Joined body of metal and thermosetting carbon fiber reinforced plastic, and joining method

Abstract

To provide a joined body of metal and a carbon fiber reinforced plastic, excellent in joining strength of the joining section, heat resistance and chemical resistance, and having high mechanical strength.SOLUTION: A joined body 100 of metal and a thermosetting carbon fiber reinforced plastic, comprises a first member 10 made of metal, a second member 20 made of a thermosetting carbon fiber reinforced plastic, and an adhesive layer 30 made of an electrodeposition coating film formed on the surface of the first member 10, with the first member 10 and the second member 20 joined to each other via the adhesive layer 30.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a joined body of a metal and a thermosetting carbon fiber reinforced plastic and a joining method. [Background technology]

[0002] Carbon fiber reinforced plastic (CFRP), which uses carbon fiber as a reinforcing material in a base plastic, is an extremely light material with a specific gravity of about one-quarter that of steel, yet has strength and rigidity on a par with steel, making it increasingly applicable to a variety of products, including structural components for transportation equipment such as aircraft and automobiles. In recent years, the demand for decarbonization has led to demands for weight reduction in parts and components for various industrial products, exemplified by the shift to electric vehicles (EVs), and there is a growing need for multi-material combinations of CFRP and metal materials to achieve both weight reduction and structural strength in parts and components for various industrial products.

[0003] CFRP is divided into two types: carbon fiber reinforced plastic (thermoplastic CFRP), which uses a thermoplastic resin as the base plastic, and carbon fiber reinforced plastic (thermosetting CFRP), which uses a thermosetting resin as the base plastic. Of these, thermoplastic CFRP has the property of softening when heated and hardening when cooled, which allows for a high degree of freedom in molding and processing, and is relatively easy to bond with adhesives. Therefore, the use of thermoplastic CFRP is being considered exclusively for the composite and multi-material combination of CFRP and metal materials. Furthermore, thermoplastic CFRP and metal materials are typically joined by heating the area near the joint using a hot press, laser, friction, etc. to melt the thermoplastic CFRP and thermally fuse it. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 7162925 [Patent Document 2] Japanese Patent Application Publication No. 10-195349 [Non-patent literature]

[0005] [Non-Patent Document 1] Takao Saito: Color Materials, 72(3), 156(1999) Summary of the Invention [Problem to be solved by the invention]

[0006] However, in recent years, there has been an increasing demand for higher mechanical properties, such as greater heat resistance and rigidity, even for multi-material materials made of metal and CFRP. As the thermoplastic plastics used in thermoplastic CFRP are expected to be highly crystalline super engineering plastics such as PPS and PEAK, joining by thermal fusion as described above has become extremely difficult.

[0007] On the other hand, thermosetting CFRP uses prepregs in which carbon fibers are pre-impregnated with a coating material containing thermosetting resin. Because prepreg materials have high curing reactivity, their pot life is short and they require refrigeration or freezing for storage. This makes prepregs difficult to handle and work with. Due to these factors, there has been insufficient research to date into using thermosetting CFRP instead of thermoplastic CFRP to create multi-material structures with metal materials.

[0008] For example, Patent Document 1 discloses a configuration for producing thermosetting CFRP by directly applying and curing a thermosetting electrodeposition paint without going through a prepreg process, utilizing the conductivity of a thermosetting electrodeposition paint and a carbon fiber material, and also discloses the joining of thermosetting CFRP with a metal material. However, this method does not form an adhesive layer between the metal and the thermosetting CFRP, making it difficult to obtain sufficient and reliable adhesion, and therefore cannot be used as a multi-material technology. Note that, for example, Non-Patent Document 1 and Patent Document 2 disclose electrolytically activated electrodeposition paints as other thermosetting electrodeposition paints.

[0009] The present invention has been made in view of the above background, and aims to provide a joined body of metal and carbon fiber reinforced plastic that has excellent joining strength, heat resistance, and chemical resistance at the joint and high mechanical strength. [Means for solving the problem]

[0010] One aspect of the present invention is a first member made of metal; a second member made of thermosetting carbon fiber reinforced plastic; an adhesive layer formed on the surface of the first member and consisting of an electrodeposition coating film; The first member and the second member are joined together via the adhesive layer to form a joined body of metal and thermosetting carbon fiber reinforced plastic.

