Ultra-high volume fraction carbon nanotube yarn composite laminates and methods

Abstract

Composite materials that include compressed carbon nanotube yarns, a carbon nanotube aerogel, and a resin. The carbon nanotube aerogel may be at least partially corrugated, and arranged between pluralities of compressed carbon nanotube yarns. Methods of forming composite materials that include compressing a precursor including carbon nanotube yarns and a carbon nanotube aerogel to reduce or eliminate internal voids defined by the carbon nanotube yarns.

Description

ULTRA-HIGH VOLUME FRACTION CARBON NANOTUBE YARN COMPOSITE LAMINATES AND METHODS

[0001] Cross-reference to Related Applications

[0002] This application claims priority to U.S. Provisional Patent Application No. 63 / 586,132, filed September 28, 2023, which is incorporated by reference herein.

[0003] Statement Regarding Federally Sponsored Research and Development

[0004] This invention was made with government support under contract no.NNX17AJ32G, awarded by the National Aeronautics and Space Administration. The government has certain rights in the invention.

[0005] Field of the Disclosure

[0006] This disclosure relates to methods of making composite materials, and composite materials that include carbon nanotube materials, such as carbon nanotube yams.

[0007] Background

[0008] The strength of a fiber composite, such as a carbon fiber (CF) composite, usually is a function of the ratio between the reinforcing fibers and a resin, which may be referred to as a reinforcement volume fraction.

[0009] Typically, increasing the amount of reinforcing fibers in a composite material increases the strength of the composite material. The volume fraction of CFs that may be present in a composite material is usually limited for one or more reasons, such as the geometry of the carbon fibers. For example, carbon fibers are usually circular in crosssection, which may limit the maximum theoretical volume fraction to about 76%.

[0010] The function of a resin in a composite material may include transferring load between fibers; therefore, it can be advantageous for a resin to fully wet the surfaces of the fibers, which realistically limits the maximum volume fraction of carbon fibers in carbon fiber composites to about 60%. This limit can cause a significant reduction in mechanical properties. For example, IM7 fibers have a strength of 5688 MPa, however, an IM7 60 vol% composite material has a strength of only 2723 MPa, which is a reduction of about 52% (Hexcel Corporation, “HexTow IM7 Carbon Fiber.” 2020).

[0011] Carbon nanotube yarns have emerged as an alternative to carbon fibers as a structural reinforcement material, particularly for aerospace primary and secondary structures(see, e.g., J. A. Samareh et al., Nanotechnology, vol. 28, no. 37, p. 372001, Sep. 2017). So far, most work with CNT fibers has been limited to additions to CF (see, e.g., E. Bekyarova et al., Langmuir, vol. 23, no. 7, pp. 3970-3974, Mar. 2007), additions to resins (see, e.g., M. H. Kirmani, et al. ACS Appl. Nano Mater., vol. 4, no. 3, pp. 2476-2485, Mar. 2021), or specimens too small to be industrially relevant.

[0012] FIG. 1 depicts a set of typical cross sections from a 2-ply CNT yam supplied by Nanocomp Technologies, Inc. (now part of Huntsman Advanced Materials). FIG. 1A shows a section of the yarn with both plies intact and large voids defined by one of the plies and large cracks in both. FIG. IB and FIG. 1C show a cross section from the same roll of yam about 2 cm away from the area shown in FIG. 1A. The plies have separated, and the ply in FIG. IB defines large voids, while the ply in FIG. 1C is solid; both plies have very irregular cross sections.

[0013] The irregular cross sections can complicate traditional composite manufacturing processes, and / or reduce the achievable volume fraction, typically because the CNT yams cannot be packed as closely as CFs. Additionally, the larger size of CNT yarns (which may have a diameter of about 100 pm) compared to CFs (which may have a diameter of about 5 pm) can cause the resin rich areas in CNT yam-containing composites to be much larger than in CF-containing composites.

[0014] Previous work with large scale CNT yams has resulted in composite overwrapped pressure vessels (see, e.g., J.-W. Kim et al., “Structural CNT Composites Part II: Assessment of CNT Y ams as Reinforcement for Composite Overwrapped Pressure Vessels”), or laminates made with unaligned CNT sheets (see, e.g., C. Jolowsky, et al., Composites Science and Technology, vol. 166, pp. 125-130, Sep. 2018). Eaminates have been made with CNT yarns, and a stretching procedure has been used to increase the alignment of the CNTs (see, e.g., U.S. Patent No. 10,967,587 and U.S. Patent No. 10,967,587).

[0015] There remains a need for composite materials, and methods for making composite materials, that include increased volume fractions of CNT materials.

[0016] Brief Summary

[0017] Provided herein are embodiments of methods that may achieve ultra-high volume fraction CNT yarn composites via microstructure modification processes, which may include incorporating a CNT aerogel and performing a high-pressure densification. The volume fraction used in most CF composites is about 60% or less, but embodiments of theprocesses provided herein produce composite materials with ultra-high reinforcement concentrations of at least 85%, or at least 90%. Also provided herein are composite materials that include an ultra-high volume fraction of CNT yams.

[0018] In one aspect, methods of forming composite materials are provided. In some embodiments, the methods include providing a precursor composite material that includes a first plurality of CNT yarns, a second plurality of CNT yams, and at least one CNT aerogel arranged between the first plurality of CNT yams and the second plurality of CNT yams; and compressing the precursor composite material with a force to form a compressed composite material. The force may be effective to reduce a volume of internal voids defined by the first plurality of CNT yams and the second plurality of CNT yams. The methods may include contacting the compressed composite material and a resin to form an uncured composite material. The methods also may include curing the resin to form embodiments of the composite materials.

[0019] In some embodiments, the methods include providing a first and a second uncured composite material as described herein; and arranging the second uncured composite material on and optionally in contact with the first uncured composite material. The methods also may include curing the resin after the arranging of the second uncured composite material on and optionally in contact with the first uncured composite material.

[0020] In some embodiments, the methods include arranging a first compressed composite material on and optionally in contact with a second compressed composite material, and contacting a resin and the first and second compressed composite materials. The resin then may be cured, as described herein.

