Reinforcement material including a porous layer made of a reactive thermoplastic polymer and related methods - Patents.com

Abstract

The present invention relates to a reinforcement comprising at least one fibre reinforcement having a thermoplastic porous layer bonded to at least one of the faces of the fibre reinforcement, said thermoplastic porous layer or layers making up to 10% of the total mass of the reinforcement, preferably between 0.5 and 10% of the total mass of the reinforcement, more preferably between 2 and 6% of the total mass of the reinforcement, wherein said thermoplastic porous layer or each of said thermoplastic porous layers comprises or consists of a so-called reactive thermoplastic polymer, said reactive thermoplastic polymer having an amount of -NH 2 >0.15 meq / g of reactive thermoplastic polymer. 2 The present invention relates to a reinforcement material characterized in that it has functional groups and / or has an amount of -COOH functional groups greater than 0.20 meq / g of reactive thermoplastic polymers, and also to a method for producing such a reinforcement material, a preform, a method for producing a composite part using such a reinforcement material, and a composite part using such a reinforcement material.

Description

[Technical field]

[0001] The present invention relates to the technical field of reinforcement materials suitable for the creation of composite parts. More specifically, the subject of the present invention is a reinforcement material suitable for combining with injected or infused resins to manufacture composite parts. [Background technology]

[0002] The manufacture of composite parts or articles, i.e. comprising on the one hand one or more fiber reinforcements, in particular of the unidirectional fiber web type, and on the other hand a matrix, which is in most cases mainly of the thermosetting type and may also comprise one or more thermoplastic substances, can for example be carried out by the so-called "direct" or "LCM" (from English "Liquid Composite Molding") process. The direct process is defined by the fact that the fiber reinforcement or reinforcements are processed in the "dry" state (i.e. without a final matrix) and the resin or matrix is ​​processed separately, for example by injection into a mold containing the fiber reinforcement (the "RTM" process from English "Resin Transfer Molding"), by injection through the thickness of the fiber reinforcement (liquid resin injection or resin film injection), or by manual coating / impregnation using rollers or brushes for each of the separate layers of fiber reinforcement applied successively to the shape. In the manufacture of composite parts, especially in the aviation industry, mass production rates can be high. For example, for the manufacture of single-aisle aircraft, aviation contractors want to be able to manufacture several tens of aircraft per month. Direct processes such as casting or injection molding are of great importance to meet this requirement.

[0003] The RTM, LRI or RFI process generally involves first producing a fiber preform or stack in the shape of the desired finished product, then impregnating this preform or stack with resin to form a matrix. The resin is injected or infused by a temperature pressure differential, and then, once the entire amount of resin required is contained in the preform, the assembly is brought to a higher temperature to carry out a polymerization / crosslinking cycle, thereby resulting in curing.

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

[0005] The resins used to manufacture the parts, especially by injection or infusion, may be thermosetting resins such as epoxies (also known as epoxides). The main drawback of these resins is their brittleness, which results in low impact resistance of the manufactured composite parts. Therefore, the prior art proposes bonding a fiber reinforcement layer with a porous thermoplastic polymer layer, especially a nonwoven fabric (also known as a veil) of thermoplastic fibers. Such solutions have been proposed in particular in the following documents: EP1125728, US6,828,016, US2010 / 003881, WO00 / 58083, WO2007 / 015706, WO2006 / 121961, US6,503,856, US2008 / 7435693, WO2010 / 046609, WO2010 / 061114, EP2547816, US2008 / 0289743, US2007 / 8361262, US2011 / 9371604 and WO2011 / 048340.

[0006] Multiaxial reinforcements, commonly referred to as non-crimp fabrics (NCFs), are also ideally suited for the direct process. Such multiaxial reinforcements, consisting of a stack of several unidirectional webs of reinforcing fibers (in particular carbon, glass or aramid) arranged in several orientations and stitched together, are described in particular in EP 2547816 and WO 2010 / 067003. Here too, a porous polymer layer is usually inserted into the NCF to improve the mechanical properties of the manufactured composite parts.

[0007] However, these solutions have some drawbacks: the porous thermoplastic layers used usually have a high melting point, especially above 150°C, which makes the manufacturing process of these reinforcements expensive. Furthermore, the thermoplastic material constituting the porous layer may interact with the thermosetting resin injected during the manufacture of the composite part, which is more pronounced the lower the melting point of the thermoplastic material constituting the porous layer.

[0008] Among other things, these porous thermoplastic layers can usually melt in the resin during the curing of the composite part. As a result, the thermoplastic porous layer can change the local stoichiometry of the thermosetting resin, which can spread to the fiber reinforcement when it is impregnated with the thermosetting resin. This is something that one wants to avoid, since it leads to a change in the heat resistance properties of the resulting part. It is therefore necessary to find a suitable curing cycle (defined as the rate of temperature rise to the curing temperature of the part and the hold time at the curing temperature) that allows the resin to gel at temperatures below or above the melting temperature of the thermoplastic porous layer, depending on whether the thermoplastic porous layer is maintained as it is or a change in it occurs, resulting in different final properties of the resulting part.

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

[0010] In an attempt to overcome these drawbacks, other solutions have been proposed in the prior art, in which, in order to be able to carry out the fibre-reinforced moulding process at lower cost and in shorter time, the Applicant proposes to use, instead of the thermoplastic porous layer, an epoxy powder, such as that used in the textiles developed under the reference Hexcel Primetex 43098 S 1020 S E01 1F. Such a thermosetting layer, obtained by depositing an epoxy powder with a softening temperature of about 100 °C, makes it possible to manufacture composite parts faster and cheaper, in particular at lower temperatures, since it is possible to carry out low-temperature preforming. Nevertheless, such a technique poses practical problems due to the use of powders that tend to clog the dispensing heads of the automatic dispensing devices used, and does not make it possible, among other things, to achieve satisfactory properties in terms of mechanical strength.

[0011] In patent application WO2019 / 102136, the applicant also proposed to bond a fiber reinforcement layer with a porous thermoplastic polymer layer partially crosslinked under irradiation in order to preserve the beneficial effect on mechanical performance observed when using a reinforcement comprising a porous thermoplastic layer. In particular, due to its partially crosslinked location, the porous layer is only partially meltable or even completely unmeltable in the thermosetting resin, thus avoiding temperature and moisture resistance changes. Furthermore, the use of such a porous thermoplastic polymer layer partially crosslinked under irradiation offers the possibility to carry out the manufacturing process of the reinforcement and its shaping during the manufacture of the composite part at temperatures below 130°C, preferably below 120°C. However, the use of an irradiation process to partially crosslink the thermoplastic material lengthens the entire process and increases the costs.

[0012] The object of the present invention is to provide a new reinforcement for the production of composite parts, in particular by direct processes of the RTM type, which makes it possible to achieve satisfactory mechanical performance and good resistance to temperature stresses, required in particular in the aerospace and aviation industries, without the technical constraints posed by the previous solution previously proposed in WO 2019 / 102136. Summary of the Invention

[0013] Object of the invention The present invention relates to a reinforcement comprising at least one fibre reinforcement having a thermoplastic porous layer bonded (bonded) to at least one of the faces of the fibre reinforcement, said thermoplastic porous layer(s) making up to 10% of the total mass of the reinforcement, preferably between 0.5 and 10% of the total mass of the reinforcement, more preferably between 2 and 6% of the total mass of the reinforcement, wherein said thermoplastic porous layer or layers present each comprise a so-called reactive thermoplastic polymer or consist of one or more reactive thermoplastic polymers, the 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.

[0014] In the context of the present invention, due to the reactive -NH2 and COOH functional groups present in sufficient amounts on the reactive thermoplastic polymer of the porous layer present in the reinforcement, it can react in a controlled manner with the epoxy resin during curing, which makes it possible to maintain a certain integrity in the thermoplastic layer, thus reducing its sensitivity to temperature exposure as well as improving the temperature properties of the material used in the aerospace industry.

[0015] Advantageously, in the reinforcement according to the invention, said reactive thermoplastic polymer has -NH2 functional groups 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, more preferably in the range from 0.20 to 0.95 meq / g of reactive thermoplastic polymer, and / or has -COOH functional groups 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, more preferably in the range from 0.20 to 0.95 meq / g of reactive thermoplastic polymer.

[0016] According to a preferred embodiment, the reactive thermoplastic polymer of the thermoplastic porous layer(s) present in the reinforcement has a melting temperature below 170°C, or even below 150°C, preferably in the range of 100-140°C, more preferably in the range of 100-130°C.

[0017] In fact, the reaction of the thermoplastic polymer of the porous layer with the injected or infused resin allows the use of a porous layer with a low melting temperature, and as a consequence, also lower temperatures during the production and molding of the reinforcement, thus leading to savings in terms of costs and time. A further advantage is that the melting temperature of the reactive thermoplastic polymer of the porous layer can be below 170°C, or even below 150°C, so that all stages of the manufacturing process before the addition of the resin finally required to produce the part (from the preparation of the dry material through its deposition and preform) can be carried out at temperatures below 170°C, or even better below 150°C, or even below. Such a porous layer comprising a reactive thermoplastic polymer with a lower melting point (melting temperature) allows the reinforcement joining the porous layer(s) and the fiber reinforcement(s) to be manufactured at temperatures compatible with automated manufacturing processes, in particular fiber placement and thermoforming of flat-laid preforms.

[0018] A second object of the present invention is therefore to combine the beneficial effect of using a thermoplastic porous layer on the impact resistance performance with the possibility of carrying out all steps in the manufacturing process prior to the infusion or injection of the resin at temperatures below 170°C, or even below 150°C or below 140°C, these temperatures possibly being in the range of 100-130°C, or even 80-140°C or even 80-130°C.

[0019] In the context of the present invention, in the reinforcement, it is particularly preferred that the reactive thermoplastic polymer is a polyamide or copolyamide carrying said -NH2 and / or -COOH functional groups.

[0020] In particular, said thermoplastic porous layer(s) present comprises -NH2 functional groups in an amount greater than 0.15 meq / g of porous layer and / or -COOH functional groups in an amount greater than 0.20 meq / g of porous layer.

[0021] According to a particular embodiment, the reactive thermoplastic polymer has a number average molecular weight Mn greater than 4000 g / mol.

[0022] In the reinforcement according to the invention, the fiber reinforcement can take different forms: in some embodiments, the fiber reinforcement is a unidirectional web of reinforcing threads, a woven fabric of reinforcing threads, or a stack of unidirectional webs of reinforcing threads bonded together by any other physical means such as sewing or needling.

[0023] The fibre reinforcement may in particular consist of glass fibres, aramid fibres or preferably carbon fibres.

[0024] According to a particular embodiment, the reinforcement according to the invention consists of a unidirectional web of reinforcing threads corresponding to a fibrous reinforcement having a thermoplastic porous layer as defined within the context of the present invention bonded to at least one of its faces, preferably said fibrous reinforcement consists of a unidirectional web of reinforcing threads corresponding to a fibrous reinforcement having a thermoplastic porous layer as defined within the context of the present invention bonded to each of its faces, and the thermoplastic porous layers present on each of the faces of the unidirectional web of reinforcing threads are identical.

[0025] The thermoplastic porous layer(s) of the reinforcement according to the invention may have high temperature adhesion, and thanks to the high temperature adhesion of the thermoplastic porous layer, bonding between the fiber reinforcement and the porous layer may be achieved.

[0026] According to some embodiments, the reinforcement according to the invention consists of a stack of unidirectional webs of reinforcing threads as fiber reinforcement oriented in different directions, with at least one thermoplastic porous layer as defined within the context of the present invention interposed between two unidirectional webs of reinforcing threads and / or present on the surface of the stack. Such a stack can be in the form of a stack of unidirectional webs of reinforcing threads in the arrangement (CP / R) n (CP) m or (CP / R / CP) n where CP denotes a porous thermoplastic layer as defined within the context of the present invention, R is a unidirectional web, n is an integer equal to or greater than 1, and m is 0 or 1. In such a stack, the unidirectional webs of reinforcing yarns can be joined to each other or to at least one of the thermoplastic porous layers by sewing, knitting or needling.

[0027] In the reinforcement according to the invention, the thermoplastic porous layer(s) present are in particular porous films, lattices, powder deposits, woven fabrics or, preferably, nonwoven fabrics or veils.

[0028] Another object of the present invention is to provide a method for the preparation of ... pharmaceutical composition comprising the steps of: a1) providing a fiber reinforcement; a2) providing at least one porous thermoplastic layer which comprises or consists of a so-called reactive thermoplastic polymer, the reactive thermoplastic polymer having -NH2 functional groups in an amount greater than 0.15 meq / g of reactive thermoplastic polymer and / or the reactive thermoplastic polymer having -COOH functional groups in an amount greater than 0.20 meq / g of reactive thermoplastic polymer; a3) bonding a fiber reinforcement to at least one porous thermoplastic layer; A process for preparing the reinforcement material according to the invention, comprising:

[0029] In such a preparation process, the bonding of step a3) is advantageously achieved by applying at least one porous thermoplastic layer to the fiber reinforcement, said application being accompanied or followed by heating of said reactive thermoplastic polymer to cause its softening or melting and then cooling, said heating being preferably carried out at a temperature below 170° C., or even below 150° C., more preferably in the range of 80-140° C., in particular 100-140° C., preferably in the range of 80-130° C., in particular 100-130° C. Of course, the thermoplastic polymer(s) of the thermoplastic porous layer(s) are selected so as to soften or melt at such temperatures.

[0030] Another object of the invention is a preform consisting at least in part of one or more reinforcements according to the invention.

[0031] Another object of the invention relates to a process for manufacturing a composite part from at least one reinforcement according to the invention, in which an epoxy thermosetting resin is injected or impregnated into said reinforcement according to the invention, into a stack of several reinforcements according to the invention, or into a preform according to the invention.

[0032] Advantageously, the process for manufacturing a composite part according to the invention comprises a heat treatment step comprising heating to a temperature Ta that results in crosslinking of the epoxy thermosetting resin and consolidation of the composite part, once the epoxy thermosetting resin has been injected or infused into said reinforcement or said stack, during which the epoxy resin reacts with at least a portion of the -NH2 and / or -COOH functional groups present on the reactive thermoplastic polymer of the thermoplastic porous layer(s).

