EP0659922B1 - Textile reinforcing layer useful in the manufacture of composite materials - Google Patents

Abstract

Textile reinforcement usable for the production of a composite material, consisting, when it is considered in place inside the said composite material after production, of two actual textile reinforcing layers placed on either side of a central layer endowing the said material with thickness, the said central layer consisting of a sheet based on synthetic fibres, of high unit titre, and which have received, before being converted into sheets, a treatment giving them a permanent waviness (or curl). It is characterised in that at least one of the textile reinforcing layers is covered with a fibrous web based on chemical fibres, of lower titre than that of the fibres forming the inner layer and which have also received a treatment giving them a permanent waviness or curl, the various layers being bonded together by needling.

Description

The invention relates to an improvement made to the textile reinforcements used for the production of composite materials, that is to say articles based on resin (polyester or other) reinforced with a textile reinforcement ply.

To date, depending on the applications and the desired characteristics, the reinforcing structures used in the field of composites, are for example fabrics, textile grids, nonwovens or a combination of such elements.

In its French patent 2,646,442, the Applicant proposed a textile reinforcement which is particularly suitable for producing thick reinforcements, a characteristic necessary when it is desired to produce elements such as vehicle bodywork, pleasure boats, tanks, etc., which must have great rigidity. Such a frame is constituted by at least two layers of textile reinforcement proper, arranged on either side of a central layer giving the thickness to said material, and it is characterized in that said central layer consists of a ply based on synthetic fibers, with a high unitary titer, and which have received a treatment prior to their tablecloths form giving them an undulation with permanent crimps, the different layers being linked together by sewing / knitting.

Such a complex is entirely satisfactory with regard to the mechanical characteristics which the composite structure which it makes it possible to exhibit.

Furthermore, it is particularly suitable for producing structures of complex shape obtained by molding, for example according to the techniques known as "press molding with injection" or "vacuum molding". One of the drawbacks it has, however, is that the seams connecting the different layers together, however, limit the deformation capacities and above all, lead to surface appearance defects.

Now we have found, and this is what is the subject of the present invention, an improvement to such a type of textile material which not only makes it possible to conserve the advantages which such a structure has, namely the possibility of deformation, high thickness and above all very high homogeneity of the composite material obtained, resulting from the fact that thanks to the particular structure of the internal fibrous web (fibers having a spring effect), a very homogeneous distribution of the resin is obtained over the entire thickness and all directions of said material and a perfectly regular surface appearance.

In general, the invention therefore relates to a new type of textile reinforcement which can be used for the production of a composite material, this reinforcement being constituted if it is considered in place inside said composite material after production, by two textile reinforcement layers proper, arranged on either side of a central layer giving the thickness to said material, said central layer being constituted by a sheet based on synthetic fibers, of high unit strength, and which have previously received when they are placed in the form of a sheet, a treatment communicating to them a permanent undulation (or crimp), and it is characterized in that at least one of the textile reinforcement layers is covered with a fibrous veil based on chemical fibers, lower than that of the fibers constituting the internal layer and which have also received a treatment imparting to them a permanent waving or crimping, the different layers hes being linked together by needling.

In an embodiment according to the invention, said textile reinforcement consists of a central layer trapped between two textile reinforcements, at least one of which is covered with a fibrous web.

According to a variant, the reinforcement consists of a layer based on fibers of high unitary strength, intended to give thickness to the final material, covered on one of its faces with a textile reinforcement itself covered with a fibrous web, said material being, during the production of the composite structure, folded back on itself so that there is, in the final structure, a central layer giving the thickness on either side of which is arranged a textile reinforcement associated with a fibrous web.

Compared to the reinforcements as described in patent 2,646,442, such a material has improved deformation and molding possibilities given the absence of seams to link the different layers together, retains the same characteristics of good distribution. resin and above all, allows to obtain articles whose exterior surface condition is perfectly regular.

As the material used in the production of such a complex, materials similar to those which are the subject of patent FR-A-2 646 442 can be used to produce the internal layer as well as the two textile reinforcement layers arranged on either side. on the other side of this central layer.

Thus, the internal layer will preferably be produced from a nonwoven web, obtained for example by carding, based on synthetic fibers such as polyester, polypropylene, polyamide, polyethylene fibers having a high titer and which have received a treatment. texturing, for example by stuffing, giving them a permanent crimp. By high titer is meant fibers whose titer is generally between 20 and 200 dtex and whose cutting length is generally between 40 and 120 mm. It is obvious that the use of finer fibers can possibly be envisaged, but then the density of the structure is increased, thus disturbing the path of the resin during the production of the composite material and making the manufacture of the latter more difficult, if not impossible. .

As textile reinforcements proper disposed on either side of the aforementioned internal layer, use will be made of all types of conventional reinforcements such as contiguous or spaced parallel yarns, bidirectional plies, fibrous plies, fabrics which can be used alone or in combination combination. Such reinforcements can be based on any material normally used to make composite articles, such as for example glass fibers.

The fibrous web which covers at least one of the textile reinforcement layers, can be produced from chemical fibers, of the same nature or of a different nature from that constituting the internal layer, said fibers having also received treatment communicating them a crimp and being much finer. As an indication, polyester, polyamide, polypropylene, polyethylene fibers having a titer between 1.5 dtex and 10 dtex and which are normally used for conventional textile applications, such as clothing, furnishing, filtration, etc., are perfectly suitable for make this or these surface layers.

The connection of the different layers to each other is advantageously carried out by mechanical needling, using needles having barbs oriented in opposition and making it possible to obtain the entrainment of the surface fibers as well as on the way in and out of said needles through the stack of fibrous layers constituting the complex.