[0011] Another aspect of the present invention is A method for manufacturing a joined body of metal and carbon fiber reinforced plastic, comprising: an adhesive layer forming step in which a first member made of metal is immersed in an electrodeposition paint made of electrolytically activated epoxy resin dispersed in water, a voltage is applied using the first member as a cathode to precipitate the electrolytically activated epoxy resin on the surface of the first member, and the first member electrodeposited with the electrodeposition paint is heated at a temperature of 180°C or less to remove moisture, thereby forming an adhesive layer made of electrodeposition paint on the surface of the first member; a laminating step of laminating the prepreg for forming a thermosetting carbon fiber reinforced plastic on the first member so that the prepreg for forming a thermosetting carbon fiber reinforced plastic contacts the adhesive layer; a curing step of heating the first member and the prepreg for forming a thermosetting carbon fiber reinforced plastic, which are stacked together, at a temperature of 180°C or higher to cure the electrolytically activated epoxy resin; The present invention relates to a method for producing a joined body of metal and carbon fiber reinforced plastic, which includes the steps of: [Effects of the Invention]

[0012] In the above-described joined body of metal and thermosetting carbon fiber reinforced plastic, the adhesive layer has high bonding strength and adhesion to the metal due to electrodeposition coating, and also has high bonding strength and adhesion to the thermosetting carbon fiber reinforced plastic because it is a resin-to-resin bond. Furthermore, the epoxy resin constituting the adhesive layer has excellent heat resistance and chemical resistance. Therefore, by joining a first member made of metal and a second member made of thermosetting carbon fiber reinforced plastic via the adhesive layer, the joint has excellent bonding strength, heat resistance, and chemical resistance, and can form a joined body with a metal that has high mechanical strength.

[0013] As described above, according to the above-described one aspect, it is possible to provide a joined body of metal and carbon fiber reinforced plastic having excellent joining strength, heat resistance, and chemical resistance at the joint and high mechanical strength.

[0014] In the manufacturing method according to the other embodiment, the electrolytically activated epoxy resin forming the adhesive layer has electrodeposition latency with respect to the curing reaction of the coating. Electrodeposition latency refers to a property of the coating that the curing reaction is initially latent and requires an electrodeposition process to become active. In other words, to initiate the curing reaction of the coating, it is essential to apply a voltage in advance in the electrodeposition process to cause an electrochemical reaction; the curing reaction does not proceed simply by heating without applying a voltage. Furthermore, the curing reaction after the electrodeposition process proceeds slowly below the curing temperature of the epoxy resin, and proceeds almost negligibly at room temperature, even in the temperature range of 100 to 180°C.

[0015] Therefore, in the manufacturing method of the other aspect described above, by heating the first member electrodeposited in the adhesive layer formation step with a cationic electrodeposition paint made by dispersing an electrolytically activated epoxy resin in water at a temperature of 180°C or less, the moisture remaining in the first member is removed and an adhesive layer is formed, which makes it easy for the adhesive layer before bonding to maintain a semi-cured state at room temperature. This extends the usable time (pot life) and improves workability. Furthermore, by joining the first member made of metal and the second member made of thermosetting carbon fiber reinforced plastic via the adhesive layer, the joint can form a joined body with metal that has excellent bonding strength, heat resistance, and chemical resistance, and high mechanical strength. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 2A is a conceptual perspective view illustrating a step of joining a first member and a prepreg in the first embodiment, and FIG. 2B is a conceptual perspective view of a joined body of the first member and a second member. [Figure 2] FIG. 2A is a conceptual cross-sectional view illustrating a step of joining a first member and a prepreg, and FIG. 2B is a conceptual cross-sectional view of a joined body of the first member and a second member in the first embodiment. [Figure 3] 1 is a flow diagram showing a method for producing a bonded body of metal and thermosetting carbon fiber reinforced plastic in the first embodiment. [Figure 4] FIG. 3 is a conceptual diagram illustrating the adhesive layer forming step in the first embodiment. [Figure 5] FIG. 1 is a flow diagram showing a method for producing a prepreg for forming a thermosetting carbon fiber reinforced plastic in the first embodiment. [Figure 6] FIG. 2 is a conceptual diagram illustrating a confirmation test in the first embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0017] In the above-described embodiment of the bonded body of metal and thermosetting carbon fiber reinforced plastic, the electrodeposition coating film in the adhesive layer is preferably made of an electrolytically activated epoxy resin. In this case, by using an electrolytically activated epoxy resin for the adhesive layer, the first member to which a cationic electrodeposition paint made by dispersing the electrolytically activated epoxy resin in water has been electrodeposited is heated at a temperature of 180°C or less to remove the moisture remaining in the first member, thereby forming an adhesive layer. This makes it easy to maintain the adhesive layer in a semi-cured state at room temperature before bonding. This results in a long usable time (pot life) and improved workability.