[0033] In particular, the gelation of epoxy resins occurs during the heat treatment process, and -NH2 and / or -COOH functional groups react with the resin before it gels.

[0034] According to a first variant of the manufacturing process of the composite part according to the invention, said temperature Ta is higher than the melting temperature of said reactive thermoplastic polymer of said at least one thermoplastic porous layer. In particular, heating to said temperature Ta is carried out during a heat treatment step for a period between 5 minutes and 2 hours. In most cases, the heat treatment step comprises a temperature increase stage up to said temperature Ta, in particular at a rate of 0.1 to 10 ° C / min. Preferably, the viscosity of the epoxy thermoset resin increases between the melting of said reactive thermoplastic polymer of said at least one thermoplastic porous layer and the onset of crosslinking of the epoxy thermoset resin. More precisely, it can be said that the increasing viscosity is the viscosity 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 embodiment variant, during the heat treatment step, gelation of the epoxy thermosetting resin occurs more quickly than if it were subjected to the heat treatment step alone. In particular, when heated to a temperature Ta, gelation of the epoxy thermosetting resin occurs after a heating time of 5 to 60 minutes.

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

[0037] According to a second variant of the manufacturing process of the composite part according to the invention, the heating is carried out at said temperature Ta, which is below the melting temperature of the reactive thermoplastic polymer of the thermoplastic porous layer. In particular, heating at said temperature Ta for 5 minutes to 5 hours is carried out during the heat treatment step. Preferably, the gelling of the thermosetting epoxy resin occurs faster than if it were subjected to the heat treatment step alone. Here too, the heat treatment step generally comprises a temperature increase stage up to said temperature Ta, in particular at a rate of 0.1 to 10 ° C / min.

[0038] According to a second variant of the manufacturing process of the composite part according to the invention, in which the temperature Ta is below 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 at least equal to 100°C, advantageously in the range from 100 to 150°C.

[0039] Also advantageously, according to a second variant of the manufacturing process of the composite part according to the invention, the temperature Ta is below the melting temperature of the reactive thermoplastic polymer of the at least one thermoplastic porous layer, said reactive thermoplastic polymer having a melting temperature higher than 120°C.

[0040] Whatever the variant used to manufacture the composite part according to the invention, the temperature Ta is in the range of 120 to 220 °C, preferably in the range of 160 to 220 °C, more preferably in the range of 170 to 190 °C, typically 180 °C.

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

[0042] In addition, the process for manufacturing a composite part according to the present invention may comprise, prior to the infusion or injection of said epoxy thermoset resin, deposition or moulding of said reinforcement(s), preferably taking advantage of the high temperature tack of said at least one thermoplastic porous layer present in said reinforcement(s), carrying out a heating preferably carried out at a temperature below 170°C, or even below 150°C, preferably in the range of 100-140°C, more preferably in the range of 100-130°C.

[0043] The invention also encompasses a composite part obtained by a manufacturing process as defined within the context of the present invention.

[0044] The present invention therefore relates to a composite part comprising a thermosetting epoxy matrix including at least one reinforcement comprising at least one fibre reinforcement with a thermoplastic porous layer bonded to at least one of the faces of the fibre reinforcement, said thermoplastic porous layer(s) making up to 10% of the total mass of the reinforcement, preferably between 0.5 and 10% of the total mass of the reinforcement, more preferably between 2 and 6% of the total mass of the reinforcement, in which a covalent bond exists between the thermoplastic polymer present in the thermoplastic porous layer(s) and the thermosetting epoxy matrix, said covalent bond resulting from the reaction of -NH2 and / or -COOH functional groups present on said thermoplastic polymer and on the epoxy resin.

[0045] definition By "porous layer" is meant a permeable layer that allows a liquid, such as a resin, to pass through the material when it is injected or poured therein during the preparation of a preform or a composite part. In particular, the open area of ​​such a layer ranges from 30 to 99%, preferably from 40 to 70%. Such an open area, which is a conventional parameter for characterizing such a porous layer, can be measured using any technique known to the skilled artisan, in particular using the method described in WO2011 / 086266. Examples of porous layers include porous films, lattices made by interwoven threads, layers obtained by powder deposition, woven fabrics and nonwoven fabrics. However, in the context of the present invention, whatever the method described, it is preferred to use a porous layer in the form of a nonwoven fabric, also known as a veil, which makes it possible to manufacture composite parts with particularly sufficient mechanical properties.

[0046] The porous layer is said to be thermoplastic because it contains a thermoplastic polymer, advantageously consisting essentially or exclusively of a thermoplastic polymer or a blend of thermoplastic polymers. If the porous layer comprises several polymers, these may be present in a mixture within the layer, in particular within the porous film, powder or fiber forming the porous layer. To form the porous layer, it is also possible to use fibers having a core and seeds around the core, the core and the seeds being in different polymers, in particular one or more reactive thermoplastic polymers as defined within the context of the present invention forming the seeds. The porous layer may also comprise a thermoplastic binder in one or more reactive thermoplastic polymers as defined within the context of the present invention, in particular having a lower melting point than the rest of the polymer(s) forming the porous layer. A porous layer is said to consist essentially of a thermoplastic polymer or a blend of such polymers when the thermoplastic polymer or a blend of such polymers represents at least 90% by weight, preferably at least 95% by weight, of the mass of the thermoplastic porous layer. In this specification, the thermoplastic porous layer may be referred to simply as a "porous layer" for the sake of simplicity. In particular, the porous layer may consist essentially or solely of reactive thermoplastic polymers, in particular selected from polyesters, copolyesters, polyamide-imides, polyethersulfones, polyimides, polyetherketones, polymethylmethacrylates, aromatic polyethers, polyamides and copolyamides, having -NH2 functionality in an amount greater than 0.15 meq / g of the reactive thermoplastic polymer and / or -COOH functionality in an amount greater than 0.20 meq / g of the reactive thermoplastic polymer, or a mixture of such polymers. Thus, such polymers may contain either -NH2 functionality in an amount greater than 0.15 meq / g of the reactive thermoplastic polymer, or -COOH functionality in an amount greater than 0.20 meq / g of the reactive thermoplastic polymer, or -NH2 functionality in an amount greater than 0.15 meq / g of the reactive thermoplastic polymer and -COOH functionality in an amount greater than 0.20 meq / g of the reactive thermoplastic polymer.

[0047] In the context of the present invention, when referring to meq / g of reactive thermoplastic polymer, the mass of reactive thermoplastic polymer includes the reactive functional groups present on said polymer.

[0048] In the context of the present invention, for the sake of simplicity, reactive thermoplastic polymers, in particular those selected from polyesters, copolyesters, polyamide-imides, polyethersulfones, polyimides, polyetherketones, polymethylmethacrylates, aromatic polyethers, polyamides and copolyamides, having -NH2 functional groups in an amount greater than 0.15 meq / g of reactive thermoplastic polymer and / or -COOH functional groups in an amount greater than 0.20 meq / g of reactive thermoplastic polymer, can simply be called reactive thermoplastic polymers. Thus, said reactive thermoplastic polymers can have -NH2 functional groups in an amount greater than 0.15 meq / g of reactive thermoplastic polymer, or have -COOH functional groups in an amount greater than 0.20 meq / g of reactive thermoplastic polymer, or have both -NH2 functional groups in an amount greater than 0.15 meq / g of reactive thermoplastic polymer and -COOH functional groups in an amount greater than 0.20 meq / g of reactive thermoplastic polymer. In the reactive thermoplastic polymers used in the context of the present invention, the -NH2 and / or -COOH functional groups, which may be described as free or reactive functional groups, are present on said thermoplastic polymer in an amount sufficient to achieve a covalent reaction with the epoxy resin used during the manufacture of the composite part, in order to maintain the integrity or specific integrity of the thermoplastic porous layer or at least limit its mobility in the resins injected or poured during the subsequent manufacture of the composite part, thus without adversely affecting the mechanical properties of the composite part obtained.

[0049] In particular, the reactive thermoplastic polymers used in the context of the present invention comprise free -COOH functional groups in an amount of more than 0.20 meq / g of reactive thermoplastic polymer, in particular in an amount of 0.22 meq / g or more, 0.25 meq / g or more, 0.30 meq / g or more or 0.40 meq / g or more of reactive thermoplastic polymer, preferably in the range of 0.20 to 1 meq / g of reactive thermoplastic polymer, more preferably in the range of 0.20 to 0.95 meq / g of reactive thermoplastic polymer, especially 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, the reactive thermoplastic polymers used in the context of the present invention contain free -NH2 functional groups in an amount of more than 0.20 meq / g of reactive thermoplastic polymer, in particular in an amount of 0.25 meq / g or more, 0.30 meq / g or more or 0.34 meq / g or more of reactive thermoplastic polymer, preferably in the range of 0.20 to 1 meq / g of reactive thermoplastic polymer, more 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. Said amounts of -COOH or -NH2 functional groups can be present on the reactive thermoplastic polymer alone or together in any possible combination.

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

[0051] Said additional thermoplastic polymer may have a melting temperature below 170° C., or even below 150° C., preferably in the range of 100-140° C., more preferably in the range of 100-130° C. In such a case, advantageously, the reactive porous layer consists of at least 70% by weight, preferably at least 80% by weight, more preferably at least 90% by weight of one or more reactive thermoplastic polymers as defined in the context of the present invention.

[0052] It is also possible to use fibres having a core made of one or more so-called additional thermoplastic polymers having a melting temperature below 170°C, or even below 150°C, preferably in the range of 100-140°C, more preferably in the range of 100-130°C, said core being surrounded by a sheath, the sheath being constituted by one or more reactive thermoplastic polymers as defined within the context of the present invention. Said additional thermoplastic polymers may also have a melting temperature above 170°C, or even above 180°C, preferably in the range of 180-220°C. In such a case, advantageously, reactive thermoplastic polymer(s) as defined within the context of the present invention may be present in the porous layer to act as a binder, in particular to bond the thermoplastic porous layer to the fibre reinforcement, and reactive thermoplastic polymer(s) as defined within the context of the present invention may be present in the porous layer in smaller amounts, in particular in an amount corresponding to 10-30% of the mass of the porous layer.

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

[0054] In the context of the present invention, and whatever the implementation variant, the reactive thermoplastic polymer is preferably a polyamide or copolyamide, having an amount of -NH2 functional groups greater than 0.15 meq / g of reactive thermoplastic polymer and / or an amount of -COOH functional groups greater than 0.20 meq / g of reactive thermoplastic polymer, in particular the amounts of -NH2 functional groups and / or -COOH functional groups specified above in the more general description of the reactive thermoplastic polymer.

[0055] The reactive thermoplastic polymers used in the context of the present invention have a sufficient amount of reactive functional groups that make it possible to react with the epoxy thermosets conventionally used in the manufacture of composite parts. As will become clear from the examples, such a reaction makes it possible to impart particularly advantageous properties to the composite parts obtained, in particular improving their resistance to temperature and moisture, while preserving satisfactory mechanical properties that are important for composite parts intended for the aviation and aerospace industries.

[0056] The amount of reactive -COOH or -NH2 functional groups present can be assessed by potentiometric titration. The amount of -COOH functional groups can be determined by titration with tetra-n-butylammonium hydroxide ((C4H9)4N + OH - The amount of -NH2 functional groups is measured by an acid-base assay of the porous layer using 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 context of the present invention is advantageously a polyamide or copolyamide. In particular, the reactive thermoplastic polymer is in the form of a branched polyamide or copolyamide with -NH2 or -COOH functional groups at the end of the branch chain so as to achieve the amount of functional groups targeted within the context of the present invention. In particular, polyamide 6 (polycaprolactam), polyamide 6.6 (nylon), polyamide 6.10 (polyhexamethylene sebacamide), polyamide 6.12 (polyhexamethylene dodecane diamide), polyamide 11 (polyundecane amide), polyamide 12 (polylauroamide) are mentioned. Advantageously, the reactive thermoplastic polymer belongs to the copolyamide family, in particular the copolymers of caprolactam and / or lauryllactam and / or hexamethylene diamine with adipic acid.

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

[0059] Conventionally, polyamides or copolyamides can be obtained from several raw materials, such as lactams, aminocarboxylic acids, diamines or triamines, dicarboxylic acids, etc., as described in EP3197974, FR2883878 and US2010 / 0032629. The production of copolyamides requires the selection of at least two of these products. The amount of diamine and dicarboxylic acid used controls the amine and acid functional groups present in the polyamide or copolyamide.

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

[0061] Aminocarboxylic acids include amino-undecanoic acid, aminododecanoic acid, and the like.

[0062] Examples of dicarboxylic acids include adipic acid, isophthalic acid, sebacic acid, dodecanedioic acid, seraphthalic acid, and the like.

[0063] Examples of diamines include those having 6 to 12 carbon atoms, aryl and saturated rings, such as hexamethylenediamine, tetramethylenediamine, octamethylenediamine, decamethylenediamine, piperazine, etc.

[0064] Examples of copolyamide linkages include caprolactam and lauryllactam (6 / 12), caprolactam, lauryllactam and amino 11-undecanoic acid (6 / 11 / 12), caprolactam, adipic acid and hexamethylenediamine (6 / 66), caprolactam, lauryllactam, adipic acid and hexamethylenediamine (6 / 12 / 66), caprolactam, lauryllactam, amino 11-undecanoic acid, adipic acid and hexamethylenediamine (6 / 66 / 11 / 12).

[0065] In particular, acids such as adipic acid (for the introduction of -COOH functional groups) and / or amines such as hexamethylenediamine (for the introduction of amine functional groups) act in appropriate amounts to tailor and achieve the desired number of reactive functional groups.

[0066] More generally, for all thermoplastic polymers, the preferred solution for introducing amine-NH2 or acid-COOH functional groups is plasma treatment. The implementation of such treatments is described in particular 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-C 4-208; in the publication Plasma grafting - a method to obtain monofunctional surfaces, C. Oehr, M. Muller, B. Elkin, D. Hegemann, U. Vohrer, Surface and Coatings Technology, Vol. 116-119, September 1999, pages 25-35; US2021 / 0086226; or WO2019 / 243631.