[0021] In another aspect, composite materials are provided. In some embodiments, the composite materials include a first ply that includes a first plurality of compressed CNT yams, a second plurality of compressed CNT yarns, at least one first CNT aerogel, and a cured resin. The at least one CNT aerogel of the first ply may be at least partially corrugated and arranged between the first plurality of compressed CNT yams and the second plurality of compressed CNT yarns. The first plurality of compressed CNT yarns and the second plurality of compressed CNT yarns may be free of internal voids or define internal voids of a volume less than those in identical, non-compressed CNTs. The cured resin may at least partially coat the first ply, at least partially impregnate the first ply, or a combination thereof. The composite materials may include one or more additional plies, such as a second ply that includes a third plurality of compressed CNT yarns, a fourth plurality of compressed CNT yams, at least one second CNT aerogel, and the cured resin.

[0022] Additional aspects will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the aspects described herein. The advantages described herein may be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive.

[0023] Brief Description of the Drawings

[0024] FIG. 1A is a scanning electron microscopy (SEM) image of a 2-ply CNT yarn used as a starting material in embodiments of the methods herein.

[0025] FIG. IB is an SEM image of a first ply separated from the 2-ply yam depicted at FIG. 1A.

[0026] FIG. 1C is an SEM image of a second ply separated from the 2-ply yam of FIG. 1A.

[0027] FIG. 2A— FIG. 2F are schematics of an embodiment of layup procedure.

[0028] FIG. 2A depicts an embodiment of a first plurality of CNT yarns laid up at, or less than, half of a desired ply density.

[0029] FIG. 2B depicts an embodiment of a CNT sock arranged on the CNT yams depicted at FIG. 2A.

[0030] FIG. 2C depicts an embodiment of a second plurality of CNT yams arranged on the CNT sock depicted at FIG. 2B.

[0031] FIG. 2D depicts the results of an embodiment of a densification procedure, which consolidates both pluralities of CNT yarns to a single ply, wherein the CNT sock is woven between the CNT yarns.

[0032] FIG. 2E depicts an embodiment of a resin added to the ply depicted at FIG.2D.

[0033] FIG. 2F depicts an embodiment of a product formed by two plies depicted at FIG. 2E.

[0034] FIG. 3 is a photograph of an embodiment of a plurality of CNT yarns arranged on an embodiment of a CNT sock.

[0035] FIG. 4A is an SEM image of a CNT yam laminate prepared without high- pressure densification.

[0036] FIG. 4B depicts an embodiment of a CNT yarn laminate subjected to a high- pressure densification at a pressure of 234 MPa.

[0037] FIG. 5 depicts an embodiment of an apparatus / method for densifying composite materials.

[0038] FIG. 6A is a photograph of an embodiment of unidirectional CNT yams before densification.

[0039] FIG. 6B is a photograph of the unidirectional CNT yams depicted at FIG. 6A after densification.

[0040] FIG. 6C is a photograph of an embodiment of CNT yarns arranged perpendicularly before densification.

[0041] FIG. 6D is a photograph of the pluralities of CNT yams depicted at FIG. 6C after densification.

[0042] FIG. 7A— FIG. 7F are schematics of an embodiment of a multidirectional ply layup process.

[0043] FIG. 7A depicts an embodiment of a square mold with a shim on a filament winder.

[0044] FIG. 7B depicts an embodiment of a ply including a plurality of 0° CNT yams / CNT sock wound on the square mold depicted at FIG. 7A.

[0045] FIG. 7C depicts an embodiment of a ply including a plurality of 90° CNT yams / CNT sock wound on the square mold depicted at FIG. 7A, and over the 0° CNY yams / CNT sock of FIG. 7B.

[0046] FIG. 7D depicts the plies of FIG. 7B and FIG. 7C after densification.

[0047] FIG. 7E depicts an embodiment of a thin film of a resin applied to the plies ofFIG. 7B and FIG. 7C.

[0048] FIG. 7F depicts an embodiment of a cured [0 / 90] product, which may be removed from the mold of FIG. 7A.

[0049] FIG. 8 is an SEM image (cross section) of an embodiment of a single ply unidirectional laminate.

[0050] FIG. 9 is an SEM image (cross section) of an embodiment of a unidirectional laminate featuring 12 layers of CNT yarns and 14 layers of CNT sock.

[0051] FIG. 10A is an SEM image (cross section) of an embodiment of a [0 / 90 / +45 ]slaminate.

[0052] FIG. 10B is an SEM of the laminate of FIG. 10A at greater magnification.

[0053] FIG. 11A is a plot of a thermogravimetric analysis (TGA) of an embodiment of a unidirectional laminate.

[0054] FIG. 11B is a plot of a TGA analysis of an embodiment of a quasi-isotropic laminate.

[0055] Detailed Description

[0056] Provided herein are composite materials and methods of forming composite materials, such as composite materials that include an ultra-high volume of CNT materials, such as CNT yarns.

[0057] Methods

[0058] In some embodiments, the methods include providing a precursor composite material, and compressing the precursor composite material with a force to form a compressed composite material.

[0059] The precursor composite material may include a first plurality of CNT yarns, a second plurality of CNT yams, and at least one CNT aerogel arranged between the first plurality of CNT yams and the second plurality of CNT yams. The at least one CNT aerogel may be arranged between and in contact with one or both of the first and second pluralities of CNT yams. In some embodiments, the methods include providing a CNT aerogel, and dispersing the CNT aerogel among and / or between CNT yams, which may increase the resulting composite materials’ laminate transverse strength.

[0060] A “plurality of CNT yams” (e. ., a first plurality of CNT yams, a second plurality of CNT yams, etc.) may include one or more CNT yarns arranged in any manner using any device. For example, a device, such as a mold see, e.g., FIG. 7), may have a first surface, and one or more CNT yarns may be arranged on the first surface to provide a plurality of CNT yams. The one or more CNT yarns may contact the first surface and optionally one or more other surfaces of the molds; for example, one or more CNT yams may be wound onto a mold to provide a “first” plurality of CNT yarns.

[0061] The precursor composite material also may include a resin arranged between the first plurality of CNT yarns and the second plurality of CNT yarns. The resin may be in contact with (i) the first plurality of CNT yarns, (ii) the second plurality of CNT yarns, (iii) the CNT aerogel, or (iv) a combination thereof. The resin may be in the form of a sheet.

