Composite material and method for manufacturing composite material

Abstract

To provide a method of producing a composite material excellent in strength.SOLUTION: Provided is a method of producing a composite material 10 which includes a carbon-fiber sheet 20, resins, and carbon nanotubes, the method including: a laminate forming step of forming a laminate 50 by laminating a first resin sheet 35A, a first carbon nanotube sheet 45A, the carbon-fiber sheet 20, a second carbon nanotube sheet 45B, and a second resin sheet 35B in this order; and an impregnation step of pressing the laminate 50 in a lamination direction and heating the laminate 50 to make the resin contained in the first resin sheet 35A and the resin contained in the second resin sheet 35B flow and impregnate the carbon-fiber sheet 20 with the resins.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a composite material and a method for manufacturing the composite material. More specifically, the present invention relates to a composite material including a carbon fiber sheet and carbon nanotubes, and a method for manufacturing the same.

Background Art

[0002] A carbon fiber sheet formed by bundling a plurality of carbon fibers is lightweight and high-strength, and is used in various fields. Further, as shown in Patent Document 1, in order to further increase the strength of the carbon fiber sheet, a carbon fiber reinforced layer reinforced with carbon fibers and a reinforcing layer containing carbon nanotubes (CNTs) are laminated and formed into a carbon nanotube reinforced fiber structure (hereinafter referred to as a composite material).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Patent Document 1 describes a method for manufacturing a composite material in which a fiber prepreg sheet obtained by impregnating carbon fibers with a resin and semi-curing the resin, and a semi-cured resin sheet obtained by mixing carbon nanotubes with the resin are alternately laminated in a plurality of sheets to form a laminate, and then the fiber prepreg sheet and the semi-cured resin sheet are pressure-bonded. However, in such a method, an interface exists between the carbon fiber reinforced layer containing carbon fibers and the reinforcing layer containing CNTs. Therefore, for example, when a strong impact is received from the lamination direction, interface peeling may occur, and the carbon fiber reinforced layer and the reinforcing layer may be easily separated. Therefore, it is desired to improve the integrity of the entire composite material and increase the strength (for example, compressive strength).

[0005] This invention has been made in view of the above, and its object is to provide a composite material with excellent strength and a method for manufacturing the same. [Means for solving the problem]

[0006] The present invention relates to a method for manufacturing a composite material comprising a carbon fiber sheet, a resin, and carbon nanotubes, and includes a laminate formation step of forming a laminate by stacking a first resin sheet, a first carbon nanotube sheet, the carbon fiber sheet, a second carbon nanotube sheet, and a second resin sheet in this order, and an impregnation step of pressing the laminate in the stacking direction and heating the laminate to cause the resin contained in the first resin sheet and the resin contained in the second resin sheet to flow and impregnate each of them up to the carbon fiber sheet.

[0007] According to the manufacturing method of the present invention, by pressing and heating the laminate in the lamination direction, on one side of the carbon fiber sheet, the resin contained in the first resin sheet softens, for example, and flows in the lamination direction, piercing a portion of the first carbon nanotube sheet. Then, the resin flows further in the lamination direction, incorporating the carbon nanotubes, and impregnates the carbon fiber sheet. Similarly, on the other side of the carbon fiber sheet, the resin contained in the second resin sheet softens, for example, and flows in the lamination direction, piercing a portion of the second carbon nanotube sheet. Then, it flows further in the lamination direction, incorporating the carbon nanotubes, and impregnates the carbon fiber sheet. As a result, the carbon nanotubes are firmly entangled with the carbon fiber sheet and fixed to the carbon fiber sheet by the resin. That is, the carbon fiber sheet and the carbon nanotubes are firmly fixed not only by the chemical bonding force of the resin, but also by entanglement. Therefore, compared to the manufacturing method in Patent Document 1, for example, the carbon nanotubes are relatively less likely to peel off from the carbon fibers, and the strength of the composite material can be increased.

