Stretched and broken fiber material and method for manufacturing the same

Abstract

The present invention provides a method for manufacturing stretch-fractured fiber materials, a system for manufacturing stretch-fractured fiber materials, stretch-fractured carbon fiber materials, and dried stretch-fractured carbon fiber products. [Solution] A method and system for producing a stretch-broken fiber material includes supplying a fiber material, which includes a plurality of continuous filaments and a continuous carrier film, into a stretch-breaking device such that the continuous carrier film is in contact with the fiber material, and using the stretch-breaking device to break at least a portion of the plurality of continuous filaments of the fiber material while the continuous carrier film is in contact with the fiber material, thereby producing a stretch-broken fiber material that is in contact with the continuous carrier film.

Description

Technical Field

[0001] [Government Support] This invention was made with government support under Contract No. W911W6-18-C-0050 awarded by the United States Army Research Office (USARO). The government has certain rights in this invention.

[0002] [Related Applications] This application claims the benefit of priority of U.S. Provisional Application No. 63 / 070,151, filed Aug. 25, 2020, entitled "Technique, Method and Device for the Manufacture of Stretch Broken Carbon Fiber", and U.S. Provisional Application No. 63 / 123,248, filed Dec. 10, 2020, entitled "Technique, Method and Device for the Manufacture of Stretch Broken Carbon Fiber", the entire teachings of both of which are incorporated herein by reference for any purpose.

[0003] This disclosure generally relates to stretch broken fiber materials, particularly stretch broken carbon fiber materials, and methods of manufacturing such materials using one or more carrier films.

Background Art

[0004] Composite materials such as carbon fiber materials are used in a wide variety of applications. One type of composite material that is gaining promise is stretch-fractured carbon fiber (SBCF) material, which is formed by modifying the properties of conventionally manufactured carbon fiber filaments using mechanical stretching. The stretching process cuts the fibers at inherently weak points, effectively shortening the fiber length. This can strengthen the resulting carbon fiber material in various ways, including improving the manufacturability of carbon fiber parts due to the macroscopic "ductile" behavior of the SBCF material. This can enable the manufacture of more intricate parts and complex shapes using SBCF material. The stretch-fracturment process can also remove inherent defects from the carbon fiber material, thereby improving material strength and potentially helping to reduce the cost of finished carbon fiber parts and structures by enabling a less expensive manufacturing process.

[0005] One current technique for producing SBCF material involves employing a series of rollers driven at different rotational speeds to stretch and selectively cut carbon fibers. However, this technique, as currently implemented, has many limitations, including insufficient fiber shortening, various scale-up difficulties, and difficulties in handling the shortened fibers after they have been broken. In particular, unsupported carbon fiber tows are difficult to handle once stretched and broken. In addition, carbon tow breakage, fiber entanglement on rollers, debris buildup on rollers, and other scale-up difficulties have occurred routinely. Many of these problems require the stretching and breaking machine to be stopped, cleaned, and reset before SBCF production can be resumed. As a result, commercial adoption of this technique has been limited to date. [Overview of the Initiative]

[0006] A method for producing a stretch-broken fiber material according to one embodiment of the present disclosure includes supplying a fiber material, which includes a plurality of continuous filaments and a continuous carrier film, into a stretch-breaking device such that the continuous carrier film is in contact with the fiber material, and, while the continuous carrier film is in contact with the fiber material, using the stretch-breaking device to break at least a portion of the plurality of continuous filaments of the fiber material to produce a stretch-broken fiber material that is in contact with the continuous carrier film.

[0007] Another embodiment is a system for producing a stretch-broken fiber material, comprising: a stretch-breaking device configured to break the filaments of a fiber material to shorten the average filament length of the fiber material; and a feeder configured to supply a continuous carrier sheet into the stretch-breaking device, wherein the continuous carrier sheet is in contact with the fiber material while the stretch-breaking device breaks the filaments of the fiber material.

[0008] Another embodiment includes a stretch-fractured carbon fiber material that can be molded using a molding force of 1 MPa or less.

[0009] Another embodiment includes a dry stretch-fractured carbon fiber product comprising a stretch-fractured carbon fiber tow, wherein 98% or more of the fibers of the stretch-fractured carbon fiber tow are aligned within 2°.

