Fixing thread for sewing together reinforcing fibers

Abstract

The invention relates to a fixing thread 1, 5, 10, 16 for sewing together reinforcing fibers, in particular to form a fiber preform, for the production of a fiber-reinforced composite component by means of impregnation with a curable polymer material. According to the invention, the fixing thread 1, 5, 10, 16 has an interface 4, 9, 15, 19 for locally increasing the ductility of a matrix formed by the curable polymer material and has at least one core thread 2, 6, 11, 12, 17, so as in particular to reduce the tendency for microcracks to form in the matrix of the finished composite component in the regions where the fixing threads 1, 5, 10, 16 penetrate. The interface 4 may be formed, for example, by an enclosure of the core thread 1 by a thermoplastic polymer material, for example by polyethylene, polypropylene or the like.

Claims

1. In a fiber preform for production of a fiber-reinforced composite component by impregnation with a curable polymer material, the improvement comprising a fixing thread with which reinforcing fibers of the preform are sewn or fixed together, wherein the fixing thread comprises an interface of a thermoplastic polymer material to locally increase ductility of a matrix formed by the curable polymer material in the regions where the fixing thread penetrates or projects into the matrix, the fixing thread having at least one core thread, which is formed by a plurality of filaments of carbon fibers, wherein the at least one core thread has a semicircular cross-sectional geometry and wherein the interface comprises an interface thread with a semicircular cross-sectional geometry which is bonded to the at least one semi-circular core thread.

2. The improvement of claim 1, wherein the fixing thread has a substantially circular circumferential contour.

3. The improvement of claim 1, wherein the fixing thread includes a plurality of core threads, with each core thread comprising a plurality of filaments of carbon fibers.

4. In a fiber preform for production of a fiber-reinforced composite component by impregnation with a curable polymer material, the improvement comprising a fixing thread with which reinforcing fibers of the preform are sewn or fixed together, wherein the fixing thread comprises an interface of a thermoplastic polymer material to locally increase ductility of a matrix formed by the curable polymer material in the regions where the fixing thread penetrates or projects into the matrix, the fixing thread having a plurality of core threads, each of which is formed by a plurality of filaments of carbon fibers, wherein the interface comprises at least one interface thread, wherein the plurality of core threads and the at least one interface thread are twisted with one another.

5. The improvement of claim 4, wherein the fixing thread has a substantially circular circumferential contour.

6. In a fiber preform for production of a fiber-reinforced composite component by impregnation with a curable polymer material, the improvement comprising a fixing thread with which reinforcing fibers of the preform are sewn or fixed together, wherein the fixing thread has a substantially circular circumferential contour and comprises an interface of a thermoplastic polymer material to locally increase ductility of a matrix formed by the curable polymer material in the regions where the fixing thread penetrates or projects into the matrix, the fixing thread having at least one core thread, which is formed by a plurality of filaments of carbon fibers, wherein the interface comprises at least one interface thread in strip form, which is wound around the at least one core thread.

7. The improvement of claim 6, wherein the fixing thread includes a plurality of core threads, with each core thread comprising a plurality of filaments of carbon fibers.

8. In a fiber-reinforced composite component produced by impregnation of a fiber preform with a curable polymer material, the improvement comprising a fixing thread with which reinforcing fibers of the preform are sewn or fixed together, wherein the fixing thread comprises an interface of a thermoplastic polymer material which locally increases ductility of a matrix formed by the curable polymer material in the regions where the fixing thread penetrates into the matrix, the fixing thread having at least one core thread, which is formed by a plurality of filaments of carbon fibers, wherein the at least one core thread has a semicircular cross-sectional geometry and wherein the interface comprises an interface thread with a semicircular cross-sectional geometry which is bonded to the semi-circular core thread.

9. The improvement of claim 8, wherein the fixing thread has a substantially circular circumferential contour.

10. The improvement of claim 8, wherein the fixing thread includes a plurality of core threads, with each core thread comprising a plurality of filaments of carbon fibers.

