WO1994020658A1

WO1994020658A1 - Multiaxial three-dimensional fabric and process for its manufacture

Info

Publication number: WO1994020658A1
Application number: PCT/FR1994/000230
Authority: WO
Inventors: Jean-Marc Ruzand; Gérard GUENOT
Original assignee: C.T.M.I. Cotton Textiles Pour Materiaux Innovants
Priority date: 1993-03-03
Filing date: 1994-03-01
Publication date: 1994-09-15
Also published as: EP0687315B1; AU6144794A; FR2702222A1; DE69433132D1; EP0687315A1; FR2702222B1

Abstract

Three-dimensional fabric with oblique reinforcements comprising warp yarns (1), weft yarns (2) and oblique yarns (3a, 3b). The warp yarns (1) form at least two layers and run over different layer planes, with none of these yarns linking the two outermost fabric layers. The weft yarns (2) comprise at least two layers, disposed in superimposed planes, and are interlaced and woven with the warp yarns (1). The oblique yarns (3a, 3b) are disposed in layers of parallel yarns, forming one or more pairs, the directions of each layer of oblique yarns of one pair being symmetrical with one another in relation to the longitudinal fabric direction, and forming a non-right angle in relation to said longitudinal direction. The layers of oblique yarns (3a, 3b) are covered with at least one layer of non-oblique yarns. Application in the production of reinforcing elements for composite materials.

Description

MULTIAXIAL THREE-DIMENSIONAL FABRIC AND

ITS MANUFACTURING PROCESS

The present invention relates to a three-dimensional multiaxial fabric, for technical uses, of a new and advantageous constitution, as well as to a process for its manufacture. This three-dimensional fabric with multiple reinforcement directions, more particularly with oblique reinforcements, is especially intended, in its industrial applications, to constitute the reinforcement of composite materials with high structural characteristics.

The composite materials in question consist of a reinforcement made up of reinforcements and a matrix which coats the reinforcement. The reinforcement is generally based on fibers with high mechanical resistance, such as: glass fibers, carbon, silicon carbide, aramid, etc. The matrix is organic, inorganic or metallic in nature; it is obtained from a binder, such as a resin in the case of an organic matrix, the reinforcement of which is impregnated, a heat treatment producing the polymerization of the resin and obtaining the final, hardened composite material .

These materials are characterized in particular by excellent mechanical resistance properties combined with a low density. Also, these materials are widely used for many applications in which high mechanical strengths are sought: aeronautical and space constructions; transportation industry: automobile, shipbuilding; sport stuff ; competition vehicles and boats; etc ...

Another important advantage of these composite materials lies in the possibility of placing the reinforcements in the directions of the forces to which the structure is subjected, which makes it possible to obtain the maximum resistance and incomparable characteristics. in these directions, and thus the best adaptation of the material to the requested use.

Most of the time, composite materials for structural use are produced with reinforcements in the form of long or continuous oriented fibers, the reinforcements in the form of short or cut fibers, dispersed in the matrix, being generally reserved for uses not requiring very high mechanical resistance. ^* For reinforcement reinforcements with predefined orientation directions, there are different arrangements:

- Axmatures with reinforcements in one direction (also called unidirectional or uniaxial): The reinforcements are arranged in the form of long fibers aligned parallel to each other. It is understood that these frames are mainly reserved for structures subjected to stresses essentially in one direction, and of long shape, that is to say having a small section relative to their length. These unidirectional reinforcements are often used in combination with more complex reinforcements, their use alone being limited by their low mechanical resistance in all directions not parallel to that of the reinforcements, this resistance then being only that of the matrix and of the fiber-bond. matrix which is almost always much lower than the strength of the fibers.

- Reinforcements in two directions, also designated by the abbreviation "2D": For the production of composite materials, these reinforcements are most often in the form of fabrics. To obtain the desired thickness, several layers of fabric are placed on top of each other. The parts thus obtained have very good mechanical characteristics along the two directions of the threads of the fabrics, but for the others directions and in particular in the direction perpendicular to the two previous directions (again the direction of the thickness), as well as for intermediate directions, which will be described as oblique with respect to the two main directions of the fabrics, the mechanical properties are significantly worse. In practice, this can result in "decohesions" or "delaminations" between the layers of tissue, under the action of stresses which do not otherwise reach the "resistance limit of the reinforcing fibers of the fabrics. are therefore not used to the best of their potential properties. On the other hand, the establishment of the superimposed layers of tissue is an operation which is often not very rapid and therefore costly, presenting in addition risks of errors in the quantities and arrangements of the layers, which is detrimental to the quality of the parts produced.

- Three-dimensional reinforcements with reinforcements in three directions, also designated by the abbreviation "3D": To overcome the aforementioned defects, various types of woven reinforcements having reinforcing fibers in the three dimensions of space have been proposed. It may be reinforcements arranged in three perpendicular directions ("3D orthogonal"), of which there are many methods of making, or in axial, radial and circumferential directions ("polar 3D") as described in the French patent N ° 2643657. These reinforcements have excellent characteristics in the three directions of the reinforcements and in particular if a thick piece is made with a fabric of the "3D orthogonal" type, the risks of delamination between different layers of reinforcing threads are very clearly reduced. In addition, insofar as these three-dimensional reinforcements can be produced on a machine automatically, the desired composition of the reinforcing reinforcement is immediately obtained, ready to be impregnated to obtain the part. composite finished. This is a guarantee of better productivity and increased quality in obtaining parts.

However, these types of "3D" reinforcements have the drawback of not easily lending themselves to the production of all the geometries of parts. This is obviously the case for "3D polar" type armatures reserved for forms of revolution. As for reinforcements of the "3D orthogonal" type, their drawback is that they are ill-suited to the production of structures having relatively small thicknesses. It is particularly difficult to shape them to produce parts of curved shape.

