# US 8,772,187 B2 · Auxetic fabric structures and related fabrication methods > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,772,187 B2 - Document ID: US8772187B2 - Status: Granted - Kind: B2 - Application number: 12/665,166 - Filed: 2008-06-23 - Published: 2011-02-24 - Granted: 2014-07-08 - Earliest claimed: 2007-06-21 - Assignees: University of Massachusetts - Applicants: Samuel C. Ugbolue; Yong K. Kim; Steven B. Warner; Qinguo Fan; Chen-Lu Yang; Olena Kyzymchuk - Inventors: Samuel C. Ugbolue; Yong K. Kim; Steven B. Warner; Qinguo Fan; Chen-Lu Yang; Olena Kyzymchuk - Web page: https://patentgrep.com/patent/US8772187B2 ## CPC - D04B 21/12: characterised by thread material - D10B 2401/061: elastic - Y10T 442/10: Scrim [e.g., open net or mesh, gauze, loose or open weave or knit, etc.] - Y10T 442/40: Knit fabric [i.e., knit strand or strip material] - Y10T 442/45: Knit fabric is characterized by a particular or differential knit pattern other than open knit fabric or a fabric in which the strand denier is specified - D04B: KNITTING - D10B: INDEXING SCHEME ASSOCIATED WITH SUBLASSES OF SECTION D, RELATING TO TEXTILES - Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION ## Abstract Auxetic fabric structures, of the sort which can be useful in conjunction with composite materials, and related methods of fabrication. ## Claims ### Claim 1 An auxetic warp knitted fabric having a net structure, the net structure comprising: a first chain of connected diagonal ribs, the first chain extending along a course direction, wherein adjacent diagonal ribs of the first chain extend along different diagonal directions and are connected at a valley or a peak of the first chain, and wherein each of the diagonal ribs of the first chain forms an angle α relative to the course direction; a second chain of connected diagonal ribs, the second chain extending along the course direction, wherein adjacent diagonal ribs of the second chain extend along different diagonal directions and are connected at a valley or a peak of the second chain, and wherein each of the diagonal ribs of the second chain forms the angle α relative to the course direction; and vertical ribs extending along a wale direction perpendicular to the course direction, wherein the diagonal ribs of the first and second chains and the vertical ribs each comprises one or more yarns forming warp knit stitches that comprise loops of the yarns, wherein the loops are intermeshed and the intermeshed loops extend along a course direction or a wale direction, wherein each vertical rib connects a peak of the first chain to a valley of the second chain, and wherein at least some of the valleys of the first chain and some of the peaks of the second chain are unconnected and separated by gaps along the wale direction; wherein in a relaxed state, the angle α is a non-zero angle, and the fabric comprises a width along the course direction and a length along the wale direction; wherein when the fabric is stretched along either the course direction or the wale direction, the diagonal ribs of the first and second chains move towards aligning with the course direction and the angle α decreases from nonzero towards zero so that each chain becomes longer along the course direction and the width of the fabric increases, and the gaps between the unconnected valleys of the first chain and peaks of the second chain expand along the wale direction so that the length of the fabric increases in response to the stretch; and wherein the fabric has a Poisson's ratio with a value that is less than or equal to 0. ### Claim 2 (depends on 1) The auxetic warp knitted fabric of claim 1 providing an effective negative Poisson's ratio value ranging from 0 to about −5. ### Claim 3 (depends on 2) The auxetic warp knitted fabric of claim 2 wherein said Poisson's ratio value ranges from 0 to about −1. ### Claim 4 (depends on 1) The auxetic warp knitted fabric of claim 1 wherein said one or more yarns are selected from natural fibers, manufactured fibers and combinations thereof. ### Claim 5 (depends on 1) The auxetic warp knitted fabric of claim 1 wherein the fabric is free of any elastic yarns. ### Claim 6 (depends on 1) The auxetic warp knitted fabric of claim 1 further comprising an in-lay structure between at least some loops of the first or second chain, wherein the in-lay structure comprises an elastic yarn component that comprises a multi-filament configuration. ### Claim 7 (depends on 1) The auxetic warp knitted fabric of claim 1 comprising a construction selected from single layer, tubular and multi-layer constructions. ### Claim 