Pressurizable elongated reinforcing members and methods for manufacturing parts made from composite materials - Patent Application 20070122997

Abstract

The present invention relates to a pushable elongated reinforcing member (R) comprising a plurality of continuous fibers that are or include unconsolidated fibers, the plurality of continuous fibers forming a first group (F) having a first flexural modulus, and at least one elongated element (E) having a second flexural modulus greater than the first flexural modulus. At least one elongated element (E) is connected to the first group of continuous fibers (F) and transmits a pushable compressive force from the at least one elongated element (E) to the first group of continuous fibers (F) in its longitudinal direction. The present invention also relates to a method for producing a part (P), the method comprising the steps of obtaining a body (B) including a tubular cavity (T), and introducing the pushable elongated reinforcing member (R) and a liquid matrix material into the tubular cavity (T) and allowing the matrix material to solidify.

Description

[Technical Field]

[0001] The present invention generally relates in a first aspect to a pushable elongated reinforcing member, and more particularly to a pushable elongated reinforcing member that combines flexibility with the ability to transmit compressive loads along its length when inserted into a cavity in a body to fabricate a part from a composite material.

[0002] In a second aspect, the present invention also relates to a method of manufacturing a part made from a composite material including the indentable elongated reinforcing members of the first aspect. [Background technology]

[0003] Pushable elongated reinforcing members having the features of the preamble of claim 1 are known in the art.

[0004] Reinforcing fibres can be classified into three main groups according to their length: short or chopped fibres, which have a predefined length of a few millimetres (e.g. 5 mm); long fibres, which have a predefined length of a few centimetres (e.g. 5 cm); and continuous fibres, which are usually supplied in spools of tens or hundreds of metres, the length of which is defined in the manufacturing process according to the size of the part.

[0005] Continuous fibres can simultaneously be classified into two main groups: non-consolidated fibres such as dry fibres (i.e. only fibres in the form of e.g. tows, rovings, threads etc.), dry fibres combined with a binder, prepregs (i.e. fibres combined with uncured thermosetting resins), hybrid or commingled fibres (i.e. reinforcing fibres combined with thermoplastic fibres); and consolidated fibres, i.e. fibres that have been combined with a matrix material and then consolidated by melting and cooling in the case of thermoplastic resins or by curing in the case of thermosetting resins.

[0006] Unconsolidated continuous fibers are very flexible (i.e., have a very low flexural modulus) and can transmit tensile loads in their longitudinal direction, but have negligible or no ability to transmit bending or compressive loads. Consolidated continuous fibers can transmit loads in all directions, but have low flexibility (i.e., have a high flexural modulus).

[0007] In most traditional composite manufacturing techniques, as well as existing CFRAM (Continuous Fiber Reinforced Additive Manufacturing) technologies, the fibers are positioned on a surface, except in the case of pultrusion, where the fibers are pulled through a short die.

[0008] However, in the CFIP (Continuous Fibre Injection Process) technique for producing composite parts as described in EP 3231592 B1, in which continuous fibres are introduced into a cavity in a body to strengthen the part, the fibres are introduced into a tubular cavity simultaneously with the liquid resin by (i) applying pressure to the resin to cause a flow of the resin and a drag force on the fibre bundle, and (ii) applying a pushing force to the fibres at the entrance of the tubular cavity.

[0009] In CFIP, the length / diameter ratio of the tubular cavity is typically very high, e.g., 100, 200, or even higher, which can result in high friction loads resulting primarily from the length and surface roughness of the tubular cavity.

[0010] In CFIP, the number of fibers introduced into the tubular cavity is typically very high: for example, to introduce a fiber volume content of approximately 50% into a 5 mm diameter tubular cavity, a bundle of 11 tows of 24k filaments (total of 264k) is required, which is significantly higher than the number of filaments used in CFRAM technology (typically 1k).

[0011] On the other hand, the stiffness of a fiber bundle is proportional to the stiffness of the constituent filaments or tows, so using slightly stiffer tows can result in a very stiff bundle.

[0012] During the CFIP loading process, it is very common for some of the fiber filaments to break or fray, causing the filaments to jam due to frictional forces, which in turn causes further frictional forces to occur, complicating or impeding the loading process.

[0013] Therefore, in CFIP, the fiber bundle must (i) be flexible to allow the introduction process inside the tubular cavity, especially with a nonlinear path; (ii) transmit the pushing force applied to the fibers at the entrance of the tubular cavity along the fiber bundle, i.e., be able to transmit compressive loads in the longitudinal direction of the fibers; and (iii) avoid or minimize the effects of fiber breakage during the introduction process.

[0014] Due to these differences from traditional composite manufacturing techniques and CFRAM technology, as well as the specific requirements of CFIP technology, commercially available fiber forms (such as tows and yarns) have significant limitations for their application in tubular cavities via CFIP technology.

[0015] Indeed, when used in CFIP, existing unconsolidated fiber morphologies can be subjected to very low compression forces before the fibers buckle and / or break, complicating or hindering the deployment process, whereas existing consolidated fiber morphologies can be subjected to high compression forces, but their low flexibility complicates or hinders the deployment process when deployed into nonlinear tubular cavities.

[0016] Therefore, there is a need to provide an alternative to the deficiencies present in the prior art, specifically to provide a pushable elongated strength member that does not suffer from the above-mentioned drawbacks of the prior art proposals and that achieves an optimal balance between flexibility and pushability, making it particularly suitable for application in CFIP techniques. Summary of the Invention

[0017] To this end, the present invention relates in a first aspect to a pushable elongated reinforcing member comprising a plurality of continuous fibers.