Three-dimensional fabrics capable of being shaped, for example by folding, are known and one can here cite, by way of example, the fabric described in French patent No. 2497839. In this case, however, weaving yarns performing the third direction are generally fine binding yarns whose mechanical characteristics are limited.

- Non delaminable three-dimensional reinforcements: Other types of woven reinforcements exist which are not "3D" reinforcements (with three directions) and which however have a good resistance to delamination in the thickness direction. An example of reinforcement of this type is described in French patent No. 2610951. In this type of reinforcement, a three-dimensional fabric is produced comprising several layers of weft yarns and warp yarns, the warp yarns of which run through different planes and are crisscrossed with weft threads of different layers. The warp threads thus arranged provide connections between the different layers materialized by the weft threads. An indelaminable structure is thus obtained as a "3D" structure without fibers which pass through the thickness of the fabric. This frame can be considered as an intermediary between a "2D" frame and a "3D" frame, hence the name "2.5D" given to this frame. This type of frame is well suited to the manufacture of thin parts. However, if the "3D" and "2.5D" reinforcements described above generally have good mechanical characteristics along the directions of the reinforcing fibers and good delamination resistance properties, they may have insufficient characteristics for certain cases of stress. by efforts encountered on structures in service. Thus, for example, in the case of a plate-type structure which is subjected to twisting or warping stresses, that is to say forces inducing a torsional torque of the plate which tends to rotate the two opposite ends of the plate around an axis perpendicular to these two ends in opposite directions, conventional “3D” or “2.5D” type reinforcements as described above may have insufficient strengths and stiffnesses in the directions in which torsional stresses are exerted. It is then necessary to have a reinforcement having more than three reinforcing directions and in particular having reinforcing fibers in directions inclined with respect to the longitudinal direction of the reinforcement (oblique reinforcements), and symmetrical with respect to this direction. longitudinal. This gives a five-directional frame, also called "5D".

European patent No. 0426878 (or the corresponding international patent application No. WO 90/14454) describes a three-dimensional fabric which essentially consists of a reinforcement of the "orthogonal 3D" type, further comprising threads arranged obliquely in symmetrical directions. This three-dimensional fabric comprises threads which extend in the vertical direction, that is to say in the direction of the thickness of the fabric, in thus connecting the two extreme layers of the fabric; 1'endo magement of these "vertical" threads thus causes delamination of the fabric, which loses its cohesion and its mechanical strength. As will appear below, this fundamentally distinguishes the aforementioned document from the subject of the present invention.

There are also other more complex types of reinforcement: "4D", "5D" or more ("9D", "11D"). They have excellent qualities, but are practically ^" always intended for very specific uses and most often require special machines for each model of structure to be produced.

The object of the present invention is to provide a new three-dimensional fabric composed of a three-dimensional base frame which is indelaminable of an intermediate nature between a "2D" frame and a "3D" frame, and groups of so-called oblique reinforcing threads arranged in accordance with directions forming various non-right angles, with the longitudinal direction of the fabric, the groups of oblique threads and the basic reinforcement forming an inseparable whole, this three-dimensional fabric making it possible to produce reinforcements having increased resistance to 'efforts of various orientations. Another objective of the invention is to propose an industrial process for the manufacture of this three-dimensional fabric which allows an automated and reproducible production in great lengths.

To this end, the multiaxial three-dimensional fabric with oblique reinforcements according to the present invention consists of:

warp threads which extend in a direction of the so-called longitudinal fabric,

- weft threads which extend in a direction of the so-called transverse fabric, in particular in a direction perpendicular to the direction of the warp threads. warp threads comprising at least two layers of warp threads and constituting a network of threads running on planes of different layers, while weft threads, also comprising at least two layers, are arranged in several planes superimposed in the direction of the thickness of the fabric so that a three-dimensional multi-layer fabric is obtained, in which the warp threads are interlaced and woven with weft threads of different planes, without any "of these warp threads connects two extreme layers of the fabric, and

- so-called oblique wires arranged in layers of wires parallel to each other, forming one or more pairs of layers of oblique wires, the directions of each layer of oblique wires of a pair being preferably symmetrical with respect to each other in the longitudinal direction of the fabric and forming a non-right angle with the abovementioned longitudinal direction, the sheets of oblique threads being arranged so as to be covered by at least one layer of non-oblique threads, that is to say warp and / or weft.

In one embodiment of the invention, the three-dimensional multiaxial fabric comprises oblique threads arranged in two pairs or groups of pairs of symmetrical plies of oblique threads, at least one pair of plies being disposed on the side of an external face of the fabric , and at least one other pair of plies being disposed on the side of the opposite external face of the fabric, the plies of oblique threads disposed respectively on the two sides of the fabric being covered, each, by an outer layer of weft threads.

The weaving of warp threads and weft threads, both present in several layers, can be carried out according to any weave, always retaining the essential characteristic of the invention that none of the warp threads connects the two extreme layers of the fabric, so that in the event of local surface damage, the fabric retains its cohesion and mechanical strength. In the same vein, the structure of the three-dimensional fabric according to the invention also proves to be advantageous compared to known ultiaxial fabrics comprising plies of oblique threads, but using binding threads which constitute points of weakness.

According to another aspect of the invention, the three-dimensional multiaxial fabric object of the invention advantageously comprises oblique threads arranged in symmetrical layers whose directions form an angle of + 45 ° and symmetrically of -45 °, with the longitudinal direction fabric. Weft threads, warp threads and oblique threads can be based on carbon fibers, glass, silicon carbide, silica, quartz, boron or ceramic, or other fibers of mineral nature , natural or synthetic organic fibers such as aramid fibers, metallic fibers or threads, said warp, weft and oblique threads being made up of fibers of the same kind and of the same fibers or of combinations of fibers of different natures or of fibers different or a combination of these two possibilities.