[0010] Various embodiments of this disclosure may overcome the limitations of the aforementioned current stretch-fractured fiber manufacturing process by utilizing one or more carrier films, such as polymer carrier films, as an essential element in the stretch-fractured process. The aforementioned carrier films may be employed on one or both sides of the bundle of fiber material during the stretch-fractured process. In various embodiments, the use of carrier films may improve grip on the fibers, prevent the fibers from sticking to the stretch-fractured machine, and provide a backing that allows for improved handling of the moldable material produced in the stretch-fractured process. The use of carrier films may also provide shorter fiber lengths, which can significantly improve the moldability and strength of SBCF. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a schematic diagram showing a differential roller system for manufacturing stretched and broken fiber material according to an embodiment of the present disclosure. [Figure 2] Figure 2 is a schematic diagram showing a dual platen system for producing stretch-fractured fiber material according to an embodiment of the present disclosure. [Figure 3A] Figure 3A is a plan view of a stretched and broken fiber material on a carrier film. [Figure 3B] Figure 3B is a cross-sectional view of the stretched and broken fiber material and carrier film along the line A-A' in Figure 3A. [Figure 3C] Figure 3C is a cross-sectional view of a stretched and broken fiber material sandwiched between a first carrier film and a second carrier film. [Figure 3D] Figure 3D is a plan view showing two tows of stretched and broken fiber material on a carrier film. [Figure 4] Figure 4 plots the fiber length profile of a stretch-broken carbon fiber (SBCF) material of one embodiment, manufactured using a carrier film that contacts the carbon fiber material during the stretch-breaking process, against the fiber length profiles of three comparative examples of SBCF materials manufactured using the prior art. [Figure 5]Figure 5 is a micrograph of an SBCF material, including (A) a comparative example of an SBCF material manufactured using a conventional technique that does not include a carrier film in contact with the fiber material during the stretch-breaking process, and (B) an SBCF material of one embodiment manufactured using a carrier film in contact with the carbon fiber material during the stretch-breaking process. [Figure 6] Figure 6 is a schematic diagram of a differential roller system for manufacturing prepreg stretch-broken fiber material, which includes a feeding device configured to supply a resin-containing sheet into a stretch-breaking device and bring it into contact with the stretch-break-fiber material. [Figure 7] Figure 7 is a plot showing the moldability of an SBCF material of one embodiment, manufactured using a carrier film that contacts the carbon fiber material during the stretching and breaking process, compared to the moldability of a comparative example of an SBCF material manufactured using the conventional technique. [Figure 8A] Figure 8A is a plan view showing a carrier film containing multiple perforations. [Figure 8B] Figure 8B is a cross-sectional view of a fibrous material placed between two perforated carrier films. [Figure 9] Figure 9 schematically shows a differential roller system for producing stretch-broken fiber material, which includes a feeder configured to supply a cured sheet into a stretch-breaking device so as to be in contact with the surface of a carrier film. [Figure 10] Figure 10 is a flowchart illustrating a method for producing a stretch-broken fiber material according to various embodiments of the present disclosure. [Modes for carrying out the invention]

[0012] Various embodiments will be described in detail with reference to the accompanying drawings. Wherever possible, the same reference numerals will be used throughout the drawings to refer to the same or similar parts. References to specific examples and embodiments are for illustrative purposes only and are not intended to limit the scope of the invention or the claims.

[0013] The present invention may "comprise" (not limit) or "consist essentially of" the components of the present invention and other content or elements described herein. As used herein, "comprising" means any other element or element not listed, in addition to the listed elements or their equivalents in structure or function. The terms "having" and "including" should also be interpreted as not limiting unless the context suggests otherwise. As used herein, "consist essentially of" means that the present invention may include content added to what is listed in the specification and / or claims, provided that the additional content does not substantially alter the basic and novel characteristics of the claimed invention.

[0014] Any and all ranges enumerated herein, including those enumerating a range "between" two values, include endpoints. Terms such as “about,” “generally,” “substantially,” and “approximately” should be interpreted as modifying the term or value in a manner that is not absolute but not discernible in the prior art. Such terms will be defined by the context and the term they modify when understood by those skilled in the art. This includes, at a minimum, the degree of expected experimental error, technical error, and instrumental error for a given technique used to measure a value. Unless otherwise indicated, where used herein, “one (a and an)” includes plural; for example, “one medium” may mean at least one medium and multiple mediums, i.e., two or more mediums.

[0015] As used herein, the term "and / or" when used in the listing of two or more items means that any one of the listed characteristics can be present or any combination of two or more of the listed characteristics can be present. For example, if a composition of the present invention is described as including feature A, B, and / or C, the composition can include only feature A, only B, only C, a combination of A and B, a combination of A and C, a combination of B and C, or a combination of A, B, and C.

[0016] Various embodiments of the present disclosure relate to methods and systems for manufacturing drawn rupture fiber materials such as drawn rupture carbon fiber materials. According to various embodiments of the present disclosure, at least one continuous carrier film may be supplied into a drawn rupture device such that at least one continuous carrier film contacts the fiber material when filaments of the fiber material are ruptured using the drawn rupture device. At least one carrier film may be drawn but not ruptured during the drawn rupture process such that the drawn rupture fiber material contacts at least one continuous carrier film.

[0017] In various embodiments, providing a continuous carrier film that contacts the fiber material during the drawn rupture process can help maintain the organization and alignment of the drawn rupture fiber filaments, which can enable improved handling and transport of the drawn rupture fiber material and improved properties of the finished parts that can be manufactured using the drawn rupture fiber material. The use of at least one carrier film can also provide a partition between the fiber material and the components of the drawn rupture device, which can minimize wear and debris on the drawn rupture device and improve the reliability and efficiency of the drawn rupture fiber manufacturing process.

[0018] FIG. 1 is a schematic diagram of a differential roller system 100 for manufacturing a drawn - broken fiber material according to various embodiments of the present disclosure. A fiber material 101 composed of a plurality of continuous fiber filaments may be supplied into a drawing - breaking device 110 and may be placed under tension by a plurality of rollers 104, 106 of the drawing - breaking device 110. In the embodiment shown in FIG. 1, the drawing - breaking device 110 includes three sets of rollers 105, 107, and 109 (which may also be referred to as the first nip station 105, the second nip station 107, and the third nip station 109, respectively). The fiber material 101 may proceed through each of the first nip station 105, the second nip station 107, and the third nip station 109 along the direction of arrow 102. At each nip station 105, 107, and 109, the fiber material 101 may pass between a first roller 104 and at least one second roller 106. In the embodiment shown in FIG. 1, each nip station 105, 107, 109 includes a first roller 104 and a pair of second rollers 106 having a diameter smaller than that of the first roller 104. At least one of the rollers 104, 106 at each nip station 105, 107, and 109 may be a drive roller that is controlled to rotate at a predetermined speed. The remaining rollers 104, 107 at each nip station 105, 107, and 109 may optionally be idler rollers. In an embodiment, the first roller 104 may have an outer surface composed of a durable material such as urethane. In some embodiments, the second roller 106 may have an outer surface composed of a metal or metal alloy such as steel.

