Composite material and method for manufacturing the same

Abstract

This enables the reliable and / or efficient utilization or reuse of carbon fibers, even those of relatively short lengths. [Solution] The present invention provides a method for manufacturing a composite material, comprising a carding step of carding a mixture of carbon fibers and thermoplastic resin fibers, and a heating and pressing step of heating and pressing the carded mixture without performing the following (1) to (4) processes, wherein the heating and pressing step forms a sheet-like or strip-like composite material. (1) Contangle treatment by needle punching (2) Entanglement treatment by water flow treatment (3) Cross-layer processing (4) Folding process

Description

[Technical Field] 【0001】 The present invention relates to composite materials, particularly composite materials containing carbon fibers, and a method for producing the same. [Background technology] 【0002】 Carbon fiber reinforced plastics (CFRP) possess excellent physical properties, including mechanical properties such as lightness, high strength, and high rigidity, electrical properties including electrical conductivity and electromagnetic shielding, and thermal properties including thermal conductivity and heat resistance. Therefore, they are utilized in various fields such as medicine, aerospace, industrial equipment, construction, civil engineering, and automobiles. Furthermore, the applications of carbon fiber are likely to expand even further in the future. 【0003】 There are many types of carbon fibers, including polyacrylonitrile-based carbon fibers, rayon-based carbon fibers, pitch-based carbon fibers, cellulose-based carbon fibers, and polyimide-based carbon fibers. Furthermore, composite materials composed of carbon fibers and resin compositions have conventionally been manufactured using many types of manufacturing methods, such as injection molding, continuous pressing, or pultrusion (Patent Document 1). 【0004】 Furthermore, the fiber length of the carbon fiber is adjusted as appropriate depending on the application. After the carbon fiber, which is manufactured as a continuous fiber immediately after production, is cut to the desired length, carbon fibers with relatively long or short fiber lengths can be produced. On the other hand, a method for producing carbon fibers having a fiber length distribution of 100 μm to 3 mm, referred to as short fiber, has been disclosed (Patent Document 2). This method involves crushing carbon fibers bonded with resin, and then thermally decomposing the crushed material under conditions where the decomposition gas of the crushed material is present. [Prior art documents] [Patent Documents] 【0005】 [Patent Document 1] Japanese Patent Publication No. 2006-249395 [Patent Document 2] Japanese Patent Application Publication No. 11-50338 [Overview of the Initiative] [Problems that the invention aims to solve] 【0006】 However, while the applications of carbon fiber composite materials are expanding, the high energy consumption during their manufacture, the difficulty in reusing the resulting waste materials, and the significant environmental impact of their disposal are posing technical and social challenges. 【0007】 For example, scraps (including waste materials; the same applies hereinafter) generated during the manufacture of carbon fiber and waste materials generated during disposal contain a large amount of irregularly shaped and short-length carbon fibers. In the case of waste materials from carbon fiber reinforced plastics (CFRP), which are widely used, these waste materials contain matrix resins such as epoxy resin, and are therefore disposed of after being cut or broken. However, the amount of irregularly shaped and short-length carbon fibers that are reused as a result of these processes remains small. Therefore, compared to the large demand for virgin carbon fiber, the development of technologies and social implementation for the reliable and / or efficient utilization or reuse of the irregularly shaped and short-length carbon fibers contained in these scraps and waste materials is still in its early stages. [Means for solving the problem] 【0008】 The present invention solves at least one of the above-mentioned problems and can greatly contribute to the realization of a technology that enables the reliable and / or efficient utilization or reuse of carbon fibers, even those with relatively short fibers. 【0009】 The inventors diligently conducted research to enhance the usability or value of carbon fibers, not only when the starting material is waste material, but also when it is virgin material or its scraps, and even when the starting material is carbon fiber with a relatively short fiber length. Through trial and error, the inventors focused on the manufacturing process up to the molding of so-called intermediate materials such as prepregs or sheets containing carbon fibers. Furthermore, even when using carbon fibers with a short fiber length, the inventors diligently analyzed and considered ways to introduce new technologies or make improvements to the manufacturing process in order to improve the performance of applied products to which these carbon fibers are used. 