[0008] The composite material according to the present invention comprises a carbon fiber sheet having one surface and another surface, a resin, and carbon nanotubes, wherein the carbon nanotubes are intertwined and fixed by the resin on the one surface and the other surface of the carbon fiber sheet, and in a cross-sectional view in a direction perpendicular to the carbon fiber sheet, at least a portion of the region has a laminated structure consisting of five layers in which the resin layer, the layer containing the carbon nanotubes, the layer containing the carbon fiber sheet, the layer containing the carbon nanotubes, and the resin layer are stacked in this order.

[0009] In the composite material according to the present invention, carbon nanotubes are intertwined with one surface and the other surface of a carbon fiber sheet, and these carbon nanotubes are fixed to the carbon fiber sheet by a resin. That is, the carbon fiber sheet and carbon nanotubes are fixed not only by the chemical bonding force of the resin, but also by the intertwining. Therefore, the strength of the composite material can be relatively increased compared to the case where the carbon fiber sheet and carbon nanotubes are bonded only by the chemical bonding force of the resin. Furthermore, at least a portion of the composite material according to the present invention is covered with a layer of resin. Therefore, the strength can be relatively increased compared to the case where carbon nanotubes or carbon fibers are exposed on the outer surface, and interfacial delamination is less likely to occur, for example, when subjected to a strong impact from the lamination direction. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a composite material with excellent strength and a method for manufacturing the same. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a flowchart showing a method for manufacturing composite materials. [Figure 2] Figure 2 is a cross-sectional view showing a laminate according to one embodiment. [Figure 3]Figure 3 is a cross-sectional view showing a state in which a first carbon nanotube sheet and a second carbon nanotube sheet are laminated on the upper and lower surfaces of a carbon fiber sheet, respectively. [Figure 4] Figure 4 is a cross-sectional view showing a portion of the composite material. [Modes for carrying out the invention]

[0012] Embodiments of the composite material according to the present invention will be described below with reference to the drawings. Matters other than those specifically mentioned herein that are necessary for carrying out the present invention can be understood as design matters for those skilled in the art based on the prior art. The present invention can be carried out based on the contents disclosed herein and the common technical knowledge in the art. Furthermore, the embodiments described herein are not intended to particularly limit the present invention. In addition, in the following drawings, the same reference numerals are used for members and parts that perform the same function, and redundant explanations are omitted or simplified as appropriate. Furthermore, in this specification, the notation "X~Y" (where X and Y are arbitrary numerical values) indicating a range includes not only the meaning of "greater than X" and "less than Y", but also the meaning of "greater than X" and "less than Y".

[0013] <Method for manufacturing composite material 10> First, the manufacturing method of the composite material 10 will be described. Figure 1 is a flowchart of the manufacturing method of the composite material 10. The manufacturing method of this embodiment includes a laminate formation step (step S100) and an impregnation step (step S200).

[0014] In the laminate formation process (step S100), as shown in Figure 2, the first resin sheet 35A, the first carbon nanotube sheet 45A, the carbon fiber sheet 20, the second carbon nanotube sheet 45B, and the second resin sheet 35B are stacked in this order to form a laminate 50. Therefore, first, the carbon fiber sheet 20, the first resin sheet 35A and the second resin sheet 35B containing resin, and the first carbon nanotube sheet 45A and the second carbon nanotube sheet 45B containing carbon nanotubes are prepared.

[0015] The carbon fiber sheet 20 is a sheet-like component in which multiple carbon fibers are arranged. The carbon fiber sheet 20 may be a porous molded body having voids into which resin can be impregnated in the impregnation process (step S200) described later. The thickness (average thickness; the same applies hereinafter) of the carbon fiber sheet 20 is, for example, 1 μm to 1000 μm, 10 μm to 100 μm, and in one example, 100 μm. The carbon fiber sheet 20 may be the same as those conventionally used for this type of application, and there are no particular restrictions. Examples of carbon fiber sheets 20 include carbon fiber nonwoven fabrics and woven fabrics. The carbon fiber sheet 20 is preferably composed of carbon fibers. Examples of carbon fiber types include PAN-based carbon fibers made from polyacrylonitrile, and pitch-based carbon fibers made from pitch such as petroleum pitch. The average diameter of the carbon fibers is generally several microns to several tens of microns, for example, 1 μm to 50 μm.

