Fabric for use in composite materials and method for producing said fabric and a composite material body

Abstract

A fabric (10) for use in composite materials having a reinforcing system (11) made of reinforcing warp threads (13) and reinforcing weft threads (14), which are placed on top of one other in two different reinforcing layers (16), (17). A binding system (12) of binding warp threads (20) and binding weft threads (21) is formed from a binding yarn (30) with a lower yarn count than the reinforcing yarn (15). The reinforcing system (11) is enclosed between the binding warp threads (20) on the one side and the binding weft threads (21) on the other side, and thus, held in place at binding points (22). At each binding point (22), a binding warp thread (20) is guided and held between a stationary warp thread (25) and a regular warp thread (24) of a warp thread pair (23) of binding warp threads (20). Between two adjacent binding points of a warp thread pair (23), the stationary warp thread (25) and the regular warp thread (24) have intersecting points (26).

Claims

1. A fabric (10) for use in composite materials, comprising a reinforcing system (11) of reinforcing warp threads (13) and reinforcing weft threads (14), said reinforcing warp threads (13) forming a first reinforcing layer (16), said reinforcing weft threads (14) being placed on said first reinforcing layer (16) of said reinforcing warp threads (13) without binding with the reinforcing warp threads (13) for forming a second reinforcing layer (17); a binding system (12) of binding warp threads (20) and binding weft threads (21), said reinforcing system (11) being located between the binding weft threads (21) and the binding warp threads (20), pairs of said binding warp threads (20) each comprising a stationary warp thread (25) and a directly adjacent regular warp thread (24) which cross each other multiple times with said binding warp threads (20) being woven to a binding weft thread (21) by a leno weave at binding points (22) between the stationary warp thread (25) and a regular warp (24) of each pair for securing together the first and second reinforcing layers (16, 17) without a weaving connection between the threads of the reinforcing system (11) and binding system (12).

2. The fabric (10) of claim 1 in which intersecting points (26) between crossing stationary warp threads (25) and regular warp threads (24) are located at the binding points (22) with the weft thread (21).

3. The fabric (10) of claim 1 in which reinforcing warp threads (13) cross the reinforcing weft threads (14) at intersecting points (18), and the number of intersecting points of the reinforcing warp threads (13) with the reinforcing weft threads (14) of the reinforcing system (11) is equal to or greater than the number of binding points (22) of the binding system (12).

4. The fabric (10) of claim 1 in which said reinforcing system (11) is made of a reinforcing yarn (15) comprising said reinforcing warp and weft threads (13, 14) and said binding system is made of a binding yarn (30) different from said reinforcing yarn (15) comprising said binding warp and weft threads (20, 21), said binding yarn (30) having a smaller cross-section than the reinforcing yarn (15).

5. The fabric (10) of claim 1 in which said reinforcing system (11) is made up of reinforcing yarn (15) comprising said reinforcing warp and weft threads (13, 14) and said binding system is made up of binding yarn (30) different from said reinforcing yarns (15) comprising said binding warp and weft threads (20, 21), and said binding yarn (30) has a lower titer than the reinforcing yarn (15).

6. The fabric (10) of claim 4 in which said reinforcing yarn (15) comprises at least one of carbon, aramid, or glass fibers.

7. The fabric (10) of claim 4 in which said reinforcing yarn (15) has a flat cross-section with a dimension in one direction (B) greater than the dimension at a right angle thereto.

8. The fabric (10) of claim 4 in which said binding yarn (30) is made of a material that will bind with a plastic material of a composite material during the production of a composite material.

9. The fabric (10) of claim 4 in which the material and titer of the binding yarn (30) are such that an interlaminary shearing strength of a composite material produced therefrom deviates from a nominal value prespecified by the reinforcing system (11) by a maximum of one prespecified tolerance value.

10. The fabric (10) of claim 4 in which the binding yarn (30) contains plastic material.

11. The fabric (10) of claim 4 in which the binding yarn (30) contains a phenoxy plastic material.

12. The fabric (10) of claim 4 in which the binding yarn (30) comprises a core (31) and a coat (32) enclosing the core (31), said core (31) having a higher melting temperature than said coat (32).