[0018] In the above-described embodiment of the bonded body of metal and thermosetting carbon fiber reinforced plastic, the thermosetting carbon fiber reinforced plastic preferably comprises carbon fiber and an electrolytically activated epoxy resin. In this case, the cationic electrodeposition paint, which is a dispersion of the electrolytically activated epoxy resin in water, is heated at a temperature of 180°C or less to the carbon fiber material that has been electrodeposited in the electrodeposition step, thereby removing the moisture remaining in the carbon fiber material and forming an adhesive layer. This makes it easy for the thermosetting carbon fiber reinforced plastic that constitutes the second component to maintain a semi-cured state at room temperature. This results in a long usable time (pot life) and improved workability.

[0019] In the above-described embodiment of the bonded body of metal and thermosetting carbon fiber reinforced plastic, the electrolytically activated epoxy resin is preferably a novolac phenol polyepoxy resin, which makes it easier to maintain the thermosetting carbon fiber reinforced plastic constituting the adhesive layer and the second member in a semi-cured state at room temperature, thereby extending the pot life and improving workability.

[0020] In the method for producing a bonded body of a metal and a thermosetting carbon fiber reinforced plastic according to the other embodiment described above, the prepreg for forming a thermosetting carbon fiber reinforced plastic is preferably produced by a prepreg production method including a prepreg electrodeposition step in which a carbon fiber material formed by combining carbon fibers is immersed in an electrodeposition paint comprising an electrolytically activated epoxy resin dispersed in water, and a voltage is applied using the carbon fiber material as a cathode to deposit the electrolytically activated epoxy resin on the surface of the carbon fiber; and a prepreg heating and dehydration step in which the carbon fiber material electrodeposited with the cationic electrodeposition paint is heated at a temperature of 180°C or less to remove moisture. In this case, the curing reaction does not actively proceed in the prepreg at a heating temperature of 180°C or less, so the epoxy resin in the prepreg is in a semi-cured state, and the prepreg can be maintained in a semi-cured state at room temperature. Furthermore, since refrigeration or freezing is not required for storage, the usable time (pot life) is extended and workability is improved. Furthermore, because the prepreg is in a semi-cured state at room temperature, it can be easily molded to fit the first component to which the thermosetting CFRP is to be applied, even if the first component has a complex shape. As a result, takt time can be shortened and mass production is possible.

[0021] In the method for producing a joined body of metal and thermosetting carbon fiber reinforced plastic according to the other aspect described above, the heating temperature in the adhesive layer forming step is preferably 100° C. or higher and 180° C. or lower. In this case, the adhesive layer before joining can be maintained in a semi-cured state early, improving workability.

[0022] In the method for producing a bonded body of a metal and a thermosetting carbon fiber reinforced plastic according to the other aspect described above, in the overlapping step, it is preferable to overlap the prepreg for forming a thermosetting carbon fiber reinforced plastic onto the first member while heating at a temperature of not more than 180° C. In this case, when overlapping the first member and the prepreg for forming a thermosetting carbon fiber reinforced plastic, the adhesive layer can be maintained in a semi-cured state at room temperature, improving the workability and compatibility of the adhesive layer.

[0023] In the method for producing a joined body of metal and thermosetting carbon fiber reinforced plastic according to the other aspect described above, the heating temperature in the overlapping step is 100° C. or higher and 180° C. or lower. In this case, the adhesive layer before joining can be maintained in a semi-cured state early, improving workability.

[0024] In the method for producing a joined body of metal and thermosetting carbon fiber reinforced plastic according to the other aspect described above, the heating temperature in the curing step is 180° C. or higher and 300° C. or lower. In this case, the adhesive layer can be cured early after the laminating step is completed, which further shortens the takt time and further improves mass productivity.

[0025] (Embodiment 1) 1. Joints of metal and thermosetting carbon fiber reinforced plastic The following provides a detailed description of the joined body of metal and thermosetting carbon fiber reinforced plastic according to this embodiment 1. The joined body 100 of metal and thermosetting carbon fiber reinforced plastic according to this embodiment 1 (hereinafter also referred to as "joint body 100") includes a first member 10 made of metal and a second member 20 made of thermosetting carbon fiber reinforced plastic joined together via an adhesive layer 30 as shown in FIG.

[0026] 1-1. First member The metal constituting the first member 10 is not particularly limited, and various metals such as aluminum alloy, copper alloy, stainless steel alloy, and titanium alloy can be used. The shape of the first member 10 is also not limited, and can be a shape depending on the application of the joined body 100. In the present embodiment 1, the first member 10 is flat, as shown in Figs. 1 and 2 .

