WO2013190221A1

WO2013190221A1 - Process for manufacturing a textile reinforcement for composite materials, and reinforcement thus obtained

Info

Publication number: WO2013190221A1
Application number: PCT/FR2013/051389
Authority: WO
Inventors: Philippe Sanial; Julie FOUREL
Original assignee: Chomarat Textiles Industries
Priority date: 2012-06-18
Filing date: 2013-06-13
Publication date: 2013-12-27
Also published as: FR2992000B1; FR2992000A1

Abstract

The invention relates to a process for manufacturing a textile reinforcement for composite materials, comprising: ■ a core (3), and at least one reinforcing layer (7, 14) based on a mat of cut fibres, in which: ■ said core layer (3) is interlocked by needle punching with a first reinforcing layer (7) formed from a mat based on fibres (5) of a first type; an assembly, formed by a second reinforcing layer (14) formed from a mat of fibres (11) of a second type and a surface veil (17), is deposited on said first reinforcing layer (7); and ■ said assembly formed by the second reinforcing layer (14) and the surface veil is interlocked with the first reinforcing layer (7) by needle punching, in which the fibres (5, 11) of the first and second type differ in one of the following parameters: linear density, length or density.

Description

PROCESS FOR PRODUCING A TEXTILE REINFORCING REINFORCEMENT FOR COMPOSITE MATERIALS, AND ARMATURE THUS OBTAINED Technical Field

The invention relates to the field of reinforcement used for the manufacture of composite materials that can be used to produce rigid structures. More particularly, it relates to reinforcements having high performance mechanical properties, combined with three-dimensional geometries that can be complex.

Such an armature is based on a structure as described in EP 0 395 548. This type of reinforcement comprises a draining core, combined with two reinforcing layers intended to be impregnated with a sand thermoset resin which is distributed over the all of the piece to be made by circulating inside the draining layer.

Previous techniques

However, the reinforcements as described in EP 0 395 548, have a disadvantage of aesthetic order. More specifically, the outer layers, which impregnate resin to impart the mechanical properties to the composite structure, have a relatively irregular surface condition. Indeed, these outer layers are made based on relatively large title fibers, so that they are relatively thick, and appear on the apparent face of the structure.

However, in some applications, a very regular and homogeneous aesthetic appearance is sought. To do this, in EP 0 694 643, it has been proposed to include in the reinforcement a surface layer formed of a veil of fine fibers, in the thickness of which are housed the thick fibers of the reinforcing layers. . Under these conditions, the outer surface of the composite structure appears smoother since the irregularities of the reinforcing layers are compensated by the thickness of the finer fiber web.

However, such a structure is also not so satisfactory, insofar as all or part of the layers that compose it are joined together by the sewing or knitting operations. These sewing threads or knitting provide a very effective solidarity of different layers together, but tend to block the movement of the different layers together.

Thus, in the production of complex shapes, with relatively small radii of curvature, the low deformation capacity of such reinforcements leads to the appearance of folds, or at the very least of zones whose thickness is not totally constant. , and differs from those in totally flat areas.

A solution was provided using, as described in EP 0 659 922, an assembly of the various layers of the reinforcement by needling operations. Thus, the central core, covered with two reinforcing layers, themselves covered with a surface web, are assembled by a needling operation, which causes certain fibers of the web and reinforcing layers to become embedded in the thickness of the core layer.

Such a solution, even if it is satisfactory for certain applications, has the disadvantage of limiting somewhat the deformability, insofar as the veil of the outer surface layer is intimately connected to the core which is at the heart of the reinforcement. . Another solution has been described in EP 2 145 036, which consists in assembling all the different layers by means of hot melt materials, which may be contained in the fibers themselves. A heating operation makes it possible to express these thermo-fusible properties, so that the different layers are mechanically bonded together by the material having melted. Such a solution, however, has several disadvantages among which there is a relatively low deformability, and a complexity of the manufacturing process since it involves a heating step. Presentation of the invention

The invention therefore aims to solve all the problems mentioned above by providing a textile reinforcement which has both good deformation capacity, while maintaining a very homogeneous exterior appearance. Thus, the invention relates to a method of manufacturing reinforcement textile reinforcement for composite materials, comprising a core and at least one reinforcing layer based on a mat of cut fibers.

According to the invention, this method comprises the following steps during which:

^Bonding the core layer by needling with a first reinforcing layer formed of a mat based on fibers of a first type;

^■ is deposited on the first reinforcing layer a second layer of reinforcement formed of a mat of fibers of a second type;

The second reinforcing layer is secured by needling to the first reinforcing layer.

In practice, the fibers of the first and second types may differ in one of the following parameters: their title, their length or their density. In other words, the invention consists in producing the reinforcement using a reinforcing layer which consists of at least two distinct elementary layers, with slightly different properties with respect to the behavior with respect to the resin, and therefore the final mechanical properties of the composite structure.

