Reinforcing material comprising a porous layer of a reactive thermoplastic polymer and associated processes

Abstract

The present invention relates to a reinforcing material comprising at least one fibrous reinforcement and associated with a thermoplastic porous layer on at least one of its faces, said thermoplastic porous layers representing at most 10% of the total mass of the reinforcing material, preferably from 0.5 to 10% of the total mass of the reinforcing material, and preferably from 2 to 6% of the total mass of the reinforcing material, characterized in that said thermoplastic porous layer or each of said present thermoplastic porous layers comprises a so-called reactive thermoplastic polymer or consists of one or more reactive thermoplastic polymers, a reactive thermoplastic polymer having -NH2 functional groups in an amount greater than 0.15 meq / g of reactive thermoplastic polymer and / or having -COOH functional groups in an amount greater than 0.20 meq / g of reactive thermoplastic polymer.The invention also relates to methods for manufacturing said reinforcing materials, to preforms, to methods for manufacturing composite parts, and to composite parts using said reinforcing materials.

Description

Technical Field

[0001] The present invention relates to the technical field of reinforcing materials suitable for the construction of composite parts. More specifically, the invention relates to reinforcing materials suitable for the production of composite parts in combination with an injected or infused resin. Previous technique

[0002] The manufacture of composite parts or articles, that is to say comprising, on the one hand, one or more fibrous reinforcements, in particular of the type unidirectional fibrous sheets and, on the other hand, a matrix (which is, most often, mainly of the thermosetting type and may include one or more thermoplastics) can, for example, be carried out by a process called "direct" or "LCM" (from the English "Liquid Composite Moulding").A direct process is defined by the fact that one or more fiber reinforcements are used in a "dry" state (i.e., without the final matrix), with the resin, or matrix, being applied separately. This can be done, for example, by injection into the mold containing the fiber reinforcements (RTM, or Resin Transfer Moulding), by infusion through the thickness of the fiber reinforcements (LRI, or RFI, or Resin Film Infusion), or by manual coating / impregnation using a roller or brush on each of the individual layers of fiber reinforcements applied successively to the mold. In the context of composite part manufacturing, particularly in the aerospace sector, the production rate for mass production can be high. For example, for the manufacture of single-aisle aircraft, aerospace manufacturers often require the ability to produce several dozen aircraft per month.Direct processes such as infusion or injection are processes of great interest that can meet this requirement.

[0003] For RTM, LRI, or RFI processes, it is generally necessary to first fabricate a fibrous preform or stack in the shape of the desired finished article. This preform or stack is then impregnated with a resin to form the matrix. The resin is injected or infused using differential pressure and temperature. Once the entire required amount of resin is contained within the preform, the assembly is heated to a higher temperature to complete the polymerization / crosslinking cycle and thus harden it.

[0004] Composite parts used in the automotive, aerospace, and marine industries are subject to particularly stringent requirements, especially regarding mechanical properties. To save fuel and facilitate maintenance, the aerospace industry has replaced many metallic materials with lighter composite materials.

[0005] The resin that is bonded to the fiber reinforcements during the manufacturing process, particularly by injection or infusion, can be a thermosetting resin, such as epoxy (also called epoxy resin). The major drawback of these resins is their brittleness, resulting in low impact resistance for the composite parts produced. Therefore, prior art has proposed bonding the fiber reinforcement layers to porous thermoplastic polymer layers, and in particular to a non-woven fabric (also called a web) of thermoplastic fibers. Such solutions are proposed in particular in the following documents: EP 1125728, WO 2006 / 096170 A1, US 6,828,016, US 2010 / 003881, WO 00 / 58083, WO 2007 / 015706, WO 2006 / 121961, US 6,503,856, US 2008 / 7435693, WO 2010 / 046609, WO 2010 / 061114, EP 2 547 816, US 2008 / 0289743, US 2007 / 8361262, US 2011 / 9371604 and WO 2011 / 048340.

[0006] Multiaxial reinforcements, commonly known as non-crimp fabrics (NCFs), are also perfectly suited to direct manufacturing processes. Such multiaxial reinforcements, consisting of a stack of several unidirectional layers of reinforcing fibers (in particular, carbon, glass, or aramid) arranged in various orientations and stitched together, are described in applications EP 2 547 816 and WO 2010 / 067003. Most often, here again, porous polymer layers are inserted within the NCFs to improve the mechanical properties of the resulting composite parts.

[0007] These solutions, however, have some drawbacks. Indeed, these thermoplastic porous layers typically have a high melting point, often exceeding 150°C, which makes manufacturing these reinforcing materials expensive. Furthermore, the thermoplastic material constituting the porous layer can interact with the thermosetting resin injected during the production of composite parts, a reaction that is even more pronounced when the melting point of the thermoplastic material in the porous layer is low.

[0008] Most importantly, these porous thermoplastic layers are often fusible within the resin during the curing of the composite part. Consequently, these porous thermoplastic layers can alter the local stoichiometry of the thermosetting resin and can spread into the fibrous reinforcements during their impregnation with the thermosetting resin, which is undesirable as it leads to a degradation of the temperature resistance properties of the resulting parts.Thus, it is necessary to find a suitable curing cycle (defined as the rate of temperature rise to the curing temperature of the part and the holding time at the curing temperature) to allow the resin to gel at a temperature lower or higher than the melting temperature of the thermoplastic porous layers, depending on whether one wishes to keep the thermoplastic porous layer intact or alter it, resulting in different final properties of the part obtained.

[0009] Finally, another disadvantage of the thermoplastic porous layers proposed in the prior art is the sensitivity of the thermoplastics used to prolonged exposure to temperature.

[0010] To address these drawbacks, other solutions have been proposed in the prior art: in order to perform the shaping step of the fibrous reinforcement at a lower cost and in less time, the applicant proposed using an epoxy powder such as that used for the fabric developed under reference Hexcel Primetex 43098 S 1020 S E01 1F, instead of a porous thermoplastic layer. Such a thermosetting layer, obtained by depositing an epoxy powder with a softening temperature of around 100°C, allows for the faster and less expensive production of composite parts, particularly at a lower temperature, since low-temperature preforming can be performed.However, such a technique poses practical problems due to the use of powder which tends to clog the deposit heads of the automated deposit devices used and above all does not allow to obtain satisfactory properties in terms of mechanical resistance.

[0011] The applicant also proposed, in its patent application WO 2019 / 102136, to combine the fibrous reinforcement layers with partially irradiation-crosslinked thermoplastic polymer porous layers, in order to maintain the beneficial effects on mechanical performance observed when using reinforcement materials comprising a thermoplastic porous layer. In particular, due to its partially crosslinked portion, the porous layer will only be partially fusible, or even completely infusible, in the thermosetting resin, thus preventing alteration of its temperature and humidity resistance properties.Furthermore, the use of such partially crosslinked thermoplastic polymeric porous layers under irradiation offers the possibility of manufacturing the reinforcing material, and also shaping it during the production of composite parts, at temperatures below 130°C, preferably below 120°C. However, implementing an irradiation process that allows for partial crosslinking of the thermoplastic material lengthens the overall process and increases its costs.

[0012] The present invention aims to provide new reinforcement materials for the production of composite parts by direct process, of the RTM type in particular, which make it possible to achieve satisfactory mechanical performance, in particular required by the aerospace and aeronautical industry and good resistance to temperature stresses, without the technical constraints posed by the previous solutions previously proposed in application WO 2019 / 102136. Object of the invention

[0013] The invention relates to a reinforcement material comprising at least one fibrous reinforcement associated on at least one of its faces with a thermoplastic porous layer, said thermoplastic porous layer(s) representing at most 10% of the total mass of the reinforcement material, preferably from 0.5 to 10% of the total mass of the reinforcement material, and preferably from 2 to 6% of the total mass of the reinforcement material, wherein said thermoplastic porous layer or each of said thermoplastic porous layers present comprises a so-called reactive thermoplastic polymer or is made up of one or more reactive thermoplastic polymers, a reactive thermoplastic polymer having -NH2 functions in an amount greater than 0.15 meq / g of reactive thermoplastic polymer and / or having -COOH functions in an amount greater than 0.20 meq / g of reactive thermoplastic polymer.

[0014] Within the framework of the invention, due to the reactive functions -NH2 and COOH present in sufficient quantity on the reactive thermoplastic polymer of the porous layer present in the reinforcing material, the latter will be able to react in a controlled manner with epoxy resins during baking, which will allow to maintain a certain integrity of the thermoplastic layer, and thus makes it possible to reduce the sensitivity to exposure in temperature, as well as to improve the temperature properties for materials in the aerospace industry.

[0015] Advantageously, in the reinforcing material according to the invention, said reactive thermoplastic polymer carries -NH2 functions in an amount greater than 0.20 meq / g of reactive thermoplastic polymer, preferably in the range of 0.20 to 1 meq / g of reactive thermoplastic polymer and preferably in the range of 0.20 to 0.95 meq / g of reactive thermoplastic polymer, and / or carries -COOH functions in an amount greater than 0.20 meq / g of reactive thermoplastic polymer, preferably in the range of 0.20 to 1 meq / g of reactive thermoplastic polymer and preferably in the range of 0.20 to 0.95 meq / g of reactive thermoplastic polymer.

[0016] According to preferred embodiments, said reactive thermoplastic polymer of said or said thermoplastic porous layer(s) present within the reinforcing material has a melting temperature below 170°C, or even below 150°C and preferably belonging to the range of 100 to 140°C, and preferably to the range of 100 to 130°C.

[0017] Indeed, the reaction of the thermoplastic polymer in the porous layer with the injected or infused resin allows for the use of a porous layer with a low melting point. This enables the use of lower temperatures during manufacturing and shaping the reinforcing material, resulting in cost and time savings. Another advantage is that the melting point of the reactive thermoplastic polymer in the porous layer can be below 170°C, or even 150°C or lower. This allows all the manufacturing process steps prior to adding the resin needed to complete the part (from preparing the dry material to its deposition and preforming) to be carried out at a temperature below 170°C, and even better, below 150°C or lower.Thus, such porous layers comprising a reactive thermoplastic polymer with a lower melting point will allow the manufacture of the reinforcement material combining porous layer(s) and fibrous reinforcement(s) at a temperature compatible with automated manufacturing processes, including fiber placement and hot forming of flat-deposited preforms.

[0018] The present invention therefore has as a secondary objective the combination of the beneficial effects of the use of a thermoplastic porous layer on impact resistance performance, while having the possibility of carrying out all the steps of the manufacturing process prior to the infusion or injection of the resin, at temperatures below 170°C, or even below 150°C or 140°C, these temperatures being in some cases even in the range of 100 to 130°C, or even ranging from 80 to 140 or 130°C.

[0019] In a particularly preferred manner within the framework of the invention, in the reinforcing material, the reactive thermoplastic polymer is a polyamide or a copolyamide bearing said -NH2 and / or -COOH functions.

[0020] In particular, the said thermoplastic porous layer(s) present contain -NH2 functions in quantities greater than 0.15 meq / g of porous layer and / or -COOH functions in quantities greater than 0.20 meq / g of porous layer.

[0021] According to particular embodiments, the reactive thermoplastic polymer has an average number molecular mass of Mn greater than 4000 g / mol.

[0022] In the reinforcing materials according to the invention, the fibrous reinforcement can take different forms. According to some embodiments, the fibrous reinforcement is a unidirectional web of reinforcing yarns, a fabric of reinforcing yarns, or a stack of unidirectional webs of reinforcing yarns joined together by stitching or any other physical means, in particular needle punching.

[0023] The fibrous reinforcement can, in particular, be made of glass fibers, aramid fibers, or, preferably, carbon fibers.

[0024] According to certain embodiments, a reinforcement material according to the invention consists of a unidirectional web of reinforcing yarns corresponding to the fibrous reinforcement, associated on at least one of its faces with a thermoplastic porous layer as defined within the scope of the invention, preferably said fibrous reinforcement material consisting of a unidirectional web of reinforcing yarns corresponding to the fibrous reinforcement, associated on each of its faces with a thermoplastic porous layer as defined within the scope of the invention and the thermoplastic porous layers present on each of the faces of the unidirectional web of reinforcing yarns being identical.

[0025] The said thermoplastic porous layer(s) of the reinforcing materials according to the invention may have a hot-sticky character and the association of the fibrous reinforcement and the said porous layer was able to be achieved thanks to the hot-sticky character of the said thermoplastic porous layer.

[0026] According to certain embodiments, a reinforcing material according to the invention consists of a stack of unidirectional layers of reinforcing yarns, acting as fibrous reinforcements, oriented in different directions, with at least one thermoplastic porous layer as defined in the context of the invention, interposed between two unidirectional layers of reinforcing yarns and / or on the surface of the stack. Such a stack may consist of a superposition of layers corresponding to a sequence (CP / R)n (CP)m or (CP / R / CP)n, where CP designates a thermoplastic porous layer as defined in the context of the invention, R a unidirectional layer, n an integer greater than or equal to 1, and m equal to 0 or 1. In such stacks, the joining of the unidirectional layers of reinforcing yarns to each other, or even their joining to the at least one thermoplastic porous layer, may be achieved by stitching, knitting, or needle punching.

[0027] In the reinforcing materials according to the invention, the thermoplastic porous layer(s) present is / are, in particular, a porous film, a grid, a powder deposit, a fabric or, preferably, a non-woven or veil.

[0028] The invention also relates to a method for preparing a reinforcing material according to the invention, characterized in that it comprises the following successive steps: a1) have a fibrous reinforcement, a2) have at least one porous thermoplastic layer comprising a so-called reactive thermoplastic polymer, or consisting of one or more reactive thermoplastic polymers, a reactive thermoplastic polymer having -NH2 functions in a quantity greater than 0.15 meq / g of reactive thermoplastic polymer and / or having -COOH functions in a quantity greater than 0.20 meq / g of reactive thermoplastic polymer, a3) proceed to the association of the fibrous reinforcement and at least one porous thermoplastic layer.

[0029] In such a preparation process, the combination of step a3) is advantageously obtained by applying at least one thermoplastic porous layer to the fibrous reinforcement, said application being accompanied or followed by heating said reactive thermoplastic polymer causing it to soften or melt, and then followed by cooling, said heating preferably being carried out at a temperature below 170°C, or even at 150°C and preferably belonging to the range of 80 to 140°C, in particular 100 to 140°C, and preferably to the range of 80 to 130°C, in particular 100 to 130°C. Of course, the thermoplastic polymer(s) of the thermoplastic porous layer are chosen so as to obtain their softening or melting at such a temperature.

[0030] The invention also relates to a preform made up, at least in part, of one or more reinforcing materials according to the invention.

[0031] Another object of the invention relates to a method of manufacturing a composite part from at least one reinforcing material according to the invention, in which a thermosetting epoxy resin is injected or infused within said reinforcing material according to the invention, a stack of several reinforcing materials according to the invention, or a preform according to the invention.

[0032] Advantageously, the manufacturing process of a composite part according to the invention includes, once the thermosetting epoxy resin has been injected or infused into said reinforcing material or said stack, a heat treatment step, comprising heating to a temperature Ta, leading to the crosslinking of the epoxy resin and the consolidation of the composite part, during which the epoxy resin reacts with at least some of the -NH2 and / or -COOH functions present on the reactive thermoplastic polymer of the thermoplastic porous layer(s).

[0033] In particular, the gelation of the epoxy resin occurs during the heat treatment stage and the -NH2 and / or -COOH functions react with said resin, before the gelation of the latter.