[0067] Thermoplastic polymers are commercially available that have the desired number of -NH2 amine and / or -COOH acid functional groups or to which the desired number of amine and / or acid functional groups can be tailored or introduced by plasma treatment.

[0068] In the case of polyesters and copolyesters, such polymers are marketed by Evonik Industries AG (Germany), Eastmann Chemical Company (USA), Arkema (France), EMS-Grivory (Switzerland) and Toyobo Co., Ltd. (Japan).

[0069] In the case of polyamide-imides, for example, such polymers are marketed by Solvay (Belgium), Toyobo Co., Ltd. (Japan) and Mitsubishi Chemical (Switzerland).

[0070] In the case of polyethersulfone, such polymers are marketed by BASF (Germany), Sumitomo Chemical Co., Ltd. (Japan) and Ensinger Plastics (Germany).

[0071] In the case of polyimides, such polymers are commercially available from companies such as DuPont (USA), Evonik Industries AG (Germany) and Huntsmann Corporation (USA).

[0072] In the case of polyetherketones, such polymers are marketed by Arkema (France), Solvay (Belgium), Evonik Industries AG (Germany) and Victrex (Great Britain).

[0073] Finally, in the case of polymethyl methacrylate, such polymers are marketed by Evonik Industries AG (Germany) and Kuraray Co., Ltd. (Japan).

[0074] The reactive thermoplastic polymer in the porous layer can be an amorphous polymer, but is preferably a semi-crystalline polymer. Semi-crystalline polymers have a glass transition temperature lower than their melting point, which makes them easier to soften and therefore easier to bond to the fiber reinforcement or to preform and / or deposit the reinforcement according to the invention. Furthermore, semi-crystalline polymers have an organized molecular structure, particularly with aligned chains, which gives them better mechanical properties than amorphous polymers, which have less organized molecular structure.

[0075] In describing the melting temperature of the thermoplastic polymer or porous layer, reference is made to the peak melting temperature as measured by Differential Scanning Calorimetry (DSC) at a temperature ramp of 10° C. / min.

[0076] "A fiber reinforcement with a porous layer bonded to at least one of its faces" means that the fiber reinforcement is bonded to at least one porous layer applied to one of its faces. In particular, this bond is achieved by adhesive bonding, thanks to the high-temperature adhesion of the porous layer due to its thermoplasticity. In particular in the case of stacks comprising several fiber reinforcements and several porous layers, this bond can also be completed or replaced by mechanical bonding of the sewing or knitting type, or by any other physical means (needling, etc.).

[0077] The reinforcement according to the invention can be described as "dry" since it is intended to be bonded with a binder, in particular a thermosetting resin, for the manufacture of a composite part, and the mass of the porous layer(s) present in the reinforcement according to the invention does not exceed 10% of the total mass of the reinforcement, preferably representing 0.5-10%, more preferably 2-6% of the total mass of the reinforcement according to the invention.

[0078] More generally, the reinforcement according to the invention is a so-called dry material, i.e. suitable for manufacturing composite parts bonded with resin, in particular with thermosetting epoxy-based resin. The reinforcement according to the invention comprises a polymer part which represents up to 10% of the total mass of the reinforcement, preferably between 0.5 and 10% of the total mass of the reinforcement, more preferably between 2 and 6% of the total mass of the reinforcement. This polymer part comprises or consists of the porous thermoplastic layer(s) present in the reinforcement according to the invention.

[0079] In particular, according to the invention, the thermoplastic porous layer(s) present in the reinforcement consist of one or more reactive thermoplastic polymers selected in particular from polyesters, copolyesters, polyamide-imides, polyethersulfones, polyimides, polyetherketones, polymethylmethacrylates, aromatic polyethers, polyamides and copolyamides as defined within the context of the present invention, preferably from polyamides and copolyamides as defined within the context of the present invention.

[0080] The term "nonwoven", which may also be called "veil", is generally taken to mean a set of continuous or short fibers arranged randomly. These nonwovens or veils can be produced, for example, by dry-laid, wet-laid or spun-laid processes, for example by extrusion ("spunbond"), meltblown extrusion ("Meltblown"), fiberizing spray applicators ("Meltblown") or solvent spinning ("electrospinning", "flash spinning", "force spinning"), all of which are well known to those skilled in the art. In particular, the fibers constituting the nonwoven can have an average diameter ranging from 0.5 to 70 μm, preferably from 0.5 to 20 μm. The nonwoven can consist of short or, preferably, continuous fibers. In the case of short-fiber nonwovens, the fibers can be, for example, between 1 and 100 mm long. The nonwoven provides a random, preferably isotropic, covering.

[0081] Advantageously, the nonwoven or nonwoven fabrics present in the reinforcement according to the invention have a density of between 0.2 and 20 g / m 2 The thickness of the nonwoven fabric in the reinforcement according to the invention may vary according to the mode of bonding with the fiber reinforcement. Preferably, the nonwoven fabric or nonwoven fabrics present in the reinforcement according to the invention each have a thickness of 0.5 to 50 microns, preferably 3 to 35 microns, after bonding with the fiber reinforcement, if the bonding is carried out by applying heat and pressure to take advantage of the high temperature adhesion of the nonwoven fabric. If the bonding is achieved by mechanical means such as sewing, knitting or needling, the thickness of the nonwoven fabric may be greater than 50 microns, in particular in the range of 50 to 200 microns. The properties of these nonwoven fabrics can be measured according to the methods described in WO2010 / 046609.

[0082] By "fibrous reinforcement" is meant a layer of reinforcing fibers which may in particular be in the form of a woven or unidirectional web of reinforcing fibers. The reinforcing fibers are generally glass, carbon, aramid or ceramic fibers, with carbon fibers being particularly preferred.

[0083] Generally, in the field, the term "unidirectional web or layer of reinforcing fibers" refers to a web consisting solely or nearly solely of reinforcing fibers or threads deposited in the same direction so as to extend substantially parallel to one another. In the case of a web of reinforcing threads, it extends in a parallel or substantially parallel general direction. In particular, according to a particular embodiment of the invention, the unidirectional web does not include weft threads that weave the reinforcing threads or fibers together, or even seams intended to give the unidirectional web cohesion before joining with another layer, in particular a thermoplastic porous layer. In particular, this avoids any undulations in the unidirectional web. The unidirectional web of reinforcing fibers can consist of a single thread, but more frequently it consists of several aligned threads arranged side by side. The threads are arranged so as to provide a total or nearly total coverage over the entire surface of the web. In this case, in each of the webs constituting the intermediate material, the threads are preferably arranged between the edges so as to minimize or even avoid gaps or overlaps.

[0084] In unidirectional webs, the reinforcing yarn(s) are preferably not bonded with a polymeric binder and are therefore described as dry, i.e., they are not impregnated, coated, or bonded with any polymeric binder before bonding with the thermoplastic porous layer(s). However, the reinforcing fibers are usually characterized by a standard sizing percentage of up to 2% by weight. This is particularly suitable for the manufacture of composite parts by resin diffusion using the direct process. In unidirectional webs, the reinforcing yarn(s) can be twisted yarns.

[0085] The fibres constituting the fibre reinforcement used in the context of the present invention are preferably continuous. The fibre reinforcement generally consists of several threads.

[0086] In particular, the carbon yarn consists of a set of filaments and generally contains between 1,000 and 80,000 filaments, advantageously between 12,000 and 24,000 filaments. Particularly preferred within the context of the present invention are carbon yarns of 1 to 24K, for example 3K, 6K, 12K or 24K, preferably 12 and 24K. For example, the carbon yarns present in the fiber reinforcement used in the context of the present invention have a titre of 60 to 3800 Tex, preferably 400 to 900 Tex. The fiber reinforcement can be made of any kind of carbon yarn, for example, high resistance (HR) yarn with a tensile modulus of 220-241 GPa and a tensile stress at break of 3450-4830 MPa, intermediate modulus (IM) yarn with a tensile modulus of 290-297 GPa and a tensile stress at break of 3450-6200 MPa, and high modulus (HM) yarn with a tensile modulus of 345-448 GPa and a tensile stress at break of 3450-5520 Pa (according to ASM Handbook, ISBN 0-87170-703-9, ASM International 2001). When the unidirectional reinforcement web is made of carbon yarn, the unidirectional reinforcement web can be made of 126 g / m 2 ~500g / m 2 , especially 126~280g / m 2The composition may have a basis weight in the range of 1000 to 2000 gram.

[0087] Reinforcement according to the invention The invention can be applied to different types of reinforcements, i.e. simple reinforcements comprising single fibre reinforcements intended to be stacked on top of each other, or more complex reinforcements comprising several stacked fibre reinforcements which can be used alone or also in stacked form.

[0088] In particular, examples of simple reinforcements include those consisting of a unidirectional web of reinforcing fibers corresponding to the fibrous reinforcement, to which a porous thermoplastic layer comprising or consisting of a reactive thermoplastic polymer as provided within the context of the present invention is bonded to at least one of the faces of the fibrous reinforcement. In order to have a symmetrical material 1 as shown in FIG. 1, a unidirectional web 2 of fibrous reinforcement, in particular reinforcing fibers 3, is bonded to each of the faces of the unidirectional web of reinforcing fibers with a thermoplastic porous layer 4, 5 comprising or consisting of one or more reactive thermoplastic polymers as provided within the context of the present invention, the porous layers present on each face of the unidirectional web of reinforcing fibers being preferably identical. In the context of the present invention, the thermoplastic porous layer comprising or consisting of one or more reactive thermoplastic polymers has high-temperature adhesion, and the bonding between the fibrous reinforcement and the thermoplastic porous layer is advantageously achieved thanks to the high-temperature adhesion of the porous layer. This adhesion is due to the thermoplasticity of the porous layer. Of course, it may also be possible to use the high-temperature adhesion of the porous layer to replace or complete this bonding by sewing or knitting, or by any other means of physical bonding type (needling, etc.).

[0089] The reinforcement may also be in the form of a stack of such reinforcements, i.e. (CP / R / CP) nwhere CP denotes a thermoplastic porous layer comprising or consisting of one or more reactive thermoplastic polymers as defined within the context of the present invention, in particular nonwovens, R denotes a unidirectional web and n is an integer equal to or greater than 1. Preferably, all porous thermoplastic CP layers have the same or even identical basis weight and / or all R fiber reinforcements have the same or even identical basis weight. It is also possible that the two outer CP layers of the stack have a basis weight equal to twice the basis weight of the other inner CP layer.

[0090] Examples of more complex reinforcements include those consisting of a stack of unidirectional reinforcing fiber webs oriented in different directions, with at least one porous thermoplastic layer, comprising or consisting of one or more reactive thermoplastic polymers as provided within the context of the present invention, interposed between the two unidirectional reinforcing fiber webs and / or present at the surface of the stack. According to a first variant, such materials can be in the form of a laminate of the arrangement (CP / R) n or (CP / R) n The laminate may consist of a stack corresponding to / CP, where CP denotes a porous thermoplastic layer comprising or consisting of a reactive thermoplastic polymer as defined within the context of the present invention, R denotes a unidirectional web as described within the context of the present invention, n denotes an integer, preferably all CP layers have the same basis weight or are even the same. In particular, in such a stack, the fiber reinforcement R is a unidirectional web of reinforcing fibers, in particular carbon fibers, preferably of the same basis weight. Such materials are known as NCF (Non-Crimp Fabrics). Generally, in the case of NCF, the unidirectional webs of reinforcing fibers are joined to each other and to the porous thermoplastic layer(s) present by sewing or knitting. Of course, it may be possible to replace or even complete this joining by sewing or knitting, by adhesion achieved by the high-temperature adhesion of the thermoplastic porous layer, or by any other means of physical bonding type (needling, etc.).

[0091] In particular, in the case of NCF, the reinforcement according to the invention is composed of unidirectional webs extending along different orientations selected from the angles 0°, 30°, 45°, 60°, 90°, 120°, 135°. All or part of the unidirectional webs may have different orientations. By way of example, the reinforcement according to the invention may be composed of the following stacks: 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 feed direction for producing the reinforcement according to the invention. In the case of joining by sewing or knitting, the general direction of the sewing or knitting threads also generally corresponds to 0°. Such multiaxial production is well known and includes general techniques such as those described, for example, in the book "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 processes and devices for producing multiaxial fiber webs.In particular, the unidirectional webs may be formed before the multi-axes are made or may be laid in-line. The unidirectional webs may be sewn or knitted together using stitches that run parallel to one another. In particular, the sewing or knitting stitches are spaced apart in the same line, preferably at the same pitch, with a pitch of 1-20 mm, more preferably 2-12 mm. Similarly, two successive sewing or knitting lines are spaced apart, for example, by 2-50 mm, preferably 5-15 mm. Preferably, all successive sewing lines in a series of parallel lines are spaced apart by the same distance. Polyester, copolyester, polypropylene (PP), polyethylene (PE), polyphenylene sulfide (PPS), polyethylene naphthalate (PEN), liquid crystal polymer (LCP), polyketone, polyamide, crosslinkable thermoplastics, carbon, glass, basalt, silica and mixtures thereof are examples of sewing thread materials that are particularly suitable within the context of the present invention. Polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, polylactic acid and copolymers thereof are examples of polyesters that can be used. The yarns have a fineness in the range of 5 to 150 dTex, in particular less than 30 dTex, measured for example according to standard EN ISO 2060. For details of structures that can be used in NCF type materials, see documents such as EP2547816 or WO2010 / 067003.

