METHOD FOR THE RESISTANCE WELDING OF FIBER-COMPOSITE COMPONENTS TO GIVE A FIBER-COMPOSITE STRUCTURE, FIBER-COMPOSITE STRUCTURE AND FIBER-COMPOSITE COMPONENT

Abstract

A method for resistance welding of two fiber-composite components to give a fiber-composite structure includes arranging conductive fibers within a jointing region of the two fiber-composite components, where each conductive fiber includes a carbon fiber with an electrically insulating coating. An electric current is passed through the conductive fibers to heat the jointing region to a welding temperature and melt the fiber-composite components in the jointing region. The jointing region is hardened in a manner that bonds the two fiber-composite components by way of the jointing region to give the fiber-composite structure.

Claims

1. A method for resistance welding of two fiber-composite components to give a fiber-composite structure, the method comprising: arranging conductive fibers within a jointing region of the two fiber-composite components, where each conductive fiber comprises a carbon fiber with an electrically insulating coating; passing an electric current through the conductive fibers to heat the jointing region to a welding temperature and melt the fiber-composite components in the jointing region; and hardening the jointing region to bond the two fiber-composite components by way of the jointing region to give the fiber-composite structure.

2. The method according to claim 1, where arranging the conductive fibers comprises placing of the fiber-composite components in closest-possible contact with one another at a jointing area.

3. The method according to claim 2, where at least a proportion of the conductive fibers is arranged in the jointing area between the two fiber-composite components.

4. The method according to claim 1, where at least a proportion of the conductive fibers is integrated into at least one of the two fiber-composite components in the jointing region such that at least ends of the respective conductive fibers protrude from the respective fiber-composite component.

5. The method according to claim 1, where arranging the conductive fibers comprises pressing of the two fiber-composite components against one another.

6. The method according to claim 1, where the conductive fibers are arranged in a form of at least one or more of bundles, tapes, mats, woven fabrics, non-woven fabrics, laid scrims and individual fibers.

7. The method according to claim 1, comprising: recording the welding temperature; and regulating the electric current on the basis of the recorded welding temperature.

8. The method according to claim 7, where the welding temperature is recorded by a thermographic camera.

9. The method according to claim 7, where the welding temperature is recorded by a temperature sensor integrated into the fiber-composite components.

10. The method according to claim 1, where the welding temperature corresponds at least to a melting point of polyetheretherketone.

11. The method according to claim 1, where conductive fibers used have a polymer-electrolyte coating as electrically insulating coating.

12. A fiber-composite structure produced by a method according to claim 1.

13. An aircraft or spacecraft with a fiber-composite structure according to claim 12.

14. A fiber-composite component for use in a method according to claim 1, which comprises: conductive fibers integrated into the fiber-composite component in a jointing region of the fiber-composite component such that at least ends of the respective conductive fibers protrude from the fiber-composite component, where each conductive fiber comprises a carbon fiber with an electrically insulating coating.

15. The fiber-composite component according to claim 14, where the electrically insulating coating is configured as polymer-electrolyte coating.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The disclosure herein is explained in more detail below with reference to the Inventive Examples provided in the diagrams of the Figures:

[0029] FIG. 1 is a diagrammatic cross-sectional view of a conductive fiber for use in a method for the resistance welding of two fiber-composite components according to an embodiment of the disclosure herein;

[0030] FIG. 2 is a diagrammatic perspective view of fiber-composite components with conductive fibers corresponding to FIG. 1 located therebetween;

[0031] FIG. 3 is a diagrammatic perspective view of fiber-composite components for use in a method for resistance welding according to another embodiment of the disclosure herein;

[0032] FIG. 4 is a flow diagram of a method for the resistance welding of two fiber-composite components as used in FIG. 2 or 3; and

[0033] FIG. 5 is a diagrammatic side view of an aircraft with a fiber-composite structure produced by the method from FIG. 4.

DETAILED DESCRIPTION

[0034] The figures attached are intended to increase understanding of the embodiments of the disclosure herein. They illustrate embodiments, and serve in conjunction with the description to explain principles and concepts of the disclosure herein. Other embodiments, and many of the advantages mentioned, are apparent from the drawings. The elements of the drawings have not necessarily been shown in true scale in relation to one another.

[0035] Unless otherwise stated, elements, features and components that are identical or functionally identical or have identical effect in each case have the same reference signs in the figures of the drawing.

[0036] FIG. 1 is a diagrammatic cross-sectional view of a conductive fiber 2 for use in a method M for the resistance welding of two fiber-composite components 1 according to an embodiment of the disclosure herein.

