EP0296996A1 - Textile structure, especially for composite materials, and manufacturing method thereof - Google Patents

Abstract

Textile structure for composite materials in particular, and process for its manufacture. The subject of the invention relates to the technical field of weaving methods. The textile structure according to the invention comprises at least two planar sheets whose directions are maintained in adjoining position by a bonding means (1) oriented so that it cuts at least the directions of the fibres of the sheets which are outermost or the most complex. <IMAGE>

Description

The object of the invention relates to the technical sector of weaving methods.

The invention relates to a textile complex in layers, such as for example polyesters reinforced with a glass fabric. Such materials are well known and in common use. In general, they are reinforced by a fabric in which the weft threads and the warp threads are regularly intertwined. Most often for mechanical reasons, the weft threads and the warp threads are orthogonal.

These fabrics have drawbacks resulting in particular from the interlacing of the warp and weft threads and their orientation at right angles.

Due to the interpenetration of the warp and weft plies, the wires are not straight, but have a certain undulation, so that they do not offer, in the direction of their length, their maximum mechanical characteristics.

Due to the 90 ° positioning of the weft threads and warp threads, the complex only has resistances in two orthogonal directions, those of warp threads and weft threads, which offer 70 to 75% of the resistance nominal wire if they were straight. In a diagonal direction with respect to these two previous directions, the woven reinforcement offers only less than 25% of the resistance of the threads which compose it.

Methods are known for adding to a fibrous reinforcement composed of two unidirectional nonwoven plies at least one ply of threads in a diagonal weft. However, these methods are complicated either because of the design of the diagonal frame, or because of the method.

We can cite for example French Patent 2,522,027 which reports a textile support whose structure comprises a ply of composite warp threads and a ply of weft threads, these two plies being deposited one on the other, without interpenetration. In diagonal wefts, there are at least two layers each composed of a plurality of wires. The son of the two plies of diagonal wefts are repetitively opposite directions thus forming opposite rafters, each of which occupies only part of the width of the fibrous support. The repetition of these chevron designs causes the chevrons to shorten lengthwise and widthwise of the fibrous reinforcement thus formed. However, the diagonal frame is not unidirectional.

This type of structure makes it possible to deposit the plies of diagonal wefts only on one side of a fibrous support if necessary. On the other hand, the diagonal weft is, in one direction, divided into several portions of threads of poorer quality than a single piece thread crossing the entire width of the fibrous support.

All of the plies of this known fibrous support are held together by tying threads, in chains, with the necessary knotting.

Finally, in the reinforcements or woven complexes, the threads or fibers, given their intertwining, do not slip relative to one another, despite certain suitable armor. The possibility of significant deformation is therefore reduced with the risk of breaking the stressed wires or of folds forming during shaping. However, the current or envisaged applications for fiber-reinforced composite materials increasingly require and require:
- good deformability, in order to be possibly stamped into complex and deep shapes;
- resistances in several directions predetermined by the use and no longer by the only directions of the warp and weft threads;
- in certain cases, a fineness of the reinforcement, in the direction of its thickness, which the known supports do not allow according to which fabrics must be stacked according to the different directions of maximum resistance required.

The problems being thus posed, the invention set itself the aim of remedying the drawbacks cited by providing a solution in the form of a unitary textile complex having resistances in as many directions as there are layers and more generally according to at least two non-orthogonal directions.

This textile complex is constituted by a plurality of flat unidirectional sheets, deposited one on the other without interpenetration, said sheets being held together by a binding wire oriented so that it cuts the directions of the son or fibers of the sheets. In each layer, the threads or fibers are laid flat in a rectilinear manner, to offer, in the direction in which they are laid, the optimum resistance properties.

Given this structure, the son or fibers of the sheets can easily move relative to each other, which allows the possible drawing of the complex thus obtained.

The multidirectional textile complex according to the invention comprises plies of threads or fibers oriented and linked to a unique and independent weaving process for each ply.

A directional sheet, in a given orientation, is no longer formed by a shuttle, but is executed by alternately depositing one or more threads or fibers between the claws of two endless chains arranged laterally, in a manner parallel to the axis Manufacturing. The son or fibers are deposited at the desired angle, the speed of advance of the claw chains being equal to that of manufacturing the textile complex. The spacing of the claws of the chains allows a juxtaposed deposit of the wires or fibers in the complex.