8 (depends on 7) The auxetic warp knitted fabric of claim 7 wherein said construction is selected from single and multi-layer constructions, and said fabric is incorporated into a composite comprising said fabric coupled to a substrate component. ### Claim 9 (depends on 8) The auxetic warp knitted fabric of claim 8 wherein said composite is incorporated into one of a compression bandage, an intravascular bandage, and an intravascular stent. ### Claim 10 (depends on 1) A auxetic warp knitted fabric of claim 1 wherein the fabric is obtainable by a warp knitting process using at least three guide bars, and wherein the number of fully set guide bars is selected from 0 and 1. ### Claim 11 (depends on 10) The auxetic warp knitted fabric of claim 10 comprising a fillet warp knitted net structure. ### Claim 12 (depends on 11) The auxetic warp knitted fabric of claim 11 wherein 0 to 1 guide bars are fully-set and between 2 and about 8 guide bars are partially-set. ### Claim 13 (depends on 10) The auxetic warp knitted fabric of claim 10 comprising an inlay warp knit fabric. ### Claim 14 (depends on 13) The auxetic warp knitted fabric of claim 13 wherein the inlay warp knit fabric is formed using at least three guide bars, one said guide bar being partially-set and another guide bar being fully-set. ### Claim 15 (depends on 10) The auxetic warp knitted fabric of claim 10 wherein the fabric provides an effective negative Poisson's ratio value ranging from 0 to about −1, said Poisson's ratio value being dependent on at least one of tricot course length and chain course length. ### Claim 16 (depends on 10) The auxetic warp knitted fabric of claim 10 wherein the fabric is free of any elastic yarns. ### Claim 17 A method of using a warp knitting technique to fabricate an auxetic warp knitted fabric having a net structure, said method comprising: fully setting at least one guide bar of a plurality of guide bars of a warp knitting apparatus; partially setting at least one guide bar of the plurality of guide bars; forming a first chain of connected diagonal ribs, the first chain extending along a course direction, wherein adjacent diagonal ribs of the first chain extend along different diagonal directions and are connected at a valley or a peak of the first chain, and wherein each of the diagonal ribs of the first chain forms an angle α relative to the course direction; a second chain of connected diagonal ribs, the second chain extending along the course direction, wherein adjacent diagonal ribs of the second chain extend along different diagonal directions and are connected at a valley or a peak of the second chain, and wherein each of the diagonal ribs of the second chain forms the angle α relative to the course direction; and vertical ribs extending along a wale direction perpendicular to the course direction, wherein the diagonal ribs of the first and second chains and the vertical ribs each comprises warp knit stitches comprising loops from one or more yarns, wherein the loops are intermeshed and the intermeshed loops extend along a course direction or a wale direction, wherein each vertical rib connects a peak of the first chain to a valley of the second chain, and wherein at least some of the valleys of the first chain and some of the peaks of the second chain are unconnected and separated by gaps along the wale direction; wherein in a relaxed state, the angle α is a non-zero angle, and the fabric comprises a width along the course direction and a length along the wale direction; wherein when the fabric is stretched along either the course direction or the wale direction, the diagonal ribs of the first and second chains move towards aligning with the course direction and the angle α decreases from nonzero towards zero so that each chain becomes longer along the course direction and the width of the fabric increases, and the gaps between the unconnected valleys of the first chain and peaks of the second chain expand along the wale direction so that the length of the fabric increases in response to the stretch; and wherein the fabric has a Poisson's ratio with a value that is less than or equal to 0. ### Claim 18 (depends on 17) The method of claim 17 wherein fabric comprises an auxetic inlay warp net structure. ### Claim 19 (depends on 18) The method of claim 18 wherein the inlay warp knit auxetic structure is fabricated using a—vertical and b—horizontal elastomeric filling yarn. ### Claim 20 (depends on 17) The method of claim 17 wherein the one or more yarns are selected from natural fibers, manufactured fibers and combinations thereof.