[0027] 1-2.Adhesive layer As shown in FIG. 2(a), the adhesive layer 30 is formed on the surface of the first member 10 and is composed of an electrodeposition coating. The electrodeposition coating constituting the adhesive layer 30 is formed by electrodeposition coating with a cationic electrodeposition coating in which an electrolytically activated epoxy resin is dispersed in water. Hereinafter, this cationic electrodeposition coating will also be referred to as an "electrolytically activated electrodeposition coating." An electrolytically activated epoxy resin is an epoxy resin that is electrolytically activated by an electrode reaction. More specifically, an electrolytically activated epoxy resin forms an epoxy resin coating by applying a voltage in the electrodeposition process, and the electrode reaction caused by the voltage application generates activated chemical species in the coating, which promote the progress of the curing reaction of the coating. The progress of the curing reaction after voltage application is slow below the curing temperature of the epoxy resin, and in particular, progresses almost nothing at room temperature, and is also slow in the temperature range of 100 to 180°C.

[0028] Such electrolytically activated epoxy resins are resin compositions containing sulfonium and propargyl groups in addition to the epoxy groups that constitute the epoxy resin. The resin composition of the electrolytically activated epoxy resin may, but does not necessarily, contain both sulfonium and propargyl groups in one molecule containing an epoxy group. For example, one molecule may contain only either a sulfonium or propargyl group. In this case, the resin composition as a whole contains these two types of functional groups. That is, the resin composition may consist of a resin containing both sulfonium and propargyl groups, a mixture of a resin containing only sulfonium groups and a resin containing only propargyl groups, or a mixture of all of these.

[0029] The epoxy resin that forms the backbone of the electrolytically activated epoxy resin is preferably one having at least two epoxy groups per molecule, and specific examples include epibis-type epoxy resins, those chain-extended with diols, dicarboxylic acids, diamines, etc.; epoxidized polybutadienes; novolac phenol-type polyepoxy resins; novolac cresol-type polyepoxy resins; polyglycidyl acrylate; polyglycidyl ethers of aliphatic polyols or polyether polyols; and polyglycidyl esters of polybasic carboxylic acids. Of these, novolac phenol-type polyepoxy resins, novolac cresol-type polyepoxy resins, and polyglycidyl acrylate are preferred because they can be easily multifunctionalized to enhance curability.

[0030] Examples of electrolytically activated electrodeposition paints containing such electrolytically activated epoxy resins include Insulead (registered trademark) 1000 and Insulead (registered trademark) 3000 manufactured by Nippon Paint Industrial Coatings Co., Ltd. Note that Insulead 1000 and Insulead 3000 contain phenolic resin (novolac resin) as a polymer compound, and can impart insulating properties and heat resistance by precipitating the epoxy resin. In this embodiment, Insulead 3000 is used as the electrolytically activated electrodeposition paint.

[0031] 1-3.Adhesive layer formation process As shown in FIG. 3, the adhesive layer forming step S10 for forming the adhesive layer 30 includes an electrodeposition step S1 and a heating and dehydration step S2.

[0032] 1-3-1.Electrodeposition process In the electrodeposition step S1 shown in Fig. 3, first, in step S11, the first member 10 is immersed in an electrolytically activated electrodeposition paint. In the first embodiment, as shown in Fig. 4, the first member 10 is immersed in an electrolytically activated electrodeposition paint 40 of a predetermined concentration stored in a reaction tank 50. This brings the electrolytically activated electrodeposition paint 40 into contact with the entire surface of the first member 10. An electrode 51 is also immersed in the reaction tank 50. The configuration of the electrode 51 is not limited, and it may be made of any conductive material, such as stainless steel, aluminum, or carbon.

[0033] Thereafter, in step S12, a voltage is applied to the first member 10. In the first embodiment, as shown in Fig. 4, the first member 10 and an electrode 51 in the reaction tank 50 are electrically connected via a power supply 52, and the output of the power supply 52 is controlled by a controller 53 to apply a voltage from the power supply 52 so that the first member 10 serves as the cathode. As a result, the epoxy resin present as a polymer compound colloid in the electrolytically activated electrodeposition paint 40 adheres to the surface of the first member 10 by electrophoresis, and is insolubilized and precipitated (electrodeposited) by an electrode reaction.

[0034] Since the cationic electrodeposition paint in which electrolytically activated epoxy resin is dispersed in water remains on the surface of the deposited epoxy resin, in step S13, this is washed away with deionized water to clean the epoxy resin surface.