11. In a fiber-reinforced composite component produced by impregnation of a fiber preform with a curable polymer material, the improvement comprising a fixing thread with which reinforcing fibers of the preform are sewn or fixed together, wherein the fixing thread comprises an interface of a thermoplastic polymer material which locally increases ductility of a matrix formed by the curable polymer material in the regions where the fixing thread penetrates into the matrix, the fixing thread having a plurality of core threads, each of which is formed by a plurality of filaments of carbon fibers, wherein the interface comprises at least one interface thread, wherein the core threads and the at least one interface thread are twisted with one another.

12. The improvement of claim 11, wherein the fixing thread has a substantially circular circumferential contour.

13. In a fiber-reinforced composite component produced by impregnation of a fiber preform with a curable polymer material, the improvement comprising a fixing thread with which reinforcing fibers of the preform are sewn or fixed together, wherein the fixing thread has a substantially circular circumferential contour and comprises an interface of a thermoplastic polymer material which locally increases ductility of a matrix formed by the curable polymer material in the regions where the fixing thread penetrates into the matrix, the fixing thread having at least one core thread, which is formed by a plurality of filaments of carbon fibers, wherein the interface comprises at least one interface thread in strip form which is wound around the at least one core thread.

14. The improvement of claim 13, wherein the fixing thread includes a plurality of core threads, with each core thread comprising a plurality of filaments of carbon fibers.

Description

(1) In the drawing:

(2) FIG. 1 shows a cross section through a first exemplary embodiment of the fixing thread according to the invention,

(3) FIG. 2 shows a cross section through a second exemplary embodiment of the fixing thread according to the invention,

(4) FIG. 3 shows a cross section through a third variant of the fixing thread according to the invention and

(5) FIG. 4 shows a plan view of a portion of a fourth variant of the fixing thread according to the invention.

(6) FIG. 1 shows a cross section through a first exemplary embodiment of the fixing thread according to the invention.

(7) A fixing thread 1 is formed by a core thread 2, which has an enclosure 3 of a thermoplastic material to form an interface 4. The core thread 2 is a conventional fixing thread, for example a polyester thread which can only undergo low mechanical loads, or the like. The enclosure 3 represents the interface 4 with respect to the surrounding matrix of the curable polymer material, which is not represented, whereby the desired local increase in ductility of the surrounding matrix is obtained, in particular in the regions where the fixing thread 1 penetrates, so that the tendency for microcracks to form in the matrix of the finished composite component is reduced significantly by the use of the fixing thread 1. During the curing process, the thermoplastic material of the enclosure 3 distributes itself locally in the boundary region between the fixing thread and the matrix. The enclosure 3 is formed from a suitable thermoplastic polymer material, for example from polyethylene, from polypropylene or the like, and has a small material thickness in relation to the diameter of the core thread 2, so that entry of the thermoplastic material into the matrix during the curing process is minimized. The curable polymer material or the resin system that can be cured in particular by crosslinking to form the matrix is, for example, an epoxy resin, a polyester resin, a BMI resin or the like.

(8) FIG. 2 and FIG. 3 show cross-sectional representations through alternative embodiments of the fixing thread according to the invention.

(9) The fixing thread 5 in FIG. 2 is formed in turn by a core thread 6 and an interface thread 7, which are bonded to each other in the region of a baseline 8, for example by fusing of the interface thread 7 or the like that is formed by a thermoplastic material. With preference, the core thread 6 and the interface thread 7 respectively have an approximately semicircular cross-sectional geometry, so that the fixing thread 5 has a substantially circular cross-sectional geometry. In this case, the interface thread 7 forms the actual interface 9, which according to the invention brings about the local increase in ductility in the region of the surrounding matrix, which is not represented. The core thread 6 is in turn a conventional fixing thread, for example a polyester filament or the like.

(10) The fixing thread 10 in the representation of FIG. 3 is formed by two core threads 11, 12 and two interface threads 13, 14. Here, the fixing thread 10 has a substantially circular circumferential contour, as indicated by the dotted circumferential line. The core threads 11, 12 are in turn conventional fixing threads, for example polyester filaments or the like. By contrast, the interface threads 13, 14 are formed by a thermoplastic material to form an interface 15, which likewise serves for the local increase in the ductility in the boundary region with respect to the matrix.