13. A method for producing the fabric (10) of claim 1, comprising the steps of: loading a weaving machine (35) with reinforcing warp threads (13), binding warp threads (20), reinforcing weft threads (14), and binding weft threads (21), inserting the reinforcing weft threads (14) and the binding weft threads (21) in a prespecified sequence, during insertion of the reinforcing weft threads (14) maintaining the reinforcing warp threads (13) in a same upper shed or lower shed, and during insertion of binding weft threads (21), for each pair binding warp threads (20), a binding warp thread (20) acting as a regular warp thread (24) is maintained in the same upper or lower shed while a binding warp thread (20) acting as a stationary warp thread (25) of each pair, as well as the reinforcing warp threads (13), are maintained in the other shed, and intersecting the regular warp thread (24) with the stationary warp thread (25) of each pair between the weft insertions with the binding weft thread (21) for forming (1) a reinforcing system (11) of reinforcing weft threads (14) and reinforcing warp threads (13) wherein the reinforcing warp threads (13) form a first reinforcing layer (16), the reinforcing weft threads (14) being placed on said reinforcing layer without binding with the reinforcing warp threads (13) for forming a second reinforcing layer (17), and (2) a binding system (12) of binding weft threads (21) and binding warp threads (20) woven together by a leno weave at binding points (22) for securing together the first and second reinforcing layers (16, 17) without a weaving connection between the threads of the reinforcing system (11) and binding system (12).

14. The method of claim 13 including guiding the reinforcing warp threads (13) in a single shared weaving shaft (41) of the weaving machine (35), and guiding the stationary warp threads (25) and the regular warp threads (24) in different weaving shafts (39, 40) of the waving machine (35).

15. The method of claim 14 including adapting the fabric (10) to the desired shape of a composite material body to be produced by melting the threads (20, 21) of the binding system (12) by thermal action in at least one melting region (46).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic plan view of an illustrative fabric in accordance with the invention;

(2) FIG. 2 is a schematic plan view of two successive binding points of the fabric, such as shown in FIG. 1, having a first binding type of binding system;

(3) FIG. 3 is a vertical section of the illustrated fabric taken in the plane of line III-III in FIG. 2;

(4) FIG. 4 is a schematic plan view of two successive binding points of the fabric, such as used in FIG. 1, with a second binding type of binding system;

(5) FIG. 5 is a vertical section of the illustrated fabric taken in the plane of line V-V in FIG. 4;

(6) FIG. 6 is a perspective schematic of a fabric such as shown in FIG. 1, for the production of a preform;

(7) FIG. 7 is a perspective of the structure of a binding yarn, including core and coat, used in the illustrated fabric;

(8) FIG. 8 is a perspective of a reinforcing yarn of the illustrated fabric;

(9) FIG. 9 is a schematic of a weaving machine during insertion of binding weft threads in the production of the illustrated fabric; and

(10) FIG. 10 is a schematic of the weaving machine shown in FIG. 8 during insertion of reinforcing weft threads in the production of the illustrated fabric.

(11) While the invention is susceptible of various modifications and alternative constructions, certain illustrative embodiments thereof have been shown in the drawings and will be described below in detail. It should be understood, however, that there is no intention to limit the invention to the specific forms disclosed, but on the contrary, the intention is to cover all modifications, alternative constructions, and equivalents falling within the spirit and scope of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(12) Referring more particularly to FIG. 1 of the drawings, there is shown an illustrative fabric 10 in accordance with the invention for the production of composite materials or composite material bodies, in particular a composite of fabric 10 and plastic material. The fabric 10 comprises a reinforcing system 11, as well as a binding system 12. The reinforcing system 11 consisting of reinforcing warp threads 13 and reinforcing weft threads 14 is disposed to impart the composite material or the composite material body with the desired mechanical properties by interacting with another material, specifically plastic. In doing so, the reinforcing system 11 improves the strength and stiffness of the composite material. In the exemplary embodiment, the reinforcing warp threads 13 and the reinforcing weft threads 14 consist of a reinforcing yarn 15 having a flat cross-section, as can be seen, for example, in FIGS. 3, 5 and 7. The flat cross-section is characterized in that its width in a width direction B is greater than its height in height direction H at a right angle relative to the width direction B. In particular, the width may be greater by at least the factor 2 than the height H of the reinforcing yarn 15. In the exemplary embodiment, the cross-section is elliptical or oval.