[0016] The first resin sheet 35A and the second resin sheet 35B have the same configuration. That is, the first resin sheet 35A and the second resin sheet 35B are made of the same resin and have the same size and thickness. However, the first resin sheet 35A and the second resin sheet 35B may have different configurations. For example, the first resin sheet 35A and the second resin sheet 35B may differ in at least one of the following: the type of resin and the properties (size, thickness, etc.). Hereafter, the first resin sheet 35A and the second resin sheet 35B will be collectively referred to as resin sheet 35.

[0017] The thickness of the resin sheet 35 is preferably greater than the thickness of the carbon nanotube sheet 45. The thickness of the resin sheet 35 is typically 10 μm to 1000 μm, for example, 10 μm to 200 μm, and in one example, 100 μm. Depending on the thickness of the carbon nanotube sheet 45, setting the thickness of the resin sheet 35 within the above range prevents excess resin, making it easier for the resin to penetrate the carbon nanotube sheet 45 and to intertwine with the carbon fiber sheet 20 in the impregnation process (step S200) described later. Therefore, the effects of the technology disclosed herein can be demonstrated at a high level. The resin sheet 35 is preferably substantially (95% by mass or more, 98% by mass or more, preferably 100% by mass) composed of resin. The resin sheet 35 is preferably free of binders. This makes it easier for the carbon nanotubes to physically intertwine in the impregnation process (step S200) described later.

[0018] The resin sheet 35 can be any conventionally known material without particular limitation. The resin constituting the resin sheet 35 may be a thermosetting resin or a thermoplastic resin. The thermosetting resin can be any resin material that hardens with heat, and conventionally known materials can be used without particular limitation. Examples include epoxy resin, unsaturated polyester resin, vinyl ester resin, phenol resin, melamine resin, urea resin, cyanate ester resin, and bismaleimide resin. The thermoplastic resin can be any thermoplastic resin material, and conventionally known materials can be used without particular limitation. Examples include polyolefin resin (e.g., polyethylene and polypropylene), polyamide resin (e.g., polyamide 6, polyamide 66), polycarbonate resin, and polyphenylene sulfide resin. It is preferable that the resin constituting the resin sheet 35 is a thermoplastic resin.

[0019] The first carbon nanotube sheet 45A and the second carbon nanotube sheet 45B have the same configuration here. That is, the first carbon nanotube sheet 45A and the second carbon nanotube sheet 45B are composed of the same carbon nanotubes and have the same size and the same thickness. However, the first carbon nanotube sheet 45A and the second carbon nanotube sheet 45B may have different configurations. For example, at least one of the type and properties (size, thickness, etc.) of the carbon nanotubes in the first carbon nanotube sheet 45A and the second carbon nanotube sheet 45B may be different. Hereinafter, the first carbon nanotube sheet 45A and the second carbon nanotube sheet 45B are collectively referred to as the carbon nanotube sheet 45.

[0020] The thickness of the carbon nanotube sheet 45 is typically thinner than the thickness of the carbon fiber sheet 20. The thickness of the carbon nanotube sheet 45 may be, for example, 1 / 20000 to 1 / 10 times, or 1 / 200 to 1 / 5 times the thickness of the carbon fiber sheet 20. It is preferable that the thickness of the carbon nanotube sheet 45 is thinner than the thickness of the resin sheet 35. It is preferable that the thickness of the first carbon nanotube sheet 45A is thinner than the thickness of the first resin sheet 35A. It is preferable that the thickness of the second carbon nanotube sheet 45B is thinner than the thickness of the second resin sheet 35B. Thereby, in the impregnation process (step S200) described later, it becomes easier for the resin to break through the carbon nanotube sheet 45. The thickness of the carbon nanotube sheet 45 is preferably 100 μm or less, for example, 0.005 μm to 100 μm, 0.1 μm to 10 μm, 0.5 μm to 5 μm, and in one example, it is 2 μm. Depending on the pressurization conditions and the like in the impregnation process (step S200) described later, when the thickness of the carbon nanotube sheet 45 is thicker than 100 μm, it becomes difficult for the resin to impregnate the carbon nanotube sheet 45, and there is a risk that the strength of the composite material 10 will decrease.