[0018] In contrast to pushable elongate reinforcing members known in the prior art, in one aspect of the present invention, the plurality of continuous fibers are or include unconsolidated fibers and form a first group having a first flexural modulus, and the pushable reinforcing member further includes at least one elongate element having a second flexural modulus greater than the first flexural modulus, the at least one elongate element being connected to the first group of continuous fibers and transmitting a push-compression force in the longitudinal direction from the at least one elongate element to the first group of continuous fibers.

[0019] As used herein, modulus of elasticity, both the first flexural modulus and the second flexural modulus, should be understood to refer to a physical property of a material that is obtained from a standardized test method and quantifies the relationship between stress and strain in bending deformation, and has units of force / area (e.g., N / mm). 2 , MPa).

[0020] Some materials, such as metals, exhibit very similar moduli of elasticity regardless of the loading condition (tension, compression, bending), and the tensile modulus (also known as Young's modulus) is usually used.

[0021] Other materials, such as polymers and composites, behave differently under different loading conditions, and specific standards exist to characterize their mechanical properties. For example, ASTM D790 defines standard test methods for the flexural properties of unreinforced and reinforced plastics.

[0022] Other materials, such as membranes, fabrics, threads, cords, or unconsolidated continuous fibers, can transmit tensile loads only in the tangential or longitudinal direction, i.e., they offer no or no significant resistance when subjected to compressive or bending loads, and therefore their compressive and bending moduli are zero or close to zero.

[0023] When a slender structure is subjected to a longitudinal compressive load, it can buckle when the load reaches a critical value (known as the Euler critical load), at which point the structure's stiffness drops sharply and it loses significantly its ability to withstand the compressive load. This critical load is directly proportional to the flexural modulus of the material.

[0024] Thus, a pushable elongated reinforcing member has been designed for use in CFIP techniques, aiming to provide an optimal balance of pushability and flexibility, based on a combination of (i), (ii), and (iii): (i) a fiber with a low flexural modulus and high flexibility to allow the member to be introduced into a non-linear tubular cavity; (ii) one or more elongated elements with a high flexural modulus (at least 50% higher than the same elongated member without the elongated elements) to allow for the application of a push-compression force before the fiber or element begins to buckle and / or break; and (iii) one or more elements for connecting the elongated elements to the highly flexible continuous fiber.

[0025] The ratio of both components is important. In preferred embodiments, components with a volume fraction of elongated elements in the range of 1.5% to 15%, or 1.5% to 5%, or 3% to 15%, provide the best balance between pushability and flexibility. However, higher volume fractions of elongated elements (between 15% and 75%) can still be a good solution for various applications involving gentle bending or requiring high pushability.

[0026] Thus, the pushable elongate reinforcing members of the first aspect of the present invention, in some embodiments, comprise different types of reinforcing fibres, such as carbon, aramid, glass, natural fibres, or combinations thereof.

[0027] According to one embodiment, the second flexural modulus is at least 10 times greater than the first flexural modulus.

[0028] In one embodiment, the first flexural modulus is less than 10,000 MPa and the second flexural modulus is greater than 10,000 MPa.

[0029] According to an embodiment of the pushable elongate reinforcing member of the first aspect of the present invention, at least one elongate element is connected to the first group of continuous fibers by at least one connecting element.

[0030] The bonding elements are characterized by three main aspects: the type of element, the method used to apply it, and the bond points formed between at least one elongated element and the first group of continuous fibers.

[0031] According to the first aspect of the invention, several variants of its implementation are envisaged: According to the first aspect, the at least one bonding element interconnects the first group of continuous fibers and the at least one elongated element by weaving, wrapping, tying or sewing at least one thread and / or by applying a matrix material, adhesive or binder, such as a thermosetting or thermoplastic polymer (which may be the same as the liquid resin or material used in the introduction process).

[0032] A single connecting element may form one or more bond sites depending on the method used for application: for example, if the connecting element is a knotted thread that is then cut, each connecting element will form one bond site, whereas if the connecting element is a wrapped thread that is applied continuously along the elongate member, the connecting element will form multiple bond sites.

[0033] The distance between the bonded points can therefore be determined by the distance between the bonded elements and / or the method of application of the bonded elements. In one embodiment, the yarn is wound in a non-uniform manner, with regions having continuous windings (low pitch regions), each of which represents a bonded point, and regions with a higher pitch (at least 10 times the low pitch), within which no bonded points are generated. Pitch here refers to the longitudinal distance between corresponding points on adjacent turns.

[0034] In some embodiments, the bonding element provides additional functions in addition to the bonding function, such as electrically insulating the continuous fibers to prevent phenomena such as galvanic corrosion, or in other embodiments, these additional functions are provided by additional outer layers that provide one or more of these additional functions.

[0035] According to an embodiment of the pushable elongate reinforcing member of the first aspect of the present invention, the elongate elements are bonded to the first group of continuous fibers at at least two locations along their length.

[0036] In one embodiment, the at least two spacings are 5 to 50 times the diameter or thickness of the pushable elongate reinforcement member.

[0037] In one embodiment, the elongate element is bonded to the first group of continuous fibers at at least two points along at least 75% of its length, preferably at or near both ends.