[0034] According to a first embodiment of the manufacturing process for a composite part according to the invention, the temperature Ta is higher than the melting temperature of the reactive thermoplastic polymer of at least one porous thermoplastic layer. In particular, heating to the temperature Ta is carried out during the heat treatment step for 5 minutes to 2 hours. Most often, the heat treatment step includes a heating phase, in particular at a rate of 0.1 to 10°C / minute, up to the temperature Ta. Preferably, the viscosity of the epoxy thermosetting resin increases between the melting of the reactive thermoplastic polymer of at least one porous thermoplastic layer and the initiation of crosslinking of the epoxy thermosetting resin.More rigorously, one could say that the viscosity which is increased is that of the system resulting from the reaction between the reactive polymer of the thermoplastic porous layer and the epoxy resin.

[0035] According to the first implementation variant, during the heat treatment step, the epoxy thermosetting resin gels earlier than if it were subjected to heat treatment alone. Specifically, when heated to temperature Ta, the epoxy thermosetting resin gels after a heating time of 5 to 60 minutes.

[0036] According to the first variant of the manufacturing process of a composite part according to the invention where the temperature Ta is greater than the melting temperature of said reactive thermoplastic polymer of said at least one thermoplastic porous layer, the thermosetting resin preferably has a glass transition temperature Tg greater than 150°C.

[0037] According to a second embodiment of the manufacturing process for a composite part according to the invention, the temperature Ta is lower than the melting temperature of the reactive thermoplastic polymer of the thermoplastic porous layer, and heating is carried out to the temperature Ta. In particular, heating to the temperature Ta for 5 minutes to 5 hours is performed during the heat treatment step. Preferably, the gelation of the epoxy thermosetting resin occurs earlier than if the resin alone were subjected to the heat treatment step. Again, generally, the heat treatment step includes a heating phase, in particular at a rate of 0.1 to 10°C / minute, up to the temperature Ta.

[0038] According to the second variant of the manufacturing process for a composite part according to the invention, where the temperature Ta is lower than the melting temperature of said reactive thermoplastic polymer of said at least one porous thermoplastic layer, the thermosetting resin preferably has a glass transition temperature Tg of at least 100°C, and advantageously in the range of 100 to 150°C.

[0039] Advantageously also, according to the second variant of the manufacturing process of a composite part according to the invention where the temperature Ta is lower than the melting temperature of said reactive thermoplastic polymer of said at least one porous thermoplastic layer, said reactive thermoplastic polymer has a melting temperature greater than 120°C.

[0040] Regardless of the variant of implementation of the manufacturing process of a composite part according to the invention, the temperature Ta belongs to the range from 120 to 220°C, preferably belongs to the range from 160 to 220°C, preferably to the range from 170 to 190°C, and is typically equal to 180°C.

[0041] Advantageously, in the manufacturing processes of a composite part according to the invention, the thermosetting epoxy resin has a viscosity of less than 1000 mPa.s at a temperature of 90°C.

[0042] Furthermore, the manufacturing processes for a composite part according to the invention may include, prior to the infusion or injection of said thermosetting epoxy resin, a deposition or shaping of said reinforcing material(s), which preferably uses the hot stickiness of said at least one thermoplastic porous layer present in said reinforcing material(s) and employs heating, preferably carried out at a temperature below 170°C, or even at 150°C and preferably belonging to the range from 100 to 140°C, and preferably to the range from 100 to 130°C.

[0043] The invention also relates to composite parts obtained by a manufacturing process as defined within the scope of the invention.

[0044] The invention relates to composite parts comprising a thermosetting epoxy matrix in which is included at least one reinforcing material comprising at least one fibrous reinforcement associated on at least one of its faces with a thermoplastic porous layer, said thermoplastic porous layer(s) representing at most 10% of the total mass of the reinforcing material, preferably from 0.5 to 10% of the total mass of the reinforcing material, and preferably from 2 to 6% of the total mass of the reinforcing material. In said composite parts, there are covalent bonds between the thermosetting epoxy matrix and the thermoplastic polymer present within the thermoplastic porous layer(s), said covalent bonds resulting from the reaction of -NH2 and / or -COOH groups present on said thermoplastic polymer and the epoxy resin. Definitions

[0045] A "porous layer" is defined as a permeable layer that allows a liquid, such as a resin, to pass through the material when injected or infused during the formation of a preform or composite part. Specifically, the openness factor of such a layer is in the range of 30 to 99%, preferably in the range of 40 to 70%. This openness factor, a standard parameter for characterizing such a porous layer, can be determined using any technique known to those skilled in the art, including the method described in application WO 2011 / 086266. Examples of porous layers include porous films, grids made by interlacing threads, layers obtained by powder deposition, fabrics, and nonwovens.However, in the context of the invention, whatever the embodiment described, it is preferable to use a porous layer in the form of a non-woven fabric, also called a veil, which allows for the production of composite parts with particularly satisfactory mechanical properties.

[0046] The porous layer is called thermoplastic because it contains a thermoplastic polymer and is advantageously composed essentially or solely of a thermoplastic polymer or a mixture of thermoplastic polymers. When the porous layer comprises several polymers, these may be present in a mixture within the layer, particularly within a porous film, a powder, or fibers forming the porous layer. It is also possible to use fibers having a core and a sheath around the core to form the porous layer, the core and the sheath being made of different polymers, and in particular one or more reactive thermoplastic polymers defined within the scope of the invention forming the sheath.The porous layer may also include a thermoplastic binder made of one or more reactive thermoplastic polymers as defined in the invention, in particular those with a lower melting point than the rest of the polymer(s) forming the porous layer. The porous layer is said to consist essentially of a thermoplastic polymer or a mixture of such polymers if said polymer or mixture represents at least 90% by mass, and preferably at least 95% by mass, of the mass of the thermoplastic porous layer. In this description, the thermoplastic porous layer may be simply referred to as the "porous layer" for the sake of simplicity.In particular, the porous layer may consist essentially or solely of a reactive thermoplastic polymer, notably selected from polyesters, copolyesters, polyamide-imides, polyethersulfones, polyimides, polyetherketones, polymethyl methacrylates, aromatic polyethers, polyamides and copolyamides, which carry -NH2 functions in quantities greater than 0.15 meq / g of reactive thermoplastic polymer and / or -COOH functions in quantities greater than 0.20 meq / g of reactive thermoplastic polymer, or a mixture of such polymers.Such polymers may therefore comprise either only -NH2 functions in quantities greater than 0.15 meq / g of reactive thermoplastic polymer, or only -COOH functions in quantities greater than 0.20 meq / g of reactive thermoplastic polymer, or -NH2 functions in quantities greater than 0.15 meq / g of reactive thermoplastic polymer and -COOH functions in quantities greater than 0.20 meq / g of reactive thermoplastic polymer.

[0047] Within the framework of the invention, when referring to meq / g of reactive thermoplastic polymer, the mass of reactive thermoplastic polymer includes the reactive functions present on said polymer.

[0048] Within the framework of the invention, for the sake of simplicity, a reactive thermoplastic polymer, in particular chosen from polyesters, copolyesters, polyamide-imides, polyethersulfones, polyimides, polyetherketones, polymethyl methacrylates, aromatic polyethers, polyamides and copolyamides, which carry -NH2 functions in quantities greater than 0.15 meq / g of reactive thermoplastic polymer and / or -COOH functions in quantities greater than 0.20 meq / g of reactive thermoplastic polymer, may simply be called a reactive thermoplastic polymer.Thus, the aforementioned reactive thermoplastic polymers can either carry -NH2 functions in quantities greater than 0.15 meq / g of reactive thermoplastic polymer, or carry -COOH functions in quantities greater than 0.20 meq / g of reactive thermoplastic polymer, or carry both -NH2 functions in quantities greater than 0.15 meq / g of reactive thermoplastic polymer and -COOH functions in quantities greater than 0.20 meq / g of reactive thermoplastic polymer.In the reactive thermoplastic polymers used in the invention, -NH2 and / or -COOH groups, which can be described as free or reactive groups, are present on the thermoplastic polymer in sufficient quantities to obtain covalent reactions with the epoxy resin used in the production of a composite part. This is done so as to maintain the integrity, or a certain degree of integrity, of the porous thermoplastic layer, or at least limit its mobility in the resin infused or injected during the subsequent production of a composite part. Thus, there are no adverse effects on the mechanical properties of the resulting composite part.

[0049] In particular, a reactive thermoplastic polymer used in the context of the invention comprises free -COOH functions, in an amount greater than 0.20 meq / g of reactive thermoplastic polymer, in particular in an amount greater than or equal to 0.22; 0.25; 0.30 or 0.40 meq / g of reactive thermoplastic polymer; preferably in the range of 0.20 to 1 meq / g of reactive thermoplastic polymer and preferably in the range of 0.20 to 0.95 meq / g of reactive thermoplastic polymer, in particular in the range of 0.20 to 0.60 meq / g of reactive thermoplastic polymer, in the range of 0.20 to 0.50 meq / g of reactive thermoplastic polymer, or, even more preferably, in the range of 0.22 to 0.46 meq / g of reactive thermoplastic polymer.In particular, a reactive thermoplastic polymer used in the context of the invention comprises free -NH2 functions, in an amount greater than 0.20 meq / g of reactive thermoplastic polymer, in particular in an amount greater than or equal to 0.25; 0.30 or 0.34 meq / g of reactive thermoplastic polymer; preferably in the range of 0.20 to 1 meq / g of reactive thermoplastic polymer and preferably in the range of 0.20 to 0.95 meq / g, in particular in the range of 0.20 to 0.60 meq / g of reactive thermoplastic polymer; in the range of 0.30 to 0.50 meq / g of reactive thermoplastic polymer, in the range of 0.30 to 0.40 meq / g of reactive thermoplastic polymer, or, even more preferably, in the range of 0.32 to 0.36 meq / g of reactive thermoplastic polymer. The said quantities of -COOH or -NH2 functions can be present alone or together, according to all possible combinations, on a reactive thermoplastic polymer.

[0050] It is also possible for the porous layer to consist essentially or solely of one or more reactive thermoplastic polymers, mixed with another, so-called additional, thermoplastic polymer. In this case, preferably, the mass of the reactive thermoplastic polymer(s) represents at least 10%, and preferably at least 70%, of the total mass of the porous thermoplastic layer. Examples of polymers other than reactive thermoplastic polymers include polyamides, copolyamides, polyesters, copolyesters, polyamide-imides, polyethersulfones, polyimides, polyetherketones, polymethyl methacrylates, and aromatic polyethers (not containing -NH2 or -COOH groups, or containing such groups in smaller quantities than those envisaged in the context of the invention)...

[0051] The said additional thermoplastic polymer may have a melting point below 170°C, or even below 150°C, and preferably within the range of 100 to 140°C, and preferably within the range of 100 to 130°C. In such cases, advantageously, the reactive porous layer is made up of at least 70% by mass, preferably at least 80% by mass, and preferably at least 90% by mass of one or more reactive thermoplastic polymer(s) as defined within the scope of the invention.

[0052] It is also possible to use fibers having a core made of one or more additional thermoplastic polymers with a melting point below 170°C, or even 150°C, and preferably within the range of 100 to 140°C, and more preferably within the range of 100 to 130°C. This core is surrounded by a sheath made of one or more reactive thermoplastic polymers defined within the scope of the invention. This additional thermoplastic polymer may also have a melting point above 170°C, or even 180°C, and preferably within the range of 180 to 220°C.In such cases, advantageously, the reactive thermoplastic polymer(s) as defined in the context of the invention may be present within the porous layer to serve as a binder, in particular to bind the thermoplastic porous layer to the fibrous reinforcement, and the reactive thermoplastic polymer(s) as defined in the context of the invention may be present in smaller quantities within the porous layer, in particular representing 10 to 30% of the mass of the porous layer.

[0053] In the context of the invention, the polymeric material constituting the porous layer is preferably a reactive thermoplastic polymer or a mixture of such reactive thermoplastic polymers and not a mixture of one or more of these polymers with another thermoplastic polymer.

[0054] Within the framework of the invention, and regardless of the embodiment variant, the reactive thermoplastic polymer is preferably a polyamide or a copolyamide, carrying -NH2 functions in quantities greater than 0.15 meq / g of reactive thermoplastic polymer and / or -COOH functions in quantities greater than 0.20 meq / g of reactive thermoplastic polymer, and in particular carrying -NH2 and / or -COOH functions in the quantities previously specified in the more general description of reactive thermoplastic polymers.

[0055] The reactive thermoplastic polymer used in the invention carries a sufficient number of reactive functional groups to enable it to react with epoxy thermosetting resins, which are commonly used in the production of composite parts. As will be shown in the examples, this reaction will impart particularly advantageous characteristics to the resulting composite parts, notably improving their resistance to temperature and humidity, while maintaining satisfactory mechanical properties, which are important for composite parts intended for the aeronautical and aerospace industries.

[0056] The amount of reactive -COOH or -NH2 groups present can be determined by potentiometric titration: the amount of -COOH groups is determined by acid-base titration of the porous layer with tetra-n-butylammonium hydroxide ((C4H9)4N+OH-) in alcoholic solution, while the amount of -NH2 groups is determined by titration with perchloric acid (HClO4) in acetic acid, as detailed in the examples. The results are expressed in meq / g (milliequivalents per gram).

[0057] The reactive thermoplastic polymer used in the invention is advantageously a polyamide or copolyamide. In particular, the reactive thermoplastic polymer is in the form of a branched polyamide or copolyamide bearing an -NH2 or -COOH functional group at the end of the branch chains, so as to achieve the quantities of functional groups targeted in the invention. It may be a polyamide 6 (polycaprolactam), 6.6 (nylon), 6.10 (polyhexamethylene sebaçamide), 6.12 (polyhexamethylene dodecanediamide), 11 (polyundecanamide), or 12 (polylauroamide), among others. Advantageously, the reactive thermoplastic polymer belongs to the copolyamide family, and in particular to copolymers of caprolactam and / or lauryllactam and / or hexamethylenediamine and adipic acid.

[0058] Such polymers are, in particular, marketed by ARKEMA France, under the references Platamid ®< HX2598 and H2651, by Evonik Industries AG (Germany), by Solvay (Belgium) or by EMS-Grivory (Switzerland).

[0059] Typically, as described for example in applications EP3197974, FR2883878 and US2010 / 0032629, polyamides or copolyamides can be obtained from several raw materials: lactams, aminocarboxylic acids, diamines or triamines, dicarboxylic acids, etc. The production of a copolyamide requires the selection of at least two of these products. The quantities of diamines and diacids used allow for the modulation of the amine and acid functional groups present in the polyamide or copolyamide.

[0060] Examples of lactams include those with 3 to 12 carbon atoms on the main ring, which can be substituted. Examples include caprolactam, capryllactam, lauryllactam, and amylolactam.

[0061] Examples of aminocarboxylic acids include amino-undecanoic acid and aminododecanoic acid.

[0062] Examples of dicarboxylic acids include adipic acid, isophthalic acid, sebacic acid, dodecanedioic acid, therephthalic acid...

[0063] Examples of diamines include those with 6 to 12 carbon atoms, aryl diamines, and saturated cyclic diamines. Examples include hexamethylenediamine, tetramethylenediamine, octamethylenediamine, decamethylenediamine, and piperazine.

[0064] Examples of copolyamide chains include those of caprolactam and lauryl lactam (6 / 12), those of caprolactam, lauryl lactam and 11-amino undecanoic acid (6 / 11 / 12), those of caprolactam, adipic acid and hexamethylene diamine (6 / 66), those of caprolactam, lauryl lactam, adipic acid and hexamethylene diamine (6 / 12 / 66), those of caprolactam, lauryl lactam, 11-amino undecanoic acid, adipic acid and hexamethylene diamine (6 / 66 / 11 / 12).

[0065] In particular, appropriate amounts of acid such as adipic acid (for the introduction of -COOH functions) and / or amine such as hexamethylenediamine (for the introduction of amine functions) are used, in order to modulate and obtain the desired number of reactive functions.