[0021] As the carbon nanotube sheet 45, a conventionally known one can be used without particular limitation. The carbon nanotube sheet 45 can be a porous molded body having voids into which the resin can be impregnated in an impregnation step (step S200) described later. Thereby, in the impregnation step (step S200) described later, it becomes easier for the resin to break through the carbon nanotube sheet 45 starting from the voids. The carbon nanotube sheet 45 is preferably substantially (95% by mass or more, 98% by mass or more, preferably 100% by mass) composed of carbon nanotubes. The carbon nanotube sheet 45 preferably does not contain a binder. Thereby, in the impregnation step (step S200) described later, it becomes easier to physically entangle with the carbon fiber sheet 20. The carbon nanotube of the present embodiment is fibrous carbon having a structure in which graphene forming a carbon hexagonal network is rolled into a tube shape. The carbon nanotube has a high aspect ratio and excellent properties such as mechanical strength, conductivity, and heat conductivity. Examples of the type of carbon nanotube include single-walled carbon nanotubes formed of one layer of graphene, multi-walled carbon nanotubes formed of two or more layers of graphene, and the like.

[0022] The properties of the carbon nanotube are not particularly limited. For example, the average length can be approximately 250 μm or less, typically 0.001 μm to 250 μm, for example, about 0.1 μm to 3 μm. Also, the average diameter of the carbon nanotube is typically smaller than the average diameter of the carbon fibers contained in the carbon fiber sheet 20, and can be, for example, approximately 0.1 nm to 100 nm, and in one example, about 10 nm. By satisfying at least one (preferably both) of the above-described properties, it becomes easier to entangle with the carbon fiber sheet 20 in the impregnation step (step S200) described later.

[0023] In this embodiment, the laminate formation step (step S10) includes a first lamination step (step S110) and a second lamination step (step S120). In the first lamination step (step S110), as shown in Figure 3, the first carbon nanotube sheet 45A is superimposed on the upper surface 20A of the carbon fiber sheet 20, and the second carbon nanotube sheet 45B is superimposed on the lower surface 20B of the carbon fiber sheet 20. This forms a pre-laminated laminate consisting of three sheets, with the first carbon nanotube sheet 45A, the carbon fiber sheet 20, and the second carbon nanotube sheet 45B being laminated in this order. Note that the upper surface 20A is an example of "one surface," and the lower surface 20B is an example of "the other surface."

[0024] Next, in the second lamination step (step S120), as shown in Figure 2, the first resin sheet 35A is superimposed on the upper surface 45AA of the first carbon nanotube sheet 45A, which is laminated on the upper surface 20A of the carbon fiber sheet 20, and the second resin sheet 35B is superimposed on the lower surface 45BB of the second carbon nanotube sheet 45B, which is laminated on the lower surface 20B of the carbon fiber sheet 20. In this way, a laminate 50 is formed in which the first resin sheet 35A, the first carbon nanotube sheet 45A, the carbon fiber sheet 20, the second carbon nanotube sheet 45B, and the second resin sheet 35B are laminated in this order from the top.

[0025] Next, in the impregnation step (step S200), the laminate 50 is pressed in the lamination direction and heated to soften and flow a portion of the resin contained in the two resin sheets 35, thereby impregnating the carbon fiber sheet 20. At this time, it is preferable to press the laminate 50 so as to sandwich it from one side (here, from above) and the other side (here, from below) in the lamination direction, and to heat the first resin sheet 35A and the second resin sheet 35B. The laminate 50 is heated while being pressed in the lamination direction by, for example, a heating press.

