the application surface, as can be seen in the photograph presented in the left part of Figure 17. As shown in Figure 17, in the evaluation of the materials, for obtaining a bonded application, a series of parallel test pieces (SSSS) of material 19 were applied adjacent to each other to perform the application on a flat surface. The same procedure was followed for materials 20 (SZZS) and 21 (SZSZ). With these last two materials, the application is better controlled, resulting in a reduction of the gaps and undulations on the application surface. By observing the behavior of the materials in the guide grooves, it was noted that improper centering of material 19 (SSSS) occurred, thereby abutting against one of the edges of the groove, while materials 20 and 21 are supported in the groove and on its two edges and are very well centered.

[0219] First, for materials 22 and 23, and second, the same findings were observed for materials 24 and 25. In the case of material 22 containing only S-twist yarns, the application is not as good compared to the use of material 23 using a series of SZSZSZ yarns. Similarly, in the case of material 24 containing only Z-twist yarns, more gaps were observed compared to the case of material 25 using a series of SSZZSS yarns. Table 12 shows the average gap widths obtained between two test pieces, measured with a gauge, for the application of materials 24 and 25.

[0220]

Table 12

[0221] It is clear that the use of an SSZZSS web consisting of both S-twist and Z-twist yarns results in a distinct reduction of the zones without reinforcement yarns in the resulting unidirectional web. Number of test pieces 8 Applications 8 Average gap (mm) 0.1 mm 1.5 mm

[0222] Performance of the material according to the present invention

[0223] The performance of the material according to the present invention was evaluated according to the method described in Part A.

[0224] Regardless of whether the unidirectional web consists only of S-twisted yarns or Z-twisted yarns, or whether the unidirectional web consists of both S-twisted yarns and Z-twisted yarns, the advantages of using the twisted yarns proposed in accordance with the present invention are retained with respect to a reduction in the ratio of the non-vacuum thickness to the vacuum thickness, a reduction in overrun, an improvement in the lateral permeability of the material, and an improvement in the lateral electrical conductivity of the material.

[0225] Since the defects of the manufactured reinforcing material are reduced, the mechanical performance is very good.

[0226] The results obtained are shown in Table 13 below.

[0227] (Missing)

[0228]

Table 13

[0229] Compared with the comparative microperforated material 27, the overrun performance of the unidirectional web consisting of both S-twisted yarns and Z-twisted yarns is improved. As a result, the overrun performance is improved regardless of whether the material is a unidirectional web consisting of a series of yarns twisted in the same direction or a unidirectional web consisting of a mixture of S-twisted yarns and Z-twisted yarns. The results obtained are shown in Table 14 below.

[0230]

Table 14

[0231] Also, the lateral transmission performance of the material 23 of the present invention was measured, compared with the lateral transmission performance of the comparative material 27, and is shown in Table 15 below. For the two materials, the lateral transmission rates obtained are equivalent.

[0232]

Table 15

[0233] The lateral electrical conductivity performance of Material 23 according to the present invention was also measured and is shown in Table 16 below.

[0234]