[0062] Generally, any CNT yams may be present in the precursor composite materials and composite materials disclosed herein. The CNT yarns may include a spun CNT fiber material, an unspun CNT fiber material, or a combination thereof. CNT yams generally differ from CFs, because CNT yams typically have relatively large, highly irregular crosssections. The CNT yams may be formed by aligning and / or twisting a CNT sock or material obtained from a CNT sock.

[0063] The first plurality of CNT yarns may include two or more substantially parallel (± 5°) CNT yarns. The second plurality of CNT yams may include two or more substantially parallel (± 5°) CNT yams. As used herein, two or more yams are “substantially parallel” when the average deviation of the two or more yams from an axis of alignment is 5 ° or less, i.e., ±5 °C.

[0064] A first plurality of CNT yams and a second plurality of CNT yarns may be substantially unidirectionally arranged (± 5°), such as in the precursor composite material and / or the compressed composite material. As used herein, two or more pluralities of CNT yams are “substantially unidirectionally arranged” when the axis of alignment of the second plurality of CNT yams is oriented within 50or less, i.e., +5 °C, of the axis of alignment of the first plurality of CNT yarns.

[0065] A first plurality of CNT yams and a second plurality of CNT yarns may be substantially perpendicularly arranged (± 5°), such as in the precursor composite material and / or the compressed composite material. As used herein, two or more pluralities of CNT yams are “substantially perpendicularly arranged” when the axis of alignment of the second plurality of CNT yams is oriented within 50or less, i.e., ±5 °C, of an axis of alignment that is perpendicular to the axis of alignment of the first plurality of CNT yams.

[0066] Other relative orientations of the two or more pluralities of CNT yams are envisioned. In some embodiments, when the first and second pluralities of CNT yarns include substantially parallel CNT yams, then the first plurality of CNT yarns and the second plurality of CNT yams are arranged at an angle of about 0° to about 45°, about 0° to about 40°, about 0° to about 35°, about 0° to about 30°, about 0° to about 25°, about 0° to about 20°, about 0° to about 15°, or about 0° to about 10°, relative to each other.

[0067] Generally, any CNT aerogel may be present in the precursor composite materials and composite materials disclosed herein. The phrase “CNT aerogel”, as used herein, refers to an unaligned, two-dimensional network of CNTs, which may be obtained from any known source or process, such as a floating catalyst chemical vapor deposition process. Therefore, embodiments of CNT aerogels may be obtained directly from a tube furnace with minimal processing, in contrast to CNT yarns. The CNT aerogels also may be referred to herein and in the relevant literature as a CNT “sock”. A CNT aerogel may be very thin; for example, a CNT aerogel may have a thickness of about 10 pm or less, about 5 pm or less, about 3 pm or less, about 2 pm or less, or about 1 pm.

[0068] Generally, a force may be applied to a precursor composite material using any known technique and / or apparatus, such as a hydraulic press, and the force may include any type of force, such as a compressive force.

[0069] The force, such as a compressive force, may be effective to reduce a volume of internal voids defined by the first plurality of CNT yarns and the second plurality of CNT yams. The volume of internal voids defined by the first and second pluralities of CNT yarns may be reduced by any extent, such as about 20 % to 100 %, about 40 % to 100 %, about 60 % to 100 %, or about 80 % to 100 %. Additionally or alternatively, a high-pressure densification achieved by a force may increase the interface area between resin and yams, which can be the limiting factor in CNT yam composite materials (see, e.g., J.-W. Kim et al., Carbon, vol. 173, pp. 857-869; A. De Leon et al., Composites Science and Technology, vol. 222, p. 109375, May 2022).

[0070] In some embodiments, the methods include densifying the precursor composite material, via a high-pressure densification process, which may achieve a desired microstructure of CNT yarns in the compressed composite materials.

[0071] In some embodiments, the force is at least 50 MPa, at least 100 MPa, at least 150 MPa, at least 200 MPa, or at least 250 MPa. In some embodiments, the force is about 50 MPa to about 300 MPa, about 100 MPa to about 300 MPa, about 150 MPa to about 300 MPa, about 200 MPa to about 300 MPa, or about 250 MPa to about 300 MPa.

[0072] In some embodiments, the force is applied by a press, such as a hydraulic press. The hydraulic press may include one or more caul plates, one or more shims, a mold, or a combination thereof. In some embodiments, the providing of the precursor composite material includes providing a mold; and rotating the mold to wind onto the mold the first plurality of CNT yams, the second plurality of CNT yarns, and the at least one CNT aerogel. In some embodiments, the compressing of the precursor composite material includes arranging the mold in a press, such as a hydraulic press; and applying the force with the press.

[0073] In some embodiments, the methods include contacting a precursor composite material and a resin to form an uncured composite material, or a compressed composite material and a resin to form an uncured composite material. Two or more precursor composite materials and / or compressed composite materials may be arranged on and optionally in contact with each other before the two or more precursor composite materials are contacted with a resin.

[0074] The contacting of (i) the precursor composite material and / or (ii) the compressed composite material and the resin may be effective to (a) at least partially coat the precursor composite material and / or the compressed composite material with the resin, (b) at least partially impregnate the precursor composite material and / or the compressed composite material with the resin, or (c) a combination thereof. A material is “at least partially coated” with a resin when the resin contacts all or a portion of the material’s surface. A material is “at least partially impregnated” with a resin when the resin permeates all or a portion of the material’s sub-surface volume.

[0075] In some embodiments, the contacting of a precursor composite material and a resin includes arranging the resin between the first plurality of CNT yarns and the second plurality of CNT yams. The resin may be in contact with (i) the first plurality of CNT yarns, (ii) the second plurality of CNT yarns, (iii) the CNT aerogel, or (iv) a combination thereof. The resin may be in the form of a sheet.

[0076] The methods also may include curing a resin. The resin may be cured using manner or technique, and the curing may occur in one or more stages and at any one or more points of the methods described herein.

[0077] As explained herein, the composite materials may include a relatively high volume fraction of CNT yarns. In some embodiments, a volume fraction of CNT yarns in the precursor composite material, the compressed composite material, or the composite material is at least 70 %, at least 75 %, at least 80 %, at least 85 %, at least 90 %, at least 95 %, or at least 98 %.