【0010】 As a result, the inventors discovered that by deliberately omitting several key processes used in the manufacturing process of conventional nonwoven fabrics or spun yarns, processing the material while it is still small in weight and thin, and further adding ingenuity to the pressing process for forming the intermediate material, it is possible to solve at least one of the above-mentioned problems. The present invention was created based on the above-mentioned perspectives and ideas. 【0011】 One composite material of the present invention comprises carbon fibers and thermoplastic resin fibers, and is in the form of a sheet or strip. Furthermore, the basis weight of the composite material is 5 g / m². 2 More than 150g / m 2 The following conditions apply, and the thickness is between 0.1 mm and 3 mm. 【0012】 This composite material, being a sheet or strip containing carbon fibers and thermoplastic resin fibers, offers superior moldability compared to conventionally used carbon fiber-containing composite materials (for example, composite materials consisting of thermosetting resins such as epoxy resin and carbon fibers). Furthermore, it reduces processing time and man-hours, thereby lowering the cost of manufacturing the composite material. Additionally, the small basis weight and thin thickness of this composite material make it the smallest unit for use as an intermediate material, significantly increasing the design flexibility of application products using this composite material as an intermediate. Moreover, because the composite material is sheet or strip-shaped and possesses the basis weight and thickness characteristics within the aforementioned numerical range, it is advantageous in that, for example, by stacking multiple sheets of the composite material, it allows for flexible design of the physical strength or rigidity in the planar direction of the sheet-shaped composite material (in other words, directions other than the thickness direction) or in the longitudinal direction and the direction perpendicular to the longitudinal direction along the plane of the strip-shaped composite material. 【0013】 Furthermore, one method for manufacturing a composite material according to the present invention includes a carding step of carding a mixture of carbon fibers and thermoplastic resin fibers, and a heating and pressing step of heating and pressing the carded mixture without performing the following (1) to (4) processes, wherein the heating and pressing step forms a sheet-like or strip-like composite material. (1) Contangle treatment by needle punching (2) Entanglement treatment by water flow treatment (3) Cross-layer processing or stacking processing by cross-layering (may also be called "wrapping processing") (4) Folding process 【0014】 According to this composite material manufacturing method, the above-described heating and pressing step is performed on a mixture of carbon fibers and thermoplastic resin fibers that have been processed by the carding step, without performing any of the above-described steps (1) to (4). This makes it possible to reliably reduce the mass of carbon fibers oriented in the thickness direction of the sheet-like or strip-like composite material formed by pressing, or the proportion of carbon fibers oriented in the thickness direction to the total carbon fibers. As a result, the tensile strength or bending strength in the planar direction of the composite material (and moreover, the molded product using the composite material) can be stabilized. Therefore, according to this composite material manufacturing method, a composite material containing carbon fibers that can withstand practical use can be manufactured very simply without performing the above-described steps (1) to (4). Furthermore, according to this composite material manufacturing method, since the number of steps required to manufacture the composite material is reduced as described above, the manufacturing cost of the composite material can be significantly reduced. 