[0019] System 100 may also include at least one feeder 111, 113 configured to supply carrier films 112, 114 into the stretch-breaking device 110. In the embodiment of Figure 1, the first feeder 111 may include a first spool capable of supplying the first carrier film 112 into the first nip station 105 of the stretch-breaking device 110. The second feeder 113 may include a second spool 113 capable of supplying the second carrier film 114 into the first nip station 105 of the stretch-breaking device 110. The first carrier film 112 may be supplied through each of the nip stations 105, 107, and 109 of the stretch-breaking device 110 such that the first carrier film 112 is positioned between the first side surface 115 of the fiber material 101 and each of the second rollers 106 of the respective nip stations 105, 107, and 109. The second carrier film 114 may be supplied through each of the nip stations 105, 107, and 109 of the stretching and breaking device 110 so that the second carrier film 114 is positioned between the second side surface 116 of the fiber material 101 and each of the first rollers 104 of the respective nip stations 105, 107, and 109. Although the embodiment in Figure 1 shows the first carrier film 112 and the second carrier film 114 positioned on opposing side surfaces 115, 116 of the fiber material 101, it will be understood that in some embodiments, the carrier film (e.g., the first carrier film 112 or the second carrier film 114) may be positioned on only one side of the fiber material 101 as the fiber material 101 progresses through the first nip station 105, the second nip station 107, and the third nip station 109.

[0020] The rollers 104 and 106 of each nip station 105, 107, and 109 may be driven to rotate at different speeds, which can impart tension to the fiber material 101, the first carrier film 112, and the second carrier film 114 as they are fed through the stretch-breaking device 110. In various embodiments, the rollers 104 and 106 of the third nip station 109 may rotate at a higher speed than the rollers 104 and 106 of the second nip station 107. This can impart tension to the fiber material 101, the first carrier film 112, and the second carrier film 114 in the region 117 between nip stations 107 and 109 (which may also be called the “breaking zone”). The tensile strain in the fibrous material 101 within the fracture zone 117 may be sufficient to cause at least a portion of the filaments of the fibrous material 101 to break along the weaker parts of the filaments, thereby shortening the average length of the filaments and producing a stretch-fractured fibrous material 101'. However, the tensile strain in the first carrier film 112 and the second carrier film 114 within the fracture zone 117 may be sufficient to stretch (i.e., elongate) the films 112 and / or 114, but not to cause the carrier films 112 and / or 114 to break.

[0021] Therefore, as the stretched-fractured fiber material 101' exits the stretched-fractured device 110, the stretched-fractured fiber material 101' may come into contact with a continuous first carrier film 112 and / or a continuous second carrier film 114. In some embodiments, the stretched-fractured fiber material 101' may be sandwiched between the continuous first carrier film 112 and the continuous second carrier film 114. In various embodiments, the carrier films 112 and / or 114 may help maintain the organization and alignment of the stretched-fractured fiber filaments, which may enable improved handling and transport of the stretched-fractured fiber material 101', as well as improved properties of the finished parts that can be manufactured using the stretched-fractured fiber material 101'. The first carrier film 112 and the second carrier film 114 can also provide a partition between the fiber material 101 and the rollers 104 and 106 of the stretch-breaking device 110, which can help prevent the fibers from sticking to or wrapping around the rollers 104 and 106 and protect the stretch-breaking device 110 from debris. In addition, direct contact between the rollers 104 and 106 and the abrasive fiber material can be reduced or eliminated, so wear on the rollers 104 and 106 can be significantly reduced. This can reduce downtime, extend the service life of the stretch-breaking device 110, and improve the overall reliability and cost-effectiveness of the stretch-breaking fiber manufacturing process.

[0022] Figure 2 schematically illustrates an alternative system 200 for producing a stretch-broken fiber material 101'. The system 200 shown in Figure 2 includes a dual-platen stretch-breaking apparatus 210. As in the system 100 shown in Figure 1, the fiber material 101 can be fed into the dual-platen stretch-breaking apparatus 210. The system 200 may also include at least one feeder 111, 113 configured to feed carrier films 112, 114 into the stretch-breaking apparatus 210. In the embodiment of Figure 2, the first feeder 111 may include a first spool capable of feeding the first carrier film 112 into the dual-platen stretch-breaking apparatus 210 such that the first carrier film 112 is positioned on the surface 115 of the first side of the fiber material 101. The second feeding device 113 may include a second spool that can feed the second carrier film 114 into the dual platen stretching and breaking device 210 such that the second carrier film 112 is positioned on the surface 116 of the second side of the fiber material 101. The embodiment shown in Figure 2 shows a pair of carrier films 112 and 114 in contact with two opposing side surfaces 115 and 116 of the fiber material 101, but it will be understood that in some embodiments the fiber material 101 may be in contact with only one of the carrier films 112 or 114.

[0023] The fibrous material 101 and at least one carrier film 112 and / or 114 can pass through a pair of platen systems 201 and 203 of the dual platen stretching and breaking device 210, each of which may be operably coupled to an actuator system 205 that can selectively apply pressure to the fibrous material 101 and carrier films 112, 114 along the direction of arrow 204. A second actuator system 206 may be configured to selectively move the platen systems 201 and 203 relative to each other along the direction of arrow 207. During operation, as the fiber material 101 and at least one carrier film 112 and / or 114 are supplied through the dual platen stretch-breaking device 210 along the direction of arrow 211, the platen systems 201 and 203 may selectively grip the sides of the fiber material 101 and carrier films 112 and 114, and at the same time, the second actuator system 206 may move the platen systems 201 and 203 away from each other along the direction of arrow 207. This may stretch the fiber material 101 and at least one carrier film 112 and / or 114 within the breaking zone 117 located between the respective platen systems 201 and 203. The tensile strain in the fiber material 101 within the breaking zone 117 may be sufficient to break at least a portion of the filaments of the fiber material 101 along the weaker parts of the filaments, thereby shortening the average length of the filaments and producing a stretch-break fiber material 101'. However, the tensile strain in the first carrier film 112 and the second carrier film 114 within the fracture zone 117 may be sufficient to stretch (i.e., elongate) at least one carrier film 112 and / or 114, but not sufficient to cause the carrier films 112 and / or 114 to fracture.