[0026] The heating and pressing conditions can be appropriately adjusted depending on the properties of the resin contained in the first resin sheet 35A and the second resin sheet 35B (e.g., the type of resin) and the thickness of each sheet. Therefore, although not particularly limited, the pressing pressure per unit area is, for example, 0.1 MPa to 10 MPa. The pressing temperature during heating should be a temperature that softens or melts the resin contained in the first resin sheet 35A and the second resin sheet 35B, for example, if the resin is a thermoplastic resin. The pressing temperature during heating is typically higher than the softening point (preferably the melting point) of the resin contained in the first resin sheet 35A and the second resin sheet 35B, for example, 50°C to 250°C. In this way, as the resin sheet 35 is heated and pressed, the resin in the resin sheet 35 flows in the lamination direction, and the pressure at this time pierces the carbon nanotube sheet 45. Then, the flowing resin continues to flow in the stacking direction, incorporating the carbon nanotubes contained in the carbon nanotube sheet 45, and impregnates the carbon fiber sheet 20.

[0027] In the impregnation step (step S200) of this embodiment, it is preferable to further apply ultrasonic vibration to the laminate 50. For example, ultrasonic vibration is further applied to the laminate 50 while it is being pressed in the lamination direction by a heating press and heated. The ultrasonic frequency is, for example, 1 kHz to 30 kHz. By applying ultrasonic vibration to the laminate 50, the carbon nanotubes contained in the carbon nanotube sheet 45 are loosened and become easier to disperse in the resin. As a result, the resin of the resin sheet 35 better incorporates the carbon nanotubes and impregnates them into the carbon fiber sheet 20.

[0028] When the resin is a thermosetting resin, it is preferable to heat the laminate 50 after pressing it with a heating press (i.e., after the resin moves to the carbon fiber sheet 20 while incorporating the carbon nanotube sheet 45 and impregnates the carbon fiber sheet 20) to cure the resin. On the other hand, when the resin is a thermoplastic resin, it is preferable to heat the laminate 50 at the same time as pressing it with a heating press so that the molten (including reduced viscosity) resin sheet 35 impregnates the carbon fiber sheet 20 while incorporating the carbon nanotube sheet 45. After that, it is preferable to cool the laminate 50 to cure the resin. The composite material 10 can be manufactured in the manner described above. The composite material 10 obtained in this manner can maintain the five-layer laminated structure described later.

[0029] <Composite Material 10> The composite material 10 disclosed herein comprises a carbon fiber sheet 20, a resin, and carbon nanotubes. The composite material 10 is a sheet-like intermediate material (prepreg) used, for example, in the manufacture of FRP (Fiber Reinforced Plastics). The overall thickness (average thickness; the same applies hereinafter) of the composite material 10 is approximately 200 μm to 5000 μm, for example, 300 μm to 1000 μm. The composite material 10 can be suitably manufactured, for example, by the manufacturing method described above. The carbon fiber sheet 20 has one surface and the other surface.

[0030] On one and the other surface of the carbon fiber sheet 20, the carbon nanotubes are entangled with the carbon fiber sheet 20. More specifically, the carbon nanotubes are entangled with the carbon fibers of the carbon fiber sheet 20. Multiple carbon nanotubes are dispersed and entangled on the surface of the carbon fiber sheet 20. The entanglement of the carbon nanotubes with the carbon fiber sheet 20 can be confirmed, for example, by scanning electron microscope (SEM) images. The carbon nanotubes may be entangled with the carbon fibers by mechanical bonding forces or by physical bonding forces such as intermolecular forces. At least a portion of the carbon nanotubes are fixed to the carbon fiber sheet 20 by resin.

[0031] A portion of the resin impregnates the carbon fiber sheet 20. The resin is a binding component that chemically integrates the carbon fiber sheet 20 and the carbon nanotubes. The resin plays the role of a matrix material.