[0066] More generally, and for all thermoplastic polymers, a preferred method for introducing amine (-NH2) or acid (-COOH) groups is plasma treatment. The implementation of such treatments is described in the following documents: "Grafting of Chemical Groups onto Polymers by Means of RF Plasma Treatments: a Technology for Biomedical Applications," P. Favia, R. d'Agostino, F. Palumbo, J. Phys. IV France 07 (1997) C4-199-C4-208; and "Plasma grafting - a method to obtain monofunctional surfaces," C. Oehr, M. Müller, B. Elkin, D. Hegemann, U. Vohrer, Surface and Coatings Technology Volumes 116-119, September 1999, Pages 25-35; US2021 / 0086226. or WO 2019 / 243631 ....

[0067] Thermoplastic polymers comprising the desired number of amine -NH2 and / or acid -COOH functions, or on which the desired number of amine and / or acid functions can be modulated or introduced by plasma treatment, in particular, are commercially available.

[0068] As regards polyesters or copolyesters, such polymers are marketed for example by the companies Evonik Industries AG (Germany), Eastmann Chemical Company (USA), Arkema (France), EMS-Grivory (Switzerland), Toyobo (Japan).

[0069] With regard to polyamide-imides, such polymers are marketed for example by the companies Solvay (Belgium), Toyobo (Japan), Mitsubishi Chemical (Switzerland).

[0070] With regard to polyethersulfones, such polymers are marketed for example by the companies BASF (Germany), Sumitomo Chemical (Japan), Ensinger Plastics (Germany).

[0071] With regard to polyimides, such polymers are marketed for example by the companies DuPont (USA), Evonik Industries AG (Germany), Huntsmann Corporation (USA).

[0072] With regard to polyetherketones, such polymers are marketed for example by the companies Arkema (France), Solvay (Belgium), Evonik Industries AG (Germany), Victrex (United Kingdom).

[0073] Finally, regarding polymethyl methacrylates, such polymers are marketed, for example, by the companies Evonik Industries AG (Germany) and Kuraray (Japan).

[0074] The reactive thermoplastic polymer of the porous layer can be an amorphous polymer, but is preferably a semi-crystalline polymer. Since semi-crystalline polymers have a glass transition temperature lower than their melting temperature, they can be softened more easily, facilitating their bonding to the fibrous reinforcement or facilitating the subsequent deposition and / or preforming of the reinforcement material according to the invention. Furthermore, semi-crystalline polymers possess, in particular, an organized molecular structure in which the chains are aligned, giving them superior mechanical properties compared to amorphous polymers, whose molecular structure is not organized.

[0075] When discussing the melting temperature of a polymer or a thermoplastic porous layer, it refers to the peak melting temperature measured by Differential Scanning Calorimetry (DSC) with a temperature rise of 10°C / min.

[0076] The term "fibrous reinforcement bonded on at least one face to a porous layer" means that the fibrous reinforcement is attached to at least one porous layer, which is applied to one of its faces. Such a bond is typically achieved by gluing, notably due to the porous layer's heat-adhesive properties, resulting from its thermoplastic nature. It is also possible, particularly in the case of a stack comprising several fibrous reinforcements and several porous layers, for this bond to be supplemented or replaced by a mechanical bond such as stitching, knitting, or any other physical means (needle pricking, etc.).

[0077] The reinforcing materials according to the invention can be described as "dry" because they are intended to be combined with a binder, in particular a thermosetting resin, for the manufacture of a composite part. Therefore, the mass of the porous layer(s) present in the reinforcing material according to the invention does not exceed 10% of the total mass of the reinforcing material, and preferably represents 0.5 to 10%, and more preferably 2 to 6%, of the total mass of the reinforcing material according to the invention.

[0078] More generally, the reinforcing materials according to the invention are so-called dry materials, meaning they are suitable for manufacturing composite parts in combination with a resin, particularly a thermosetting epoxy resin. A reinforcing material according to the invention comprises a polymer component representing at most 10% of the total mass of the reinforcing material, preferably from 0.5% to 10% of the total mass of the reinforcing material, and preferably from 2% to 6% of the total mass of the reinforcing material. This polymer component comprises, or even consists of, the thermoplastic porous layer(s) present in the reinforcing material according to the invention.

[0079] In particular, according to the invention, the thermoplastic porous layer(s) present in the reinforcing material is / are made up of one or more reactive thermoplastic polymer(s), in particular chosen from polyesters, copolyesters, polyamide-imides, polyethersulfones, polyimides, polyetherketones, polymethyl methacrylates, aromatic polyethers, polyamides and copolyamides as defined in the scope of the invention, and preferably of one or more reactive thermoplastic polymer(s) chosen from polyamides and copolyamides as defined in the scope of the invention.

[0080] The term "nonwoven," which can also be called "web," classically refers to a collection of continuous or short fibers arranged randomly. These nonwovens or webs can be produced, for example, by drylaid, wetlaid, or spunlaid processes, such as spunbond, meltblown, fiberized spray applicator, or solvent spinning (electrospinning, flashspinning, forcespinning), all well-known to those skilled in the art. In particular, the constituent fibers of the nonwoven can have an average diameter ranging from 0.5 to 70 µm, and preferably from 0.5 to 20 µm. Nonwovens can be composed of short fibers or, preferably, continuous fibers. In the case of a short fiber nonwoven, the fibers may have, for example, a length between 1 and 100 mm.Non-woven fabrics offer random and, preferably, isotropic coverage.

[0081] Advantageously, the nonwoven fabric(s) present in the reinforcing materials according to the invention has a surface mass in the range of 0.2 to 20 g / m². The thickness of a nonwoven fabric in the reinforcing materials according to the invention may vary depending on the method of bonding to the fibrous reinforcement. Preferably, the nonwoven fabric or each of the nonwoven fabrics present in the reinforcing materials according to the invention has a thickness of 0.5 to 50 microns after bonding to the fibrous reinforcement, preferably from 3 to 35 microns, when the bonding is achieved by applying heat and pressure, to utilize the hot-bonding properties of the nonwoven fabric. When the bonding is achieved by mechanical means, such as sewing, knitting, or needle punching, the thickness of the nonwoven fabric may exceed 50 microns, particularly in the range of 50 to 200 microns.The characteristics of these non-wovens can be determined according to the methods described in application WO 2010 / 046609.

[0082] The term "fibrous reinforcement" refers to a layer of reinforcing fibers, which may take the form of a fabric or a unidirectional sheet of reinforcing fibers. These reinforcing fibers are generally glass, carbon, aramid, or ceramic fibers, with carbon fibers being particularly preferred.

[0083] In this field, a "unidirectional reinforcing fiber web or layer" is typically understood to be a web composed exclusively or almost exclusively of reinforcing fibers or yarns laid in the same direction, so as to extend substantially parallel to one another. In the case of a web of reinforcing yarns, these extend along general directions of extension that are parallel or substantially parallel. In particular, according to a specific embodiment of the invention, the unidirectional web does not include any weft yarns interlacing the reinforcing yarns or fibers, nor any stitching intended to provide cohesion to the unidirectional web before its association with another layer, and in particular with a porous thermoplastic layer. This makes it possible, in particular, to avoid any waviness within the unidirectional web.A unidirectional web of reinforcing fibers can be made of a single yarn, although it is most often composed of several aligned yarns arranged side by side. The yarns are arranged to ensure total or near-total coverage over the entire surface of the web. In this case, within each of the layers constituting the intermediate material, the yarns are preferably arranged edge to edge, minimizing or even eliminating any gaps or overlaps.

[0084] In a unidirectional web, the reinforcing yarn(s) are preferably not bonded with a polymeric binder and are therefore described as dry; that is, they are neither impregnated, nor coated, nor bonded with any polymeric binder before being bonded to one or more porous thermoplastic layers. The reinforcing fibers are, however, most often characterized by a standard sizing percentage that can represent no more than 2% of their mass. This is particularly well-suited to the production of composite parts by resin diffusion using direct processes. In a unidirectional web, the reinforcing yarn(s) may be twisted yarns.

[0085] The constituent fibers of the fibrous reinforcements used in the invention are preferably continuous. The fibrous reinforcements are generally made up of several strands.

[0086] In particular, a carbon fiber consists of a set of filaments and generally comprises from 1,000 to 80,000 filaments, advantageously from 12,000 to 24,000 filaments. Particularly preferred, within the scope of the invention, carbon fibers of 1 to 24 K, for example, 3 K, 6 K, 12 K, or 24 K, and preferably 12 and 24 K, are used. For example, the carbon fibers present in the fibrous reinforcements used within the scope of the invention have a carbon content of 60 to 3800 Tex, and preferably 400 to 900 Tex.A fibrous reinforcement can be made with any type of carbon yarn, for example, High Strength (HR) yarns with a tensile modulus between 220 and 241 GPa and a tensile breaking strength between 3450 and 4830 MPa, Intermediate Modulus (IM) yarns with a tensile modulus between 290 and 297 GPa and a tensile breaking strength between 3450 and 6200 MPa and High Modulus (HM) yarns with a tensile modulus between 345 and 448 GPa and a tensile breaking strength between 3450 and 5520 Pa (according to the "ASM Handbook", ISBN 0-87170-703-9, ASM International 2001). In the case where the unidirectional reinforcement layer is made of carbon yarns, it may have a weight, in particular, in the range of 126g / m² to 500g / m², in particular from 126 to 280 g / m². Reinforcing material according to the invention

[0087] The invention can be adapted for different types of reinforcement materials: simple reinforcement materials comprising a single fibrous reinforcement intended to be stacked on top of each other, or more complex reinforcement materials comprising several superimposed fibrous reinforcements, which can be used alone or also in the form of stacking.

[0088] In particular, as an example of simple reinforcing materials, one can cite those consisting of a unidirectional web of reinforcing fibers corresponding to the fibrous reinforcement, associated on at least one of its faces with a porous thermoplastic layer comprising or consisting of a reactive thermoplastic polymer as provided for in the invention. So as to have a symmetrical material 1 as illustrated figure 1The fibrous reinforcement, and in particular the unidirectional web 2 of reinforcing fibers 3, is associated on each of its faces with a thermoplastic porous layer 4, 5 comprising or consisting of one or more reactive thermoplastic polymers as provided for in the invention, and the porous layers present on each face of the unidirectional web of reinforcing fibers are preferably identical. In the invention, the thermoplastic porous layer comprising or consisting of one or more reactive thermoplastic polymers exhibits a hot-sticky characteristic, and the association of the fibrous reinforcement and the thermoplastic porous layer is advantageously achieved thanks to the hot-sticky character of the porous layer. This stickiness results from the thermoplastic nature of the porous layer.Of course, it may also be possible to replace, or even supplement, this association using the hot stickiness of the porous layer, by sewing or knitting, or by any other means of physical bonding (needling...).

[0089] The reinforcing material may also be in the form of a stack of such reinforcing materials, namely (CP / R / CP) n, where CP designates a thermoplastic porous layer comprising or consisting of one or more reactive thermoplastic polymers as defined in the context of the invention, and in particular a nonwoven fabric, and R a unidirectional web, with n being an integer greater than or equal to 1. Preferably, all the thermoplastic porous CP layers have the same basis weight, or even be identical, and / or all the fibrous reinforcements R have the same basis weight, or even be identical. It is also possible for the two outer CP layers of the stack to have a basis weight equal to twice the basis weight of the other CP layers, referred to as the inner layers.

[0090] As an example of more complex reinforcing materials, one can cite those consisting of a stack of unidirectional reinforcing fiber layers oriented in different directions, with at least one porous thermoplastic layer comprising or made of one or more reactive thermoplastic polymers as provided for in the invention, sandwiched between two unidirectional reinforcing fiber layers and / or on the surface of the stack. According to a first embodiment, such a material can consist of a stack corresponding to a sequence (CP / R) n or (CP / R) n / CP, where CP designates a porous thermoplastic layer comprising or made of a reactive thermoplastic polymer as defined in the invention, R a unidirectional layer as described in the invention, and n denoting an integer, preferably with all CP layers having the same basis weight, or even being identical.In particular, in such stacks, the R-fibrous reinforcements are unidirectional sheets of reinforcing fibers, especially carbon fibers, preferably of the same basis weight. Such materials are called NCFs (Non-Crimp Fabrics). Typically in the field of NCFs, the unidirectional sheets of reinforcing fibers are joined to each other and to the existing thermoplastic porous layer(s) by stitching or knitting. Of course, it may be possible to replace, or even supplement, this stitching or knitting by adhesion achieved through the hot-tackiness of the thermoplastic porous layer, or by any other physical bonding method (needle punching, etc.).

[0091] In particular, in the case of NCF, the reinforcing material according to the invention is composed of unidirectional plies extending along different orientations chosen from the angles 0°, 30°, 45°, 60°, 90°, 120°, 135°. All the unidirectional plies may have different orientations or only some of them.By way of example, the reinforcing material according to the invention may be produced in the following stacking arrangements: 0° / 90°, 90° / 0°, 45° / 135°, 135 / 45°, 90° / 0° / 90°, 0° / 90° / 0°, 135° / 45° / 135° / , 45° / 135° / 45°, 0° / 45° / 90°, 90° / 45° / 0°, 45° / 0° / 90°, 90° / 0° / 45°, 0° / 135° / 90°, 90° / 135° / 0°, 135° / 0° / 90°, 90° / 0° / 135°, 45° / 0° / 135°, 135° / 0° / 45°, 45° / 135° / 0, 0° / 135° / 45°, 45° / 135° / 90°, 90° / 135° / 45°, 135° / 45° / 0°, 0° / 45° / 135°, 135° / 45° / 90°, 90° / 45° / 135°, 60° / 0° / 120°, 120° / 0° / 60°, 30° / 0° / 150°, 150° / 0° / 30°, 135° / 0° / 45° / 90°, 90° / 45° / 0° / 135°, 45° / 135° / 0° / 90°, 90° / 0° / 135° / 45°, 0° / 45° / 135° / 90°, 90° / 135° / 45° / 90°, 90° / 135° / 0° / 45°, 45° / 0° / 135° / 90°, where 0° corresponds to the machine's direction of travel for producing the reinforcing material according to the invention. In the case of a sewn or knitted assembly, the general direction of the sewing or knitting threads will also generally correspond to 0°.The production of such multiaxials is well-established and employs conventional techniques, for example, those described in "Textile Structural Composites, Composite Materials Series Volume 3" by Tsu Wei Chou & Franck K. Ko, ISBN 0-444-42992-1, Elsevier Science Publishers BV, 1989, Chapter 5, paragraph 3.3, or in patent FR2761380, which describes a process and device for producing multiaxial fiber webs. In particular, the unidirectional webs can be formed beforehand, or deposited in a line, during the formation of the multiaxial. The joining of the different unidirectional webs by stitching or knitting can be achieved using stitches or knitting techniques extending along parallel lines. In particular, the stitching or knitting points are spaced, within the same line, according to a step, preferably identical, of 1 to 20 mm, preferably of 2 to 12 mm.Similarly, two consecutive lines of stitching or knitting are, for example, spaced 2 to 50 mm apart, preferably 5 to 15 mm. Preferably, all consecutive lines of stitching in a series of parallel lines will be spaced the same distance apart. Examples of materials constituting the stitching thread particularly suitable for the purposes of the invention include polyesters, copolyesters, polypropylenes (PP), polyethylenes (PE), polyphenylene sulfides (PPS), polyethylene naphthalates (PEN), liquid crystal polymers (LCP), polyketones, polyamides, crosslinkable thermoplastics, carbon, glass, basalt, silica, and mixtures thereof. Polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, polylactic acid and their copolymers are examples of polyesters that can be used.The yarn will, for example, have a count in the range of 5 to 150 dTex, notably less than 30 dTex, for example determined according to the EN ISO 2060 standard. For more details on constructions usable in NCF type materials, reference can be made to documents EP 2547816 or WO 2010 / 067003 in particular.

