Intermediate composite element, production process and composite part

Abstract

The present invention relates to an intermediate composite element (200), which comprises: - at least one molded part (3, 300, 301, 310) comprising a reinforcing fiber assembly embedded in a thermosetting polymer matrix, - at least one dry stack (4, 400, 401, 410) of reinforcing fiber layers, comprising at least one polymer porous layer inserted between two consecutive reinforcing fiber layers, the molded part (300) being attached to the surface of the stack and bonded to the latter, characterized in that the thermosetting polymer partially penetrates the thickness of the dry stack (400) from the surface of the attached molded part (300) of the dry stack (400), thereby providing a bond between the dry stack (400) and the molded part (300). The present invention also relates to its production process, the process of producing composite parts using such an element, and the resulting composite parts.

Description

Technical Field

[0001] The present invention relates to the technical field of reinforcing materials suitable for manufacturing composite parts. More specifically, the present invention relates to the technical field of reinforcing materials suitable for producing composite parts combined with injection or infusion of resin. Background Art

[0002] Since composite parts, which include not only one or more fiber reinforcements but also a matrix (usually mainly of the thermosetting type and may include one or more thermoplastics), combine light weight, mechanical properties, and corrosion resistance, they are increasingly used as substitutes for metal parts, especially in the fields of aviation, automotive, and energy.

[0003] The production of composite parts or articles can be carried out by means of two types of processes, namely the so-called "indirect" process and the so-called "direct" or "liquid composite molding" (LCM) process.

[0004] The indirect process uses fiber materials pre-impregnated with polymer resin, and then shapes them by means of a compression molding operation to suit the production of the required composite parts. The fiber prepreg materials include the required amount of resin for the final composite parts. The main production processes for compression molding are:

[0005] - The "sheet molding compound" (SMC) process, in which prepreg sheets are placed in the form of a stack;

[0006] - The "bulk molding compound" (BMC) process, in which chopped fibers mixed with resin are combined in a compression molding operation.

[0007] The prior art proposes the use of chips, especially rectangular chips, which are composed of assemblies impregnated with unidirectional fibers and can be directly positioned randomly in the mold, or can also be used to indirectly form a sheet material in which the chips are randomly arranged and generally extend into the plane of the sheet. The resulting intermediate sheet material is cut to the size of the mold, the stack is placed in the mold, and then compression molding is carried out. These types of materials can flow during the molding operation and fill all parts of the mold used. Hexcel Corporation (Stamford USA) offers to sell this type of sheet material under the name of of.

[0008] Although such compression molding processes are particularly suitable for producing three-dimensional parts with complex shapes, they still have limitations for producing large parts.

[0009] The direct process is defined as using one or more fiber reinforcements in the "dry" state (i.e., without the final matrix), and separately preparing the resin to be used as the matrix for shaping, for example, by injecting it into a mold containing the fiber reinforcement (resin transfer molding (RTM) process), by infusing through the thickness of the fiber reinforcement (liquid resin infusion (LRI) process or resin film infusion (RFI) process), or even by continuously manually coating / impregnating each individual layer of the fiber reinforcement with a roller or brush.

[0010] For the RTM, LRI or RFI processes, it is generally necessary to first produce a fiber preform or stack in the desired final form, and then impregnate the preform or stack with resin to form the matrix. The resin is injected or infused at a certain temperature by a pressure difference, and then, after the required amount of resin is completely contained in the preform, the assembly is raised to a higher temperature to complete the polymerization / crosslinking cycle and thereby cure it.

[0011] Examples of materials suitable for the direct process include fiber reinforcements, where unidirectional sheets of reinforcing fibers (especially carbon) are combined with two thin veils of thermoplastic fibers bonded to both sides of the unidirectional sheet. Such materials are described in particular in applications EP 1125728, US6828016, WO 00 / 58083, WO 2007 / 015706, WO 2006 / 121961, US 6503856, US 2008 / 7435693, WO 2010 / 046609, WO 2010 / 061114, EP 2547816, US 2008 / 0289743, US 2007 / 8361262, US2011 / 9371604 and WO 2011 / 048340.

[0012] Multi-axial reinforcements (commonly known as "non-crimp fabrics" (NCF)) are also ideally used in the direct process. Such multi-axial reinforcements are described in particular in applications EP 2547816 and WO 2010 / 067003, and consist of a stack of several unidirectional layers of reinforcing fibers (especially carbon, glass or aramid) arranged along several orientations and stitched together.

[0013] Thus, the direct process and the indirect process employ various materials, devices and processes.

[0014] In the prior art, various processes or devices have been proposed, especially for producing three-dimensional parts with more or less complex shapes.

[0015] Application WO 2016 / 207309 proposes a prepreg molding process that uses at least one blank of molding material, the blank including a guide that, during molding, guides the molding material to be molded so that it flows into the cavity of a compression mold, thereby enabling the acquisition of complex shapes with surface ribs. The reinforcing fiber material is or of the prepreg type. The material can be easily thermoformed into a three-dimensional arrangement, the material consisting of fragments of unidirectional tapes impregnated with a thermosetting resin, configured in a quasi-isotropic arrangement to form a layer of fiber material.

[0016] Application WO 2017 / 029121 describes an alternative solution that includes a mold for producing composite parts by compression molding, the mold including an inner insert having walls that can move independently to increase or decrease the size of the insert.

[0017] This application also proposes combining various materials or intermediate elements to produce specific parts, particularly when these parts have portions with various shapes or complexities, or even portions subject to various stresses.

[0018] Specifically, in the prior art, it has been proposed to join two molded parts together by gluing or riveting, which can lead to brittleness at the interface and require additional assembly steps. Specifically, a molded composite part forming ribs or protrusions can be attached to another molded composite part using such techniques. However, it is generally considered that simple gluing is not sufficient, particularly for aerospace parts, and should be supplemented by mechanical joining such as riveting (see specifically Advisory Circular No. 20-107 of the United States Department of Transportation Federal Aviation Administration on August 9, 2009 and Section 23.573(a) of Title 14 of the United States Code of Federal Regulations), which requires the use of appropriate tools and additional joining steps.

[0019] However, Application WO 2014 / 168701 proposes a multi-component structure produced from various materials: a moldable component having a complex geometry consisting of fragments of unidirectional tapes pre-impregnated with a type thermosetting resin; and a structural component consisting of unidirectional fibers pre-impregnated with a thermosetting resin, which are combined and molded in a single step by curing the thermosetting resin. By selecting the coefficient of thermal expansion of the structural component and the moldable component, microcracks at the interface between the two components during high-temperature molding are minimized. To this end, it is proposed to integrate continuous fibers oriented in various directions into the structural component. Each of the components includes 25% - 45% by weight of a thermosetting resin.

[0020] Other documents have proposed processes suitable for producing extremely specific parts: Document US 2019 / 338881 describes a tubular fastener for repairing a pipeline with a gasket, the gasket including a first part composed of reinforcing fibers and a substantially fully cured resin composition, and a second part into which the resin composition penetrates, the second part being composed of dry fibers, in particular felt. On the other hand, document DE 102014009446 describes an attachment element including a thermoplastic molded part into which a fiber layer 11 is inserted. The fiber layer has two parts: a part fully embedded in the molded part, and two dry parts 11.1 extending outside the molded part, which are not impregnated with the thermoplastic material. Then, by impregnating the dry parts with a thermosetting resin, a composite part including the attachment point is obtained.

[0021] In this context, the present invention proposes new intermediate composite elements, a process for producing such new intermediate composite elements, and an implementation in a process for producing composite parts, which provide more adaptation options according to direct or indirect devices that can be used at certain sites, and which are more suitable for producing parts with various shapes and sizes. Specifically, the present invention is ideally suited for producing composite parts with complex shapes, such as parts including ribs or protrusions. The process according to the present invention can be easily adapted to various types of composite parts, and composite parts with good mechanical stress resistance can be obtained. Specifically, the present invention proposes an intermediate composite element and a process that uses various parts required to manufacture a composite part including the intermediate composite element and then assembles them, and forms a compliant connection at the joint between the two parts. Summary of the Invention

[0022] First, the present invention relates to an intermediate composite element, which includes:

[0023] - at least one molded part including a reinforcing fiber assembly embedded in a thermosetting polymer matrix,

[0024] - at least one dry stack of reinforcing fiber layers, specifically including at least one porous polymer layer inserted between two consecutive reinforcing fiber layers, the molded part being attached to and bonded to the surface of the stack, characterized in that the thermosetting polymer partially penetrates the thickness of the dry stack from the surface of the attached molded part of the dry stack, thereby forming a bond between the dry stack and the molded part.

[0025] In the context of the present invention, the thermosetting polymer forming the polymer matrix of the molded part also penetrates the thickness of the dry stack. This penetration allows for the formation of a firm bond between the molded part and the dry stack. Thus, there is no need to supplement this bond with additional mechanical bonding. Moreover, advantageously, in the context of the present invention, the bond between the molded part and the dry stack is not provided by mechanical fastening means such as rivets, screws, etc. In addition, such an intermediate composite element is ideally suited for the production of complex composite parts in combination with an injection or infusion resin that penetrates, in particular, into the dry stack, by a direct process. In fact, since the thermosetting polymer only partially penetrates the thickness of the stack, it is necessary to supplement the dry stack by adding a polymer matrix during the production process of the composite part. Specifically, the dry stack comprises from 4 to 20 layers of reinforcing fibers, preferably from 8 to 16 layers of reinforcing fibers, and at least 2 layers of reinforcing fibers in the dry stack, preferably at least 4 layers of reinforcing fibers, do not contain any thermosetting polymer that has penetrated from the molded part. These layers are located on the outer part of the stack opposite to the surface connected to the molded part.

[0026] Advantageously, in the intermediate composite element, the dry stack of reinforcing fiber layers has an average thickness of at least 5 mm, and the thermosetting polymer penetrates the thickness of the stack partially from the surface of the stack with an average penetration depth of at least 2 mm. By this penetration, regardless of the thickness of the dry stack, the bond between the dry stack and the molded part is compliant and enables good shear resistance to be obtained at the interface of the final composite part obtained from the intermediate composite element. In the context of the present invention, the average thickness and the average penetration depth of the stack can be measured by making 10 measurements perpendicular to the plane of the interface between the molded part and the dry stack and then calculating the arithmetic mean of these measured values. Such measurements can be carried out by cutting the intermediate composite element as described in the examples. Another way to characterize the permeability of the thermosetting polymer is to observe the number of layers of reinforcing fibers in the dry stack into which the thermosetting polymer has penetrated as described above.

[0027] In the context of the present invention, the dry stack is called "dry" because it comprises a polymer portion that represents at most 10% of the total weight of the stack, preferably from 0.5% to 10% of the total weight of the stack, more preferably from 2% to 6% of the total weight of the stack, and this polymer portion contributes at least partially to the cohesion of the stack. This polymer portion does not include the amount of thermosetting polymer that has penetrated the dry stack.

[0028] This polymer portion can specifically be a thermoplastic polymer, a polymer comprising a thermoplastic portion, or a mixture of such polymers.

[0029] The intermediate composite element according to the invention has integral and cohesive properties. Thus, not only are the molded part and the dry stack bonded to each other, but the dry stack also forms a fixed part, i.e., the reinforcing fiber layers of the dry stack (also referred to as fiber layers) are bonded to each other. Such bonding can be achieved by mechanical bonding such as stitching or weaving, or alternatively can be achieved by the polymer portions contained in the dry stack as described below.

[0030] According to one embodiment, the reinforcing fiber layer is a fabric.

[0031] According to a preferred embodiment, the reinforcing fiber layer is a unidirectional reinforcing fiber sheet preferably oriented in at least two different directions.

[0032] According to one embodiment, the dry stack is formed from one or more non-crimp fabrics (NCF), each NCF being an assembly of a plurality of unidirectional reinforcing fiber sheets oriented in at least two different directions and bonded by stitching or weaving. In such a case, the dry stack can be formed from one or more NCFs, each NCF being an assembly of a number of unidirectional reinforcing fiber sheets oriented in at least two different directions and bonded by stitching or weaving, and there may be one or more porous polymer layers on the surface or between the unidirectional layers.

[0033] When the fiber layers are fabrics or preferably unidirectional reinforcing fiber sheets, whether in the form of NCFs or not, at least one porous polymer layer is inserted between two consecutive fabrics or two consecutive unidirectional reinforcing fiber sheets. This enables the mechanical properties of the composite part to be optimized.

[0034] Specifically, regardless of the method of implementing the invention, the porous polymer layer present in the dry stack is a porous membrane, grid, powder coating, fabric, or preferably a non-woven fabric or a thin felt.

