EP0283334A1 - Woven reinforcement for composite material - Google Patents

Abstract

This reinforcement is formed by a basic pattern constituted by fifteen woof threads R in a staggered arrangement forming six vertical columns 1 to 6 of alternately two and three threads and at least five horizontal lines 1 to 5 each of three threads, and by six imbricated layers C1 to C6 of at least two parallel threads, namely at least twelve threads a, b, c . . . 1, each connecting every third woof thread of the same column in two adjacent lines and the warp threads of the consecutive layers connecting the woof threads in alternating columns.

Description

The present invention relates to composite materials and it relates more particularly to a woven reinforcement having a new texture for the manufacture of parts with very high resistance.

• - Caractéristiques, notamment mécaniques, exceptionnelles
• - Aptitudes remarquables à orienter les constituants dans les directions des contraintes auxquelles est soumise la structure, à telle enseigne que celle-ci possède des caractéristiques inégalables.

Composite materials generally have the following two advantages:

• - Characteristics, particularly mechanical, exceptional
• - Remarkable aptitudes to orient the constituents in the directions of the constraints to which the structure is subjected, so much so that it has incomparable characteristics.

The composite materials consist of a reinforcement and a binder. The frame is essentially made from very resistant textile fibers (glass fibers, silica fibers, carbon fibers, silicon carbide fibers, alumina fibers, aromatic polyamide fibers, etc.) and the binder can be an organic resin. or a refractory product or a metal.

The present invention aims to achieve a new type of frame. As produced according to the invention, the frame is said to be woven. By woven reinforcement is meant an interlacing of textile fibers which stands by itself and has the dimensional characteristics of the part made of composite material.

The binder required to finish the structure can be deposited in the woven reinforcement, either by liquid or by gas. The liquid route consists in making a liquid impregnate penetrate into the reinforcement which, by subsequent treatment, is transformed to such an extent that the structure thus made up has the required characteristics. By the gaseous route is meant a process such that the armature is placed in an enclosure at a fixed temperature and pressure and is subjected concomitantly to a gas flow, the molecules of which decompose in contact with the fibers constituting the armature (chemical deposition vapor phase). After a certain time, the reinforcement plus the binder have obtained the required characteristics.

The literature describes reinforcements with reinforcements in different directions:

- Reinforcements with fibrous reinforcement in random directions (called random D).

This is particularly the case with felts. These reinforcements have the advantage of having very homogeneous characteristics. They often have the unacceptable disadvantage of having weak mechanical characteristics due to the fact that the fibers are short (less than 1 centimeter) and little linked to each other by the binder.

- Reinforcements with fibrous reinforcement in 1 direction (say 1D).

Armatures of this type are most often used as by-products of armatures in more than one direction (with the exception of hazards D) or in the sports and leisure industry. They consist of long fibers (several meters) aligned parallel to each other.

- Reinforcements with fibrous reinforcement in 2 directions (called 2D).

These are all kinds of fabrics and wound products. These fabrics are used as monolayers, mainly in the clothing industry. In most other industries, 2D is used as a multilayer. The resulting structures have excellent mechanical characteristics in the direction of the reinforcements. On the other hand, in the perpendicular direction, the characteristics are very weak, so much so that interlayer cleavages (also called delaminations) can occur during deposition of the binder, during an impact or during cyclic stresses, often prohibitive for the intended use.

- Reinforcements with fibrous reinforcement in 3 directions (called 3D).

These are much more sophisticated products, the use of which is mainly reserved at present for the aeronautical and ballistic sectors. The resulting structures have excellent characteristics, especially in the three directions of the reinforcing fibers. On the other hand, they do not present a risk of delamination.

The reinforcing fibers can be arranged either along the three axes of a normal trihedron (triorthogonal 3D), or along radial, circumferential and longitudinal directions of the axisymmetric parts (polar 3D).

The disadvantage of 3D reinforcement is that, as obtained by existing methods to date, the spacing between the layers of the wires is too large to meet the needs of thin structures, which can be of the order of 1 to 3 mm. In addition, due to its geometric construction, the 3D has large cavities. These most often complicate the operation of depositing the binder in a homogeneous manner, both liquid and gas.

There are many methods for making fibrous reinforcements. Some of these processes are in the public domain; others are protected by invention patents, for example the applicants' patents FR-2,395,340 and FR-2,531,459.