[0092] Regardless of the arrangement of the reinforcing materials according to the invention, according to particular embodiments, the thermoplastic porous layer(s) present comprise -NH2 functions in quantities greater than 0.15 meq / g of porous layer and / or -COOH functions in quantities greater than 0.20 meq / g of porous layer.In particular, the said thermoplastic porous layer(s) present comprise(s) free -COOH functions, in quantities greater than 0.20 meq / g of thermoplastic porous layer, in particular in quantities greater than or equal to 0.22; 0.25; 0.30 or 0.40 meq / g of thermoplastic porous layer; preferably in the range of 0.20 to 1 meq / g of thermoplastic porous layer and preferably in the range of 0.20 to 0.95 meq / g of thermoplastic porous layer, in particular in the range of 0.20 to 0.60 meq / g of thermoplastic porous layer, in the range of 0.20 to 0.50 meq / g of thermoplastic porous layer, or, even more preferably, in the range of 0.22 to 0.46 meq / g of thermoplastic porous layer.In particular, the said thermoplastic porous layer(s) present comprise free -NH2 functions, in quantities greater than 0.20 meq / g of thermoplastic porous layer, in particular in quantities greater than or equal to 0.25; 0.30 or 0.34 meq / g of thermoplastic porous layer; preferably in the range of 0.20 to 1 meq / g of thermoplastic porous layer and preferably in the range of 0.20 to 0.95 meq / g of thermoplastic porous layer, in particular in the range of 0.20 to 0.60 meq / g of thermoplastic porous layer; in the range of 0.30 to 0.50 meq / g of thermoplastic porous layer, in the range of 0.30 to 0.40 meq / g of thermoplastic porous layer, or, even more preferably, in the range of 0.32 to 0.36 meq / g of thermoplastic porous layer.The said quantities of -COOH or -NH2 functions can be present alone or together, according to all possible combinations, on a thermoplastic porous layer. Method for preparing a reinforcing material according to the invention

[0093] Within the framework of the invention, a reinforcing material according to the invention can be prepared by implementing the following successive steps: a1) have a fibrous reinforcement, a2) have at least one porous thermoplastic layer comprising or made of a reactive thermoplastic polymer as defined in the context of the invention, a3) proceed to combine the fibrous reinforcement and at least one porous thermoplastic layer.

[0094] In particular, step a3) can be achieved by applying at least one thermoplastic porous layer to the fibrous reinforcement, said application most often being accompanied or followed by heating causing the reactive thermoplastic polymer to soften or melt said at least one thermoplastic porous layer, and then followed by cooling. In particular, such an association can be achieved at a temperature of 22 to 200°C, preferably 50 to 180°C, and is carried out under ambient air, and by applying the thermoplastic porous layer to the fibrous reinforcement, for example, by applying pressure to the latter.Advantageously, the reactive thermoplastic polymer of the thermoplastic porous layer(s) present within the reinforcing material has a melting temperature below 170°C, or even below 150°C, and preferably within the range of 100 to 140°C, and preferably within the range of 100 to 130°C. In particular, the thermoplastic porous layer(s) present has a melting temperature below 170°C, or even below 150°C, and preferably within the range of 100 to 140°C, and preferably within the range of 100 to 130°C.With such reactive thermoplastic polymers, the association of the thermoplastic porous layer and the fibrous reinforcement using the hot stickiness of the thermoplastic porous layer can be achieved by heating to a temperature below 170°C, or even 150°C and preferably belonging to the range of 100 to 140°C, and preferably to the range of 100 to 130°C.

[0095] Step a3) can also be carried out by sewing, knitting, needle punching or any other suitable means allowing the fibrous reinforcement and the thermoplastic porous layer to be joined together.

[0096] In particular, when the fibrous reinforcement according to the invention corresponds to a stack of unidirectional sheets of reinforcing yarns linked together by stitching or any other physical means, in particular by needle punching, step a1) consists of having several fibrous reinforcements which are unidirectional sheets of reinforcing yarns, step a3) during which the association of said fibrous reinforcements and at least one thermoplastic porous layer is carried out includes the constitution of a stack of unidirectional sheets of reinforcing yarns and said at least one thermoplastic porous layer and the realization of stacking of unidirectional sheets of reinforcing yarns linked together by stitching or any other physical means, in particular by needle punching.Step a” may include both an association achieved by sewing, knitting, needle punching or any other suitable means enabling the fibrous reinforcement and the thermoplastic porous layer to be joined together and an association by application of at least one thermoplastic porous layer to at least one of the unidirectional sheets of reinforcing yarns, said application being most often accompanied or followed by heating causing the softening or melting of said reactive thermoplastic polymer of said at least one thermoplastic porous layer, said heating being followed by cooling.

[0097] In the case of more complex materials comprising at least one porous thermoplastic layer comprising or consisting of one or more reactive thermoplastic polymers as provided for in the context of the invention, between two fibrous reinforcements, and in particular, in the case of NCF, the process shall include the creation of a stacking of the different layers, and in particular according to a sequence (CP / R) n or (CP / R) n / CP, as previously defined, with n greater than 1 and the association of the different layers together may be completed or carried out by a sewing, knitting, needle-punching or other mechanical assembly operation.

[0098] Of course, whatever the preparation process used, the porous layer and the reinforcing material will be chosen so that in the end, the thermoplastic porous layer(s) represent(s) at most 10% of the total mass of the reinforcing material, preferably 0.5 to 10% of the total mass of the reinforcing material, and preferably 2 to 6% of the total mass of the reinforcing material obtained.

[0099] The characteristics of the process are related to the characteristics of the reinforcing materials as described in the context of the invention. Use and method employing a reinforcing material according to the invention for the manufacture of a preform or composite part

[0100] The reinforcement materials of the invention comprising a fibrous reinforcement associated on at least one of its faces with a porous thermoplastic layer comprising a reactive thermoplastic polymer as defined in the context of the invention, in particular selected from polyesters, copolyesters, polyamide-imides, polyethersulfones, polyimides, polyetherketones, polymethyl methacrylates, aromatic polyethers, polyamides and copolyamides, which carry -NH2 functions in quantities greater than 0.15 meq / g of reactive thermoplastic polymer and / or -COOH functions in quantities greater than 0.20 meq / g of reactive thermoplastic polymer, referred to as reactive thermoplastic polymer, are perfectly suited, for the production of a preform or a composite part, in association with a thermosetting epoxy resin.

[0101] The resin diffused or injected into the reinforcing material or a stack of reinforcing materials according to the invention is a thermosetting epoxy resin. Examples of epoxy resins include polyglycidyl derivatives of aromatic diamines, primary monoaromatic amines, aminophenols, and polycarboxylic acids. Polyglycidyl ethers of bisphenols such as bisphenol A, bisphenol F, bisphenol S, and bisphenol K are also examples. Numerous epoxy resins suitable for manufacturing composite parts by direct casting are commercially available, notably from Solvay, Hexion, and Hexcel Composites. Examples include RTM6 and HF620 resins from Hexcel Composites and EP2400 and EP2410 resins from Solvay. These resins are composed of a mixture of epoxy resins, combined with a mixture of one or more hardening agents and possibly one or more shock modifier(s).

[0102] Other commercially available epoxy resins include N,N,N',N'-tetraglycidyl diamino diphenylmethane (Huntsman's MY9663, MY720, MY721), p-aminophenol triglycidic ethers (such as Huntsman's MY0510), m-aminophenol triglycidic ethers (such as Huntsman's MY0600), and bifunctional epoxides (such as Huntsman's GY285 and CY184).

[0103] Epoxy thermosetting resins can be tetra-, tri-, or bifunctional, with an increasing number of epoxy functionalities naturally leading to higher crosslinking reaction kinetics. Such an epoxy thermosetting resin typically comprises one or more curing agents, well known to those skilled in the art for use with selected epoxy-type thermosetting polymers. Examples of preferred curing agents include cyanoguanidines, aromatic, aliphatic, and alicyclic amines, acid anhydrides, Lewis acids, substituted ureas, imidazoles, hydrazines, and silicones. An epoxy resin may also typically include a shock modifier or core-shell toughening agent.For example, one could cite Kaneka's (Japan) Kane Ace MX shock modifiers, or Arkema France's Clearstrength shock modifiers. The process according to the invention is of particular interest because the injected or infused resin is a thermosetting resin of the epoxy type. Indeed, epoxy resins have the ability to react with the -NH2 or -COOH groups present in sufficient quantities in the thermoplastic porous layers of the materials according to the invention. This reaction prevents the thermoplastic polymer of the porous layer(s) from spreading into the injected or infused resin and altering its properties, particularly its heat resistance.

[0104] Preferably, within the framework of the invention, an epoxy resin comprising a tetrafunctional epoxy, optionally mixed with a trifunctional epoxy, one or more hardening agents and one or more shock modifier(s) will be used.

[0105] Advantageously, the thermosetting epoxy resins used in the invention have a Tg of 100°C or more, or even greater than 150°C. The choice of the resin's Tg can be adapted by those skilled in the art, depending on the steps of the process implemented and whether they wish to carry out the heating at a temperature Ta lower or higher than the melting temperature of the reactive thermoplastic polymer.

[0106] The production of a composite part is typically carried out in a mold (open or closed). Before being introduced into the mold, the resin may be preheated. Before being infused or injected into the reinforcing material, the stack, or the preform, the resin may be preheated to a temperature of 60 to 90°C.

[0107] The injected or infused resin preferably has a viscosity of less than 1000 mPa·s at the temperature at which the resin is introduced into the mold. Preferably, the thermosetting resin used has a viscosity of less than 1000 mPa·s at a temperature of 90°C. Generally, during the manufacturing of composite parts, the infusion or injection temperature of a thermosetting resin into the mold most often varies from 90 to 180°C. Within the scope of this invention, the viscosity can be measured with a dynamic shear rheometer according to EN6043, with the difference that the strain is 4% instead of 10%. In particular, the measurement is performed with a 0.5 mm gap, a 4% strain control, and a frequency of 10 rad / s, with the heating rate for an isothermal process being 2°C / min.

[0108] In a conventional method for manufacturing a preform or composite part from at least one reinforcing material according to the invention, a thermosetting, thermoplastic resin, or a mixture of thermosetting and thermoplastic resins, and in particular an epoxy thermosetting resin, notably as defined within the scope of the invention, is injected or infused into said reinforcing material, or into a stack of several reinforcing materials, or into a preform made from said material. A preform is understood to be a reinforcing material, or a set of reinforcing materials, that has undergone a preliminary shaping operation before being placed in the mold or tooling used to produce the composite part.

[0109] For the production of composite parts, a stack or drape of reinforcing materials according to the invention (also called plies) is created. Conventionally, a reinforcing material according to the invention is cut to the desired dimensions for the production of the part, ply, stack, or preform to be created. In a stack, several materials or plies of reinforcing materials are piled one on top of the other.

[0110] A ply can be made of a single reinforcing material according to the invention, provided that the material is wide enough to produce the desired part and the part is relatively simple. However, more often, in the case of large or complex parts, a ply consists of several reinforcing materials according to the invention, arranged side by side to cover the entire surface area necessary to produce the desired part.

[0111] Within the scope of the invention, due to the thermoplastic nature of the porous layer present in the reinforcing material, prior to resin infusion or injection, a deposition or shaping process utilizing the hot-adhesive nature of at least one porous layer present in the reinforcing material can be implemented during the production of the preform or composite part. Advantageously, the manufacturing processes for a preform or composite part include a step of deposition or shaping of a material according to the invention, in which the porous layer is heated to a temperature resulting in at least partial melting of said reactive thermoplastic polymer of the porous layer(s) defined within the scope of the invention, and in particular to a temperature below 170°C, or even 150°C, and preferably within the range of 100 to 140°C, and more preferably within the range of 100 to 130°C.

[0112] The steps used to manufacture the composite part are quite standard for those skilled in the art. It is possible to create, as an intermediate step, a flat preform, or even a preform with a desired three-dimensional shape. In particular, the deposition of a reinforcing material according to the invention can be carried out continuously by applying pressure perpendicular to the deposited surface, in order to adhere it to that surface. Such processes, known by the abbreviations AFP (Automated Fiber Placement) or ATL (Automated Tape Lay-up), are, for example, described in documents WO 2014 / 076433 A1 and WO 2014 / 191667. Different strips of material according to the invention can be deposited side by side along parallel or non-parallel deposition paths, depending on the preform to be produced, so as to form a succession of layers deposited one on top of the other.Simultaneously with the deposition, the thermoplastic material of the porous layer is activated, i.e., softened, to utilize its hot-bonding properties. Once a layer is fully deposited, its orientation is changed so that the next layer is deposited along a different path than the previous one. Each layer is deposited parallel or not (depending on the geometry of the part to be produced) to the previous layer, with or without inter-layer spacing, and with full surface adhesion. This deposition process is particularly well-suited to reinforcing material widths between 3 and 300 mm, preferably with minimal width variation (< 0.25 mm). If the reinforcing material is wider, it can be deposited using any other suitable method.

[0113] In general, the manufacture of a composite part from at least one reinforcing material comprising at least one fibrous reinforcement associated on at least one of its faces with a porous thermoplastic layer and a resin corresponding to a thermosetting resin of the epoxy type includes the following successive steps: i) the injection or infusion, at a temperature typically ranging from 90 to 180°C, of ​​said resin, within said reinforcing material, placed inside the mold; ii) the consolidation of the reinforcing material / resin assembly, according to a heat treatment cycle; iii) the cooling of the consolidated composite part resulting from step ii).

[0114] In a conventional manner, prior to step i), the manufacturing process of a composite part according to the invention includes a step of arranging within a mold at least one reinforcing material comprising at least one fibrous reinforcement associated on at least one of its faces with a thermoplastic porous layer according to the invention.

[0115] Thus, the manufacturing of the composite part involves a diffusion step, by infusion or injection, of a thermosetting, thermoplastic resin, or a mixture of thermosetting and thermoplastic resins, within the reinforcing material or a stack of reinforcing materials according to the invention. This is followed by a consolidation step of the desired part through a polymerization / crosslinking step following a cycle defined by temperature and possibly pressure, and a cooling step. According to a particular embodiment, also adapted to all the implementation variants described in relation to the invention, the diffusion or injection, consolidation, and cooling steps are carried out in an open or closed mold.

[0116] As previously stated, in the context of the invention, and in a particularly preferred manner, the injected or infused resin is an epoxy resin.

[0117] Regarding step i), the temperature mentioned is that present inside the mold, during the injection or diffusion of the resin within the reinforcing material.

[0118] The resin is usually injected or infused while the reinforcing material, stack, or preform, into which the resin is injected or infused, is at a temperature of 110 to 180°C. This injection or infusion step usually lasts between 2 minutes and 5 hours and depends on the size of the composite part to be produced.

[0119] The invention will preferably use, for the production of the composite part, resin infusion under reduced pressure, in particular under a pressure lower than atmospheric pressure, specifically less than 1 bar and preferably between 0.1 and 1 bar. The infusion will preferably be carried out in an open mold (in particular equipped with a vacuum bag), for example by vacuum bag infusion. During the heat treatment step, a pressure lower than atmospheric pressure, specifically less than 1 bar and preferably between 0.1 and 1 bar, may also be applied.

[0120] In other processes according to the invention, the resin is added by injection, and the reinforcing material according to the invention, the stacking of such materials, or the preform is placed in a mold intended to be closed (conventionally referred to as a closed mold), particularly once the resin has been injected in sufficient quantity to fill the mold. In such cases where the resin is injected, the heat treatment step is carried out under pressure in a conventional manner, particularly at a pressure of 1 to 150 bar, and preferably from 1 to 10 bar. This is the case for the RTM, C-RTM, and HP-RTM processes, which are well known to those skilled in the art.