[0035] By using such a porous polymer layer, the dry stack can have cohesive properties, at least in part due to the thermo-bonding properties of the porous polymer layer present between two fiber layers.

[0036] Generally, the reinforcing fibers of the dry stack and / or the molded part are glass fibers, carbon fibers, aramid fibers or ceramic fibers, particularly preferably carbon fibers.

[0037] According to a preferred embodiment particularly suitable for the production of complex molded parts, the molded part is obtained by molding unidirectional fiber fragments impregnated with a thermosetting resin, the fragments preferably forming an intermediate mat in which the fragments are randomly arranged. Specifically, the fragments are rectangular or substantially rectangular and preferably have a length of 1 cm to 10 cm, a width of 2 mm to 2 cm and a thickness of 0.02 mm to 0.50 mm.

[0038] In the context of the present invention, a "complex part", and thus, in particular, a "complex molded part", specifically refers to a part that has at least one non-developable surface and a developable surface corresponding to a ruled surface, i.e., whose tangent plane is the same along the generatrix. Examples include parts with non-constant thickness or T-shaped parts, or T-shaped parts. Such molded parts can specifically be obtained by conventional compression molding techniques.

[0039] Specifically, in the intermediate composite element according to the present invention, the thermosetting polymer of the molded part is an epoxide.

[0040] Generally speaking, the thermosetting polymer matrix accounts for at least 25% of the weight of the molded part, preferably 25% to 55% of the weight of the molded part.

[0041] Advantageously, in the intermediate composite element according to the present invention, the dry stack includes 4 to 20 layers of reinforcing fibers, preferably 8 to 16 layers of reinforcing fibers.

[0042] According to certain embodiments of the present invention, the molded part has a complex shape compared to the shape of the stack. Specifically, the molded part has the shape of a hinge, attachment point, rib, ribbed beam, support, bracket, channel, bracket, fork, reinforcement, hatch frame, door frame, lever arm, base, fitting, joint, socket, or pivot.

[0043] Another feature of the present invention relates to a process for producing an intermediate composite element, which intermediate composite element comprises:

[0044] - at least one molded part, which comprises a reinforcing fiber assembly embedded in a thermosetting polymer matrix,

[0045] - at least one dry stack of layers of reinforcing fibers, specifically comprising at least one porous polymer layer inserted between two consecutive layers of reinforcing fibers, the molded part being attached to and bonded to the surface of the stack, and the production process comprising the following consecutive steps:

[0046] a - attaching at least one reinforcing fiber assembly pre-impregnated with a thermosetting polymer to the surface area of an initial dry stack of sheets of reinforcing fibers, which initial dry stack specifically comprises at least one polymer porous layer inserted between two consecutive layers of reinforcing fibers, specifically comprising at least one porous polymer layer inserted between two consecutive layers of reinforcing fibers;

[0047] b - performing a thermocompression molding operation on the reinforcing fiber assembly pre-impregnated with a thermosetting polymer deposited on the initial dry stack of sheets of reinforcing fibers in a mold, thereby causing the thermosetting polymer to crosslink and partially penetrate into the thickness of the stack;

[0048] c - Cooling is carried out to obtain a molded part including a reinforcing fiber assembly embedded in a thermosetting polymer, forming a matrix, and the thermosetting polymer partially penetrates from the surface part of the attached molded part of the dry stack into the thickness of the dry stack, and the molded part is bonded to the dry stack of the reinforcing fiber layers thus obtained as a result of such penetration of the thermosetting polymer.

[0049] Such a process enables the production of intermediate composite elements according to the present invention, especially intermediate composite elements of complex shapes, through a compression molding process accompanied by heating that is particularly suitable for producing elements of complex shapes. Therefore, the characteristics of the production process are selected to obtain intermediate composite elements according to the present invention and thus adapt to the characteristics of the present invention.

[0050] In this production process, the assembly of reinforcing fibers pre - impregnated with a thermosetting polymer attached in step a can be in the form of a preform of the desired molded part.

[0051] According to one embodiment, the reinforcing fiber laminae forming the initial dry stack used in step a are reinforcing fiber fabrics, which are combined with a porous polymer layer on at least one side, and the porous polymer layer present in the laminae accounts for at most 10% of the total weight of the laminae, preferably 0.5% to 10% of the total weight of the laminae, and more preferably 2% to 6% of the total weight of the laminae, and at least one porous polymer layer is inserted between two consecutive fabrics.

[0052] According to a preferred embodiment, the reinforcing fiber laminae forming the initial dry stack used in step a are unidirectional reinforcing fiber sheets, which are combined with a porous polymer layer on at least one side, and the porous polymer layer present in the laminae accounts for at most 10% of the total weight of the laminae, preferably 0.5% to 10% of the total weight of the laminae, and more preferably 2% to 6% of the total weight of the laminae, and at least one porous polymer layer is inserted between two consecutive unidirectional reinforcing fiber layers.

[0053] In such a case, particularly preferably, the reinforcing fiber laminae forming the initial dry stack used in step a can consist of unidirectional reinforcing fiber sheets combined with porous polymer layers on both sides, and the porous polymer layers present on both sides of the unidirectional reinforcing fiber sheets are the same.

[0054] The porous polymer layer present in the laminae can have thermo - adhesive properties, and due to the thermo - adhesive properties of the porous polymer layer, a combination of the unidirectional sheets or fabrics forming the laminae and the at least one porous polymer layer is obtained in advance. In the prior art, such laminae are generally used as a means of dry reinforcement.

[0055] Due to the thermo-bonding properties of the existing porous polymer layer, the initial dry stack of the reinforcing fiber laminates employed in step a may also have cohesive properties. Such cohesion aids in its handling and implementation during the production process. In such a case, it is also possible to prefabricate the initial dry stack of the reinforcing fiber laminates employed in step a, particularly when the dry stack is not a simple flat plate.

[0056] In another variant, the initial dry stack of the reinforcing fiber laminates employed in step a is not cohesive, as its cohesion is obtained at the end of step b due to the thermo-bonding properties of the existing porous polymer layer.

[0057] Advantageously, the porous polymer layer present in the laminates of the initial dry stack optionally used in step a comprises, consists of, or is composed of a thermoplastic polymer or a polymer containing a thermoplastic moiety.

[0058] In particular, the porous polymer layer present in the laminates of the initial dry stack used in step a is a porous film, grid, powder coating, fabric, or preferably a non-woven fabric or a thin felt.

[0059] According to another variant, the reinforcing fiber laminates forming the initial dry stack are unidirectional reinforcing fiber sheets oriented in at least two different directions and joined by stitching or weaving. In such a case, the dry stack can be formed from multiple NCFs, each NCF being an assembly of multiple unidirectional sheets oriented in at least two different directions and joined by stitching or weaving, with one or more porous polymer layers possibly present on the surface or between the unidirectional sheets. Conventionally, in the field of NCFs, stitching or weaving can be performed using glass yarns, carbon yarns, basalt yarns, silica yarns, or polyester yarns or yarns made of a thermoplastic polymer, particularly a thermoplastic polymer with a fineness in the range of 5 dTex to 150 dTex, and preferably in the range of 5 dTex to 30 dTex.

[0060] In the production process according to the invention, the reinforcing fibers of the reinforcing fiber laminates of the dry stack and / or the assemblies of prepreg reinforcing fibers are generally glass fibers, carbon fibers, aramid fibers, or ceramic fibers, particularly preferably carbon fibers.

[0061] According to one embodiment, particularly an embodiment ideally suited for the production of molded elements with complex shapes, the reinforcing fibers pre-impregnated with a thermosetting polymer for forming the assembly for forming the molded part are unidirectional fiber fragments impregnated with a thermosetting polymer, which preferably form an intermediate mat in which the fragments are randomly arranged. Advantageously, the fragments are rectangular or substantially rectangular and preferably have a length of 1 cm to 10 cm, a width of 2 mm to 2 cm, and a thickness of 0.02 mm to 0.50 mm.

[0062] Preferably, the thermosetting polymer of the component for forming the molded part is an epoxide. The thermosetting polymer of the component generally used for forming the molded part accounts for at least 25% of the weight of the component, preferably 25% to 55% of the weight of the component.

[0063] In the context of the present invention, the compression molding step b results in the diffusion of the thermosetting polymer, which partially penetrates the thickness of the stack in the interfacial region with the molded part in its final thermoset state. In most cases, the dry stack of the resulting reinforced fiber layers has an average thickness of at least 5 mm, and the thermosetting polymer penetrates the thickness of the stack from the surface of the stack to an average penetration depth of at least 2 mm. Those skilled in the art should adjust the conditions of the molding operation, in particular pressure, temperature and time, to achieve such penetration.

[0064] Generally, in step a, the initial dry stack of the reinforced fiber layers comprises 4 to 20 laminae, preferably 8 to 16 laminae, and advantageously, after step b, at least 2 reinforced fiber layers, preferably at least 4 reinforced fiber layers in the obtained dry stack do not contain any thermosetting polymer that has penetrated from the molded part.

[0065] According to a particular embodiment, the dry stack used in step a has incisions or perforations at least in the surface area where the component of the pre-impregnated reinforced fiber is attached. Such incisions or perforations facilitate the attachment of the component of the pre-impregnated reinforced fiber to the dry stack and ultimately obtain a bond between the two parts forming the final intermediate composite element.

[0066] In certain embodiments, for any alternative embodiment applicable to the production process, a mold of appropriate shape is used in step b to obtain a molded part having a complex shape compared to the shape of the stack.

[0067] Specifically, in the context of the present invention, the obtained intermediate composite element is used to form hinges, attachment points, ribs, ribbed beams, supports, fasteners, channels, brackets, fork rods, reinforcements, hatch frames, door frames, lever arms, bases, fittings, joints, sockets or pivots.

[0068] The present invention also relates to the use of an intermediate composite element according to the invention or an intermediate composite element obtained by a production process described in the context of the present invention for the combined production of composite parts with a thermosetting resin, a thermoplastic resin or a mixture of these resins. Such a process is called a direct process. The resin or resin mixture is infused or injected into the dry stack of the intermediate composite element, and after said infusion or injection, cooling is carried out, preferably using a thermosetting resin and a mixture of thermosetting resins. When using a thermosetting resin or a mixture containing a thermosetting resin, the infusion or injection is carried out under conditions that cause crosslinking of the thermosetting resin.

[0069] Accordingly, the present invention also relates to the so-called direct process for producing composite parts using the intermediate composite element described in the context of the present invention.

[0070] In such a process, it is advantageous to use the intermediate composite element together with other dry reinforcements. According to a first preferred variant, the present invention relates to a process for producing a composite part, which comprises the following steps:

[0071] A1 - providing an intermediate composite element according to the invention or an intermediate composite element produced by a production process according to the invention,

[0072] A2 - attaching said intermediate composite element to at least a part of the surface of a dry stack of reinforcing fiber laminates (referred to as an additional dry stack) such that the dry stack of the intermediate composite element abuts against the additional dry stack,

[0073] A3 - infusing or injecting a thermosetting, thermoplastic resin or a mixture of such resins into the dry stack of the intermediate composite element and the additional dry stack, using conditions that cause crosslinking in the case of a thermosetting resin, and carrying out cooling after said infusion or injection so as to obtain the desired final composite part.

[0074] In the context of the present invention, there is a very good bond between the intermediate composite element and the additional dry stack, since such a bond is of the same type and is provided by the resin infused / injected into the dry stack of the intermediate composite element and the additional dry stack. This bond is provided over the entire surface of the intermediate composite element in contact with the additional dry stack. In addition to the bond obtained by the penetration of the polymer forming the molded part into the dry stack of the intermediate composite element, this also results in a good bond at the interface of the parts forming the part. Therefore, it is not necessary to supplement these bonds with additional mechanical bonds. Furthermore, advantageously, in the context of the present invention, in the final composite part, the bond between the elements of the part corresponding to the molded part and the dry stack of the intermediate composite element, and the bond between the intermediate composite element and the additional dry stack, are not provided by mechanical fastening components such as rivets, screws, etc.

[0075] The reinforcing fiber laminae forming the additional dry stack can be structurally identical to the reinforcing fiber laminae of the dry stack forming the intermediate composite element. While this option is advantageous for the compatibility between the additional dry stack and the intermediate composite element and may promote bonding at the interface, it is not mandatory. In fact, various types of dry reinforcements bonded by infusion / injection of resin generally produce very good cohesion / bonding at the interface between the two reinforcements.

[0076] Furthermore, the process according to the invention is particularly advantageous because it enables the production of intermediate composite elements with smaller dimensions and more complex shapes by means of so-called indirect techniques, in particular by compression molding, then attaching this part to an additional dry stack with larger dimensions, and then implementing a so-called direct process that requires another device such as a vacuum bag type device to produce the final composite part.