• La figure 1 montre par une vue en perspective le procédé de fabrication notamment l'assemblage des nappes unidirectionnelles.
• Les figures 2 et 3 sont des vues en plan d'exemples nullement limitatifs du complexe textile selon l'invention.
• La figure 4 montre un exemple de procédé de pose du fil de liage dans le cas d'un complexe conforme à celui de la figure 3.
• La figure 5 montre un exemple du procédé de réalisation d'une nappe unidirectionnelle dont les fils ou fibres sont orientés angulairement, en "diagonale".

The invention is set out below in more detail with the aid of the appended drawings which show by views of essentially schematic characters, the manufacturing process and examples of embodiment of the textile complex.

• Figure 1 shows a perspective view of the manufacturing process including the assembly of unidirectional sheets.
• Figures 2 and 3 are plan views of non-limiting examples of the textile complex according to the invention.
• FIG. 4 shows an example of a method of laying the binding wire in the case of a complex conforming to that of FIG. 3.
• FIG. 5 shows an example of the process for producing a unidirectional sheet of which the yarns or fibers are oriented angularly, "diagonally".

According to the invention, the textile complex is produced from several independent layers (N1, N2, N3, N4, ...), each composed of a plurality of unidirectional threads or fibers. The son or fibers of each ply are oriented in a determined angular direction and different for each of said plies and have no interference or penetration with the plies which are contiguous to it.

On the other hand, the threads or fibers are arranged flat, in a rectilinear manner and offer, in the direction in which they are arranged, their optimum properties. The set of plies (N1, N2, N3, N4, ...) is held by one or more binding threads (1) oriented so that it cuts the directions of the threads or fibers of the plies.

It is first of all advisable to describe the process for manufacturing the textile complex, with particular reference to FIG. 1.

The different unidirectional layers (N1, N2, N3, N4, ...) are each executed in a first area (Z1) of the manufacturing process, before being superimposed (Area Z2), then held together (Area Z3) by the binding wire (s). In the example illustrated, the complex is executed from four distinct layers, namely, in order of superposition:
- a sheet (N1) composed of threads or fibers (2) arranged angularly with respect to the selvedges so as to constitute a weft called "diagonal";
- a sheet (N2) composed of threads or fibers (3) arranged perpendicular to the selvedges to form a "normal"weft;
- a sheet (N3) composed of threads or fibers (4) arranged in a chain;
- a sheet (N4) composed of son or fibers (5) arranged angularly with respect to the selvedges so as to constitute a so-called "diagonal" frame oriented in a reverse manner to that of the sheet (N1).

The layers (N1), (N2) and (N4) are each obtained by screening of a single thread or fiber according to a process which will be described later and capable of giving the desired angular orientation of the threads. The ply (4) is obtained in a conventional manner.

In the zone (Z2), the various layers are brought together in superposition and maintained in slight back pressure by any known and appropriate means. At this level, the textile complex is not yet operational, since the sheets are not linked.

At the exit of this zone (Z2), symbolized by the transverse axis (Y - Y ′), the binding threads (1) are arranged, for example by means of a set of needles (6). The textile complex thus produced is then wound on a cylinder (7) for example.

Regarding the laying of the binding threads (1), the latter can be arranged in different ways, whatever the structure of the complex, on the sole condition that said threads intersect the threads or fibers of the unidirectional sheets constituting the outer top faces and from below said complex. In the example in FIG. 1, these are the layers (N1) and (N4).

It therefore appears necessary, when the binding threads (1) are parallel to the warp threads of one or more plies, that the threads or fibers of the outer plies are arranged in a weft, with any angular orientation. However, for certain applications of composite materials, it is necessary for the complex to be of reduced thickness and / or require only two isotropic directions according to the orientations of the determined wires or fibers.

FIG. 4 shows a particular example of the textile complex composed only of two unidirectional plies, namely a ply with warp threads (4) and a ply with threads (5) arranged in a so-called "diagonal" weft. The wires (4) and (5) of each of the layers, are therefore angularly oriented between them, at an angle different from 90%.