[0038] According to one example of this embodiment, the pushable elongated reinforcing member of the first aspect of the present invention includes at least one bonding element that bonds the first group of continuous fibers to the at least one elongated member at the at least two locations, while simultaneously allowing resin to flow through areas of the first group of continuous fibers that are not covered by the at least one bonding element, thereby impregnating the first group of continuous fibers and the at least one elongated member.

[0039] At least one connecting element should be capable of transmitting a large force between the elongated element and the first group of fibers.

[0040] As a representative example, if a 50 cm long section of a pushable elongated reinforcing member having bond points spaced 10 cm apart is introduced into a tubular cavity, at which point the force exerted on the pushable elongated reinforcing member at the entrance to the cavity is 100 N, this force will be distributed over five bond points and the force that the at least one bond element must transmit at each bond point will be approximately 20 N.

[0041] According to one embodiment, at least one elongated element is formed by a second group of continuous fibers.

[0042] In one implementation of this embodiment, the second group of continuous fibers is or includes solidified continuous fibers.

[0043] In other embodiments, at least one elongated element is formed by a second group of continuous fibers made of the same material as the first group of continuous fibers, or is formed by a second group of continuous fibers made of a different material (e.g., metal or glass) to achieve an additional function (e.g., the function of transmitting electrical or optical signals in addition to the function of transmitting compressive forces), and / or has the form of at least one rod, wire, or optical fiber.

[0044] In one embodiment of the pushable elongate reinforcing member according to the first aspect of the present invention, the non-solidifying fibres are dry continuous reinforcing fibres.

[0045] In other embodiments, variations, or supplements to those described above, the non-set fibers include other types of non-set fibers other than dry reinforcing continuous fibers, such as dry fibers combined with a binder, prepregs (i.e., fibers combined with an uncured thermosetting resin), hybrid fibers, or commingled fibers (i.e., reinforcing fibers combined with thermoplastic fibers).

[0046] In one implementation of this embodiment, it should be noted that if all of the first set of continuous fibers are dry reinforcing continuous fibers, the flexural modulus of the dry fibers is 0 or close to 0. Therefore, even if the second flexural modulus is small, the latter will be infinitely higher than the first flexural modulus.

[0047] In other implementations of this embodiment, the first continuous fibers also include thermoplastic fibers combined with dry reinforcing continuous fibers to provide an extrudable hybrid or commingle form, and / or include an uncured thermoset resin to provide an extrudable prepreg form, in which case the first flexural modulus, as discussed above, will also be zero or near zero because the matrix material is not solidified.

[0048] In one embodiment, the first continuous fibers collectively form at least one first fiber bundle having a circular or substantially circular cross section, while in other embodiments they are assembled into at least one first fiber tape having a collectively rectangular or substantially rectangular cross section with a base significantly wider than its thickness.

[0049] According to one embodiment, the at least one elongated element is arranged in the peripheral region of the at least one first fiber bundle or first fiber tape and / or within the at least one first fiber bundle or first fiber tape at least in the at least two locations.

[0050] In a second aspect, the present invention relates to a method of manufacturing a part formed from a composite material, the part comprising a body and continuous fibers disposed within the body, the method comprising the steps of: a) obtaining a body including one or more tubular cavities therein, each of the one or more tubular cavities extending between a first end disposed on the outer surface of the body and including an inlet opening, and a second end opposite the first end; b) introducing the pushable elongated reinforcing member according to the first aspect of the present invention (of any embodiment) and a liquid matrix material (e.g., a molten thermoplastic resin or an uncured thermosetting resin) into at least one of the one or more tubular cavities through an entrance opening thereof, with the introduction end of the pushable elongated reinforcing member advancing towards a second end of the at least one tubular cavity. c) allowing the liquid matrix material to solidify until solidified and adhered to the body of the component and securing the pushable elongated reinforcing members within the at least one tubular cavity.

[0051] In yet another aspect, the present invention relates to a component comprising the following components: - Body made from a single material or a combination of different materials; - at least one pushable elongate reinforcing member according to the first aspect of the invention (of any embodiment) therein, the elongate reinforcing member extending between a first end located on or near the outer surface of the body and a second end; - a solidified matrix material surrounding said at least one compressible elongated reinforcing member, said matrix material being a different material from at least one of said at least one material of said body, or the same material but with different properties.

[0052] The foregoing and other advantages and features will be better understood from the following detailed description of the embodiments, taken in conjunction with the accompanying drawings, which should be considered in an illustrative and non-limiting manner. [Brief explanation of the drawings]