According to yet another aspect of the invention, this three-dimensional multiaxial fabric makes it possible to constitute a textile article of shape comprising one or more webs and wings or ribs, the number of warp threads in each layer as well as the number and the length of the weft threads being adapted as a function of the effective section to be given to the fabric at a given level.

The method according to the invention, for the manufacture of the three-dimensional multiaxial fabric defined above, in which the warp threads for all the layers of the fabric form several plies arranged in a longitudinal direction and woven with the weft threads, provides that the oblique threads constituting the pair or pairs of upper plies of oblique threads are arranged to reach the warp threads above them and in front of the frames stringers in the crowd formation zone, and that the oblique threads constituting the pair or pairs of lower layers of oblique threads are arranged to reach the warp threads from below them and in front of the heald frames in the crowd training area. The oblique threads of each of the upper plies of oblique threads are engaged in upper pass bars, the number of which is equal to the number of upper plies of oblique threads, disposed above the warp threads and in front of the heald frames. . These guide bars can take an active position, lowered, or an inactive position, raised. The oblique threads of each of the lower plies of oblique threads are engaged in lower pass bars, the number of which is equal to the number of lower plies of oblique threads, arranged below the warp threads and in front of the heald frames. . These guide bars can take an active, raised position, or a lowered inactive position. Each of the aforementioned upper or lower guide bars can move in a direction perpendicular to the longitudinal direction of the fabric and parallel to the transverse direction of the fabric, the procedure being more particularly as follows: - In a first step, the crowd being formed for weaving the upper outer layer, the upper pass bars are moved one step in the transverse direction of the fabric, in one direction for the pass bars of the upper layers of oblique yarns of an orientation and in the opposite direction for pass bars of the upper layers of oblique threads of the other orientation, then lowered into the active position so that the lower plies of oblique threads are substantially at the level of the warp threads.

- In a second step, a weft thread is inserted so that the oblique threads of the upper plies are located between this weft thread and the non-lifted warp threads.

- In a third step, the upper guide bars are raised to the inactive position so as to ^" bring the oblique wires out of the crowd.

- In a fourth step, the comb is struck.

- In a fifth step, the weft threads of the internal layers of the three-dimensional fabric are inserted successively.

- In a sixth step, when the weaving operation reaches the lower outer layer and the shed is formed for this operation, before the passage of the pick, the lower guide bars are moved by one step along the transverse direction of the fabric, in one direction for the pass bars of the lower layers of oblique threads of one orientation and in the opposite direction for the pass bars of the lower layers of oblique threads of the other orientation, then raised in the active position so as to that the lower layers of oblique threads are substantially at the level of the warp threads raised to form the crowd.

- In a seventh step, a weft thread is inserted so that the oblique threads of the lower symmetrical plies are located between this weft thread and the group of raised warp threads.

- In an eighth step, the lower guide bars are lowered to the inactive position so as to bring the oblique threads out of the crowd. - In a ninth stage, the comb is struck. When the ninth step is completed, we return to the configuration of the first step and the operations from the first to the ninth step are repeated identically and this as many times as necessary to obtain the desired length of three-dimensional fabric.

According to an embodiment of the method according to the invention for manufacturing a three-dimensional multiaxial fabric, use is made of guide bars for the oblique threads produced in several parts, which comprise the same number of oblique threads engaged. The number of oblique threads of a tablecloth necessary to cover the width of the three-dimensional fabric is ensured by the number of parts of a pass bar reduced by one, and the total number of oblique threads engaged in a pass bar for a tablecloth exceeds the number of threads required for the width of the fabric by the amount of threads mounted on a part of a pass-bar. When a pass-bar, following the transverse shifting movement, extends beyond one side of the lateral end of the fabric by a distance equal to the dimension of a part of pass-bar, this part is moved to the end opposite of the guide bar, the oblique threads engaged on this part being cut at their exit from the fabric, the ends of the threads engaged in the passers being held in place. Thus, by way of example, the guide bars can be produced in two parts, the total number of oblique threads of a sheet being, in this case, twice the number of threads necessary to cover the width of the three-dimensional fabric.

In any case, the invention will be better understood with the aid of the description which follows, with reference to the appended diagrammatic drawing representing, by way of nonlimiting examples, some embodiments of this three-dimensional multiaxial fabric, and illustrating its process of manufacturing as well as the means of implementing this process:

Figure 1 is a plan view from above of a three-dimensional multiaxial fabric according to the present invention, with oblique threads oriented at 45 °;

Figure 2 is a longitudinal sectional view of the same three-dimensional fabric, along line A-A of figure

1;

Figure 3 is a very schematic view, in side elevation, of a loom suitable for manufacturing the three-dimensional fabric shown in Figures 1 and 2;

Figure 4 is a front view of the loom of Figure 3; Figures 5 to 13 are diagrams illustrating the successive operations of weaving the three-dimensional fabric concerned, on this loom;

Figures 14 to 17 are other diagrams, which illustrate the permutation of a set of two half-pass bars;

Figure 18 is a schematic side elevational view of a three-dimensional fabric loom having a layer of oblique threads on one side;

Figure 19 is a plan view of a three-dimensional multiaxial fabric according to the invention with oblique threads oriented at angles other than 45 degrees;

Figure 20 is a perspective view of a three-dimensional fabric in the shape of "C"; Figure 21 is a perspective view of a three-dimensional fabric in the shape of "U";

