FR2854172A1 - Reinforcing textile, especially for molded articles, is made from two or more layers of glass fibres with different thicknesses and lengths - Google Patents

Abstract

The reinforcing material comprises >=2 layers of glass fibre mat (2,3) sewn together. The fibres in the second layer (3) are thicker and longer than fibres in first layer (2), and have lower degree of wettability. The fibres in second layer are continuous or >70 cm long. The reinforcing material can have an additional layer (4) in contact with second one, made from thinner, shorter and more wettable fibres. The reinforcing material consists of >=2 layers of glass fibre mat (2, 3) that are sewn together. The fibres in the second layer (3) are thicker (e.g. 70 tex as opposed to 50 tex) and longer than the fibres in the first layer (2), and lave a lower degree of wettability. The fibres in the second layer can be 'continuous' or over 70 cm long, and the reinforcing material can have an additional layer (4) in contact with the second one, made from thinner, shorter and more wettable fibres. At least one outer surface of the reinforcing material can be covered with a layer of synthetic fibres which can be stuck or sewn to the adjacent fibre layer. The material can be made from layers of fibres dropped in sequence onto an endless conveyor belt.

Description

TEXTILE REINFORCEMENT USEFUL FOR THE REALIZATION OF EMPLOYEES REINFORCEMENTS

ESPECIALLY FOR MANUFACTURE

MOLDED ARTICLES.

  Technical field The invention relates to the technical textile industry, and more specifically the textile reinforcements used for the production of composite materials.

  It relates more specifically to an improvement made to this type of textile reinforcements, intended to improve the mechanical properties of the articles incorporating these reinforcing reinforcements.

  Prior techniques The Applicant has described in document EP 395 548, a reinforcing reinforcement consisting of an assembly of at least three layers, namely a central layer and two layers of external reinforcements. The reinforcing layers consist of glass mats, that is to say sheets formed of generally discontinuous fibers. These two reinforcing mats sandwich a central layer, made from synthetic fibers, and having a certain thickness. In this way, during the molding of articles incorporating this type of reinforcement, the thermosetting resins flow inside this central layer, and come to impregnate the external reinforcement layers over their entire surface. These different layers are combined by sewing or knitting, so that the reinforcement has a large capacity for deformation, and therefore an ability to be integrated into molded articles having relatively complex shapes. However, the presence of the central layer based on synthetic fibers reduces the glass fiber content of the reinforcement, and therefore of the reinforcement, when the thermosetting resin is polymerized. This glass content, of the order of 20 to 25% by mass, may be insufficient in certain applications. One of the objectives of the invention is to provide textile reinforcements which have a higher glass content than the existing reinforcements, and this while retaining a good ability to spread the resin during molding.

  To increase the glass content, solutions have already been proposed, in which the reinforcing reinforcement is produced solely on the basis of glass fibers.

  Thus, reinforcements are known only based on glass fibers which have a knitted core. This type of reinforcement has not only the drawback of being relatively complex to manufacture, but also a very low capacity for diffusing the resin, which prevents it from being used in certain applications.

  Other types of textile reinforcements are also known, known under the abbreviation of CFRM for "Continuous Fiber Reinforcement Mat", which consist of continuous glass strands associated with a curable binder. This type of reinforcement is very slightly deformable, which limits it to applications of molded parts with low drawing.

  Another object of the invention is to provide a reinforcing reinforcement which is particularly deformable, so as to be shaped to multiple geometries of molds.

  DESCRIPTION OF THE INVENTION The invention therefore relates to a textile reinforcement, usable for the production of reinforcements used in particular for the manufacture of molded articles. In known manner, this type of reinforcement comprises at least two layers sewn together, a first of these layers consisting of a fibrous mat based on glass fibers.

  According to the invention, this frame is characterized in that the second layer is also formed by a fibrous mat of glass fibers.

  The fibers of this second layer have a titer and a length greater than those of the fibers of the first layer. They therefore have a higher stiffness than that of the fibers of the first layer. The fibers of the second layer also have lower wettability than those of the first layer.

  In other words, the invention consists in making a frame based on two different glass fiber mats. The first of these layers serves more particularly as reinforcement, while the second layer, which has a lower wettability, allows the diffusion of the resin and its good distribution over the entire surface of the reinforcement.

  By "lower wettability" is meant that the fibers of the second layer have a lower ability to be rapidly impregnated by the resins injected for molding, compared to the fibers of the first layer. In this way, the impregnation resins diffuse through the second layer, while they penetrate more quickly to the core of the fibers of the first layer to fix them there.

  In practice, the fibers used to form the second layer are semi-continuous fibers, that is to say having a length greater than 50 cm, or even one meter. In this case, the fibers can be considered continuous.

  The stiffness of these fibers makes it possible to give a greater volume. to this layer, thus promoting the diffusion of the injected resin.

  The frame described above can advantageously include a third layer. This additional layer is in contact with the second layer formed by the mat of long fibers. This additional layer is also formed by a mat of glass fibers, the fibers of which have a lower titer than those of the second layer, and they have a wettability greater than that of the fibers of the second layer. This third layer can therefore be identical or analogous to the first layer, and thus sandwich the second layer formed by the mat of long fibers. In this way, the second layer of quasi-continuous fibers ensures the diffusion of the impregnation resin to the two layers which sandwich it.

  In certain applications, the reinforcement may also comprise, on at least one of its external faces, a veil of fine fibers, for example synthetic fibers, intended to give a more regular surface finish to the reinforcement, and thus avoid the relatively irregular surface of the fibrous mats, or the seams which connect them, does not appear after molding.