(13) In order to ensure optimal mechanical properties, a convolution of the reinforcing threads 13, 14 is to be avoided. For this purpose, the reinforcing warp threads 13 are arranged parallel in a first reinforcing layer. The reinforcing weft threads 14 extend at a right angle thereto and form a second reinforcing layer 17. In the plan view of the fabric 10 in FIG. 1, as well the first reinforcing layer 16 is positioned above the second reinforcing layer 17; however, this depends on the direction from which the fabric 10 is being viewed. The reinforcing warp threads 14 and the reinforcing weft threads 13 are superimposed without binding. They form a plurality of intersecting points 18 that are not bound. The reinforcing threads 13, 14 of the reinforcing system 11 extend at the smallest possible distance next to each other, so that a tightly woven fabric 10 is the result. It will be understood that the drawing is only a schematic illustration and not true to scale.

(14) The reinforcing yarn 15 comprises carbon fibers, aramid fibers or glass fibers or is made of such fibers. Alternatively, the use of other reinforcing yarns 15 is also possible. For example, it is possible to embody the reinforcing yarn as a so-called roving, wherein a plurality of individual fibers are arranged parallel next to each other without being twisted and form the reinforcing yarn 15.

(15) The reinforcing warp threads 13 and the reinforcing weft threads 14 extend stretched in their respective reinforcing layer 16 or 17. This is understood to mean that there will be no kinks or convolutions of the reinforcing threads 13, 14 in the fabric 10 caused by binding. Radii or curvatures of the reinforcing threads 13, 14 are formed only by shaping the fabric in the composite material or the composite material body while it is being draped. In this manner, it is possible to achieve optimal strength and stiffness.

(16) The binding system 12 consists of binding warp threads 20 and binding weft threads 21. The binding warp threads extend parallel to each other and parallel to the reinforcing warp threads 13 in warp thread direction K. At a right angle thereto in the weft thread direction S, in which extend the reinforcing weft threads 14, the binding weft threads 21 extend. In the exemplary embodiment, the binding weft threads 21 extend adjacent the first reinforcing layer 16, while the binding warp threads 20 extend adjacent the second reinforcing layer 17. In this manner, the binding warp threads 20 and the binding weft threads 21 enclose the reinforcing system 11 sandwich-like. A binding of the fabric 10 is accomplished only by the binding system 12. To accomplish this, the binding warp threads 20 are woven to the binding weft threads 21 at the binding points 22. In the case of fabric 10, this is accomplished by a so-called leno weave, so that the binding system 12 could also be referred to as a leno system.

(17) FIGS. 2 through 5 show more detailed illustrations of the weave at the binding points 22. FIGS. 2 and 3 show a half-leno weave, while FIGS. 4 and 5 show full leno weaves. The binding warp threads 20 are arranged in the form of warp thread pairs 23. In doing so, a binding warp thread 20 of a warp thread pair 23 represents a regular warp thread 24, while the respectively other binding warp thread 20 acts as the stationary warp thread 25. At the binding points 22, the binding weft thread 21 extends between the regular warp thread 24 and the stationary warp thread 25 of a warp thread pair 23 and is thus held in place. In this manner, a good fixation of the relative position of the threads 20, 21 in the binding system 12 is achieved, thus resulting in a great displacement resistance of the fabric 10. This displacement resistance can be produced without high thread tension in the binding system 12. Due to the only minimal thread tension, a convolution of the reinforcing warp threads 13 and the reinforcing weft threads 14 in the reinforcing system 11 is avoided. The elongated reinforcing threads 13, 14 guarantee the desired mechanical properties of the composite material.

(18) The stationary warp threads 25 and the regular warp threads 24 of a warp thread pair 23 have intersecting points 26. In the exemplary embodiment, one or two intersecting points 26 are provided between each of the binding points 23. As is shown in FIGS. 2 through 5, in particular, the intersecting points 26 are located preferably directly in front of or behind a binding point 22. In other words, a respective intersecting point 26 of the binding warp threads 20 is arranged in the area between two reinforcing warp threads 13 and two reinforcing weft threads 14 where there is also a binding point 22. In this manner, the space required in any event for the binding point 22 between the reinforcing threads 13, 14 of the reinforcing system 12 is used for providing the intersecting points 26.

(19) Referring to the half leno weave shown in FIGS. 2 and 3, the regular warp threads 24 extendin viewing direction on the binding weft threads 21at the binding points 22 above the respective binding weft thread 21. Correspondingly, the stationary warp thread 25 extends on the binding points 22 always on the other side underneath the binding weft thread 21. In the half leno weave, intersecting points 26 exist only at every second binding point 22 of a warp thread pair 23, i.e., preferably directly in front of and behind the binding point 22 of the respective binding weft thread 21.