[0077] Furthermore, according to certain embodiments of the invention, the intermediate composite element has a complex shape compared to the shape of the additional dry stack. In particular, the intermediate composite element forms hinges, attachment points, ribs, ribbed beams, supports, brackets, channels, tie rods, fork rods, reinforcements, hatch frames, door frames, lever arms, bases, fittings, joints, sockets or pivots in the final composite part obtained.

[0078] Advantageously, the additional dry stack has at least one dimension that is larger than at least one dimension of the intermediate composite element, in particular at least 2 times, preferably at least 4 times the size of at least one dimension of the intermediate composite element. In particular, the additional dry stack has an area that is at least 10 times the size of the area fixing the intermediate composite element.

[0079] In the context of the present invention, the additional dry stack to be used in step A2 can be prefabricated.

[0080] Furthermore, advantageously, the surface of the additional stack fixing the intermediate composite element has one or more surface undulations such as ribs or protrusions, and specifically these surface undulations can be obtained by pre-preforming the additional dry stack. In this case, the presence of the dry stack of the intermediate composite element at the interface with the additional dry stack having a greater deformation capacity than the molded part allows for less restricted adjustment of the relative position of the intermediate composite element and the additional dry stack. Since there are fewer constraints compared to the case of direct assembly with the molded part, faster joining is possible. This thus promotes the bonding / assembly of these two elements.

[0081] Although not a preferred variant of the present invention, it is also possible to use the intermediate composite element in a direct process without any additional reinforcing elements. Thus, the present invention also relates to a process for producing a composite part, which process comprises the following steps:

[0082] B1 - Provide an intermediate composite element according to the present invention or an intermediate composite element obtained by the process described in the context of the present invention,

[0083] B2 - Under conditions that cause cross - linking of the intermediate composite element when using a thermosetting resin, infuse or inject a thermosetting resin, a thermoplastic resin, or a mixture of such resins into the dry stack of the intermediate composite element, and then obtain the desired final composite part by cooling.

[0084] It should be understood that during the production process of the composite part according to the present invention, especially for molded parts and / or dry stacks, it is preferably to achieve the same characteristics as those described for the intermediate composite element or its production process.

[0085] Advantageously, inject or infuse the thermosetting resin, especially epoxy resin, respectively in step A3 or B2 of the process for producing the composite part.

[0086] Using conventional techniques known to those skilled in the art, step A3 or B2 can be carried out respectively by infusion, preferably in an open mold, for example, by vacuum bag infusion technique.

[0087] The present invention also relates to a composite part that can be obtained by one of the processes for manufacturing a composite part described in the context of the present invention.

[0088] Such components particularly correspond to composite parts used in the fields of aviation, automotive, space, defense, industry, or energy. The present invention is particularly suitable for producing three - dimensional parts with complex shapes.

[0089] With reference to the accompanying drawings, the present invention will be better understood from the following detailed description. The documents cited in this specification are attached for reference. Description of the Drawings

[0090] Figure 1 Figure 1 is a schematic cross - sectional view of an intermediate composite element according to the present invention.

[0091] Figure 2 Figure 2 is a schematic cross - sectional view of a composite part according to the present invention.

[0092] Figure 3 Figure 3 is a schematic illustration of the steps involved in the production of an intermediate composite element according to the present invention.

[0093] Figure 4 Figure 4 ​​​​​​​​It is a schematic illustration of steps involved in the production of a composite part from an intermediate composite element according to the present invention, in a first variant of the production process of the composite part according to the present invention.

[0094] Figure 5 Figure 5 It is a schematic illustration of steps involved in the production of a composite part from an intermediate composite element according to the present invention, in a second variant of the production process of the composite part according to the present invention.

[0095] Figure 6A Figure 6A In a perspective view, a complex-shaped intermediate composite element and an additional dry stack (only partially shown) are schematically shown, which are shaped to have a series of ribs.

[0096] Figure 6B Figure 6B Two identical elements with an intermediate composite element are shown, which is attached to an additional dry stack before adding resin to form the final part.

[0097] Figure 6C Figure 6C It is an enlarged view of a part of the intermediate composite element, showing the interface between the molded part and the dry stack, and showing that the thermosetting polymer that also forms the matrix of the molded part locally penetrates into the thickness of the dry stack.

[0098] Figure 7 Figure 7 A photograph corresponding to a partial cross-sectional view of the intermediate composite element is shown, showing the polymer forming the matrix of the molded part penetrating into the dry stack.

[0099] Intermediate composite element

[0100] According to a first feature, the present invention relates to an intermediate composite element for use in combination with an injected or potted resin to produce a composite part. In Figure 1 is schematically shown an intermediate composite element 2 according to the present invention: it includes at least one molded part (illustrated in the example as a single molded part 3) and at least one dry stack (illustrated in the example as a single dry stack 4 of fiber layers 5), the molded part 3 and the dry stack 4 being bonded to each other. The molded part 3 is located on one of the larger sides of the dry fiber stack 4, and the interface 6 corresponding to the bonding area between the molded part 3 and the dry stack 4 can not only correspond to the entire surface of the side of the dry fiber stack 4 on which the molded part 3 is placed, as in the example Figure 1 shown, but can also correspond to only a part of that surface.

[0101] ​​​​​​​​​​The molded part 3 consists of a matrix of one or more thermosetting polymers in which reinforcing fibers are distributed. In the context of the present invention, the term "thermosetting polymer" is used to denote a polymer that is fully thermosetting or even a thermosetting polymer that is not fully thermosetting. Specifically, it is possible that the thermosetting proportion is less than 100%, but generally greater than 70%. Furthermore, in the molded part, although the thermosetting polymer may contain some thermo-crosslinking functionality, the polymer still retains its thermosetting characteristics, that is, even when heated, it cannot return to its original liquid or paste form.

[0102] The thermosetting polymer matrix is obtained by polymerizing / crosslinking a thermosetting polymer or a mixture of thermosetting polymers. The molded part is obtained by compression molding an assembly of reinforcing fibers pre-impregnated with a thermosetting polymer or a mixture of thermosetting polymers. The reinforcing fibers are typically glass, carbon, aramid or ceramic fibers, and specifically preferably carbon fibers. The reinforcing fibers can be found in any type of arrangement known to those skilled in the art and are used in the production of molded composite parts. They can be woven, non-woven, sheets of unidirectional fibers, or preferably chopped fibers or chips made of unidirectional fibers. Specifically, chopped fibers of unidirectional fibers impregnated with a thermosetting polymer can be used to manufacture the molded part. The use of such chips allows for good creep and is particularly suitable for the production of complex molded parts. Specifically, the molded part can be made of rectangular or substantially rectangular chips, which preferably have a length of 1 cm to 10 cm, a width of 2 mm to 2 cm, and a thickness of 0.02 mm to 0.50 mm. Specifically, such chips of unidirectional fibers impregnated with a thermosetting polymer are obtained by impregnating unidirectional fiber rovings and then cutting them, or by cutting sheets impregnated with unidirectional fibers. Such chips can then be laid flat at will and pressed into sheets to form an intermediate mat. For example, such an intermediate mat prepared from chips of pre-impregnated unidirectional fibers corresponds, for example, to the material sold by Hexcel Corporation (Stamford USA). In the case of using chips consisting of unidirectional fibers, within the molded part, if the chips have been randomly arranged before the compression molding operation, the unidirectional reinforcing fibers forming the chips are randomly oriented in three dimensions, or if the chips have been arranged as a stack and subjected to the intermediate mat of the compression molding operation, the unidirectional reinforcing fibers forming the chips are mainly randomly oriented only in two dimensions.

[0103] The thermosetting matrix can correspond to any type of thermosetting polymer in a thermosetting state, namely epoxy resin, phenolic resin, bismaleimide resin or cyanate ester resin, or a mixture of such resins, and epoxy resin is preferred. The molded part contains the amount of thermosetting polymer required in the final composite part. Specifically, the thermosetting polymer matrix accounts for at least 25% of the weight of the molded part, preferably 25% to 55% of the weight of the molded part.

[0104] On the other hand, the dry stack 4 consists of a stack of reinforcing fiber layers 5 positioned on top of each other. The dry stack 4 is cohesive, that is, the reinforcing fiber layers 5 that make it up are bonded together. The stack is described as "dry" because for the production of composite parts, it should be combined with a thermoplastic or thermosetting resin, or a mixture of such resins, specifically with a thermosetting resin. However, the dry stack can also include a polymer part, but the polymer part accounts for at most 15% of the total weight of the dry stack, preferably at most 10%, more preferably 0.5% to 10% of the total weight of the dry stack, and preferably 2% to 6% of the total weight of the dry stack. The polymer part can be a thermosetting polymer, specifically it can be an epoxy resin, a thermoplastic polymer, a polymer including a thermoplastic part or a mixture of such polymers. Specifically, the polymer part is in the form of one or more porous layers inserted between two reinforcing fiber layers 5. It can also include one or more porous layers located on the surface of the dry stack 4 and / or the stitched or woven yarns. Advantageously, the dry stack 4 contains a polymer part that enables the cohesive property of the reinforcing fiber layers 5 to be ensured and gives the dry stack 4 its overall properties.

[0105] The fiber layers 5 of the dry stack 4 can be any type of reinforcing fiber layer suitable for producing composite parts by means of a direct process, specifically it can be a fabric, a non-woven fabric or a unidirectional sheet. Preferably, the reinforcing fiber layers 5 forming the dry stack 4 are all reinforcing fiber fabrics, or more preferably, all unidirectional reinforcing fiber layers.

[0106] Within the dry stack 4, the fiber layers 5 can be different, or, preferably, can all be the same. Again, the reinforcing fibers of the fiber layers 5 are typically glass fibers, carbon fibers, aramid fibers or ceramic fibers, while carbon fibers are particularly preferred. In the context of the present invention, the dry stack 4 includes one or more porous polymer layers inserted between the reinforcing fiber layers 5, specifically to ensure that the stack is cohesive due to the thermo-bonding properties of the polymer. The cohesion of the stack can also be ensured or partially ensured by stitched or woven yarns that link the various fiber layers of the stack or at least some of them together.

[0107] "Porous layer" means a layer that allows the passage of a liquid such as a resin when the composite part is formed, the liquid being injected or infused through a stack containing the liquid. Specifically, the openness factor of such a layer, determined according to the process described in application WO 2011 / 086266, is in the range of 1% to 70%, preferably in the range of 30% to 60%. Examples of porous layers include porous membranes, grids made of interwoven yarns, powder-coated layers, fabrics, and non-woven fabrics. The porous layer is called a polymer because it is composed of a polymer or a mixture of polymers. Specifically, the porous polymer layer can be made of one or more thermoplastic polymers, one or more thermosetting polymers, or a mixture of thermosetting polymers or thermoplastic polymers. Examples of thermoplastic polymers commonly used in dry stacks (and thus for the formation of the porous layers present) include those selected from the following: polyamides (e.g., PA: PA6, PA12, PA11, PA6.6, PA 6.10, PA 6.12), copolyamides (CoPA), polyamide-ether or ester block (PEBAX, PEBA), polyphthalamide (PPA), polyesters (polyethylene terephthalate (e.g., PET), polybutylene terephthalate (e.g., PBT), copolyesters (CoPE), thermoplastic polyurethanes (TPU), polyacetals (e.g., POM), polyolefins (e.g., PP, HDPE, LDPE, LLDPE), polyethersulfones (PES), polysulfones (e.g., PSU), polyphenylsulfones (e.g., PPSU), polyetherketoneketones (PEEK), polyetherketoneketones (PEKK), polyphenylene sulfides (PPS), polyetherimides (PEI), thermoplastic polyimides, liquid crystal polymers (LCP), phenoxies, block copolymers (such as styrene-butadiene-methyl methacrylate (SBM) copolymers, methyl methacrylate-butyl acrylate (MAM) copolymers, and mixtures thereof). The porous polymer layer may also consist of or contain a partially crosslinked thermoplastic polymer, as described in application WO 2019 / 102136. During the subsequent production of the composite part, a person skilled in the art can modify the selection of the (multiple) component polymers of the polymer part of the dry stack according to the choice of the resin to be injected or infused. Advantageously, the polymer part of the dry stack (and thus the (multiple) porous polymer layers present therein) comprises a thermoplastic polymer or a polymer comprising a thermoplastic part or a mixture of such polymers, or consists of a thermoplastic polymer or a polymer comprising a thermoplastic part or a mixture of such polymers.