[0037] The conductive fiber 2 comprises a carbon fiber 3, provided with an electrically insulating coating 4. The electrically insulating coating 4 is configured as solid polymer-electrolyte coating. This type of electrochemical coating can by way of example be produced by immersing the carbon fiber 3 into a suitable electrochemical bath. In a specific example, the coating can be achieved via polymerization of methoxy polyethylene glycol monomethacrylate. By way of example, the carbon fiber 3 can have a diameter of from 6 to 7 micrometers. This type of solid polymer-electrolyte coating can be configured very thinly, for example with a thickness of 0.5 micrometer, the resultant overall diameter of the conductive fiber 2 being about 7 to 8 micrometers. This type of coating can moreover withstand temperatures above 700 C., and therefore has ideal suitability for the welding of thermoplastics such as PEEK.

[0038] This configuration of the conductive fiber 2 offers a number of advantages for the use in a resistance welding method. Firstly, the properties of the conductive fiber 2, in respect of structure, and also in relation to compatibility thereof with fiber-composite material, are similar to those of a conventional carbon fiber. It can therefore readily be used as reinforcement fiber in fiber-composite components, or integrated into the same, without any occurrence of undesired reactions. Secondly, the solid polymer-electrolyte coating is configured as electrical insulator which can insulate a conductive fiber 2 electrically from other conductive fibers 2, without any occurrence of leakage currents and/or short circuit between multiple conductive fibers 2 through which current is flowing and adjacent conductive fibers 2. This type of conductive fiber 2 is moreover sufficiently heat-resistant for welding of PEEK. Advantageous uses of such conductive fibers 2 in method M for the resistance welding of two fiber-composite components 1 are explained below with reference to the other figures.

[0039] To this end, FIG. 2 is a diagrammatic perspective view of fiber-composite components 1 with the conductive fibers 2 shown in FIG. 1, while FIG. 4 is a flow diagram of a corresponding method M for the resistance welding of two fiber-composite components 1.

[0040] The fiber-composite components 1 can by way of example have a matrix made of thermoplastic and is reinforced by a large number of carbon fibers. Thermoplastic can by way of example be polyetheretherketone (PEEK), which can have a very high melting point of about 380 C. The two fiber-composite components 1 are depicted purely diagrammatically in FIG. 2 as identically configured, rectangular blocks. In a specific use, the fiber-composite components 1 can by way of example be structural components for the fuselage of an aircraft 100, e.g. a passenger aircraft (cf. FIG. 5). The fiber-composite components 1 have been arranged above the other in a jointing region 5, and a large number of conductive fibers 2 have been provided in a sheet-like, grid-like arrangement in a jointing area 6 between the fiber-composite components 1. The conductive fibers 2 here protrude laterally from the jointing region 5. This arrangement of the fiber-composite components 1 and of the conductive fibers 2 is merely one example. In principle, the person skilled in the art can introduce conductive fibers 2 appropriate for a particular use, in the form of bundles, tapes, mats, woven fabrics, non-woven fabrics, laid scrims and/or individual fibers or the like, in a sheet-like arrangement or any other type of arrangement.

[0041] The method M accordingly comprises, as M1 (cf. FIG. 4), arranging the conductive fibers 2 within the jointing region 5 of the two fiber-composite components 1, where the fiber-composite components 1 are brought into closest-possible contact with one another at the jointing area 6, and at least a proportion of the conductive fibers 2 is arranged in the jointing area 6 between the two fiber-composite components 1. The method M moreover comprises, as M2, passing an electric current through the conductive fibers 2 in a manner that heats the jointing region 5 to a welding temperature and melts the fiber-composite components 1 in the jointing region 5. To this end it is possible by way of example to connect a power source from outside of the jointing region 5 to the conductive fibers 2. A force and/or a pressure can additionally be used to press the two fiber-composite components 1 against one another, in order to assist the binding of the components and to maximize uniformity of temperature distribution and, respectively, guarantee that the fiber-composite components 1 are in close contact across the entire jointing area 6.

[0042] The method M can moreover comprise, as M3, recording of the welding temperature and, as M4, regulating the electrical current on the basis of the welding temperature recorded. To this end, in this example of an embodiment a thermographic camera 7 is provided, for example a thermal imaging camera, which continuously records the welding temperature in a manner that permits, where appropriate, local or global adjustment of the electrical current if the welding temperature deviates from the desired temperature. Because PEEK is used in the present case as thermoplastic, care must be taken that the welding temperature at least exceeds the melting point of PEEK. An example of a welding temperature that could clearly be used as process temperature would be about 400 C.

[0043] Finally, the method comprises, as M5, hardening of the jointing region 5 in a manner such that the two fiber-composite components 1 are bonded by way of the jointing region 5 to give a fiber-composite structure 10. The protruding ends of the conductive fibers 2 can be removed. This fiber-composite structure 10 can by way of example be a higher-order structural component for an aircraft 100. FIG. 5 shows by way of example an aircraft 100 into which a fiber-composite structure 10 produced by the present method M, e.g. a strengthening element, a stringer, a crossmember, an external skin section, a ceiling panel, a floor panel and/or a wall panel or the like, has been introduced.