[0092] Whatever the arrangement of the reinforcement according to the invention, according to a particular embodiment, said thermoplastic porous layer(s) present comprise -NH2 functional groups in an amount of more than 0.15 meq / g of porous layer and / or -COOH functional groups in an amount of more than 0.20 meq / g of porous layer. In particular, said thermoplastic porous layer(s) present comprise free -COOH functional groups in an amount of more than 0.20 meq / g of thermoplastic porous layer, in particular in an amount of 0.22 meq / g or more, 0.25 meq / g or more, 0.30 meq / g or more or 0.40 meq / g or more of thermoplastic porous layer, preferably in the range of 0.20 to 1 meq / g of thermoplastic porous layer, more preferably in the range of 0.20 to 0.95 meq / g of thermoplastic porous layer, especially 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, said thermoplastic porous layer(s) present comprise free -NH2 functional groups in an amount greater than 0.20 meq / g of thermoplastic porous layer, in particular in an amount of 0.25 meq / g or more, 0.30 meq / g or more or 0.34 meq / g or more of thermoplastic porous layer, preferably in the range of 0.20 to 1 meq / g of thermoplastic porous layer, more 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. Said amounts of -COOH functional groups or -NH2 functional groups can be present alone or together in any possible combination on the thermoplastic porous layer.

[0093] Process for preparing the reinforcement material according to the invention In the context of the present invention, the reinforcement material according to the invention can be produced by the following sequential steps: a1) providing a fiber reinforcement; a2) providing at least one thermoplastic porous layer comprising or consisting of a reactive thermoplastic polymer as defined within the context of the present invention, a3) bonding the fiber reinforcement to at least one thermoplastic porous layer; The compound can be prepared by carrying out the steps:

[0094] In particular, step a3) can be achieved by applying at least one thermoplastic porous layer to the fiber reinforcement, said application being in most cases accompanied by heating causing softening or melting of said reactive thermoplastic polymer of said at least one thermoplastic porous layer or said application being followed by heating and then cooling. In particular, such bonding can be achieved at a temperature between 22 and 200°C, preferably between 50 and 180°C, and is carried out under ambient air by applying the thermoplastic porous layer to the fiber reinforcement, for example by applying pressure thereto. Advantageously, said reactive thermoplastic polymer of said thermoplastic porous layer(s) present in the reinforcement has a melting temperature below 170°C, or even below 150°C, preferably in the range of 100 to 140°C, more preferably in the range of 100 to 130°C. In particular, said thermoplastic porous layer(s) present has a melting temperature below 170°C, or even below 150°C, preferably in the range of 100 to 140°C, more preferably in the range of 100 to 130°C. Bonding of the thermoplastic porous layer to the fiber reinforcement using such reactive thermoplastic polymers due to the high temperature adhesion of the thermoplastic porous layer can be achieved by heating to a temperature below 170°C, or even below 150°C, preferably in the range of 100 to 140°C, more preferably in the range of 100 to 130°C.

[0095] Step a3) can also be performed by sewing, knitting, needling or any other suitable means for bonding the fiber reinforcement and the thermoplastic porous layer together.

[0096] In particular, when the fiber reinforcement according to the invention corresponds to a stack of unidirectional webs of reinforcing threads joined together, in particular by needling-type sewing or any other physical means, step a1) consists of providing several fiber reinforcements, which are unidirectional webs of reinforcing threads, and step a3), during which said fiber reinforcements and at least one thermoplastic porous layer are bonded together, in particular by needling-type sewing or any other physical means, to produce a stack of unidirectional webs of reinforcing threads joined together. Step a'' can include both bonding achieved by sewing, knitting, needling or any other suitable means allowing the fiber reinforcement and the thermoplastic porous layer to be bonded together, and bonding achieved by applying at least one thermoplastic porous layer to at least one of the unidirectional webs of reinforcing threads, said application usually being accompanied by heating to soften or melt said reactive thermoplastic polymer of said at least one porous thermoplastic layer, or said application being followed by heating, said heating being followed by cooling. Within the context of the present invention, in the case of more complex materials comprising at least one thermoplastic porous layer between two fiber reinforcements, in particular in the case of NCF, which comprises or consists of one or more reactive thermoplastic polymers as provided, the process can be carried out in particular in the sequence (CP / R) as defined above. n or (CP / R) n In accordance with / CP, it includes creating a stack of various layers, where n is greater than 1, and the joining of the different layers to each other can be completed or achieved by sewing, knitting, needling or other mechanical assembly operations.

[0097] Naturally, whatever the preparation process used, the porous layer and the reinforcement are selected in such a way that the thermoplastic porous layer(s) ultimately represents a maximum of 10% of the total mass of the reinforcement, preferably between 0.5 and 10% of the total mass of the reinforcement, more preferably between 2 and 6% of the total mass of the resulting reinforcement.

[0098] The process characteristics relate to the reinforcement characteristics as described within the context of the present invention.

[0099] Use of the reinforcement according to the invention for the manufacture of a preform or a composite part, and a process using same The reinforcement of the present invention comprises a fiber reinforcement having bonded to at least one of its faces a thermoplastic porous layer comprising a reactive thermoplastic polymer as defined within the context of the present invention, in particular selected from polyesters, copolyesters, polyamide-imides, polyethersulfones, polyimides, polyetherketones, polymethylmethacrylates, aromatic polyethers, polyamides and copolyamides, with -NH2 functional groups in an amount greater than 0.15 meq / g of the reactive thermoplastic polymer and / or -COOH functional groups in an amount greater than 0.20 meq / g of the thermoplastic polymer, and is perfectly suitable for the manufacture of preforms or composite parts bonded with epoxy thermosets.

[0100] The resin diffused or injected into the reinforcement or stack of reinforcements according to the invention is a thermosetting epoxy resin. Examples of epoxy resins include polyglycidyl derivatives of aromatic diamines, monoaromatic primary amines, aminophenols and polycarboxylic acids. Other examples include polyglycidyl ethers of bisphenols such as bisphenol A, bisphenol F, bisphenol S and bisphenol K. A large number of epoxy resins suitable for the direct manufacture of composite parts are commercially available, in particular from Solvay, Hexion and Hexcel Composites. Examples include RTM6 and HF620 resins from Hexcel Composites and EP2400 and EP2410 resins from Solvay. These resins consist of a mixture of epoxy resins, combined with one or more hardeners and optionally a mixture of one or more impact modifiers.

[0101] Other commercially available epoxy resins include N,N,N',N'-tetraglycidyldiaminodiphenylmethane (Huntsman MY9663, MY720, MY721), p-aminophenol triglycidyl ether (such as Huntsman's MY0510), m-aminophenol triglycidyl ether (such as Huntsman's MY0600) or difunctional epoxides (such as Huntsman's GY285, and CY184).

[0102] Epoxy thermosets can be tetrafunctional, trifunctional or difunctional, with an increase in the number of epoxy functionalities necessarily resulting in a higher crosslinking reaction rate. Such epoxy thermosets usually include one or more curing agents well known to those skilled in the art for use with the selected epoxy type thermosetting polymer. Examples of preferred curing agents include cyanoguanidine, aromatic, aliphatic and cycloaliphatic amines, acid anhydrides, Lewis acids, substituted ureas, imidazoles, hydrazines and silicones. The epoxy resin may also include a core-shell impact modifier or toughener, as is commonly used by those skilled in the art. Examples include Kane Ace MX impact modifier from Kaneka Corporation (Japan) or Clearstrength impact modifier from Arkema France. The process according to the invention is particularly interesting when the injected or infused resin is an epoxy type thermoset. The epoxy resin has the ability to react with -NH2 or -COOH functional groups present in sufficient amounts in the porous thermoplastic layer of the material according to the invention. Such a reaction prevents the thermoplastic polymer in the porous layer(s) from spreading into the injected or infused resin and changing the properties of the resin, especially with respect to heat resistance.

[0103] Preferably, epoxy resins are used in the context of the present invention that include tetrafunctional epoxies optionally mixed with trifunctional epoxies, one or more hardeners and one or more impact modifiers.

[0104] Advantageously, the thermosetting epoxy resins used in the context of the present invention have a Tg of at least 100° C., or even above 150° C. The choice of Tg of the resin used can be optimized by the person skilled in the art depending on the process step to be carried out and on whether it is desired to heat at a temperature Ta below or above the melting temperature of the reactive thermoplastic polymer.

[0105] Composite parts are usually manufactured in open or closed molds. Before being introduced into the mold, the resin can be preheated, in particular to a temperature of 60-90°C before being poured or injected into the reinforcement, stack or preform.

[0106] The injected or poured 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. In general, when producing composite parts, the temperature at which the thermosetting resin is poured or injected into the mold most often varies between 90 and 180 ° C. In the context of the present invention, the viscosity can be measured using a dynamic shear rheometer according to standard EN6043, the difference being that the deformation is 4% instead of 10%. In particular, the measurements are carried out with an air gap of 0.5 mm, a deformation control of 4%, a frequency of 10 rad / s and an isothermal heating rate of 2 ° C / min.

[0107] Typically, in the process for manufacturing a preform or composite part from at least one reinforcement according to the invention, a thermosetting resin, a thermoplastic resin or a mixture of thermosetting and thermoplastic resins, in particular as defined within the context of the present invention, in particular a thermosetting epoxy resin, is injected or poured into said reinforcement, or into a stack of several reinforcements, or into a preform made from said material. By preform is meant a reinforcement, or a set of reinforcements, that has undergone a prior forming operation before being placed in a mold or tool used to manufacture the composite part.

[0108] To manufacture a composite part, the reinforcements according to the invention are stacked or draped (also known as plies). Usually, the reinforcements according to the invention are cut to the desired size to manufacture the part, ply, stack or preform to be obtained. In a stack, several reinforcements or plies are stacked on top of each other.

[0109] A ply may be wide enough to produce the desired part and may consist of a single reinforcement according to the invention if the part is not too complex, but more often, for large or complex parts, a ply will consist of a set of reinforcements according to the invention arranged side by side to cover the entire surface required to produce the desired part.

[0110] In the context of the present invention, due to the thermoplastic nature of the porous layers present in the reinforcement, a deposition or moulding operation using the high temperature tack of said at least one porous layer present in the reinforcement can be carried out during the manufacture of the preform or composite part, before the injection or infusion of the resin. Advantageously, the process of manufacturing a preform or composite part comprises a step of depositing or moulding a material according to the invention, the porous layer being heated to a temperature causing at least partial melting of said reactive thermoplastic polymer of the porous layer(s) as defined within the context of the present invention, in particular below 170°C or even below 150°C, preferably in the range of 100-140°C, more preferably in the range of 100-130°C.

[0111] The process used to manufacture composite parts is quite common to the person skilled in the art. Flat preforms or even preforms with the desired three-dimensional shape can be manufactured in the meantime. In particular, the deposition of the reinforcement according to the invention can be carried out continuously by application of pressure perpendicular to the deposition surface and applied thereto. Such processes, known under the abbreviations AFP (Automated Fiber Placement) or ATL (Automated Tape Lay-up), are described, for example, in documents WO2014 / 076433A1 and WO2014 / 191667. Different strips of material according to the invention can be placed next to each other along parallel or non-parallel deposition paths, depending on the preform to be manufactured, to form a series of plies arranged one on top of the other. Simultaneously with the deposition operation, the thermoplastic material of the porous layer is activated, i.e. softened, to take advantage of the high-temperature tackiness of the material. When a ply is completely deposited, the orientation is changed, so that the next ply is deposited along a different deposition trajectory than the previous one. Each strip is deposited parallel or non-parallel to the previous one (depending on the geometry of the part to be manufactured), with or without interstrip gaps, and with consolidation over the entire surface. This deposition process is particularly suitable for reinforcement widths between 3 and 300 mm, preferably with small width variations (<0.25 mm). If the reinforcement has a wider width, it can be deposited by any other suitable means.

[0112] In general, the manufacture of a composite part from at least one fiber reinforcement having a thermoplastic porous layer bonded to at least one of the faces of the fiber reinforcement and at least one reinforcement comprising a resin corresponding to an epoxy type thermosetting resin, is carried out by the following sequential steps: i) injecting or pouring the resin into the reinforcement material located in a mold, typically at a temperature in the range of 90°C to 180°C; ii) consolidation of the reinforcement / resin assembly during a heat treatment cycle; iii) cooling the consolidated composite part resulting from step ii); and Includes.

[0113] Typically, upstream of step i), the process for manufacturing a composite part according to the invention comprises a step of placing in a mould at least one reinforcement comprising at least one fibre reinforcement having a thermoplastic porous layer according to the invention bonded to at least one of the faces of the fibre reinforcement.

[0114] The manufacture of a composite part therefore comprises a step of diffusion of a thermosetting resin, a thermoplastic resin or a mixture of thermosetting and thermoplastic resins in a reinforcement or a stack of reinforcements according to the invention by injection or pouring, followed by a step of consolidation of the desired part by a polymerization / crosslinking step following a given cycle under heating and optionally pressure, and a cooling step. According to a particular embodiment, which is also suitable for 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.

[0115] As mentioned above, in the context of the present invention, in a very particularly preferred manner, the injected or infused resin is an epoxy resin.

[0116] For step i), the temperature mentioned is the temperature inside the mould when the resin is injected or diffused into the reinforcement.

[0117] The injection or infusion of the resin is typically carried out while the reinforcement, stack or preform into which the resin is being injected or infused is at a temperature of 110-180° C. This injection or infusion stage typically lasts from 2 minutes to 5 hours, depending on the size of the composite part being produced.

[0118] For producing composite parts, the resin is preferably injected under reduced pressure, in particular at a pressure below atmospheric pressure, in particular below 1 bar, preferably between 0.1 and 1 bar. Injection is preferably carried out in an open mould (in particular fitted with a vacuum bag), for example by vacuum bag injection. During the heat treatment stage, a pressure below atmospheric pressure can also be applied, in particular below 1 bar, preferably between 0.1 and 1 bar.

[0119] In another process according to the invention, the resin is added by injection and the reinforcement according to the invention, a stack or a preform of such material is placed in a mould (commonly called a closed mould) which is intended to be closed, in particular after the resin has been injected in a quantity sufficient to fill the mould. In such a case, when the resin is injected, a heat treatment step is carried out in the usual way, in particular under a pressure of 1 to 150 bar, preferably 1 to 10 bar. This is the case for the RTM, C-RTM and HP-RTM processes well known to those skilled in the art.