[0108] To form the intermediate composite element 2, the molding part 3 and the dry stack 4 are joined together. At the interface 6 between the molding part 3 and the dry stack 4, the bond is formed by infiltrating the thermosetting matrix of the dry stack 4. The polymer part present in the dry stack, which may also be present at the interface 6, may also contribute to the formation of this bond.

[0109] In the context of the present invention, the bond between the molding part 3 and the dry stack 4 is strengthened by partially infiltrating the thermosetting matrix from the molding part into the thickness of the stack at the surface 6 of the stack to which it is attached, thereby strengthening the bond between the stack and the molded part. As explained below, this infiltration occurs during the production of the intermediate composite element 2.

[0110] Advantageously, in the intermediate composite element, the dry stack 4 comprises at least two reinforcing fiber layers 5, and the thermosetting polymer infiltrates at least two reinforcing fiber layers 5 of the dry stack 4. Specifically, the dry stack 4 comprises from 4 to 20 reinforcing fiber layers 5, preferably from 8 to 16 reinforcing fiber layers 5, and the thermosetting polymer infiltrates at least two reinforcing fiber layers 5 of the dry stack 4, preferably at least 4 reinforcing fiber layers 5 of the dry stack 4.

[0111] Production process of the intermediate composite element

[0112] The production process of the intermediate composite element according to the present invention is as Figure 3 shown and it comprises the following successive steps:

[0113] a - attaching at least one reinforcing fiber assembly 60 pre - impregnated with a thermosetting polymer to the surface area 70 of the initial dry stack 40 of reinforcing fiber plies 50,

[0114] b - performing a thermocompression molding operation on the reinforcing fiber assembly 60 pre - impregnated with a thermosetting polymer deposited on the dry stack 40 of reinforcing fiber plies, thereby causing the thermosetting polymer to crosslink and partially infiltrate into the thickness of the stack,

[0115] c - cooling, thereby obtaining a molding part 300 which comprises a reinforcing fiber assembly embedded in a matrix corresponding to the thermoset thermosetting polymer, and then joining said molding part also to the stack 400 of reinforcing fiber layers thus obtained by means of the infiltrated thermosetting polymer.

[0116] Any conventional technique known to those skilled in the art can be used to perform the molding operation. The various elements include: the reinforcing fiber assembly 60 impregnated with a thermosetting polymer and the initial dry stack 40 of reinforcing fiber plies 50 are both subjected to a compression molding operation, as Figure 3 shown.

[0117] To this end, the components are typically located in or in a part of an open mold 20. The initial dry stack 40 of the reinforcing fiber laminates 50 can be formed directly in the mold by depositing individual laminates, or the initial dry stack 40 can be pre-formed and deposited in the mold in a single operation.

[0118] Similarly, the reinforced fiber assembly 60 pre-impregnated with a thermosetting polymer can be formed directly in the mold by depositing selected prepregs on the initial dry stack 40, or the reinforced fiber assembly 60 pre-impregnated with a thermosetting polymer can be pre-formed in the form of a preform and deposited on the initial dry stack 40 already present in the mold 20 in a single operation.

[0119] For example, the assembly 60 of prepreg reinforced fibers can correspond to a prepreg assembly of long fibers, short fibers or staple fibers, including a stack of prepreg materials in the form of sheets of prepreg reinforced fiber material, specifically prepreg fabrics or prepreg unidirectional tapes, BMC (bulk molding compound) or SMC (sheet molding compound) prepreg materials. Specifically, it is the series of prepreg fabrics and prepreg unidirectional tapes available from Hexcel Corporation (Stamford USA).

[0120] Advantageously, the thermosetting polymer assembly 60 of prepreg reinforced fibers can be made of rectangular or substantially rectangular pieces, which preferably have a length of 1 cm to 10 cm, a width of 2 mm to 2 cm and a thickness of 0.02 mm to 0.50 mm. Specifically, such unidirectional fiber pieces impregnated with a thermosetting polymer are obtained by impregnating unidirectional fiber rovings (which are then cut), or by cutting sheets impregnated with unidirectional fibers. Such pieces can then be randomly laid flat and pressed into a sheet to form an intermediate mat. For example, such an intermediate mat prepared from impregnated unidirectional fiber pieces corresponds to, for example, the materials sold by Hexcel Corporation (Stamford USA). In the case of using pieces composed of unidirectional fibers, within the molded part, if the pieces have been randomly arranged before the compression molding operation, the unidirectional reinforcing fibers forming the pieces are randomly oriented in three dimensions, or if the pieces have been arranged as a stack and subjected to an intermediate mat of the compression molding operation, the unidirectional reinforcing fibers forming the pieces are mainly randomly oriented in only two dimensions. For example, the hot compression conditions and firing cycles applicable to this type of material are described in Application WO 2016 / 207309, and reference can be made to this application for more details.

[0121] "Fiber-reinforced laminate" refers to a material composed of one or more layers, which has an integral or cohesive property, i.e., the various layers are bonded together. Within the fiber-reinforced laminate 50, there is at least one reinforcing fiber layer. Such a reinforcing fiber layer can be in the form of a fabric, a unidirectional sheet, or a non-woven fabric made of reinforcing fibers. According to a preferred embodiment, each laminate includes a unidirectional reinforcing fiber sheet, and these various unidirectional reinforcing fiber sheets are oriented in different directions in the dry stack 40, which is conventional in the art.

[0122] Laminate in which the reinforcing fiber layer is a fabric can also be used.

[0123] The dry stack 40 in the intermediate composite element 2 will correspond to the dry stack 4 and can thus be considered a precursor stack of the latter. Thus, the initial dry stack 40 of the fiber-reinforced laminate 50 includes at least one porous polymer layer inserted between two reinforcing fiber layers.

[0124] The reinforcing fibers are specifically glass fibers, carbon fibers, aramid fibers, or ceramic fibers, and carbon fibers are particularly preferred. The fiber-reinforced laminate 50 can also contain a polymer portion, but in a smaller amount to maintain the dry property of the initial dry stack 40. Specifically, if the fiber-reinforced laminate has a polymer portion, the polymer portion accounts for at most 15% of the total weight of the fiber-reinforced laminate, preferably at most 10%, and preferably 0.5% to 10% of the total weight of the fiber-reinforced laminate, and more preferably 2% to 6% of the total weight of the fiber-reinforced laminate. In this case, specifically, the fiber-reinforced laminate can include a reinforcing fiber layer and a porous polymer layer that are integral (related) to each other. If the polymer portion is bonded to the fiber reinforcement, it is considered part of the fiber-reinforced laminate. If the polymer portion is not bonded to the fiber-reinforced laminate, although it is necessarily part of the initial dry stack 40, it is still considered to have been deposited on the fiber-reinforced laminate or inserted between two fiber-reinforced laminates. Thus, the dry stack 40 includes at least one porous polymer layer inserted between two consecutive laminates 50 or at least one porous polymer layer that belongs to one laminate 50 in the dry stack 40 and is positioned in contact with another laminate 50 in the dry stack 40. However, ultimately, the initial dry stack 40 includes a polymer portion that accounts for at most 15% of the total weight of the fiber-reinforced laminate, preferably at most 10%, and preferably 0.5% to 10% of the total weight of the fiber-reinforced laminate, and more preferably 2% to 6% of the total weight of the fiber-reinforced laminate.

[0125] According to a first alternative embodiment, the reinforcing fiber laminae 50 forming the initial dry stack 40 are fiber reinforcements, in particular unidirectional reinforcing fiber sheets, which are combined with a porous polymer layer on at least one of their sides, and one or more porous polymer layers present in said laminae represent at most 10% of the total weight of the laminae, preferably from 0.5% to 10% of the total weight of the laminae, more preferably from 2% to 6% of the total weight of the laminae, wherein at least one porous polymer layer is inserted between two consecutive fiber reinforcements, in particular between two consecutive unidirectional reinforcing fiber sheets.

[0126] The reinforcing fiber laminae 50 forming the initial dry stack 40 may also be reinforcing fiber fabrics, which are combined with a porous polymer layer on at least one of their sides, and one or more porous polymer layers present in said laminae represent at most 10% of the total weight of the laminae, preferably from 0.5% to 10% of the total weight of the laminae, and more preferably from 2% to 6% of the total weight of the laminae, and at least one porous polymer layer is inserted between two consecutive fabrics.

[0127] "The fiber reinforcement is combined with a porous layer on at least one of its sides" means that the fiber reinforcement is combined with at least one porous layer, and the at least one porous layer is attached to at least one of the sides of the fiber reinforcement. Specifically, due to the thermo-bonding properties of the porous polymer layer, this combination is specifically formed by gluing. For this combination, in particular in the case of a stack comprising a plurality of fiber reinforcements and a plurality of porous polymer layers, it is also possible to supplement or replace it by mechanical combinations of the stitching or weaving type or by any other physical means (such as needle punching).

[0128] Specifically, the porous polymer layer is a non-woven fabric. The terms "non-woven fabric" and the equivalent term "web" generally refer to assemblies composed of continuously or randomly arranged short fibers. For example, these non-woven fabrics or webs can be produced by dry processes ("dry laying"), wet processes ("wet laying"), by melting ("spunbond"), for example by extrusion ("spunbond"), by extrusion blow molding ("meltblown"), by melt spraying ("fiber sprayer") or solvent spinning well-known to those skilled in the art ("electrospinning", "flash spinning", "force spinning"). Specifically, the fibers forming the non-woven fabric have an average diameter in the range of 0.5 μm to 70 μm, and preferably in the range of 0.5 μm to 20 μm. The non-woven fabric can be formed of short fibers or preferably of continuous fibers. In the case of a non-woven fabric of short fibers, the fibers can have a length, for example, from 1 mm to 100 mm. The non-woven fabric provides a random covering, preferably an isotropic covering.

[0129] Advantageously, the non-woven fabric present in the initial dry stack 40 has a weight of 0.2 g / m 2The weight per unit area within the range of from 0 to 20 g / m2. The thickness of the non-woven fabric in the reinforcing material according to the present invention can vary depending on the nature of the combination with the fiber reinforcement. Preferably, after combination with the fiber reinforcement, each of the non-woven fabrics present in the initial dry stack 40 has a thickness of from 0.5 μm to 50 μm, and when the combination is achieved by applying heat and pressure, this thickness is preferably from 3 μm to 35 μm in order to utilize the thermal bonding characteristics of the non-woven fabric. When combined by mechanical means such as stitching, weaving or needle punching, the thickness of the non-woven fabric may be greater than 50 μm, specifically in the range of from 50 μm to 200 μm. The characteristics of such non-woven fabrics can be determined by means of the method described in application WO 2010 / 046609.

[0130] Dry fabrics with powder or polymer veils can be obtained from Hexcel in series, and there are even G0926 powder-coated fabrics and 48302 veil fabrics.

[0131] Preferably, as the reinforcing fiber laminate 50, those reinforcing fiber laminates composed of unidirectional reinforcing fiber sheets corresponding to the fiber reinforcement are used, which are combined with the porous layer provided in the context of the present invention on at least one of their sides. In order to have a symmetric material, the fiber reinforcement, specifically the unidirectional reinforcing fiber sheet, is combined with the porous layer on both of its sides, as provided in the context of the present invention, and preferably, the porous layers present on both sides of the unidirectional reinforcing fiber sheet are the same. In the context of the present invention, the porous layer has thermal bonding characteristics, and due to the thermal bonding characteristics of the porous layer, the combination of the fiber reinforcement and the porous layer is advantageously achieved, thereby forming a single laminate. These thermal bonding characteristics come from the polymer constituting the porous layer, which is preferably a thermoplastic polymer, or a polymer including a thermoplastic part or a mixture of such polymers. If the stack of the single reinforcing fiber laminate 50 is pre-stacked and combined in the form of a preform before being positioned in the mold, this adhesion characteristic will also impart a cohesive characteristic to the resulting dry stack.

[0132] Such reinforcing fiber laminates 50 are described in WO 2010 / 046609, WO 2010 / 061114, US 2008 / 7435693, US 2010 / 003881, EP1125728, WO 2007 / 015706, WO 2006 / 121961 and US 6503856, and more details can be referred to these documents. In these documents, the component reinforcing yarns constituting the unidirectional sheet can be untwisted. Twisted reinforcing yarns can also be used to form the unidirectional sheet, advantageously using yarns individually twisted at a twist of from 3 to 15 turns / m, preferably from 6 to 12 turns / m.

