MULTI-LEVEL-ARCHITECTURE MULTIFIBER COMPOSITE YARN

Abstract

A multi-level-architecture multi-fiber composite yarn includes a composite yarn having a first anisotropic expansion coefficient in an axial and/or radial direction, and a matrix material included with the yarn, wherein the matric material has a second anisotropic expansion coefficient that is different from the first anisotropic expansion coefficient in at least one of the axial or radial directions. A method of fabricating a multi-level-architecture multi-fiber composite yarn includes infiltrating a composite yarn having a first anisotropic expansion coefficient in an axial and/or radial directions with a matrix material having a second anisotropic expansion coefficient different from the first anisotropic expansion coefficient in the axial or radial direction.

Claims

1. A multi-level-architecture multi-fiber composite yarn, comprising a composite yarn having a first anisotropic expansion coefficient in an axial and/or radial direction, and a matrix material included with the yarn, wherein the matric material has a second anisotropic expansion coefficient that is different from the first anisotropic expansion coefficient in at least one of the axial or radial directions.

2. The composite yarn of claim 1 wherein the composite yarn comprises multiple continuous filament or staple fibers disperses in the matrix material to form a single yarn.

3. The composite yarn of claim 2 wherein the continuous filament or staple fibers are selected from a group comprising polyimide, polyester, polyethylene, polyamide, aliphatic polyesters, polylactic acid, poly(3-hydroxybutyrate-co-3-hydroxyvalerate), metal, ceramic or wool.

4. The composite yarn of claim 2 wherein the continuous filament or staple fibers are polyamide fibres.

5. The composite yarn of claim 2 wherein a plurality of continuous filaments or staple fibers are individually coated in the matric material, prior to being combined in the matric material.

6. The composite yarn of claim 5 wherein the individually coated filaments or fibers are combined by bundling the filaments or fibers and dipping the bundled filaments or fibres in a solution of the matric material, and are the dried to vulcanize the matric material.

7. The composite yarn of claim 1 wherein the matrix material is selected from a group comprising. poly(dimethylsiloxane), dimethicone, thermal plastic elastomeric olefin, polyurethane, ethoxyline, natural or synthetic rubber, mineral, responsive gel.

8. The composite yarn of claim 1 wherein the matrix material is poly(dimethylsiloxane).

9. The composite yarn of claim 1 wherein the expansion coefficient(s) is(are) one that is responsive to hydrothermal, electro-thermal, photo-thermal, hygral, chemical stimulation.

10. The composite yarn of claim 1 wherein the composite yarn comprises two more individually coated composite yarns included together by one of twisting, winding, plying, cabling or braiding, and the curing the included composite yarns.

11. A method of fabricating a multi-level-architecture multi-fiber composite yarn, comprising infiltrating a composite yarn having a first anisotropic expansion coefficient in an axial and/or radial directions with a matrix material having a second anisotropic expansion coefficient different from the first anisotropic expansion coefficient in the axial or radial direction.

12. The method of claim 11 wherein the multiple continuous filaments or staple fibers are individually coated in the matrix material, prior to being combined in the matric material.

13. The method of claim 12 wherein individually coating the multiple continuous filaments or staple fibers comprises dipping the individual filaments or fibres in a solution of the matric material, and drying the individual filaments or fibres in a drying oven to vulcanize the coating.

14. The method of claim 12 further comprising bundling the individually coated filaments or fibres, and further dipping the bundled filaments or fibres into the solution of the matric material to coat the bundled filaments or fibres, and drying the drying the bundled filaments or fibres in a drying oven to vulcanize the coating.