[0032] As shown in Figure 1, the composite material 10 of this embodiment has a five-layer laminated structure in which a resin layer 30, a layer 40 containing carbon nanotubes, a carbon fiber sheet 20, a layer 40 containing carbon nanotubes, and a resin layer 30 are stacked in this order in a direction perpendicular to the carbon fiber sheet 20 (more specifically, a direction perpendicular to the plane of the carbon fiber sheet 20), due to, for example, the manufacturing method described above. That is, in the laminated structure, the resin layer 30 is located on the outermost side, the carbon fiber sheet 20 is located on the innermost side, and the layer 40 containing carbon nanotubes is located between the carbon fiber sheet 20 and the resin layer 30. In the laminated structure, the resin layer 30 constitutes the outer surface of the composite material 10 (one side and the other side in the lamination direction).

[0033] In this specification, a "layer" does not necessarily have to have a clear boundary; for example, it may be a layer with a concentration gradient in which the proportion of the contained components changes gradually. Also, in a laminated structure, a part of the layer 40 containing carbon nanotubes and a part of the layer 30 made of resin may overlap. However, in that case, most of the layer 40 containing carbon nanotubes is located relatively on the inside, and most of the layer 30 made of resin is located relatively on the outside.

[0034] Furthermore, in the laminated structure, a portion of the carbon fiber sheet 20 and a portion of the layer 40 containing carbon nanotubes may overlap. For example, in the manufacturing method described above, since the carbon nanotubes flow together with the resin and become entangled with the carbon fiber sheet 20, it is expected that the sum of the thicknesses of the layer 40 containing carbon nanotubes and the carbon fiber sheet 20 in the composite material 10 will be smaller than the sum of the thicknesses of the carbon nanotube sheet 45 and the carbon fiber sheet 20 in the lamination process. However, in that case, most of the carbon fiber sheet 20 (especially the portion with the highest concentration of carbon fibers) is located relatively on the inside, and most of the layer 40 containing carbon nanotubes (especially the portion with the highest concentration of carbon nanotubes) is located relatively on the outside.

[0035] In any cross-sectional view in a direction perpendicular to the carbon fiber sheet 20, the laminated structure preferably occupies approximately 1 / 3 or more (33% or more), and more preferably half (50%) or more, of the total cross-sectional area when the composite material 10 is cut in the thickness direction, with 100% being the total cross-sectional area. The proportion occupied by the laminated structure may be, for example, 80% or less, or 70% or less. The laminated structure may be substantially maintained throughout the entire composite material 10 (95% or more, or 98% or more).

[0036] The proportion of the layered structure can be confirmed, for example, by scanning electron microscope (SEM) images. More specifically, first, the composite material 10 is embedded and polished to create a cross-section. Next, the cross-section of the composite material 10 is observed with an SEM, and an SEM image is acquired at a magnification such that the entire thickness fits within a single field of view. Then, using commercially available image resolution software, the area of ​​the portion where the five-layered structure is maintained is determined, and the proportion (%) of this area is calculated when the total cross-sectional area of ​​the composite material 10 is set to 100%.

[0037] Furthermore, in parts of the composite material 10 other than the laminated structure, for example, the resin contained in the resin sheet 35 (first resin sheet 35A and / or second resin sheet 35B) may not be entirely impregnated into the carbon nanotube sheet 45 or carbon fiber sheet 20, and the outer surface may not be covered with a layer 30 made of resin. For example, the outer surface of the composite material 10 may be composed of a layer 40 containing carbon nanotubes. Also, in the inner part of the composite material 10 in the thickness direction, similar to the laminated structure, it is preferable that the carbon nanotubes are intertwined with the carbon fiber sheet 20, and that the carbon nanotubes are fixed to the carbon fiber sheet 20 by the resin impregnated into the carbon fiber sheet 20.