[0035] The voltage and current applied to the carbon fiber material are not particularly limited and can be appropriately selected depending on the type of electrolytically activated electrodeposition paint. In particular, the applied voltage is preferably 90 to 500 V, more preferably 100 to 300 V, from the viewpoint of more sufficiently depositing the epoxy resin on each carbon fiber while further suppressing the electrolysis of water. The applied current depends on the size, thickness, etc. of the carbon fiber material, but is preferably 0.01 to 1.0 A, more preferably 0.05 to 0.5 A, from the viewpoint of more sufficiently depositing the epoxy resin on each carbon fiber while further suppressing the electrolysis of water.

[0036] The voltage application time is not particularly limited and can be appropriately selected depending on the type of electrolytically activated electrodeposition coating material. In particular, from the viewpoint of more sufficiently depositing the epoxy resin on each carbon fiber while further suppressing the electrolysis of water, the voltage application time is preferably 1 to 300 minutes, more preferably 5 to 120 minutes.

[0037] 1-3-2. Heating dehydration process In the thermal dehydration step S2 shown in FIG. 2, the first member 10 after the electrodeposition step S1 is heated at a temperature of 180°C or less. This removes moisture derived from the electrolytically activated electrodeposition paint adhering to the first member 10. The heating temperature in the thermal dehydration step S2 is 180°C or less, and more preferably in the range of 100 to 180°C. By setting the heating temperature in the range of 100 to 180°C, moisture can be removed quickly while suppressing curing of the adhesive layer 30 in the first member 10 after the electrodeposition step S1. The heating time in the thermal dehydration step S2 is not limited as long as it is a time that allows moisture to be sufficiently removed. Once the moisture has been sufficiently removed, the adhesive layer 30 is completed.

[0038] In the thermal dehydration step S2, as described above, the heating temperature is 180°C or less, so the curing of the electrolytically activated epoxy resin does not actively proceed, and the completed adhesive layer 30 is in a semi-cured state. As described above, the curing reaction of the electrolytically activated epoxy resin after the electrodeposition step S1 hardly progresses at room temperature, so the adhesive layer 30 can be stored in a semi-cured state at room temperature.

[0039] 1-4. Second member made of thermosetting carbon fiber reinforced plastic The thermosetting carbon fiber reinforced plastic that constitutes the second member 20 is made of a carbon fiber material and a thermosetting resin. The thermosetting carbon fiber reinforced plastic can be formed from a prepreg for forming thermosetting carbon fiber reinforced plastic. A prepreg for forming thermosetting carbon fiber reinforced plastic (hereinafter simply referred to as "prepreg" in this specification) is a composite of carbon fiber and thermosetting resin for forming thermosetting carbon fiber reinforced plastic, in which the carbon fiber material is pre-impregnated with the thermosetting resin.

[0040] 1-4-1. Carbon fiber materials Carbon fiber materials are formed by combining carbon fibers in a bundle or woven form. The structure of the carbon fiber material is not limited, and examples include a planar carbon fiber sheet and a bundle of carbon fibers. The carbon fiber sheet can be one in which multiple carbon fibers are woven in perpendicular directions. The weaving pattern is not limited, and known weaves such as plain weave and twill weave can be used. In addition, carbon fiber sheets can be used in which the carbon fibers are arranged not only linearly but also curvedly. The average fiber diameter of each carbon fiber is preferably within a range of 0.001 to 50 μm, from the viewpoint of sufficient precipitation of the epoxy resin described below. In this embodiment, a plain weave carbon fiber sheet is used as the carbon fiber material. The longitudinal and lateral dimensions of the carbon fiber sheet are not limited, and the thickness of the carbon fiber sheet is also not limited.

[0041] 1-4-2. Electrodeposition paint on the second component The electrocoating paint used to form the thermosetting carbon fiber reinforced plastic in the second member 20 is an electrolytically activated epoxy resin dispersed in water, and can be similar to the electrocoating paint in the adhesive layer 30 described above. In this embodiment, Insulead 3000 is used as the electrolytically activated electrocoating paint in the second member 20.

[0042] 1-5. Manufacturing method of prepreg for thermosetting carbon fiber reinforced plastics The method for manufacturing the prepreg for forming the thermosetting carbon fiber reinforced plastic that constitutes the second member 20 includes a prepreg electrodeposition step S1a and a prepreg heating and dehydration step S2a, as shown in Fig. 5. The prepreg electrodeposition step S1a and the prepreg heating and dehydration step S2a are the same as those in the electrodeposition step S1 and the heating and dehydration step S2 of the adhesive layer formation step S10 shown in Fig. 3, except that the first member 10 is replaced with a carbon fiber sheet, and detailed explanations thereof will be omitted.