[0053] [Figure 1] FIG. 1 is a schematic diagram illustrating a cross-sectional side view of a pushable elongated reinforcing member according to a first aspect of the present invention after it has been introduced into a tubular cavity in a body of a component, in one embodiment. [Figure 2]FIG. 2 is a schematic diagram of a pushable elongate strength member according to the first aspect of the present invention in an embodiment in which the joining elements are wound threads. [Figure 3] FIG. 3 is a schematic representation of a pushable elongate strength member according to the first aspect of the present invention in an embodiment in which the joining elements are formed from two threads applied by braiding. [Figure 4A] FIG. 4A is a schematic diagram illustrating a cross-sectional side view of a plurality of pushable elongated reinforcing members according to a first aspect of the present invention after they have been introduced into a tubular cavity in a body of a part in an embodiment in which the bonding elements are uniformly distributed. [Figure 4B] FIG. 4B is a cross-sectional view of the component shown in FIG. 4A, taken along the section line AA. [Figure 5A] FIG. 5A is a schematic diagram illustrating a cross-sectional side view of a plurality of pushable elongated reinforcing members according to a first aspect of the present invention after they have been introduced into a tubular cavity in a body of a part in an embodiment in which the bonding elements are unevenly distributed. [Figure 5B] FIG. 5B is a cross-sectional view of the component shown in FIG. 5A taken along the section line AA. [Figure 6A] FIG. 6A is a schematic illustration of a pushable elongate reinforcing member of the first aspect of the present invention in an embodiment in which the bond between the first group of continuous fibers and the elongate member is made according to Bonding Option 1A. [Figure 6B] FIG. 6B is an enlarged detail view of one of the bond regions in the embodiment of FIG. 6A. [Figure 6C] FIG. 6C is a cross-sectional view of the pushable elongate strength member shown in FIG. 6A, taken along the section line AA. [Figure 7A] FIG. 7A is a schematic diagram of a pushable elongated reinforcing member according to a first aspect of the present invention, showing an embodiment in which the bond between the first group of continuous fibers and the elongated member is made according to bond option 1B. [Figure 7B] FIG. 7B is an enlarged detail view of one of the bond regions in the embodiment of FIG. 7A. [Figure 7C] FIG. 7C is a cross-sectional view of the pushable elongate strength member shown in FIG. 7A, taken along the section line AA. [Figure 8A] FIG. 8A is a schematic representation of a pushable elongate reinforcing member according to the first aspect of the present invention in an embodiment in which the bond between the first group of continuous fibers and the elongate elements is made according to Bonding Option 2. [Figure 8B] FIG. 8B is an enlarged detail view of one of the bond regions in the embodiment of FIG. 8A. [Figure 8C] FIG. 8C is a cross-sectional view of the pushable elongate strength member shown in FIG. 8A, taken along the section line AA. [Figure 9A] FIG. 9A is a schematic illustration of a pushable elongate reinforcing member according to the first aspect of the present invention in an embodiment in which the bond between the first group of continuous fibers and the elongate elements is made according to Bonding Option 3. [Figure 9B] FIG. 9B is an enlarged detail view of one of the bond regions in the embodiment of FIG. 9A. [Figure 9C] FIG. 9C is a cross-sectional view of the pushable elongate strength member shown in FIG. 9A, taken along the section line AA. [Figure 10A] FIG. 10A is a schematic representation of a pushable elongate strength member according to a first aspect of the present invention in some embodiments in which the first group of continuous fibers forms a tape. [Figure 10B] FIG. 10B is a cross-sectional view of the compressible elongate reinforcement member shown in FIG. 10A, taken along section line AA, for an embodiment in which the elongate elements are solidified layers. [Figure 10C] FIG. 10C is a cross-sectional view of the pushable elongate reinforcement member shown in FIG. 10A, taken along the section line AA, in an embodiment in which the elongate elements are solidified rods. [Figure 11A] FIG. 11A is a schematic illustration of a pushable elongate reinforcing member of the first aspect of the present invention in an embodiment in which the bond between the first group of continuous fibers and the elongate member is made according to bond option 1C. [Figure 11B]FIG. 11B is an enlarged detail view of one of the bond regions in the embodiment of FIG. 11A. [Figure 11C] FIG. 11C is a cross-sectional view of the pushable elongate strength member shown in FIG. 11A, taken along the section line AA. [Figure 12A] FIG. 12A is a schematic cross-sectional view of a body of a part having a tubular cavity defined therein, used to manufacture the part by the method of the second aspect of the present invention, in one embodiment. [Figure 12B] FIG. 12B is a schematic view of the body of the component of FIG. 12A with an introducer connected to one introducing end of the tubular cavity thereof. [Figure 12C] Figure 12C shows the same components as Figure 12B, but shows a state in which a pushable elongated reinforcing member of the first aspect of the present invention has been introduced into the tubular cavity by an introducer connected thereto, according to an embodiment of the method of the second aspect of the present invention. [Figure 12D] Figure 12D is a schematic illustration of the final composite part after two pushable elongated reinforcing members of the first aspect of the present invention have been introduced into the two illustrated tubular cavities together with a liquid matrix material (not shown), the elongated members have been cut at the entrance to the tubular cavities, and the introducers have been separated, according to one embodiment of the method of the second aspect of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0054] As shown, according to various embodiments in the accompanying figures, a first aspect of the present invention relates to a pushable elongated reinforcing member R. The elongated member R includes a plurality of continuous fibers forming a first group F having a first flexural modulus, and one or more elongated elements E having a second flexural modulus greater than the first flexural modulus. The one or more elongated elements E are bonded to the first group of continuous fibers F at two or more locations L along their length to transfer a push-compression force longitudinally from the elongated elements E to the first group of continuous fibers F.

[0055] For example, as shown in Figure 1, the pushable elongated reinforcing member R is based on a combination of a first set of fibers F, which are not capable of transmitting compressive loads (usually dry fibers, but can also be prepreg or commingled fibers), and elongated elements E, such as consolidated fibers or composite rods, which are capable of transmitting compressive loads, and which transmit the pushable loads along the fiber bundles that form the pushable elongated reinforcing member R.

[0056] Consolidated fiber or composite rods are typically produced by pultrusion at fiber volume fractions of approximately 60%. Pultrusion is the most cost-effective composite manufacturing technique.

[0057] It has been demonstrated that a good balance between pushability and flexibility can be achieved when the volume fraction of elongated elements in the bundle is in the range of 1.5% to 15%, or 1.5% to 5%, or 3% to 15%. However, even higher volume fractions of elongated elements (in the range of 15% to 75%) can still be a viable solution for a variety of applications involving gentle bending or where high pushability is required.

