KNITTED THREE-DIMENSIONAL ELECTROCONDUCTIVE MAT FOR USE AS A LIGHTNING-RESISTANT WALL

Abstract

A three-dimensional electroconductive mat formed of an electroconductive knitted fabric capable of homogeneously distributing electrical charges over the entire surface thereof, wherein the knitted fabric includes at least one electroconductive metal filament yarn; a composite material including such a mat, and 40 to 95% by volume of a thermoplastic and/or thermosetting polymer material.

Claims

1. A three-dimensional electroconductive mat consisting of an electroconductive knitted fabric capable of homogeneously distributing electrical charges over an entire surface thereof, wherein the electroconductive knitted fabric comprises at least one electroconductive metal filament yarn.

2. The mat according to claim 1, wherein the at least one electroconductive metal filament yarn is made of copper, bronze, aluminum, brass, titanium, silver, gold or alloys thereof.

3. The mat according to claim 2, wherein the electroconductive knitted fabric comprises a single metal filament yarn.

4. The mat according to claim 1, wherein the electroconductive knitted fabric comprises at least one electroconductive unidirectional (UD) yarn able to move and discharge electrical charges in a direction of the UD yarn.

5. The mat according to claim 4, wherein the at least one electroconductive (UD) yarn is metal.

6. The mat according to claim 5, wherein the at least one electroconductive (UD) yarn comprises a plurality of metal UD yarns and the plurality of metal UD yarns consist of a bundle of twelve copper yarns of 0.02 to 2 mm in diameter, or have an electrical conductivity of a same order as that of such a bundle.

7. The mat according to claim 1, wherein the electroconductive knitted fabric comprises at least two different electroconductive materials.

8. The mat according to claim 1, wherein the electroconductive knitted fabric comprises 0 to 40% by volume of one or more reinforcement yarns.

9. A composite material comprising a three-dimensional electroconductive mat according to claim 1, and 40 to 95% by volume of thermoplastic and/or thermosetting polymer material.

10. The composite material according to claim 9, wherein the thermoplastic and/or thermosetting polymer material comprises 100 to 5% by volume of thermoplastic material and 0 to 95% by volume of thermosetting resin.

11. The composite material according to claim 10, wherein the volume proportion of thermosetting polymer material is greater than a proportion by volume of thermoplastic polymer material.

12. The composite material according to claim 1, wherein the composite material is obtained by combining reinforcing fibers with a mat according to claim 1.

13. The composite material according to claim 12, wherein the composite material is obtained by superimposing a mat according to claim 1, and one or more knitted fabrics of reinforcement yarn(s).

14. A method comprising providing a three-dimensional electroconductive mat according to claim 1 to constitute a lightning-resistant wall of a land, water or aerial vehicle, or a building.

15. The mat according to claim 3, wherein the single metal filament yarn is a yarn of copper from 0.01 to 1 mm in diameter.

16. The mat according to claim 8, wherein the one or more reinforcement yarns are made of carbon fiber, glass or aramid.

17. The method according to claim 14, wherein the three-dimensional electroconductive mat constitutes a lightning-resistant wall of train body part, airplane fuselage or space vehicle.

18. A method comprising providing a composite material according to claim 9 to constitute a lightning-resistant wall of a land, water or aerial vehicle, or a building.

19. The method according to claim 18, wherein the composite material constitutes a lightning-resistant wall of train body part, airplane fuselage or space vehicle.

Description

COUNTER-EXAMPLE 1

[0034] A composite is made by adding, side-by-side, a copper mesh fabric with a grammage equal to 80 g/m.sup.2, intended to homogeneously distribute the electrical charges over the entire surface, and a copper foil 10 cm wide and a few tenths of a mm thick, which has the function of collecting the charges from the copper fabric and of discharging them towards the rear of the airplane, then by superimposing the assembly thus obtained, of which part of the surface consists of the copper mesh fabric and the other part of the surface consists of the copper foil, of a mat of woven carbon fibers pre-impregnated with epoxy resin.

