FR2989695A1 - TEXTILE REINFORCEMENT COMPLEX FOR COMPOSITE COMPONENTS AND METHOD OF MANUFACTURE - Google Patents

Abstract

Reinforcing textile complex for composite parts, comprising at least one layer of high tenacity yarn arranged in parallel, characterized in that it comprises at least one layer of synthetic yarn, which may or may not be perforated, in contact with the layer of yarns of high tenacity, said synthetic son being arranged parallel and rectilinear, without mechanical connection between them.

Description

TECHNICAL FIELD The invention relates to the field of technical textiles, and more particularly to textiles intended to serve as strengthening reinforcement for composite parts. BACKGROUND OF THE INVENTION It more specifically targets high performance complexes, that is to say integrating high tenacity yarns such as glass, carbon or the like. It relates more particularly to arrangements for increasing the resistance of the composite parts obtained from this reinforcement, to compression phenomena after impact.

PRIOR ART In general, in the field of composite parts, it is known to use reinforcement textile reinforcements which are formed of a textile complex comprising one or more layers. These layers have yarns oriented in the directions for which it is desired to enhance the mechanical properties of the composite part. In general, when it is desired to have an isotropic or quasi-isotropic reinforcement, complexes are used which comprise several reinforcement layers with different individual orientations. The layers of this multiaxial complex are generally assembled by stitching or the like. Among the properties required for such complexes, there is the post-impact compressive strength of the composite part, which is measured after the complex has been impregnated with the resin blocking the high tenacity yarns. To improve this compressive strength after impact, it is known to interpose between the different layers of high-tenacity yarns, veils of synthetic fibers -2- which deform during the impacts exerted on the composite part. The choice of this veil of synthetic fibers is essential to maintain satisfactory properties at the level of the composite part.

It is conceivable that a high density and / or a thick thickness of the web interposed between the reinforcing layers makes it possible to increase the compressive strength after impact, since the energy received during an impact dissipates inside the reinforcement layers. the material of the veil.

Conversely, this web must be as permeable as possible, so as not to oppose the creep of the resin, and in particular must not interfere with the passage of the resin from one layer to the other of the reinforcement. This factor, just like the weight of the veil pushes the contrary to the choice of a veil the finest and the lightest possible. The choice of a fine veil also results in a reduction of the risks of delamination between layers. The reduction in the thickness or the weight of the web inevitably leads to difficulties in handling the veil, as well as manufacturing problems, since it is conceivable that it is difficult to manufacture a veil so the density is very low. since this makes it necessary to use filaments of very low titre, or to have filament junctions which are too few in number. There is therefore a need to replace the existing sails with layers whose density is lower than that observed with the sails used to date.

SUMMARY OF THE INVENTION The invention therefore relates to a reinforcing textile complex for composite parts, comprising at least one layer of high-tenacity yarns formed of a sheet of parallel threads in a rectilinear configuration without being embossed. the invention, this complex is characterized in that it comprises at least one layer of synthetic son in contact with the high tenacity son layer. These synthetic son are arranged parallel and rectilinear without mechanical connection between them.