[0121] The composite part is then obtained after a consolidation step involving heat treatment. Step ii) is a heat treatment step of the resin / reinforcing material(s) assembly, leading to the crosslinking of the thermosetting resin and the consolidation of the composite part. This step includes heating to a temperature Ta, which is conventionally called the curing temperature of the composite part. This temperature Ta can be equal to or higher than that of step i). In such a case, where it is higher than the infusion or injection temperature of the resin, step ii) includes a heating phase, up to the temperature Ta.

[0122] The composite part is generally obtained through a conventional heating consolidation step, using a heat treatment cycle recommended by the resin supplier and following best practices. This consolidation step involves polymerization (in the case of a thermoplastic resin) or crosslinking (in the case of a thermosetting resin). With a thermosetting resin, gelation occurs before hardening / crosslinking. The pressure applied during the treatment cycle is low for infusion under atmospheric or reduced pressure (specifically from 0.1 mbar to 1 bar) and higher for injection molding in an RTM (specifically from 1 to 150 bar). Generally, epoxy resin is added under a pressure of 0.1 mbar to 15 bar, and more commonly from 1 to 10 bar.

[0123] Most often, during the heat treatment stage, also called the consolidation stage, the heat treatment cycle comprises two phases: a heating phase to a temperature Ta and a heating phase to that temperature Ta, generally called the curing or post-curing stage. The temperature Ta is the temperature at which the thermosetting resin becomes cross-linkable. The temperature Ta and the heating time at that temperature are selected to achieve complete cross-linking of the chosen epoxy thermosetting resin. The temperature Ta is, in particular, a function of the resin being injected or infused.Generally, the heating temperature (Ta) falls within the range of 120 to 220°C, preferably between 160 and 220°C, and ideally between 170 and 190°C. It is typically 180°C, particularly for epoxy resins used in the production of composite parts for the aerospace industry. Heating times at these temperatures are usually from 30 minutes to 5 hours, typically between 1 and 2 hours. The heating time will be adjusted by a person skilled in the art according to the Ta temperature. The lower the Ta temperature, the longer the heating time may be required to achieve complete curing of the resin.

[0124] Typically, the temperature rise is achieved by increasing it by 0.1 to 10°C per minute, and in particular by 1 to 3°C per minute, typically by 2°C per minute.

[0125] According to a first embodiment, the heat treatment step comprises a heating phase, in particular at a rate of 0.1 to 10°C / minute, up to a temperature Ta, which is higher than the melting temperature of said reactive thermoplastic polymer of said at least one thermoplastic porous layer present in the reinforcing material according to the invention, and heating to said temperature Ta, in particular for 5 minutes to 2 hours. The viscosity of the thermosetting resin (or more rigorously the thermosetting resin system modified following the reaction with the thermoplastic porous layer) increases between the melting of said reactive thermoplastic polymer of the thermoplastic porous layer(s) and the initiation of the crosslinking of the epoxy thermosetting resin.This increase in viscosity reflects the reactions that take place between the epoxy resin and the reactive -NH2 and / or -COOH functions of the reactive thermoplastic polymer of the thermoplastic porous layer of the reinforcing material.

[0126] The reaction between the epoxy resin and the reactive -NH2 and / or -COOH functions of the reactive thermoplastic polymer of the thermoplastic porous layer of the reinforcing material can also have the effect that during the heat treatment step, the gelation of the thermosetting epoxy resin occurs earlier than if the latter were subjected alone to the heat treatment step.

[0127] In specific embodiments, the gelation of the thermosetting resin occurs upon heating to temperature Ta, after a heating time of 5 to 60 minutes at temperature Ta. The timing of gelation of the epoxy resin will depend in particular on the reactivity of the epoxy resin, the injection / infusion temperature of the epoxy resin, the rate of temperature rise Ta, and the selected temperature Ta.

[0128] According to the first variant of the manufacturing process of a composite part according to the invention where the temperature Ta is greater than the melting temperature of said reactive thermoplastic polymer of said at least one thermoplastic porous layer, the thermosetting epoxy resin preferably has a glass transition temperature Tg greater than 150° C.

[0129] According to a second implementation variant, the heat treatment step includes a heating phase, specifically at a rate of 0.1 to 10°C / minute to a temperature Ta, which is lower than the melting point of the reactive thermoplastic polymer of at least one thermoplastic porous layer, and heating to said temperature Ta, specifically for 5 minutes to 5 hours. In this case, where heating to achieve complete crosslinking / polymerization of the epoxy resin is carried out at a lower temperature Ta, the heating time at this temperature may be longer. It will be adjusted by a person skilled in the art, depending on the resin used.Here again, the reaction between the epoxy resin and the reactive -NH2 and / or -COOH functions of the reactive thermoplastic polymer of the thermoplastic porous layer of the reinforcing material can also have the effect that during the heat treatment step, the gelation of the thermosetting epoxy resin occurs earlier than if the latter were subjected alone to the heat treatment step.

[0130] According to the second variant of the manufacturing process for a composite part according to the invention, where the temperature Ta is lower than the melting temperature of said reactive thermoplastic polymer of said at least one porous thermoplastic layer, the thermosetting epoxy resin preferably has a glass transition temperature Tg of at least 100°C, and advantageously in the range of 100 to 150°C.

[0131] Advantageously also, according to the second variant of the manufacturing process of a composite part according to the invention where the temperature Ta is lower than the melting temperature of said reactive thermoplastic polymer of said at least one porous thermoplastic layer, said reactive thermoplastic polymer has a melting temperature greater than 120°C.

[0132] In the context of the invention, and regardless of the specific embodiment of the process, during the heat treatment step, the gelation of the thermosetting resin occurs after reactive functions of the reactive thermoplastic polymer in the porous thermoplastic layer of the reinforcing material have reacted with the epoxy thermosetting resin. However, other reactions may still occur during the complete cross-linking of the resin.

[0133] Once the heat treatment is complete, cooling is achieved by circulating a fluid acting as a refrigerant, such as water or a mixture of water and air, while interrupting the heating process. Pressurization is usually stopped during cooling, particularly when a temperature below 40°C is reached.

[0134] Of course, the same characteristics and implementations described in connection with the reinforcing material according to the invention apply to the processes and uses described within the scope of the invention.

[0135] The reactive thermoplastic polymer used in the invention contains a sufficient quantity of reactive -NH2 and / or -COOH groups, enabling it to react with epoxy resins commonly used in the production of composite parts. As will be demonstrated by the examples, this reaction will impart particularly advantageous characteristics to the resulting composite parts, notably improving their resistance to temperature and humidity, while maintaining satisfactory mechanical properties, which are important for composite parts intended for the aeronautical and aerospace industries. Other aspects and other inventions

[0136] The present invention can be generalized to other thermosetting resins, besides those of the epoxy family.

[0137] Other usable thermosetting resins are, in particular, selected from unsaturated polyesters, vinyl esters, phenolic resins, polyimides, bismaleimides, phenol-formaldehyde resins, urea-formaldehyde resins, 1,3,5-triazine-2,4,6-triamines, benzoxazines, cyanate esters, and mixtures thereof. Such a resin may also include one or more curing agents, well known to those skilled in the art for use with the selected thermosetting polymers.

[0138] The reactive functional groups present on the reactive polymer will then be adapted by a person skilled in the art to enable it to react with the injected or infused thermosetting resin. In particular, in the case of unsaturated polyester or vinyl ester resins, as well as bismaleimides, the reactive thermoplastic polymer may contain unsaturations that allow it to react with these resins.

[0139] In the case of phenolic resins, the reactive thermoplastic polymer may, for example, contain alcohol, aldehyde or ketone functions enabling it to react with this type of resin.

[0140] The previous descriptions given in connection with the use of epoxy resin are applicable to these types of processes.

[0141] Therefore, this description also covers the following aspects.

[0142] The description relates to a manufacturing process for a composite part comprising the following successive steps: (0) an arrangement step within a mold of at least one reinforcing material comprising at least one fibrous reinforcement associated on at least one of its faces with a thermoplastic porous layer; (i) an injection or infusion step of a thermosetting resin, at a temperature ranging in particular from 90 to 180°C, within said reinforcing material placed inside the mold; (ii) a heat treatment step of the resin / reinforcing material(s) assembly, comprising heating to a temperature Ta, leading to the crosslinking of the thermosetting resin and the consolidation of the composite part; (iii) the cooling of the consolidated composite part resulting from step (ii); characterized in that said thermoplastic porous layer carries reactive functions which react with the thermosetting resin during the heat treatment step.

[0143] In particular, in such a process, the said thermoplastic porous layer(s) of said reinforcing material shall represent at most 10% of the total mass of the reinforcing material, preferably from 0.5 to 10% of the total mass of the reinforcing material, and preferably from 2 to 6% of the total mass of the reinforcing material.

[0144] In such a process, due to the porous layer present in the reinforcing material which reacts with the thermosetting resin, the latter will be only partially fusible, or even completely infusible, in thermosetting resins, particularly epoxy resins which are commonly used in the production of composite parts. In the process according to the invention, the thermoplastic porous layer carries reactive functionalities that react with the thermosetting resin during the heat treatment step, thereby reducing sensitivity to temperature exposure and improving temperature properties for materials used in the aerospace industry.

[0145] According to a first variant of such a process for manufacturing a composite part, the temperature Ta is higher than the melting temperature of the reactive thermoplastic polymer of at least one porous thermoplastic layer. In particular, heating to the temperature Ta is carried out in step ii) for 5 minutes to 2 hours. Most often, the heat treatment step includes a heating phase, in particular at a rate of 0.1 to 10°C / minute, up to the temperature Ta.

[0146] It is possible that the viscosity of the thermosetting resin increases between the melting of the reactive thermoplastic polymer in the thermoplastic porous layer and the initiation of cross-linking of the thermosetting resin. Specifically, it is the viscosity of the thermosetting resin system, modified following melting and reaction with the thermoplastic porous layer, that increases.

[0147] It is also possible that, during the heat treatment stage, the gelation of the thermosetting resin occurs earlier than if the latter were subjected to the heat treatment stage alone.

[0148] The gelation of the thermosetting resin can occur during heating to temperature Ta, particularly after a heating time of 5 to 60 minutes at temperature Ta.

[0149] According to the first variant of such a manufacturing process for a composite part where the temperature Ta is greater than the melting temperature of said reactive thermoplastic polymer of said at least one thermoplastic porous layer, the thermosetting resin preferably has a glass transition temperature Tg greater than 150°C.

[0150] According to a second variant of such a composite part manufacturing process, the temperature Ta is lower than the melting temperature of the reactive thermoplastic polymer of the thermoplastic porous layer. In particular, heating to said temperature Ta, for 5 minutes to 5 hours, is carried out during step ii). Preferably, the gelation of the thermosetting resin occurs earlier than if the resin were subjected to the heat treatment step alone. Again, generally, the heat treatment step includes a heating phase, in particular at a rate of 0.1 to 10°C / minute, up to said temperature Ta.

[0151] According to the second variant of such a process for manufacturing a composite part, where the temperature Ta is lower than the melting temperature of said reactive thermoplastic polymer of said at least one porous thermoplastic layer, the thermosetting resin preferably has a glass transition temperature Tg of at least 100°C, and advantageously in the range of 100 to 150°C.

[0152] Advantageously also, according to the second variant of such a process for manufacturing a composite part where the temperature Ta is lower than the melting temperature of said reactive thermoplastic polymer of said at least one porous thermoplastic layer, said reactive thermoplastic polymer has a melting temperature greater than 120° C.

[0153] In such manufacturing processes for a composite part, regardless of their implementation variant, the temperature Ta generally belongs to the range of 120 to 220°C, preferably to the range of 160 to 220°C, preferably to the range of 170 to 190°C, and is typically equal to 180°C.

[0154] In said manufacturing processes of a composite part, regardless of their implementation variant, during the heat treatment step, advantageously, the gelation of the thermosetting resin occurs after reactive functions have reacted with said thermosetting resin.

[0155] Furthermore, the reaction of the thermoplastic polymer in the porous layer with the injected or infused resin allows for the use of a porous layer with a low melting point. This enables the use of lower temperatures during manufacturing and shaping the reinforcing material, resulting in cost and time savings. Another advantage is that the melting point of the reactive thermoplastic polymer in the porous thermoplastic layer can be below 170°C, or even 150°C. This allows all the manufacturing process steps prior to adding the resin needed to complete the part (from preparing the dry material to its deposition and preforming) to be carried out at a temperature below 170°C, and even better, below 150°C or lower.Thus, such porous layers comprising a reactive thermoplastic polymer with a lower melting point will allow the manufacture of the reinforcement material combining porous layer(s) and fibrous reinforcement(s) at a temperature compatible with automated manufacturing processes, including fiber placement and hot forming of flat-deposited preforms.

[0156] Such processes therefore have the secondary objective of combining the beneficial effects of using a thermoplastic porous layer on impact resistance performance, while having the possibility of carrying out all the steps of the manufacturing process prior to the infusion or injection of the resin, at temperatures below 150°C, or even 140°C, these temperatures being in some cases even in the range of 80 to 130°C or 100 to 130°C.

[0157] Thus, advantageously, in said manufacturing process of a composite part, said reactive thermoplastic polymer of said at least one thermoplastic porous layer present within the reinforcing material has a melting temperature below 170°C, or even 150°C and preferably belonging to the range of 100 to 140°C, and preferably to the range of 100 to 130°C.

[0158] The said manufacturing processes for a composite part may include, prior to the infusion or injection of said thermosetting resin, a deposition or shaping of said reinforcing material(s), which uses the hot stickiness of said at least one thermoplastic porous layer present in said reinforcing material(s) and implements heating carried out at a temperature below 170°C, or even at 150°C and preferably belonging to the range from 80 to 140°C, in particular from 100 to 140°C, and preferably to the range from 80 to 130°C, in particular from 100 to 130°C, chosen according to the melting temperature of said reactive thermoplastic polymer of said thermoplastic porous layer.

[0159] The aforementioned manufacturing processes for a composite part are particularly suited to cases where the injected or infused resin is an epoxy resin.

[0160] Advantageously, said epoxy resin has a viscosity of less than 1000 mPa.s at a temperature of 90°C.

[0161] Particularly preferred examples of epoxy resins include those comprising a tetrafunctional epoxy, possibly mixed with a trifunctional epoxy, one or more hardening agents and one or more shock modifier(s).

[0162] In particular, in the aforementioned composite part manufacturing processes, the thermoplastic porous layer comprises a reactive thermoplastic polymer or is composed of one or more reactive thermoplastic polymers, a reactive thermoplastic polymer having -NH₂ functionalities in quantities exceeding 0.15 meq / g of reactive thermoplastic polymer and / or having -COOH functionalities in quantities exceeding 0.20 meq / g of reactive thermoplastic polymer. Such thermoplastic porous layers are particularly well-suited when the injected or infused resin is an epoxy resin, notably one of the resins described above.

[0163] Advantageously, said reactive thermoplastic polymer carries -NH2 functions in quantities greater than 0.20 meq / g of reactive thermoplastic polymer, preferably in the range of 0.20 to 1 meq / g of reactive thermoplastic polymer and preferably in the range of 0.20 to 0.95 meq / g of reactive thermoplastic polymer, and / or carries -COOH functions in quantities greater than 0.20 meq / g of reactive thermoplastic polymer, preferably in the range of 0.20 to 1 meq / g of reactive thermoplastic polymer and preferably in the range of 0.20 to 0.95 meq / g of reactive thermoplastic polymer.

[0164] In particular, the reactive thermoplastic polymer is a polyamide or a copolyamide carrying said functions.

[0165] In particular, in the aforementioned composite part manufacturing processes, at least one porous layer comprises -NH₂ functional groups in quantities exceeding 0.15 meq / g of porous layer and / or -COOH functional groups in quantities exceeding 0.20 meq / g of porous layer. Again, such thermoplastic porous layers are particularly well-suited to cases where the injected or infused resin is an epoxy resin, notably one of the resins described above.

[0166] According to specific embodiments, the reactive thermoplastic polymer has an average molecular mass in number Mn greater than 4000 g / mol.