[0038] As described above, in the composite material 10 of this embodiment, carbon nanotubes are intertwined on the upper surface 20A and lower surface 20B of the carbon fiber sheet 20, and the carbon nanotubes are fixed to the carbon fiber sheet 20 by the resin. That is, the carbon fiber sheet 20 and the carbon nanotubes are fixed not only by the chemical bonding force of the resin, but also by entanglement. Therefore, the strength of the composite material 10 can be increased relatively compared to the case in which the carbon fiber sheet 20 and the carbon nanotubes are bonded only by the chemical bonding force of the resin. Furthermore, at least a part of the composite material 10 is covered with a layer 30 made of resin. Therefore, the strength can be increased relatively compared to the case in which the carbon nanotubes or carbon fibers are exposed on the outer surface, and interfacial delamination is less likely to occur, for example, when subjected to a strong impact from the lamination direction.

[0039] In the composite material 10 of this embodiment, when viewed in cross-section, the laminated structure accounts for 1 / 3 or more of the total cross-sectional area of ​​the composite material 10, which is considered to be 100%. According to the above embodiment, the strength of the carbon fiber sheet 20 can be increased by carbon nanotubes, while the layer 40 containing the carbon fiber sheet 20 and carbon nanotubes can be more reliably bonded by the resin.

[0040] In the composite material 10 of this embodiment, the resin is a thermoplastic resin. According to the above embodiment, the strength of the composite material 10 can be further increased.

[0041] In the manufacturing method of this embodiment, by pressing and heating the laminate 50 in the lamination direction, the resin contained in the first resin sheet 35A on the upper surface 20A of the carbon fiber sheet 20 softens, flows in the lamination direction, and penetrates a portion of the first carbon nanotube sheet 45A. Then, the resin flows further in the lamination direction, incorporating the carbon nanotubes, and impregnates the carbon fiber sheet 20. Similarly, on the lower surface 20B of the carbon fiber sheet 20, the resin contained in the second resin sheet 35B softens, flows in the lamination direction, and penetrates a portion of the second carbon nanotube sheet 45B. Then, it flows further in the lamination direction, incorporating the carbon nanotubes, and impregnates the carbon fiber sheet 20. As a result, the carbon nanotubes are firmly entangled with the carbon fiber sheet 20 and fixed to the carbon fiber sheet 20 by the resin. That is, the carbon fiber sheet 20 and the carbon nanotubes are firmly fixed not only by the chemical bonding force of the resin, but also by entanglement. Therefore, carbon nanotubes become less likely to peel off from carbon fibers, and the strength of the composite material 10 can be increased.

[0042] In the manufacturing method of this embodiment, the laminate formation step (step S100) includes a first lamination step (step S110) in which a first carbon nanotube sheet 45A and a second carbon nanotube sheet 45B are laminated on the upper surface 20A and lower surface 20B of the carbon fiber sheet 20, respectively, and a second lamination step (step S120) in which a first resin sheet 35A and a second resin sheet 35B are laminated on the upper surface 45AA of the first carbon nanotube sheet 45A laminated on the upper surface 20A of the carbon fiber sheet 20 and on the lower surface 45BB of the second carbon nanotube sheet 45B laminated on the lower surface 20B of the carbon fiber sheet 20, respectively. According to the above embodiment, the first resin sheet 35A, the first carbon nanotube sheet 45A, the carbon fiber sheet 20, the second carbon nanotube sheet 45B, and the second resin sheet 35B can be laminated with high precision. Furthermore, the configuration of the manufacturing equipment can be simplified, productivity can be improved, and production costs can be reduced.

[0043] In the manufacturing method of this embodiment, ultrasonic vibration is further applied to the laminate 50 during the impregnation step (step S200). According to the above embodiment, the first carbon nanotube sheet 45A and the second carbon nanotube sheet 45B are more thoroughly incorporated into the carbon fiber sheet 20, thereby increasing the strength of the composite material 10.

[0044] In the manufacturing method of this embodiment, in the impregnation step (step S200), the laminate 50 is pressed so as to sandwich it from one side and the other side in the lamination direction, and the first resin sheet 35A and the second resin sheet 35B are heated. According to the above embodiment, the first carbon nanotube sheet 45A and the second carbon nanotube sheet 45B can be wrapped around both sides of the carbon fiber sheet 20 in a balanced manner.