[0133] In a second alternative embodiment, the reinforcing fiber laminate 50 forming the initial dry stack 40 comprises a plurality of unidirectional reinforcing fiber layers oriented in different directions and joined by stitching or weaving. Specifically, the reinforcing fiber laminate 50 consists of a stack of unidirectional reinforcing fiber layers oriented in different directions, and preferably, as described above, at least one porous polymer layer is inserted between two unidirectional reinforcing fiber sheets, or even on the surface of the stack. According to a first embodiment of this second variant, such a fiber-reinforced laminate can be made from a stack corresponding to the sequence (CM / R) n where CM represents a porous polymer layer as provided in the context of the present invention, R represents a fiber reinforcement as described in the context of the present invention, n represents an integer, specifically 1, 2 or 3, and where, preferably, all CM layers have the same or almost the same weight.

[0134] In a second embodiment of this second alternative embodiment, such a fiber-reinforced laminate can be made from a stack corresponding to the (CM / R) n / CM sequence, where CM represents a porous polymer layer as provided in the context of the present invention, R represents a fiber reinforcement as described in the context of the present invention, n represents an integer, specifically 1, 2 or 3, and where, preferably, all porous CM layers have the same or almost the same weight, or the outer porous layer has a weight equal to half of the weight of each of the inner porous polymer layers.

[0135] Specifically, in such a stack, the fiber reinforcement R is preferably a unidirectional reinforcing fiber sheet having the same weight, and specifically is a carbon fiber. Such a material is referred to as NCF (non-crimp fabric). Generally, in the field of NCF, the joining between unidirectional reinforcing fiber layers with each other and with the existing (multiple) porous layers is achieved by stitching or weaving. Of course, the joining can be by stitching or weaving, by adhesion due to the thermo-bonding properties of the porous polymer layer, or by any other means of physical joining type (such as needling to replace or even supplement the joining), and the porous polymer layer is preferably made of a thermoplastic polymer or a polymer comprising a thermoplastic part or a mixture of such polymers).

[0136] Specifically, in the case of NCF, the fiber-reinforced laminate according to the invention consists of unidirectional plies that extend in various orientations selected from 0°, 30°, 45°, 60°, 90°, 120°, 135°. All of the plies or only some of them may have different orientations. As an example, the fiber-reinforced laminate according to the invention may be made in 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°, 0° corresponds to the forward direction of the machine used to produce the reinforcement according to the invention. In the case of the joining implemented by stitching or weaving, the total direction of the stitching or weaving yarns also generally corresponds to 0°. The production of such multi-axial parts is well known and uses conventional techniques described, for example, by Tsu Wei Chou and Franck K. Ko in the book "Textile Structural Composites, Composite Materials Series Volume 3" (ISBN 0-444-42992-1, Elsevier Science Publishers B.V., 1989, Chapter 5, Paragraph 3.3) or in patent FR2761380, which describes the process and apparatus for producing multi-axial fiber sheets. Specifically, the unidirectional plies may be formed before the multi-axial sheet is formed or applied online when the multi-axial sheet is formed. The stitching or weaving joining between the individual unidirectional plies can be achieved by means of stitching or weaving stitches that extend along lines parallel to each other.Specifically, the stitched or braided threads are spaced apart at regular intervals within the same thread, which intervals are preferably the same, ranging from 1 mm to 20 mm, preferably from 2 mm to 12 mm. Similarly, for example, two consecutive stitched or braided threads are spaced 2 mm to 50 mm apart, preferably 5 mm to 15 mm apart. Preferably, all consecutive stitches of a series of threads parallel to each other should be equally spaced. Among the examples of materials that constitute a stitching yarn particularly suitable in the context of the present invention, there are glass, carbon, basalt, silica, thermoplastic yarns, specifically made of polymers selected from polyester (PET), polypropylene (PP), polyethylene (PE), polyphenylene sulfide (PPS), polyethylene naphthalate (PEN), liquid crystal polymer (LCP), polyketone, polyamide, and mixtures thereof. Polyethylene terephthalate, polybutylene terephthalate, polypropylene terephthalate, polylactic acid, and their copolymers are examples of polyesters that can be used. For example, the fineness of the yarn is in the range of 5 dTex to 150 dTex, specifically less than 30 dTex, for example, determined according to EN ISO 2060. Further details regarding certain configurations that can be used for NCF-type materials can be found specifically in the documents EP 2547816 or WO 2010 / 067003.

[0137] Examples of NCF are described in the documents US 8361262, US 9,371,604, WO 2011 / 113751, and EP 2491175, and further details can be referred to in these documents. Again, the component reinforcing yarns can be untwisted. Twisted reinforcing yarns can also be used to form unidirectional sheets, advantageously using yarns individually twisted with a twist of 3 to 15 turns / meter, preferably 6 to 12 turns / meter.

[0138] Once the individual components are positioned in the mold, any suitable technique known to those skilled in the art is then used to perform the thermocompression molding operation b. The purpose of this operation is first to form and consolidate the molded part 300 after cooling. The shape obtained for the molded part 300 corresponds to the desired shape, which is its final shape in the final molded part 100. Accordingly, the shape of the mold 80 is adjusted accordingly. Compression molding is carried out by applying pressure and heat. Typically, those skilled in the art select the temperature, pressure, thermal cycle, and curing time based on the amount and properties of the thermosetting polymer present in the prepreg reinforced fiber assembly 60. As an example, for all the necessary details regarding the process and the thermosetting polymers that can be used, reference can be made to application WO 2016 / 207309. Specifically, the thermosetting polymer present in the prepreg reinforced fiber assembly is an epoxy resin, a phenolic resin, a bismaleimide resin, or a cyanate ester resin, or a mixture of such resins, with epoxy resin being preferred. The thermosetting resin contains a curing agent suitable for achieving crosslinking / curing. Specifically, the thermosetting polymer accounts for at least 25% by weight of the prepreg reinforced fiber assembly, preferably 25% to 55% by weight of the prepreg reinforced fiber assembly.

[0139] Typically, for example, compression molding is carried out in a temperature range of 100°C to 400°C, in a pressure range of 0.2 MPa to 2000 MPa, including a time period of 15 seconds to 2 hours. Those skilled in the art can modify the selection of these parameters, specifically based on the properties of the thermosetting polymer and its amount, which is a function of the mold size.

[0140] When the initial dry stack 40 includes a thermoplastic part, the compression molding step b also has an impact on this thermoplastic part. Specifically, it can cause the melting or even crosslinking of the (multiple) porous polymer layers present. However, due to the relatively small amount of the polymer part in the dry stack 400 thus obtained, such a transformation will not hinder the subsequent resin diffusion by injection or infusion, which is necessary for the production of the composite part.

[0141] The compression molding step b also makes it possible to obtain a bond between the dry stack 400 and the molded part 300 after cooling, thus forming the intermediate composite element 200, because during molding, the thermosetting polymer also diffuses at the interface 600 with the dry stack 400 and hardens after cooling, and thus fixes the two parts at the interface. In fact, after applying pressure and heat, during the compression molding operation, the polymer partially penetrates the thickness of the dry stack 400. Additionally, as Figure 3As shown, in the case where the prepreg reinforcing fiber assembly 60 includes short fibers (including unidirectional fiber fragments), creep may occur in the reinforcing fibers and the polymer of the prepreg reinforcing fiber assembly 60, and thus the contact area 600 between the molded part and the dry stack is greater than the initial contact area 70, which corresponds to the surface onto which the prepreg reinforcing fiber assembly 60 of the dry stack 40 is deposited. This creep also allows the prepreg reinforcing fiber assembly 60 to fully conform to the inner wall of the mold 80, thereby obtaining a molded part 300 with a complex shape.

[0142] The cooling step c is usually carried out outside the mold. However, cooling can also be carried out in the mold, usually by maintaining the pressure applied to the mold.

[0143] One of the advantages of the present invention is that the compression molding step b also causes a part of the thermosetting polymer present in the prepreg reinforcing fiber assembly 60 to diffuse from the interface 600 into the initial dry stack 40. Thus, at the end of the compression molding step b, when the resin is in its thermoset state, the thermosetting resin partially penetrates into the thickness of the dry stack 400 at the interface 600 with the molded part 300, which enhances the bonding between the obtained dry stack 400 and the molded part 300. Specifically, such diffusion occurs to a thickness of at least 2 mm from the interface 600. Generally, the initial dry stack 40 includes 4 to 20 reinforcing fiber laminae, preferably including 8 - 16 reinforcing fiber laminae 50, and the thermosetting polymer penetrates at least two reinforcing fiber laminae 50 of the dry stack, specifically penetrates at least 4 reinforcing fiber laminae (including reinforcing fiber layers) of the dry stack 400, and the dry stack is present in the obtained intermediate composite element 200 at the end of the molding operation. According to Figure 7The photograph taken with a Zeiss AxioImager M2m optical microscope as shown is obvious, and this photograph is a cross-sectional view of the intermediate reinforcement material according to the present invention. The boundary line a corresponds to the interface between the molded part (above) and the dry stack (below). The inclusion resin is added to the dry stack, so that the area of the dry stack previously impregnated with the thermosetting polymer can be emphasized. This photograph shows a sample placed in a mold and then covered with the inclusion resin to hold it in place. The automatic polishing program performed by Struers Tegramin-25 provides a flat and flawless surface for microscopic observation. The boundary line b corresponds to the inclusion resin c / area interface of the dry stack impregnated with the thermosetting polymer. It can be seen that the line b is much lower than the line a, and the distance between these two lines corresponds to the thickness of the dry stack into which the thermosetting polymer (also present in the molded part) penetrates. However, the reinforcing fiber laminae still remain in the dry stack where the polymer from the molded part has not penetrated. Specifically, in the dry stack 400 present in the intermediate composite element 200, at least 2, preferably at least 4, reinforcing fiber laminae do not contain the thermosetting polymer that has penetrated from the molded part 300.

[0144] Certain modifications can be made to this process to facilitate the adhesion of the prepreg reinforcing fiber assembly 60 to the dry stack and ultimately obtain a bond between the two parts that make up the final intermediate composite element 200. Specifically, in the area of the surface 70 of the reinforcing fiber assembly 60 pre-impregnated with the thermosetting polymer, incisions or perforations can be formed. By way of example, such incisions or perforations can have a maximum size of 2 mm to 150 mm.

[0145] At the end of step b, the intermediate composite element can be removed from the mold and transferred to another device suitable for producing composite parts by a direct process.

[0146] Composite parts and the production process of composite parts

[0147] According to Figure 4 The first variant shown, the present invention relates to a process for producing a composite part 100, which comprises the following steps:

[0148] A1 - Provide an intermediate composite element 200 according to the present invention or an intermediate composite element obtained by the production process of the intermediate composite element according to the present invention,

[0149] A2 - Attach the intermediate composite element 200 to at least a part of the surface of a dry stack of reinforcing fiber laminae (referred to as an additional dry stack 700) such that the dry stack 400 of the intermediate composite element 200 abuts the additional dry stack 700

[0150] Injecting or pouring a thermosetting resin, a thermoplastic resin, or a mixture of such resins into both the dry stack 400 of the intermediate composite element 200 and the additional dry stack 700, and the injection or pouring is then cooled to obtain the desired final composite part 100. In the case where the resin is a thermosetting resin or the resin includes a thermosetting resin, the pouring or injection is carried out under conditions that cause the crosslinking of the thermosetting resin, which is typically achieved by an appropriate curing cycle.

[0151] In the context of the present invention, the portion of the dry stack 400 located on the additional dry stack 700 does not contain a thermosetting polymer and thus has a certain flexibility in conforming to the surface of the additional dry stack. In step A3, in addition to diffusing into the additional dry stack 700, the resin also diffuses into the portion of the dry stack 400 available for such diffusion. A temperature process cycle is implemented in step A3, which results in the consolidation of the assembly and the final part 100 after cooling.

[0152] Again, the additional dry stack 700 is described as "dry" because for the production of the composite part, it should be combined with a thermoplastic or thermosetting resin, specifically it may be mixed with a thermosetting resin. Thus, the additional dry stack 700 may include a polymer portion, but the polymer portion accounts for at most 15% of the total weight of the additional dry stack 700, preferably at most 10%, and preferably accounts for 0.5% to 10% of the total weight of the additional dry stack 700, more preferably 2% to 6%. Specifically, the polymer portion may be in the form of one or more layers embedded in the fiber-reinforced laminae, or in the form of stitched or woven yarns, inserted between two reinforcing fiber layers and / or located on the surface of the additional dry stack 700. Specifically, the dry stack 700 includes at least one porous polymer layer inserted between two consecutive fiber-reinforced laminae, or includes a fiber-reinforced lamina that contains at least one polymer porous layer positioned opposite to another fiber-reinforced lamina in the dry stack 700.

[0153] The interface 900 between the intermediate composite element 200 and the additional dry stack 700 passes through the dry stack 400. This portion of the dry stack does not include any thermosetting polymer that has penetrated from the molded portion into the thickness of the dry stack attached to the additional dry stack 700. Thus, at the interface 900, there is an interface between two dry materials into which the injected / poured resin can penetrate and cure during step A3.