[0167] According to particular embodiments, step i) is carried out by injection of the resin and the heat treatment of step iii) is carried out under a pressure of 1 to 150 bar in a closed mold.

[0168] According to other particular embodiments, the arrangement step 0) is carried out in an open mold, in particular equipped with a vacuum bag, and step i) is carried out under reduced pressure, in particular under a pressure between 0.1 and 1 bar.

[0169] In the reinforcing materials used in such processes, fibrous reinforcement can take different forms. According to some embodiments, fibrous reinforcement is a unidirectional sheet of reinforcing yarns, a fabric of reinforcing yarns, or a stack of unidirectional sheets of reinforcing yarns joined together by stitching or any other physical means, including needle punching.

[0170] The fibrous reinforcement can, in particular, be made of glass fibers, aramid fibers, or, preferably, carbon fibers.

[0171] According to certain embodiments of such processes, a reinforcing material used consists of a unidirectional web of reinforcing yarns corresponding to the fibrous reinforcement, associated on at least one of its faces with a thermoplastic porous layer as defined within the scope of the invention, preferably said reinforcing material consisting of a unidirectional web of reinforcing yarns corresponding to the fibrous reinforcement, associated on each of its faces with a thermoplastic porous layer as defined within the scope of the invention and the thermoplastic porous layers present on each of the faces of the unidirectional web of reinforcing yarns being identical.

[0172] According to certain embodiments, a reinforcing material used in said processes consists of a stack of unidirectional layers of reinforcing yarns, acting as fibrous reinforcements, oriented in different directions, with at least one thermoplastic porous layer as defined in the context of the invention, interposed between two unidirectional layers of reinforcing yarns and / or on the surface of the stack. Such a stack may consist of a superposition of layers corresponding to a sequence (CP / R)n (CP)m or (CP / R / CP)n, where CP designates a thermoplastic porous layer as defined in the context of the invention, R a unidirectional layer, n an integer greater than or equal to 1, and m equal to 0 or 1.In such stacks, the association of unidirectional sheets of reinforcing yarns with each other, or even their association with at least one porous thermoplastic layer, can be achieved by sewing, knitting or needle punching.

[0173] In the reinforcing materials used in said processes, the thermoplastic porous layer(s) present is / are, in particular, a porous film, a grid, a powder deposit, a fabric or, preferably, a non-woven or veil.

[0174] Another aspect of the description also relates to composite parts obtained by a manufacturing process as defined in this part.

[0175] This description therefore concerns composite parts comprising a thermosetting matrix, in particular epoxy, thermoset in which is included at least one reinforcing material comprising at least one fibrous reinforcement associated on at least one of its faces with a thermoplastic porous layer. In said composite parts, there are covalent bonds between the thermosetting epoxy matrix and the thermoplastic polymer present within the thermoplastic porous layer(s), said covalent bonds resulting from the reaction of reactive functions that were present on said thermoplastic polymer and the thermosetting resin, in particular epoxy.In particular, in such composite parts, the said thermoplastic porous layer(s) of said reinforcing material shall represent at most 10% of the total mass of the reinforcing material, preferably from 0.5 to 10% of the total mass of the reinforcing material, and preferably from 2 to 6% of the total mass of the reinforcing material.

[0176] The examples below, with reference to the attached Figures, illustrate the invention, but are not intended to be limiting. Brief description of the Figures

[0177] [ Fig. 1 ] There figure 1 is a schematic view of a manufacturing process for an example of a reinforcing material according to the invention. Fig. 2 ] There figure 2 is a schematic view of an example of reinforcing material according to the invention. Fig. 3 ] There figure 3presents images obtained under optical microscopy, when different sheets and RTM6 epoxy resin are placed between two glass slides and subjected to heating at 180°C. Fig. 4 ] There figure 4 represents the reversible and irreversible heat fluxes following a temperature increase of 2°C / min, by modulated differential calorimetric analysis, of different layers in a tetrafunctional epoxy resin from Huntsman, which does not contain a hardener, after a 1h 120°C + 2h 180°C cycle with a temperature increase of 2°C / min. Fig. 5 ] There figure 5 presents the evolution of the viscosity of RTM6 resin alone during curing, of RTM6 resin when diffused within a stack of CP1 porous layers according to the invention, and of the same stack of CP1 porous layers in an oil. Fig. 6 ] There figure 6presents the evolution of the viscosity of RTM6 resin alone (heating and then curing), and of RTM6 resin when diffused within a stack of porous CP1 or CP8 layers according to the invention bearing -COOH or CP9 functional groups outside the invention. Fig. 7 ] There figure 7 presents the evolution of modules G' and G", as a function of time and temperature, during the heat treatment step (heating up then curing), of the RTM6 resin when the latter is diffused within a stack of porous CP8 layers conforming to the invention or CP9 outside the invention. Fig. 8 ] There figure 8 presents the evolution of the viscosity of RTM6 resin alone during the heat treatment step (heating up then curing), and of RTM6 resin when the latter is diffused within a stack of porous CP2 or CP5 layers according to the invention bearing -NH2 or CP4 functional groups outside the scope of the invention. Fig. 9 ] There figure 9 presents the evolution of the viscosity of RTM6 resin alone during the heat treatment step (heating up then curing), of a tetrafunctional epoxy resin from Huntsman, which does not include a hardener, when the latter is diffused within a stack of porous layers CP1, CP2, CP5 or CP8 according to the invention, or CP9 outside the invention. Fig. 10 ] There Figure 10 presents the evolution of viscosity and moduli G' and G", as a function of time and temperature, during the heat treatment step (heating up then curing), of the Huntsman tetrafunctional epoxy resin, which does not contain a hardener when the latter is diffused within a stack of CP8 porous layers according to the invention. Fig. 11 ] There figure 11presents the evolution of viscosity during the heat treatment step (heating up then curing) of the RTM6 resin when the latter is diffused within a stack of porous CP10 layers according to the invention or of non-porous film layers made of the same polymer. Fig. 12 ] There figure 12 shows the evolution of the freezing time (heating time at temperature Ta until the freezing point is reached) according to the isotherm temperature Ta (temperature used for resin infusion and curing) of the RTM6 resin, when the latter is diffused within a stack of porous CP8 layers according to the invention. Fig. 13 ] There figure 13presents the heating time at 180°C required to obtain gelation of the resin (crossing of modules G' and G") in the case of different epoxy resins diffused in a stack of different layers (according to the invention and outside the invention), after a temperature increase at 2°C / min from 120°C to 180°C + 2h at 180°C. Fig. 14 ] There figure 14 presented in the case of reinforcement material 2 (outside the scope of this invention), is the DMA curve obtained with and without conditioning at 70°C for 14 days, with a temperature increase of 2°C / min from 25 to 270°C, for a composite part obtained by injection of RTM6 resin. Fig. 15 ] There figure 15 presented in the case of the reinforcement material 5 (according to the invention), is the DMA curve obtained with and without conditioning at 70°C for 14 days, with a temperature rise of 2°C / min from 25 to 270°C, for a composite part obtained by injection of RTM6 resin. Fig. 16 ] There figure 16presented in the case of the reinforcement material 6 (according to the invention), the DMA curve obtained with and without conditioning at 70°C for 14 days, with a temperature rise of 2°C / min from 25 to 270°C, for a composite part obtained by injection of RTM6 resin. Examples Reinforcements, porous layers and resins used

[0178] The fibrous reinforcements used in all cases are unidirectional sheets of 210g / m2, made with carbon fibers marketed by Hexcel Composites, Dagneux France, under the reference IMA 12K. The properties of these 12K fibers are summarized in Table 1 below: Table 1 Hexcel IMA 12K tensile strength (MPa) 6,067 voltage module (GPa) 297 final elongation at break (%) 1,8 density (g / cm³) 1,79 weight / length (g / m) 0,445 filament diameter (µm) 5,1

[0179] The porous polymeric layers studied are presented in Table 2 below: Table 2 Polymer layer (PL) Polymer Nature of the layer COOH functions (meq / g)* NH2 functions (meq / g)* Melting point of the layer (°C) Other information 1 (invention) Arkema copolyamide voile (non-woven) 0,22 0,02 146 2 (invention) Arkema copolyamide voile (non-woven) 0,02 0,34 106 3 (excluding invention) Arkema Copolyamide voile (non-woven) 0,11 0,08 103 4 (excluding invention) Arkema Copolyamide voile (non-woven) - 0,06 126 5 (invention) Arkema Copolyamide voile (non-woven) - 0,34 128 6 (previous article) epoxy (thermosetting) powder depot Used in the Primetex 43098 S 1020 S E01 1F fabric marketed by Hexcel 7 (previous article) Platamid® copolyamide < HX2632 marketed by Arkema voile (non-woven) - - 105 Layer used in application WO 2019 / 102136, before crosslinking 7a (previous article) partially crosslinked copolyamide Platamid®< HX2632 marketed by Arkema Voile (non-woven) - - 100 Layer used in WO 2019 / 102136 request 8 (invention) Arkema Copolyamide voile (non-woven) 0,46 0,02 121 9 (previous article) copolyamide voile (non-woven) 0,10 0,12 160 Protechnic 1R8D04 sail used in WO 2019 / 102136 for comparison 10 (invention) Arkema Copolyamide voile (non-woven) 0,23 - 125 * meq / g of polymer = meq / g of porous layer

[0180] Table 3 provides more details on some of the polymers used to make the porous layers. Table 3 Polymer layer (PL) coPA: Ratio in % mass Diacid and diamine / triamine raw materials providing amine and acid functions ** Raw material providing cross-linking ** 6 66 6.10 6.12 11 12 Adipic acid DC6 Hexamethylene diamine HMDA Diethylenetriamine DETA (multifunctional monomer) Undecylenic acid (unsaturated monoacid) 1 (invention) 35 30 35 - - - 1,3 - 2 (invention) 22 28 - - - 50 - 1,80 - 5 (invention) 20 - - 30 - 50 - 1,80 - 8 (invention) 25 - - 25 - 50 3,6 - 0,23 1 (**) : (mass % of the formulation used for the formation of coPA)

[0181] The porous layers used for comparison were made with: 1) CP9: a thermoplastic veil 1R8004 marketed by Protechnic (66, rue des Fabriques, 68702 - CERNAY Cedex - France) with a melting point of 160°C. This veil (hereafter referred to as veil 1 R8D04) is obtained by meltblown and has a surface mass of 4 g / m² and a thickness of 100 µm before lamination onto the fibrous reinforcement. The diameter of the constituent fibers is 15 µm. The openness factor of such a layer is approximately 50%.2) CP7: a fiber veil made of Platamid® HX2632 polymer, marketed by Arkema (a copolyamide with terminal unsaturations that allow for a three-dimensional network under UV, gamma, or beta treatment), which has a melting point of 117°C. This veil (hereafter referred to as the HX2632 veil) is produced by meltblown and has a surface mass of 4 g / m² and a thickness of 100 µm before being bonded to the fibrous reinforcement. The diameter of the constituent fibers is 15 µm. The openness factor of such a layer is approximately 50%. CP7a: a fiber veil made of a Platamid ®< HX2632 polymer marketed by Arkema crosslinked under beta treatment (100 kGy, as described in application WO 2019 / 102136), which has a melting temperature of 109°C.This veil is obtained by meltblown, has a surface mass of 4 g / m², a thickness of 100 µm before bonding to the fibrous reinforcement, and is partially cross-linked under beta treatment. The diameter of the constituent fibers is 15 µm. The openness factor of such a layer is approximately 50%. 3) CP6: by depositing a layer of epoxy powder used in the Primetex 43098 S 1020 S E01 1F fabric, marketed by Hexcel Composites, Dagneux, France. The average diameter of the powder is 51 µm (D50, median value), and its glass transition temperature is in the range of 54 to 65°C. 4) CP3: a fiber veil made of a Platamid ® polymer marketed by the company Arkema, which has a melting temperature of 103°C - this veil is obtained by meltblown and has a surface mass of 4 g / m2 and a thickness of 100 µm before laminating onto the fibrous reinforcement.The diameter of the constituent fibers is 15 µm. The openness factor of such a layer is approximately 50%. 5) CP4: a fiber veil made of a Platamid® polymer marketed by Arkema, which has a melting point of 126°C - this veil is obtained by meltblown and has a surface mass of 4 g / m² and a thickness of 100 µm before lamination onto the fibrous reinforcement. The diameter of the constituent fibers is 15 µm. The openness factor of such a layer is approximately 50%.

[0182] The porous layers according to the invention were made with: 1) CP1: A fiber veil made of Platamid® polymer, marketed by Arkema, with a melting point of 146°C. This veil is produced by meltblown and has a surface mass of 4 g / m² and a thickness of 100 µm before being bonded to the fibrous reinforcement. The diameter of the constituent fibers is 15 µm. The openness factor of such a layer is approximately 50%. 2) CP2: A fiber veil made of Platamid® polymer, marketed by Arkema, with a melting point of 106°C. This veil is produced by meltblown and has a surface mass of 4 g / m² and a thickness of 100 µm before being bonded to the fibrous reinforcement. The diameter of the constituent fibers is 15 µm. The openness factor of such a layer is approximately 50%.3) CP5: a copolyamide film produced by Arkema, which has a melting point of 128°C - this film is . held together by meltblown and has a surface mass of 4 g / m² and a thickness of 100 µm before being bonded to the fibrous reinforcement. The diameter of the constituent fibers is 15 µm. The openness factor of such a layer is approximately 50%. 4) CP8: a copolyamide veil produced by Arkema, which has a melting point of 121 °C - this veil is held together by meltblown and has a surface mass of 4 g / m² and a thickness of 100 µm before being bonded to the fibrous reinforcement. The diameter of the constituent fibers is 15 µm. The openness factor of such a layer is approximately 50%. 5) CP10: a copolyamide veil produced by Arkema, which has a melting point of 125°C - this veil is It is held together by meltblown and has a surface mass of 4 g / m² and a thickness of 100 µm before being bonded to the fibrous reinforcement. The diameter of the constituent fibers is 15 µm. The openness factor of such a layer is approximately 50%.

[0183] The thermosetting resins used for the production of composite parts are presented in Table 4 below: Table 4 Resin Type Commercial Reference Supplier Main features: Temperature and cooking time* HexFlow® tetrafunctional epoxy < RTM6 Hexcel composites 180°C, minimum 90 minutes HexFlow® tetrafunctional epoxy < HF620 Hexcel composites 180°C, 2 hours Prism® three-functional epoxy < EP2400 Solvay 180°C, 2 hours Prism® trifunctional epoxy < EP2410 Solvay 180°C, 2 hours *As recommended on the product sheet

[0184] Methods for determining the quantity of -NH2 and -COOH functional groups: The quantity of reactive -COOH or -NH2 functional groups present can be evaluated by potentiometric titration. The quantity of -COOH functional groups is determined by acid-base titration of the porous layer with tetra-n-butylammonium hydroxide ((C4H9)4N+<OH-<TBAOH) in alcoholic solution, while the quantity of -NH2 functional groups is determined by titration with perchloric acid (HClO4) in acetic acid. The results are expressed in meq / g of polymer evaluated. The method described in document AB-068, entitled "Potentiometric Determination of Terminal Carboxyl and Amino Groups in Polyesters and Polyamides," from Metrohm, details the procedure for determining the carboxylic acid and amine functional groups present by potentiometric titration.

[0185] The reagents used for the titration are as follows: TBAOH (concentration 0.1mol / L in isopropanol) = titrant for COOH reactive functions, HClO 4 (concentration 0.1mol / L in glacial acetic acid) = titrant for NH 2 reactive functions, benzyl alcohol.

[0186] To determine the amount of COOH reactive functions, between 0.5 and 1.5 g of sample is weighed into a beaker, mixed with 100 mL of benzyl alcohol, and diluted by heating to boiling. After cooling to around 80–100°C, the titration is performed with TBAOH. The burette tip is only slightly immersed in the solution. A blank value (i.e., without adding any sample) is determined under the same conditions.