[0024] Figure 3A is a plan view of the stretch-fractured fiber material 101' on the carrier film 112, and Figure 3B is a cross-sectional view of the stretch-fractured fiber material 101' and the carrier film 112 along the line A-A' in Figure 3A. The stretch-fractured fiber material 101' may be manufactured using a suitable process, such as a differential roller-based stretch-fractured process as described above with reference to Figure 1, or a dual platen-based stretch-fractured process as described above with reference to Figure 2. Other suitable methods for manufacturing the stretch-fractured fiber material 101', including, for example, the use of a breaking bar for cutting the fiber filaments, are also within the scope of the intended disclosure. The stretch-fractured fiber material 101' may be supported on the carrier film 112, which may help maintain the alignment of the stretch-fractured filaments along the first horizontal direction (hd1) and may facilitate the handling of the stretch-fractured fiber material 101'. In some embodiments, the stretched and broken fiber material 101' may be sandwiched between the first carrier film 112 and the second carrier film 114, as shown in the cross-sectional view of Figure 3C.

[0025] In various embodiments, the stretch-broken fiber material 101' may be placed on the carrier film 112 or between two carrier films 112 and 114 during the stretch-breaking process used to manufacture the stretch-broken fiber material 101'. The stretch-breaking process may shorten the average length of the filaments by cutting the filaments of the fiber material at one or more positions along the first horizontal direction (hd1). As described above with reference to Figures 1 and 2, the stretch-breaking process may be such that the carrier films 112 and 114 are stretched but not broken so that they are continuously stretched along the first horizontal direction (hd1) after the stretch-breaking process.

[0026] In some embodiments, multiple bundles of fibers (which may also be called “tows”) can be processed simultaneously by a stretch-breaking device such as a differential roller stretch-breaking device 110 as shown in Figure 1. Multiple tows of the fiber material 101 may proceed side by side through the stretch-breaking device 110, with each tow of the fiber material 101 in contact with at least one carrier film 112, 114, as described above. In some embodiments, each tow may be in contact with a different carrier film, or each tow may be sandwiched between different pairs of carrier films. Alternatively, multiple tows may be in contact with the same carrier film 112 and / or 114. Figure 3D is a plan view showing two tows of stretch-breaking fiber material 101A' and 101B' on a carrier film 112. When fibrous material is supplied through the stretch-breaking device 110 along a first horizontal direction (hd1) to produce stretch-breaked fibrous materials 101A' and 101B', each tow of the stretch-breaked fibrous materials 101A and 101B may be in contact with the same carrier film 112. The individual tows of the stretch-breaked fibrous materials 101A and 101B may be separated laterally along a second horizontal direction (hd2). In some embodiments, an additional carrier film (not shown in Figure 3D) may be in contact with each tow of the fibrous materials 101A and 101B on the upper surface of the fibrous materials 101A and 101B.

[0027] The stretch-fracture fibrous material 101' in various embodiments of this disclosure may be a carbon fiber material, but other suitable fiber materials are also within the scope of the intended disclosure. For example, the stretch-fracture fibrous material 101' may include fiberglass, organic fiber materials such as KEVLAR® fiber materials, ceramic fibers, glass fibers, basalt fibers, graphite fibers, and other fiber materials characterized by relatively high strength and stiffness. In one embodiment, the stretch-fracture fibrous material 101' may consist of a fiber material having a Young's modulus of 5 Mpsi to 120 Mpsi.

[0028] The carrier films 112, 114 in various embodiments of this disclosure may be composed of polymer materials such as linear low-density polyethylene (LLDPE) material, but other suitable materials for the carrier films 112, 114 are also within the scope of the intended disclosure. For example, the carrier films 112, 114 may be composed of one or more of polymer materials, rubber materials, thermoplastic materials (e.g., polyimide, polypropylene, polyetheretherketone (PEEK), polyamide, etc.), fabric materials, woven materials, and / or paper-based materials. In some embodiments, the surface of at least one carrier film 112, 114 in contact with the fibrous material may include an adhesive such as an epoxy resin, which can facilitate contact between the carrier films 112, 114 and the fibrous material and help maintain the alignment of the fibrous material after the stretch-breaking process.

[0029] In various embodiments, the carrier films 112, 114 may be composed of materials that have a higher degree of stretchability before rupture compared to the fibrous material 101. For example, a carbon fiber filament under tensile stress typically elongates (i.e., stretches) about 2% of its length before rupture. In various embodiments, the carrier films 112 and / or 114 in contact with the fibrous material 101 may elongate (i.e., stretch) under tensile stress to at least 6% of its length, including at least 10% of its length, for example between 15% and 20% of its length, before rupture.

[0030] In some embodiments, the carrier films 112, 114 may be removed from the stretched-fractured fiber material 101' prior to forming the fractured fiber material 101' into manufactured parts. In some embodiments, the carrier films 112, 114 removed from the stretched-fractured fiber material 101' may be composed of recyclable material. In some embodiments, the entirety of the carrier films 112, 114 may optionally be reused in a subsequent stretch-fractured process to produce additional stretched-fractured fiber material 101'.