[0058] When the slender elements are constructed from consolidated fibers, the use of a low volume fraction of slender elements also contributes to: (i) a cost-effective solution, since consolidated fibers are significantly more expensive than, for example, dry fibers, and (ii) a higher total fiber volume fraction within the tubular cavity, since thin fiber filaments (typically 7 microns for carbon fiber) can achieve a much higher compressibility (or reduced interfilament voids) compared to relatively thick composite rods (e.g., 0.5 mm or 1 mm).

[0059] Using a group of thinner rods is more suitable than using a few thicker rods to achieve the same volume fraction of consolidated fibers because of the increased flexibility and the ability to reduce the radius of curvature. Thinner rods also make it easier to cut the bundle after installation into the tubular cavity. It has been demonstrated that a 0.5 mm diameter carbon composite rod can be bent to a radius of curvature of approximately 1.5 cm without breaking, and still fully recover to its original position. This second property is also important because it facilitates the installation process using the CFIP technique described above.

[0060] As an example, a pushable fiber bundle for introducing a 5 mm diameter tubular cavity can be constructed from 11 24k dry carbon fiber tows with a flexural modulus of 0 MPa and three 0.5 mm diameter carbon / epoxy pultruded composite rods with a flexural modulus of 120,000 MPa, resulting in a 5.6% volume fraction of slender elements in the bundle. It can also be constructed from three 0.5 mm diameter epoxy pultruded composite rods with a flexural modulus of 120,000 MPa, resulting in a 5.6% volume fraction of slender elements in the bundle, a 52.4% total fiber volume fraction in the cavity, and a minimum radius of curvature of approximately 1.5 cm.

[0061] According to the CFIP and / or the method of the second aspect of the present invention, a pressing force (action force, indicated by the right-pointing arrow in FIG. 1) applied by the introduction system at the entrance of the tubular cavity T of the body B is transmitted along the fiber bundle via the elongated elements E (solidified fibers). A reaction force is a friction force (indicated by the left-pointing arrow in FIG. 1) that occurs between the fiber bundle and the tubular cavity wall. The fibers that are primarily subjected to this friction force are the peripheral fibers.

[0062] If the elongated elements E, such as the solidified fibers, are not mechanically coupled to the first set of fibers F, such as the dry fibers, especially the peripheral fibers, the elongated elements E will slip relative to the first set of fibers F, hindering the introduction process. Therefore, a third element is required for proper functioning of the fiber bundle. This element must (i) couple the solidified fibers E with the dry fibers F (especially the peripheral fibers) and (ii) be able to transfer loads between them.

[0063] When there are many elongated elements E (e.g. composite rods), it is desirable to place them together, since the shorter the distance between the elongated elements E, the lower the moment of inertia of the bundle and the more flexible it becomes.

[0064] The use of elongated elements E also contributes to significantly reducing or avoiding bending or buckling of the fibers of the first set of fibers F during pressing, which leads to better fiber alignment and improved mechanical properties.

[0065] These bonding elements J also have the function of preventing or inhibiting fraying of the first set of fibers F during the introduction process, which is not only important for process feasibility but also for holding the fibers in place to allow proper handling of the material.

[0066] The coupling elements J may be of various types and / or may be provided in different arrangements depending on the embodiment, for example: - Bonding options 1A, B, C (see below): threads or bundles of threads are sewn, wrapped (see Figure 2), knotted or braided (see Figure 3) onto (option 1A) and / or through (options 1B and 1C) the reinforcing elongate strips R (e.g. bundles or tapes). - Bonding option 2: Matrix material (e.g. cured thermoset, solidified thermoplastic, adhesive or similar). - Combined option 3: A combination of both.

[0067] In bonding option 1B, both the plurality of continuous fibers of the first group F and the elongated element E are sewn, wrapped, knotted, or braided at an internal location Li (e.g., by an internal winding W1) by a bonding element J (e.g., a thread), while in bonding option 1C, only the elongated element E is sewn, wrapped, knotted, or braided at an internal location Li (e.g., by an internal winding W1) by a bonding element J (e.g., a thread).

[0068] In both bonding options 1B and 1C, a bonding element J (eg, a thread) stitches, wraps, knots, or knits (eg, by an external wrap W2) the first group of continuous fibers F at an external location Lo.

[0069] When dry fibers are used in the first group F, the outer surface of the elongated member R needs to be permeable to allow the resin to flow through the dry fibers during the introduction process and to allow proper impregnation of the fiber bundle or fiber tape. This permeability can be achieved by applying the bonding element in such a way that no part of the outer surface is covered by the bonding element.

[0070] Furthermore, the bonding by the bonding element J can be applied in a homogeneous or non-homogeneous manner.

[0071] 4A and 4B show an embodiment of such a uniform bonding, in particular three continuous fiber bundles including both the first group F and the elongated elements E introduced into the tubular cavity T, which are bonded respectively by three threads J uniformly wound around them (i.e. according to bonding option 1A), with a low winding pitch such that two adjacent winding turns are close to each other.

[0072] However, bonding all fiber bundles in a uniform manner presents the following limitations: 1. Significantly reduces the flexibility of the bundle. 2. It crowds the fibers throughout the bundle, making proper impregnation difficult or preventing it, especially in the interior areas. 3. It prevents the fibers from dispersing uniformly within the tubular cavity. 4. Prevents the fibers from adapting to different cross-sectional shapes of the tubular cavity.