[0044] With the aid of the method M described it is therefore possible to produce a fiber-composite structure 10 from two fiber-composite components 1 by a resistance welding method that is efficient and that can easily be automated. The conductive fibers 2, which have a core made of carbon fibers 3, serve as current conductors here (i.e. as providers of resistance to generate the heat for welding), the individual conductive fibers 2 being insulated from one another by virtue of the electrically insulating coating 4. Leakage currents and undesired heat losses are thus prevented. There is no need to use metal grids or similar disadvantageous materials. Instead, carbon fibers 3 with a high-compatibility coating are used, and these can bind into the fiber-composite components 1 without any disadvantageous results, and moreover can serve to reinforce the components.

[0045] FIG. 3 is a diagrammatic perspective view of fiber-composite components 1 for use in a method M for resistance welding according to another embodiment of the disclosure herein.

[0046] Unlike the embodiment shown in FIG. 2, in this example the conductive fibers 2 have been integrated into the fiber-composite components 1 in a jointing region 5 in a manner such that ends of these protrude from the fiber-composite components 1. In FIG. 3, the conductive fibers 2 have been arranged, purely by way of example, parallel and alongside one another in the vicinity of a surface of the respective fiber-composite component 1. In this embodiment, the surface serves as jointing area 6 at which the two fiber-composite components 1 are placed in closest-possible contact with one another before a current is passed through the conductive fibers 2 (cf. the arrow in FIG. 3). By way of example, the conductive fibers 2 can be integrated directly into the fiber-composite components 1 during manufacture of the components, and can provide reinforcement. However, it is in principle equally possible that integration of the conductive fibers 2 into the fiber-composite components 1 is delayed until a subsequent juncture after manufacture. As soon as the fiber-composite components 1 have been placed into closest-possible contact with one another, a current is introduced into the conductive fibers 2, by way of which the fiber-composite components 1 are then welded to one another. The welding temperature can be recorded in this embodiment by way of example by temperature sensors 8 which have respectively been integrated into the fiber-composite components 1 in the vicinity of the conductive fibers 2 and can therefore determine the temperature directly in the jointing region 5. After hardening M5 of the jointing region 5, the protruding ends of the conductive fibers 2 can be removed, e.g. by cutting.

[0047] In principle, the disclosure herein is not restricted to the embodiments described. By way of example, the two embodiments from FIGS. 2 and 3 can be combined with one another in a manner such that a proportion of the conductive fibers 2 can have been arranged between the fiber-composite components 1 whereas another proportion of the conductive fibers 2 can already have been integrated into the fiber-composite components 1 during manufacture.

[0048] In the interests of conciseness, various features have been brought together in one or more examples in the detailed description above. However, it should be clear here that the above description is merely illustrative, and in no way restrictive. It serves to cover all of the alternatives, modifications and equivalents of the various features and Inventive Examples. After consideration of the above description, the person skilled in the art will immediately and directly conceive of many other examples on the basis of a person's technical knowledge.

[0049] The Inventive Examples have been selected and described with the aim of providing the best possible description of the principles underlying the disclosure herein and the possibilities for practical use of the principles. Persons skilled in the art can thus optimize modification and use of the disclosure herein and the various Inventive Examples thereof in relation to the intended application. In the claims, and also in the description, the words including and having are used as neutral words with the meaning comprising. Use of the words a and of one moreover is not intended in principle to exclude a plurality of features and components thus described.

[0050] While at least one exemplary embodiment of the present invention(s) is disclosed herein, it should be understood that modifications, substitutions and alternatives may be apparent to one of ordinary skill in the art and can be made without departing from the scope of this disclosure. This disclosure is intended to cover any adaptations or variations of the exemplary embodiment(s). In addition, in this disclosure, the terms comprise or comprising do not exclude other elements or steps, the terms a, an or one do not exclude a plural number, and the term or means either or both. Furthermore, characteristics or steps which have been described may also be used in combination with other characteristics or steps and in any order unless the disclosure or context suggests otherwise. This disclosure hereby incorporates by reference the complete disclosure of any patent or application from which it claims benefit or priority.

KEY

[0051] 1 Fiber-composite component [0052] 2 Conductive fiber [0053] 3 Carbon fiber [0054] 4 Electrically insulating coating [0055] 5 Jointing region [0056] 6 Jointing area [0057] 7 Thermographic camera [0058] 8 Temperature sensor [0059] 10 Fiber-composite structure [0060] 100 Aircraft [0061] M Method [0062] M1 Method step [0063] M2 Method step [0064] M3 Method step [0065] M4 Method step [0066] M5 Method step