[0031] In some embodiments, at least one of the first carrier film 112 and / or the second carrier film 114 may remain in contact with the stretch-fractured fiber material 101' during the process in which the stretch-fractured fiber material 101' in contact with the carrier films 112, 114 is formed into a manufactured part. For example, the carrier films 112 and / or 114 may remain in contact with the stretch-fractured fiber material 101' if one or more properties of the carrier films 112, 114 may be beneficial to the final product part manufactured using the stretch-fractured fiber material 101'. In one non-limiting example, the carrier films 112, 114 containing a thermoplastic material or matrix may allow the thermoplastic material or matrix to permeate or impregnate the stretch-fractured fiber material 101'. In some embodiments, the permeated or impregnated thermoplastic material may provide faster curing and / or cycle time and other improved properties to the finished manufactured part. In some embodiments, the carrier films 112, 114 may include a material such as epoxy resin, which allows the stretched-fracture fiber material 101' in contact with the carrier films 112, 114 to sink into the carrier films 112, 114 when the carrier films 112, 114 are heated, in order to produce a matrix containing a carrier film material into which stretched-fracture fibers are impregnated.

[0032] The stretch-fractured fibrous material 101', such as stretch-fractured carbon fiber (SBCF), may be composed of fibers of various lengths. Differences in fiber length of the stretch-fractured fibrous material 101' can provide materials with different properties and characteristics. The length of individual fibers within a bundle or tow of the stretch-fractured fibrous material may be measured, and the resulting fiber length distribution may indicate the material's properties. Figure 4 plots the fiber length profile 401 of a stretch-fractured carbon fiber (SBCF) material (MSU SB2) of one embodiment, manufactured using a carrier film that contacts the carbon fiber material during the stretch-fractured process, as described above, with the fiber length profiles 402, 403, and 404 of three comparative examples of stretch-fractured carbon fiber (SBCF) materials (i.e., IM7 SB2, Hexcel Legacy, and Albany) manufactured using a conventional technique that does not include a carrier film that contacts the fiber material during the stretch-fractured process. As can be seen from Figure 4, the fiber length profile 401 of the embodiment's SBCF material shows a significant reduction in average fiber length (i.e., 3.4 cm) compared to the average fiber lengths of Comparative Examples 402, 403, and 404 (i.e., 5.3 cm, 6.2 cm, and 4.8 cm, respectively). The embodiment's SBCF material 401 made using a carrier film also exhibits a very tight fiber length distribution and a reduction in long fibers compared to Comparative Examples 402, 403, and 404. The reduction or elimination of long fibers in SBCF materials, such as fibers with a length exceeding 6 cm, may help provide a macroscopically moldable carbon fiber material.

[0033] In various embodiments, SBCF materials manufactured using a carrier film that contacts the carbon fiber material during the stretch-breaking process may have an average fiber length of less than 4 cm. In some embodiments, SBCF materials manufactured using a carrier film that contacts the carbon fiber material during the stretch-breaking process may have a median fiber length of less than 5 cm, such as less than 4 cm. In some embodiments, the standard deviation of the fiber length of the SBCF material of the embodiment may be less than 0.95. In some embodiments, less than 0.01% of the fibers of the SBCF material of the embodiment may have a fiber length greater than 6 cm. In some embodiments, more than 50% of the fibers of the SBCF material of the embodiment may have a fiber length of 1.0 cm to 3.5 cm. In some embodiments, more than 2% of the fibers of the SBCF material of the embodiment may have a fiber length of less than 2 cm. In some embodiments, the fiber diameter of the SBCF material of the embodiment may be 5 μm to 15 μm.

[0034] Figure 5 shows micrographs of SBCF materials, including (A) a comparative example of an SBCF material manufactured using a conventional technique that does not include a carrier film in contact with the fiber material during the stretch-breaking process, and (B) an SBCF material of one embodiment manufactured using a carrier film in contact with the carbon fiber material during the stretch-breaking process as described above. The micrograph on the right (B) shows a significant improvement in fiber alignment compared to the comparative example in micrograph (A). Various embodiments include dry fiber SBCF materials in which 98% or more of the fibers are aligned within 2° in each bundle or tow of the SBCF material. As used herein, “dry fiber” SBCF material means an SBCF material that does not contain or essentially contains resin material. As used herein, “bundle” or “tow” of SBCF material means at least 10 3This is an untwisted group of SBCF materials, each containing individual carbon fiber filaments. In some embodiments, a tow of SBCF material may contain an even number of carbon fiber filaments, such as 3,000 filaments ("3K tow"), 6,000 filaments ("6K tow"), and 12,000 filaments ("12K tow").

[0035] Additional embodiments of the present disclosure include prepreg stretch-fractured fiber materials. Prepreg stretch-fractured fiber is a general term for stretch-fractured fiber materials, such as SBCF materials, that have been pre-impregnated with a resin system. The resin system may include a suitable resin such as epoxy, and may also include a suitable curing agent. As a result, the prepreg stretch-fractured fiber material may be ready to be placed in a mold for forming a part without requiring the addition of a resin material in another step.

[0036] In some embodiments, the surfaces of the carrier films 112, 114 that come into contact with the fiber material 101 during the stretch-breaking process may include a resin material, such as an epoxy resin, that can impregnate the stretch-breaking fibers to provide a prepreg stretch-breaking fiber material. Alternatively, or in addition to the above, a resin-containing film or sheet, such as a paper sheet with a resin coating, may come into contact with the fibers after the stretch-breaking process, so that the resin material can impregnate the stretch-breaking fibers to provide a prepreg stretch-breaking fiber material.