(20) Different therefrom, in the full leno weave as in FIGS. 4 and 5, the stationary warp thread 25 and the normal warp thread 24 extend alternately once above and once below the binding warp thread 21. In the full leno weave, each binding point 22 of a warp thread pair 23 has intersecting points 26, i.e., preferably in front of and behind the binding point 22 with the respective binding weft thread 21.

(21) In any event, in all binding types, the binding warp thread 21 is received between the regular warp thread 24 and the stationary warp thread 25 and fixed in place at the binding point 22.

(22) In the exemplary embodiment, the number of binding weft threads 21 is lower than the number of reinforcing threads 14. The number of binding points 22 in the binding system 12 is thus smaller than the number of intersecting points 18 in the reinforcing system 11. The number of binding warp thread pairs 20 is at most as great as the number of reinforcing warp threads 13, wherein the number is preferably smaller. The float in the binding system 12, i.e., the distance between the binding points 22, may remain constant or also vary within the fabric 10. Fabric areas that require a greater displacement resistance may have a greater number of binding points 22. Fabric areas that require a better shiftability of the reinforcing threads 13, 14 of the reinforcing system 11, e.g., to improve drapability, may display a greater distance between the binding points 22 and thus display a greater float. The float in the fabric 10 may vary in longitudinal direction of the fabric and/or in transverse direction of the fabric.

(23) FIG. 7 shows the reinforcing yarn 15 and also, schematically, a binding yarn 30. In the exemplary embodiment, the binding yarn 30 has a circular cross-section. In accordance with the example, the cross-section in width direction B and/or in height direction H is smaller than the cross-section of the reinforcing yarn 15. Preferably, the titer of the binding yarn 30 is smaller than the titer of the reinforcing yarn 15. In the exemplary example, the titer of the binding yarn 30 is a maximum of 500 dtex.

(24) In the preferred exemplary embodiment, a hot-melt adhesive yarn is used, said yarn, for example, consisting of copolyester or of Grilon MS by EMS Chemie company. It is also possible to use other phenoxy yarns. The binding yarn 30 mentioned as the hot-melt adhesive yarn has a core 31 that is completely enclosed in circumferential direction by a coat 32. The core 31 and the coat 32 consist of different materials. In particular, the melting temperature of the coat 32 is lower than the melting temperature of the core 31. As a result of this, it is possible in the production of a composite material body to fix an appropriately shaped fabric 10 in place or combine it with other fabric layers, should this be desirable, for example in the manufacture of a preform. In this case, the hot-melt adhesive bonding with other material layers can be accomplished very simply by thermal action, without additional binders. At the same time, the binding yarn 30 remains stable because the core 31 does not melt due to its higher melting temperature. FIG. 6 shows schematically a shaping of a fabric section.

(25) The fabric 10 is used for the production of a composite material body. If, as shown by FIG. 6, a fabric layer 45 is to be fixed in place beforehand and/or bound to additional fabric layers in the course of a manufacturing process and is to be fixed in place beforehand in a desired three-dimensional form, the fabric layer 45 or the superimposed fabric layers can be treated by thermal action within a melting region 46. Thus it is possible to produce a preform, for example. However, this fixation can also take place only during the subsequent shaping during the production of the composite material body. In doing so, the binding threads 20, 21 of the binding system 12 may also insert a hot-melt adhesive bond with the plastic material of the composite material body. In this manner, also a good interlaminar bond is achieved, thus ensuring a high interlaminar shearing strength of the composite material body.

(26) FIGS. 8 and 9 schematically show a weaving machine 35 for the manufacture of a fabric 10. The weaving machine 35 comprises a back-rest 36 by means of which the warp threads 13, 20 can be fed. The warp threads 13, 20 then move through a warp stop motion 37 and through the drop wires 38. In continuation, the weaving shafts, each having a plurality of healds, are provided, said healds being disposed for shed formation. The stationary warp threads 25 are guided in a shared first weaving shaft 39. A second weaving shaft 40 guides the regular warp threads 24. A thread weaving shaft 41 guides the reinforcing warp threads 13. A reed 43 for the abutment of the warp threads 21 and 14, respectively, against the weaving edge is provided between the weaving shafts 39, 40, 41 and a fabric take-down 42.