【0015】 Furthermore, in each of the above-mentioned inventions, the fact that the carbon fibers are made from virgin material scraps, waste materials, or recycled materials is a preferred embodiment, as it can serve as one means of solving social issues related to environmental impact. [Effects of the Invention] 【0016】 One composite material of the present invention is a sheet-like or strip-like composite material containing carbon fibers and thermoplastic resin fibers. Because the basis weight and thickness of the composite material have the above-described characteristics, it exhibits superior moldability compared to conventionally used carbon fiber-containing composite materials, and can reduce the processing time and man-hours required for the composite material, thereby reducing the cost of manufacturing the composite material. Furthermore, because the composite material is in the form of a sheet or strip and possesses the basis weight and thickness characteristics within the above-described numerical range, it is advantageous in that, for example, by stacking multiple composite materials, it is possible to freely design the physical strength or rigidity in the planar direction of the sheet-like composite material (in other words, a direction other than the thickness direction) or in the longitudinal direction and the direction perpendicular to the longitudinal direction along the plane of the strip-like composite material (for example, the freedom to stack multiple composite materials). 【0017】 Moreover, according to the manufacturing method of one composite material of the present invention, the mass of carbon fibers oriented in the thickness direction of the sheet-shaped or strip-shaped composite material, or the ratio of carbon fibers oriented in the thickness direction to the entire carbon fibers, can be accurately reduced. As a result, the tensile strength or flexural strength in the plane direction of the composite material (more precisely, the molded product using the composite material) can be stabilized, and thus a composite material containing carbon fibers that can withstand practical use can be manufactured. 【Brief Description of Drawings】 【0018】 [Figure 1] It is a process flow diagram showing a part of the manufacturing process of the composite material of the first embodiment. [Figure 2] It is a plan view of the composite material 100a of the first embodiment. [Figure 3] It is a plan view of the composite material 100b of the first embodiment. [Figure 4] It is a schematic configuration diagram of a part of a carding machine that performs the carding process of the first embodiment. [Figure 5] It is a photograph showing an example of a molded product formed using the composite materials 100a and 100b of the first embodiment as starting materials. [Figure 6] It is (a) the measurement result by an X-ray CT apparatus of an example of the composite materials 100a and 100b of the first embodiment, and (b) the measurement result of a comparative example. 【Modes for Carrying Out the Invention】 【0019】 <First Embodiment> In the manufacturing method of the composite materials 100a and 100b of the present embodiment, each process shown in FIG. 1 is part of the entire process. Further, FIG. 2 is a plan view of one composite material 100a of the present embodiment. Further, FIG. 3 is a plan view of another composite material 100b of the present embodiment. 【0020】 As shown in Figure 1, the composite materials 100a and 100b of this embodiment can be manufactured by performing a mixing step (S1), a carding step (S2), and a heating and pressing step (S3). The long or continuous composite material manufactured by the above steps can be cut into composite materials 100a and 100b of the desired length by performing a cutting step (S4). The above steps will be described in detail below. 【0021】 In the mixing step (S1) of this embodiment, carbon fibers and thermoplastic resin fibers are mixed in a mixing tank. An example of a mixing method that can be used in this embodiment is a method of mixing using a cylinder opener. 【0022】 The mixing step (S1) can typically form a first mixed material in which at least a portion of the carbon fibers are in contact with the thermoplastic resin fibers. More specifically, the thermoplastic resin fibers in this embodiment may be mixed with the carbon fibers in a substantially uniform manner. 【0023】 Furthermore, the carbon fiber used as one of the starting materials in this embodiment may be virgin carbon fiber (including scraps) immediately after its manufacture, or it may be waste material that has already been used. The use of recycled carbon fiber, or a mixed fiber of virgin material (including scraps of virgin material; the same applies hereinafter in this embodiment) and recycled carbon fiber as one of the starting materials is a preferred embodiment because it can be one means of solving social issues related to environmental impact. 