[0037] Figure 6 shows one embodiment of a system 600 that may be used to manufacture prepreg stretch-broken fiber material according to various embodiments of the present disclosure. The system 600 in Figure 6 includes a differential roller stretch-broken device 610 and is similar to the aforementioned system 100 in Figure 1. Therefore, repeated descriptions of similar components are omitted. The system 600 in Figure 6 differs from the system 100 in Figure 1 in that a carrier film 114 is fed through nip stations 105, 107 and 109 during the stretch-broken process and contacts one side 116 of the fiber material 101, but the carrier film does not contact the opposite side 115 of the fiber material 101 during the stretch-broken process. The system 600 also includes a feeder 603 configured to feed a resin-containing sheet 601 into the stretch-broken device 610. In the embodiment of Figure 6, the feeder 603 may include a spool that can feed the resin-containing sheet 601 into a third nip station 109 of the stretch-broken device 610. In some embodiments, the resin-containing sheet 601 may enter a third nip station 109 downstream of a break zone 117 located between nip stations 107 and 109, and thus the resin-containing sheet 601 may come into contact with the side surface 115 of the fibrous material after stretch-breaking. The resin material of the resin-containing sheet 601 may be impregnated into the stretch-breaking fibers to provide a prepreg stretch-breaking fibrous material 101'. In some embodiments, the resin-containing sheet 601 may be a paper sheet coated with an epoxy resin material.

[0038] In various embodiments, the surface of the resin-containing sheet 601 in contact with the fibrous material 101 may have adhesive or tacky properties. This can assist the resin-containing sheet 601's ability to grip the stretch-fractured fibrous material, improving the robustness and reliability of the stretch-fractured system 600. The tacky surface of the resin-containing sheet also helps to immobilize the fibers almost immediately after stretch-fracturing, which can help the stretch-fractured fibers maintain their alignment. In addition, a consistent area weight of the prepreg fibrous material can be ensured because the fibers remain continuous and therefore easy to handle while a consistent amount of prepreg resin material can be applied to the fibers after stretch-fracturing, and tow elongation and fiber control can be performed. This means that industry-standard fiber handling techniques can be employed, and a consistent fibrous fabric can be used, as in any conventional prepreg line. Furthermore, the cost of manufacturing the prepreg stretch-broken fiber material 101' can be reduced compared to other SBCF prepreg materials, and the required workflow and machinery can be significantly simplified.

[0039] Stretched fractured fiber materials 101' manufactured using carrier films according to various embodiments of this disclosure, such as stretched fractured carbon fiber (SBCF) materials, may have improved moldability compared to conventional stretched fractured fiber materials. Figure 7 is a plot showing the moldability of an SBCF material of one embodiment (MSU SBCF) manufactured using a carrier film that contacts the carbon fiber material during the stretching fracture process, as described above, compared to the moldability of a comparative example SBCF material (Hexcel SBCF) manufactured using a conventional technique that does not include a carrier film that contacts the fiber material during the stretching fracture process. Samples of various lengths were tested by applying tension to the fibers, and the resulting moldability was measured. The tests included tows of approximately 12,000 carbon fibers with diameters up to approximately 5.5 μm. The gauge length represents the distance between pinch points where the fiber tow was supported during the test. The moldability of each SBCF tow was tested by applying a load perpendicular to the fiber direction between pinch points at various gauge lengths. The average maximum load ("avg.max load") represents the average peak load at the fiber tow before the fibers begin to elongate (i.e., strain > 0.2% in the fiber). Thus, a lower average maximum load at smaller gauge lengths indicates that the SBCF material is more moldable. As shown in Figure 7, the improved fiber length profile of the embodiment's SBCF material (SBCF MSU) provides a significantly reduced molding force compared to the comparative example's SBCF material (SBCF Hexcel). In particular, the embodiment's SBCF material can be molded into complex shapes much more easily than the comparative example's SBCF material. This significant improvement in moldability can greatly facilitate the manufacture of carbon fiber parts compared to either conventional continuous fiber carbon or conventional SBCF material. In various embodiments, SBCF materials manufactured using a carrier film that contacts the carbon fiber material during the stretch-breaking process may be moldable with a molding force of 1 MPa or less.

[0040] In some embodiments, the carrier films 112, 114 that come into contact with the fibrous material during the stretch-breaking process may include perforations penetrating the carrier films 112, 114. Figure 8A is a plan view showing a carrier film 112 including a plurality of perforations 801. Figure 8B is a cross-sectional view along line B-B' in Figure 8A. As shown in Figure 8B, the carrier film 112 including the perforations 801 comes into contact with the upper surface of the stretch-breaking fibrous material 101'. In the embodiment of Figure 8B, a second carrier film 114 including the perforations 801 comes into contact with the lower surface of the stretch-breaking fibrous material 101'.

[0041] In various embodiments, the carrier films 112 and / or 114 may be perforated prior to or as part of the stretch-breaking process to reinforce the fiber material 101 and / or to facilitate the process of using the fiber material 101, so as to allow the material to reach the fiber material 101. In particular, the carrier films 112 and / or 114 may be perforated prior to or during the stretch-breaking process so as not to obstruct the introduction of the desired reinforcing material into the fibers. Arrow 603 in Figure 8B schematically shows the reinforcing material introduced into the fiber material 101 through perforation 601 in the carrier film 112.