[0187] To determine the amount of NH₂ reactive functions, between 0.5 and 1.0 g of sample is weighed into a beaker, mixed with 100 mL of benzyl alcohol, and diluted by heating to boiling. After cooling to approximately 80–100°C, the titration is performed with perchloric acid (HClO₄). The tip of the burette is only slightly immersed in the solution. A blank value is determined under the same conditions.

[0188] The quantity of reactive functions is then calculated using the following formula: Quantité de fonctions réactives COOH ou NH 2 , en μeq / kg = A − B × t × 100 E

[0189] Where A is the consumption in mL of titrant for the sample, B the consumption in mL of titrant for the blank, t the titration of the titrant and E the mass of the sample in g.

[0190] The titer of the titrant is determined by potentiometry according to Metrohm Bulletin 206 / 5 e "Titer determination in potentiometry". For TBAOH, benzoic acid is generally used; for HClO4, TRIS (tris-hydroxymethyl)-aminomethane is generally used.

[0191] Lamination of the sails - Obtaining a reinforcement material known as UD warped

[0192] The sails are associated with the unidirectional sheet of carbon fibers with a production line using a machine as described in application WO 2010 / 061114 and detailed further below, with reference to the figure 1 The resulting reinforcing material 1 is schematically represented on the figure 2 : it consists of a unidirectional sheet 2 of carbon fibers 3 associated on each of its faces with a veil 4,5, the association having been obtained thanks to the hot stickiness of the thermoplastic veils 4,5.

[0193] Carbon wires 3 are unwound from corresponding reels 30 of carbon wires fixed on a creel 40, pass through a comb 50, are guided into the axis of the machine by means of a guide roller 60, a comb 70 and a guide bar 80a.

[0194] The carbon fibers 3 are preheated using a heating bar 90 and then spread using the spreading bar 80b and the heating bar 100 to the desired carbon surface mass for the unidirectional web 2. The rolls 13a and 13b of the webs 4 and 5 are unrolled without tension and transported using continuous conveyors 15a and 15b fixed between the free-rotating, non-motorized rollers 14a, 14b, 14c, 14d and the heated bars 12a, 12b. The webs 4 and 5 are preheated in zones 11a and 11b before coming into contact with the carbon fibers 3 and are bonded on either side of two heated bars 12a and 12b, the gap between which is controlled. A calender 16, which can be cooled, then applies pressure to the unidirectional web with a veil on each side, to drive the reinforcing material 1 in the form of a ribbon.A return roller 18 allows redirection of the reinforcing material 1 to the traction system comprising a trio of pull 19 and winding 20 driven by a motor to form a roll made up of the reinforcing material 1 thus formed. Tests performed I. Measures taken

[0195] DSC: from the English "Differential Scanning Analysis". The analyses were performed on a Discovery 25 scanner from TA Instruments, Guyancourt, France.

[0196] DMA: from the English "Dynamic Mechanical Analysis". The analyses were carried out on a Q800 instrument from TA Instruments, Guyancourt, France, according to the EN 6032 standard (1Hz, 1°C / min, Amplitude 15 µm).

[0197] Hot microscopy analysis: The analyses were performed on an Axio M2m Microscope Imager from Zeiss, Marly-le-Roi, France, equipped with a heating device from Linkam Scientific Instruments, Tadworth, UK.

[0198] Rheology: Viscosity analyses were performed on a HAAKE Mars 60 rheometer from Thermo Fisher Scientific, Courtaboeuf, France. The analyses were carried out according to standard EN6043 at 2°C / min, 10 rad / s, but at a strain of 4% and not 10%. II. Influence of the reactive function rate on mobility in RTM6 resin

[0199] A porous layer (PL) to be studied and RTM6 epoxy resin applied to said porous layer are placed between two glass slides, and the entire assembly is then placed under an optical microscope. The system is subjected to a temperature increase of 2°C / min up to 180°C, corresponding to the final temperature during the infusion or injection of the RTM6 epoxy resin in the production of a composite part. This is therefore the critical cycle for the PL layer's temperature resistance, since no pre-curing step of the resin is used.

[0200] There figure 3The images shown were obtained at 180°C, i.e., after the resin has cured. It appears that the film dissolves or completely loses its integrity within the resin in the case of layers CP3, CP4, and CP7, which do not correspond to the definition of the invention. It also appears that the film loses its integrity within the resin in the case of layer CP8, which does correspond to the invention, indicating that the reactivity and integrity of the porous layer are uncorrelated. However, a reduction in the mobility of the porous layer within the resin is still observed, which is sufficient.

[0201] It is quite clear that, on the one hand, the presence of -NH2 groups in a porous layer, corresponding to an amount greater than 0.15 meq / g, allows it to maintain its integrity in contact with the epoxy resin, even when the temperature reached is well above its melting point (porous layers CP2 and 5), in the same way as the porous layer CP7a formed with a partially crosslinked thermoplastic polymer. The preservation of this integrity clearly demonstrates that a reaction has occurred between the porous layer and the resin.

[0202] Similarly, a quantity of -COOH groups in the porous layer greater than 0.20 meq / g is necessary for reactivity upon contact with the epoxy resin (porous layers CP1, CP8, and CP10), but this does not automatically guarantee the preservation of its integrity. A reduction in the mobility and dissolution of the porous layer in the resin is nevertheless observed, clearly demonstrating that a reaction has occurred between the porous layer and the resin. These observations therefore highlight the fact that the reaction between the porous layer and the epoxy resin can lead to a more or less pronounced preservation of the porous layer's integrity. Further studies were conducted to demonstrate the presence or absence of reaction between the studied porous layers and the resin. III. Demonstration of the reactivity of porous layers on epoxy functions

[0203] Different results were obtained with porous layers and a tetrafunctional epoxy from Huntsman, which does not contain a hardener: Modulated Differential Calorimetric Analysis (MDSC) Plane-plane rheology. Modulated Differential Calorimetric Analysis (MDSC)

[0204] Approximately 2 mg of porous layer were impregnated with approximately 18 mg of epoxy, and the assembly was placed in a hermetically sealed, perforated aluminum DSC capsule. These capsules were then placed in an oven and subjected to a temperature cycle equivalent to the standard cycles used in the production of composite parts by infusion or injection molding: 1 hour at 120°C + 2 hours at 180°C with a temperature increase of 2°C / min. After curing, the samples were slowly cooled naturally to room temperature.

[0205] The samples thus obtained were then analyzed by MDSC at 2°C / min to differentiate between reversible phenomena (glass transitions of the epoxy and the film, film melting) and irreversible phenomena (exothermic crosslinking of the resin). The results are presented on the figure 4 .

[0206] The first observation is that the curing cycle does not affect the epoxy, as the MDSC curve remains unchanged with a glass transition temperature of approximately -15 / -20°C. However, it is clear that if there is reactivity between the porous layer and the epoxy during the curing cycle, the porous layer is no longer able to recrystallize and therefore no longer exhibits a melting point during MDSC analysis (porous layers CP1 and 2). Conversely, when the porous layer does not react with the epoxy, it can recrystallize upon cooling, as indicated by the melting point of porous layer CP9, which is visible at approximately 150°C.

[0207] A second observation is the initiation of epoxy crosslinking at high temperature, which occurs 10 to 20°C earlier when the resin has been able to react partially with the porous layer.

[0208] Finally, a slight glass transition is observed around 10-20°C when the porous layer is able to react with the epoxy. This glass transition could be that of a portion of the epoxy that has initiated cross-linking with the porous layer. Rheology plan-plan

[0209] A 35 mm diameter, 0.12 g porous layer disc was prepared by stacking several layers of the porous layer. The resulting disc was then immersed in RTM6 epoxy resin to ensure complete impregnation and subsequently positioned on the lower platform of the rheometer. Excess resin was then removed as the upper platform was lowered until a 0.5 mm gap was created, within which the resin-impregnated porous layer sample was placed.

[0210] The imposed deformation was 4% and the shear frequency was 10 rad / s, according to standard EN6043 and the baking cycle was an isothermal one hour at 120°C, followed by a rise at 2°C / min up to 180°C for 2 hours.

[0211] There figure 5The diagram shows the evolution of viscosity during curing, and it is clear that after melting of the CP1 porous layer, the viscosity gradually increases, whereas in the absence of the porous layer, the viscosity of the RTM6 resin remains stable, or even decreases slightly as the temperature increases before crosslinking occurs. To ensure that the increase in the system's viscosity in the presence of the CP1 porous layer was solely due to the porous layer, the same test was also performed by immersing it in an oil with the same viscosity as RTM6 at 120°C (PMX-50 oil). It was observed that the CP1 porous layer melted more significantly (the viscosity level dropping by two decades compared to one decade in RTM6) and that the viscosity of the mixture then remained constant.This observation therefore confirmed that the observed increase in the viscosity of the porous layer / RTM6 resin system, which followed the melting of the porous layer, was due to reactions occurring between the RTM6 resin (and more particularly its epoxy function) and the CP1 porous layer (and more particularly its reactive - COOH functions).

[0212] There figure 6 presents the same type of results, but in the presence of different porous layers possessing -COOH functions: CP1 and CP8 in accordance with the invention and CP9 carrying only 0.10 meq / g of -COOH functions and 0.12 meq / g of -NH2 functions, therefore outside the invention.

[0213] These results clearly show that by controlling the amount of -COOH functions in the porous polyamide layers, it is possible to control the level of their reactions with the epoxy resin.

[0214] Shear rheology also allows us to track crosslinking, since at the gel point (or gelation point), the conservation modulus G' and the loss modulus G" are equivalent. The gel point therefore corresponds to the intersection between the two curves G' and G".

[0215] By increasing the -COOH functionality of the porous layers (CP8), it is possible to obtain crosslinking between the porous layer and the RTM6 resin as indicated by the crossing of the G' and G" modules after 50 minutes of experiment and at 158°C ( figure 7 ). In the presence of the CP9 porous layer, the RTM6 gel point is virtually unchanged, which confirms that the porous layer does not react with the resin.

[0216] Similarly, the figure 8presents the evolution of viscosity in the presence of different porous layers possessing -NH2 functions. It is observed once again that by increasing the proportion of -NH2 functions in the polyamide porous layers, it is possible to control the level of reactions between them and the epoxy resin.

[0217] These results were complemented by a second series of experiments in which the porous layers studied were immersed not in RTM6 resin, but in a Huntsman tetrafunctional epoxy without a hardener. This was done to better highlight the reactions between the reactive functions of the polyamide and the epoxy, which could be masked by the presence of the hardener in RTM6 resin, since the kinetics of the epoxy / hardener reaction are faster than those of epoxy alone. Otherwise, the test conditions were strictly identical, and the results obtained are presented in figure 9and allow monitoring of any gelation of the epoxy / polyamide system. With the CP8 layer, a clear increase in viscosity is observed during the temperature rise ( figure 9 ), but also, it appears that the crossing of modules G' and G" ( Figure 10 ) occurs after 28 minutes of temperature rise and at 155°C. It is important to note that epoxy resin alone gels after more than 11 hours at 180°C, which also confirms that the observed gel point in Figure 10This stems from the reaction between the porous layer and the epoxy. For the other layers CP1, CP2, and CP5, no change in the epoxy's gel point is observed; however, a limitation in the melting of the porous layer and an increase in the mixture's viscosity are observed, indicating a reaction between the reactive functions and the epoxy. Conversely, layer CP9 melts pronouncedly, and the mixture's viscosity remains constant throughout the test, indicating an absence of interaction or reactivity ( figure 9 ). IV. No influence of the porous layer structure on the reactivity of RTM6 resin with epoxy

[0218] The polyamide of porous layer 10 (CP10) in non-woven form was also tested as a 100 µm thick non-porous film to assess whether the structure of the polyamide layer used influenced its reactivity with the epoxy of the RTM6 resin. It appears on the figure 11(which shows the evolution of viscosity during a temperature increase at 2°C / min from 120°C to 180°C over 2 hours of epoxy / polyamide samples according to the porous layer or film structure of the polyamide) that the layer structure has no influence on its reactivity with the epoxy. Thus, the accessibility of the -COOH groups of the polyamide remains the same whether it is in the form of a non-woven fabric (CP10) or a non-porous film. V. Reactivity of the porous layer at a temperature below its melting point

[0219] The ability of the porous layer to react with the RTM6 resin below its melting point was validated with the CP8 porous layer. figure 12 shows the evolution of the freezing time (heating time at temperature Ta until the freezing point is reached) as a function of the isotherm temperature Ta (temperature used for resin infusion and curing), applied during the test for an RTM6 sample and an RTM6 / CP8 porous layer sample. It appears on the figure 12that the porous layer can react and modify the freezing point of RTM6, even below its melting point. Thus, even though it is clear that the reaction kinetics of the CP8 / RTM6 porous layer are accelerated when the two materials are brought into contact above the melting point of the porous layer (leading to greater mobility of the porous layer and therefore increased accessibility of the -COOH groups of the polyamide), the reaction is also possible below the melting point. VI. Application to various commercial resins

[0220] The different porous layers were immersed in the four commercial resins described previously, namely RTM6, HF620, EP2400, and EP2410. The freezing point was then measured as the intersection of the moduli G' and G" during a temperature increase at 2°C / mh from 120°C to 180°C + 2h at 180°C. figure 13presents all the results obtained. When gelation occurs during the heating phase at 180°C, the difference lies in the heating time required to achieve gelation, which is shown in the upper part of the figure 13 .

[0221] The difference in reactivity between RTM6 and HF620 resins, on the one hand, and EP2400 and EP2410 resins, on the other, is clearly apparent and manifests itself in a very different gelation time at 180°C. The decreased reactivity of the resin gives the porous layers more time to react. Thus, although reactions between the reactive groups and the epoxy occur as previously demonstrated, the CP1 porous layer (carrying -COOH groups, according to the invention) and the CP5 porous layer (carrying -NH2 groups, according to the invention) do not influence the gel point of RTM6. However, with these same layers, the gel point is altered for HF620 resin, and this effect is even more pronounced for EP2400 and EP2410 resins.Thus, due to the slowing of the epoxy / hardener reaction kinetics in the case of HF620, EP2400, and EP2410 resins, the reactions between the reactive functional groups and the epoxy have a greater impact on the resin's gel point. However, regardless of whether or not there is a change in the gel point, in the case of RTM6 resin, with the porous layers according to the invention, there are reactions between the reactive functional groups carried by said layers and the epoxy resin, as previously demonstrated, and these reactions also result in the maintenance of mechanical properties, as shown in paragraph IV below. Conversely, with the CP4 and CP9 porous layers (not part of the invention), there is no change in the gel point, regardless of the resin: EP2400 and EP2410 or RTM6 and HF620. This confirms that in this case, there is no reaction with the epoxy resin.