[0120] The composite part is then obtained after a consolidation step corresponding to a heat treatment. Step ii) is a heat treatment step for the resin / reinforcement(s) assembly, resulting in crosslinking of the thermosetting resin and consolidation of the composite part. This step comprises heating up to a temperature Ta, commonly called the curing temperature of the composite part. This temperature Ta may be equal to or greater than the temperature of step i). In such a case, when the temperature Ta is higher than the resin infusion or injection temperature, step ii) comprises a temperature rise stage up to the temperature Ta.

[0121] The composite parts are generally obtained by a conventional consolidation process accompanied by heating, according to the implementation known to the skilled person, using the heat treatment cycle recommended by the supplier of the resin used. This process of consolidating the desired part includes polymerization (for thermoplastic resins) or crosslinking (for thermosetting resins). For thermosetting resins, gelation of the resin occurs before curing / crosslinking. The pressure applied during the processing cycle can be low (in particular 0.1 mbar to 1 bar) when injected at atmospheric or reduced pressure, or high (in particular 1 to 150 bar) when injected into RTM molds. Generally, the epoxy resin is added at a pressure of 0.1 mbar to 15 bar, more generally 1 to 10 bar.

[0122] In most cases, during the heat treatment step, also known as the consolidation step, the heat treatment cycle comprises two stages: a temperature increase stage up to a temperature Ta, and a heating stage at said temperature Ta, generally known as the curing or post-curing stage. The temperature Ta is the temperature at which the thermosetting resin is crosslinkable. The temperature Ta and the heating time at this temperature are selected so as to achieve complete crosslinking of the selected epoxy thermosetting resin. In particular, the temperature Ta depends on the resin to be injected or poured. In general, the temperature Ta ranges from 120 to 220°C, preferably from 160 to 220°C, more preferably from 170 to 190°C, typically 180°C, in particular for epoxy resins used to manufacture composite parts for the aerospace industry. The heating time at such a temperature is usually between 30 minutes and 5 hours, typically 1 to 2 hours. The heating time is adapted to the temperature Ta by the person skilled in the art. The lower the temperature Ta, the longer the heating time required to completely cure the resin.

[0123] Conventionally, the temperature is increased by 0.1 to 10° C. per minute, in particular 1 to 3° C. per minute, typically 2° C. per minute.

[0124] According to a first embodiment variant, the heat treatment step comprises a heating step, in particular at a rate of 0.1-10 ° C / min, to a temperature Ta higher than the melting temperature of the reactive thermoplastic polymer of the at least one thermoplastic porous layer present in the reinforcement according to the invention, and in particular for a period of 5 min to 2 h at said temperature Ta. The viscosity of the thermosetting resin (or more precisely the thermosetting resin system modified after reaction with the thermoplastic porous layer) increases between the melting of the reactive thermoplastic polymer of the thermoplastic porous layer(s) and the onset of crosslinking of the epoxy thermosetting resin. This increase in viscosity reflects the reaction that takes place between the epoxy resin and the reactive -NH2 and / or -COOH functional groups of the reactive thermoplastic polymer in the porous thermoplastic layer of the reinforcement.

[0125] The reaction of the epoxy resin with the reactive -NH and / or -COOH functional groups of the reactive thermoplastic polymer in the porous thermoplastic layer of the reinforcement may also have the effect that during the heat treatment step, gelation of the epoxy thermoset occurs faster than if it were subjected to the heat treatment step alone.

[0126] According to a particular embodiment, gelation of the thermosetting resin occurs during heating to temperature Ta and after a heating time of 5 to 60 minutes at temperature Ta. The time for the epoxy resin to gel depends, inter alia, on the reactivity of the epoxy resin, the temperature of injection / infusion of the epoxy resin, the rate of rise to temperature Ta and the selected temperature Ta.

[0127] According to a first variant of the manufacturing process of the composite part according to the invention, in which the temperature Ta is higher than the melting temperature of the reactive thermoplastic polymer of the at least one thermoplastic porous layer, the epoxy thermoset preferably has a glass transition temperature Tg higher than 150° C.

[0128] According to a second embodiment variant, the heat treatment step comprises a heating step, in particular at a rate of 0.1-10 ° C. / min, to a temperature Ta below the melting temperature of the reactive thermoplastic polymer of the at least one thermoplastic porous layer, and heating at said temperature Ta for a period of time in particular between 5 min and 5 h. In this case, when the heating to achieve complete cross-linking polymerization of the epoxy resin is carried out at a lower temperature Ta, the heating time at this temperature may be longer. This is adjusted by the skilled person depending on the resin used. Here again, the reaction of the epoxy resin with the reactive -NH2 and / or -COOH functional groups of the reactive thermoplastic polymer of the porous thermoplastic layer of the reinforcement may also have the effect that during the heat treatment step, gelation of the epoxy thermosetting resin occurs faster than if it was subjected to the heat treatment step alone.

[0129] According to a second variant of the process for the manufacture of a composite part according to the invention, in which the temperature Ta is below the melting temperature of said reactive thermoplastic polymer of said at least one thermoplastic porous layer, the epoxy thermoset preferably has a glass transition temperature Tg at least equal to 100°C, advantageously in the range from 100 to 150°C.

[0130] Also advantageously, according to a second variant of the manufacturing process of the composite part according to the invention, the temperature Ta is below the melting temperature of the reactive thermoplastic polymer of the at least one thermoplastic porous layer, said reactive thermoplastic polymer having a melting temperature higher than 120°C.

[0131] In the context of the present invention and regardless of how the process is carried out, during the heat treatment stage, the gelling of the thermoset occurs after the reactive functional groups of the reactive thermoplastic polymer of the porous thermoplastic layer of the reinforcement react with the epoxy thermoset, while other reactions can still take place during the complete crosslinking of the resin.

[0132] Once the heat treatment is complete, cooling is performed by circulating a fluid acting as a coolant, in particular water or a mixture of water and air, and heating is discontinued. Pressurization is usually discontinued during cooling, in particular when a temperature below 40°C is reached.

[0133] Naturally, the same properties and applications as described in connection with the reinforcement material according to the invention apply to the processes and uses described within the context of the present invention.

[0134] The reactive thermoplastic polymers used in the context of the present invention have a sufficient amount of reactive -NH2 and / or -COOH functional groups that make it possible to react with epoxy-type resins commonly used in the manufacture of composite parts. As will become clear from the examples, such reactions make it possible to impart particularly advantageous properties to the composite parts obtained, in particular improving the temperature and moisture resistance, while retaining satisfactory mechanical properties that are important for composite parts for the aviation and aerospace industries.

[0135] Other aspects of the invention The present invention can also be applied to thermosetting resins other than epoxy resins.

[0136] Other usable thermosetting resins are selected from unsaturated polyesters, vinyl esters, phenolic resins, polyimides, bismaleimides, phenol-formaldehyde resins, urea-formaldehyde resins, 1,3,5-triazine-2,4,6-triamine, benzoxazines, cyanate esters, and mixtures thereof, among others. Such resins may also include one or more curing agents known to those skilled in the art for use with the selected thermosetting polymer.

[0137] The reactive functional groups present on the reactive polymer are then adapted by one skilled in the art to react with the injected or poured thermosetting resin. In particular, in the case of unsaturated polyester or vinyl ester resins, as well as bismaleimides, the reactive thermoplastic polymer may contain unsaturation that allows it to react with these resins.

[0138] In the case of phenolic resins, the reactive thermoplastic polymer may contain, for example, alcohol, aldehyde or ketone functional groups that allow it to react with this type of resin.

[0139] The above description for the use of epoxy resins can be translated into these types of processes.

[0140] Therefore, the present specification also relates to the following aspects:

[0141] The description includes the following sequential steps: 0) placing at least one reinforcement member in a mold, the reinforcement member including at least one fiber reinforcement member having a thermoplastic porous layer bonded to at least one of the faces of the fiber reinforcement member; i) injecting or pouring a thermosetting resin into the reinforcement material placed in a mold, in particular at a temperature that may range from 90 to 180°C; ii) a heat treatment step for the resin / reinforcement(s) assembly, comprising heating to a temperature Ta resulting in crosslinking of the thermosetting resin and consolidation of the composite part; and iii) cooling the consolidated composite part resulting from step ii), The process for manufacturing a composite part is characterized in that said thermoplastic porous layer has reactive functional groups which react with said thermosetting resin during said heat treatment step.

[0142] In particular, in such a process, the thermoplastic porous layer(s) of the reinforcement occupy up to 10% of the total mass of the reinforcement, preferably 0.5-10% of the total mass of the reinforcement, more preferably 2-6% of the total mass of the reinforcement.

[0143] In such a process, the porous layer present in the reinforcement reacts with the thermosetting resin, which is only partially or not completely meltable with the thermosetting resins commonly used in the manufacture of composite parts, especially epoxy type thermosetting resins. As part of the method according to the invention, the thermoplastic porous layer has reactive functional groups which react with the thermosetting resin during the heat treatment stage, thereby reducing the sensitivity to temperature exposure and improving the temperature properties of the material used in the aerospace industry.

[0144] According to a first variant of such a composite part manufacturing process, said temperature Ta is higher than the melting temperature of said reactive thermoplastic polymer of said at least one thermoplastic porous layer. In particular, heating to said temperature Ta is carried out during step ii) for a period between 5 min and 2 h. In most cases, the heat treatment step comprises a temperature increase stage up to said temperature Ta, in particular at a rate of 0.1 to 10 ° C / min.

[0145] The viscosity of the thermosetting resin may increase between melting of said reactive thermoplastic polymer of the thermoplastic porous layer and the initiation of crosslinking of the thermosetting resin, in particular the viscosity of the modified thermosetting resin system after melt reaction with the thermoplastic porous layer increases.

[0146] During the heat treatment step, gelation of the thermosetting resin may occur more quickly than if it were subjected to only the heat treatment step.

[0147] Gelation of the thermosetting resin can occur during heating to the temperature Ta, especially after a heating time of 5 to 60 minutes at the temperature Ta.

[0148] According to a first variant of such a process for manufacturing a composite part, in which the temperature Ta is higher than the melting temperature of the reactive thermoplastic polymer of the at least one thermoplastic porous layer, the thermosetting resin preferably has a glass transition temperature Tg higher than 150° C.

[0149] According to a second variant of such a composite part manufacturing process, the temperature Ta is below the melting temperature of said reactive thermoplastic polymer of said thermoplastic porous layer. In particular, during step ii) heating to said temperature Ta takes place for 5 min to 5 h. Preferably, gelation of the thermosetting resin occurs faster than if it were subjected to the heat treatment step alone. Here too, the heat treatment step generally comprises a temperature increase stage up to said temperature Ta, in particular at a rate of 0.1 to 10 ° C / min.

[0150] According to a second variant of such a process for manufacturing a composite part, in which the temperature Ta is below 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 at least equal to 100°C, advantageously in the range from 100 to 150°C.

[0151] Also advantageously, according to a second variant of such a process for manufacturing a composite part, in which the temperature Ta is below the melting temperature of the reactive thermoplastic polymer of the at least one thermoplastic porous layer, said reactive thermoplastic polymer having a melting temperature higher than 120°C.

[0152] In such processes for manufacturing composite parts, regardless of their variants of implementation, the temperature Ta is generally in the range of 120 to 220 ° C, preferably in the range of 160 to 220 ° C, more preferably in the range of 170 to 190 ° C and typically equal to 180 ° C.

[0153] In said processes for manufacturing composite parts, whatever their implementation variants, during the heat treatment step, advantageously the gelling of the thermosetting resin occurs after the reactive functional groups have reacted with said thermosetting resin.

[0154] Furthermore, the reaction of the thermoplastic polymer of the porous layer with the injected or infused resin allows the use of a porous layer with a low melting temperature, which in turn allows the use of lower temperatures during the production and molding of the reinforcement, thus saving in terms of costs and time. A further advantage is that the melting temperature of said reactive thermoplastic polymer of the thermoplastic porous layer can be below 170°C, or even below 150°C, so that all stages of the manufacturing process before the addition of the resin finally required to produce the part (from the preparation of the dry material through its deposition and preform) can be carried out at temperatures below 170°C, or even better below 150°C, or even below. Such a porous layer comprising a reactive thermoplastic polymer with a lower melting point therefore allows the reinforcement joining the porous layer(s) and the fiber reinforcement(s) to be manufactured at temperatures compatible with automated manufacturing processes, in particular fiber placement and thermoforming of flat-laid preforms.

[0155] A second objective of such a process is therefore to combine the beneficial effect of using a thermoplastic porous layer on impact performance with the possibility of carrying out all stages of the manufacturing process prior to the infusion or injection of the resin at temperatures below 150°C or even below 140°C, possibly in the range of 80-130°C or 100-130°C.

[0156] Thus, advantageously, in the process for manufacturing a composite part, the reactive thermoplastic polymer of the at least one thermoplastic porous layer present in the reinforcement has a melting temperature below 170°C, even below 150°C, preferably in the range from 100 to 140°C, more preferably in the range from 100 to 130°C.

[0157] Prior to the injection or infusion of the thermosetting resin, the process for producing a composite part may comprise the deposition or moulding of the reinforcement material, taking advantage of the high temperature tack of the at least one thermoplastic porous layer present in the reinforcement material, and heating it to a temperature below 170°C, or even below 150°C, preferably in the range of 80-140°C, in particular 100-140°C, more preferably 80-130°C, in particular 100-130°C, selected in correlation with the melting temperature of the reactive thermoplastic polymer of the thermoplastic porous layer.

[0158] These methods of manufacturing composite parts are particularly suitable where the injected or infused resin is an epoxy resin.

[0159] Advantageously, said epoxy resin has a viscosity of less than 1000 mPa.s at a temperature of 90°C.

[0160] Particularly preferred epoxy resins include those that include a tetrafunctional epoxy, optionally mixed with a trifunctional epoxy, one or more hardeners, and one or more impact modifiers.

[0161] In particular, in said process for manufacturing composite parts, the thermoplastic porous layer comprises or consists of a so-called reactive thermoplastic polymer, which has -NH2 functional groups in an amount greater than 0.15 meq / g of the reactive thermoplastic polymer and / or -COOH functional groups in an amount greater than 0.20 meq / g of the reactive thermoplastic polymer. Such a porous thermoplastic layer is particularly suitable when the injected or infused resin is an epoxy resin, in particular one of the resins mentioned above.