In other words, the invention consists in replacing the existing sails with layers formed of layers of yarns deposited on the layer of high-tenacity yarns, which are in a configuration known by the abbreviation NCF for "Non Crimped Fabrics", in which the high tenacity yarns are arranged without undulation in their longitudinal direction. In other words, the layers of high tenacity yarns are covered with a set of parallel yarns whose spacing and properties can be chosen to give a performance considerably greater than those observed with two-dimensional webs, in particular in terms of density. Moreover, the use of the web of synthetic threads can be applied in combination with one or more layers of reinforcement son. In the case of a single reinforcing layer, the layer of synthetic threads is found on the surface of the complex. The invention can also be applied to complexes comprising several layers of high tenacity son superimposed between which are interposed one or more layers of synthetic son. In this case, it may be advantageous that the orientations of the layers of the high-tenacity yarns are different from one layer to another, so as to form a multiaxial reinforcement. In practice, the synthetic yarns may be selected from the group consisting of polyester, polyamide, phenoxy, polypropylene, polyethylene yarns, alone or in combination. It may also be multi-component yarns made of several materials, for example with respect to the core and the sheath of the yarns. In practice, the layer of synthetic yarns may have a surface mass of between 0.5 and 20 g / m 2, that is to say a density much lower than that which can be obtained with fiber webs. with equivalent economic conditions. In practice, these synthetic threads may be based on a hot-melt material, which may be subjected to a calendering operation or more generally to heating associated with the application of a pressure, which makes it possible to produce reinforcement complexes free from yarns. binding or sewing. According to different variants, it is possible to use the synthetic yarns which are textured yarns, making it possible to give a certain thickness to the layer interposed between the reinforcing layers, because of the swelling of the yarns used as well as a certain capacity to deform. It is also possible to use synthetic fibers consisting of monofilaments, which because of the incompressibility of these monofilaments, can form spaces within which the resin can more easily flow during its infusion or injection. In practice, it is possible to use several layers of synthetic threads directly superimposed with son orientations different from one layer to another. Such a combination makes it possible to improve the thickness interposed between reinforcement layers, and plays favorably with regard to the creep of the resin. It is also possible in this way to combine layers of synthetic yarns of different nature. The use of several layers of superimposed synthetic yarns also makes it possible to reduce the density of synthetic yarns of each of the layers, while retaining satisfactory overall properties, and in particular good adhesion when using synthetic hot melt yarns L the invention also relates to a process for manufacturing a textile composite reinforcement complex, in which: at least one layer of high tenacity yarns is deposited in parallel, and preferably in a rectilinear configuration without embossing; One layer of synthetic yarns is deposited in contact with one of these layers of high-tenacity yarns, these synthetic yarns being deposited in the form of a sheet of parallel yarns. Preferably, the synthetic yarns are deposited in an orientation forming a non-zero angle with the orientation of the yarns of the high tenacity layer on which these yarns are deposited. In one particular embodiment, the high-tenacity layer and the synthetic layer can be subjected to a step of exposure to a source of heat and application of pressure, such as, for example by calendering, to obtain a complex without strands of binding or sewing. BRIEF DESCRIPTION OF THE FIGURES The manner of carrying out the invention, as well as the advantages which result therefrom, will emerge clearly from the description of the embodiments which follow, in support of the appended figures in which: FIGS. 1 to 4 are brief perspective views of textile complexes according to four different embodiments, wherein some of the layers have been partially removed to reveal the underlying layers; FIG. 5 is a schematic summary perspective view of a machine for carrying out the invention. Of course, the dimensions and the proportions of the various elements constituting the complex of the invention are given as an indication in order to make it possible to understand the invention, to differ from reality. Embodiment of the invention As already mentioned, the invention can be realized in various ways, while respecting the general principle of setting up a layer of parallel synthetic threads, coming into contact with a layer of reinforcement. Thus, as illustrated in FIG. 1, the reinforcement 1 comprises a first layer 2 made from carbon threads, having a number of filaments from 12K to 50K, having undergone a spreading operation such as a unitary yarn ( 3) has a width of the order of a few millimeters to a few hundred millimeters. The used carbon wires may have different levels of toughness, having higher or lower Young's moduli, depending on the applications. These wires 20 (3) are arranged in parallel and in a contiguous manner without having any encapsulation, that is to say without undulations around the main plane of the layer (2). This sheet of carbon son has an overall surface area of the order of a few tens to a few hundred g / m 2, typically from 30 g / m 2 to 300 g / m 2. Complementarily, this reinforcing layer (2) receives an additional layer (4) formed by a sheet of parallel synthetic threads (5). The nature, density and angle made by these wires can vary depending on the application. Thus, it is possible to space at will these son, so as to form a perforated layer and even lighter. In the example illustrated in FIG. 1, the wires (5) form an angle α of 45 ° with respect to the axis (6) corresponding to the direction of the wires (3) of the reinforcing layer (2). ), but this angle can of course vary depending on the applications.