【0024】 When a mixed fiber of virgin material and recycled carbon fiber is used, the volume ratio of the virgin material to the total mixed fiber is not limited. However, from the viewpoint of stabilizing or improving the strength (e.g., tensile strength or bending strength) of the sheet-like or strip-like composite material 100a, 100b finally manufactured using the mixed fiber, the volume ratio of the virgin material to the mixed fiber is preferably 20% by volume or more (more preferably 30% by volume or more). On the other hand, there is no particular upper limit to the volume ratio of the virgin material to the mixed fiber, but since the virgin material can be a factor that increases manufacturing costs, from the viewpoint of suppressing manufacturing costs (e.g., material costs) with high certainty, the volume ratio of the virgin material to the mixed fiber is preferably 30% by volume or less. 【0025】 As mentioned above, obtaining carbon fibers as a starting material from waste materials or recycled materials is a suitable embodiment because it can be one means of solving social issues related to environmental impact. Typical examples of such waste materials or recycled materials are carbon fiber reinforced plastics (CFRP), which are currently used in aircraft and wind turbine blades. Generally, carbon fiber reinforced plastics are materials in which virgin carbon fiber filaments are impregnated with a thermosetting resin, such as epoxy resin. Therefore, in order to obtain recycled carbon fibers as a starting material in this embodiment, it is necessary to extract carbon fibers (recycled carbon fibers) by, for example, heating and firing the waste materials or recycled materials to decompose and remove the thermosetting resin. 【0026】 In order to maintain high strength in the final composite materials 100a and 100b, it is preferable to keep the fiber length of the carbon fibers within a predetermined range. In other words, if the non-uniformity of the length of the carbon fibers increases, it becomes difficult to stabilize the tensile strength or bending strength of the final composite materials 100a and 100b. The characteristic technical effect of maintaining stable strength by keeping the fiber length of the composite materials 100a and 100b within a predetermined range is particularly applicable when using scraps of virgin material, or waste or recycled materials, as starting materials, as these materials are likely to be weaker in terms of mechanical strength (typically tensile strength) compared to virgin material. 【0027】 Furthermore, the carbon fibers used as starting materials for the manufacture of the composite materials 100a and 100b of this embodiment may include carbon fibers in a mixture of carbon fibers and a thermosetting resin such as epoxy resin, as exemplified by waste materials, or carbon fibers impregnated with a thermosetting resin such as epoxy resin. 【0028】 Furthermore, the thermoplastic resin fiber, which is another starting material in this embodiment, is not limited to any fiber made of a thermoplastic resin material that does not hinder the manufacture of the composite materials 100a and 100b in this embodiment. It should be noted that the thermoplastic resin fiber being at least one selected from the group consisting of polypropylene, polyamide, polycarbonate, polystyrene, and polyphenylene sulfide is a preferred embodiment from the viewpoint of achieving short-time molding of molded articles using composite materials 100a and 100b as starting materials, and / or from the viewpoint of achieving low-cost molding such as cold pressing. 【0029】 Incidentally, it is a preferred embodiment from at least one of the following four viewpoints (A) to (D): that carbon fibers with a fiber length of 20 mm or more and 100 mm or less (preferably 30 mm or more and 100 mm or less) contained in the composite materials 100a and 100b of this embodiment constitute 50 volume percent or more (preferably 60 volume percent or more) of all such carbon fibers (more specifically, the distribution of all fiber lengths of the carbon fibers) contained in the composite materials 100a and 100b. (A) In the mixing process of this embodiment, the carbon fibers and the thermoplastic resin fibers are mixed with high accuracy. (B) In the carding process (S2) described later, from the viewpoint of preventing with high certainty that the first mixed material formed in the mixing process (S1) will not be processed by the carding machine (for example, from the viewpoint of preventing the risk of the material falling out of the carding machine when the fiber length is less than 20 mm (or less than 30 mm for higher certainty) (C) In the carding process (S2) described later, the view is to reliably prevent carbon fibers from becoming entangled in the cylinder 50, walker 52 and / or stripper 54. (D) By adopting the carbon fibers of this embodiment, which have a short fiber length, the degree of freedom or ease of molding is increased, in other words, moldability or moldability is improved. Furthermore, if we consider the aforementioned point (A) from a different perspective, by adopting the numerical range of the fiber length, it is possible to more reliably suppress the uneven distribution of one material in the composite materials 100a and 100b. 