[0073] For this reason, it is preferable to bond them in a non-uniform manner. It has been demonstrated that even if fiber bundles (or fiber tapes) are bonded at intervals of 5 to 50 times the diameter or thickness, their flexibility and impregnation properties are not significantly affected, and their pushability can be maintained.

[0074] A low proportion of elongated elements E, such as solidified fiber rods, with small diameters will result in a very low bond area if bonded unevenly. To achieve adequate adhesion to adequately transfer the load from the elongated elements E to the first set of fibers F, the use of additional substances such as activators, primers, adhesion promoters, etc. may be required.

[0075] In the case of non-uniform bonding, the above limitations 3 and 4 also exist, but they are limited to the bonding area, which is only a small portion of the fiber bundle. When multiple fiber bundles are introduced into a tubular cavity, uniform fiber distribution can be achieved if the bonding areas do not coincide.

[0076] 5A and 5B show one embodiment of such a non-uniform bonding. In particular, three continuous fiber bundles, including both a first fiber group F and elongated elements E introduced into a tubular cavity T, are bonded respectively by three threads J wound non-uniformly around them (i.e., according to bonding option 1A). The wrapping has regions Z1 with a very low winding pitch and regions Z2 with a very high winding pitch.

[0077] In the embodiment shown in Figures 5A-5B, the regions of very low winding pitch do not match between bundles, allowing for a more uniform distribution within the tubular cavity, as is evident from the cross-sectional view shown in Figure 5B when compared to Figure 4B.

[0078] In bonding method 1, the yarns J are preferably combined with at least one matrix material, such as a thermosetting resin (prepreg), a thermoplastic fiber (comingle), an adhesive or similar material, or a combination thereof, which, when solidified, bonds to the elongated elements E and to the first group of fibers F.

[0079] 2 and 4A, in a uniform bond, each turn (wrap) corresponds to a bond location L (only a portion of which is shown in the figures for clarity), whereas in the embodiment of FIG. 3, each crossing point of the braided yarn J corresponds to a bond location L.

[0080] However, in embodiments involving non-uniform bonding, i.e., the embodiments shown in Figures 5A-5B, 6A-6C, 7A-7C, and 11A-11C, the bond locations L are actually spaced apart longitudinally (typically spaced apart by 5 to 50 times the diameter or thickness of the pushable elongated reinforcing member R), and in the example of Figures 5A and 5B, for example, each region Z1 having a very low (small) winding pitch corresponds to one of these bond locations L.

[0081] In other words, in the embodiments of Figures 5A-5B, 6A-6C, 7A-7C, and 11A-11C, bonding sites are not considered in the regions Z2 where the winding pitch is very high (large). This is because in these regions, the yarn is not bonded to the matrix material, or is bonded but not consolidated, or the tension in the yarn is too low to ensure effective bonding even if it is bonded and consolidated to the matrix material. This also applies to the intermediate regions between bonding sites L in the embodiments of Figures 9A-9C.

[0082] In the embodiments of Figures 6A-6C, 7A-7C and 11A-11C, each bond point L is formed by a respective group of sub-points (intersections), but all of these sub-points in each group are considered to form a single point L because the relative distance between them is very small (less than the diameter or thickness of the elongated reinforcing member R).

[0083] The thread J may be made of a material specific for this function, such as polyester or aramid fiber, or may be made of the same material as the fiber bundle. The thread J may be made of a rigid or elastic material.

[0084] In one embodiment, the first set of fibers F, the elongated elements E and also the connecting elements are made of the same type of reinforcing fibers, such as carbon fibers, resulting in a "full-carbon pushable and flexible" member. Furthermore, optionally, if the connecting elements J are combined with a matrix, the material of the matrix may be the same as the liquid matrix material used to impregnate the pushable elongated reinforcing members R.

[0085] To achieve a proper mechanical bond, the elongated element E must be in direct contact with the yarn J. This means that if the yarn J is placed on a fiber bundle containing the first group of fibers F, the elongated element E (e.g., a solidifying fiber) should be placed in its surrounding or outer region. This arrangement corresponds to bonding option 1A and is shown in Figures 6A-6C.

[0086] In an implementation of the embodiment of Figures 6A-6C, the pushable elongated strength members R have the following fiber bundle configuration: - Dry fiber F: 11 carbon fiber tows of 24k filaments, flexural modulus 0MPa - Slender element E: Three 0.5 mm carbon / epoxy rods with a fiber volume fraction of 60% and a flexural modulus of 120000 MPa, arranged in the peripheral region of the fiber bundle. - Volume fraction of element E in the bundle: 5.6%. - Bonding element J: 200 denier aramid fiber yarn impregnated with cyanoacrylate adhesive - Application method: Uneven wrapping around the periphery - Low pitch area Z1 or joining point L: - Number of turns: 3 - Pitch: 1mm - High pitch area Z2: - Number of turns: 1 - Pitch: 10cm - Distance between joints L: 10cm - Maximum load per connection point L: >40N

[0087] When a thread J is placed through the fiber bundle, i.e., within the first group of fibers F, an elongated element E may be placed within the bundle, i.e., according to bonding option 1B or 1C. This arrangement (for bonding option 1B) is shown in Figures 7A-7C and includes a bonding element J (e.g., a thread) wrapped around the plurality of continuous fibers and elongated element E of the first group F with an inner winding W1 at an inner location Li, and wrapped around the first group of continuous fibers F with an outer winding W2 at an outer location Lo.