[0078] The methods provided herein may be used to form composite materials having any number of plies. The number of plies may be selected to impart one or more desired properties to the composite materials, such as a desired thickness, durability, etc.

[0079] In some embodiments, the methods include providing a first uncured composite material; providing a second uncured composite material; and arranging the second uncured composite material on and optionally in contact with the first uncured composite material. The resin may be cured to form the composite material before or after the arranging of the second uncured composite material on and in contact with the first uncured composite material. The first uncured composite material and the second uncured composite material may have identical or different compositions. The methods also may include providing a third, fourth, fifth, etc. uncured composite material, and processing them in the foregoing manner to form a multi-ply composite material.

[0080] In some embodiments, the methods include providing a first compressed composite material; providing a second compressed composite material; arranging the second compressed composite material on and optionally in contact with the first compressed composite material; and contacting a resin and the first and the second compressed composite materials. The resin may be cured to form the composite material. The first compressed composite material and the second compressed composite material may have identical or different compositions. The methods also may include providing a third, fourth, fifth, etc. compressed composite material, and processing them in the foregoing manner to form a multi-ply composite material.

[0081] The first, second, third, fourth, fifth, etc. uncured or compressed composite materials may be oriented in any manner relative to each other. For example, when a first uncured composite material and a second uncured composite material include substantially parallel (± 5°) CNT yarns, the first uncured composite material and the second uncured composite material (and optionally the one or more additional uncured composite material(s)) are substantially unidirectionally arranged (± 5°). Other configurations are envisioned, however, including a first and a second uncured composite material that are arranged substantially perpendicularly to each other.

[0082] FIG. 2 depicts an overview of a possible layup for an embodiment of a 2-ply unidirectional CNT yarn laminate with the reinforcement orientation out of the page. FIG. 2A depicts an embodiment in which yams are laid at less than half of the desired density for a single ply. A layer of CNT aerogel may be placed on top of the yarns, as depicted in FIG. 2B. An additional layer of yam may be placed on top of the CNT sock, as depicted at FIG. 2C. An embodiment of the densification procedure is shown at FIG. 2D, which deforms the CNT yams and sock and can result in improved transverse strength from the CNT sock and increased density by deforming the yarns. FIG. 2E depicts an embodiment in which resin is added to the yarns. The resin may be cured to a B-stage, thereby completing the first ply.The densification process can allow this unidirectional ply to have greater reinforcement concentration than is possible with un-deformed reinforcement materials like carbon fibers, while retaining full wet-out of the reinforcement. In some embodiments, another unidirectional ply is laid on top of the first and then cured together to create a 2-ply unidirectional CNT yarn laminate, as shown in FIG. 2F.

[0083] As explained herein, CNT sock layers may be applied in any manner, such as by laying the CNT sock on a yam layer, and using an apparatus or device to gently stick them together. A CNT sock may be attracted to a yam by electrostatic forces. FIG. 3 is aphotograph of an embodiment of a CNT yarn layer 300 wrapped on top of a CNT sock layer 310. Also depicted are a mold 320 and a shim 330.

[0084] FIG. 4 shows a comparison of an embodiment of a CNT yarn laminate (a) without a high-pressure treatment and (b) compressed with 234 MPa. The compression can result in a significant densification of the yams, and / or a more uniform cross section.

[0085] FIG. 5 depicts an embodiment of an apparatus used in a hydraulic press. The apparatus includes outer steel caul plates 510, aluminum sheets 520, inner steel caul plates 530, outer steel shims 540, CNT yarns and sock 550, inner steel shims 560, and a steel mold 570.

[0086] Two steel caul plates (outer plate 510, inner plate 530) may be used with an aluminum sheet 520 in between them to act as a damper, and / or even out any misalignment in the press. In view of the small size of most CNT yarns, high accuracy may be desirable. An additional hardened steel shim may be placed between the yarns and the caul plates so that the yarns are less likely to be damaged by any irregularities in the caul plates, which may be polished to a smooth surface.

[0087] In some embodiments, up to 300 MPa is used to completely eliminate all internal voids and densify the yams. For large scale implementation, a roller can be used to allow for larger plies to be densified. FIG. 6 compares the visual effects of the densification treatment. FIG. 6A and FIG. 6B compare unidirectional CNT yarns before and after densification, and FIG. 6C and FIG. 6D compare [0 / 90] yarns before and after densification. After densification, differentiation between individual yarns can become difficult and the yams can reflect more light, likely due to the more uniform surface.

[0088] In addition to unidirectional laminates, multiple plies at different orientations can be laid up on the same mold. In some embodiments, a prepreg process is used to further layup plies into quasi-isotropic laminates.

[0089] Laminates can be laid up in any manner, such as by hand in whatever sequences are desired, since the prepregs are effectively 0° or [0 / 90] prepreg sheets. Additional thin films of resin can be added to the layup between each prepreg ply to increase interlaminar strength.

[0090] Composite Materials

[0091] Also provided herein are composite materials. In some embodiments, the composite materials include a first ply. The first ply may include a first plurality of compressed CNT yarns, a second plurality of compressed CNT yams, at least one first CNT aerogel, and a cured resin.

[0092] The at least one CNT aerogel may be at least partially corrugated see, e.g. , FIG. 2) and arranged between the first plurality of compressed CNT yarns and the second plurality of compressed CNT yarns. A CNT aerogel is “at least partially corrugated” when it at least a portion of the CNT aerogel defines alternating ridges and grooves. Each groove may be capable of accommodating a CNT yarn, as depicted at FIG. 2.

[0093] The first plurality of compressed CNT yams and the second plurality of compressed CNT yarns may be free of internal voids or define internal voids of a volume less than those in identical, non-compressed CNTs.

[0094] The cured resin generally may be present at any location of the composite materials, but, in some embodiments, the cured resin (i) at least partially coats the first ply, (ii) at least partially impregnates the first ply, or (iii) a combination thereof.

[0095] In some embodiments, (i) the first plurality of compressed CNT yarns includes two or more substantially parallel (± 5°) CNT yams, (ii) the second plurality of compressed CNT yams comprises two or more substantially parallel (± 5°) CNT yarns, or (iii) a combination thereof. In some embodiments, the first plurality of compressed CNT yams and the second plurality of compressed CNT yarns are substantially unidirectionally arranged (± 5°) in the composite material.