Figures 22,23 and 24 are perspective views, very schematic, of other forms of three-dimensional fabrics according to the invention. A nonlimiting example of the constitution of a three-dimensional multiaxial fabric according to the invention is represented by FIGS. 1 and 2. The three-dimensional fabric which is seen in plan in FIG. 1 consists of warp threads 1 which are arranged in a so-called longitudinal direction of the three-dimensional fabric, of weft threads 2 arranged in a so-called transverse direction three-dimensional fabric, this direction being perpendicular to the longitudinal direction, and oblique threads 3a, 3b, 3c, 3d. The oblique threads here form four layers. Are visible in Figure l, the sheet formed by the oblique son 3a parallel and the sheet formed by the oblique son 3b parallel. The two plies of oblique threads 3a, 3b are symmetrical with respect to the longitudinal direction of the fabric and form an angle of 45 degrees with this direction. These two plies of oblique threads 3a, 3b are arranged on the side of the upper face of the fabric, while the other two plies of oblique threads 3c, 3d are arranged on the side of the lower face of the fabric. Assuming that FIG. 1 is a plan view of the fabric from above, the plies of oblique threads 3c, 3d situated on the side of the lower face cannot be seen, but, if a plan view from below is shown fabric, the lower oblique plies of yarn would appear in exactly the same way as shown in FIG. 1 for the upper plies.

The weft threads 2 are arranged in several superimposed planes in the thickness direction of the fabric, so as to obtain a three-dimensional fabric. The warp threads 1 are intertwined with weft threads 2 located in different planes and thus run in the thickness direction of the three-dimensional fabric. FIG. 2 shows the arrangement of the various warp 1, weft 2, and oblique 3a, 3b, 3c, 3d wires in the thickness of the fabric. We note in particular that the warp threads 1 connect different weft son planes 2 but without completely crossing the thickness of the fabric, that is to say that the weft son layers 2 of the upper and lower end faces of the fabric are not directly connected by the same warp thread. The base fabric produced by the warp and weft threads thus constitutes an intermediate reinforcement between a "2D" reinforcement and a "3D" reinforcement.

In FIGS. 1 and 2, the constituent threads of the fabric are shown in the form of threads of round and solid section, this to facilitate understanding of the geometry of the structure of the fabric. In reality, the threads are almost never massive, but consist of a multitude of filaments. The section of these threads varies according to the locations of the fabric and the actual product has a density of threads greater than what FIGS. 1 and 2 show.

The oblique threads 3a, 3b, 3c, 3d which are shown seen in section in FIG. 2 constitute two symmetrical plies on the side of the upper face of the three-dimensional fabric (threads 3a, 3b) and two other symmetrical plies on the side of the lower face of said tissue (yarns 3c, 3d).

The upper oblique threads 3a and 3b are covered by the weft threads 2 of the upper plane, and are thus located between the aforementioned weft threads and the other weft threads and warp threads of the three-dimensional fabric.

The lower oblique threads 3c and 3d are located between the weft threads 2 of the lower plane which are then below the threads 3c, 3d, and the other weft threads and warp threads of the three-dimensional fabric.

Figures 1 and 2 show the basic pattern of the weave of the fabric. In reality this pattern will be repeated both in the longitudinal direction (warp direction) and in the transverse direction (width or weft direction), depending on the dimensions of the fabric. More particularly, the weaving of warp threads 1 and weft threads 2 is here defined on 12 rows of warp threads and 12 rows of weft threads and constitutes a twill weave of 2 ties 1. This type of weave is given by way of example and the three-dimensional fabric can be produced from other types of weave of different ratios without departing from the scope of the invention.

By using a weave pattern for weaving the warp and weft threads of square ratio, as is the case for the example of FIGS. 1 and 2, and by weaving with identical threads in weft, warp and obliques or, at least, having the same size, we obtain a three-dimensional fabric comprising oblique threads arranged in symmetrical layers forming angles of 45 degrees with the longitudinal direction of the fabric (which corresponds to the general direction of warp threads 1).

We understand that by using a non-square ratio weave design, or by using threads of different dimensions for the weft, warp and oblique threads, or even by combining these two arrangements, we can obtain, without going out of the framework of the invention, a three-dimensional fabric comprising oblique threads forming angles different from 45 degrees with the longitudinal direction. An example of such a fabric is shown in Figure 19, where the angle is about 30 degrees.

A method for manufacturing a three-dimensional fabric according to the invention is described below, with reference to Figures 3 and following. Figures 3 and 4 show schematically the structure of a loom for weaving a three-dimensional fabric according to the invention.

The warp threads 1 which form superimposed plies 4 come from wire feeders 8 which consist either of beams or of cantres. These devices which are analogous to those commonly used are not detailed here. The oblique wires 3a, 3b, 3c, 3d are supplied by similar devices 9a, 9b, 9c, 9d. The mechanical tension of the warp threads and the oblique threads is adjusted by regulating systems (not shown) produced by any known apparatus.

The warp threads 1 coming from the feed devices 8 then pass between guide bars or rollers 10, then are engaged in the healds of heald frames 5. The number of heald frames 5, the number of healds and l 'arrangement of warp threads 1 in the heddles are determined by the weave to be obtained and the dimensions of the fabric to be produced as any person skilled in the art knows how to do. In Figure 3, one of the frames 5 is shown in the raised position, showing the crowd thus formed.

A lance 11 inserts the weft 2 into the crowd. The lance 11 can be replaced by any other known device ensuring the same function.

The oblique threads 3a, 3b of the upper layers arrive at the height of the warp threads 1 from above and in front of the heald frames 5 (to the left of these in FIG. 3) in the crowd formation zone . The oblique wires 3a, 3b are engaged, for each of them, in the eye of a passette. The passettes are mounted on upper pass bars 6a, 6b at the rate of one bar per sheet of oblique wires. The passettes can take an active position in which the threads and the threads which are introduced therein are at the height of the plies of warp threads in the formation zone of the crowd, and an inactive position in which the threads and the threads introduced therein find distant above the warp threads and out of the crowd. To this end, the bars supporting the passettes are mobile, in particular, being able to pivot around a transverse axis perpendicular to the passettes. In the lowered position, the strainers are active; in the raised position they are inactive. The movement of the guide bars can be obtained by any other means, for example by sliding in a vertical plane. In FIG. 3, the upper guide bars 6a, 6b are shown in the active (lowered) position.