Table 16

[0235] Material 23 according to the present invention provides good electrical properties as compared with Comparative Material 2. In addition, aspects or embodiments that may be included in the present invention are summarized as follows. [1]. A reinforcing material (1) comprising a unidirectional reinforcing web (2) formed of one or more carbon reinforcing yarns (3) and bonded to a layer of polymer fibers (4, 5) that are non-woven fabric materials on each side, wherein the polymer portion of the reinforcing material occupies 0.5% to 10% of its total weight, preferably 2% to 6% of its total weight, and the unidirectional reinforcing web (2) comprises one or a series of individually twisted reinforcing yarns (3) having a twist of 3 turns / m to 15 turns / m, preferably 6 turns / m to 12 turns / m. The reinforcing material (1) is characterized by this. [2]. The reinforcing material (1) according to item 1 above, wherein the unidirectional reinforcing web (2) is formed of a plurality of reinforcing yarns (3), and at least every fifth reinforcing yarn, preferably at least every second or third reinforcing yarn, preferably all reinforcing yarns, are individually twisted with a twist of 3 turns / m to 15 turns / m, preferably 6 to 12 turns / m. [3]. The unidirectional reinforcing web (2) is 126 g / m 2 ~280 g / m 2 , especially 126~210 g / m 2 The reinforcing material (1) according to item 1 or 2 above, characterized by having a basis weight within the range of. [4]. The reinforcing material (1) according to any one of items 1 to 3 above, wherein the unidirectional reinforcing web (2) is formed of one or more carbon reinforcing yarns (3) having a titre of 3 to 24 K, preferably 6 to 12 K. [5]. All of the carbon reinforcing yarns (3) forming the unidirectional reinforcing web (2) are individually twisted to have a twist of 3 turns / m to 15 turns / m, preferably 6 turns / m to 12 turns / m, and the unidirectional reinforcing web (2) thus comprises at least three carbon reinforcing yarns (3) twisted with at least one S-twist reinforcing yarn and at least one Z-twist reinforcing yarn. It is characterized by including, - When the total number of the twisted carbon reinforced yarns (3) forming the unidirectional reinforcing web (2) is an even number, the number of the twisted carbon reinforced S-twisted yarns (3) on one side of the plane Δ and the number of the twisted carbon reinforced S-twisted 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%}, and each end point of the range is rounded to the nearest integer (rounded off) so that the formula defining the range becomes an integer, and the other twisted carbon reinforced yarns (3) are Z-twisted yarns; - When the total number of the twisted carbon reinforced yarns (3) forming the unidirectional reinforcing web (2) is an odd number, the number of the twisted carbon reinforced S-twisted yarns (3) on one side of the plane Δ and the number of the twisted carbon reinforced S-twisted yarns (3) on the other side of the plane Δ are either two integers or an integer plus 0.5, each independently within the range {[(total number of yarns) / 4] - 35%; [(total number of yarns) / 4] + 35%}, and each end point of the range is rounded to the nearest integer or an integer plus 0.5 so that the formula defining the range becomes an integer or an integer plus 0.5, and the other carbon reinforced twisted yarns (3) are Z-twisted yarns; The reinforcing material (1) according to any one of items 1 to 4 above, wherein the plane Δ is a plane parallel to the overall extending direction of the unidirectional web (2) and bisects the unidirectional web (2) perpendicularly to its surface. [6]. The reinforcing material (1) according to item 5 above, having a width exceeding 7 mm, preferably exceeding 12 mm, preferably within the range of 12 mm to 51 mm, and a length of preferably 2 m to 5000 m, preferably 100 m to 2000 m. [7]. The reinforcing material (1) according to any one of items 1 to 6 above, wherein the polymer fiber layers (4, 5) have thermoplasticity, and in particular, are made of a thermoplastic polymer, a partially crosslinked thermoplastic polymer, a mixture of such polymers, or a mixture of a thermoplastic polymer and a thermosetting polymer. [8]. The reinforcing material (1) according to any one of items 1 to 7 above, wherein the polymer fiber layers (4, 5) have hot tack properties, and the bonding with the unidirectional reinforcing web is achieved by these hot tack properties. [9]. The reinforcing material (1) according to any one of items 1 to 8 above, wherein the polymer fiber layers (4, 5) are the same non-woven material.

[10] . The non-woven material is 0.2 g / m 2 ~20 g / m 2 The reinforcing material (1) according to any one of items 1 to 9 above, characterized by having a basis weight within the range of and / or a thickness of 0.5 microns to 50 microns, preferably 3 microns to 35 microns.

[11] . The reinforcing material (1) according to any one of items 1 to 10 above, characterized by not being perforated, sewn, knitted, or woven.

[12] . The following continuous process: a1) Providing a unidirectional reinforcing web (2) formed from one or more reinforcing yarns (3) individually twisted and having a twist of 3 turns / m to 15 turns / m. a2) Providing at least two layers (4, 5) of polymer fibers that are non-woven materials. a3) Bonding each layer of the polymer fibers to each side of the unidirectional reinforcing web. A method for preparing the reinforcing material (1) according to any one of items 1 to 11 above, characterized by including the above.

[13] . The method according to item 12 above, including a process for manufacturing the unidirectional reinforcing web (2) that includes adding a twist of 3 turns / m to 15 turns / m to the reinforcing yarn or a series of yarns upstream of step a1), and the twist is added individually to each yarn.

[14] . The unidirectional reinforcing web (2) is formed from a plurality of reinforcing yarns (3), and the method includes, upstream of step a1), i) adding a twist of 3 to 15 turns / m to a series of reinforcing yarns, the twist being added individually to each yarn, and ii) optionally aligning the resulting twisted yarns with other reinforcing yarns and juxtaposing the yarns to form a unidirectional reinforcing web, particularly as defined in item 5 above. The method according to item 12 or item 13 above, characterized by including the above.