[0162] Advantageously, said reactive thermoplastic polymer has -NH2 functional groups 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, more preferably in the range of 0.20 to 0.95 meq / g of reactive thermoplastic polymer, and / or -COOH functional groups 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, more preferably in the range of 0.20 to 0.95 meq / g of reactive thermoplastic polymer.

[0163] In particular, the reactive thermoplastic polymer is a polyamide or copolyamide carrying said functional groups.

[0164] In particular, in said process for manufacturing a composite part, said at least one porous layer comprises -NH2 functional groups in an amount greater than 0.15 meq / g of porous layer and / or -COOH functional groups in an amount greater than 0.20 meq / g of porous layer. Again, such a thermoplastic porous layer is particularly suitable when the injected or infused resin is an epoxy resin, in particular one of the aforementioned resins.

[0165] According to a particular embodiment, the reactive thermoplastic polymer has a number average molecular weight Mn greater than 4000 g / mol.

[0166] According to a particular embodiment, step i) is carried out by resin injection and the heat treatment of step iii) is carried out in a closed mould under a pressure between 1 and 150 bar.

[0167] According to another particular embodiment, the placement step 0) is carried out in an open mould, in particular fitted with a vacuum cover, and step i) is carried out under reduced pressure, in particular under a pressure of 0.1 to 1 bar.

[0168] In the reinforcements used in such processes, the fiber reinforcement can take different forms: in some embodiments, the fiber reinforcement is a unidirectional web of reinforcing yarns, a woven fabric of reinforcing yarns, or a stack of unidirectional webs of reinforcing yarns bonded together by any other physical means such as sewing or needling.

[0169] The fibre reinforcement may in particular consist of glass fibres, aramid fibres or preferably carbon fibres.

[0170] According to some embodiments of such a process, the reinforcement used consists of a unidirectional web of reinforcing threads corresponding to a fibrous reinforcement, with a thermoplastic porous layer as defined within the context of the present invention bonded to at least one of its faces, preferably said reinforcement consists of a unidirectional web of reinforcing threads corresponding to a fibrous reinforcement, with a thermoplastic porous layer as defined within the context of the present invention bonded to each of its faces, the thermoplastic porous layers present on each of the faces of the unidirectional web of reinforcing threads being identical.

[0171] According to some embodiments, the reinforcement used in the process consists of a stack of unidirectional webs of reinforcing threads as fiber reinforcement oriented in different directions, with at least one thermoplastic porous layer as defined within the context of the present invention interposed between two unidirectional webs of reinforcing threads and / or present on the surface of the stack. Such a stack can be in the form of a stack of unidirectional webs of reinforcing threads in the arrangement (CP / R) n (CP) m or (CP / R / CP) n where CP denotes a porous thermoplastic layer as defined within the context of the present invention, R is a unidirectional web, n is an integer equal to or greater than 1, and m is 0 or 1. In such a stack, the unidirectional webs of reinforcing yarns can be joined to each other or to at least one of the thermoplastic porous layers by sewing, knitting or needling.

[0172] In the reinforcement used in the process, the thermoplastic porous layer or layers present are in particular porous films, grids, powder deposits, woven fabrics or, preferably, nonwoven fabrics or veils.

[0173] Another aspect of the description also relates to a composite part obtained by a manufacturing process as defined herein.

[0174] The present specification therefore relates to a composite part comprising a thermosetting resin, in particular an epoxy resin, matrix, comprising at least one reinforcement comprising at least one fiber reinforcement with a thermoplastic porous layer bonded to at least one of the faces of the fiber reinforcement. In said composite part, there is a covalent bond between the thermosetting epoxy matrix and the thermoplastic polymer present in the thermoplastic porous layer(s), said covalent bond resulting from the reaction of reactive functional groups present in said thermoplastic polymer with the thermosetting resin, in particular the epoxy. In particular, in such a composite part, said thermoplastic porous layer(s) of said reinforcement represents up to 10% of the total mass of the reinforcement, preferably between 0.5 and 10% of the total mass of the reinforcement, more preferably between 2 and 6% of the total mass of the reinforcement.

[0175] The present invention is illustrated by the following examples, which are not intended to be limiting, and which refer to the accompanying drawings. [Brief description of the drawings]

[0176] [Figure 1] FIG. 2 is a schematic diagram of a manufacturing process for an example of a reinforcement material according to the present invention.

[0177] [Diagram 2] FIG. 1 is a schematic diagram of an example of a reinforcement material according to the present invention.

[0178] [Diagram 3] 1 shows images obtained under an optical microscope when different Veil and RTM6 epoxy resins were placed between two glass slides and subjected to heating at 180° C.

[0179] [Figure 4] The reversible and irreversible heat flows with a temperature increase of 2°C / min are shown by modulated differential scanning calorimetry for different bars in Huntsman tetrafunctional epoxy resin without hardener when cycled at 120°C for 1 hour + 180°C for 2 hours with a temperature increase of 2°C / min.

[0180] [Diagram 5] 1 shows the change in viscosity of RTM6 resin alone during curing, the viscosity of RTM6 resin when dispersed within a stack of CP1 porous layers consistent with the present invention, and the viscosity of the same stack of CP1 porous layers in oil.

[0181] [Figure 6] 4 shows the viscosity of RTM6 resin alone (temperature increase and subsequent curing) and the change in viscosity of the RTM6 resin when dispersed in a stack of porous layers CP1 or CP8 with -COOH functional groups in accordance with the present invention, or CP9 outside the present invention.

[0182] [Figure 7] FIG. 1 shows the change in elastic modulus G′ and G″ as a function of time and temperature during the heat treatment process (temperature increase and subsequent curing) of RTM6 resin when it is dispersed within a CP8 porous layer in accordance with the present invention or a stack of CP9 outside the present invention.

[0183] [Figure 8] FIG. 1 shows the change in viscosity of RTM6 resin alone during the heat treatment process (temperature increase followed by curing) when RTM6 resin is dispersed in a stack of CP2 or CP5 porous layers with -NH2 functional groups conforming to the present invention or CP4 outside the present invention.

[0184] [Figure 9]FIG. 1 shows the change in viscosity of RTM6 resin alone during the heat treatment step (temperature increase and subsequent curing) of Huntsman tetrafunctional epoxy resin without hardener (curing agent), when RTM6 resin is dispersed in a stack of CP1, CP2, CP5 or CP8 porous layers in accordance with the present invention, or CP9 outside the present invention.

[0185] [Figure 10] FIG. 1 shows the change in viscosity and elastic modulus G′ and G″ as a function of time and temperature when a Huntsman tetrafunctional epoxy resin without hardener is diffused in a stack of CP8 porous layers according to the present invention during the heat treatment step (temperature increase and subsequent curing).

[0186] [Figure 11] FIG. 1 shows the change in viscosity of RTM6 resin during the heat treatment process (temperature increase followed by curing) when the resin is dispersed within a stack of CP10 porous layers conforming to the present invention, or within a stack of layers of non-porous films made from the same polymer.

[0187] [Figure 12] FIG. 1 shows the variation in gel time (time of heating at temperature Ta until the gel point is reached) as a function of the isothermal temperature Ta (temperature used for resin injection and curing) of RTM6 resin when the RTM6 resin is dispersed in a stack of CP8 porous layers conforming to the present invention.

[0188] [Figure 13] Figure 1 shows the heating time at 180°C required to achieve gelation of the resin (crossover of G' and G'' moduli) for different epoxy resins diffused into a stack of different layers (inventive and non-inventive) with a temperature ramp from 120°C to 180°C at 2°C / min + 2 hours at 180°C.

[0189] [Figure 14]In the case of Reinforcement 2 (not according to the invention), FIG. 14 shows the DMA curves obtained for a composite part obtained by injection of RTM6 resin, with and without conditioning at 70° C. for 14 days, when the temperature is increased at 2° C. / min from 25° C. to 270° C.

[0190] [Figure 15] In the case of reinforcement 5 (according to the invention), FIG. 15 shows the DMA curves obtained for a composite part obtained by injection of RTM6 resin, with and without conditioning at 70° C. for 14 days, when the temperature was increased at 2° C. / min from 25 to 270° C.

[0191] [Figure 16] In the case of reinforcement 6 (according to the invention), FIG. 16 shows the DMA curves obtained for a composite part obtained by injection of RTM6 resin, with and without conditioning at 70° C. for 14 days, when the temperature is increased at 2° C. / min from 25° C. to 270° C. EXAMPLES

[0192] example Reinforcement, porous layer and resin used The fibre reinforcement used in all cases is a 210 g / m2 composite made from carbon fibre marketed by Hexcel Composites, Dagneux France under the reference IMA 12K. 2 The properties of these 12K fibers are summarized in Table 1 below. [Table 1]

[0193] The porous polymer layers studied are shown in Table 2 below. [Table 2]

[0194] *meq / g polymer = meq / g porous layer

[0195] Table 3 gives some details of the polymers used to form the porous layer. [Table 3]

[0196] The porous layer used for comparison was made from: 1) CP9: 1R8D04 thermoplastic veil marketed by Protechnic (66, rue des Fabriques, 68702-CERNAY Cedex-France) and having a melting temperature of 160°C - this veil (hereinafter referred to as 1R8D04 veil) is meltblown and has a melting point of 4 g / m before lamination to the fiber reinforcement. 2 and a thickness of 100 μm. The fibers have a diameter of 15 μm. The open area of ​​such a layer is about 50%. 2) CP7: a fiber veil made from Platamid® HX2632 polymer (a copolyamide with terminal unsaturation that allows obtaining a three-dimensional network under UV, gamma or beta treatment), marketed by Arkema and having a melting temperature of 117° C. - this veil (hereafter referred to as HX2632 veil) was meltblown and had a density of 4 g / m before being laminated to the fiber reinforcement. 2 and a thickness of 100 μm. The fibers have a diameter of 15 μm. The open area of ​​such a layer is about 50%. CP7a: A fiber veil made of Platamid® HX2632 polymer marketed by Arkema and having a melting temperature of 109° C., crosslinked under beta treatment (100 kGy as described in WO2019 / 102136). This meltblown veil has a mass per unit area of ​​4 g / m 2It has a thickness of 100 μm before lamination to the fiber reinforcement and is partially crosslinked under beta treatment. The fibers have a diameter of 15 μm. The open area of ​​such a layer is around 50%. 3) CP6: Product by depositing layers of epoxy powder marketed by Hexcel Composites, Dagneux France and used in Primetex 43098 S 1020 S E01 1F fabric. The powder has an average diameter of 51 μm (D50, median) and a glass transition temperature in the range of 54-65 °C. 4) CP3: A fiber veil marketed by Arkema and made from Platamid® polymer with a melt temperature of 103° C. - this veil is meltblown and weighs 4 g / m before laminating with the fiber reinforcement. 2 and a thickness of 100 μm. The fibers have a diameter of 15 μm. The open area of ​​such a layer is about 50%. 5) CP4: A fiber veil made of Platamid® polymer marketed by Arkema and having a melting temperature of 126° C. - this veil is meltblown and has a thickness of 4 g / m before lamination to the fiber reinforcement. 2 and a thickness of 100 μm. The fibers have a diameter of 15 μm. The open area of ​​such a layer is about 50%.

[0197] A porous layer according to the present invention was made from: 1) CP1: A fiber veil marketed by Arkema and made from Platamid® polymer, with a melt temperature of 146° C. - this veil was meltblown and weighed 4 g / m before laminating with the fiber reinforcement. 2 and a thickness of 100 μm. The fibers have a diameter of 15 μm. The open area of ​​such a layer is about 50%. 2) CP2: A fiber veil made of Platamid® polymer marketed by Arkema and having a melting temperature of 106° C. - this veil is meltblown and has a thickness of 4 g / m before lamination to the fiber reinforcement.2 and a thickness of 100 μm. The fibers have a diameter of 15 μm. The open area of ​​such a layer is about 50%. 3) CP5: Copolyamide veil from Arkema with a melt temperature of 128°C - this veil is meltblown and weighs 4g / m before lamination with the fibre reinforcement. 2 and a thickness of 100 μm. The fibers have a diameter of 15 μm. The open area of ​​such a layer is about 50%. 4) CP8: Copolyamide veil from Arkema with a melt temperature of 121°C - this veil is meltblown and weighs 4g / m before being laminated with the fibre reinforcement. 2 and a thickness of 100 μm. The fibers have a diameter of 15 μm. The open area of ​​such a layer is about 50%. 5) CP10: Arkema copolyamide veil with a melt temperature of 125°C - this veil is meltblown and weighs 4g / m before lamination with the fibre reinforcement. 2 and a thickness of 100 μm. The fibers have a diameter of 15 μm. The open area of ​​such a layer is about 50%.

[0198] The thermosetting resins used to manufacture the composite parts are listed in Table 4 below. [Table 4]

[0199] Method for determining the amount of -NH2 and -COOH functional groups:

[0200] The amount of reactive -COOH or -NH2 functional groups present can be assessed by potentiometric titration. The amount of -COOH functional groups can be determined by titration with tetra-n-butylammonium hydroxide ((C4H9)4N + OH -The amount of -NH2 functionality is measured by acid-base titration of the porous layer with (TBAOH) and the amount of -NH2 functionality is measured by titration with perchloric acid (HClO4) in acetic acid. Results are expressed in meq / g of polymer evaluated. The method described in document AB-068 by Metrohm entitled "Potentiometric determination of carboxyl and amino end groups in polyesters and polyamides" details the potentiometric titration procedure used to measure the carboxylic acid and amine functionalities present.

[0201] The reagents used in the assay are as follows: TBAOH (0.1 mol / L in isopropanol) = reactive titrant for COOH reactive functional groups, HClO4 (0.1 mol / L in glacial acetic acid) = reactive titrant for NH2-reactive functional groups; Benzyl alcohol.

[0202] To measure the amount of COOH reactive functional groups, weigh 0.5-1.5 g of sample into a beaker, mix with 100 mL of benzyl alcohol and dilute by heating to boiling point. After cooling to about 80-100 °C, titrate with TBAOH. Immerse the end of the buret slightly in the solution. Determine the blank value (i.e., no sample is added) under the same conditions.