[0096] The composite materials generally may include one or more additional plies. The plies of the composite materials may be arranged in contact with each other in any manner; for example, the plies may be arranged on and in contact with each other. In some embodiments, the composite materials include a second ply including a third plurality of compressed CNT yarns, a fourth plurality of compressed CNT yarns, at least one second CNT aerogel, and the cured resin. The second ply may be arranged on and in contact with the first ply.

[0097] All referenced publications are incorporated herein by reference in their entirety. Furthermore, where a definition or use of a term in a reference, which is incorporated by reference herein, is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.

[0098] While certain aspects of conventional technologies have been discussed to facilitate disclosure of various embodiments, applicants in no way disclaim these technical aspects, and it is contemplated that the present disclosure may encompass one or more of the conventional technical aspects discussed herein.

[0099] The present disclosure may address one or more of the problems and deficiencies of known methods and processes. However, it is contemplated that various embodiments may prove useful in addressing other problems and deficiencies in a number of technical areas. Therefore, the present disclosure should not necessarily be construed as limited to addressing any of the particular problems or deficiencies discussed herein.

[0100] In this specification, where a document, act or item of knowledge is referred to or discussed, this reference or discussion is not an admission that the document, act or item of knowledge or any combination thereof was at the priority date, publicly available, known to the public, part of common general knowledge, or otherwise constitutes prior art under the applicable statutory provisions; or is known to be relevant to an attempt to solve any problem with which this specification is concerned.

[0101] In the descriptions provided herein, the terms “includes,” “is,” “containing,” “having,” and “comprises” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to.” When materials or methods are claimed or described in terms of “comprising” various steps or components, the materials or methods can also “consist essentially of’ or “consist of’ the various steps or components, unless stated otherwise.

[0102] The terms “a,” “an,” and “the” are intended to include plural alternatives, e.g., at least one. For instance, the disclosure of “a CNT yam”, “a resin”, and the like, is meant to encompass one, or mixtures or combinations of more than one CNT yam, resin, and the like, unless otherwise specified.

[0103] Various numerical ranges may be disclosed herein. When Applicant discloses or claims a range of any type, Applicant’s intent is to disclose or claim individually each possible number that such a range could reasonably encompass, including end points of the range as well as any sub-ranges and combinations of sub-ranges encompassed therein, unless otherwise specified. Moreover, all numerical end points of ranges disclosed herein are approximate. As a representative example, Applicant discloses, in some embodiments, that high-pressure densification may include compressing a laminate with a pressure of about 290 MPa to about 300 MPa. This range should be interpreted as encompassing about 290 MPa and about 300 MPa, and further encompasses “about” each of 291 MPa, 292 MPa, 293 MPa, 294 MPa, 295 MPa, 296 MPa, 297 MPa, 298 MPa, and 299 MPa, including any ranges and sub-ranges between any of these values.

[0104] As used herein, the term “about” means plus or minus 10 % of the numerical value of the number with which it is being used.

[0105] EXAMPLES

[0106] The present disclosure is further illustrated by the following examples, which are not to be construed in any way as imposing limitations upon the scope thereof. On the contrary, it is to be clearly understood that resort may be had to various other aspects, embodiments, modifications, and equivalents thereof which, after reading the description herein, may suggest themselves to one of ordinary skill in the art without departing from the spirit of the present disclosure or the scope of the appended claims. Thus, other aspects of this invention will be apparent to those skilled in the art from consideration of the specification and practice of the disclosure disclosed herein.

[0107] Example 1 - Preparation of Embodiments of Laminates

[0108] In this example, four [0 / 90] perpendicular plies (see FIG. 6) were used to make an embodiment of a [0 / 90 / +45]spanel.

[0109] FIG. 7 is a schematic of the layup process used for a [0 / 90] ply of this example. FIG. 7A shows an embodiment of a mold with shims held on by tape on a filament winding mandrel fixture. FIG. 7B shows an embodiment of a layer of yams and sock wrapped in the 0° direction. FIG. 7C shows the mold removed from the mandrel, tape removed, rotated 90°, reaffixed to the mandrel and another layer of yarns and sock wrapped. The can result is a [0 / 90] set of plies. FIG. 7D shows the mold and yams removed from the filament winder and densified. FIG. 7E shows a thin film of resin applied to the surface of the mold (resin is also applied to the reverse side as well). FIG. 7F shows the resin after heating to B stage and removal from the mold.

[0110] The laminate of this example was placed in between shims for curing, and the shims were taped closed for curing. There was no evident drawback to using excess resin because it flowed out of the laminate during curing.

[0111] FIG. 8 depicts a cross section of an embodiment of a single ply unidirectional laminate 800. The yarns 810 of FIG. 8 were deformed to have roughly rectangular shapes and there was a thin layer of resin (820, 830) between adjacent yarns 830 and on the outer surface of the yarns 820.

[0112] Multiple layers of CNT socks were woven between CNT yarns to increase the transverse strength of the laminate without a significant loss in longitudinal strength. FIG. 9 depicts an SEM cross section of a unidirectional laminate with 12 layers of CNT yarns and 14 layers of CNT sock. There was a large distance between each yarn to accommodate 12 layersin total, therefore after densification the yarns were not rectangular as in previous figures, but resin was still present between yarns.

[0113] An SEM cross section is shown in FIG. 10 with images of an embodiment of a [0 / 90 / ±45]slaminate. The low magnification image in FIG. 10A demonstrated the consistency in the process of this example. FIG. 10B shows that the yarns of this example were clearly deformed and had a layer of resin between them, as in the single ply unidirectional laminate shown in FIG. 8.

[0114] Thermal gravimetric analysis (TGA) was performed to validate that embodiments of the laminates had ultra-high volume fractions. FIG. 11 shows TGA results from embodiments of (a) unidirectional, (b) 0 / 90s, and (c) 0 / 90 / ±45squasi-isotropic laminates. TGAs were performed on a TA Q50 in air at a rate of 15 °C / min from 50 °C to 900 °C. By 500 °C, at which point the resin had degraded, the weight decrease of the laminates was 11% for the unidirectional and 17% for the quasi-isotropic. The results indicated very low resin concentration, much lower than what has been achievable with traditional carbon fiber.