[0042] Sizing is a type of material that may be used to enhance the processing of a stretch-broken fiber material 101. Sizing is a thin, homogeneous coating applied to the surface of fibers during the manufacturing process to protect the fiber filaments during handling and processing, and during subsequent compounding and synthesis processes of the stretch-broken fiber material. Sizing materials used in the stretch-broken fiber material process may include water-soluble polymers called fabric sizing agents, such as chemical substances like modified starch, polyvinyl alcohol (PVA), carboxymethylcellulose (CMC), and acrylates. Other suitable sizing materials are also within the scope of the intended disclosure. Perforations 601 penetrating the carrier film 112 and / or 114 may be configured to allow the sizing solution to reach the fiber material 101.

[0043] The perforations 601 in the carrier films 112 and / or 114 are not limited to enabling the transfer of sizing material to the carrier films, but may also be used to allow any desired material to pass through the carrier films 112 and / or 114 to reach the fiber material 101. Such material includes, but is not limited to, solutions, gases, lubricants, vapors, hot air, or other materials, which may reach the fiber material 101 and / or subsequent processing steps as desired. For example, prior to the stretch-breaking step, the sizing agent may be pre-coated to the fibers, and a solvent or other softener may be transferred through the perforations 601 in the carrier films 112 and / or 114 to reconstitute and activate the pre-coated sizing agent. Suitable solvents / softeners include, but is not limited to, alcohols, other organic solvents, water, or vapors.

[0044] The perforations 601 may have any desired size (e.g., microholes or macroholes) that allows the desired reinforcing material to pass through the carrier film 112 and / or 114 to reach the fibrous material 101. For example, the carrier film 112 and / or 114 may be composed of a microporous material such as a GORETEX® film that allows a specific reinforcing material (e.g., vapor) to pass through the carrier film 112 and / or 114 while blocking other materials. The perforations 601 in the carrier film 112 and / or 114 may be made by any means preferred for optimal introduction of the reinforcing material. Such perforation means may include punching holes, laser burning, drilling, molding, or other perforation methods.

[0045] In one embodiment, an automatic roller (e.g., a "porcupine roller") with spikes on its outer surface may be used to perforate the carrier films 112 and / or 114 when they pass through the stretch-breaking process, or prior to the stretch-breaking process, such as during the manufacture of the carrier films 112 and / or 114. The pattern and / or size of the perforations 601 formed in the carrier film material may be modified as necessary to optimize the stretch-breaking fiber processing.

[0046] Alternatively, the carrier films 112 and / or 114 may be made from a polymer or other material manufactured with a desired and optimal porous structure to allow sizing or other reinforcing materials to reach or penetrate the fibrous material 101. For example, sintered polyethylene technology of the type used in making filters can be used to provide the porous carrier films 112 and / or 114.

[0047] The carrier films 112 and / or 114 containing the perforations 601 may be used to produce (1) a dry material form suitable for weaving or sewing into a cloth, (2) a dry material in the form of a woven fabric or a unidirectional tape, or (3) a stretch-break fiber material 101 suitable for the production of a prepreg stretch-break fiber material 101.

[0048] Figure 9 shows another embodiment of system 900 that may be used to produce stretch-breakable fiber materials according to various embodiments of the present disclosure. System 900 in Figure 9 includes a differential roller stretch-breaking device 910 and is similar to system 100 described above with reference to Figure 1. Therefore, a repeated discussion of similar components is omitted. System 900 in Figure 6 differs from system 100 in Figure 1 in that a cured sheet 901 is supplied to the stretch-breaking device 900 downstream of the breaking zone 117. System 900 may also include a feeder 903 configured to supply the cured sheet 901 into the stretch-breaking device 910. In the embodiment of Figure 9, the feeder 903 may include a spool that can supply the cured sheet 901 into a third nip station 109 of the stretch-breaking device 910. The cured sheet 901 may have higher rigidity than the first carrier film 112 and the second carrier film 114. In this embodiment, the cured sheet 901 may be in contact with the first carrier film 112 such that the first carrier film 112 is positioned between the cured sheet 901 and the stretched and broken fiber material 101'.

[0049] In various embodiments in which carrier films 112 and 114 are positioned on two sides 115 and 116 of the fibrous material 101 during the stretch-breaking process, the release of tension in the carrier films 112 and 114 as they exit the stretch-breaking device 910 may cause the carrier films 112 and 114 to bounce. This bounce of the carrier films 112 and 114 may cause the formation of a wavy pattern in the stretch-breaking fibrous material 101' between the respective carrier films 112 and 114. This wavy pattern in the stretch-breaking fibrous material 101' may reduce the alignment and organization of the stretch-breaking fibrous material 101'. Therefore, by providing a cured sheet 901 that contacts one of the carrier films 112 prior to the carrier films 112 and 114 exiting the stretch-breaking device 901, the bounce of the carrier films 112 and 114 and the resulting formation of a wavy pattern in the stretch-breaking fibrous material 101' can be reduced or eliminated. In some embodiments, the hardened sheet 901 may be composed of a metallic material such as spring steel. Other suitable materials for the hardened sheet 901 are also within the scope of the intended disclosure. In some embodiments, the hardened sheet 901 may be a reusable component. The carrier films 112 and 114 and the stretch-breaking fiber material 101' may be removed from the hardened sheet 901, and the hardened sheet 901 may be rebounded in the stretch-breaking system 900 and reused.

[0050] Figure 10 is a flow chart showing a method 1000 for producing a stretch-broken fiber material 101' according to various embodiments of the present disclosure. Referring to Figure 10, in step 1001 of method 1000, a fiber material 101 comprising a plurality of filaments and carrier films 112, 114 may be fed into a stretch-breaking device (110, 210, 610, 910) such that the carrier films 112, 114 are in contact with the fiber material 101. In step 1003 of method 100, while the carrier films 112, 114 are in contact with the fiber material 101, at least a portion of the plurality of filaments of the fiber material 101 are broken using the stretch-breaking device (110, 210, 610, 910) to produce a stretch-broken fiber material 101' that is in contact with the continuous carrier films 112, 114.