Similarly, the oblique threads 3c, 3d of the lower layers arrive at the height of the warp threads 1 from below and in front of the heald frames 5, in the crowd formation zone. The oblique wires 3c, 3d are engaged, for each of them, in the eye of a passette. The passettes are mounted on lower pass bars 6c, 6d, at the rate of one bar per sheet of oblique wires. The passettes can take an active position in which the eye and the threads which are introduced therein are at the height of the plies 4 of warp son in the area of formation of the crowd, and an inactive position in which the eye and the introduced threads are located far below the warp threads and outside the crowd. For this, the lower pass bars 6c, 6d are movable like the upper pass bars 6a, 6b. Thus, with swivel bars 6c, 6d, in the raised position, the passettes are active and in the lowered position, they are inactive. In FIG. 3, the lower guide bars 6c, 6d are shown inactive (lowered position).

Each of the upper or lower guide bars 6a, 6b, 6c, 6d, can move in a direction perpendicular to the longitudinal direction of the fabric and parallel to its transverse direction. The movements are made step by step from left to right or from right to left when we look at the loom from the front (Figure 4), the direction of movement depends on each guide bar. The pass bars are made in two or more parts which are generally integral, but which can be separated and moved for certain weaving operations, as described in detail below. A comb 7 is arranged between the frames 5 and the guide bars 6a, 6b, 6c, 6d. The comb 7 can be animated by a movement towards the front of the fabric (either from right to left in FIG. 3) to effect the tightening of the fabric. 'The finished three-dimensional fabric is extracted from the front of the loom (that is to the left in Figure 3) using known devices used in traditional looms.

In FIGS. 3 and 4 the loom is shown with the warp threads 1 in substantially horizontal planes and consequently with vertical heald frames 5. While retaining the same functions, the loom can also be designed with the warp threads in vertical planes and the horizontal heald frames, without departing from the scope of the invention. In this design the oblique threads will arrive horizontally in the weaving area.

The course of the current operations of weaving a three-dimensional fabric, with the loom described above, is described below. The operations described make it possible to produce a three-dimensional fabric such as that described above and illustrated by FIGS. 1 and 2.

At the start, all warp, weft and oblique threads are assumed to be mounted on the loom. In a first step, the crowd is formed for the weaving of the upper outer layer. For this, the first heald frame 5 is lifted and with it are lifted all the warp threads 1 which correspond to the leftmost warp thread in FIG. 1 representing the fabric seen in plan (the weave pattern shown is repeated a number of times across the width of the fabric in depending on the expected size of the fabric). The upper guide bars 6a, 6b which are then in the inactive position (raised) are moved one step in the transverse direction of the fabric. In the example considered, this step is equivalent to the size of four warp threads. The guide bar 6a is moved one step from left to right (with reference to Figures 1 and 4). The bar 6b is moved one step from right to left, this in order to obtain the plies of oblique son 3a and 3b symmetrical. The two guide bars 6a, 6b are then lowered to come into active position and bring the oblique threads 3a, 3b substantially at the level of the warp threads 1 not lifted. This configuration is illustrated in Figure 5. In a second step shown in the figure

6, one. weft thread 2 is passed through the crowd by the movement of the lance 11. This thread corresponds to thread 2 at the bottom of FIG. 1. The passage of the weft thread 2 is done so as to cover the oblique threads 3a, 3b. The oblique threads 3a, 3b are thus located between the weft thread 2 and the warp threads ^• 1 not lifted, as can be seen in FIG. 1.

In a third step, illustrated by the figure

7, the guide bars 6a, 6b are raised to come to the inactive position, so as to bring the oblique wires

3a, 3b outside the crowd.

In a fourth step, illustrated by the figure

8, the comb 7 is struck, which ensures the establishment and tightening in the fabric of the weft 2 and oblique threads 3a, 3b. The guide bars 6a, 6b having been raised during the previous step, the movement of the comb 7 can be carried out without hindrance.

During a fifth step, represented by FIG. 9, the internal layers are woven which constitute the part of three-dimensional fabric of intermediate structure between a "2D" and a "3D" type. In this step, only warp 1 and weft 2 threads are used.

Thus at the start of this step, the first heald frame 5 remains raised and the second, fifth and ninth frames are lifted, these frames respectively corresponding to the second, fifth and ninth warp threads 1 seen from the left in FIG. 1 The second weft thread 2 of the operation described here is then inserted by actuating the lance 11. This thread corresponds to the second weft thread 2 seen from the bottom in FIG. 1; it passes under the first, second, fifth and ninth warp threads 1, under the upper oblique threads 3a, 3b and on the other warp threads 1 and lower oblique threads 3c, 3d. The comb 7 is actuated at this time to tighten the weft thread 2 which has just been inserted. Then the necessary movement of the heddle frames 5 is carried out for the weaving of the third layer. These maneuvers, being conventional weaving operations, are not repeated in detail here. In a sixth step, the crowd is formed for weaving the lower outer layer. In the example of the fabric of FIG. 1, all the heald frames 5 are lifted except for the fourth, which corresponds to the fourth warp thread 1 counted from the left in FIG. 1 which remains the only thread chain not lifted. The lower guide bars 6c, 6d which are then in the inactive position (lowered) are moved one step in the transverse direction of the fabric. This step has the same value as that used to move the upper guide bars 6a, 6b. The guide bar 6c is moved one step from left to right. The guide bar 6d is moved one step from right to left, this in order to obtain the plies of oblique son 3c, 3d symmetrical. The two guide bars 6c, 6d are then raised to come into the active position and bring the oblique wires 3a, 3b inside the crowd substantially at the level of the wires chain lifted to form the crowd. This situation is illustrated in FIG. 10. To simplify the diagrams, the guide bars 6c and 6d are not shown in FIGS. 5 to 9 where they are not in operation.