[0154] Any fiber-reinforced lamina used for the initial dry stack 40 is suitable for the additional dry stack 700. The reinforcing fiber laminae 800 that make up the additional dry stack 700 may be structurally the same as or different from those that make up the initial dry stack 40 of the intermediate composite element 200, which is used to form the intermediate composite element 200. For example, NCF-type laminae may be used in the additional dry stack 700, while the dry stack 400 of the intermediate composite element 200 consists of a fabric or unidirectional sheets bonded only by means of a polymer interlayer.

[0155] The first variant is particularly advantageous because it combines the advantages of direct and indirect processes. Complex molded parts can be manufactured by an indirect process and then combined with simpler but larger parts, which are then consolidated by a direct process. The intermediate bond between the dry stack 400 in the intermediate composite element 200 and the molded part 300 provides a particularly strong bond between the two parts. Specifically, one or more intermediate composite elements for forming ribs or protrusions may be attached to the surface of the additional dry stack to form the main part of the final composite part.

[0156] By depositing the reinforcing fiber laminae individually, the additional dry stack 700 of the reinforcing fiber laminae can be formed directly in equipment suitable for the direct process, or the stack can be preformed in a device into which the resin 10 is subsequently injected or infused and deposited in a single operation. In the second case, the additional dry stack 700 may be in the form of a preform adjusted to the desired shape of the final composite part 100.

[0157] The processes of lamina placement and preform production are well known to those skilled in the art.

[0158] Figures 6A to 6B This situation is illustrated. Figure 6A The additional dry stack 702 is shown, or more precisely, the part of the additional dry stack having the surface to which the intermediate composite element 202 is to be attached is shown. The additional dry stack 702 is preformed and has a series of ribs 710. As for the intermediate composite element 202, it has a complex shape and it includes a seat 210 and a clamping plane 220. The seat 210 also has a series of tracks 230 into which the ribs 710 can be inserted. As Figure 6B shown, the final composite part obtained after resin infusion / injection into an assembly of two elements attached to each other can be used specifically in the construction of aircraft landing gear.

[0159] Figure 6C is shown in close-up Figure 6Aa portion of the intermediate composite element 202 therein, which shows the molded portion 310 and the dry stack 410 in the seat 210. In the region 420 of the dry stack 410 extending from the molded portion 310, there is penetration of a thermosetting polymer that has diffused during molding and has spread into the molded portion to partially impregnate the dry stack 410. The remaining portion of the dry stack 410 is dry and free of thermosetting polymer and has greater flexibility to conform to the surface of an additional dry stack 702 that has been shaped, specifically in the region of the ribs 710.

[0160] Generally, in the direct process of producing composite parts, a thermosetting resin, a thermoplastic resin, or a mixture of a thermosetting resin and a thermoplastic resin is injected or infused into a dry stack.

[0161] In the context of the present invention, in the case where there is a thermoplastic portion in the porous polymer layer present in the additional dry stack 700, prior to infusing or injecting the resin, the thermo-bonding properties of at least one of the porous polymer layers present can be utilized for deposition or shaping. Advantageously, in this case, the process includes a preliminary step of constituting the additional dry stack 700 and a step of depositing or shaping a layer of reinforcing fibers for forming the stack, where the porous polymer layer is heated to a temperature that can cause at least partial melting of the (multiple) porous layer defined in the context of the present invention, specifically heated to a temperature in the range from 80 °C to 130 °C, preferably heated to a temperature in the range from 80 °C to 120 °C.

[0162] Those skilled in the art are already familiar with the deposition processes that can be used to form stacks, which are directly used in a device that will subsequently be used for infusing or injecting resin, or for producing a flat preform, or even for producing a preform of the desired three-dimensional shape.

[0163] According to Figure 5 the second alternative embodiment shown, although not preferred, the present invention relates to a process for producing a composite part 101 that includes the following steps:

[0164] B1 - providing an intermediate composite part 201 obtained according to the present invention or according to a process described in the context of the present invention,

[0165] B2 - under conditions that cause cross-linking of the intermediate composite element in the case of using a thermosetting resin, infusing or injecting a thermosetting resin, a thermoplastic resin 10, or a mixture of such resins into the dry stack of the intermediate composite element, and subsequently obtaining the desired final composite part 101 by cooling.

[0166] In this case, the intermediate composite element 201, which consists only of the molded part 301 and the dry stack 401, undergoes a direct process, in which the molded part 301 and the dry stack 401 are joined together by a thermosetting polymer penetrating partially into the thickness of the dry stack 401, and the thermosetting polymer forms the polymer matrix of the molded part 301. In the example shown, a vacuum bag type device 30 is used to inject the resin 10. Then the resin is diffused into the part of the dry stack 401 available for such diffusion.

[0167] Regardless of the process used to produce the composite part, when producing a composite part by a direct process, as a final step, it includes a diffusion step that infuses or injects a thermosetting resin, a thermoplastic resin, or a mixture of a thermosetting resin and a thermoplastic resin into the existing dry stack, followed by a step of consolidating the desired part by a polymerization / crosslinking step according to a specified temperature cycle under pressure, and a cooling step. According to a specific embodiment that is equally applicable to all alternative embodiments described according to the present invention, the diffusion, consolidation, and cooling steps are carried out in an open or closed mold, particularly in an open mold, for example by means of vacuum bag infusion technology.

[0168] Specifically, the diffusing resin can be of the thermoplastic type or preferably of the thermosetting type, or can consist of a mixture of a thermosetting resin and a thermoplastic resin. Examples of thermoplastic resins include polyamides, polyesters, polyamide-imides, polyether sulfones, polyimides, polyether ketones, polymethyl methacrylates, aromatic polyethers, etc. Thermosetting resins that can be used are particularly selected from epoxides, unsaturated polyesters, vinyl esters, phenolic resins, polyimides, bismaleimides, phenol-formaldehyde resins, urea-formaldehyde resins, 1,3,5-triazine-2,4,6-triamine, benzoxazines, cyanates, and mixtures thereof. Such resins can also include one or more curing agents known to those skilled in the art for use with the selected thermosetting polymer. Preferably, the present invention is implemented by using a thermosetting resin, particularly an epoxy resin, during the infusion or injection step. There is already a mechanical bond in the molded part where the polymer matrix has been crosslinked. However, it is preferred to use an injection or infusion resin whose chemical family is the same as that of the resin present in the molded part, or even the same as that of the polymer part present in the dry stack. This facilitates obtaining the same type of structural properties.

[0169] The present invention preferably uses a thermosetting resin to be infused under reduced pressure, particularly at a pressure below atmospheric pressure, particularly below 100 kPa and preferably between 10 kPa and 100 kPa, to produce a composite part. The infusion is preferably carried out in an open mold, for example by means of vacuum bag infusion technology.

[0170] After the heat treatment step, a composite part is finally obtained. Specifically, the composite part is typically obtained by performing the heat treatment recommended by the suppliers of these polymers and known to those skilled in the art, through the conventional consolidation cycles of the polymers involved. By polymerizing / crosslinking according to the defined temperature and pressure cycles and then cooling, this consolidation step of the required composite part is carried out. In the case of thermosetting resins, there is usually a gelling step before the resin cures. The pressure applied during the processing cycle is lower in the case of vacuum infusion and higher in the case of injection into an RTM mold.

[0171] In the context of the present invention, the intermediate composite part is produced by a first compression molding process, while the final composite part is produced by resin infusion / injection. Thus, these two manufacturing steps, which require different equipment, can be carried out at the same manufacturing site and integrated into a single production line, or at two different sites depending on technical limitations and available resources.

[0172] The composite part thus obtained is the main part of the present invention. Figure 2 Such a composite part 1 is schematically illustrated. The composite part includes a molded part 3 and a part 7 including a reinforcing fiber layer 8 impregnated with a thermoplastic matrix or a thermosetting matrix (not shown), which is formed by implementing a direct process.

[0173] At the interface 9 with the molded part, there is penetration of the thermosetting polymer of the molded part. According to Figure 4 the process described, such a part can be obtained from Figure 1 the intermediate composite element 2 shown, in which case some of the reinforcing fiber layers 8 forming part 7 correspond to the reinforcing fiber layers 5 forming the dry stack.

[0174] The present invention is applicable to the production of various composite parts in the fields of aviation, automotive, space, defense, industry or energy. Examples of such parts are: wing panels, fuselages, landing gear doors, movable panels, doors, wing boxes, nacelles, fuselage panels, vertical or horizontal tails, self-reinforcing plates, floors, fairings, monocoque chassis, etc. Examples

[0175] The examples described below are used to illustrate the present invention but do not limit the scope of the present invention.

[0176] There are various intermediate composite elements available on the market. For the production of the molded part, a material or fabric pre-impregnated with a thermosetting resin called M81 sold by Hexcel Corporation (Stamford USA) is used. It is a high-performance compression molding material for producing parts with complex shapes. It is made of long carbon fibers (50 mm) and contains 38% thermosetting resin by weight. M81 is a prepreg fabric impregnated with 42% epoxy resin by weight and weighing 200 g / m 2 2.

[0177] For the production of dry stacks, whether corresponding to dry stacks present in the intermediate composite or additional dry stacks for producing the final composite part, unidirectional layers of carbon fibers, namely IMA 12K fibers produced by Hexcel, are bonded on both sides to a 4 g / m 2 copolyamide thin felt type 1R8 polymer adhesive produced by Protechnic. Due to the thermo-bonding properties of the thin felt, the combination of the unidirectional sheet and the thin felt is achieved. As described in application WO 2010 / 046609, the polymer adhesive is bonded to the carbon. Hereinafter, such a unidirectional thin felt / unidirectional sheet combination is referred to as a "dry ply" (or "ply" in Tables 1 and 2 below). Such dry plies are specifically described in application EP 2342073.

[0178] For injection molding, an epoxy resin numbered RTM6 sold by Hexcel Corporation (Stamford USA) for primary and secondary aircraft structures is used.

[0179] Tables 1 and 2 below summarize the various intermediate composites and parts produced according to the present invention.

[0180] Table 1:

[0181]

[0182] Table 2:

[0183]

[0184] Three 180 mm × 180 mm plies are cut from a 460 mm-wide roll using a die-cut press, placed in an oven at 180 °C for 10 minutes, and then cooled to room temperature (22 °C). The dry 200 mm × 200 mm ply and or or ply are overlapped and then placed in a mold preheated to 180 °C. The interface between the prepreg assembly and the dry stack accounts for 80% of the upper surface of the dry stack. The mold is closed using a press, and a pressure of 100 bar is applied at 180 °C for 20 minutes. The intermediate composite element is recovered without pre-cooling the mold. Cooling is carried out outside the mold.

[0185] After inclusion of the resin, the interface between the molded part and the dry stack obtained using a ZEISS Axio Imager M2m optical microscope was observed, and an intermediate composite element was observed. A sample of the obtained intermediate composite element was placed in a mold and then coated with inclusion resin to fix it in place, and images were taken. An automatic polishing program was performed using a Struers Tegramin-25 to obtain a flat and flawless surface for microscopic observation. These observations clearly demonstrated that the thermosetting polymer supplied by had penetrated into the dry stack at the interface. This penetration was visible in , which was a photograph taken at the interface of the intermediate composite element 2 shown in Table 1. Figure 7 The observations in Figure 7 showed that the penetration occurred to a depth of 2 mm, reaching 3 to 5 laminae in the dry stack. Figure 7 The obtained intermediate composite element was then placed alone in a mold (composite part I) or on an additional dry stack (composite parts II to IV) to form the parts shown in Table 2. HexFlow RTM6 epoxy resin sold by Hexcel was infused into a mold equipped with a vacuum infusion system at 80 °C under a pressure of 1 bar and maintained at a temperature of 120 °C. The mold was then filled with epoxy resin, and the vacuum bag infusion system was placed in the mold. When the preform was filled and the resin came out of the mold, the outlet tube was closed and the curing cycle was started (heating to 180 °C at a rate of 3 °C / min, then post-curing at 180 °C for 2 h and cooling at a rate of 5 °C / min).

[0186] The specimens were then cut to the appropriate size according to ASTM D 2344 for shear testing in a plane corresponding to the interface between the molded part / dry stack in the resin matrix. The specimens were placed on two support points (tip radius 1.5 mm) spaced 4 times the specimen thickness apart, and a punch (tip radius 1.5 mm) was placed on the opposite side of the specimen at the midpoint between the two support points. Values ranging from 41 MPa to 56 MPa were obtained depending on the configuration, and the results fully met the requirements. No significant differences were found in the shear strength data for parts I and II, indicating that performing the direct process with an additional dry stack had no effect on the interlaminar shear strength of the resulting parts.