There are reinforcements with more than three dimensions (4D, 5D, 9D and 11 D). They have the advantage of having good homogeneous characteristics. However, their use is very marginal, due in particular to the extreme complexity of their production by automatic methods.

The object of the invention is to provide a new reinforcement which is particularly suitable for producing thin structures and in particular for elements for protecting spacecraft when they re-enter the atmosphere, or other applications, having very good mechanical characteristics. in the direction of the reinforcements, equivalent to a stack of 2D, indelaminable like a 3D, but without fibers perpendicular to the wall, that is to say an intermediate reinforcement between 2D and 3D.

au fil de trame R de la colonne 5, dans la ligne 2, soit

, le second fil b de la première nappe C1 reliant le fil de trame R de la colonne 2, dans la ligne 3, soit

au fil de trame R de la colonne 5, dans la ligne 4, soit

le premier fil c de la deuxième nappe C2 reliant le fil de trame R de la colonne 1 dans la ligne 2, soit

, au fil de trame R de la colonne 4, dans la ligne 1, soit R 4 ; le second fil d de la deuxième nappe C2 reliant, de même, les fils de trame

et

les trajets des fils des nappes suivants C3,...C6 étant obtenus en ajoutant 2 à chaque référence de colonne correspondante précédente, savoir, pour le premier fil de la nappe

etc, ce motif étant agrandissable suivant l'épaisseur du matériau à réaliser, avec un nombre impair de lignes.The subject of the invention is for this purpose a frame of woven threads or fibers formed of weft threads and warp threads, characterized in that its texture is formed by a basic pattern constituted by fifteen weft threads R arranged in staggered rows. forming six vertical columns 1 to 6 of two and three wires alternately and at least five horizontal lines 1 to 5 of three wires each, and by six overlapping plies C1 to C6 of at least two parallel wires or at least twelve wires a, b , c ... l, each connecting one weft thread in three of the same column in two adjacent lines and the warp threads of consecutive plies connecting weft threads in alternating columns, the first yarn a of the first ply C1 connecting the weft thread R of column 2, in row 1, that is

in the weft R of column 5, in row 2, either

, the second yarn b of the first ply C1 connecting the weft yarn R of column 2, in row 3, either

in the weft R of column 5, in row 4, either

the first yarn c of the second ply C2 connecting the weft yarn R of column 1 in row 2, ie

, in the weft thread R of column 4, in row 1, that is R 4; the second yarn d of the second ply C2 likewise connecting the weft yarns

and

the paths of the wires of the following plies C3, ... C6 being obtained by adding 2 to each preceding corresponding column reference, namely, for the first wire of the ply

etc, this pattern being enlargeable according to the thickness of the material to be produced, with an odd number of lines.

FIG. 4 is an example of enlarging the basic pattern, comprising seven lines and three-wire plies.

• La figure 1 est une vue schématique d'une première partie d'un motif de base d'une armature suivant l'invention montrant l'agencement des six fils de chaîne a...f des trois premières nappes C1, C2, C3 par rapport aux fils de trame R.
• La figure 2 est une vue analogue à celle de la figure 1, montrant l'agencement des six fils de chaîne g...l des trois autres nappes C4, C5 et C6 par rapport aux fils de trame du même motif de base.
• la figure 3 est une vue schématique d'un motif de bae complet, obtenue par superposition des figures 1 et 2.
• La figure 4 montre l'agencement réel des fils de chaîne et de trame dans l'armature suivant l'invention, tel qu'il apparait à la micrographie.

The description which follows, with reference to the accompanying drawings by way of nonlimiting examples, will make it possible to understand clearly how the invention can be put into practice.

• Figure 1 is a schematic view of a first part of a basic pattern of a frame according to the invention showing the arrangement of the six warp son a ... f of the first three plies C1, C2, C3 by compared to the weft threads R.
• Figure 2 is a view similar to that of Figure 1, showing the arrangement of the six warp son g ... l of the other three plies C4, C5 and C6 with respect to the weft son of the same basic pattern.
• FIG. 3 is a schematic view of a complete bae pattern, obtained by superposition of FIGS. 1 and 2.
• FIG. 4 shows the actual arrangement of the warp and weft threads in the reinforcement according to the invention, as it appears on the micrograph.

The principle of the 2,5D reinforcement consists in interlacing the warp and weft threads in order to obtain an indelaminable material, without thread perpendicular to the wall.