【0030】 Next, the first mixed material, which is initially in the state of a mass of fibers formed by the mixing step (S1) described above, is subjected to a carding step (S2) using a carding machine (manufactured by Sanwa Textile Co., Ltd., model DS-C40ST) to form a continuous fiber web (in this embodiment, a continuous first mixed material 90). In this step, the first mixed material, which is a mixture of the carbon fibers and the thermoplastic resin fibers described above, is subjected to a carding process. The carding step (S2) in this embodiment is a step that aims to achieve a more homogeneous mixing of the carbon fibers and the thermoplastic resin fibers with high accuracy, and to align the direction or orientation (hereinafter, the term "direction" includes the meaning of "orientation") of the carbon fibers in the first mixed material to a predetermined range. 【0031】 Figure 4 is a schematic diagram of a part of the carding machine that performs the carding process (S2) in this embodiment. For the sake of explanation, in Figure 4, the arrows of the continuous first mixed material 90 indicate the direction in which it is continuously processed by the carding process (S2). Also, for the sake of explanation, the rotation directions of the rotating bodies such as the cylinder 50, walker 52, and doffer 56 are indicated by arrows in Figure 4. 【0032】 As shown in Figure 4, when the first mixed material is introduced into the carding machine, the following processes (i) and (ii) are performed to obtain a continuous first mixed material 90 that has become a fiber web. (i) After being sent to the cylinder 50, the first mixed material, which is in the state of a mass of fibers, is combed by four sets of walkers 52 as shown in Figure 4, and the first mixed material on the walkers 52 is stripped back to the cylinder 50. Together, these two systems further mix the multiple types of fibers in the continuous first mixed material 90 and reduce the variation in the orientation of the carbon fibers in the continuous first mixed material 90. (ii) Subsequently, the doffer 56 sends out the continuous first mixture 90 that has been stripped from the cylinder without any stagnation, regardless of whether it is concentrated or not. 【0033】 Furthermore, in the carding process (S2), the basis weight of the final sheet-like or strip-like composite material 100a, 100b is 5 g / m². 2 More than 150g / m 2 The following (more preferably 10 g / m²) 2 More than 50g / m 2 In order to adjust it to the following, a process is performed to quantify (make approximately constant) the processing amount per unit time (the amount of output in (ii) above). 【0034】 One of the notable features of the manufacturing process in this embodiment is that, after the carding process (S2) described above, the following heating and pressing process (S3) is performed without performing the following steps (1) to (4). In other words, in this embodiment, no process is performed to increase the thickness of the sheet-like or strip-like composite material 100a, 100b produced by the heating and pressing process (S3) described later, and / or to actively increase the degree of entanglement in the thickness direction (including integration). According to the inventors' studies and analysis, the inventors have found that the following steps (1) to (4) for the composite material 100a, 100b contribute little to improving the physical strength in the planar direction of the composite material 100a, 100b, or to improving the degree of orientation (i.e., reducing the maximum deviation of orientation) or improvement. Furthermore, the fact that productivity and / or yield can be significantly improved by not performing the following steps (1) to (4) is also an advantage compared to the prior art. (1) Contangle treatment by needle punching (2) Entanglement treatment by water flow treatment (3) Cross-layer processing or stacking by cross-layer processing (4) Folding process 【0035】 In this embodiment, after the carding process (S2), a heating and pressing process (S3) is performed. The heating and pressing process (S3) produces sheet-like or strip-like composite materials 100a and 100b by arranging each fiber in two dimensions and smoothing the surface. The composite materials 100a and 100b of this embodiment play an important role as materials (intermediate materials) or elements for forming various applications using the composite materials 100a and 100b. 【0036】 In the heating and pressing step (S3) of this embodiment, a continuous first mixed material, which has become a web of fibers formed by the carding step (S2) described above, is pressed by being sandwiched between two opposing cylindrical heating rollers and passed between the two heating rollers, thereby producing sheet-like or strip-like (or "tape-like") composite materials 100a, 100b. 