[0187] ​

Claims

1. An intermediate composite element (2, 200, 201, 202), comprising: - at least one molded part (3, 300, 301, 310) comprising a reinforcing fiber assembly embedded in a thermosetting polymer matrix, - at least one dry stack (4, 400, 401, 410) of reinforcing fiber layers (5), comprising at least one porous polymer layer inserted between two consecutive reinforcing fiber layers (5), The molded part (3, 300, 301, 310) is attached to and bonded to the surface of the dry stack, characterized in that the thermosetting polymer partially penetrates the thickness of the dry stack (4, 400, 401, 410) from the surface of the dry stack (4, 400, 401, 410) to which the molded part (3, 300, 301, 310) is attached, thereby providing a bond between the dry stack (4, 400, 401, 410) and the molded part (3, 300, 301, 310).

2. The intermediate composite element (2, 200, 201, 202) according to claim 1, characterized in that The dry stack (4, 400, 401, 410) of reinforcing fiber layers (5) has an average thickness of at least 5 mm, and the thermosetting polymer partially penetrates the thickness of the stack from the surface of the stack to an average penetration depth of at least 2 mm.

3. The intermediate composite element (2, 200, 201, 202) according to claim 1 or 2, characterized in that The dry stack (4, 400, 401, 410) comprises a polymer part that accounts for at most 10% of the total weight of the stack, and the polymer part at least partially contributes to the cohesion of the stack.

4. The intermediate composite element (2, 200, 201, 202) according to claim 1 or 2, characterized in that The dry stack (4, 400, 401, 410) comprises a polymer part that accounts for 0.5% to 10% of the total weight of the stack, and the polymer part at least partially contributes to the cohesion of the stack.

5. The intermediate composite element (2, 200, 201, 202) according to claim 1 or 2, characterized in that The dry stack (4, 400, 401, 410) comprises a polymer part that accounts for 2% to 6% of the total weight of the stack, and the polymer part at least partially contributes to the cohesion of the stack.

6. The intermediate composite element (2, 200, 201, 202) according to any one of claims 3 to 5, characterized in that The polymer part is a thermoplastic polymer, a polymer containing a thermoplastic part, or a mixture of such polymers.

7. The intermediate composite element (2, 200, 201, 202) according to any one of claims 1 to 6, characterized in that The reinforcing fiber layer (5) is a fabric.

8. The intermediate composite element (2, 200, 201, 202) according to any one of claims 1 to 6, characterized in that, The reinforcing fiber layer (5) is a unidirectional reinforcing fiber sheet oriented in at least two different directions.

9. The intermediate composite element (2, 200, 201, 202) according to claim 8, characterized in that The dry stack (4, 400, 401, 410) is formed of one or more non-crimp fabrics (NCF), each NCF being an assembly of a plurality of unidirectional reinforcing fiber sheets oriented in at least two different directions and joined by stitching or weaving.

10. The intermediate composite element (2, 200, 201, 202) according to claim 8, characterized in that, The dry stack (4, 400, 401, 410) is formed of one or more NCF, each NCF being an assembly of a plurality of unidirectional reinforcing fiber sheets oriented in at least two different directions, with one or more porous polymer layers present on the surface, and the assembly being joined by stitching or weaving.

11. The intermediate composite element (2, 200, 201, 202) according to any one of claims 1 to 10, characterized in that, The porous polymer layer present is a porous membrane, grid, powder coating, fabric.

12. The intermediate composite element (2, 200, 201, 202) according to any one of claims 1 to 10, characterized in that, The porous polymer layer present is a non-woven fabric or a thin felt.

13. The intermediate composite element (2, 200, 201, 202) according to any one of claims 1 to 12, characterized in that, The cohesiveness of the dry stack (4, 400, 401, 410) is obtained at least in part due to the thermo - bonding properties of the porous polymer layer present between two layers of reinforcing fibers (5).

14. The intermediate composite element (2, 200, 201, 202) according to any one of claims 1 to 13, characterized in that, The reinforcing fibers of the dry stack (4, 400, 401, 410) and / or the molded part (3, 300, 301, 310) are glass fibers, carbon fibers, aramid fibers or ceramic fibers.

15. The intermediate composite element (2, 200, 201, 202) according to any one of claims 1 to 13, characterized in that, The reinforcing fibers of the dry stack (4, 400, 401, 410) and / or the molded part (3, 300, 301, 310) are carbon fibers.

16. The intermediate composite element (2, 200, 201, 202) according to any one of claims 1 to 13, characterized in that, The molded part (3, 300, 301, 310) is obtained by molding unidirectional fiber fragments impregnated with a thermosetting resin, the unidirectional fiber fragments forming an intermediate mat in which the unidirectional fiber fragments are randomly arranged.

17. The intermediate composite element (2, 200, 201, 202) according to claim 16, characterized in that, The unidirectional fiber fragments are rectangular or substantially rectangular.

18. The intermediate composite element (2, 200, 201, 202) according to claim 17, characterized in that, The unidirectional fiber fragments have a length of 1 cm to 10 cm, a width of 2 mm to 2 cm, and a thickness of 0.02 mm to 0.50 mm.

19. The intermediate composite element (2, 200, 201, 202) according to any one of claims 1 to 18, characterized in that, The thermosetting polymer of the molded part (3, 300, 301, 310) is an epoxide.

20. The intermediate composite element (2, 200, 201, 202) according to any one of claims 1 to 19, characterized in that, The thermosetting polymer is at least 25% by weight of the molded part (3, 300, 301, 310).

21. The intermediate composite element (2, 200, 201, 202) according to any one of claims 1 to 19, characterized in that, The thermosetting polymer is 25% to 55% by weight of the molded part (3, 300, 301, 310).

22. The intermediate composite element (2, 200, 201, 202) according to any one of claims 1 to 21, characterized in that, The dry stack (4, 400, 401, 410) comprises 4 to 20 layers of reinforcing fibers (5), and advantageously at least 2 layers of reinforcing fibers (5) in the dry stack (4, 400, 401, 410) do not contain any thermosetting polymer that has penetrated from the molded part (3, 300, 301, 310).

23. The intermediate composite element (2, 200, 201, 202) according to any one of claims 1 to 21, characterized in that, The dry stack (4, 400, 401, 410) comprises 8 to 16 layers of reinforcing fibers (5), and advantageously at least 4 layers of reinforcing fibers (5) in the dry stack (4, 400, 401, 410) do not contain any thermosetting polymer that has penetrated from the molded part (3, 300, 301, 310).

24. The intermediate composite element (2, 200, 201, 202) according to any one of claims 1 to 23, characterized in that, The molded part (3, 300, 301, 310) has a complex shape compared to the shape of the stack.

25. The intermediate composite element (2, 200, 201, 202) according to any one of claims 1 to 24, characterized in that, The molded part (3, 300, 301, 310) has the shape of a hinge, attachment point, rib, ribbed beam, support, bracket, channel, tie rod, fork rod, reinforcement, hatch frame, door frame, lever arm, base, fitting, joint, socket or pivot.

26. A method for producing an intermediate composite element (2, 200, 201, 202), comprising: - at least one molded part (3, 300, 301, 310) comprising a reinforcing fiber assembly embedded in a thermosetting polymer matrix, - At least one dry stack (4, 400, 401, 410) of the reinforcing fiber layer (5), comprising at least one polymer porous layer inserted between two consecutive reinforcing fiber layers (5), the molded part (3, 300, 301, 310) being attached and bonded to the surface of the dry stack, and the production method comprising the following consecutive steps: a - Attaching at least one reinforcing fiber assembly (60) pre-impregnated with a thermosetting polymer to the surface area (70) of the initial dry stack (40) of the reinforcing fiber laminae (50), the initial dry stack (40) comprising at least one polymer porous layer inserted between two consecutive reinforcing fiber layers (50); b - Performing a hot compression molding operation on the reinforcing fiber assembly (60) pre-impregnated with a thermosetting polymer deposited on the initial dry stack (40) of the reinforcing fiber laminae (50) in a mold, thereby causing the thermosetting polymer to crosslink and partially penetrate into the thickness of the dry stack; c - Performing a cooling operation, thereby obtaining a molded part (3, 300, 301, 310) comprising a reinforcing fiber assembly embedded in the thermosetting polymer, forming a matrix, the thermosetting polymer partially penetrating from the surface part of the dry stack (4, 400, 401, 410) to which the molded part (3, 300, 301, 310) is attached into the thickness of the dry stack (4, 400, 401, 410), and the molded part (3, 300, 301, 310) being bonded to the dry stack (4, 400, 401, 410) of the thus obtained reinforcing fiber layer (5) as a result of such penetration of the thermosetting polymer.

27. The method for producing an intermediate composite element (2, 200, 201, 202) according to claim 26, characterized in that, The assembly (60) of reinforcing fibers pre-impregnated with a thermosetting polymer attached in step a is in the form of a preform of the required molded part (3, 300, 301, 310).

28. A method for producing an intermediate composite element (2, 200, 201, 202) according to claim 26 or 27, characterized in that, The reinforcing fiber laminae forming the initial dry stack (40) used in step a are unidirectional reinforcing fiber sheets, bonded to a porous polymer layer on at least one of their sides, the porous polymer layer present in the sheets accounting for at most 10% of the total weight of the sheets, and at least one porous polymer layer being inserted between two consecutive unidirectional reinforcing fiber layers.

29. The method for producing an intermediate composite element (2, 200, 201, 202) according to claim 26 or 27, characterized in that, The reinforcing fiber laminae forming the initial dry stack (40) used in step a are unidirectional reinforcing fiber sheets, bonded to a porous polymer layer on at least one of their sides, the porous polymer layer present in the sheets accounting for 0.5% to 10% of the total weight of the sheets, and at least one porous polymer layer being inserted between two consecutive unidirectional reinforcing fiber layers.

30. A method for producing an intermediate composite element (2, 200, 201, 202) according to claim 26 or 27, characterized in that, The reinforcing fiber laminae forming the initial dry stack (40) used in step a are unidirectional reinforcing fiber sheets, bonded to a porous polymer layer on at least one of their sides, the porous polymer layer present in the sheets accounting for 2% to 6% of the total weight of the sheets, and at least one porous polymer layer being inserted between two consecutive unidirectional reinforcing fiber layers.

31. A method for producing an intermediate composite element (2, 200, 201, 202) according to any one of claims 28 to 30, characterized in that, The reinforcing fiber laminate (50) forming the initial dry stack (40) used in step a consists of unidirectional reinforcing fiber sheets bonded to porous polymer layers on both of their sides, and the porous polymer layers on each side of the unidirectional reinforcing fiber sheets are the same.

32. A method for producing an intermediate composite element (2, 200, 201, 202) according to claim 26 or 27, characterized in that, The reinforcing fiber laminate (50) forming the initial dry stack (40) is a fabric made of reinforcing fibers, bonded to a porous polymer layer on at least one of their sides, the porous polymer layer present in the laminate accounting for at most 10% of the total weight of the laminate, and at least one porous polymer layer is inserted between two consecutive fabrics.

33. A method for producing an intermediate composite element (2, 200, 201, 202) according to claim 26 or 27, characterized in that, The reinforcing fiber laminate (50) forming the initial dry stack (40) is a fabric made of reinforcing fibers, bonded to a porous polymer layer on at least one of their sides, the porous polymer layer present in the laminate accounting for 0.5% to 10% of the total weight of the laminate, and at least one porous polymer layer is inserted between two consecutive fabrics.

34. A method for producing an intermediate composite element (2, 200, 201, 202) according to claim 26 or 27, characterized in that, The reinforcing fiber laminate (50) forming the initial dry stack (40) is a fabric made of reinforcing fibers, bonded to a porous polymer layer on at least one of their sides, the porous polymer layer present in the laminate accounting for 2% to 6% of the total weight of the laminate, and at least one porous polymer layer is inserted between two consecutive fabrics.

35. A method for producing an intermediate composite element (2, 200, 201, 202) according to any one of claims 32 to 34, characterized in that, The porous polymer layer present in the laminate exhibits thermo-bonding properties, and due to the thermo-bonding properties of the porous polymer layer, a combination of the unidirectional reinforcing fiber sheets or the fabric forming the laminate and the at least one porous polymer layer is obtained in advance.

36. A method for producing an intermediate composite element (2, 200, 201, 202) according to any one of claims 27 to 35, characterized in that, The initial dry stack (40) of the reinforcing fiber laminate (50) used in step a has cohesiveness obtained due to the thermo-bonding properties of the existing porous polymer layer.