Figures 1 to 3 show how the warp threads are arranged in relation to "circles" which correspond to the location of the weft threads. It will be noted that these weft threads, or these "circles" are arranged in staggered rows, forming alignments in rows and columns of which one intersection in two comprises a "circle" if each "circle" is given a line number and a column number: R indicates the "circle" of the 2nd column and the 3rd row. It will be noted that the total number of lines depends on the thickness of the material to be produced and that it is odd (here 5) while the number of columns is a multiple of 6, because the rest of the reinforcement is obtained by repeating the previous pattern.

A set of pairs of parallel wires will be called "tablecloth". A complete pattern consists of 6 layers of warp threads, parallel two by two.

These layers will be designated by C1, C2, C3, C4, C5 and C6. (For clarity, the path of these layers has been separated into two figures). FIG. 1 shows the path of the layers C1, C2 and C3, and FIG. 2 shows the path of the layers C4, C5 and C6.

On the pattern shown, the tablecloth has only 2 threads and the number of threads of a tablecloth is equal to half the even number, immediately less than the number of lines.

et au dessous de

The first wire of the C1 ribbon cable passes over

and below

et au-dessous de

The second wire of the ribbon cable C1 passes over

and below

puis de

. Il relie donc un sur trois des fils de la ligne 2.The first thread turns around

then

. It therefore connects one in three of the wires in line 2.

puis de

. Il relie donc un sur trois des fils de trame de la ligne 3 à un sur trois des fils de trame de la ligne 4.The second thread revolves around

then

. It therefore connects one in three of the weft yarns in line 3 to one in three of the weft yarns in line 4.

By adding 2 to the column number of the weft threads, the path of the threads of the sheet C2 is obtained, then by adding 2 again, that of the sheet C3.

When these 3 layers have passed, the weft threads of line 1 are connected to those of line 2 and the weft threads of line 3 to those of line 4.

The layers C4, C5 and C6 (FIG. 2) connect the weft threads of line 2 to those of line 3 and the weft threads of line 4 to those of line 5.

The path of C4 is deduced from that of the water table C1 by adding 1 to the line number and 1 to the number of weft thread column.

The actual presentation of the product obtained is shown in Figure 3. Note the flattened oval shape of the weft threads and the high percentage of the area occupied by filaments; this is favorable to the mechanical strength of the material and facilitates the placement of the binder.

The pattern constituting this reinforcement is the simplest and most logical to obtain a material with interlaced layers.

Each warp thread connects two rows of adjacent wefts. The arrangement of the weft threads (R) in staggered rows is imposed to avoid a vacuum between the warp threads and to minimize the undulations of the warp threads.

In this pattern you need 6 layers of thread to tie the rows of weft threads.

The reinforcements according to the invention can be produced with fibers or threads of any kind (carbon, Kevlar, silica, silicon carbide, Nextel, etc.).

These reinforcements are either made with fibers, or of the same kind, or else by a combination of fibers or threads of different natures. In addition, the sections of the fibers or threads can be identical or of different dimensions and shapes.

Finally, the mesh of the frame can be adapted to the request by provision provided in advance of the "circles" corresponding to the weft threads.

The reinforcement according to the invention can be produced in the form of a plate. However, most of this type of product relates to circular parts of variable shape, and is particularly suitable for thin structures.

Claims (1)

Reinforcement in woven threads or fibers formed of weft threads and warp threads, characterized in that its texture is formed by a basic pattern constituted by fifteen weft threads R arranged in staggered rows forming six vertical columns 1 to 6 of two and three wires alternately and at least five horizontal lines 1 to 5 of three wires each, and by six overlapping plies C1 to C6 of at least two parallel wires or at least twelve wires a, b, c, ... l, each connecting one weft thread on three of the same column in two adjacent lines and the warp threads of the consecutive plies connecting weft threads in alternating columns, the first thread a of the first ply C1 connecting the weft thread R of the column 2, in row 1, that is

, in the weft thread R of column 5 in row 2, that is R, '; the second yarn b of the first ply C1 connecting the weft yarn R of column 2 in row 3, ie

, in the weft R of column 5 in row 4, either

; the first yarn c of the second ply C2 connecting the weft yarn R of column 1 in row 2, ie

, in the weft thread R of column 4, in row 1, that is Ri; the second yarn d of the second ply C2 likewise connecting the weft yarns

and

, the paths of the wires of the following plies C3, ... C6 being obtained by adding 2 to each preceding corresponding column reference, namely, for the first wire of the ply

this pattern being enlargeable according to the thickness of the material to be produced, with an odd number of lines.

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