In the case where the basic structure making it possible to produce a material in accordance with the invention consists only of a fibrous sheet of high titer, one side of which is covered with a textile reinforcement itself covered with a fibrous web based on fine and crimped fibers, needling can be carried out with needles which have barbs oriented in the same direction and which penetrate into the stack of textile materials from the surface layer based on fine fibers.

Optionally, it could be envisaged to make the connection of the different layers together by using a needling treatment by means of jets of fluid, and more particularly of water jets.

The invention and the advantages which it brings will however be better understood thanks to the embodiment given below for information but not limitation.

Example

• d'une couche interne constituée par une nappe non tissée réalisée par cardage, à partir de fibres de polypropylène ayant un titre unitaire de 70 dtex et une longueur de coupe de 90 mm, les fibres ayant été préalablement frisées avant coupe de manière à présenter des ondulations permanentes (dans le cas présent, 2,3 ondulations/centimètre) ; cette nappe pèse environ 250 g/m2 et a une épaisseur d'environ 4 mm ;
• de deux nappes de renfort textile proprement dites disposées de part et d'autre de la couche interne précitée, ces nappes de renfort textile étant constituées toutes les deux par un mat de verre pesant 450 g/m2, obtenu par découpe de fibres de verre et nappage conventionnel par voie sèche ; ces fibres de verre ont un titre de 25 tex, la longueur de coupe étant de 50 mm.

On a conventional needling machine, equipped with needles having barbs oriented in opposition, a frame is produced in accordance with the invention by introducing into said needling machine a superposition of textile plies previously produced, and which consists of:

• an internal layer consisting of a nonwoven web produced by carding, from polypropylene fibers having a unit titer of 70 dtex and a cutting length of 90 mm, the fibers having been crimped before cutting so as to present permanent waves (in this case, 2.3 waves / centimeter); this sheet weighs approximately 250 g / m2 and has a thickness of approximately 4 mm;
• two textile reinforcement plies proper disposed on either side of the aforementioned internal layer, these textile reinforcement plies both being constituted by a glass mat weighing 450 g / m2, obtained by cutting glass fibers and conventional dry topping; these glass fibers have a titer of 25 tex, the cutting length being 50 mm.

On either side of the above-mentioned assembly, against the two external faces of the textile reinforcement layers, a fibrous web is also arranged, made by carding from crimped polyester fibers having a count of 3.3 dtex and a length 40 mm cutting; this fibrous sheet weighs 60 g / m2.

• vitesse de passage de la matière : 4 mètres/minute
• amplitude de déplacement des aiguilles : 60 mm
• densité d'aiguilletage : 45/50 coups par cm2.

The needling operation is carried out under the following conditions:

• material passing speed: 4 meters / minute
• displacement of the needles: 60 mm
• needling density: 45/50 strokes per cm2.

After needling, a structure is obtained having a thickness of approximately 4.5 mm, the various plies being perfectly bonded to each other.

Example 2 :

Example 1 is repeated except that the stack of textile plies consists only of an internal layer covered with a textile reinforcing ply and a fibrous web having the same characteristics and the same composition. than the materials of Example 1.

Needling is carried out under the same conditions except that the needles have barbs oriented in the same direction and that their action on the stack of textile webs is exerted from the fibrous web of fine fibers.

During use, the structure obtained is folded back on itself so that the fibrous webs are on the outside and the nonwoven based on high titer fibers is on the inside. In the preceding example, for example, a reinforcement having a thickness of approximately 9 mm is obtained.

The materials according to the invention are perfectly suited for making articles molded by press with injection or by vacuum molding. The composite articles thus produced are very homogeneous, and moreover have a perfectly regular surface appearance.

Of course, the invention is not limited to the embodiment described above, but it covers all the variants produced in the same spirit.

Thus, the connection of the different layers could possibly be carried out by performing double-sided needling or by means of an installation using water jets.

Similarly, if it is advantageous to make the connection of all the layers constituting the material according to the invention in a single operation, it could be envisaged to attach the two external faces after having produced the internal structure (central layer and reinforcement associated with this layer) beforehand.

Claims (5)

1. Textile reinforcement which can be used for the manufacture of a composite material, consisting, considering the situation inside the said composite material after manufacture, of two reinforcing textile layers proper which are arranged on either side of a central layer giving thickness to the said material, the said central layer consisting of a web based on man-made fibres which have a high individual linear density and, prior to them being formed into webs, have received a treatment giving them a permanent undulation (or crimp), characterized in that at least one of the reinforcing textile layers is covered with a fibrous lap based on chemical fibres having a linear density less than that of the fibres forming the internal layer and having also received a treatment giving them a permanent undulation or crimp, the various layers being bonded together by needle punching.
2. Reinforcement according to Claim 1, characterized in that it consists, before manufacture of the composite material, of a central layer trapped between two reinforcing textiles, at least one of which is covered with a fibrous lap.
3. Reinforcement according to Claim 1, characterized in that it consists, before manutacture of the composite material, of a layer based on fibres having a high individual linear density, this layer being intended to give thickness to the final material, covered on just one of its faces with a reinforcing textile which is itself covered with a fibrous lap, the said material, during the manufacture of the composite structure, being folded on itself so that, in the final structure, there is again a central thickness-giving layer on either side of which is arranged a reinforcing textile associated with a fibrous lap.
4. Reinforcement according to one of Claims 1 to 3, characterized in that the layer or layers of reinforcing textile consist of fibrous mats possibly associated with other reinforcing textiles.
5. Reinforcement according to one of Claims 1 to 4, characterized in that the layer giving thickness to the material and the fibrous lap or laps forming the external face or faces are based on polyester, polyamide, polypropylene or polyethylene fibres, reinforcing elements interposed between these layers being based on glass fibres.