[0043] In this embodiment 1, the prepreg bonding step 3a is performed after the prepreg heating and dehydration step S2a. In the prepreg bonding step 3a, a plurality of prepregs 20a for forming thermosetting carbon fiber reinforced plastics (hereinafter referred to as "prepregs 20a") formed in the prepreg heating and dehydration step S2a are laminated and heated at a temperature of 180°C or less and rolled to be bonded to each other. The number of prepregs 20a to be laminated is not limited and can be any desired number.

[0044] 2. Manufacturing method for joining metal and thermosetting carbon fiber reinforced plastic Next, a detailed description will be given of a method for manufacturing the joined body 100 of metal and thermosetting carbon fiber reinforced plastic according to the present embodiment 1. As shown in Fig. 3, the method for manufacturing the joined body 100 includes the above-mentioned adhesive layer forming step S10, the laminating step S20, and the curing step S30.

[0045] 2-1. Layering process The overlapping step S20 shown in Fig. 3 is performed after the adhesive layer forming step S10. In the overlapping step S20, as shown in Fig. 2(b), the prepreg 20a for forming a thermosetting carbon fiber reinforced plastic is overlapped on the first member 10 so that the prepreg 20a for forming a thermosetting carbon fiber reinforced plastic contacts the adhesive layer 30. In the overlapping step S20, rolling may be performed after overlapping.

[0046] In the overlapping step S20, the first member 10 and the prepreg 20a for forming a thermosetting carbon fiber reinforced plastic may be overlapped while being heated at a temperature of 180° C. or less. The heating temperature in the overlapping step S20 may be 100° C. or more and 180° C. or less.

[0047] 2-2.Curing process After the overlapping step S20, a curing step S30 shown in Fig. 3 is performed. In the curing step S30, the overlapping first member 10 and the prepreg 20a for forming a thermosetting carbon fiber reinforced plastic are heated at a temperature of 180°C or higher to cure the electrolytically activated epoxy resin in the adhesive layer 30 and the prepreg 20a. The heating temperature in the curing step S30 can be set to 180°C or higher and 300°C or lower. This bonds the first member 10 and the second member 20 via the adhesive layer 30. A bonded body 100 of metal and thermosetting carbon fiber reinforced plastic can be produced.

[0048] 3. Confirmation test Next, a test to confirm the adhesive strength of the bonded body 100 of metal and thermosetting carbon fiber reinforced plastic according to the first embodiment was conducted as follows. First, as described above, a prepreg 20a was produced according to the prepreg electrodeposition step S1a and the prepreg heating and dehydration step S2a shown in FIG. 5. Then, five prepreg sheets 20a cut into 25 mm × 100 mm pieces in the prepreg joining step 3a were stacked and pressed together under a load of approximately 10 kg. The laminated prepreg 20b was then dried at 105°C for 10 minutes to remove moisture, producing an uncured laminated prepreg 20b shown in FIG. 6(a). The thickness of the laminated prepreg 20b was 1.0 mm.

[0049] Next, metal plates (1.0 mm thick each) made of aluminum, copper, and SUS were prepared as the first members 10 and cut to 25 mm x 100 mm. Each first member 10 was subjected to electrodeposition coating in a region extending 25 mm from its tip according to the electrodeposition step S1 and thermal dehydration step S2 shown in FIG. 3, thereby forming an adhesive layer 30 as shown in FIG. 6(a). Each metal plate constituting the first member 10 utilizes the surface of a cold-rolled material as is, and the surface of the first member 10 is a smooth flat surface with a surface roughness of Ra 1.0 or less. The area where the adhesive layer 30 is formed measures 25 mm x 25 mm.

[0050] 3, the laminated prepreg 20b was laminated on the first member 10 as shown in FIG. 6(b), and then the laminated prepreg 20b was baked at a temperature of 170° C. to 180° C. for 20 minutes or longer as shown in FIG. 3, in accordance with the curing step S30. This produced a bonded body 100 of the first member 10 and the laminated prepreg 20b.

[0051] Each of the bonded bodies 100 prepared as described above was subjected to a tensile tester to check the shear stress at the bonded portion of each bonded body 100. The shear stress at the bonded portion between the aluminum first member 10 and the laminated prepreg 20b was 4.6 MPa, the shear stress at the bonded portion between the copper first member 10 and the laminated prepreg 20b was 4.8 MPa, and the shear stress at the bonded portion between the SUS first member 10 and the laminated prepreg 20b was 4.4 MPa. This confirmed that a sufficiently high bond strength was obtained in all cases.