These different elementary layers of reinforcement are not secured in the same way inside the frame. In other words, the elementary reinforcing layer located closest to the core is more intimately connected to the latter than is the reinforcing layer further from the core.

The fact that the outermost layer is not intimately linked to the soul, or even not linked at all to the latter, confers an additional degree of freedom in the thickness of the frame which is thus much more deformable, and therefore suitable for producing structures of complex shapes.

In some applications, it may be advantageous to provide an outer layer formed of a surface web. In this case, the surface web is deposited on the second reinforcing layer, and the assembly formed by the web and the second reinforcing layer is secured to the first reinforcing layer by needling.

It should be noted that the reinforcement thus produced makes it possible to obtain particularly homogeneous surface conditions, since the surface veil is not secured to the entirety of the layers of the reinforcement, but essentially to that on which it rests .

In practice, different needling modes can be used. In a first embodiment, the needling of the second reinforcing layer may penetrate the core in a shallower manner than the needling of the first reinforcing layer. In other words, the outermost reinforcing layer is slightly secured to the core layer, but with a lower gripping force than that which connects the inner reinforcing layer and the core.

In another embodiment, the needling of the second reinforcing layer penetrates only into the first reinforcing layer, without reaching the central core.

The invention thus also covers a reinforcing reinforcement for composite materials which comprises:

■ a core based on synthetic fibers,

^■ a first reinforcing layer made of a mat consisting of staple fibers of a first type,

^■ a second layer of reinforcement based on a mat consisting of fibers of a second type,

This second reinforcing layer being secured to the first reinforcing layer by needling.

According to different embodiments, the length of the cut fibers of the first type may be less than the length of the fibers of the second type.

In other words, the elementary reinforcing layer which is located closest to the core has fibers of shorter length, to allow the passage of the resin in the direction of the outermost reinforcing layer, made from longer fibers or more densely distributed. Advantageously, the armature may comprise an outer layer formed of a fibrous web based on fibers of a lower titre than that of the fibers of the reinforcing layers, and secured to the second reinforcing layer with the first reinforcing layer.

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:

Figure 1 is a schematic view of an installation for implementing the method according to the invention.

Figures 2 and 3 are schematic sectional views of the frame according to the invention made according to variants concerning the needling steps. Of course, the thicknesses of the various layers shown in the figures are given for information only to facilitate understanding of the invention, and may differ from reality.

Ways to realize the invention

As illustrated in FIG. 1, the installation 1 comprises a first feed station 2 in a layer 3 intended to form the core of the future reinforcement.

In the form shown, this layer 3 is made beforehand, and is then unwound at the entrance of the installation 1. It could of course be carried out continuously just upstream of the installation 1.

In the production direction, the installation 1 then comprises a station 4 through which fibers 5 are cut to form segments which are deposited in mat on the core layer 3. These fibers 5 are obtained from continuous yarns 6 of a high tenacity material such as in particular glass, or the like. Downstream of the station 4, there is a first needling station 8 which makes it possible to join the reinforcing layer 7 to the core 3.

Thus, at the exit of the needling station 8, an assembly formed of the reinforcing layer 7 joined to the core 3 is obtained.

Subsequently, there is a station 10 for depositing by gravity fibers 11 made by a section of a high tenacity yarn 12, which may be identical or different from the wire 6 cut at the first station 4.

The title of the yarn 12 as well as the length of the cut fibers may vary, as may the density of the deposited fibers.

In a post located downstream 16, is proceeded to the establishment of a web of surface 14, made from synthetic fibers of low title, with respect to the fibers used to produce the reinforcing layers 7, 14. Typically , the surface web 17 is unwound from a roll of material made independently. This surface veil may be optional, and not be used in certain applications, in particular those requiring high deformability of the reinforcement before impregnation.

After the setting up of the surface veil 17, the installation comprises a second needling station 20 which makes it possible to secure the entire surface veil 17 and the layer 14 issuing from the station 10, with respect to the assembly formed of the first reinforcing layer 7 and the core 3.

Insofar as the set of upper layers must be secured more loosely with respect to the core, or not be secured at all to the core 3, the needling conditions of the station 20 differ from those of the first one. 4. Thus, needling should be preferred, the depth of which penetration is smaller, so as to limit the feed of the fibers of the upper layers in the soul.

In the following, the frame must be returned or undergo other treatments for the opposite side.

Of course, the installation 1 described in FIG. 1 shows a continuous manufacture in which the two needles intervene simultaneously as production proceeds, but it is also possible that the core 3 and the first reinforcing layer 7 is performed in an operation independent of the second needling. Similarly, it is conceivable to have several successive reinforcement layers with a progression of mechanical properties (yarn count, fiber length, density of the layer) depending on the desired applications. Depending on the operating conditions, different configurations can be obtained.

Thus, as illustrated in FIG. 2, the core layer 103 is associated in a first step with a first reinforcing layer 107, by a needling which causes the entrainment of certain fibers 108 of the layer 107 inside the core 103, as shown schematically.