It is thus possible to provide that the son (5) are arranged perpendicular to the son (3) chain (2) with an angle of 90 °. It should be noted that this angle, combined with the number of threads per unit length, makes it possible to adjust the density of the sheet (4), which it is advantageous to reduce, as far as possible, so as not to modify the permeability of the complex (1) vis-a-vis the resin. However, it will seek to deposit a sufficient amount of son so that the post-impact compressive strength is sufficient. By way of example, it is possible to use polyester and polyamide or phenoxy yarns which have a titer of between 11 and 167 dtex which are deposited by a framer in a proportion of 2 to 10 threads per cm, making it possible to obtain densities for the sheet (4) of the order of a few g / m2. The choice of fiber material (5) is essentially determined by the chemical nature of the resin that will impregnate the reinforcing threads. In the particular example of FIG. 1, the complex is reduced in terms of reinforcement to a single layer of parallel threads and the sheet of threads (4) can advantageously be used as a means of joining the reinforcement threads to each other, and to overcome conventional means such as an additional sewing thread. In this case, the assembly illustrated in FIG. 1 will be subjected to a calendering operation by which the material of the wires (5) is raised to a temperature above its softening temperature. The application of a pressure makes it possible to penetrate part of these threads (5) on the surface of the reinforcing threads and thus ensuring the relative locking. Of course, it is also possible to secure the web of synthetic yarns (4) to the reinforcing yarn layer (2) by conventional means, in particular by a conventional sewing or knitting mechanism. In the example illustrated in FIG. 2, the reinforcement (21) comprises, just like that of FIG. 1, a reinforcing layer (22) composed of parallel threads (23), as well as a layer of synthetic thread. (24). This complex 21 also comprises an additional layer (32) reconstituted reinforcement son (33), arranged in an orientation different from that of the web (22). Of course, the relative directions of the two plies of reinforcing yarns (22) (32) may vary depending on the applications, and range from a few degrees to 90 °, as illustrated in the figure. Similarly, the nature of the son of the two reinforcing layers may be different, depending on the properties that are desired. These two reinforcing layers (22) (32) can thus have similar properties in terms of yarns and density. They can also be different by using son of different natures, or of different densities. It is also conceivable that the stack as illustrated in Figure 2 can be declined by increasing the number of layers, and providing as many layers of reinforcement son as necessary, each separated by a layer of synthetic son. Thus, as illustrated in Figure 3, the reinforcing complex (51) comprises a layer (52) of reinforcing son on which rests a layer (54) of synthetic son. On top, a layer of reinforcing threads (62) in a different orientation than the threads of the layers (52) is deposited. This layer (62) receives a layer (64) of synthetic threads on which another layer of reinforcing threads (72) is deposited, with a third orientation different from that of the underlying reinforcing son layers (62) ( 52). Of course, the choice of the number of layers and their orientation can be very wide depending on the applications. In the variant illustrated in FIG. 4, the reinforcing layer (82) receives two plies of synthetic threads (84) (87) which are in direct contact with one another. The two plies (84) (87) can be made from yarns of different types to combine several properties. It is thus possible to use a first ply formed of thermofusible threads which will allow the layers to be joined together after calendering, with another ply whose threads have been chosen to improve the compressive strength after impact. Advantageously, the orientations a and (3 of the son of the layers (84) (87) may be different, in this way the mechanical properties of the complex may be similar to those obtained by employing grid structures between the reinforcing layers ( 82) (92) Of course, the invention also covers variants in which the number of layers of synthetic threads is even greater and their number in kind would of course be suitable for applications.

For example, the reinforcements illustrated in Figures 1 to 4 can be made on a machine as shown in Figure 5. Such a machine (100) has several separate positions. Thus, a first input station (101) comprises a creel (102) from which the son (104) are unwound reels or slabs (103) to form the warp son. This station (101) thus delivers the son of one of the reinforcing layers to a conveyor belt (108). At a second station (110), a creel (111) allows the delivery of synthetic son (114) from coils (113). These yarns (114) are passed through a framer (115), which includes a mechanism suitable for depositing a yarn web of a predetermined width across the entire width of the conveyor belt (108). Different technical solutions can be used in an equivalent way, since they make it possible to deposit the synthetic threads (114). It is thus possible to use a framer which uses a mechanism of clamps to allow the deposition of plies of cut son or mechanisms using lugs on the edge of warp son plies to maintain the various synthetic son which then remain continuous. Of course, the wire deposit station (110) can be adapted to adjust the inclination of the synthetic threads (114) with respect to the warp direction. Similarly, the station 110 can be duplicated as many times as it is desired to superpose layers of synthetic son between two reinforcing layers.