15. The method of claim 14 further comprising loading the coated bundle of filaments or fibres and twisting the bundle.

16. The method of claim 15 further comprising coiling the twisted bundle against a tool by either further twisting (homochirality), or heat setting prior to twisting in the opposite direction (heterochirality), or winding against a tool, and curing the coiled bundle in a curing oven at temperature

17. The method of claim 15 wherein curing in a curing oven comprising heating the bundle to 220 deg-C for one (1) hour.

18. The method of claim 11 further comprising selecting the fibers from a group comprising polyimide, polyester, polyethylene, polyamide, aliphatic polyesters, polylactic acid, poly(3-hydroxybutyrate-co-3-hydroxyvalerate), metal, ceramic or wool.

19. The method of claim 18 wherein selecting comprises selecting polyamide fibers.

20. The method of claim 11 further comprising selecting the matrix material from a group comprising. poly(dimethylsiloxane), dimethicone, thermal plastic elastomeric olefin, polyurethane, ethoxyline, natural or synthetic rubber, mineral, responsive gel

21. The method of claim 20 wherein selecting comprises selecting poly(dimethylsiloxane).

22. A multi-fiber composite yarn produced by a method according to the steps of claim 11.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The invention will now be described with reference to the accompanying drawings in which:

[0025] FIG. 1 is a cut-away section illustration of a multi-fibre composite yarn according to the invention,

[0026] FIG. 2 is a cross-section illustration of the multi-fibre composite yarn,

[0027] FIG. 3 is an illustration a twisted bundle of the filaments or fibres,

[0028] FIG. 4 is an illustration a twisted and coiled bundle of filaments or fibres,

[0029] FIG. 5 is an illustration of a braiding a composite yarn, and

[0030] FIG. 6 illustrates steps (a) through (h) of producing the twisted and coiled bundle of filaments or fibres of FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] Preferred embodiments of the invention will now be described to illustrate the invention. The terminology used is for illustrative purposes only and is not intended to limit the scope and/or use of the invention unless the context clearly requires otherwise.

[0032] FIG. 1 shows an exemplary of a multi-level-architecture multi-fiber composite yarn (MAMFCY) 10 having one or more, preferable multiple, composite yarns 11 included within a matrix material 12. The coated composite yarns 11 are each made by twisting or grouping multiple long continuous filament fibres, or by spinning and or twisting staple fibres together to make a cohesive single thread. In the preferred embodiment of the invention, two or more individual composite yarns are used and are combined by twisting, cabling (i.e. twisting together in the opposite direction to their individual twist direction), interlacing three of more strands in a braid, or other such techniques of combinations thereof as known in the art. The composite yarns 11 are each made from synthetic or natural fibers such as polyimide, polyester, polyethylene, polyamide, aliphatic polyesters like polylactic acid or poly(3-hydroxybutyrate-co-3-hydroxyvalerate), metal, ceramic or wool. The material of the composite yarns is chosen to give the yarns a first anisotropic expansion coefficient in an axial and/or radial direction.

[0033] The matrix material may be made from materials such as poly(dimethylsiloxane), dimethicone, thermal plastic elastomeric olefin, polyurethane, ethoxyline, natural or synthetic rubber, mineral or responsive gel. The material of the matrix material is chosen to give the matrix a second anisotropic expansion coefficient that is different from the first anisotropic expansion coefficient in at least one of the axial or radial directions.

[0034] In a preferred embodiment of the invention the yarns 11 comprise polyamide and the encasing matrix material 12 is poly(dimethylsiloxane). As shown in FIG. 2, a plurality of yarns 11, 11 etc. are dispersed evenly within the matrix material 12. The expansion coefficient of polyimide is 1.8810.sup.6K.sup.1(1.8810.sup.6K.sup.1) in the axial direction and 84510.sup.6K.sup.1 (84510.sup.6K.sup.1) in the radial direction at 50-230 deg-C. In contrast the expansion coefficient of poly(dimethylsiloxane) in all directions is about 60010.sup.6K.sup.1 (60010.sup.6K.sup.1) at 50-230 deg-C. Accordingly, when the MAMFCY is subjected to a temperature change the polyimide yarn exhibits greater stability in the axial direction than the poly(dimethylsiloxane) matrix resulting in an actuating stroke of the MAMFCY.