[0222] These results also highlight the influence of the epoxy functionality of the tested resins. While the epoxies in the case of RTM6 and HF620 are tetrafunctional, they are trifunctional in the case of EP2400 and EP2410 resins. This means that there are fewer accessible epoxy groups in these two resins, resulting in slower reactivity with the porous layers, particularly noticeable in the case of the CP8 porous layer, which reacted especially quickly with the RTM6 and HF620 resins. This, however, allows time for the other porous layers (CP1, CP5) to react. VII. Influence of the reactivity of porous layers on the mechanical properties of the composite

[0223] Seven reinforcing materials presented in Table 5 were compared, four according to the invention and four for comparison. Table 5 Material 1 comparison Material 2 comparison Material 3 according to the invention Material 4 according to the invention Porous layer Primetex fabric epoxy powder (CP6) Sail 1RSD04 (CP9) CP1 CP2 Material 5 according to the invention Material 6 according to the invention Material 7 comparison Material 7a comparison Porous layer CPS CPS CP7 CP7a

[0224] The conditions used for the manufacture of unidirectional carbon sheets combined with a porous layer on each side are indicated in Table 6 below. Table 6: Process parameters for implementing unidirectional sheets associated with a veil on each side Material Measured surface mass of the unidirectional (g / m²) Line speed (m / min) T bars (°C) T bar (°C) T preheating sail T bars (°C) (90) (100) (°C) (12a & (11a & 11b) 12b) 2 210 2,4 200 200 160 180 3 210 2,4 60 65 85 100 4 210 2,4 60 65 85 100 5 210 2,4 60 65 85 100 6 210 2,4 60 65 85 100 7 210 2,4 60 65 85 100 7a 210 2,4 60 65 85 100

[0225] A 340 mm x 340 mm preform, composed of a stacking sequence adapted to the carbon basis weight, was placed in an injection mold under pressure. A frame of known thickness surrounding the preform allowed for achieving the desired TVF fiber volume percentage.

[0226] The epoxy resin marketed by Hexcel under the reference HexFlow RTM6 was injected at 80°C under 2 bar through the preform, which was maintained at 120°C inside the press. The pressure applied by the press was 5.5 bar. Once the preform was filled and the resin was flowing from the mold, the outlet pipe was closed and the heat treatment cycle initiated: 3°C / min up to 180°C, followed by heating for 2 hours at 180°C and cooling at 5°C / min.

[0227] Specimens were then cut to the appropriate dimensions to carry out compression after impact (CAI), in-plane shear (IPS), and compression on perforated plate (OHC) tests, summarized in Table 7. Table 7 IPS CAI OHC Orientation of the preform folds [45 / 135]2s [45 / 0 / 135 / 90]3s [45 / 0 / 135 / 90]35 Testing machine Instron 5582 Zwick Z300 Zwick Z300 EN standard 6031 6038 6036

[0228] The results obtained for all of these tests are listed in Tables 8 to 10. The mechanical results presented show that the results according to the invention make it possible to obtain composite parts with optimal properties, in particular in terms of impact resistance (CAI), mechanical properties showing sensitivity to holes such as compression hole (OHC) or shear in plane (IPS).

[0229] It can thus be seen that, on the one hand, although epoxy powder (comparative material 1) solves the problem of carrying out all the steps of the dry preform manufacturing process at temperatures between 80 and 130°C, it does not allow for the production of composite parts with optimal mechanical properties. On the other hand, conventional polyamide web (comparative material 2), conversely, allows for optimal mechanical properties, but requires higher temperatures for its manufacture and shaping. The materials according to the invention, however, address both problems.

[0230] Materials 3 to 6 according to the present invention thus make it possible to combine both a manufacturing and shaping process at temperatures below 130°C and optimal mechanical properties in composite parts. It should also be emphasized that the mechanical performance is comparable regardless of the material of the invention, even if the integrity of the porous layer is lost and only the mobility of the porous layer is reduced (material 6 with CP8 layer), or even if the porous layer does not cause a change in the gel time of the RTM6 resin (material 3 with CP1 layer or material 5 with CP5 layer). Thus, in all cases, with the materials according to the invention, the reactive functional / epoxy reactions are sufficient to prevent deterioration of the mechanical properties of the resulting composite part due to the presence of the porous layer, despite its low melting point.Similarly, it is observed that with the materials according to the invention, the mechanical properties are equivalent to the properties obtained with the comparative material 7a whose thermoplastic CP7a layer is partially crosslinked.

[0231] IPS performance is also improved compared to the comparator material 7. Tableau 8- IPS IPS Material 1 comparison Material, 2 comparisons Material 3 according to the invention Material 4 according to the invention Module (dry, 23°C) (GPa) 4,1 4,4 4,5 4,4 Stress 0.2% (dry, 23°C) (MPa) 39 38 39 40 Modulus (dry, 90°C) (GPa) 3,6 3,4 3,8 3,8 Stress 0.2% (dry, 90°C) (MPa) 32 29 31 32 IPS Material 5 according to the invention Material 6 according to the invention Material 7 comparison Material 7a comparison Module (dry, 23°C) (GPa) 4, 6 4,6 4,2 4,6 Stress 0.2% (dry, 23°C) (MPa) 41 41 40 41 Modulus (dry, 90°C) (GPa) 3,5 3,6 2,9 3,9 Stress 0.2% (dry, 90°C) (MPa) 30 30 25 33 Tableau 9 - OHC OHC compression Material 1 comparison Material 2 comparison Material 3 according to the invention Material 4 according to the invention dry, 23°C (MPa) 257 285 300 285 dry, 90°C (MPa) 228 228 218 218 OHC compression Material 5 according to the invention Material 6 according to the invention Material 7 comparison Material 7a comparison dry, 23°C (MPa) 291 292 285 295 dry, 90°C (MPa) 220 210 99 238

[0232] As shown in Table 9, with the materials according to the invention, the OHC performance is identical or even better. Tableau 10 - CAI CAI standardized to 60%TVF (dry, 23°C) Material 1 comparison Material 2 comparison Material 3 according to the invention Material 4 according to the invention 30J (MPa) 126 259 293 290 70J (MPa) - 192 241 237 CAI normansée at 60% TVF (dry, 23°C) Material 5 according to the invention Material 6 according to the invention Material 7 comparison Material 7a comparison 30J (MPa) 264 264 167 255 703 (MPa) - - - 211

[0233] With the materials according to the invention, the CAI performances shown in Table 10 are better than those obtained with comparative materials 1 and 7, which have comparable melting points. However, they are comparable to those obtained with comparative material 2, which requires shaping at a higher temperature. VIII. Influence of porous layer reactivity on stability during temperature conditioning

[0234] The tests carried out showed that a composite part obtained by combining a reinforcing material with a thermoplastic porous layer and RTM6 resin exhibited two transitions under temperature stress. The first transition corresponds to the glass transition of the thermoplastic porous layer enriched with epoxy resin and occurs at temperatures below 100°C, while the second transition corresponds to the glass transition of the epoxy matrix and occurs at temperatures of around 200°C.

[0235] Most aging of composite materials in contact with aggressive fluids occurs at temperatures up to 70°C with varying contact times. During the aging of comparative material 2 (with a CP9-1 R8D04 porous layer) at 70°C, an evolution of the glass transition in the thermoplastic porous layer enriched with epoxy resin was observed, due to phase separation and curing of this epoxy resin. An example of the result is presented in figure 14 which shows the material's response to DMA stress (DMA curves obtained with and without conditioning for 14 days at 70°C: 2°C / min from 25 to 270°C). The transition changes significantly from approximately 60°C to approximately 100°C during aging at 70°C, while the glass transition of RTM6 does not change (not shown).

[0236] Conversely, by using the porous layers according to the invention in materials 5 and 6 according to the invention (the figure 15 and the figure 16 (respectively), it clearly appears that the glass transition of the thermoplastic porous layer, which reacted with the epoxy resin, remains relatively stable during aging at 70°C. This is explained by the fact that there is no phase separation between the two materials that reacted chemically during the curing of the RTM6 resin.

[0237] This confirms the results obtained by optical microscopy and shows that the reactions between the porous layers according to the invention and the resin minimize the impact of the presence of said porous layer on the properties of the resin, despite its low melting point. This is one of the advantages of the invention, since it appears that the presence of the porous layers proposed in the invention does not affect the thermomechanical properties of the thermosetting resin.

Claims

1. Reinforcing material (1) comprising at least one fibrous reinforcement (2) associated on at least one of its faces with a thermoplastic porous layer (4,5), said thermoplastic porous layer(s) (4,5) representing at most 10% of the total mass of the reinforcing material (1), preferably from 0.5 to 10% of the total mass of the reinforcing material (1), and more preferably from 2 to 6% of the total mass of the reinforcing material (1), said fibrous reinforcement (2) being a unidirectional web of reinforcing yarns (3), a fabric of reinforcing yarns or a stack of unidirectional webs of reinforcing yarns bonded together by needling or any other physical means, characterized in that said porous thermoplastic layer (4, 5) or each of said porous thermoplastic layers (4, 5) present comprises a so-called reactive thermoplastic polymer or consists of one or more reactive thermoplastic polymers, a reactive thermoplastic polymer carrying -NH2 functions in a quantity greater than 0.15 meq / g of reactive thermoplastic polymer and / or carrying - COOH functions in a quantity greater than 0.20 meq / g of reactive thermoplastic polymer.

2. Reinforcing material (1) according to claim 1, characterized in that the said reactive thermoplastic polymer carries -NH2 functions in an amount greater than 0.20 meq / g of reactive thermoplastic polymer, preferably in the range from 0.20 to 1 meq / g of reactive thermoplastic polymer and more preferably in the range from 0.20 to 0.95 meq / g of reactive thermoplastic polymer, and / or carries - COOH functions in an amount greater than 0.20 meq / g of reactive thermoplastic polymer, preferably in the range from 0.20 to 1 meq / g of reactive thermoplastic polymer and more preferably in the range from 0.20 to 0.95 meq / g of reactive thermoplastic polymer.

3. Reinforcing material (1) according to claim 1 or 2, characterized in that the reactive thermoplastic polymer of said porous thermoplastic layer(s) (4,5) present within the reinforcing material (1) has a melting temperature in the range from 100 to 140°C, and preferably in the range from 100 to 130°C.

4. Reinforcing material (1) according to any one of claims 1 to 3, characterized in that the reactive thermoplastic polymer is a polyamide or copolyamide carrying said -NH2 and / or -COOH functions.

5. Reinforcing material (1) according to any one of claims 1 to 4, characterized in that the said thermoplastic porous layer(s) (4,5) present comprise(s) -NH2 functions in an amount greater than 0.15 meq / g of porous layer and / or -COOH functions in an amount greater than 0.20 meq / g of porous layer.

6. Reinforcing material (1) according to any one of claims 1 to 5, characterized in that the reactive thermoplastic polymer has a number-average molecular weight Mn greater than 4000 g / mol.

7. Reinforcing material (1) according to any one of claims 1 to 6, characterized in that the fibrous reinforcement (2) consists of glass fibers, aramid fibers or, preferably, carbon fibers.

8. Reinforcing material (1) according to any one of claims 1 to 7, characterized in that it consists of a unidirectional web of reinforcing yarns (3) corresponding to the fibrous reinforcement (2), associated on at least one of its faces with a thermoplastic porous layer (4, 5) as defined in any one of claims 1 to 6, preferably said reinforcing material (1) consisting of a unidirectional web of reinforcing yarns (3) corresponding to the fibrous reinforcement (2), associated on each of its faces with a thermoplastic porous layer (4,5) as defined in any one of claims 1 to 6, and the thermoplastic porous layers (4,5) present on each of the faces of the unidirectional web of reinforcing yarns (3) being identical.

9. Reinforcing material (1) according to any one of claims 1 to 8, characterized in that said thermoplastic porous layer(s) (4, 5) have a hot tackiness and the association of the fibrous reinforcement (2) and said porous layer has been achieved thanks to the hot tackiness of said thermoplastic porous layer (4, 5).

10. Reinforcing material (1) according to any one of claims 1 to 7, characterized in that it consists of a stack of unidirectional webs of reinforcing yarns (3), as fibrous reinforcements (2), oriented in different directions, with at least one thermoplastic porous layer (4, 5) as defined in any one of claims 1 to 5 interposed between two unidirectional webs of reinforcing yarns (3) and / or on the surface of the stack.

11. Reinforcing material (1) according to claim 10, characterized in that it consists of a superposition of layers corresponding to a sequence (CP / R)n (CP)m or (CP / R / CP)n with CP designating a thermoplastic porous layer (4, 5) as defined in any one of claims 1 to 5, R a unidirectional web, n an integer greater than or equal to 1 and m equal to 0 or 1.

12. Reinforcing material (1) according to claim 10 or 11, characterized in that the unidirectional webs of reinforcing yarns (3) are associated with one another or with the at least one porous thermoplastic layer (4, 5) by sewing, knitting or needling.

13. Reinforcing material (1) according to any one of claims 1 to 12, characterized in that said porous thermoplastic layer(s) (4,5) present is (are) a porous film, a grid, a powder deposit, a fabric or, preferably, a non-woven or veil.

14. Method of preparing a reinforcing material (1) according to any one of claims 1 to 13, characterized in that it comprises the following successive steps: a1) providing a fibrous reinforcement (2), a2) providing at least one thermoplastic porous layer (4, 5) comprising a so-called reactive thermoplastic polymer, or consisting of one or more reactive thermoplastic polymers, a reactive thermoplastic polymer carrying -NH2 functions in an amount greater than 0.15 meq / g of reactive thermoplastic polymer and / or carrying -COOH functions in a quantity greater than 0.20 meq / g of reactive thermoplastic polymer, a3) associating the fibrous reinforcement and the at least one porous thermoplastic layer (4,5).

15. Method of preparation according to claim 14, characterized in that the association of step a3) is achieved by applying the at least one porous thermoplastic layer (4, 5) on the fibrous reinforcement (2), said application being accompanied or followed by heating of said reactive thermoplastic polymer causing its softening or melting, then followed by cooling, said heating preferably being carried out at a temperature below 170°C, or even 150°C and preferably in the range from 100 to 140°C, and more preferably in the range from 100 to 130°C.

16. Preform consisting, at least in part, of one or more reinforcing materials (1) according to one of claims 1 to 13.

17. Method of manufacturing a composite part from at least one reinforcing material (1) according to any one of claims 1 to 13, characterized in that an epoxy thermosetting resin is injected or infused into said reinforcing material (1), a stack of several reinforcing materials (1) according to any one of claims 1 to 13, or a preform according to claim 16.

18. Method of manufacturing a composite part according to claim 17, characterized in that it comprises, once the epoxy thermosetting resin has been injected or infused into said reinforcing material or said stack, a heat treatment step, comprising heating to a temperature Ta, leading to crosslinking of the epoxy resin and consolidation of the composite part, during which the epoxy resin reacts with at least some of the -NH2 and / or -COOH functions present on the reactive thermoplastic polymer of the thermoplastic porous layer(s) (4,5).

19. Method of manufacturing a composite part according to claim 18, characterized in that gelling of the epoxy resin takes place during the heat treatment step and the -NH2 and / or -COOH functions react with said resin, prior to gelling of the latter.

20. Method of manufacturing a composite part according to one of claims 17 to 19, characterized in that said temperature Ta is higher than the melting temperature of said reactive thermoplastic polymer of the at least one porous thermoplastic layer (4, 5).

21. Method of manufacturing a composite part according to one of claims 17 to 19, characterized in that said temperature Ta is lower than the melting temperature of said reactive thermoplastic polymer of said at least one porous thermoplastic layer (4, 5), and, preferably, gelling of the epoxy thermosetting resin occurs earlier than if the latter were subjected to the heat treatment step alone.

22. Method of manufacturing a composite part according to one of claims 17 to 21, characterized in that the temperature Ta is in the range from 120 to 220°C, preferably is in the range from 160 to 220°C, more preferably is in the range from 170 to 190°C, and is typically equal to 180°C.

23. Method of manufacturing a composite part according to one of claims 17 to 22, characterized in that the epoxy thermosetting resin has a viscosity of less than 1000 mPa.s at a temperature of 90°C.

24. Method of manufacturing a composite part according to one of claims 17 to 23, characterized in that it comprises, prior to infusion or injection of said epoxy thermosetting resin, deposition or shaping of said reinforcing material(s) (1), which preferably utilizes the hot tackiness of said at least one thermoplastic porous layer (4,5) present in said reinforcing material(s) (1) and implements heating, preferably carried out at a temperature below 170°C, or even 150°C and preferably is in the range from 100 to 140°C, and more preferably in the range from 100 to 130°C.

25. Composite parts obtained by a manufacturing process as defined in any one of claims 17 to 24.

Images