[0051] While the above refers to specific embodiments, it will be understood that the disclosure is not limited in that way. Those skilled in the art will recognize that various modifications can be made to the disclosed embodiments, and that such modifications are intended to be within the scope of the disclosure. Interoperability is presumed between all embodiments that are not substitutes for one another. The words “comprise” or “include” assume all embodiments in which the words “consist essentially of” or “consists of” are substituted for the words “comprise” or “include,” unless expressly stated otherwise. Where embodiments using a particular structure and / or configuration are illustrated in the disclosure, it will be understood that the disclosure can be implemented with any other functionally equivalent and compatible structure and / or configuration, unless such substitution is expressly prohibited or otherwise known to those skilled in the art. All publications, patents, and patent applications referenced herein are incorporated herein by reference to the same extent as any individual publication, patent, or patent application is specifically and individually indicated as being incorporated herein by reference in whole.

Claims

1. A method for producing stretched and broken fiber materials, A fibrous material comprising multiple continuous filaments and a continuous carrier film is supplied into a stretching and breaking device such that the continuous carrier film is in contact with the fibrous material. While the continuous carrier film is in contact with the fiber material, the stretch-breaking device is used to break at least a portion of the plurality of continuous filaments of the fiber material to produce a stretch-breaked fiber material that is in contact with the continuous carrier film. The method, including the method described above.

2. The continuous carrier film includes a first continuous carrier film that contacts the fiber material on a first side surface of the fiber material, and the method is The second continuous carrier film is supplied into the stretching and breaking device such that the second continuous carrier film contacts the fiber material on a second side of the fiber material opposite to the first side of the fiber material. The method according to claim 1, further comprising:

3. The method according to claim 1, wherein, under tensile stress, the continuous carrier film is capable of elongating by at least 6% of the length of the continuous carrier film along the direction of the tensile stress before the continuous carrier film breaks.

4. The method according to claim 1, wherein the fiber material includes at least one of carbon fiber material, fiberglass material, organic fiber material, ceramic fiber material, glass fiber material, basalt fiber material, and graphite fiber material.

5. The method according to claim 4, wherein the continuous carrier film comprises at least one of a polymer material, a rubber material, a thermoplastic material, a cloth material, a woven material, and a paper-based material.

6. The method according to claim 5, wherein the continuous carrier film includes a resin material on the surface of the continuous carrier film that is in contact with the fiber material in order to produce a prepreg stretched and broken fiber material that is in contact with the continuous carrier film.

7. The method according to claim 2, wherein the second continuous carrier film is supplied into the stretch-breaking device and in contact with the second side surface of the fiber material prior to breaking at least a portion of the plurality of continuous filaments of the fiber material using the stretch-breaking device.

8. The method according to claim 2, wherein the second continuous carrier film is supplied into the stretch-breaking device and in contact with the second side surface of the fiber material after at least a portion of the plurality of continuous filaments of the fiber material have been broken using the stretch-breaking device.

9. The method according to claim 7, wherein the second continuous carrier film includes a resin-containing sheet containing a resin material that contacts the second side surface of the fiber material to produce a prepreg stretch-broken fiber material.

10. The method according to claim 1, wherein the continuous carrier film includes a plurality of perforations penetrating the continuous carrier film, the perforations being configured to allow the reinforcing agent to pass through the perforations into the fibrous material.

11. The method according to claim 2, further comprising supplying a cured film into the stretch-breaking device after at least a portion of the plurality of continuous filaments of the fiber material has been broken using the stretch-breaking device, wherein the cured film has higher rigidity than the first continuous carrier film and the second carrier film, and either the first continuous carrier film or the second carrier film is positioned between the fiber material and the cured film.

12. A system for manufacturing stretched and broken fiber materials, A stretching and breaking device configured to break the filaments of a fiber material and shorten the average filament length of the fiber material, A supply device configured to supply a continuous carrier sheet into the stretching and breaking device, wherein the continuous carrier sheet is in contact with the fiber material while the stretching and breaking device breaks the filaments of the fiber material. The system including the above.

13. The stretching and breaking device includes a differential roller stretching and breaking device, according to claim 12.

14. The system according to claim 12, wherein the stretching and breaking device includes a dual platen stretching and breaking device.

15. The system according to claim 12, wherein the supply device includes a first supply device configured to supply a first continuous carrier film into the stretch-breaking device such that the first continuous carrier film is in contact with a first side surface of the fibrous material, and the system further includes a second supply device configured to supply a second continuous carrier film into the stretch-breaking device such that the second continuous carrier film is in contact with a second side surface of the fibrous material opposite to the first side surface.

16. The system according to claim 12, wherein the second supply device is configured to supply the second continuous carrier film into the stretch-breaking device such that the second continuous carrier film contacts the second side surface of the fiber material prior to the stretch-breaking device breaking the filaments of the fiber material.

17. The system according to claim 16, comprising a resin-containing sheet containing a resin material, the second continuous carrier film being supplied into the stretch-breaking device and contacting the second side surface of the fiber material after the filaments of the fiber material have been broken to provide a prepreg stretch-breaking fiber material.

18. A stretch-fracture carbon fiber material that can be molded using a molding force of 1 MPa or less.

19. The stretched and broken carbon fiber material according to claim 1, wherein the stretched and broken carbon fiber material has an average fiber length of less than 4 cm.

20. A dry stretched-fractured carbon fiber product comprising a stretched-fractured carbon fiber tow, wherein 98% or more of the fibers of the stretched-fractured carbon fiber tow are aligned within 2°.

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