During a seventh step, shown in FIG. 11, a weft thread 2 is inserted by actuating the lance 11 so that the oblique threads 3c, 3d are located between the aforementioned weft thread and the group of threads of chain 1 lifted. The weft thread 2 in question thus passes below the oblique threads 3c, 3d. In FIG. 1, this weft thread corresponds to the fourth thread 2 from the bottom of the drawing.

In an eighth step, illustrated by FIG. 12, the guide bars 6c, 6d are lowered to come to the inactive position, so as to bring the oblique wires 3c, 3d out of the crowd.

In a ninth step, illustrated by FIG. 13, the comb 7 is struck in a manner analogous to the operation of the fourth step.

When the ninth step is completed, we return to the configuration of the first step and the operations from the first to the ninth step described above will be repeated identically to proceed with the complete weaving of the three-dimensional fabric.

All the operations described above can be carried out automatically; the method described allows the production of a three-dimensional fabric. in great length and with the inherent desired quality, in the repeatability of the process.

The orders for lifting the heald frames and other operations described above correspond to the definition of the fabric shown in FIG. 1 and are given by way of non-limiting example. The movement sequences of the heddle frames and frame passage may be different to correspond to any type of armor used in accordance with the invention. These sequences can be determined by methods known to those skilled in the art without departing from the scope of the invention. During the weaving operations as described above and their repetition, each guide bar 6a, 6b, 6c or 6d is driven in a transverse shift movement step by step, either from left to right, either from right to left, but always in the same direction for a given pass bar. If we use guide bars before a number of oblique threads for a tablecloth just equal to the number of oblique threads of this tablecloth that we meet across the width of the three-dimensional fabric, after each shift of the bars a growing part of the surface of the fabric will no longer be covered by oblique threads. Ultimately, if the guide bars are offset by a number of steps equal to the number of oblique threads of a web crossed over a width of the fabric there will no longer be oblique threads in the three-dimensional fabric.

It is to remedy this problem that, in accordance with a characteristic of the invention, the guide bars are produced in several parts and have a number of oblique threads engaged greater than the number of oblique threads of a sheet which are found on a three-dimensional fabric width.

The simplest arrangement is to make each pass bar in two equal parts. So that the oblique threads always cover the three-dimensional fabric, it is necessary that, when one half (or a part) of the pass bar is entirely offset outside the fabric, to the left or to the right depending on the pass bar considered, the other half of the pass bar still completely covers the fabric. The number of oblique threads engaged in the entire guide bar must therefore be double the number of oblique threads necessary to cover the width of the three-dimensional fabric, which is also the number of oblique threads of a tablecloth encountered on the width of the fabric.

Each guide bar can also be produced in three equal parts, this remaining within the scope of the invention. In this case, when a third (part) of the pass bar is offset outside the fabric, the other two thirds (or the other two parts) of the pass bar should completely cover the fabric. The number of oblique threads engaged in the entire guide bar must then be equal to one and a half times the number of oblique threads of a tablecloth necessary to cover the width of the fabric, or even in other words, equal to 3 / 2 of the latter number. The guide bars can also be made in four equal parts; the number of oblique threads engaged in an entire guide bar will then be equal to 4/3 of the number of oblique threads of a tablecloth necessary to cover the width of the fabric. More generally and without departing from the scope of the invention, the guide bars may, for each of them, be produced in n equal parts, each part comprising the same number of oblique wires (an embodiment in unequal parts not presenting 'practical interest). The number n will be at least equal to 2 and at most equal to N + 1, N being the number of oblique threads of a tablecloth encountered on a width of fabric. The number of oblique threads of a tablecloth necessary to cover the width of the three-dimensional fabric will be equal to the number of oblique threads engaged on n-1 parts of the guide bar. In general, the number of oblique threads engaged in an entire guide bar is equal to the number of oblique threads of a sheet necessary to cover the width of the three-dimensional fabric multiplied by the ratio n / (nl). The operation of a multi-part pass bar is described below taking the case of a two-part pass bar illustrated in FIGS. 14 to 17. The two parts 6al and 6a2 of a pass bar are normally joined to each other during weaving operations. As a result of the transverse movement step by step, the guide bar is at a point in the situation shown in Figure 14. The part 6a2 is located completely outside the fabric. This part is then separated from the other part 6al of the pass bar, the oblique threads engaged in this part 6a2 are cut at their exit from the three-dimensional fabric and remain in place in the passers of the bar part 6a2 as illustrated. in Figure 15. Part 6a2 is then moved to the left (see Figure 16). To allow the concomitant movement of the oblique threads engaged on the part of the pass-bar 6a2, the oblique threads 3a of a pass-bar are supplied on two different planes as can be seen in FIG. 3, each plane comprising the oblique threads a part of a pass bar 6al or 6a2. The part 6a2 of the guide bar is finally secured again with the part 6al as shown in FIG. 17, but the part 6a2 is now at the left of the part 6al and no longer on its right as at the beginning of the operation.

The shifting movement of the guide bar will then continue in the same direction (from left to right in the example) and the 6al part will gradually overflow from the fabric, but there will always be the desired amount of oblique threads on the fabric, part 6a2 taking over. When the part 6al is completely out of the fabric, it will in turn be brought back to the opposite end of the guide bar in the same way as it was done for the part 6a2. We will thus find the initial situation, the cycle described above repeating itself.