[0035] In a preferred embodiment of the invention the matrix material is applied to the composite fibers by multi-stage coating to build up layers of the matrix material on the yarns, and to consolidate the preferred plurality of yarns together. Coating of the fibers may be by any of a number of known methods, such as by dip-coating, die-coating, direct roll coating where coating liquid is rolled onto the fibres by a roller suspended in the coating solution, or any other known method that facilitates an even covering to the yarn. Other methods involve a Pad-Dry-Cure method where the fibres are submerged in the coating solution then the excess squeezed out in the rollers. Other possible methods of coating the fibres include Calendar Finishing, Hot melt extrusion coating and Foam finishing. Referring to FIG. 6(a) firstly, individual filament or staple fibers 11 are individually coated. The preferred method of coating the individual filament or staple fibers 11 is to apply the individual fibres 11 between the parallel arms of a C-shaped frame 13. As illustrated in FIG. 6(b) the frames and fibres are then dipped into a vessel 14 containing a matrix coating solution. In the preferred example, the matrix coating solution is a mixture of poly(dimethylsiloxane) (PDMS) and ethyl acetate (EA), with a ratio of 1:1 to 1:9 (PDMS:EA). The preferred ratio is 1:4 (PDMS:EA). The individual fibers are then dried on the frame in a drying oven to vulcanize the first layer of matrix coating on the individual fibres (FIG. 6(c)). The temperature range for oven drying is 80120 C., for a time range of between 1 hour and 6 hours. An optimally 80 C. for 3 hours. The individual coated filament or staple fibers 11, 11 etc are then combined into a multi-fiber yarn, as afore mentioned, and then dipped into the vessel 14 containing the coating solution (FIG. 6(d)) to coat the combine fibers in the matrix. The multi-stage coating disperses and consolidates the individual fibers in the matrix. The individually coated fibers 11, 11 etc. coating separately as shown in the cross section illustration of FIG. 2. The multi-fibre yarn 11a is then dried in a drying oven to vulcanize the final matrix coating (FIG. 6(e)). The temperature range for oven drying is again 80 to 120 C., for a time range of between 1 hour and 6 hours. An optimally 80 C. for 3 hours.

[0036] Referring to FIG. 6(f), the coated multi-fibre yarn 11a is then preferably twisted by fixing the yarn at a first end 15, and loading the yarn by suspending a weight 16 from a second end of the yarn. One end of the loaded yarn 11a is then turned to twist the yarn. Referring to FIG. 6(g), the twisted yarn is them coiled by any various known techniques but a preferred method includes coiling the single yarn against a tool by either further twisting (homochirality) or heat setting prior to twisting in the opposite direction (heterochirality). Finally, as illustrated in FIG. 6(h) the coiled yarn is then heat set in a curing oven at temperature for a period of time. Preferably the matrix is heat set at 220 deg-C for one (1) hour.

[0037] The MAMFCY according to the invention exhibits anisotropy or directional dimensional expansion/contraction of the composite yarns due to coupled mechanical deformation. The result is a composite fibre linear actuator that exhibits excellent performance, as well as flexibility, adjustability in actuating force and stroke, long lasting and outstanding environmental stability. The actuation is triggered by volume changes due to temperature/humidity changes and can be powered by, for example, hydrothermal, electro-thermal, photo-thermal, hygral or chemical stimulation. The MAMFCY can be designed to work under different conditions with sufficient force and actuating stroke by choice of the relative expansion coefficients of the yarn and matrix material.

[0038] In yet a further example of the invention, a final coating biocompatible component (e.g. silicone) could be applied if the actuator need to be implanted to the body of living beings as an artificial muscle. Alternatively, polyimide yarn could be chosen to meet the requirement of thermal stability when the actuator is used under high-temperature condition for waste heat recovery in industrial process.