In a third station (120) a creel (121) allows the deposition of reinforcing son (124) in a direction different from the direction of advance of the conveyor belt, and in the illustrated form is substantially perpendicular.

Of course, the direction of the reinforcing son (124) can be adjusted depending on the type of reinforcement that is desired to achieve and its multiaxial character. In the illustrated form, only a second layer of reinforcing threads is deposited but it is obvious that the machine can be modified as desired to deposit as many layers of reinforcement and layers of synthetic son as necessary. In the form illustrated in FIG. 5, the machine (100) comprises an assembly station (140), which comprises heating means (141) which can be constituted for example by a heating ramp, making it possible to raise the temperature of all the layers circulating on the conveyor belt, and to soften, in particular, the synthetic son. The calendering station also comprises means for applying a pressure and in particular pressure rollers (142) (143) which can deform the previously heated synthetic son. It is obvious that the heating means can be integrated with the pressure rollers (142) (143).

In a variant, not shown, the calendering station (140) can be replaced by a traditional sewing station, with if necessary a modification of the stack of layers to take into account the type of seam. More particularly, in this case, the son in the warp or 0 ° direction are introduced last station, before sewing. It follows from the foregoing that the reinforcing complex according to the invention has many advantages, in particular that of allowing an improvement in the compressive strength after impact with a very small amount of synthetic material, to be compared. with existing solutions using fiber sails. It also eliminates in some cases a sewing thread that can be detrimental in some applications

Claims (1)

CLAIMS1 / Reinforcing textile complex (1) for composite parts, comprising at least one layer (2) of high-tenacity yarns formed of a sheet of parallel yarns (3) in a rectilinear configuration without being embossed, characterized in that it comprises at least one layer (4) of synthetic threads (5), in contact with the layer (2) of high tenacity yarns, said synthetic threads (5) being arranged parallel and rectilinear, without mechanical connection between them. 2 / Complex according to claim 1 characterized in that the orientation of the son (5) of the synthetic layer forms a non-zero angle (a) with the orientation of the son (3) of the layer (2) son of high tenacity in contact with which synthetic threads come. 3 / A complex according to claim 1 characterized in that the high tenacity yarns are selected from the group consisting of carbon yarns, glass yarns, basalt yarns, aramid yarns, fiber yarns and in particular of flax, singly or in combination. 4 / Complex according to claim 1 characterized in that the layer of synthetic son is composed of son of different nature. 5 / complex according to claim 1 characterized in that the layer of high tenacity son has a density of between 30 g / m2 and 600 g / m2. 6. A complex according to claim 1 characterized in that it comprises several layers (22,32) of superheavy son of high tenacity, between which is interposed at least one layer (24) of synthetic son.-13- 7 / Complex according to claim 1 characterized in that the orientations of the son of the layers (22,32) son of high tenacity are different from one layer to another. 8 / complex according to claim 1 characterized in that the synthetic son are selected from the group consisting of polyester son, polyamide, phenoxy, polypropylene, polyethylene, alone or in combination. 9 / complex according to claim 1 characterized in that the synthetic son layer has a weight per unit area of between 1 and 20 g / m2. 10 / complex according to claim 1 characterized in that the synthetic son are based on a hot melt material. 11 / Complex according to claim 1 characterized in that it is free of binding son or sewing. 12 / complex according to claim 1 characterized in that the synthetic son are textured son. 13. The complex of claim 1 characterized in that the synthetic son are monofilaments. 14 / complex according to claim 1 characterized in that it comprises several layers (84,87) of synthetic son directly superimposed, the orientations of the synthetic son of said layers being different from one layer to another.-14- A method of manufacturing a textile reinforcing complex for composite parts, wherein: at least one layer of high tenacity yarns (103) is deposited in parallel and in a rectilinear configuration without embossing; a layer of synthetic threads (115) is deposited in contact with one of said layers of high-tenacity yarns, said synthetic threads being deposited in the form of sheets of parallel threads. The method of claim 15 wherein the synthetic yarns (115) are deposited in an orientation forming a non-zero angle with the orientation of the yarns (103) of the high tenacity yarn layer on which they are deposited. 17. The method of claim 15 wherein the high-tenacity layer and synthetic wire layer are subjected to a step of exposure to a source of heat and application of pressure.