For a pass bar made of more than two parts, operations analogous to those described above will be performed each time a part of the pass bar is found outside the fabric.

Another example of the type of multiaxial three-dimensional fabric and of the process for its manufacture in accordance with the invention, is illustrated in FIG. 18. The loom ^" shown in FIG. 18 is arranged to manufacture a three-dimensional fabric comprising two symmetrical layers of oblique threads on the side of a single face. Leaving aside the pair of plies of oblique threads on one face, this kind of three-dimensional fabric has a structure similar to that of the three-dimensional fabric of the first example defined by FIGS. 1 and 2.

As for the loom of FIG. 18, its design is very close to that of the loom described above. The main difference is that on the loom of FIG. 18, only the devices necessary for weaving the upper oblique threads 3a, 3b, namely the feeding devices 9a, 9b, the guide bars 6a, 6b, etc. . Likewise, its operation is deduced simply from that of the previous craft by eliminating the steps relating to the lower oblique wires, and it is not repeated in detail here.

FIG. 20 represents a three-dimensional fabric according to the invention produced in the shape of a "C". This shaped fabric has two wings and a core. The wings consist of plies of oblique threads on their external faces and a weaving of warp 1 and weft 2 threads according to the invention in the thickness of the wings, the number of warp and weft threads being adjusted. depending on the desired thickness of the wings. The core which connects the two wings is produced by weaving warp 1 and weft 2 yarns according to the invention. This genre shaped fabric can be made simply on a loom such as that described above, shown in Figures 3 and 4. It suffices to reduce the number of warp threads 1 in the area between the two wings and not to keep in this area as the warp threads needed to make the core.

A three-dimensional fabric having substantially the same external shape, here designated as a "U", can also be produced, while remaining within the scope of the invention, according to FIG. 21. The core consists of plies of oblique threads 3a, 3b on its external face (which in FIG. 21 is shown on the upper face as it would come out of the loom) and a weaving of warp 1 and weft 2 threads according to the invention in the thickness of soul. The wings are produced by weaving warp 1 and weft threads 2 in accordance with the invention. This type of shaped fabric can be produced on a loom such as that shown in FIG. 18. The number of warp threads 1 will be reduced by eliminating the warp threads in the recessed area between the two wings and below the soul.

Preferably, the loom is equipped with two lances, or equivalent weft passage devices, symmetrical, in order to insert weft yarns 2 independent in the wings. The movement of one of the two lances is adjustable so that it ensures the passage of the weft threads over the entire width of the core in the area of the weaving thereof.

Other fabrics of various shapes can be produced in a similar manner without departing from the scope of the invention. Nonlimiting examples of shapes that can be obtained (I, T, etc.) are indicated in FIGS. 22, 23 and 24. In general, the three-dimensional fabric according to the invention makes it possible to constitute a textile article of shape comprising one or more webs and wings or ribs, the number of warp threads in each sheet as well as the number and the length of the weft threads being adapted as a function of the effective section of fabric at a given level.

The three-dimensional fabric which is the subject of the present invention is more particularly intended to constitute the reinforcements of composite parts for structural use. To produce the finished composite material, the fabric constituting the reinforcement is impregnated and densified by substances forming the matrix (organic resins, carbon, ceramics, metals) according to known methods not detailed here.

This three-dimensional fabric can be made from fibers or yarns of any kind, but will advantageously be made from high performance fibers such as: carbon, aramid, glass, silicon carbide, ceramic known under the name Nextel (registered trademark) , etc. , the fibers used being of the same nature or of different natures, the yarns and fibers being able to have identical or different titles, dimensions, textures.

Compared to existing three-dimensional fabrics, the three-dimensional fabric that is the subject of the invention, by virtue of its greater number of reinforcement directions, makes it possible to produce parts of various shapes and dimensions, having increased resistance to multiple orientation forces. In addition, thanks to the mechanized manufacturing processes described, such a fabric can be obtained in significant lengths under good conditions of productivity and reproducibility.

Claims

1. Multiaxial three-dimensional fabric with oblique reinforcements, characterized in that it consists of:

warp threads (1) which extend in a so-called longitudinal direction of the fabric,

- weft threads (2) which extend in a so-called transverse direction of the fabric, in particular in a direction perpendicular to the direction of the warp threads (1), the warp threads (1) comprising at least two layers of threads warp and constituting a network of threads running on planes of different layers, while the weft threads (2), also comprising at least two layers, are arranged in several planes superimposed in the direction of the thickness of the fabric so that a three-dimensional multi-layer fabric is obtained, in which the warp threads (1) are interlaced and woven with weft threads (2) of different planes, without any of these warp threads (1) connects two extreme layers of the fabric, and

- so-called oblique wires (3a, 3b, 3c, 3d) arranged in layers of wires parallel to each other, forming one or more pairs of layers of oblique wires, the directions of each layer of oblique wires of a pair being preferably symmetrical one from the other with respect to the longitudinal direction of the fabric and forming a non-right angle with the abovementioned longitudinal direction, the plies of oblique threads (3a, 3b, 3c, 3d) being arranged so as to be covered by at minus a layer of non-oblique threads, that is to say warp (1) and / or weft (2) threads.

2. Three-dimensional multiaxial fabric according to claim 1, characterized in that it comprises oblique threads arranged in two pairs or groups of pairs of symmetrical plies of oblique threads, at least one pair of plies of oblique threads (3a, 3b) being arranged on the side of an external face of the fabric, and at least one other pair of plies of oblique threads (3c, 3d) being disposed on the side of the opposite external face of the fabric, the plies of oblique threads (3a, 3b, 3c, 3d) disposed respectively on the two sides of the fabric being covered, each one, by an external layer of weft threads (2).