[0035] This material is very difficult to drape, and all the more in three-dimensional complex form. This material was punctured and stripped the first time it was struck by lightning.

EXAMPLE 1

[0036] An electroconductive knitted fabric is made with one or more mesh, filler and/or float yarn(s), each consisting of a copper yarn 0.1 mm in diameter and a thermoplastic polymer material integrated into the metal knitted structure in the form of one or more mesh, filler and/or float yarn(s) and/or one or more weft yarn(s) added into the knitted fabric in the form of unidirectional yarn(s). This knitted fabric is made directly in the desired three-dimensional shape, regardless of its complexity. It has a continuity of its conductive yarns/fibers.

[0037] To this three-dimensional electroconductive knitted fabric, one or more reinforcing mat(s) of the same three-dimensional geometry are superimposed, and consisting of a woven fabric, a mat or a knitted fabric of reinforcing fibers such as carbon, glass or aramid, associated with a thermoplastic polymer material. A first example of reinforcing knitted fabric is a Kevlar? (aramid) and thermoplastic knitted fabric, that is to say having one or more mesh, filler and/or float yarn(s) consisting of aramid on the one hand, of thermoplastic on the other hand, wherein are inserted a plurality of unidirectional (UD) carbon yarns and a plurality of unidirectional UD yarns as weft yarns. A second example of reinforcing knitted fabric is a glass and thermoplastic knitted fabric. A third example of reinforcing knitted fabric is a carbon and thermoplastic knitted fabric.

[0038] The composite material can be obtained in any three-dimensional complex form desired, in a single piece, with continuity of the fibers, after firing at a temperature greater than the Tg of the thermoplastic, and cooling.

EXAMPLE 2

[0039] The electroconductive knitted fabric of example 1 is modified by inserting twelve parallel unidirectional (UD) copper yarns with a diameter of 0.2 mm as weft yarns of the knitted fabric. To this three-dimensional electroconductive knitted fabric, the same woven fabrics, mats, and knitted fabrics are superimposed as in example 1.

EXAMPLES 3 AND 4

[0040] Examples 1 and 2 are reproduced, except that the reinforcement knitted fabrics, mats and woven fabrics are pre-impregnated with liquid thermosetting resin in such a quantity that the polymer material of the composite material constitutes at least 40% of them by volume, divided into a majority of thermosetting polymer and a minority of thermoplastic polymer.

EXAMPLES 5 AND 6

[0041] Examples 1 and 2 are reproduced, but without using one or more reinforcement mats. Instead of these, the reinforcement function in the copper knitted fabric is incorporated by means of one or more mesh, filler and/or float yarn(s) and/or one or more unidirectional (UD) yarns as weft yarns, consisting of reinforcing fibers such as carbon, glass or aramid.

EXAMPLES 7 AND 8

[0042] Examples 5 and 6 are reproduced, impregnating the reinforced copper knitted fabric with liquid thermosetting resin in such a quantity that the polymer material of the composite material constitutes at least 40% of them by volume, divided into a majority of thermosetting polymer and a minority of thermoplastic polymer.

[0043] The homogeneous distribution of the fillers over the entire surface by the copper knitted fabric is very effective: The paint was burned homogeneously despite at least four lightning strikes without destroying the copper knitted fabric, which always homogeneously conducts the electrical current even after these strikes.

[0044] The charge displacement/discharge function by the unidirectional copper (UD) yarns with relatively large cross-section and electrical conductivity remains very efficient, the UD yarns having been sufficiently conductive to drain the charges without burning the paint, and therefore without heating.

[0045] The mechanical function provided by the reinforcing fibers/yarns of the fabric, mat and knitted fabric remains intact after repeated strikes without structural degradation by the shock wave which was absorbed by the very sturdy material without piercing the material, whereas the composite of counter-example 1 was pierced and stripped upon the first lightning strike.