[0088] In an implementation of the embodiment of Figures 7A-7C, the pushable elongated strength members R have the following fiber bundle configuration: - Dry fiber: 11 carbon fiber tows of 24k filaments, flexural modulus 0MPa. - Slender element E: Three 0.5 mm carbon / epoxy rods with a fiber volume fraction of 60% arranged in a fiber bundle, flexural modulus 120000 MPa. - Volume fraction of slender elements E in the bundle: 5.6%. - Bonding element J: 200 denier aramid fiber yarn impregnated with cyanoacrylate adhesive. - Installation method: Inner winding part W1 at inner part Li, peripheral winding part W2 at outer part Lo, uneven. - Low pitch area Z1 or joining point L: - Number of turns: 3 inside, 3 around the periphery - Pitch: 1mm - High pitch area Z2: - Number of turns: 1 on the periphery - Pitch: 10cm - Distance between joints L: 10cm - Maximum load per connection point L: >40N

[0089] 8A-8C show a further embodiment of a pushable elongate reinforcing member R according to the first aspect of the present invention. In this embodiment, bonding is performed according to Bonding Option 2 described above. That is, bonding element J is a matrix material, such as a cured thermoset, hardened thermoplastic, adhesive, or similar material, that is applied to a plurality of bonding locations L, soaking in and impregnating the fiber bundle and defining corresponding bonding areas where a first group of fibers F is bonded to elongate member E. In this example, while elongate member E is positioned at the center of the fiber bundle in the embodiment shown in FIG. 8C, elongate member E could be positioned anywhere, provided that the matrix material fills the entire cross-section of the bundle.

[0090] In an implementation of the embodiment of Figures 8A-8C, the pushable elongated strength members R have the following fiber bundle configuration: - Dry fiber: 27 carbon fiber tows of 24k filaments, flexural modulus 0MPa. - Slender element E: One carbon / epoxy rod with a diameter of 0.8 mm and a fiber volume fraction of 60% arranged within a fiber bundle, with a flexural modulus of 120,000 MPa. - Volume fraction of slender elements E in the bundle: 2.0%. - Bonding element J: 200 denier aramid fiber yarn impregnated with cyanoacrylate adhesive. - Application method: inner winding W1 and peripheral winding W2, uneven. - Low pitch area Z1 or joining point L: - Number of turns: 3 inside, 3 around the periphery - Pitch: 1mm - High pitch area Z2: - Number of turns: 1 on the periphery - Pitch: 10cm - Distance between joints L: 10cm - Maximum load per connection point L: >40N

[0091] 9A-9C show a further embodiment of a pushable elongated reinforcing member R according to the first aspect of the present invention. In this embodiment, the bonding is performed according to Bonding Option 3 described above, i.e., two types of bonding elements J combined, a yarn wrapped around a plurality of bonding locations L, and a matrix material, such as a cured thermoset, solidified thermoplastic, adhesive, or similar material, that is applied to the plurality of bonding locations L and soaks into and impregnates the wrapped yarn and fiber bundle, forming corresponding bonding areas where a first group of fibers F is bonded to the elongated elements E. In this example, while the embodiment shown in FIG. 9C has the elongated elements E positioned at the center of the fiber bundle, the elongated elements E could be positioned anywhere, provided the matrix material fills the entire cross-section of the bundle.

[0092] 1 through 9A-9C, the elongated reinforcing members R formed one or more fiber bundles, ie, bundles having a substantially circular cross section.

[0093] However, in the case of tubular cavities having a flat cross section, i.e., where the width of the tubular cavity is significantly greater than the height, the use of elongated reinforcing members R in the form of tapes may be more efficient than the use of fiber bundles.

[0094] The tape may be composed of various layers of unidirectional fabric, woven or multiaxial fabric, or a combination thereof. The elongated elements that enable the tape's compressibility may be one of these layers or composite rods positioned longitudinally within and / or on the surface of the tape.

[0095] The tape cross section does not necessarily have to be rectangular, but may have a particular shape (or preform) to fit within a tubular cavity having a non-rectangular or arbitrary cross-sectional shape. While bonding of the fibers can be achieved by any of the three bonding options described above, in this example, stitching is the preferred method because wrapping, braiding, or tying the threads tends to circularize the cross section in the bonded area.

[0096] Two such tape format embodiments are shown in Figures 10A, 10B and 10C.

[0097] In the embodiment of FIG. 10B, the elongated elements E are specifically centrally located solidified layers E, but they can also be located in other positions, such as at the top or bottom of the tape.

[0098] In the embodiment of FIG. 10C, there are a plurality of elongated elements E in the form of solidified rods E.

[0099] In both embodiments, the joining element J is a stitched thread, as best seen in Figures 10B and 10C.

[0100] 11A-11D show a further embodiment of the pushable elongated reinforcing member R of the first aspect of the invention. In this embodiment, the bonding is performed according to option 1C. The elongated element E is wound at an internal location Li, in particular with an internal winding W1, while the first continuous fiber group F is wound at an external location Lo, in particular with an external winding W2. The internal winding W1 and the external winding W2 are connected to each other because they are part of the same connecting element J (e.g., a thread).

[0101] Finally, Figures 12A-12D are provided to illustrate the sequence of various stages in the manufacture of a part according to the method of the second aspect of the present invention, in one embodiment.