3. Multiaxial three-dimensional fabric according to claim 1 or 2, characterized in that it comprises oblique threads (3a, 3b, 3c, 3d) arranged in symmetrical layers ^" whose directions form an angle of + 45 ° and symmetrically of - 45 °, with the longitudinal direction of the fabric.

4. Three-dimensional multiaxial fabric according to any one of claims 1 to 3, characterized in that the warp threads (1), the weft threads (2) and the oblique threads (3a, 3b, 3c, 3d) are at based on carbon fibers, glass, silicon carbide, silica, quartz, boron, ceramic, or other fibers of a mineral nature, natural or synthetic organic fibers such as aramid fibers, fibers or yarns metallic, said warp, weft and oblique threads being made up of fibers of the same kind and of the same titles or of association of fibers of different natures or of different titles or of the combination of these two possibilities.

5. Three-dimensional multiaxial fabric according to any one of claims 1 to 4, characterized in that it constitutes a textile article of shape comprising one or more webs and wings or ribs, the number of warp threads (1) in each layer as well as the number and the length of the weft threads (2) being adapted as a function of the effective section of the fabric at a given level.

6. Method for manufacturing a multiaxial three-dimensional fabric according to claim 2, in which the warp threads (1) for all the layers of the fabric form several plies (4) arranged as follows a longitudinal direction and woven with the weft threads (2), characterized in that the oblique threads (3a, 3b) constituting the pair or pairs of upper plies of oblique threads are arranged to reach the warp threads (1) by the top of these and in front of heald frames (5) in the crowd formation zone, in that the oblique wires (3c, 3d) constituting the pair or pairs of lower layers of oblique wires are arranged to reach the warp threads (1) from below them and at the front of the heddle frames (5) in the crowd formation zone, in that the oblique threads (3a, 3b) of each of the upper plies of oblique threads are engaged in upper pass bars (6a, 6b) the number of which is equal to the number of upper plies of oblique threads, arranged above warp threads (1) and at the front of the heald frames (5), these guide bars (6a, 6b) can take an ac position tive, lowered, or an inactive position, raised, in that the oblique threads (3c, 3d) of each of the lower layers of oblique threads are engaged in guide bars (6c, 6d) the number of which is equal to the number of lower layers of the oblique threads, arranged below the warp threads (1) and at the front of the heald frames (5), these guide bars (6c, 6d) can take an active, raised position or a position inactive lowered, each of the aforementioned guide bars (6a, 6b, 6c, 6d) being movable in a direction perpendicular to the longitudinal direction of the fabric and parallel to the transverse direction of the fabric.

7. A method of manufacturing a three-dimensional multiaxial fabric according to claim 6, characterized in that:

- in a first step, the shed being formed for weaving the upper outer layer, the upper pass bars (6a, 6b) are moved one step in the transverse direction of the fabric, in one direction for the guide bars (6a) of the upper plies of oblique threads (3a) of one orientation and in the opposite direction for the guide bars (6b) of the upper plies of oblique threads (3b) of the other orientation, then lowered in the active position so that the lower plies of oblique threads are substantially level with the warp threads (1),

- in a second step, a weft thread (2) is inserted so that the oblique threads (3a, 3b) of the upper plies are located between this weft thread (2) and the warp threads (1) not raised,

- in a third step, the upper guide bars (6a, 6b) are raised to the inactive position so as to bring the oblique wires (3a, 3b) out of the crowd,

- in a fourth step, the comb (7) is struck,

- in a fifth step, the weft threads (2) of the internal layers of the three-dimensional fabric are woven successively,

- in a sixth step, when the weaving operation reaches the lower outer layer and the shed is formed for this operation, before the passage of the pick, the lower pass bars (6c, 6d) are moved one step in the transverse direction of the fabric, in one direction for the pass bars (6c) of the lower plies of oblique threads (3c) of an orientation and in the opposite direction for the pass bars (6d) of the lower plies of oblique threads (3d) of the other orientation, then raised in the active position so that the lower plies of oblique threads (3c, 3d) are substantially at the level of the warp threads (1) raised to form the crowd,

- in a seventh step, a weft thread (2) is inserted so that the oblique threads (3c, 3d) of the symmetrical lower layers are located between this weft thread (2) and the group of raised warp threads (1),

- in an eighth step, the lower guide bars (6c, 6d) are lowered to the inactive position so as to bring the oblique wires (3c, 3d) out of the crowd,

in a ninth step, the comb (7) is struck, the completion of the ninth step bringing back to the "configuration of the first step, and the aforementioned operations from the first to the ninth step being repeated identically and as many times as necessary to obtain the desired length of three-dimensional fabric.

8. A method of manufacturing a three-dimensional multiaxial fabric according to claim 6 or 7, characterized in that using guide bars (6a, 6b, 6c, 6d) for the oblique threads (3a, 3b, 3c, 3d ) which are produced in several parts (6al, 6a2), which comprise the same number of oblique threads engaged, the number of oblique threads of a sheet necessary to cover the width of the three-dimensional fabric being provided by the number of parts of a pass bar decreased by one, and the total number of oblique threads engaged in a pass bar for a web exceeding the number of threads required for the width of the fabric by the amount of thread mounted on a part of pass bar, in such a way that when a pass-bar, following the transverse shifting movement, extends beyond one side of the lateral end of the fabric by a distance equal to the dimension of a part of pass-bar, this part is moved outside opposite end of the pass bar, the oblique threads engaged on this part being cut at their exit from the fabric, the ends of the threads engaged in the passettes being held in place.

9. Method for manufacturing a three-dimensional multiaxial fabric according to claim 8, characterized in that the guide bars (6a, 6b, 6c, 6d) are in two parts (6al, 6a2) and in that the total number oblique threads (3a, 3b, 3c, 3d) of a tablecloth is twice the number necessary to cover the width of the three-dimensional fabric.