【0037】 More specifically, a typical example of the set temperature for the two heating rollers in this embodiment is 180°C to 200°C. Furthermore, it is preferable to use SUS material as the base material for the heating rollers. The material of the surface of the base material, i.e., the surface in contact with the first mixed material, is preferably silicone or PTFE (polyfluorocarbon) resin. Additionally, setting the diameter of the heating rollers to 100 mm to 300 mm and maintaining their rotation speed such that the sheet-like or strip-like composite materials 100a and 100b move at 0.5 m / min to 10 m / min is a preferred configuration for accurately producing the sheet-like or strip-like composite materials 100a and 100b from the first mixed material. A typical example of the pressure applied to the first mixed material passing between the heating rollers is 3 kN to 7 kN. 【0038】 In this embodiment, by optimizing each of the above numerical ranges, when manufacturing continuous sheet-like or strip-like composite materials 100a and 100b from a continuous first mixed material 90 that has become a fiber web, it is possible to achieve an excellent production speed of 1 m / min to 4 m / min, which is applicable to mass production. 【0039】 As described above, after the carding process (S2) is performed, the heating and pressing process (S3) is carried out without performing any of the processes (1) to (4) described above. Therefore, in a preferred example of this embodiment, the continuous first mixed material 90, which has become a web of fibers formed by the carding process (S2), is configured to be sent directly to the heating and pressing process (S3) using a known moving mechanism (such as a conveyor). Therefore, it is worth noting that in this embodiment, the first mixed material is subjected to a continuous process of the carding process (S2) and the heating and pressing process (S3). Through this continuous process, composite materials 100a and 100b can be manufactured rapidly. In addition, by enabling continuous processing, if cutting of the composite materials 100a and 100b is required, a cutting process (S4) can be performed after the heating and pressing process (S3) to cut the composite materials 100a and 100b to the required length according to the specifications of the application product to which they are intended to be used, thus providing greater flexibility in the composition or design of the composite materials 100a and 100b. On the other hand, by introducing a process after the heating and pressing process (S3), for example, to continuously wind up the sheet-like or strip-like composite materials 100a and 100b that are continuously fed out using a winding roll, it is also possible to manufacture long lengths of composite materials 100a and 100b. 【0040】 Note that the heat pressing step (S3) of the present embodiment is not limited to the process using the above two heating rollers. For example, it is also possible to adopt another aspect in which a continuous first mixture 90 in the form of a fiber web fed by a flat belt conveyor is pressed using one heating roller. Further, immediately before pressing the first mixture by sandwiching it between two opposing cylindrical rollers at room temperature, for example, by temporarily accommodating the first mixture in a heated chamber under air or by blowing hot air onto the first mixture, heating the first mixture is also a preferred aspect that can be adopted as the heat pressing step (S3). Therefore, in the heat pressing step (S3) of the present embodiment for manufacturing the sheet-like or strip-like (or tape-like) composite materials 100a, 100b from the first mixture, it is not necessary that the heat treatment and the pressing treatment are necessarily performed simultaneously. 【0041】 By performing each of the above steps, the basis weight is 5 g / m 2 or more and 150 g / m 2 or less (more preferably, 10 g / m 2 or more and 50 g / m 2 or less), and the thickness is thinly processed to be 0.1 mm or more and 3 mm or less (more preferably 0.3 mm or more and 3 mm or less, even more preferably 1 mm or more and 2 mm or less), so that sheet-like or strip-like composite materials 100a, 100b can be manufactured. Note that since the composite material having the above-mentioned small basis weight and thin thickness is the minimum unit as an intermediate material, it is particularly noteworthy that the degree of freedom in designing an application product using this composite material as an intermediate material can be significantly increased. 