[0102] In particular, Figure 12A shows a body B obtained according to step a) of the above method, having a tubular cavity T defined therein. Figure 12B shows said body B with an introducer In coupled to the introducing end of one of its tubular cavities T. Figure 12C shows a pushable elongate reinforcement member R according to the first aspect of the invention, already introduced into the tubular cavity T by an introducer In coupled according to part of step b) of the above method.

[0103] The liquid matrix material introduced and solidified in steps b) and c), respectively, is not shown, but is carried out by the method of the second aspect of the invention to produce the composite part P shown in Figure 12D for the same embodiment as Figures 12A-12C.

[0104] Those skilled in the art may make changes and modifications to the above-described embodiments without departing from the scope of the invention as defined in the appended claims.

Claims

1. A pushable elongated reinforcing member (R) comprising a plurality of continuous fibers, the plurality of continuous fibers are or include non-solidified fibers, forming a first group of continuous fibers (F) having a first flexural modulus; the compressible elongated reinforcing member (R) further comprises at least one elongated element (E) having a second flexural modulus greater than the first flexural modulus; The at least one elongated element (E) is coupled to the first group of continuous fibers (F) and transmits a longitudinal compressive force from the at least one elongated element (E) to the first group of continuous fibers (F).

2. 2. The pushable elongated reinforcing member (R) of claim 1, wherein the elongated elements (E) are bonded to the first group of continuous fibers (F) at at least two locations (L) along their length.

3. 3. A pushable elongated reinforcing member (R) according to claim 1 or 2, wherein said second flexural modulus is at least 10 times greater than said first flexural modulus.

4. 4. A pushable elongated reinforcing member (R) according to claim 1, 2 or 3, wherein said first flexural modulus is less than 10,000 MPa and said second flexural modulus is greater than or equal to 10,000 MPa.

5. 5. A pushable elongated reinforcing member (R) according to any one of claims 1 to 4, wherein said at least one elongated element (E) is formed by a second group of continuous fibres.

6. 6. A pushable elongated reinforcing member (R) according to any one of claims 1 to 5, wherein the non-solidifying fibres are dry reinforcing continuous fibres.

7. 7. The pushable elongated reinforcing member (R) of claim 6, wherein the first group of continuous fibers (F) comprises thermoplastic fibers and / or uncured thermosetting resin in combination with the dry reinforcing continuous fibers.

8. A pushable elongated reinforcing member (R) according to claim 5 or claim 6 or 7 depending on claim 5, wherein the second group of continuous fibers is or comprises continuous fibers bonded and consolidated with a thermoplastic or thermosetting matrix.

9. 9. A pushable elongated reinforcing member (R) according to any one of the preceding claims, wherein the first group of continuous fibers (F) forms at least one first fiber bundle.

10. 9. A pushable elongated reinforcing member (R) according to any one of the preceding claims, wherein the first group of continuous fibers (F) is assembled into at least one first fiber tape.

11. A pushable elongated reinforcing member (R) according to claim 9 or 10, dependent on claim 2, wherein the at least one elongated element (E) is arranged in at least the at least two locations (L) in the peripheral region of the at least one first fiber bundle or first fiber tape and / or within the at least one first fiber bundle or first fiber tape.

12. The pushable elongated reinforcing member (R) according to claim 2 or any of claims 3 to 11 dependent on claim 2, wherein the pushable elongated reinforcing member (R) comprises at least one bonding element (J) to provide mutual bonding between the first continuous fiber group (F) and the at least one elongated element (E) and to enable a liquid matrix flowing through the at least one bonding element (J) and / or through areas of the first continuous fiber group (F) not covered by the at least one bonding element (J) to impregnate the first continuous fiber group (F).

13. 13. The pushable elongated reinforcing member (R) of claim 12, wherein the at least one bonding element (J) bonds the first group of continuous fibers (F) and the at least one elongated element (E) to each other by weaving, wrapping, tying, or sewing at least one thread at the at least two locations (L) and / or by applying an adhesive or bonding matrix material to the at least two locations (L).

14. 14. The pushable elongated reinforcing member (R) of claim 13, wherein the at least two locations (L) are spaced apart by a distance between 5 and 50 times the diameter or thickness of the pushable elongated reinforcing member (R).

15. A method for manufacturing a part (P) from a composite material, the part (P) comprising a body (B) and continuous fibers disposed within the body (B), The manufacturing method includes: a) obtaining a body (B) comprising one or more tubular cavities (T) therein, each tubular cavity (T) extending between a first end including an inlet opening disposed on an outer surface of the body (B) and a second end; b) introducing a reinforcing member (R) and a liquid matrix material into at least one of said one or more tubular cavities (T) through an inlet opening thereof, with an inlet end of said reinforcing member (R) advancing towards said second end of said at least one tubular cavity (T); c) solidifying said matrix material within said at least one tubular cavity (T) until solidified and attached to the body of said part and fixing said pushable elongated reinforcing members (R); Including, the pushable elongated reinforcing member (R) comprises a plurality of continuous fibers forming a first set of continuous fibers (F) having a first flexural modulus; the compressible elongated reinforcing member (R) further comprises at least one elongated element (E) having a second flexural modulus greater than the first flexural modulus; The method, wherein the at least one elongated element (E) is connected to the first group of continuous fibers (F) and transmits a compressive force from the at least one elongated element (E) to the first group of continuous fibers (F) in the longitudinal direction thereof.

16. 16. A method for manufacturing a part (P) from a composite material according to claim 15, wherein the pushable elongated reinforcing members (R) are determined according to any one of claims 1 to 14.

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