[0052] 4. Effects The effects of the bonded body of metal and thermosetting carbon fiber reinforced plastic according to the first embodiment will be described below. In the joined body 100 of metal and thermosetting carbon fiber reinforced plastic of this embodiment 1, the adhesive layer 30 has high bond strength and adhesion to the metal due to the electrodeposition coating, and also has high bond strength and adhesion to the thermosetting carbon fiber reinforced plastic because it is a resin-to-resin bond. Furthermore, the epoxy resin that constitutes the adhesive layer 30 has excellent heat resistance and chemical resistance. Therefore, by joining the first member 10 made of metal and the second member 20 made of thermosetting carbon fiber reinforced plastic via the adhesive layer 30, the joint has excellent bond strength, heat resistance, and chemical resistance, and a joined body 100 with metal that has high mechanical strength can be formed.

[0053] Furthermore, in this embodiment 1, the electrodeposition coating film in the adhesive layer 30 is made of an electrolytically activated epoxy resin. By using an electrolytically activated cationic epoxy electrodeposition paint for the adhesive layer 30, the first member 10, which has been electrodeposited with a cationic electrodeposition paint made by dispersing an electrolytically activated epoxy resin in water, is heated at a temperature of 180°C or less to remove the moisture remaining in the first member 10 and form the adhesive layer 30, which makes it easy to maintain the adhesive layer 30 in a semi-cured state at room temperature before bonding. This results in a long usable time (pot life) and improved workability.

[0054] In addition, in this embodiment 1, the thermosetting carbon fiber reinforced plastic is composed of carbon fiber and an electrolytically activated epoxy resin. By heating the carbon fiber material electrodeposited with a cationic electrodeposition paint made by dispersing the electrolytically activated epoxy resin in water at a temperature of 180°C or less, the moisture remaining in the carbon fiber material is removed and an adhesive layer is formed, which makes it easy for the thermosetting carbon fiber reinforced plastic constituting the second member to maintain a semi-cured state at room temperature. This results in a long usable time (pot life) and improved workability.

[0055] In addition, in this embodiment 1, the electrolytically activated epoxy resin is a novolac phenol polyepoxy resin, which makes it easy to maintain the thermosetting carbon fiber reinforced plastic that constitutes the adhesive layer 30 and the second member 20 in a semi-cured state at room temperature, thereby extending the usable time (pot life) and improving workability.

[0056] Furthermore, in the manufacturing method of a bonded body of metal and thermosetting carbon fiber reinforced plastic according to the first embodiment, the first member 10, which has been electrodeposited in the adhesive layer forming step with a cationic electrodeposition paint made by dispersing an electrolytically activated epoxy resin in water, is heated at a temperature of 180°C or less to remove moisture remaining in the first member 10 and form the adhesive layer 30, which makes it easy to maintain the adhesive layer 30 in a semi-cured state at room temperature before bonding. This results in a long usable time (pot life) and improved workability. Furthermore, bonding the first member 10 made of metal and the second member 20 made of thermosetting carbon fiber reinforced plastic via the adhesive layer 30 provides excellent bonding strength, heat resistance, and chemical resistance.

[0057] In this first embodiment, the prepreg 20a for forming a thermosetting carbon fiber reinforced plastic is produced by a prepreg manufacturing method including a prepreg electrodeposition step S1a in which a carbon fiber material formed by combining carbon fibers is immersed in a cationic electrodeposition paint in which an electrolytically activated epoxy resin is dispersed in water, and a voltage is applied using the carbon fiber material as a cathode to precipitate the electrolytically activated epoxy resin on the surface of the carbon fiber; and a prepreg heating and dehydration step S2a in which the carbon fiber material electrodeposited with the cationic electrodeposition paint is heated at a temperature of 180°C or less to remove moisture. As a result, the curing reaction does not actively proceed in the prepreg 20a at heating temperatures of 180°C or less, so the epoxy resin in the prepreg 20a becomes semi-cured, and the prepreg 20a can be maintained in a semi-cured state at room temperature. Furthermore, since refrigeration or freezing is not required for storage, the usable time (pot life) is extended and workability is improved. Furthermore, since the prepreg 20a is in a semi-cured state at room temperature, it can be easily molded to fit the first member 10, even if the first member 10 to which the thermosetting CFRP is to be applied has a complex shape. As a result, the takt time can be shortened, and mass productivity is high.

[0058] In the first embodiment, the heating temperature in the adhesive layer forming step S10 is 100° C. or higher and 180° C. or lower. This allows the adhesive layer 30 to be maintained in a semi-cured state early before bonding, improving workability.

[0059] Furthermore, in the first embodiment, in the overlapping step S20, the prepreg 20a for forming a thermosetting carbon fiber reinforced plastic is overlapped onto the first member 10 while being heated at a temperature of 180° C. or less. This allows the adhesive layer 30 to be maintained in a semi-cured state at room temperature when the first member 10 and the prepreg 20a for forming a thermosetting carbon fiber reinforced plastic are overlapped, improving workability.

