Fabric reinforced with carbon nanostructures to improve mechanical performance

Abstract

Fabrics that have unique mechanical properties are comprised of fibers that have been reacted to provide carbon nanostructures covalently grafted to these fibers so that the entanglement and/or the reactive bonding between adjacent fibers creates a hierarchal structure reinforcement of the fabric. This entanglement and/or reactivity is also effective for developing reinforcement between plies of structural fabric composites in order to enhance inter-laminar shear strength and mechanical properties.

Claims

1. A fabric comprising: fibers functionalized so as to have adhered reactive functional groups reacted with functionalized carbon nanostructures become covalently grafted to the fiber and become part of the fibers' intrinsic structure.

2. The fabric according to claim 1 wherein the fibers are drawn from a group consisting essentially of: filaments; threads; and tow.

3. The fabric according to claim 1 wherein the fibers, and any yarn made therefrom, are drawn from a group consisting essentially of: natural; and synthetic.

4. The fabric according to claim 1 wherein the fibers are made into the fabric by processes drawn from a group consisting essentially of: spinning; weaving; and drawing.

5. The fabric according to claim 1 wherein the fibers are functionalized by processes drawn from a group consisting essentially of: chemicals; and plasma.

6. The fabric according to claim 1 where the functional groups on the fiber are drawn from a group consisting essentially: hydroxyl; carboxyl; and amine.

7. The fabric according to claim 1 wherein the carbon nanostructures with which the functional groups on the fiber are reacted are drawn from a group consisting essentially of: carbon nanotubes; carbon nanoparticles; graphene; carbon nanoribbons; and graphene oxide.

8. The fabric according to claim 1 wherein the functionalized carbon nanostructures are further reacted to form more complex nanostructures consisting of two or more joined nano carbons both grafted to the fiber.

9. The fabric according to claim 8 wherein the formed complex nanostructures are drawn from a group consisting essentially of: straight nanostructures; and branched nanostructures.

10. The fabric according to claim 8 wherein the formed complex nanostructures grafted to a fiber are of sufficient size to entangle with adjacent nanostructures from neighboring fibers developing an entangled network.

11. The fabric according to claim 8 wherein the complex nanostructures have a terminal carbon nanostructure; and wherein these terminal nanocarbon structure on the complex nanostructures are reactive and react with adjacent reactive nanocarbon groups to covalently link fabric fibers and/or adjacent plies into a composite structure.

12. Soft armor constructed with fabric according to claim 1, 5, or 8.

13. A composite structure constructed with fabric according to claim 1, 5, or 8.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0040] FIG. 1 is an illustration of the nanocarbon materials that are used to develop the inventive products which includes functionalized CNT and graphene and naturally functional graphene oxide.

[0041] FIG. 2 is a plan view showing is the Plasma treated woven fabric illustrating various plasma generated functional groups that are easily applied to fabrics and are useful for the invention.

[0042] FIG. 3 is an illustration of the chemical synthesis used to provide isocyanate functionality to carbon nanotubes.

[0043] FIG. 4 shows the CNT bonded to the fabric with a schematic of the chemical synthesis used for this reaction.

[0044] FIG. 5 shows the attachment of the graphene platelet to the Fabric/CNT structure and the chemical synthesis method.

[0045] FIG. 6 illustrates the entanglement of carbon nanostructures on a fiber with the carbon nanostructures on an adjacent fabric fiber.

[0046] FIG. 7 illustrates the entanglement between the nanostructures on a ply of fabric with the nanostructure on an adjacent fabric ply.

[0047] FIG. 8 is an illustration of connection between different fibers in the fabric, or different plies in a laminate that are covalently joined to couple the fibers and/or the plies together.

DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION

[0048] The fabric may be constructed of at least one of fibers, yarns or tow. Examples of fibers include, but are not limited to, Fiberglass, carbon, nylon, polyaramid, polyester, polyurethane, polynitriles, polyethylene, polypropylene, polyvinylchloride, polystyrene, polyacrylonitrile, polytetrafluoroethylene, polymethyl methacrylate, polyvinyl acetate, or natural fibers. Preferably, the fabric is constructed of polyaramid, known as Kevlar, or Ultra high Molecular Weight Polyethylene (UHMWPE) known as Spectra and Dyneema which is commonly used to produce anti-ballistic body armor; or for structural composites made from glass, carbon, or other reinforced composite fiber.

[0049] The fabric is functionalized by chemical, additive, or plasma methods to provide chemically reactive sites on the fabric strands which will allow covalent attachment of nano- or micro-particles, including, but not limited to, carbon nanotubes (CNTs), graphene, graphene oxide, graphene nano ribbons that can be used separately or in combination. The CNTs may be single-walled or multi-walled, and the graphene materials maybe single, few or multilayered. In a preferred embodiment, the fabric is plasma functionalized which can provide several reactive moieties including, but not limited to, hydroxyl, carboxyl and amine, which are capable of covalent reaction with functionalized nanoparticles including carbon nanotubes, graphene, and graphene oxide. By further reaction, the nanoparticles and nanostructures are covalently attached to the fabric and each other.

[0050] Functional carbon Nano particles. Gas plasma functionalized graphene and carbon nanotubes were purchased from Cheap Tubes Inc. and used as received. These materials were gas plasma functionalized. Carbon nanotubes (110) and graphene (120) with —OH (hydroxyl), COOH carboxyl) and —NH2 (amine) functional groups were obtained. Graphene oxide (130) was not purchased, but is widely available to use a substitution for graphene in the invented nanostructures. An illustration of these materials is shown in FIG. 2.