With this type of structure, so that the unidirectional layers are held together, the binding threads (1) cannot be arranged parallel to the warp threads (4), but transversely to the latter while crossing the diagonal weft threads ( 5).

In this case, there is a single tying thread (1) which successively constitutes, at regular intervals, straight cross sections (1a) joined alternately by sections (1b) which extend parallel to the warp threads. Obviously, these are the different cross sections (1a) which maintain the two layers between them.

This type of binding, in the form of slots, can be obtained by any known and appropriate means. For example, means of implementation are shown diagrammatically in FIG. 4.

At the level of the zone (Z2), at the height of the transverse axis (Y - Y ′), a means (8), of the sewing machine type, is mounted on a support frame (9), movable in translation, and which spans the entire width of the complex. The machine sewing is itself mounted with transverse displacement capacity (10), along the support frame (1) so as to make the straight sections (1a) of the binding thread.

As a straight cross-section is formed (1a), the mobile support (9) moves axially along the textile complex in the direction of the winding cylinder (7) and at the same speed as said complex . This movement of movement of the support (9) which accompanies the complex, makes it possible to orient the cross sections (1a) of the binding wire in a chosen direction which can be square (case of FIG. 4) or diagonally, at the only condition to cut the two directions of the threads of each of the layers.

After forming a section (1a), the support (9) is moved axially, in the opposite direction to that of the complex, that is to say away from the winding cylinder (7), to form the section ( 1b) which extends parallel to the ply of warp threads (4). The sewing machine then forms a new cross section (1a) and so on.

Provision is made to equip the mobile support (9) with several sewing machines (8) taking into account the desired width of the fibrous complex. These sewing machines in this case each form a cross section (1a) over only part of the width of the complex. the working zones of each machine are determined to ensure the continuity of the straight sections (1a) of the binding wires.

As indicated above, upstream of the zone (Z2), the different plies are produced according to different methods depending on the weave desired for each of said unidirectional plies. FIG. 5 illustrates an embodiment.

The sheet or plies composed of warp threads (4) are produced in a conventional manner, by any known method. With regard to the formation of unidirectional sheets with son or fibers arranged transversely, each of said sheets cooperates with a compound device essentially two parallel endless chains or belts (11) and (12), and arranged along the manufacturing axis of the complex, parallel to the warp threads.

Each endless chain system (11 - 12) is arranged laterally along the edges of the corresponding plies.

Hooks or claws (13) are mounted projecting from the chains (11) and (12) which are also subject to motorized pulleys or pinions to be driven linearly in the same direction as that of movement of the complex. The arrangement and the number of claws (13) are determined according to the angular orientation desired by the diagonal frame.

A donor (14) located upstream of each unidirectional diagonal ply, in combination with the endless chain system, makes it possible to supply the corresponding ply with threads or fibers. This donor (14) is shaped to hook the weft thread (5) alternately and successively on a claw of the endless chain (11) then on a claw of the endless chain (12). The donor (14) is also oriented angularly as a function of the degree of inclination desired for the frame.

Correspondingly, the endless chains or belts (11) and (12) of each system are offset in the longitudinal direction of the complex. The different weft plies are therefore produced independently of the other plies.

To deposit the weft ply (s) thus executed on, for example, the chain ply, at the level of the zone (Z2), it is necessary to release this weft from the claws (13). This is done easily and automatically, in particular at the level of the tilting, at the end of the chain, of the claws (13). The endless chain or belt systems (11 - 12) can have an olbic work plane with respect to the horizontal work plane of the chain ply, or a parallel work plane.

The endless chain devices (11 - 12) with donor (14), the number of which corresponds to the number of weft plies desired, can therefore be arranged either in series along the warp ply, or in superposition.

Given this specific design of the complex and its manufacturing process, the main advantages resulting from it are as follows:

The unidirectional yarns or fibers of a sheet have no penetration or interference with the sheets which are contiguous to it and are laid flat in a rectilinear manner and therefore offer, in the direction in which they are laid out, the optimal properties .