【0042】 Note that an example of a molded product that can be manufactured by using the composite materials 100a, 100b of the present embodiment as a material (intermediate material) is shown in FIG. 5. FIG. 5 is a photograph showing examples of two molded products of the same shape formed using the composite materials 100a, 100b of the present embodiment as starting materials. Specifically, the molded product is an example of an application product that is a thermoplastic molded product by cold pressing. 【0043】 <Evaluation of Composite Materials 100a, 100b> [1] Evaluation of the orientation of carbon fibers contained in composite materials 100a and 100b Incidentally, when the inventors measured the direction of carbon fibers (including carbon fibers in which at least a portion is in contact with thermoplastic resin fibers (i.e., carbon fibers that are in contact before the thermoplastic resin fibers dissolve) and carbon fibers impregnated with the thermoplastic resin (i.e., carbon fibers that are in contact after the thermoplastic resin fibers dissolve); the same applies hereinafter) in an example of a sheet-like or strip-like composite material 100a, 100b formed by performing the heating and pressing process (S3) of this embodiment, using an X-ray CT scanner (Shimadzu Corporation, model SMX-225CT), they obtained some very interesting results. 【0044】 Figure 6 shows (a) the measurement results of an X-ray CT scanner for an example of composite materials 100a and 100b of this embodiment, and (b) the measurement results of a comparative example. As the comparative example shown in Figure 6(b), commercially available nonwoven fabrics that have undergone (1) entanglement treatment by needle punching and (3) cross-layer treatment or lamination treatment by cross-layering were used. 【0045】 The other measurement conditions for the measurement using the X-ray CT device described above are as follows: <Device name> Manufactured by Shimadzu Corporation ·Device name: inspeXio ·Model: SMX-225CT FPD HR Plus <Measurement conditions> After cutting the sample into 10mm x 5mm pieces, the following arrangement settings are made within the above-mentioned apparatus. (a-1) Distance between detector and X-ray source: 800 mm (a-2) Distance between the center of the sample and the X-ray source: 11mm~15mm The imaging conditions are as follows: (b-1) X-ray voltage and current: 70kV, 70μA (b-2) Resolution: 2048(pixels)×2048(pixels) (b-3) Sample rotation speed: 1 time (360°) (b-4) Total scan time: 600 seconds 【0046】 As shown in Figure 6, measurements using the X-ray CT scanner confirmed that most of the carbon fibers contained in the composite materials 100a and 100b of this embodiment are not oriented in the z direction, i.e., in the thickness direction of the composite materials 100a and 100b. Further investigation revealed that, in the xy plane shown in Figure 6, the orientation of the carbon fibers in the y direction, which represents the longitudinal direction of the continuous strip-shaped or sheet-shaped composite materials 100a and 100b, is extremely dominant over the orientation in the x direction; in other words, the carbon fibers are almost aligned in the y direction. 【0047】 On the other hand, in the comparative example, while the region indicated by the three thick arrows is particularly prominent, many fibers were also observed that were oriented not only in the y-direction but also in the z-direction. 【0048】 Further investigation revealed that the mass of the carbon fibers in the thickness direction observed in any 5 mm × 10 mm field of view of the sheet-like or strip-like composite materials 100a and 100b in plan view was a very small value, between 1% and 5% of the total mass of the carbon fibers, including in directions other than the thickness direction (i.e., directions along the plane of the composite materials 100a and 100b). 【0049】 As described above, it was found that one of the features of the composite materials 100a and 100b is that most of the carbon fibers contained in the composite materials 100a and 100b are oriented in a direction along the plane of the sheet-like or strip-like composite materials 100a and 100b, and that even within that plane, they are oriented in the longitudinal direction of the continuous strip-like or sheet-like composite materials 100a and 100b. 【0050】 Therefore, one preferred embodiment is that by stacking multiple composite materials 100a and 100b, it is possible to freely design the physical strength or rigidity in the planar direction (in other words, a direction other than the thickness direction) of the sheet-like composite materials 100a and 100b, or in the longitudinal direction of the strip-like composite materials 100a and 100b, and in the direction perpendicular to the longitudinal direction along the plane of the strip. 