[15] . The layers (4, 5) of the polymer fibers that are non-woven materials have hot tack properties, and the bonding in step a3) is obtained by applying each layer of the polymer fibers to each side of the unidirectional reinforcing web, and the application is accompanied by or followed by heating the polymer fibers to soften or melt the polymer fibers and then cooling. The method according to any one of items 12 to 14 above, characterized by the above.

[16] . A preform that is at least partially composed of one or more of the materials described in any one of items 1 to 11 above.

[17] . A method for manufacturing a composite part from at least one reinforcing material (1) according to any one of items 1 to 11, characterized in that a thermosetting resin, a thermoplastic resin, or a mixture of a thermosetting resin and a thermoplastic resin is injected or poured into the reinforcing material, the stack of a plurality of reinforcing materials according to any one of items 1 to 11 above, or the preform according to item 16 above.

[18] . The method for manufacturing a composite part according to item 17 above, including a step of forming a ply or stack including a plurality of reinforcing materials (1) according to any one of items 1 to 11 above before the injection or pouring of the resin, during which the reinforcing material (1) is conveyed and continuously circulated within a guide member to ensure its positioning when being laid down to obtain a desired ply or stack.

[19] . The manufacturing method according to item 17 or item 18 above, characterized by including an application or molding that utilizes the hot tack property of the nonwoven material (4, 5), preferably present in the one or more reinforcing materials (1) before the injection or pouring of the resin.

[20] . Use of one or more reinforcing materials (1) according to any one of items 1 to 11 above for manufacturing 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.

[21] . The manufacturing method according to any one of items 17 to 19 above, or the use according to item 20 above, characterized in that a thermosetting resin, particularly an epoxy resin, is injected or poured.

Claims

1. A reinforcing material (1) comprising a unidirectional reinforcing web (2) formed of one or more carbon reinforcing yarns (3) and bonded to layers of polymer fibers (4, 5) which are non-woven materials on each side, wherein the polymer portion of the reinforcing material occupies 0.5% to 10% of its total weight, and the unidirectional reinforcing web (2) comprises one or a series of individually twisted reinforcing yarns (3) having a twist of 3 turns / m to 15 turns / m, the unidirectional reinforcing web (2) has a basis weight in the range of 126 g / m² to 280 g / m², the unidirectional reinforcing web (2) is formed from a plurality of reinforcing yarns (3), and at least every fifth reinforcing yarn is individually twisted with a twist of 3 turns / m to 15 turns / m, and the other reinforcing yarns are untwisted or have a twist not exceeding 15 turns / m, characterized in that the reinforcing material (1).

2. The reinforcing material (1) according to claim 1, wherein the unidirectional reinforcing web (2) is formed from a plurality of reinforcing yarns (3), and at least every second or third reinforcing yarn, or all of the reinforcing yarns, are individually twisted with a twist of 3 turns / m to 15 turns / m.

3. The unidirectionally reinforced web (2) has a basis weight within the range of 126 to 210 g / m ２ The reinforcing material (1) according to claim 1 or 2, characterized in that it has a basis weight within the range of

4. The reinforcing material (1) according to any one of claims 1 to 3, wherein the unidirectional reinforcing web (2) is formed of one or more carbon reinforcing yarns (3) having a titre of 3 to 24 K.

5. All of the carbon reinforcing yarns (3) forming the unidirectional reinforcing web (2) are individually twisted to have a twist of 3 turns / m to 15 turns / m, and the unidirectional reinforcing web (2) thus comprises at least three carbon reinforcing yarns (3) twisted with at least one S-twist reinforcing yarn and at least one Z-twist reinforcing yarn, characterized in that - when the total number of the twisted carbon reinforcing yarns (3) forming the unidirectional reinforcing web (2) is an even number, the number of the twisted carbon reinforcing S-twist yarns (3) on one side of the plane Δ and the number of the twisted carbon reinforcing S-twist yarns (3) on the other side of the plane Δ are each independently an integer in the range {[(total number of yarns) / 4] - 35%; [(total number of yarns) / 4] + 35%}, and each end point of the range is rounded to the nearest integer (rounded off) so that the formula defining the range becomes an 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 unidirectionally reinforced web (2) is odd, the number of twisted carbon reinforcing S-twisted yarns (3) on one side of the plane Δ and the number of twisted carbon reinforcing S-twisted yarns (3) on the other side of the plane Δ are either two integers or one of those integers plus 0.5, and each independently is in the range {[(total number of yarns) / 4] - 35%; [(total number of yarns) / 4] + 35%}, and each end point of the range is rounded to the nearest integer or integer plus 0.5 such that the formula defining the range becomes an integer or integer plus 0.5, and the other carbon reinforcing twisted yarns (3) are Z-twisted yarns; The reinforcing material (1) according to any one of claims 1 to 4, wherein the plane Δ is a plane parallel to the overall extending direction of the unidirectional web (2) and bisects the unidirectional web (2) perpendicularly to its surface.