(27) The regular warp threads 24 are guided in a leno harness in the second weaving shaft 40. Such a system is described, for example, in publication EP 2 063 007 A1, to which reference is made to this extent. There, half-leno bindings are produced. As an alternative thereto, leno harnesses have also been known for the production of full leno weaves, which may be used alternatively. Preferably, special healds are provided in the third weaving shaft 41 for guiding the reinforcing warp threads 13, said healds being known, for example from publication EP 1 795 636 A1.

(28) During the manufacture of the fabric 10 with the use of the weaving machine 35, the warp threads 13, 20 are fed via the back-rest 36. The reinforcing warp threads 14 and the binding weft threads 21 are inserted in a prespecified sequence. When a reinforcing weft thread 21 is inserted, the first weaving shaft 39 positions the stationary warp threads 25 in the upper shed. The regular warp threads 24, as well as the reinforcing warp threads 13, are positioned via the two weaving shafts 40, 41 in the lower shed. Depending on the leno weave, the intersecting points 26 are formed in the second weaving shaft 40 by means of the leno harness, as illustrated in FIGS. 2 through 5. During the insertion of a reinforcing weft thread 14, only the reinforcing warp threads 13 are in the upper shed. The binding warp threads 20, i.e., the regular warp threads 24 as well as the stationary warp threads 25, are in the lower shed. FIG. 8 shows the insertion of a binding weft thread 21, while FIG. 9 shows the insertion of the reinforcing weft thread 14.

(29) Depending on the number of binding points 22 and their distance from each other, two or more reinforcing weft threads 14 are inserted after the insertion of a binding weft thread 21. The number of reinforcing weft threads 14 extending between two binding weft threads 21 may vary. Likewise, the number of reinforcing warp threads 13 between two warp thread pairs 23 of binding warp threads 12 may vary. For this purpose, the weaving machine 35 may also remove individual warp thread pairs 23 of binding warp threads 20 or individual reinforcing warp threads 13 from the weaving process. To do so, not specifically shown warp thread holders may be provided, these separating the warp threads 13, 20 that are to be taken out and holding them available in the region of the fabric edge before the fabric take-down 42. The warp thread holder is spatially movable for grasping and positioning the warp thread that is to be separated. The weaving machine 35 may also comprise several such warp thread holders. Furthermore, the weaving machine 35 may comprise an appropriate holding device, to which the warp thread holder feeds the separated and taken out warp thread, so that the holding device can hold the warp thread in a desired position ready for the later renewed supply.

(30) From the foregoing it can be seen that a fabric 10 is provided for use in composite materials and composite material bodies. The fabric 10 has a reinforcing system 11 made of reinforcing warp threads 13 and reinforcing weft threads 14, which are placed on top of one other in two different reinforcing layers 16, 17, without binding, and represent a core so-to-speak. The reinforcing threads 13, 14 are formed from a reinforcing yarn 15. A binding system 12 of binding warp threads 20 and binding weft threads 21 is formed from a binding yarn 30 with a lower yarn count than the reinforcing yarn 15. The fabric is bound exclusively within the binding system 12. The reinforcing system 11 is enclosed between the binding warp threads 20 on the one side and the binding weft threads 21 on the other side, and thus held in place. Binding points 22 are provided in the binding system 12. At each binding point 22, a binding warp thread 20 is guided and held between a stationary warp thread 25 and a regular warp thread 24 of a warp thread pair 23 of binding warp threads 20. Between two adjacent binding points 22 of a warp thread pair 23, the stationary warp thread 25 and the regular warp thread 24 have at least one intersecting point 26. All warp threads 13, 20 run in one warp thread direction K substantially parallel to one another. All weft threads 14, 21 run in one weft thread direction S substantially parallel to one another and transverse to the warp thread direction K.

LIST OF REFERENCE SIGNS

(31) 10 Fabric 11 Reinforcing system 12 Binding system 13 Reinforcing warp threads 14 Reinforcing weft threads 15 Reinforcing yarn 16 First reinforcing layer 17 Second reinforcing layer 18 Intersecting points 20 Binding warp thread 21 Binding weft thread 22 Binding point 23 Warp thread pair 24 Regular warp thread 25 Stationary warp thread 26 Intersecting point 30 Binding yarn 31 Core 32 Coat 35 Weaving machine 36 Back-rest 37 Warp stop motion 38 Drop wires 39 First weaving shaft 40 Second weaving shaft 41 Third weaving shaft 42 Fabric take-down 43 Reed 45 Fabric layer 46 Melting region B Width direction H Height direction K Warp thread direction S Weft thread direction