【0051】 <Other Embodiments> By the way, in the above-described embodiment, composite materials 100a and 100b are used in which carbon fibers with a fiber length of 20 mm or more and 100 mm or less (preferably 30 mm or more and 100 mm or less) make up 50 volume percent or more (preferably 60 volume percent or more) of all carbon fibers. However, from the viewpoint of at least one of the four points (A) to (D) already mentioned, it is a more preferred embodiment in which carbon fibers with a fiber length of 50 mm or more and 80 mm or less make up 40 volume percent or more of all carbon fibers. 【0052】 Furthermore, in the above-described embodiment, the fiber length of the thermoplastic resin fiber is not limited as long as the effects of the embodiment are achieved. However, in the carding process (S2), from the viewpoint of reliably preventing the first mixed material formed in the mixing process (S1) from being removed from the processing target of the carding machine, and reliably preventing the composite material from becoming entangled in the cylinder and / or doffer, it is a preferred embodiment to set the fiber length of the thermoplastic resin fiber to the same numerical range as the fiber length of the carbon fiber. An example of the first mixed material being removed from the processing target of the carding machine is when the composite material moving during the carding process (S2) is not taken over by the carding machine, for example, from the cylinder to the doffer. 【0053】 The embodiments and examples described above do not limit the present invention in any way. Modifications that fall within the scope of the present invention, including other combinations of the embodiments and examples described above, are also included in the claims. [Industrial applicability] 【0054】 The composite material and method for manufacturing the composite material of the present invention can be widely used as a functional material containing carbon fibers or a method for manufacturing the same for a variety of applications, such as components for sports equipment including bicycles, wind power generation components, components for electrical appliances or household goods, building components, aerospace-related components including rocket parts, or prepreg materials before they become molded automobile parts. [Explanation of symbols] 【0055】 50 cylinders 52 Walker 54 Strippers 56 Doffer 90 Continuous first mixture 100a,100b composite material

Claims

[Claim 1] carbon fiber and, A composite material that is not laminated and contains thermoplastic resin fibers, It is in the form of a sheet or strip, Weight: 10 g / m ２ 150g / m or more ２ The following: The thickness is 0.1 mm or more and 3 mm or less, and X-ray CT measurement of the sheet-like or strip-like composite material shows that the carbon fibers in the thickness direction observed in any 5 mm × 10 mm field of view are between 1% by mass and 5% by mass relative to all carbon fibers. Composite material. [Claim 2] The carbon fibers having a fiber length of 20 mm or more and 100 mm or less constitute 50 volume or more of all said carbon fibers. The composite material according to claim 1. [Claim 3] The thermoplastic resin fiber is at least one selected from the group consisting of polypropylene, polyamide, polycarbonate, polystyrene, and polyphenylene sulfide. The composite material according to claim 1 or claim 2. [Claim 4] The carbon fiber is a mixed fiber of virgin material (including scraps of the virgin material) and recycled carbon fiber. The composite material according to claim 1 or claim 2. [Claim 5] The carbon fiber is recycled carbon fiber, The composite material according to claim 1 or claim 2. [Claim 6] A carding process involves carding a mixture of carbon fibers and thermoplastic resin fibers. The carding step is followed by a heating and pressing step in which the carded mixture is heated and pressed without the following steps (1) to (4): The heating and pressing step forms a sheet-like or strip-like composite material having a basis weight of 10 g / m² or more and 150 g / m² or less. A method for manufacturing composite materials. (1) Contangle treatment by needle punching (2) Entanglement treatment by water flow treatment (3) Cross-layer processing or stacking by cross-layer processing (4) Folding process [Claim 7] The thickness of the composite material is 0.3 mm or more and 3 mm or less. A method for manufacturing a composite material according to claim 6. [Claim 8] The carbon fiber is a carbon fiber having a fiber length of 20 mm or more and 100 mm or less. A method for manufacturing a composite material according to claim 6 or claim 7. [Claim 9] The carbon fiber is recycled carbon fiber. A method for manufacturing a composite material according to claim 6 or claim 7. [Claim 10] The carbon fiber is a mixed fiber of virgin material (including scraps of the virgin material) and recycled carbon fiber. A method for manufacturing a composite material according to claim 6 or claim 7.

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