Subsequently, the second reinforcing layer 114 and the surface web 117 are deposited on the first reinforcing layer 107, and a second needling is performed. This needling causes the displacement of certain fibers of the surface web 117, or even of the second reinforcing layer 114 inside the first reinforcing layer 107, without this penetrating into the thickness of the coating layer. soul In another configuration illustrated in Figure 3, the first reinforcing layer 207 is secured to the core 203 in a similar way, with the passage of some fibers 208 of the reinforcing layer 207 inside the core 203.

After placement of the second reinforcing layer 214 of the web 217, the second needling causes the driving of some surface web fibers 218 217, and possibly the reinforcing layer 214 through the first layer of reinforcement 207, and also a fraction of the thickness of the core layer 203.

10

Of course, the different thicknesses as well as the shape of the fibers shown are only schematically to understand the invention.

By way of example, different types of reinforcement have been made by combining the following parameters.

Example 1

A first layer is formed based on synthetic threads of 40 to 70 dtex, with a density of the order of 100 g / m ² . This core layer receives a fibrous mat made from glass fibers of a titre of 30 tex.

The fibers are cut with a unit length of 20 cm, to form a layer of the order of 100 g / m ² . Then, the second reinforcing layer is made from text fibers of 15 tex with long fibers of the order of 80 cm, and with a density of the order of 500 g / m ² .

A surface veil based on synthetic fibers of a global density is used.

30 Example 2

The steps of Example 1 are repeated using, as first reinforcing layer, shorter fibers, of the order of 5 cm long, for a density of the first reinforcing layer of 100 g / m 2.

The second reinforcing layer is made from fibers similar to Example 1, but with a length of the order of 5 to 10 cm. The whole is covered with a veil similar to Example 1. Example 3

The steps of Example 1 are repeated, without surface veil.

Example 4

The first layer is made by a mechanical assembly (needling) between synthetic fibers and fiberglass.

The sheet produced by the synthetic fibers (polypropylene) weighs about 180 g / m ² . This sheet is needled with about 350 g / m ² of glass fiber cut between 50 and 100 mm. The title of the fiberglass used is about 33 tex.

This first layer is then needled with a fiberglass mat of about 300 g / m ² . The fiberglass used is a mixture of fibers with a length of between 50 and 100 mm. The title of the fiberglass used is about 15 tex. This sheet of fiberglass is deposited on the side of the synthetic web.

Example 5

The first layer is made by a mechanical assembly (needling) between synthetic fibers and glass fibers. The sheet produced by the synthetic fibers (polypropylene) weighs about 180 g / m ² . This sheet is needled with about 350 g / m ² of glass fiber cut between 50 and 100 mm. The title of the fiberglass used is about 15 tex.

This first layer is then needled with a fiberglass mat of about 300 g / m ² . The fiberglass used is identical to that of the first layer. This sheet of fiberglass is deposited on the side of the synthetic web.

It follows from the foregoing that the invention makes it possible to produce textile reinforcements for the production of a composite part, which has both a particularly homogeneous surface state, combined with a large deformability to adapt to complex geometry.

Claims

1 / A method of manufacturing a reinforcing textile reinforcement for composite material comprising:

■ a soul (3),

^■ at least one reinforcing layer (7, 14) based on a chopped strand mat, wherein:

^The said core layer (3) is secured by needling with a first reinforcing layer (7) formed of a fiber-based mat (5) of a first type,

^■ is deposited on said first reinforcing layer (7) an assembly formed by a second reinforcement layer (14) formed of a mat of fibers (1 1) of a second type, and a surface web (17),

^■ are joined by needling said assembly formed by the second reinforcement layer (14) and the surface web (17) to the first reinforcing layer (7), wherein the fibers (5: 1 1) of the first and second type differ by one of the following parameters: title, length, or density.

The method of claim 1 wherein the needling of the second reinforcing layer (204) penetrates the web (203) less deep than the needling of the first reinforcing layer (207).

3 / A method according to claim 1, wherein the needling of the second reinforcing layer (1 14) penetrates only in the first reinforcing layer (107).

4 / A method according to claim 1, wherein is deposited a surface web (17) on said second reinforcing layer (14), and is secured by needling to the first reinforcing layer (7) the assembly formed of the second reinforcing layer (14) and the surface veil (17), 5 / reinforcing textile reinforcement for composite materials comprising:

^■ a web (103, 203) based on synthetic fibers,

^■ a first reinforcing layer (107, 207) based on a mat consisting of staple fibers of a first type,

A second reinforcing layer (114, 214) based on a mat formed by fibers of a second type,

^■ a fibrous web based on lower tracks fibers titles of the fibers of the first and second type,

said second reinforcing layer (1 17, 217) and the fibrous web being secured to the first reinforcing layer (107, 207) by needling.

6 / textile reinforcement according to claim 5, wherein the length of the cut fibers of the first type is less than the length of the fibers of the second type.