[0115] Using the manufacturing processes provided herein, a specific tensile strength of up to 1.71 GPa / (g cm-3) and specific modulus of 256 GPa / (g cm-3) were achieved (C. E. Evers et al., “Scalable High Tensile Modulus Composite Laminates Using Continuous Carbon Nanotube Yams for Aerospace Applications,” ACS Appl. Nano Mater., p. acsanm.3c01266, Jun. 2023, doi: 10.1021 / acsanm.3c01266). The specific strength was identical to that of IM7 / epoxy while the specific modulus exceeded IM7 / epoxy by 147%.

[0116] The ultra-high volume fraction from the high-pressure yarn treatment was a contributor, if not the key contributor, to the improved properties of the CNT yarn laminates. The processes of this example were an effective approach to manufacture composite laminates with properties significantly beyond state-of-the-art carbon fiber composites.Generally, carbon fibers have had to be optimized for either strength or stiffness; CNT yams following these parameters combined high strength and high stiffness, opening an potential performance region in the Ashby chart for composite material applications.

[0117] EMBODIMENTS

[0118] The following is a non-limiting listing of embodiments of the disclosure:

[0119] Embodiment 1. A method of forming a composite material, the method comprising, consisting essentially of, or consisting of:

[0120] providing a precursor composite material, the precursor composite material comprising, consisting essentially of, or consisting of -

[0121] a first plurality of CNT yams,

[0122] a second plurality of CNT yarns, and

[0123] at least one CNT aerogel arranged between the first plurality of CNT yarns and the second plurality of CNT yarns; and

[0124] compressing the precursor composite material with a force to form a compressed composite material.

[0125] Embodiment 2. The method of Embodiment 1, wherein the force, such as a compressive force, is effective to reduce a volume of internal voids defined by the first plurality of CNT yams and the second plurality of CNT yams.

[0126] Embodiment 3. The method of Embodiment 2, wherein the force is at least 50 MPa, at least 100 MPa, at least 150 MPa, at least 200 MPa, or at least 250 MPa.

[0127] Embodiment 4. The method of Embodiment 2 or 3, wherein the force is about 50 MPa to about 300 MPa, about 100 MPa to about 300 MPa, about 150 MPa to about 300 MPa, about 200 MPa to about 300 MPa, or about 250 MPa to about 300 MPa.

[0128] Embodiment 5. The method of any one of Embodiments 1 to 4, wherein the force is applied by a press, such as a hydraulic press.

[0129] Embodiment 6. The method of Embodiment 5, wherein the hydraulic press comprises, consists essentially of, or consists of one or more caul plates, one or more shims, a mold, or a combination thereof.

[0130] Embodiment 7. The method of any of Embodiments 1 to 6, wherein the providing of the precursor composite material comprising, consists essentially of, or consists of -

[0131] providing a mold; and

[0132] rotating the mold to wind onto the mold the first plurality of CNT yams, the second plurality of CNT yams, and the at least one CNT aerogel.

[0133] Embodiment 8. The method of Embodiment 7, wherein the compressing of the precursor composite material comprises, consists essentially of, or consists of -

[0134] arranging the mold in a press, such as a hydraulic press; and

[0135] applying the force with the press.

[0136] Embodiment 9. The method of any of Embodiments 1 to 8, wherein the first plurality of CNT yams comprises two or more substantially parallel (± 5°) CNT yams.

[0137] Embodiment 10. The method of any of Embodiments 1 to 9, wherein the second plurality of CNT yams comprises two or more substantially parallel (± 5°) CNT yams.

[0138] Embodiment 11. The method of Embodiment 10, wherein the first plurality of CNT yams and the second plurality of CNT yams are substantially unidirectionally arranged (± 5°) in the precursor composite material and / or the compressed composite material.

[0139] Embodiment 12. The method of Embodiment 10, wherein the first plurality of CNT yams and the second plurality of CNT yams are substantially perpendicularly arranged (± 5°) in the precursor composite material and / or the compressed composite material.

[0140] Embodiment 13. The method of Embodiment 10, wherein the first plurality of CNT yams and the second plurality of CNT yams are arranged at an angle of about 0° to about 45°, about 0° to about 40°, about 0° to about 35°, about 0° to about 30°, about 0° to about 25°, about 0° to about 20°, about 0° to about 15°, or about 0° to about 10°, relative to each other.

[0141] Embodiment 14. The method of any one of Embodiments 1 to 13, further comprising, consisting essentially of, or consisting of contacting (i) the precursor composite material and / or the compressed composite material and (ii) a resin to form an uncured composite material.

[0142] Embodiment 15. The method of Embodiment 14, wherein the contacting of (i) the precursor composite material and / or (ii) the compressed composite material and the resin is effective to -

[0143] (a) at least partially coat the precursor composite material and / or the compressed composite material with the resin,

[0144] (b) at least partially impregnate the precursor composite material and / or the compressed composite material with the resin, or

[0145] (c) a combination thereof.

[0146] Embodiment 16. The method of Embodiment 14 or 15, wherein the contacting of the precursor composite material and the resin comprises, consists essentially of, or consists of arranging the resin between and in contact with the first plurality of CNT yarns and the second plurality of CNT yarns.

[0147] Embodiment 17. The method of any one of Embodiments 1 to 16, wherein the precursor composite material further comprises, consists essentially of, or consists of a resin arranged between and in contact with the first plurality of CNT yarns and the second plurality of CNT yarns.

[0148] Embodiment 18. The method of Embodiment 16 or 17, wherein the resin arranged between and in contact with the first plurality of CNT yarns and the second plurality of CNT yarns is in the form of a sheet.

[0149] Embodiment 19. The method of any one of Embodiments 1 to 18, further comprising, consisting essentially of, or consisting of curing the resin to form the composite material.

[0150] Embodiment 20. The method of any one of Embodiments 1 to 19, wherein a volume fraction of CNT yarns in the precursor composite material, the compressed composite material, or the composite material is at least 70 %, at least 75 %, at least 80 %, at least 85 %, at least 90 %, at least 95 %, or at least 98 %.