37. The method for producing an intermediate composite element (2, 200, 201, 202) according to claim 36, characterized in that, The initial dry stack (40) of the reinforcing fiber laminate (50) used in step a is preformed.

38. A method for producing an intermediate composite element (2, 200, 201, 202) according to any one of claims 27 to 35, characterized in that, The initial dry stack (40) of the reinforcing fiber laminate (50) used in step a is not cohesive, and its cohesiveness is obtained at the end of step b due to the thermo-bonding properties of the existing porous polymer layer.

39. A method for producing an intermediate composite element (2, 200, 201, 202) according to any one of claims 27 to 38, characterized in that, The porous polymer layer present in the laminate (50) of the initial dry stack (40) used in step a comprises, consists of, or is composed of a thermoplastic polymer or a polymer containing a thermoplastic portion.

40. A method for producing an intermediate composite element (2, 200, 201, 202) according to any one of claims 27 to 39, characterized in that, The porous polymer layer present in the laminate (50) of the initial dry stack (40) used in step a is a porous membrane, grid, powder coating, fabric.

41. A method for producing an intermediate composite element (2, 200, 201, 202) according to any one of claims 27 to 39, characterized in that, The porous polymer layer present in the laminate (50) of the initial dry stack (40) used in step a is a non-woven fabric or a thin felt.

42. A method for producing an intermediate composite element (2, 200, 201, 202) according to claim 26 or 27, characterized in that, The reinforcing fiber laminate (50) forming the initial dry stack (40) is unidirectional reinforcing fiber sheets oriented along at least two different directions and bonded by stitching or weaving.

43. The method for producing an intermediate composite element (2, 200, 201, 202) according to claim 42, characterized in that, The initial dry stack (40) is formed of a plurality of NCFs, each NCF being an assembly of a plurality of unidirectional sheets oriented along at least two different directions and bonded by stitching or weaving, with one or more porous polymer layers present on the surface.

44. A method for producing an intermediate composite element (2, 200, 201, 202) according to claim 42 or 43, characterized in that, The stitching or weaving uses glass yarn, carbon yarn, basalt yarn, silica yarn, polyester yarn, or thermoplastic polymer yarn.

45. The method for producing an intermediate composite element (2, 200, 201, 202) according to claim 44, characterized in that, The yarn is made of a thermoplastic polymer with a fineness in the range of 5 dTex to 150 dTex.

46. The method for producing an intermediate composite element (2, 200, 201, 202) according to claim 44, characterized in that, The yarn is made of a thermoplastic polymer with a fineness in the range of 5 dTex to 30 dTex.

47. A method for producing an intermediate composite element (2, 200, 201, 202) according to any one of claims 26 to 46, characterized in that, The fibers of the reinforcing fiber laminae (50) of the initial dry stack (40) and / or the fibers of the pre-impregnated reinforcing fiber assembly (60) are glass fibers, carbon fibers, aramid fibers, or ceramic fibers.

48. A method for producing an intermediate composite element (2, 200, 201, 202) according to any one of claims 26 to 46, characterized in that, The fibers of the reinforcing fiber laminae (50) of the initial dry stack (40) and / or the fibers of the pre-impregnated reinforcing fiber assembly (60) are carbon fibers.

49. A method for producing an intermediate composite element (2, 200, 201, 202) according to any one of claims 26 to 48, characterized in that, The reinforcing fibers pre-impregnated with a thermosetting polymer for forming the assembly (60) for forming the molded part (3, 300, 301, 310) are unidirectional fiber fragments impregnated with a thermosetting polymer, and the unidirectional fiber fragments form an intermediate mat in which the unidirectional fiber fragments are randomly arranged.

50. The method for producing an intermediate composite element (2, 200, 201, 202) according to claim 49, characterized in that, The unidirectional fiber fragments are rectangular or substantially rectangular.

51. The method for producing an intermediate composite element (2, 200, 201, 202) according to claim 50, characterized in that, The unidirectional fiber fragments have a length of 1 cm to 10 cm, a width of 2 mm to 2 cm, and a thickness of 0.02 mm to 0.50 mm.

52. A method for producing an intermediate composite element (2, 200, 201, 202) according to any one of claims 26 to 51, characterized in that, The thermosetting polymer for forming the assembly (60) for forming the molded part (3, 300, 301, 310) is an epoxide.

53. A method for producing an intermediate composite element (2, 200, 201, 202) according to any one of claims 26 to 52, characterized in that, The thermosetting polymer of the assembly for forming the molded part (3, 300, 301, 310) accounts for at least 25% of the weight of the assembly.

54. A method for producing an intermediate composite element (2, 200, 201, 202) according to any one of claims 26 to 52, characterized in that, The thermosetting polymer of the assembly for forming the molded part (3, 300, 301, 310) accounts for 25% to 55% of the weight of the assembly.

55. A method for producing an intermediate composite element (2, 200, 201, 202) according to any one of claims 26 to 54, characterized in that, The step b of compression molding causes the diffusion of the thermosetting polymer, which finally partially penetrates the thickness of the stack at the interface region with the molded part (3, 300, 301, 310) in its thermoset state. The resulting dry stack of the reinforcing fiber layer (5) has an average thickness of at least 5 mm, and the thermosetting polymer partially penetrates the thickness of the stack from the surface of the stack to an average penetration depth of at least 2 mm.

56. A method for producing an intermediate composite element (2, 200, 201, 202) according to any one of claims 26 to 55, characterized in that, In step a, the initial dry stack (40) of the reinforcing fiber laminae includes 4 to 20 laminae, and advantageously, at the end of step b, at least 2 reinforcing fiber layers (5) of the dry stack (4, 400, 401, 410) do not contain any thermosetting polymer that has penetrated from the molded part (3, 300, 301, 310).

57. A method for producing an intermediate composite element (2, 200, 201, 202) according to any one of claims 26 to 55, characterized in that, In step a, the initial dry stack (40) of the reinforcing fiber laminae includes 8 to 16 laminae, and advantageously, at the end of step b, at least 4 reinforcing fiber layers (5) of the dry stack (4, 400, 401, 410) do not contain any thermosetting polymer that has penetrated from the molded part (3, 300, 301, 310).

58. A method for producing an intermediate composite element (2, 200, 201, 202) according to any one of claims 26 to 57, characterized in that, The initial dry stack (40) used in step a has incisions or perforations at least on the surface to which the reinforcing fiber assembly (60) pre-impregnated with a thermosetting polymer is attached.

59. A method for producing an intermediate composite element (2, 200, 201, 202) according to any one of claims 26 to 58, characterized in that, In step b, a mold with a suitable shape is used to obtain a molded part (3, 300, 301, 310) having a complex shape compared to the shape of the stack.

60. A method for producing an intermediate composite element (2, 200, 201, 202) according to any one of claims 26 to 59, characterized in that, The obtained intermediate composite element (2, 200, 201, 202) is used to form a hinge, attachment point, rib, ribbed beam, support, bracket, channel, tie rod, fork rod, reinforcement, hatch frame, door frame, lever arm, base, fitting, joint, socket or pivot.

61. Use of an intermediate composite element (2, 200, 201, 202) according to any one of claims 1 to 25 or an intermediate composite element (2, 200, 201, 202) obtained by a method according to any one of claims 26 to 60 for the production of a composite part (1, 100, 101) in combination with a thermosetting resin (10), a thermoplastic resin or a mixture of such resins, by pouring or injecting the thermosetting resin (10), the thermoplastic resin or a mixture of such resins into the dry stack (4, 400, 401, 410) of the intermediate composite element (2, 200, 201, 202), using conditions causing its crosslinking in the case of using the thermosetting resin (10), cooling after said pouring or injection, using a thermosetting resin or a mixture of thermosetting resins.

62. A method for producing a composite part (100, 101), comprising the following steps: A1 - providing an intermediate composite element (2, 200, 201, 202) according to any one of claims 1 to 25 or an intermediate composite element (2, 200, 201, 202) obtained by a method according to any one of claims 26 to 60, A2 - attaching the intermediate composite element (2, 200, 201, 202) to at least a part of the surface of a dry stack of reinforcing fiber laminae called an additional dry stack (700, 702) such that the dry stack (4, 400, 410) of the intermediate composite element (2, 200, 202) abuts the additional dry stack (700, 702), A3 - pouring or injecting a thermosetting resin, a thermoplastic resin (10) or a mixture of such resins into the dry stack (4, 400, 410) of the intermediate composite element (2, 200, 202) and the additional dry stack (700, 702), using conditions causing the crosslinking of the thermosetting resin (10) in the case of using the thermosetting resin (10), cooling after said pouring or injection, so as to obtain the desired final composite part (100, 101). Method for producing a composite part (100, 101) according to claim 62, characterized in that, The reinforcing fiber laminae forming the additional dry stack (700, 702) are structurally identical to the reinforcing fiber laminae constituting the dry stack (4, 400, 410) of the intermediate composite element (2, 200, 202).

64. A method for producing the composite part (100, 101) according to claim 62 or 63, characterized in that, The area of the additional dry stack (700, 702) is at least 10 times larger than the area to which the intermediate composite element (2, 200, 201, 202) is attached.

65. A method for producing a composite part (100, 101) according to any one of claims 62 to 64, characterized in that, The additional dry stack (700, 702) used in step A2 is preformed.

66. A method for producing a composite part (100, 101) according to any one of claims 62 to 65, characterized in that, The surface of the additional dry stack (700, 702) to which the intermediate composite element (2, 200, 202) is attached has one or more ribs or surface undulations in the form of protrusions (710).

67. A method for producing a composite part (100, 101) according to any one of claims 62 to 66, characterized in that, In step A3, a thermosetting resin (10) is injected or infused.

68. A method for producing a composite part (100, 101) according to any one of claims 62 to 67, characterized in that, Step A3 is carried out by infusion in an open mold.

69. A method for producing the composite part (100, 101) according to claim 68, characterized in that, The infusion is vacuum bag infusion.

70. The method for producing a composite part (100, 101) according to claim 67, wherein the thermosetting resin (10) is an epoxy resin.

71. A composite part (100, 101) obtained by the production method according to any one of claims 62 to 70.

72. The composite part (100, 101) according to claim 71, which is used in the fields of aviation, automotive, space, defense, industry or energy.

73. An intermediate composite material, comprising: (a) at least one molded part, which includes a reinforcing fiber assembly embedded in a thermosetting polymer matrix, (b) at least one stack of dry reinforcing fiber layers, the stack further including at least one porous polymer material layer inserted between consecutive dry reinforcing fiber layers, and (c) partially penetrating into the stack of dry reinforcing fiber layers through the thermosetting polymer matrix, and the molded part is attached and bonded to the surface of the stack of dry reinforcing fiber layers.

74. The intermediate composite material according to claim 73, wherein the stack of dry reinforcing fibers has an average thickness of at least 5 mm, and the thermosetting polymer partially penetrates the thickness of the stack of dry reinforcing fibers to an average penetration depth of at least 2 mm.

75. The intermediate composite material according to claim 74, wherein the stack of dry reinforcing fibers is selected from: fabric layers that have been joined together by stitching or weaving, unidirectional reinforcing fiber sheets, and non-crimp fabric (NCF) layers.

76. The intermediate composite material according to claim 75, wherein the porous polymer layer is selected from porous membranes, grids, powder coatings, fabrics or non-woven fabrics or thin felts.

77. The intermediate composite material according to claim 76, wherein the stack of dry reinforcing fiber layers includes at least 8 to 16 reinforcing fiber layers, and at least 4 layers do not contain any thermosetting polymer matrix from the molded part.

78. A method for producing an intermediate composite element, comprising: (a) preparing at least one molded part, which includes a reinforcing fiber assembly embedded in a thermosetting polymer matrix; (b) preparing at least one stack of dry reinforcing fiber layers, the stack further including at least one porous polymer material layer inserted between two consecutive reinforcing fiber layers; (c) attaching and bonding the molded part to the surface of at least one stack of dry reinforcing fiber layers to form an assembly; (d) Subject the component to thermocompression molding such that at least a portion of the thermosetting polymer matrix from the molded portion will penetrate at least a portion of the stack of dry reinforcing fiber layers; and (e) Cool the component.

79. The method according to claim 78, wherein the porous polymer layer between the layers of the stack of dry reinforcing fibers is selected from a porous membrane, a grid, a powder coating, a fabric, or a non-woven fabric or a thin felt.

80. The method according to claim 79, wherein the stack of dry reinforcing fiber layers has an average thickness of at least 5 mm, and the thermosetting polymer penetrates the thickness of the stack partially from the surface of the stack to an average penetration depth of at least 2 mm.

Images