6. The reinforcing material (1) according to claim 5, characterized in that it has a width exceeding 7 mm and a length of 2 m to 5000 m.

7. The reinforcing material (1) according to any one of claims 1 to 6, wherein the polymer fiber layers (4, 5) are thermoplastic and consist of a thermoplastic polymer, a partially crosslinked thermoplastic polymer, a mixture of such polymers, or a mixture of a thermoplastic polymer and a thermosetting polymer.

8. The reinforcing material (1) according to any one of claims 1 to 7, wherein the polymer fiber layers (4, 5) have hot tack properties and the bonding to the unidirectionally reinforced web is achieved by these hot tack properties.

9. The reinforcing material (1) according to any one of claims 1 to 8, wherein the polymer fiber layers (4, 5) are the same nonwoven material.

10. The non-woven fabric material has a basis weight within the range of 0.2 g / m ２ to 20 g / m ２ and / or a thickness of 0.5 micron to 50 microns, and is characterized as the reinforcing material (1) according to any one of claims 1 to 9.

11. The reinforcing material (1) according to any one of claims 1 to 10, characterized in that it is not perforated, sewn, knitted, or woven.

12. The following continuous steps: a1) Providing a unidirectionally reinforced web (2) formed from one or more reinforcing yarns (3) individually twisted and having a twist of 3 turns / m to 15 turns / m; a2) Providing at least two layers (4, 5) of polymer fibers that are nonwoven materials; a3) Bonding each layer of the polymer fibers to each surface of the unidirectionally reinforced web; A method for preparing the reinforcing material (1) according to any one of claims 1 to 11, characterized by including the above steps.

13. A process for manufacturing the unidirectional reinforcing web (2), including adding a twist of 3 turns / m to 15 turns / m to the reinforcing yarn or a series of yarns upstream of step a1), wherein the twist is applied individually to each yarn, the method according to claim 12.

14. The unidirectional reinforcing web (2) is formed from a plurality of reinforcing yarns (3), and the method includes, upstream of step a1), i) adding a twist of 3 to 15 turns / m to a series of reinforcing yarns, wherein the twist is applied individually to each yarn, and ii) optionally aligning the resulting twisted yarns with other reinforcing yarns and juxtaposing the yarns to form a unidirectional reinforcing web, the method according to claim 12 or claim 13.

15. The layer (4, 5) of polymer fibers, which is a non-woven material, has hot tack properties, and the bonding in step a3) is obtained by applying each layer of the polymer fibers to each side of the unidirectional reinforcing web, wherein the application is accompanied by or followed by heating of the polymer fibers to soften or melt the polymer fibers and then cooling, the method according to any one of claims 12 to 14.

16. A preform that is at least partially composed of one or more of the materials described in any one of claims 1 to 11.

17. A method for manufacturing a composite part from at least one reinforcing material (1) according to any one of claims 1 to 11, wherein a thermosetting resin, a thermoplastic resin, or a mixture of a thermosetting resin and a thermoplastic resin is injected or poured into the reinforcing material, a stack of a plurality of reinforcing materials according to any one of claims 1 to 11, or the preform according to claim 16.

18. Before the injection or pouring of the resin, the method includes forming a ply or stack including a plurality of reinforcing materials (1) according to any one of claims 1 to 11, wherein, when the reinforcing materials (1) are laid down to obtain a desired ply or stack, they are conveyed and continuously circulated within a guide member to ensure their positioning, the method for manufacturing a composite part according to claim 17.

19. The manufacturing method according to claim 17 or claim 18, characterized by including an application or molding that utilizes the hot tack property of the nonwoven material (4, 5) present in the one or more reinforcing materials (1) before the injection or casting of the resin.

20. Use of one or more reinforcing materials (1) according to any one of claims 1 to 11 for manufacturing a preform or composite part bonded to a thermosetting resin, a thermoplastic resin, or a mixture of a thermosetting resin and a thermoplastic resin.

21. The manufacturing method according to any one of claims 17 to 19, or the use according to claim 20, characterized in that the thermosetting resin is injected or cast.

22. The manufacturing method or use according to claim 21, wherein the thermosetting resin is an epoxy resin.

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