Due to this flat arrangement of threads or fibers, the complex does not include "hollow" spaces in which elements of the matrix could be stored and would contribute to bringing down the characteristics of the material by a poor proportion of fibers / matrices. This arrangement also promotes good wettability of the fibers, the matrix propagating well by capillarity.

Since the plies are maintained by an unbridled binding wire, the complex obtained has characteristics of deformability such that it becomes capable of drawing without breaking fibers. These tend to improve the mechanical characteristics of the material. The different angles of the plies are maintained during the deformation.

The binding wire maintains the plies of the reinforcement thus allowing the dry reinforcement to be cut according to a "pattern" necessary for the production of a part without disordering the orientation of the plies.

From this basic design of the complex, different variant embodiments may fall within the scope of the invention, as indicated below:

The number of layers is limited only by the thickness wettable by the matrix. The tablecloths each having their own installation system, they can be of a different nature (fiber) and at their own angle.

The stacking order of the layers is not fixed and is arranged according to the intended applications. Only the tablecloth composed of warp threads, in the case of a complex with at least three layers, must be sandwiched between the two other tablecloths.

It is expected to have between the unidirectional sheets, sheets of complex in short fibers of the sail or mast type, in order to give the complex more thickness without loading it with long fibers and thus improve the flexural modulus.

The nature of the threads or fibers making up each of the layers can be very diverse. For example, the textile complex according to the invention can consist of a variety of long fibers, threads or wicks, which can be used alone or in combination, such as for example a carbon fiber sheet, a wire sheet of steel, a sheet of fiberglass and a mast of short fibers in the same reinforcement, linked by a polyamide monofilament.

The method according to the invention makes it possible in particular to use boron and silicon carbide fibers, the characteristics of which are advantageous, but which until now have not been usable in known fibrous reinforcements, given their brittleness at friction , making them unusable.

Claims (8)

-1- Textile complex for composite materials, in particular comprising several layers of superimposed unidirectional threads or fibers, characterized in that it comprises at least two flat layers, the directions of the threads or fibers of which are intersected, said layers being held in joined position by a binding means (1) oriented so that it cuts at least the directions of the fibers of the sheets, the most external or complex. -2- Complex according to claim 1, characterized in that each ply is composed of one or more unidirectional son or fibers oriented in a different angular direction determined for each of said plies having no interpenetration with the plies which are contiguous. -3- Complex according to claim 1, characterized in that it comprises two unidirectional layers, one of which is composed of son or fibers divided into chain (4) and the other of at least one wire or fiber (5) arranged in a so-called "diagonal" weft, said plies being held together by at least one binding wire (1) suitably oriented so as to cross the direction of the warp threads or fibers (4) and the weft threads or fibers (5) . -4- Complex according to claim 3, characterized in that the binding wire successively constitutes at regular intervals, straight cross sections (1a) which cut the warp threads (4) and the weft thread or threads (5), said sections being joined alternately by sections (1b). -5- Complex according to claim 1, characterized in that it comprises at least three unidirectional sheets with a sheet composed of son or fibers arranged in a chain (4), said warp ply being disposed between the two other plies each composed of at least one thread or fiber arranged in a weft known as "diagonal (2) and (5) and the directions of which intersect, all of said plies being held in joined position by at least one binding wire (1) parallel to the son or chain fibers (4). -6- Complex according to any one of claims 1, 3 and 5, characterized in that the ply (s), other than the ply (s) composed of son or fibers arranged in a chain, are each obtained by screening of at least a wire or fiber subject to means capable of giving the desired angular orientation of said son or fibers. -7- Complex according to claim 1, characterized in that it comprises a plurality of layers of unidirectional son or fibers held in superposition in a contiguous manner, the angular orientation of the son or fibers or fibers making up each of said plies being predetermined in order to obtain the isotropic character of resistance according to said orientations, this isotropic character being independent of the order of superposition of said layers. -8- A method of manufacturing the textile complex according to any one of claims 1 to 7, for composite materials in particular comprising several layers of superimposed unidirectional son or fibers, characterized by the following essential steps:
- each of the unidirectional layers (N1, N2, 3, N4, ...) is produced separately;
- said layers are superimposed;
- Maintaining said plies in contiguous position by a binding means (1) having no mechanical function in the complex.

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