[0151] Embodiment 21. A method of forming a composite material, the method comprising, consisting essentially of, or consisting of -

[0152] (A) providing a first uncured composite material according to any of the preceding Embodiments,

[0153] providing a second uncured composite material according to any of the preceding Embodiments, and

[0154] arranging the second uncured composite material on and optionally in contact with the first uncured composite material; or

[0155] (B) providing a first compressed composite material of any of the precedingEmbodiments,

[0156] providing a second compressed composite material of any of the preceding Embodiments,

[0157] arranging the second compressed composite material on and optionally in contact with the first compressed composite material,

[0158] contacting a resin and the first and the second compressed composite material.

[0159] Embodiment 22. The method of Embodiment 21, further comprising, consisting essentially of, or consisting of curing the resin to form the composite material, such as before or after the arranging of the second uncured (or compressed) composite material on and optionally in contact with the first uncured (or compressed) composite material.

[0160] Embodiment 23. The method of Embodiment 21 or 22, wherein the first uncured (or compressed) composite material and the second uncured (or compressed) composite material have identical or different compositions.

[0161] Embodiment 24. The method of any one of Embodiments 21 to 23, further comprising, consisting essentially of, or consisting of -

[0162] (A) providing one or more additional uncured composite material(s) according to any one of Embodiments 14 to 18 or 20, and

[0163] arranging the one or more additional uncured composite material(s) on the first uncured composite material and / or the second uncured composite material, wherein at least one of the one or more additional uncured composite material(s) is in contact with the first uncured composite material or the second uncured composite material; or

[0164] (B) providing one or more additional compressed composite material(s) according to any of the preceding Embodiments, and

[0165] arranging the one or more additional compressed composite material(s) on the first compressed composite material and / or the second compressed composite material, wherein at least one of the one or more additional compressed composite material(s) is in contact with the first compressed composite material or the second compressed composite material.

[0166] Embodiment 25. The method of any one of Embodiments 21 to 24, wherein when the first uncured (or compressed) composite material and the second uncured (or compressed) composite material comprise substantially parallel (± 5°) CNT yarns, the CNT yarns of the first uncured (or compressed) composite material and the second uncured (or compressed) composite material (and optionally the one or more additional uncured (or compressed) composite material(s)) are substantially unidirectionally arranged (± 5°), substantially perpendicularly arranged (± 5°), or are arranged at an angle of about 0° to about 45°, about 0° to about 40°, about 0° to about 35°, about 0° to about 30°, about 0° to about 25°, about 0° to about 20°, about 0° to about 15°, or about 0° to about 10°, relative to each other.

[0167] Embodiment 26. A composite material comprising, consisting essentially of, or consisting of -

[0168] a first ply comprising a first plurality of compressed CNT yarns, a second plurality of compressed CNT yarns, at least one first CNT aerogel, and a cured resin;

[0169] wherein the at least one CNT aerogel is at least partially corrugated and arranged between the first plurality of compressed CNT yarns and the second plurality of compressed CNT yarns;

[0170] wherein the first plurality of compressed CNT yarns and the second plurality of compressed CNT yarns are free of internal voids or define internal voids of a volume less than those in identical, non-compressed CNTs; and

[0171] wherein the cured resin (i) at least partially coats the first ply, (ii) at least partially impregnates the first ply, or (iii) a combination thereof.

[0172] Embodiment 27. The composite material of Embodiment 26, wherein the first plurality of compressed CNT yarns comprises two or more substantially parallel (± 5°) CNT yams.

[0173] Embodiment 28. The composite material of Embodiment 26 or 27, wherein the second plurality of compressed CNT yarns comprises two or more substantially parallel (± 5°) CNT yarns.

[0174] Embodiment 29. The composite material of Embodiment 28, wherein the first plurality of compressed CNT yarns and the second plurality of compressed CNT yams are substantially unidirectionally arranged (± 5°) in the composite material.

[0175] Embodiment 30. The composite material of any one of Embodiments 26 to 29, further comprising, consisting essentially of, or consisting of -

[0176] a second ply comprising a third plurality of compressed CNT yarns, a fourth plurality of compressed CNT yarns, at least one second CNT aerogel, and the cured resin;

[0177] wherein the at least one second CNT aerogel is at least partially corrugated and arranged between the third plurality of compressed CNT yams and the fourth plurality of compressed CNT yarns;

[0178] wherein the third plurality of compressed CNT yarns and the fourth plurality of compressed CNT yarns are free of internal voids or define internal voids of a volume less than those in identical, non-compressed CNTs;

[0179] wherein the cured resin (i) at least partially coats the second ply, (ii) at least partially impregnates the second ply, or (iii) a combination thereof; and

[0180] wherein the second ply is arranged on and in contact with the first ply.

[0181] Embodiment 3L The composite material of Embodiment 30, wherein the third plurality of compressed CNT yarns comprises two or more substantially parallel (± 5°) CNT yams.

[0182] Embodiment 32. The composite material of Embodiment 30 or 31 , wherein the fourth plurality of compressed CNT yams comprises two or more substantially parallel (± 5°) CNT yarns.

[0183] Embodiment 33. The composite material of Embodiment 32, wherein the third plurality of compressed CNT yarns and the fourth plurality of compressed CNT yarns are substantially unidirectionally arranged (± 5°) in the composite material.

[0184] Embodiment 34. The composite material of any of the preceding Embodiments, wherein (i) the first plurality of compressed CNT yarns comprises two or more substantially parallel (± 5°) CNT yams, (ii) the second plurality of CNT yarns comprises two or more substantially parallel (± 5°) CNT yams, (iii) the first plurality of compressed CNT yams and the second plurality of compressed CNT yams are substantially unidirectionally arranged (± 5°) in the composite material, (iv) the third plurality of compressed CNT yams comprises two or more substantially parallel (± 5°) CNT yarns, (v) the fourth plurality of compressed CNT yarns comprises two or more substantially parallel (± 5°) CNT yarns, (vi) the third plurality of compressed CNT yams and the fourth plurality of compressed CNT yams are substantially unidirectionally arranged (± 5°) in the composite material, and (vii) (a) the first and the second pluralities of CNT yarns and (b) the third and the fourth pluralities of CNT yams are arranged substantially perpendicularly (± 5°) to each other.

[0185] Embodiment 35. The method or composite material of any of the preceding Embodiments, wherein the CNT yarns comprise, consist essentially of, or consist of spun CNT yams, unspun CNT yams, or a combination thereof.