[0045] In the manufacturing method of this embodiment, the thickness of the first carbon nanotube sheet 45A is thinner than the thickness of the first resin sheet 35A, and the thickness of the second carbon nanotube sheet 45B is thinner than the thickness of the second resin sheet 35B. According to the above embodiment, the first carbon nanotube sheet 45A and the second carbon nanotube sheet 45B can be more reliably penetrated by the first resin sheet 35A and the second resin sheet 35B, respectively.

[0046] In the manufacturing method of this embodiment, the resin is a thermoplastic resin. According to the above embodiment, impregnation of the carbon fiber sheet 20 can be made easier. In addition, the strength of the composite material 10 can be increased.

[0047] Preferred embodiments of the present invention have been described above. However, the embodiments described above are merely illustrative, and the present invention can be implemented in various other forms.

[0048] In the above-described embodiment, in the laminate formation step (step S100), the first resin sheet 35A, the first carbon nanotube sheet 45A, the carbon fiber sheet 20, the second carbon nanotube sheet 45B, and the second resin sheet 35B were stacked vertically in this order to form the laminate 50. However, the laminate 50 may also be formed by stacking them horizontally. [Explanation of symbols]

[0049] 10 Composite materials 20 carbon fiber sheets 30 layers made of resin 35 Resin Sheet 35A First resin sheet 35B Second resin sheet 40 Layers containing carbon nanotubes 45 Carbon nanotube sheets 45A First carbon nanotube sheet 45B Second carbon nanotube sheet 50-layer structure

Claims

1. A method for manufacturing a composite material comprising a carbon fiber sheet, a resin, and carbon nanotubes, A laminate formation step of forming a laminate by stacking a first resin sheet, a first carbon nanotube sheet, the carbon fiber sheet, a second carbon nanotube sheet, and a second resin sheet in this order, An impregnation step in which the laminate is pressed in the lamination direction and the laminate is heated to cause the resin contained in the first resin sheet and the resin contained in the second resin sheet to flow and impregnate the carbon fiber sheet, A manufacturing method that includes this.

2. The aforementioned laminate formation step is, A first lamination step involves laminating the first carbon nanotube sheet and the second carbon nanotube sheet onto one surface and the other surface of the carbon fiber sheet, respectively. The manufacturing method according to claim 1, comprising a second lamination step of laminating a first resin sheet and a second resin sheet onto a first carbon nanotube sheet laminated on one side of the carbon fiber sheet and a second carbon nanotube sheet laminated on the other side of the carbon fiber sheet, respectively.

3. The manufacturing method according to claim 1 or 2, wherein ultrasonic vibration is further applied to the laminate in the impregnation step.

4. The manufacturing method according to claim 1 or 2, wherein in the impregnation step, the laminate is pressed so as to sandwich it from one side and the other side in the lamination direction, and the first resin sheet and the second resin sheet are heated.

5. The thickness of the first carbon nanotube sheet is thinner than the thickness of the first resin sheet. The manufacturing method according to claim 1 or 2, wherein the thickness of the second carbon nanotube sheet is thinner than the thickness of the second resin sheet.

6. The manufacturing method according to claim 1 or 2, wherein the resin is a thermoplastic resin.

7. A composite material comprising a carbon fiber sheet having one side and the other side, a resin, and carbon nanotubes, On one surface and the other surface of the carbon fiber sheet, the carbon nanotubes are intertwined and fixed by the resin, respectively. A composite material having a laminated structure consisting of five layers in which, in a cross-sectional view perpendicular to the carbon fiber sheet, at least a portion of the region is laminated in the order of the resin layer, the layer containing the carbon nanotubes, the layer containing the carbon fiber sheet, the layer containing the carbon nanotubes, and the resin layer.

8. The composite material according to claim 7, wherein, in the cross-sectional view, when the total cross-sectional area of ​​the composite material is taken as 100%, the laminated structure accounts for 1 / 3 or more of the total area.

9. The composite material according to claim 7 or 8, wherein the resin is a thermoplastic resin.

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