  In practice, this or these veils of fine fibers can be associated with the adjacent layers by gluing 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 embodiment which follows, with the support of the appended figures in which: FIG. 1 is a view of a frame in accordance to the invention, shown with the different layers constituting it which are separated from each other.

  Figure 2 is a sectional view of the frame of Figure 1.

  Figure 3 is a summary perspective diagram showing a method of producing the frame according to the invention.

  Manner of Carrying Out the Invention As already mentioned, the invention relates to a textile reinforcement which can be used to reinforce articles obtained by molding. Such an armature can be produced by combining, as illustrated in FIG. 1, different layers.

  Thus, the first layer (4) is formed of a glass fiber mat comprising relatively short fibers, that is to say with a length of the order of 30 a few centimeters. These fibers are produced from yarns with a titer typically less than 50 tex.

  In a particular example, this layer can be produced from fibers with a unit length of 50 mm, so as to form a sheet having a surface mass of the order of approximately 300 g / m2. The fibers used are advantageously chosen from the range of fibers having medium to rapid wettability. The sizing rate of these fibers is low, with typically a loss on ignition rate (or LOI for Lost On Ignition) of less than 1%. The size used makes it possible to have a solubility rate in acetone greater than 60%.

  The second characteristic layer (3) is also produced from a mat of glass fibers, but the fibers of which are clearly longer than those of the first layer (4). Thus, these fibers have a length of several tens of centimeters, and may even be of a length greater than one meter.

  The titer of the fibers used is greater than that of the fibers of the first layer (4), and typically greater than 70 tex.

  Good results have been obtained by making the second layer (3) formed from a mat of fibers 90 cm in length, and having a surface mass of 600 g / m2, from yarns of a count of 70 tex.

  The yarns used are chosen from the range of yarns with a high sizing rate, typically with an LOI greater than 1.7%, with a solubility rate in acetone less than 50%. This size gives them relatively slow wettability and significant stiffness.

  In the form illustrated in Figure 1, the frame (1) also has a third layer (2), identical to the first layer (4). However, in certain applications, this layer can be produced from a different mat, or even not be used.

  In the form illustrated in FIG. 1, the reinforcement (1) also comprises a single surface layer (5), produced from a web of synthetic fibers, such as for example that described in document EP 0 694 643 Synthetic fibers have a titer of the order of a few decitex to a few tens of decitex, and are therefore much finer than the glass fibers used for the reinforcing layers (2,3,4). Overall, this surface veil can have a grammage of between 30 and 150 g / m2, and can be formed on the basis of synthetic fibers, such as polyester or acrylic among others, or of glass.

  The reinforcing layers (2,3,4) are assembled together, so as to maintain a deformation capacity. Advantageously, this connection can be made by sewing / knitting.

  The surface veil (5) is associated with the reinforcing layers (2,3,4) by various means, such as sewing or gluing, as illustrated in FIG. 2.

  FIG. 3 illustrates one way of obtaining the invention. Thus, the glass strands 15 (14) are routed to the cutting station (11). Rollers (17,18) equipped with blades cut the wires (14) into fibers of the order of a few centimeters in length which, by gravity, and after being brewed, are deposited regularly on the conveyor belt ( 25), to form the layer (4). This layer (4) receives the fibers cut at the level of the station (12), from glass threads (15) of higher quality. The rollers (19,20) of the station (12) are arranged to cut fibers of a greater length, of several tens of centimeters. These different fibers are also deposited in an organized manner and so as to retain a large volume and a large thickness, to form the second layer (3).

  In the same way, the assembly receives the sheet (2) of fibers cut at the station (13) from son (16) of lower strength. These different plies are then associated with each other at the assembly station (23), to form most of the reinforcing part of the frame. The fibrous web (5), which can also be present on one or two of the layers of the reinforcement, is then associated in a later stage, as illustrated in FIG. 3. It can also be also sewn or knitted with the layers fibers (2,3,4) in the same step.

  The reinforcements thus produced have the advantage of retaining a very high deformability, as well as an ability to diffuse the resin, and this making it possible to obtain glass contents by mass, clearly higher than those of the existing reinforcements, and which can reach values of around 40%.

Claims (6)

  1. Textile reinforcement (1) usable for the production of reinforcements used in particular for the manufacture of molded articles, comprising at least two layers sewn together, a first of these layers consisting of a fibrous mat (2) based of glass fibers, characterized in that the second layer (3) is also formed by a fibrous mat of glass fibers, the fibers of the second layer (3) having a titer and a length greater than those of the fibers of the 10 first layer (2), and a lower wettability than that of the fibers of the first layer (2).   2. Textile reinforcement according to claim 1, characterized in that the fibrous mat of the second layer is formed of continuous fibers. 15 3. Textile reinforcement according to claim 1, characterized in that the fibrous mat of the second layer (3) is formed of fibers of length greater than cm.   4. Textile reinforcement according to claim 1, characterized in that it comprises an additional layer (4) in contact with the second layer, formed by a mat of glass fibers, the fibers of which have a lower titre than that of the fibers of the second layer, and have a wettability greater than that of the fibers of the second layer.   5. Textile reinforcement according to claim 1, characterized in that it comprises on at least one of its external faces a veil of synthetic fibers (5).   6. Textile reinforcement according to claim 5, characterized in that the veil of synthetic fibers is associated with the adjacent layers by gluing or sewing.