[0186] Embodiment 36. The method or composite material of any of the preceding Embodiments, wherein the CNT aerogel, also referred to as a CNT “sock”, comprises, consists essentially of, or consists of an unaligned, two-dimensional network of CNTs.

[0187] Embodiment 37. The method or composite material of any of the preceding Embodiments, wherein the CNT aerogel is obtained from a floating catalyst chemical vapor deposition process.

[0188] Embodiment 38. The method or composite material of any of the preceding Embodiments, wherein the CNT sock has a thickness of about 10 pm or less, about 5 pm or less, about 2 pm or less, or about 1 pm.

Claims

Claims:

1. A method of forming a composite material, the method comprising: providing a precursor composite material, the precursor composite material comprising - a first plurality of CNT yams, a second plurality of CNT yarns, and at least one CNT aerogel arranged between the first plurality of CNT yams and the second plurality of CNT yams; and compressing the precursor composite material with a force to form a compressed composite material, wherein the force is effective to reduce a volume of internal voids defined by the first plurality of CNT yarns and the second plurality of CNT yams.

2. The method of claim 1, wherein the first plurality of CNT yams comprises two or more substantially parallel (± 5°) CNT yams, and wherein the second plurality of CNT yams comprises two or more substantially parallel (± 5°) CNT yarns.

3. The method of claim 2, wherein the first plurality of CNT yams and the second plurality of CNT yams are arranged substantially unidirectionally (± 5°).

4. The method of claim 2, wherein the first plurality of CNT yams and the second plurality of CNT yams are arranged substantially perpendicularly (± 5°) to each other.

5. The method of claim 1, wherein the precursor composite material further comprises a resin arranged between the first plurality of CNT yams and the second plurality of CNT yams.

6. The method of claim 1, wherein the force is about 50 MPa to about 300 MPa.

7. The method of claim 6, wherein the force is applied by a hydraulic press.

8. The method of claim 1, further comprising contacting the compressed composite material and a resin to form an uncured composite material.

9. The method of claim 8, wherein the contacting of the compressed composite material and the resin is effective to (i) at least partially coat the compressed composite material with the resin, (ii) at least partially impregnate the compressed composite material with the resin, or (iii) a combination thereof.

10. The method of claim 8, further comprising curing the resin to form the composite material.

11. The method of claim 10, wherein a volume fraction of CNT yams in the composite material is at least 85 %.

12. The method of claim 10, wherein a volume fraction of CNT yams in the composite material is at least 90%.

13. A method of forming a composite material, the method comprising: providing a first and a second uncured composite material of claim 8; arranging the second uncured composite material on and in contact with the first uncured composite material; and curing the resin after the arranging of the second uncured composite material on and in contact with the first uncured composite material.

14. The method of claim 13, wherein the first uncured composite material and the second uncured composite material comprise two or more substantially parallel (± 5°) CNT yams.

15. A method of forming a composite material, the method comprising: providing a first and a second compressed composite material of claim 1 ; arranging the second compressed composite material on the first compressed composite material; contacting a resin and the first and the second compressed composite material; and curing the resin.

16. A composite material comprising: a first ply comprising a first plurality of compressed CNT yarns, a second plurality of compressed CNT yarns, at least one first CNT aerogel, and a cured resin; wherein the at least one CNT aerogel is at least partially corrugated and arranged between and in contact with the first plurality of compressed CNT yams and the second plurality of compressed CNT yarns; wherein the first plurality of compressed CNT yarns and the second plurality of compressed CNT yarns are free of internal voids or define internal voids of a volume less than those in identical, non-compressed CNTs; and wherein the cured resin (i) at least partially coats the first ply, (ii) at least partially impregnates the first ply, or (iii) a combination thereof.

17. The composite material of claim 16, wherein the first plurality of compressed CNT yams comprises two or more substantially parallel (± 5°) CNT yams, and the second plurality of CNT yams comprises two or more substantially parallel (± 5°) CNT yams.

18. The composite material of claim 17, wherein the first plurality of compressed CNT yams and the second plurality of compressed CNT yams are substantially unidirectionally arranged (± 5°) in the composite material.

19. The composite material of claim 16, further comprising: a second ply comprising a third plurality of compressed CNT yarns, a fourth plurality of compressed CNT yarns, at least one second CNT aerogel, and the cured resin; wherein the at least one second CNT aerogel is at least partially cormgated and arranged between and in contact with the third plurality of compressed CNT yarns and the fourth plurality of compressed CNT yarns; wherein the third plurality of compressed CNT yarns and the fourth plurality of compressed CNT yarns are free of internal voids or define internal voids of a volume less than those in identical, non-compressed CNTs; wherein the cured resin (i) at least partially coats the second ply, (ii) at least partially impregnates the second ply, or (iii) a combination thereof; and wherein the second ply is arranged on and in contact with the first ply.

20. The composite material of claim 19, wherein the third plurality of compressed CNT yams comprises two or more substantially parallel (+ 5°) CNT yams, and the fourth plurality of compressed CNT yarns comprises two or more substantially parallel (± 5°) CNT yarns.

21. The composite material of claim 20, wherein the third plurality of compressed CNT yams and the fourth plurality of compressed CNT yams are substantially unidirectionally arranged (± 5°) in the composite material.

22. The composite material of claim 19, wherein -(i) the first plurality of compressed CNT yams comprises two or more substantially parallel (± 5°) CNT yams,(ii) the second plurality of CNT yarns comprises two or more substantially parallel (± 5°) CNT yarns,(iii) the first plurality of compressed CNT yams and the second plurality of compressed CNT yarns are substantially unidirectionally arranged (± 5°) in the composite material,(iv) the third plurality of compressed CNT yams comprises two or more substantially parallel (± 5°) CNT yams,(v) the fourth plurality of compressed CNT yarns comprises two or more substantially parallel (± 5°) CNT yams,(vi) the third plurality of compressed CNT yams and the fourth plurality of compressed CNT yarns are substantially unidirectionally arranged (± 5°) in the composite material, and(vii) (a) the first and the second pluralities of CNT yams and (b) the third and the fourth pluralities of CNT yarns are arranged substantially perpendicularly (± 5°) to each other.

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