[0051] 1. Functionalization of Fabrics

[0052] The fabrics (200) for development of the examples and test coupons were functionalized by gas plasma (210) at Plasmatreat in Belmont Calif. The gases used to treat the fabrics were ammonia to provide amine functionality and carbon dioxide to provide hydroxyl functionality, Carboxyl functionality is accomplished with vapor of acetic acid. The dwell time in the plasma determined the extent of functionalization. FIG. 2 is a plan view of the plasma treated fabric showing the functionalization that can be accomplished with gas plasma treatment. The breakout illustration shows woof (211) and warp (212) fibers that have been gas functionalized (213).

[0053] 2. Isocyanate Functional Carbon Nanotubes

[0054] Both hydroxyl and carboxyl functional CNT readily react with isocyanate. To synthesize isocyanate functional CNT (310), hydroxyl functional CNT (110) was reacted with Toluene Di-isocyanate (TDI) in solvent solution. TDI was chosen because of the higher reaction rate of the ortho isocyanate group allow the TDI to be reacted onto the CNT with the para isocyanate, which is sterically hindered and requires greater activation energy, unreacted and viable for further reaction, This reaction is shown below and in FIG. 3.

[0055] R—OH+1(CH3),2,4(NCO)C6H3------1(CH3),2NCO,4NHCOOC6H—R-4,OOCNH1,(CH3)C6H3,2,NCO

[0056] 3. Covalent Bonding of CNT to Plasma Functionalized Fabric

[0057] The para isocyanate group can be readily reacted to hydroxyl functional fabric with increased temperature or catalyst to form a urethane linkage. In FIG. 4 this reaction is illustrated. Woof (211) and warp (212(adjacent fibers in the same fabric with hydroxyl functionality R—OH (213) available to react with the isocyanate groups on the di-functional CNT represented below as OCN—R—CNO This isocyanate will also react with amine groups (R—NH2) very readily without heat or catalyst to form a urea linkage. Control of this reaction is achieved by providing equimolar portions of both reactants. Both of these reactions are illustrated in FIG. 4.

[0058] FIG. 5 is an illustration of CNT grafted onto fibers to illustrate the potential of CNT to entangle at woof/warp junctions to increase the strength and modulus of the fabric. The reaction between the hydroxyl and the isocyanate (501) is shown, as the unreacted isocyanate (502) is also shown.

[0059] 4. Addition of Graphene to Fabric/CNT

[0060] The reaction of the graphene platelet to the Fabric/CNT is the same as the reaction shown in FIG. 4 wherein the amine functional graphene platelet forms a urea linkage with the remaining isocyanate group on the CNT (601) that has been adhered to the fabric. In the case where graphene oxide is substituted for functionalized graphene, the addition of graphene oxide platelets to the CNT/fabric is also achieved by urethane reaction between the CNT isocyanate and the hydroxyl groups present on graphene oxide. This is the reaction illustrated in FIG. 4. As is shown in FIG. 6, the larger, flat grapheme particle (120) is attached covalently to the carbon nanotube, or nanoribbon, (110) for the purpose of developing a stronger entanglement. The CNT diameter is generally between 10 and 50 nanometers in diameter and having a length of up to several tens of microns, while the size of the graphene platelet may be tens if microns in diameter. This structure will produce a more entangled “knot” tying the structure together and making it much stronger than the structure of nanotubes as shown in FIG. 5. This effect is easily demonstrated on the macro level by first entangling a comb of strings attached to wands and then separating them, followed by the same experiment having tied disks to the ends and sides of the strings and attempting to separate them.

[0061] Besides being applicable to reinforcing fibers in a single layer of fabric, this same technique will provide reinforcement between plies of fabrics as shown in FIG. 7. In this instance, the lower ply (710) is connected to a CNT/graphene structure (600), as is the top ply (720). In this case, depending on characteristics of the laminate it may be necessary to construct the nanostructure with longer nanotubes, or graphene nano ribbons, both of which are commercially available. A fabric so constructed will provide major performance enhancement to advanced composite structures in current use for aerospace, aircraft, and vehicle structure by not only strengthening the composite fabric, but also significantly improving the inter laminar shear strength.

[0062] As shown in FIG. 8, the entire structure between fibers in an individual fabric or between fabric plies in a laminate can be completely joined together by further reacting the residual amine groups on (700) nanostructure with a poly functional isocyanate or epoxide (801). In the case of Polymer composited these amine groups could also react into the matrix resin. This further improves the composite mechanical properties.

[0063] These described reactions are exemplary of method to attach and construct a nanostructure to fabrics. As will be obvious to those skilled in the art that a myriad of other reactions can take place to construct similar product. It is also important to note that carbon nanotubes are available in various lengths, as are carbon nano ribbons produced from graphene. The longer nanostructures will likely perform better in improving properties of nanocomposites.

[0064] This invention contemplates carbon nanostructures that are used to enhance strength, modulus, inter laminar shear and other mechanical and physical properties through the entanglement of adjacent fibers and adjacent plies of laminated material. These entanglements are designed to develop hierarchal structure binding thread, fiber, fabric, and laminate plies the function in body armor, tensile fabrics, rope etc. is without a binding matrix. The use of the invented structure in composite structures is with a matrix material that could be polymer resins, ceramics or metals.