[0203] To measure the amount of NH2 reactive functional groups, 0.5-1.0 g of sample is weighed into a beaker, mixed with 100 mL of benzyl alcohol and diluted by heating to boiling point. After cooling to about 80-100 °C, titration is carried out with perchloric acid HClO4. The end of the buret is slightly immersed in the solution. The blank value is measured under the same conditions.

[0204] The amount of reactive functional groups is then calculated according to the following formula:

[0205] Amount of reactive functional group (COOH or NH2, μeq / kg) =

number

[0206] In the above formula, A is the sample titrant consumption (mL), B is the blank titrant consumption (mL), t is the titrant titer, and E is the sample mass (g).

[0207] The titer of the titrant is determined potentiometrically according to Metrohm bulletin 206 / 5 e "Titer determination in potentiometry". For TBAOH, benzoic acid is commonly used. For HClO4, TRIS ((tris-hydroxymethyl)-amino-methane) is commonly used.

[0208] Lamination of bales - Obtaining baled UD reinforcement

[0209] The veils are bonded to the unidirectional web of carbon yarns using a production line using the machines detailed below with reference to Figure 1 as described in WO2010 / 061114. The resulting reinforcement 1 is shown diagrammatically in Figure 2. The reinforcement 1 consists of a unidirectional web 2 of carbon yarns 3 bonded to each of its faces with a veil 4, 5, the bonding being achieved thanks to the high temperature tack of the thermoplastic veils 4, 5.

[0210] The carbon thread 3 is unwound from a corresponding spool 30 of carbon thread fixed on a creel 40, passes through a comb 50 and is introduced into the axis of the device by means of a guide roller 60, a comb 70 and a guide bar 80a.

[0211] The carbon thread 3 is preheated by the heating bar 90 and then spread by the spreading bar 80b and the heating bar 100 to the desired carbon mass per unit area of ​​the unidirectional web 2. The rolls 13a and 13b of bales 4 and 5 are unwound without tension and transported by continuous belts 15a and 15b fixed between the free-rotating non-motorized rolls 14a, 14b, 14c, 14d and the heating bars 12a, 12b. The bales 4 and 5 are preheated in zones 11a and 11b before contacting the carbon thread 3 and are laminated on both sides of the two heating bars 12a and 12b with controlled air gap. A calender 16, which may be cooled, then applies pressure to the unidirectional web with the bales on both sides, resulting in the reinforcement 1 in ribbon form. A return roller 18 redirects the reinforcement 1 to a traction system with a motor-driven winding 19 and winding trio 20 to form a roll from the reinforcement 1 formed as above.

[0212] Tests carried out I. Measurement DSC: Differential Scanning Analysis. The analyses were carried out on a Discovery 25 instrument from TA Instruments, Gaiencourt, France.

[0213] DMA: Dynamic Mechanical Analysis. The analysis was carried out on a Q800 instrument from TA Instruments, Guyancourt, France, according to standard EN 6032 (1 Hz, 1° C. / min, amplitude 15 μm).

[0214] Hot Microscopy: Analyses were performed on an Axio M2m Microscope Imager from Zeiss (Marly-le-Roi, France) equipped with a heating system from Linkam Scientific Instruments (Tadworth, UK).

[0215] Rheology: Viscosity analysis was performed on a HAAKE Mars 60 rheometer, Thermofisher Scientific, Courtaboeuf, France. The analysis was performed according to EN6043 at 2°C / min and 10 rad / sec, but with a strain of 4% instead of 10%.

[0216] II. Effect of the Level of Reactive Functional Groups on Mobility in RTM6 Resin The porous layer (CP) to be studied and the RTM6 epoxy resin applied to it are placed between two glass slides and the whole is placed under an optical microscope. The whole assembly is then subjected to a temperature increase of 2°C / min up to a temperature of 180°C, which corresponds to the final temperature when the RTM6 epoxy resin is poured or injected during the manufacture of the composite part. This is a critical cycle for the temperature resistance of the CP layer, since no pre-crosslinking of the resin is used.

[0217] Figure 3 shows an image obtained at 180°C, i.e. post-crosslinking of the resin. In the case of the CP3, CP4 and CP7 layers, which do not correspond to the definition of the present invention, it can be seen that the veil dissolves in the resin or completely loses its integrity. Also, in the case of the CP8 layer, which corresponds to the present invention, the veil appears to lose its integrity in the resin, an indication that the reactivity and the integrity of the porous layer are not correlated. However, a decrease in the mobility of the porous layer in the resin is still observed, which is sufficient.

[0218] On the one hand, it is quite clear that the presence of -NH2 functional groups in the porous layer, corresponding to an amount of more than 0.15 meq / g, makes it possible to maintain the integrity of the porous layer in contact with the epoxy resin, even when the temperatures reached are far above the melting point of the porous layer (porous layers CP2 and CP5), as in the case of the porous layer CP7a made of a partially crosslinked thermoplastic polymer, which clearly indicates that a reaction has taken place between the porous layer and the resin.

[0219] Similarly, an amount of -COOH functional groups in the porous layer of more than 0.20 meq / g is required for reactivity in contact with the epoxy resin (porous layers CP1, CP8, CP10), but this does not necessarily result in the preservation of its integrity. Nevertheless, a decrease in mobility and dissolution of the porous layer in the resin are observed, which clearly indicates 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 result in a more or less significant preservation of the integrity of the porous layer. Further studies were carried out to determine the presence or absence of a reaction between the tested porous layers and the resin.

[0220] III. Demonstration of the reactivity of the porous layer towards epoxy functional groups Various results were obtained using Huntsman tetrafunctional epoxy without hardener and a porous layer: Modulated differential scanning calorimetry (MDSC) Planar rheology.

[0221] Modulated Differential Scanning Calorimetry (MDSC) Approximately 2 mg of the porous layer was impregnated with approximately 18 mg of epoxy and the assembly was placed in a closed aluminum DSC capsule which was then drilled. The resulting capsule was then placed in an oven and subjected to a temperature cycle equivalent to a conventional cycle used during the manufacture of composite parts by injection or infusion: 1 hour 120°C + 2 hours 180°C, with a temperature increase of 2°C / min. After curing, the sample was allowed to cool slowly to room temperature.

[0222] The resulting samples were then analyzed by MDSC at 2°C / min to distinguish between reversible phenomena (epoxy and beyr glass transitions, beyr melting) and irreversible phenomena (exothermic resin crosslinking). The results are shown in Figure 4.

[0223] The first observation is that the curing cycle does not affect the epoxy, since the MDSC curves remain unchanged with a glass transition around -15 / -20 °C. On the other hand, it is clear that if the porous layer reacts with the epoxy during the curing cycle, it can no longer recrystallize and therefore no longer shows a melting point in the MDSC analysis (porous layers CP1 and CP2). Conversely, if the porous layer does not react with the epoxy, it can recrystallize upon cooling, as shown by the melting point of porous layer CP9, visible at about 150 °C.

[0224] The second observation is the initiation of epoxy crosslinking at elevated temperatures, which occurs 10-20 °C earlier when the resin has been able to partially react with the porous layer.

[0225] Finally, if the porous layer is allowed to react with the epoxy, a slight glass transition is observed at about 10-20° C. This glass transition may be that of some of the epoxy that has begun crosslinking with the porous layer.

[0226] Planar Rheology A 35 mm diameter disk with 0.12 g of porous layer was prepared by stacking several plies of porous layer. The resulting disk was then immersed in RTM6 epoxy resin until it was completely impregnated and then placed on the bottom plate of the rheometer. Excess resin was then removed as the top plate was lowered until a 0.5 mm air gap was obtained in which the epoxy resin-impregnated porous layer sample was located.

[0227] According to standard EN6043, the imposed strain was 4%, the shear frequency was 10 rad / s and the curing cycle was isothermal at 120° C. for 1 h followed by a ramp up to 180° C. at 2° C. / min for 2 h.

[0228] Figure 5 shows the change in viscosity during curing, where 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 and even decreases slightly as the temperature increases before crosslinking occurs. To ensure that the increase in system viscosity in the presence of the CP1 porous layer is due to the porous layer alone, the same test was also performed by immersing the porous layer in an oil of identical viscosity to RTM6 (PMX-50 oil) at 120°C. It was then observed that the CP1 porous layer melted to a greater extent (viscosity level was a greater 20-fold decrease compared to the 10-fold decrease in RTM6) and then the viscosity of the mixture remained constant. This observation therefore confirmed that the increase in viscosity of the RTM6 porous layer / resin system observed following melting of the porous layer was due to the reaction between the RTM6 resin (more specifically its epoxy functional groups) and the CP1 porous layer (more specifically its reactive functional groups -COOH).

[0229] FIG. 6 shows the same type of results, but in the presence of different porous layers with -COOH functional groups: CP1 and CP8 are in accordance with the present invention, while CP9 has only 0.10 meq / g of -COOH functional groups and 0.12 meq / g of -NH2 functional groups and is therefore outside the scope of the present invention.

[0230] These results clearly demonstrate that it is possible to control the level of reaction of the -COOH functional groups with the epoxy resin by controlling the amount of the -COOH functional groups in the porous polyamide layer.

[0231] Crosslinking can also be monitored using shear rheology, since at the gel point (or gelling point) the storage modulus G' and loss modulus G'' are equivalent. The gel point therefore corresponds to the intersection between the two curves G' and G''.

[0232] By increasing the level of -COOH functionality in the porous layer (CP8), it is possible to achieve cross-linking between the porous layer and the RTM6 resin, as shown by the crossover of G' and G'' moduli after 50 min of the experiment and at 158 ​​°C (Figure 7). In the presence of the CP9 porous layer, the gel point of RTM6 remains virtually unchanged, confirming that the porous layer does not react with the resin.

[0233] Similarly, Figure 8 shows the change in viscosity in the presence of different porous layers with -NH2 functionality. Again, by increasing the level of -NH2 functionality in the porous polyamide layer, it is possible to control the level of reaction between the -NH2 functionality and the epoxy resin.

[0234] These results are complemented by a second series of experiments in which the porous layer to be tested is immersed not in the RTM6 resin but in Huntsman tetrafunctional epoxy without hardener, which emphasizes more the reaction between the reactive functional groups of the polyamide and the epoxy, which may be masked by the presence of the hardener in the RTM6 resin, due to the fact that the kinetics of the epoxy / hardener reaction is faster than that of the epoxy alone. The test conditions are otherwise strictly identical and the results obtained are shown in Figure 9, which made it possible to monitor the gelation of the epoxy / polyamide system. For the CP8 layer, a clear increase in viscosity is observed with increasing temperature (Figure 9), but it also seems that the G' and G'' moduli cross over after a temperature increase of 28 minutes at 155 °C (Figure 10). It is important to note that only the epoxy resin gels after more than 11 hours at 180 °C, which also confirms that the gelation point observed in Figure 10 is due to a reaction between the porous layer and the epoxy. For the other CP1, CP2 and CP5 layers, no change in the gel point of the epoxy is observed, but limited melting of the porous layer and an increase in the viscosity of the mixture is observed, indicating a reaction between the reactive functional groups and the epoxy. In contrast, the CP9 layer melts significantly and the viscosity of the mixture remains constant throughout the test, indicating no interaction or reactivity (Figure 9).

[0235] IV. No Effect of Porous Layer Structure on Epoxy Reactivity of RTM6 Resin To evaluate whether the structure of the polyamide layer used has any effect on the reactivity of the RTM6 resin with epoxy, the polyamide of the porous layer 10 (CP10) in the form of a nonwoven fabric was also tested in the form of a nonporous film with a thickness of 100 μm. Figure 11 (showing the change in viscosity during a temperature increase of 2 °C / min from 120 °C to 180 °C for 2 hours for epoxy / polyamide samples depending on the structure of the porous layer or polyamide film) shows that the structure of the layer does not affect the reactivity with epoxy. The accessibility of the -COOH functional groups of the polyamide therefore remains the same whether in the form of a nonwoven fabric (CP10) or in the form of a nonporous film.

[0236] V. Reactivity of the Porous Layer at Temperatures Below the Melting Point The ability of the porous layer to react with the RTM6 resin below its melting point was verified using a CP8 porous layer. Figure 12 shows the variation of gel time (time of heating at temperature Ta until the gel point is reached) with the isothermal temperature Ta (temperature used for resin injection and curing) applied during the testing of RTM6 and RTM6 / porous layer CP8 samples. Figure 12 shows that the porous layer is able to react and improve (modify) the gel point of RTM6 even below its melting point. It is therefore clear that the reaction rate of the CP8 / RTM6 porous layer is accelerated when the two materials are in contact above the melting point of the porous layer (greater mobility of the porous layer and therefore increased accessibility of the -COOH functional groups of the polyamide), but reaction is also possible below the melting point.

[0237] VI. Application to various commercially available resins Various porous layers were immersed in the four commercial resins mentioned above, namely RTM6, HF620, EP2400 and EP2410. The gel point was then measured as the intersection of G' and G'' modulus at 2°C / min from 120°C to 180°C + 2 hours at 180°C. Figure 13 shows the results obtained. If gelation occurs during the 180°C heating step, the difference is the heating time required to achieve gelation, which is shown in the top part of Figure 13.

[0238] The difference in reactivity between RTM6 and HF620 resins on the one hand, and between EP2400 and EP2410 resins on the other hand, is clear and is reflected in the very different times needed to achieve gelation at 180°C. The lower the reactivity of the resin, the longer the time for the porous layer to react. Thus, although the reaction between the reactive functional groups and the epoxy occurs as previously demonstrated, the porous layers CP1 (carrying -COOH functional groups in accordance with the invention) and CP5 (carrying -NH2 functional groups in accordance with the invention) do not affect the gel point of RTM6. On the other hand, in these same layers, the gel point is improved for the HF620 resin and even more significantly improved for the EP2400 and EP2410 resins. Thus, due to the slower epoxy / hardener reaction rate in the case of HF620, EP2400 and EP2410 resins, the reaction between the reactive functional groups and the epoxy has a greater impact on the gel point of the resin. In both cases, whether the gel point is improved with the porous layer according to the invention in the case of the RTM6 resin or not, there is, as mentioned above, a reaction between the reactive functional groups carried by said layer and the epoxy resin, which is also realized in the maintenance of mechanical properties, as shown in paragraph IV below. Conversely, in the CP4 and CP9 porous layers (outside the scope of the invention), there is no change in the gel point, regardless of the resins: EP2400 and EP2410 or RTM6 and HF620. This confirms that in this case there is no reaction with the epoxy resin.