[0060] In the first embodiment, the heating temperature in the overlapping step S20 is 100° C. or higher and 180° C. or lower, which allows the adhesive layer 30 to be maintained in a semi-cured state early before bonding, improving workability.

[0061] In addition, in the present embodiment 1, the heating temperature in the curing step S30 is 180° C. or higher and 300° C. or lower. This allows the adhesive layer 30 to be cured early after the completion of the overlapping step S20, further shortening the takt time and further improving mass productivity.

[0062] As described above, according to the first embodiment, it is possible to provide a joined body 100 of metal and carbon fiber reinforced plastic having excellent joining strength, heat resistance, and chemical resistance at the joint and high mechanical strength. [Explanation of symbols]

[0063] 10 First member 20 Second member 20a Thermosetting carbon fiber reinforced plastic molding prepreg 30 Adhesive layer 40 Electrolytically activated electrodeposition paint (cationic electrodeposition paint) 50 reactors 51 electrode 52 Power supply 53 Controller 100 zygote

Claims

1. a first member made of metal; a second member made of thermosetting carbon fiber reinforced plastic; an adhesive layer formed on the surface of the first member and consisting of an electrodeposition coating film; A bonded body of metal and thermosetting carbon fiber reinforced plastic, in which the first member and the second member are bonded to each other via the adhesive layer.

2. 2. The joined body of metal and thermosetting carbon fiber reinforced plastic according to claim 1, wherein the electrodeposition coating film in the adhesive layer is made of an electrolytically activated epoxy resin.

3. 3. A joined body of metal and thermosetting carbon fiber reinforced plastic according to claim 2, wherein the thermosetting carbon fiber reinforced plastic comprises carbon fiber and an electrolytically activated epoxy resin.

4. 4. A joined body of metal and thermosetting carbon fiber reinforced plastic according to claim 2 or 3, wherein the electrolytically activated epoxy resin is a novolac phenol polyepoxy resin.

5. A method for manufacturing a joined body of metal and thermosetting carbon fiber reinforced plastic, comprising the steps of: an adhesive layer forming step in which a first member made of metal is immersed in a cationic electrodeposition paint in which an electrolytically activated epoxy resin is dispersed in water, a voltage is applied using the first member as a cathode to precipitate the electrolytically activated epoxy resin on the surface of the first member, and the first member electrodeposited with the cationic electrodeposition paint is heated at a temperature of 180°C or less to remove moisture, thereby forming an adhesive layer made of the electrodeposition paint on the surface of the first member; a laminating step of laminating the prepreg for forming a thermosetting carbon fiber reinforced plastic on the first member so that the prepreg for forming a thermosetting carbon fiber reinforced plastic contacts the adhesive layer; a curing step of heating the first member and the prepreg for forming a thermosetting carbon fiber reinforced plastic, which are stacked together, at a temperature of 180°C or higher to cure the electrolytically activated epoxy resin; A method for producing a bonded body of a metal and a thermosetting carbon fiber reinforced plastic, comprising:

6. The prepreg for forming the thermosetting carbon fiber reinforced plastic includes a prepreg electrodeposition process in which a carbon fiber material formed by combining carbon fibers is immersed in a cationic electrodeposition paint in which an electrolytically activated epoxy resin is dispersed in water, and a voltage is applied using the carbon fiber material as a cathode to deposit the electrolytically activated epoxy resin on the surface of the carbon fiber; and a prepreg heating and dehydration step of heating the carbon fiber material electrodeposited with the cationic electrodeposition paint at a temperature of 180°C or less to remove moisture.

7. 7. The method for producing a joined body of metal and thermosetting carbon fiber reinforced plastic according to claim 5, wherein the heating temperature in the adhesive layer forming step is 100°C or higher and 180°C or lower.

8. 7. The method for producing a joined body of metal and thermosetting carbon fiber reinforced plastic according to claim 5 or 6, wherein in the overlapping step, the prepreg for forming thermosetting carbon fiber reinforced plastic is overlapped on the first member while being heated at a temperature of 180°C or less.

9. 9. The method for producing a joined body of metal and thermosetting carbon fiber reinforced plastic according to claim 8, wherein the heating temperature in the overlapping step is 100°C or higher and 180°C or lower.

10. 7. The method for producing a joined body of metal and thermosetting carbon fiber reinforced plastic according to claim 5 or 6, wherein the heating temperature in the curing step is 180°C or higher and 300°C or lower.

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