(11) FIG. 4 shows a plan view of a portion of a fourth variant of the fixing thread according to the invention. The fixing thread 16 has a core thread 17 and extends parallel to the plane of the drawing. The core thread 17 is wound around spirally by an interface thread 18 of a thermoplastic material to form a ductility-increasing interface 19. The winding may also take place, for example, with more than one layer, the winding direction changing from layer to layer.

(12) Instead of being formed by conventional fixing threads, which usually consist of a polyester material or the like, the core threads 2, 6, 11, 12 and 17 may also be formed at least partially by threads which consist of a thread material that can undergo high mechanical loads, so that, in addition to the actual fixing function within the fiber preform, the fixing threads formed in this way can absorb mechanical forces to an appreciable extent in the direction of the respective longitudinal axes of the fixing threads within the finished composite component. Bundles of individual glass fibers, carbon fibers or aramid fibers come into consideration, for example, as thread material that can withstand high loads.

(13) By contrast, in all the variants shown the interface threads 7, 13, 14 and 18 are formed by a thermoplastic material, for example by polypropylene, polyethylene or the like, in order to achieve the defined local increase in ductility of the matrix in the boundary region between the said matrix and the fixing thread that is aimed for by the invention.

(14) The fixing threads 1, 5, 10, 16 according to the invention may also be used, for example, for the production of continuous woven or nonwoven fabrics in strip form with fiber strands of reinforcing fibers, such as, for example, carbon fibers, glass fibers, aramid fibers or the like. Woven or nonwoven fabrics of this type are also referred to by the term sheet-like reinforcing formations. In this case, the fiber strands of reinforcing fibers that have been laid one on top of the other or interwoven are, for example, sewn together by means of the fixing threads 1, 5, 10, 16, and consequently secured against unwanted positional changes, etc.

(15) The invention accordingly relates to a fixing thread 1, 5, 10, 16 for sewing together reinforcing fibers, in particular to form a fiber preform, for the production of a fiber-reinforced composite component by means of impregnation with a curable polymer material, the fixing thread having an interface 4, 9, 15, 19, in particular for locally increasing the ductility of a matrix formed by the curable polymer material, and having at least one core thread 2, 6, 11, 12, 17.

(16) The core thread 2, 6, 11, 12 and 17 or the core threads 2, 6, 11, 12, 17 improve the processability of the interface 4, 9, 15, 19 and/or influence the mechanical properties of the composite component, for example.

(17) The core thread 2, 6, 11, 12 and 17 or the core threads 2, 6, 11, 12, 17 are preferably formed by a thread material ensuring adequate processability, in particular by a polyester material or the like.

(18) The core thread 2, 6, 11, 12, 17 or the core threads 2, 6, 11, 12, 17 are also preferably formed by a material that can undergo high mechanical loads, in particular by glass fibers, by carbon fibers, by aramid fibers or the like.

(19) The fixing thread 1, 5, 10, 16 advantageously has a substantially circular circumferential contour.

(20) The interface 4 is formed, for example, by an enclosure 3 around at least portions of at least one core thread 2 with a polymer material, in particular with a thermoplastic polymer material.

(21) The interface 9 is formed in particular by a bonding of at least one core thread 6 with an interface thread 7 of a polymer material, in particular of a thermoplastic polymer material.

(22) The interface 15 is also advantageously formed by a twisting of at least one core thread 11, 12 with at least one interface thread 13, 14 of a polymer material, in particular of a thermoplastic polymer material.

(23) Moreover, the interface 19 is formed, for example, by at least one core thread 17 being wound around by at least one interface thread 18 in strip form of a polymer material, in particular of a thermoplastic polymer material.

LIST OF REFERENCE NUMERALS

(24) 1 fixing thread 2 core thread 3 enclosure 4 interface 5 fixing thread 6 core thread 7 interface thread 8 baseline 9 interface 10 fixing thread 11 core thread 12 core thread 13 interface thread 14 interface thread 15 interface 16 fixing thread 17 core thread 18 interface thread 19 interface