[0239] These results also highlight the influence of epoxy functionality on the resins tested. In the case of the RTM6 and HF620 resins, the epoxies are tetrafunctional, whereas in the case of the EP2400 and EP2410 resins, they are trifunctional. This means that there are fewer accessible epoxy groups in the case of the latter two resins, which results in a slower reactivity with the porous layer, as is especially seen in the case of the porous layer CP8, which reacted particularly quickly with the RTM6 and HF620 resins. However, this leaves time for the other porous layers (CP1, CP5) to react.

[0240] VII. Effect of Porous Layer Reactivity on Composite Mechanical Properties As shown in Table 5, seven reinforcements, four materials according to the invention, and four materials for comparative purposes were compared. [Table 5]

[0241] The conditions used to produce a unidirectional carbon web bonded to porous layers on both sides are shown in Table 6 below. [Table 6]

[0242] A 340 mm x 340 mm preform consisting of a stacking sequence adapted to the carbon basis weight was placed in an injection mould under a press. A frame of known thickness surrounding the preform made it possible to obtain the desired fibre volume ratio FVR.

[0243] An epoxy resin marketed by Hexcel under the reference HexFlow RTM6 was injected at 80° C. under 2 bar through a preform maintained at 120° C. in a press. The pressure exerted by the press was 5.5 bar. After the preform was filled and the resin had left the mold, the outlet pipe was closed and the heat treatment cycle started: 3° C. / min to 180° C., followed by heating to 180° C. for 2 hours and cooling to 5° C. / min.

[0244] The specimens were then cut to appropriate dimensions and subjected to compression after impact (CAI), in-plane shear (IPS), and open hole compression (OHC) tests as summarized in Table 7. [Table 7]

[0245] The results obtained in all these tests are shown in Tables 8 to 10. The mechanical results presented demonstrate 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), the mechanical properties showing sensitivity to holes such as open hole compression (OHC) or in-plane shear (IPS).

[0246] On the one hand, epoxy powder (comparative material 1) solves the problem of carrying out all steps of the dry preform manufacturing process at temperatures between 80 and 130 °C, but does not produce composite parts with optimal mechanical properties. On the other hand, conventional polyamide veil (comparative material 2) gives optimal mechanical properties but requires higher temperatures for manufacturing and molding. In contrast, the material according to the invention addresses both problems.

[0247] Thus, materials 3 to 6 according to the invention make it possible to combine both a manufacturing and molding process at temperatures below 130 ° C and optimal mechanical properties of the composite parts. It should also be emphasized that the mechanical performance is comparable, regardless of what material is used in 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 if the porous layer does not modify the gel time of the RTM6 resin (material 3 with CP1 layer or material 5 with CP5 layer). Thus, in all cases, in the materials according to the invention, the reactive functional group / epoxy functional group reaction is sufficient to prevent a decrease in the mechanical properties of the obtained composite part due to the presence of the porous layer, despite its low melting point. Likewise, in the materials according to the invention, the mechanical properties are found to be comparable to those obtained with the comparative material 7a, in which the thermoplastic CP7a layer is partially crosslinked.

[0248] The IPS performance is also improved over the comparative material 7. [Table 8] [Table 9]

[0249] As can be seen from Table 9, the OHC performance is the same or even better than the material according to the invention. [Table 10]

[0250] For 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, whereas they are comparable to those obtained with comparative material 2, which requires higher temperature molding.

[0251] VIII. Effect of Porous Layer Reactivity on Stability During Temperature Conditioning The tests carried out showed that the composite parts obtained by bonding a reinforcement containing a thermoplastic porous layer with RTM6 resin have two transitions when subjected to temperature stress: the first transition corresponds to the glass transition of the porous thermoplastic layer enriched with epoxy resin and occurs at a temperature below 100°C, while the second transition corresponds to the glass transition of the epoxy matrix and occurs at a temperature of about 200°C.

[0252] Most aging of composites in contact with aggressive fluids is performed at temperatures up to 70°C for various lengths of contact time. When comparative material 2 (with CP9-1R8D04 porous layer) is aged at 70°C, a change in the glass transition of the epoxy-rich thermoplastic porous layer was observed due to the curing and phase separation of the epoxy resin. An example of the results is shown in Figure 14, which shows the response of the material to DMA stress (DMA curves obtained with and without conditioning at 70°C for 14 days: 2°C / min from 25°C to 270°C). The transition changes significantly from about 60°C to about 100°C when aging at 70°C, while the glass transition of RTM6 does not change (not shown).

[0253] Conversely, when using a porous layer according to the invention for materials 5 and 6 according to the invention (Figures 15 and 16, respectively), it is clear that the glass transition of the thermoplastic porous layer, which may have reacted with an epoxy resin, remains relatively stable when aged at 70° C. This is because there is no phase separation between the two chemically reacted materials when the RTM6 resin cures.

[0254] This confirms the results obtained by optical microscopy and shows that the reaction between the porous layer according to the invention and the resin minimizes the effect 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 present invention, since the presence of the porous layer recommended in the present invention does not seem to affect the thermomechanical properties of the thermosetting resin.

Claims

1. 1. A reinforcement (1) comprising at least one fibrous reinforcement (2) having a thermoplastic porous layer (4, 5) bonded to at least one of the faces of the fibrous reinforcement (2), wherein said thermoplastic porous layer(s) (4, 5) represent up to 10% of the total mass of the reinforcement (1), preferably between 0.5 and 10% of the total mass of the reinforcement (1), more preferably between 2 and 6% of the total mass of the reinforcement (1), said fibrous reinforcement (2) being a unidirectional web of reinforcing threads (3), a woven fabric of reinforcing threads or a stack of unidirectional webs of reinforcing threads bonded to each other by needling or any other physical means, wherein said porous thermoplastic layer (4, 5) or layers (4, 5) present each comprise a so-called reactive thermoplastic polymer or consist of one or more reactive thermoplastic polymers, said reactive thermoplastic polymers being present in an amount of -NH ２ A reinforcing material (1) characterized in that it has functional groups and / or has an amount of --COOH functional groups greater than 0.20 meq / g of reactive thermoplastic polymer.

2. The reactive thermoplastic polymer contains -NH 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, more preferably in the range of 0.20 to 0.95 meq / g of reactive thermoplastic polymer. ２ 2. The reinforcement (1) according to claim 1, characterized in that it has functional groups and / or has an amount of -COOH functional groups 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, more preferably in the range of 0.20 to 0.95 meq / g of reactive thermoplastic polymer.

3. 3. Reinforcement (1) according to claim 1 or 2, characterized in that the reactive thermoplastic polymer of the porous thermoplastic layers (4, 5) present in the reinforcement (1) has a melting temperature in the range of 100 to 140°C, preferably in the range of 100 to 130°C.

4. The reactive thermoplastic polymer is ２ Reinforcement (1) according to claim 1 or 2, characterized in that it is a polyamide or copolyamide having functional groups and / or -COOH functional groups.

5. The thermoplastic porous layers (4, 5) present contain -NH in an amount greater than 0.15 meq / g of porous layer. ２ A reinforcing material (1) according to claim 1 or 2, characterized in that it contains more than 0.20 meq / g of -COOH functional groups in the functional group and / or porous layer.

6. 3. Reinforcement (1) according to claim 1 or 2, characterized in that the reactive thermoplastic polymer has a number average molecular weight Mn greater than 4000 g / mol.

7. 3. Reinforcement (1) according to claim 1 or 2, characterized in that the fibre reinforcement (2) consists of glass fibres, aramid fibres or preferably carbon fibres.

8. 3. A reinforcement (1) according to claim 1 or 2, characterized in that the reinforcement (1) consists of a unidirectional web of reinforcing threads (3) corresponding to the fibrous reinforcement (2) with the thermoplastic porous layers (4, 5) bonded to at least one of the faces of the fibrous reinforcement (2), preferably the reinforcement (1) consists of a unidirectional web of reinforcing threads (3) corresponding to the fibrous reinforcement (2) with the thermoplastic porous layers (4, 5) bonded to each of the faces of the fibrous reinforcement (2), and the thermoplastic porous layers (4, 5) present on each face of the unidirectional web of reinforcing threads (3) are identical.

9. 3. The reinforcing material (1) according to claim 1 or 2, characterized in that the thermoplastic porous layer (4, 5) has high-temperature adhesion, and thanks to the high-temperature adhesion of the thermoplastic porous layer (4, 5), a bond between the fiber reinforcing material (2) and the porous layer is achieved.

10. 3. A reinforcement (1) according to claim 1 or 2, characterized in that the reinforcement (1) consists of a stack of unidirectional webs of reinforcing threads (3) as fibrous reinforcement (2) oriented in different directions, and at least one of the thermoplastic porous layers (4, 5) is interposed between two unidirectional webs of reinforcing threads (3) and / or present on the surface of the stack.

11. The reinforcement (1) has a series of (CP / R) with CP representing the thermoplastic porous layer (4, 5). ｎ (CP) ｍ or (CP / R / CP) ｎ 11. The reinforcement (1) according to claim 10, characterized in that it consists of a superposition of layers corresponding to: R = unidirectional web; n = integer greater than or equal to 1; and m = 0 or 1.

12. 11. Reinforcement (1) according to claim 10, characterized in that the unidirectional webs of reinforcing threads (3) are joined to each other or to the at least one porous thermoplastic layer (4, 5) by sewing, knitting or needling.

13. 3. Reinforcement (1) according to claim 1 or 2, characterized in that the porous thermoplastic layer (4, 5) present is a porous film, a grid, a powder deposit, a woven fabric, or preferably a nonwoven fabric or veil.

14. The following sequential steps: a1) providing a fiber reinforcement (2); a2) containing or consisting of one or more so-called reactive thermoplastic polymers, in which the reactive thermoplastic polymers contain more than 0.15 meq / g of -NH ２ providing at least one thermoplastic porous layer (4, 5) having functional groups and / or wherein the reactive thermoplastic polymer has an amount of —COOH functional groups greater than 0.20 meq / g of the reactive thermoplastic polymer; a3) bonding said fiber reinforcement to said at least one porous thermoplastic layer (4, 5); 3. A method for producing a reinforcement (1) according to claim 1 or 2, characterized in that it comprises:

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

16. A preform consisting at least in part of one or more reinforcing materials (1) according to claim 1 or 2.

17. 3. A method for manufacturing a composite part from at least one reinforcement (1) according to claim 1 or 2, characterized in that an epoxy thermosetting resin is injected or poured into the reinforcement (1) or into a stack of several of the reinforcements (1).

18. A method for producing a composite part from at least one reinforcement (1) as described in claim 1 or 2, characterized in that an epoxy thermosetting resin is injected or poured into a preform consisting at least in part of one or more of said reinforcements (1).

19. The manufacturing method includes a heat treatment step, which comprises heating to a temperature Ta that results in crosslinking of the epoxy thermosetting resin and consolidation of the composite part when the epoxy thermosetting resin is injected or infused into the reinforcement or the stack, during which the epoxy resin forms -NH present on the reactive thermoplastic polymer of the thermoplastic porous layer (4, 5). ２ 18. A method for producing a composite part according to claim 17, characterized in that it reacts with at least a portion of the functional groups and / or -COOH functional groups.

20. The gelation of the epoxy resin occurs during the heat treatment step, and -NH ２ 20. A method for producing a composite part according to claim 19, characterized in that the functional groups and / or -COOH functional groups are reacted with the resin before its gelation.

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

22. A method for manufacturing a composite part as described in claim 18, characterized in that the temperature Ta is higher than the melting temperature of the reactive thermoplastic polymer of at least one porous thermoplastic layer (4, 5).

23. 18. Method for manufacturing a composite part according to claim 17, characterized in that said temperature Ta is below the melting temperature of the reactive thermoplastic polymer of said at least one porous thermoplastic layer (4, 5), preferably such that gelation of the epoxy thermoset resin occurs faster than if it were subjected to the heat treatment step alone.

24. A method for producing a composite part as described in claim 18, characterized in that the temperature Ta is below the melting temperature of the reactive thermoplastic polymer of the at least one porous thermoplastic layer (4, 5), and preferably the gelation of the epoxy thermosetting resin occurs more quickly than if it were subjected to the heat treatment process alone.

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

26. A method for manufacturing a composite part as described in claim 18, characterized in that the temperature Ta is in the range of 120 to 220°C, preferably in the range of 160 to 220°C, more preferably in the range of 170 to 190°C, and typically equal to 180°C.

27. 18. The method of claim 17, wherein the epoxy thermoset resin has a viscosity of less than 1000 mPa.s at a temperature of 90°C.

28. The method of claim 18, wherein the epoxy thermosetting resin has a viscosity of less than 1000 mPa.s at a temperature of 90°C.

29. 18. Method for manufacturing a composite part according to claim 17, characterized in that the manufacturing method comprises, before the infusion or injection of the epoxy thermoset resin, depositing or moulding the reinforcement (1), preferably taking advantage of the high temperature tack of the at least one thermoplastic porous layer (4, 5) present in the reinforcement (1), carrying out a heating preferably carried out at a temperature below 170°C, or even below 150°C, preferably in the range of 100-140°C, more preferably in the range of 100-130°C.

30. A method for producing a composite part according to claim 18, characterized in that the production method comprises depositing or shaping the reinforcement (1) before injecting or injecting the epoxy thermosetting resin, preferably taking advantage of the high temperature tack of the at least one thermoplastic porous layer (4, 5) present in the reinforcement (1), and carrying out heating preferably at a temperature below 170°C, or even below 150°C, preferably in the range of 100-140°C, more preferably in the range of 100-130°C.

31. A composite part obtained by a manufacturing process as defined in claim 17.

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