JP2011073191A - Joined body of cfrp and adherend and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a joined body of a CFRP prepreg and a metallic alloy firmly affixed to each other. <P>SOLUTION: A first CFRP prepreg based on a first PAN carbon fiber with a tensile strength of 4.4 GPa and a second CFRP prepreg based on a second PAN carbon fiber with a tensile strength of 6.0 GPa are stacked and heated to form a CFRP member. The first CFRP prepreg forming the surface of the CFRP member is roughened and a one-pack type epoxy adhesive is applied. A one-pack type epoxy adhesive is applied to the surface of a metallic alloy 11 having three conditions for NAT. The first CFRP prepreg 12 and the metallic alloy are brought close together and heated and the one-pack type epoxy adhesive is cured to obtain a joined body of the CFRP member and the metallic alloy firmly affixed to each other. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a bonded body of a carbon fiber reinforced plastic (hereinafter referred to as “CFRP (abbreviation of Carbon Fiber Reinforced Plastics)”) and an adherend used in the entire manufacturing field of transportation equipment, electrical equipment, medical equipment, and the like. In particular, the present invention relates to a bonded body in which CFRP and an adherend (CFRP or metal alloy) are bonded together by a co-curing (hereinafter referred to as “co-cure”) method. The present invention also relates to a joined body in which CFRP and an adherend (CFRP or metal alloy) are bonded by a cobond method using an epoxy adhesive.

  The inventors of the present invention have developed a technique for firmly bonding metal alloys to each other or a metal alloy and CFRP with an epoxy adhesive. Patent Document 1 discloses a technique for firmly bonding aluminum alloys or between an aluminum alloy and CFRP using a one-component epoxy adhesive. Similarly, in Patent Documents 2, 3, 4, 5, and 6, magnesium alloy, copper alloy, titanium alloy, stainless steel, and general steel material are respectively used as a metal alloy or a CFRP member and a one-component epoxy adhesive. Thus, a technique for firmly bonding is disclosed.

  Here, in the said technique, the adhesive force was acquired by the anchor effect by making the metal alloy surface into a predetermined shape and structure. The inventors refer to this theory as “NAT (Nano Adhesion Technology)”. In NAT, the metal alloy surface satisfies the following three conditions to achieve strong adhesion to the adherend.

(1) The first condition is that when the metal alloy surface is scanned with the latest dynamic mode scanning probe microscope, RSm is 0.8 to 10 μm and Rz is 0.2 to 5 μm. It is a measure. Here, RSm is the average length of contour curve elements defined in Japanese Industrial Standard (JIS B 0601: 2001, ISO 4287: 1997), and Rz is Japanese Industrial Standard (JIS B 0601: 2001, ISO 4287: 1997). This roughness surface is referred to as a “surface having a roughness on the order of microns”.
(2) The second condition is that ultrafine irregularities having a period of 5 nm or more are further formed on the surface of the metal alloy having a roughness on the order of microns. In order to satisfy the conditions, fine etching is performed on the surface of the metal alloy, and the inner wall surface of the concave portion having a roughness on the order of micron is 5 to 500 nm, preferably 10 to 300 nm, more preferably 30 to 100 nm (optimum value). Form ultra-fine irregularities with a period of 50 to 70 nm.
(3) The third condition is that the surface layer of the metal alloy is ceramic. Specifically, with respect to the metal alloy type that originally has corrosion resistance, the surface layer needs to be a metal oxide layer having a thickness equal to or greater than that of the natural oxide layer, and the metal alloy type having relatively low corrosion resistance ( For example, in the case of a magnesium alloy or a general steel material, the third condition is that the surface layer is a thin layer of metal oxide or metal phosphorous oxide generated by chemical conversion treatment or the like.

  These are schematically illustrated as shown in FIG. Concave portions (C) having a roughness on the order of microns are formed on the surface of the metal alloy 40, and ultra fine irregularities (A) are formed on the inner walls of the concave portions, and the surface layer is a ceramic layer 41. In addition, a part of the cured adhesive layer 42 penetrates into the ultra-fine irregularities. It is a simple idea that when a liquid adhesive enters the surface of the metal alloy thus formed and hardens after the penetration, the metal alloy and the hardened adhesive are bonded very firmly.

  The procedure of adhesive bonding is shown below. First, the surface of the metal alloy is etched to satisfy the above three conditions. Then, apply a liquid one-component epoxy adhesive to a predetermined range of the metal alloy, put it in a desiccator, place it under vacuum, and then return it to normal pressure. Invade. That is, the adhesive is sufficiently infiltrated into the metal alloy surface. Thereafter, the adherend is bonded to the predetermined range and heated to cure the adhesive.

  In such a case, if the epoxy adhesive is liquid, the viscosity can be lowered with a slight increase in temperature even if the viscosity at room temperature is high. Therefore, the concave portion (roughness of the irregularities in the first condition) on the surface of the metal alloy is reduced. It is possible to enter the recess). And the epoxy adhesive which penetrate | invaded hardens | cures in this recessed part by subsequent heating. Actually, an ultrafine unevenness is further formed on the inner wall surface of the recess (the second condition), and the ultrafine unevenness is a thin ceramic-like thin film (the third condition). Since it is covered, the epoxy resin that has entered the inside of the recess and solidified is difficult to come out by being gripped by ultra-fine irregularities such as spikes.

  The present inventors have demonstrated that “NAT” enables high-strength adhesion between metal alloys or between a metal alloy and CFRP. As an example, as a result of adhering together A7075 aluminum alloys having the conditions of “NAT” using a commercially available one-component epoxy adhesive, a bonded body exhibiting an intense shear breaking force and tensile breaking force as high as 70 MPa is obtained. (Patent Document 1).

WO 2008/114669 A1 (aluminum alloy) WO 2008/133096 A1 (magnesium alloy) WO 2008/126812 A1 (copper alloy) WO 2008/133030 A1 (titanium alloy) WO 2008/133296 A1 (stainless steel) WO 2008/146833 A1 (general steel)

ThreeBond Technical News 19 (issued October 1, 1987, ThreeBond Co., Ltd.)

  As described above, the present inventors used a commercially available one-part epoxy adhesive, and based on “NAT”, conducted an experiment to bond and bond metal alloys to each other or a metal alloy and CFRP. Regarding the bonding of CFRP, the shear breaking force and the tensile breaking force tended to be lower than when metal alloys were bonded to each other. Strong adhesion between a metal alloy and CFRP is expected in various fields such as aircraft and ships. However, when a metal alloy and CFRP are bonded with a one-component epoxy adhesive, an adhesive force equivalent to that of metal alloys cannot be stably obtained. Specifically, the composite in which the metal alloy and CFRP are bonded has a large variation between the composites in the shear breaking force and the tensile breaking force, and the breaking force itself is clearly reduced. The present inventors performed the same adhesion experiment by improving the one-component epoxy adhesive. As a result, it was confirmed that although it contributed to the improvement in the adhesion between metal alloys meeting the NAT conditions, it did not contribute to the improvement in the adhesion between the metal alloy and CFRP.

  As a result of investigating factors that cause the adhesive strength between CFRP and metal alloy to be inferior to the adhesive strength between metal alloys, the present inventors have found the following facts. In short, it has been found that the cause of the fracture of the composite of CFRP and metal alloy is the adhesive force between the carbon fiber in CFRP and the matrix resin. When the composite of CFRP and metal alloy was pulled and broken, the fracture surface of the metal alloy was enlarged and observed, and a lot of carbon fibers were attached to all of the fracture surface. That is, the adhesive force between the cured matrix resin and the cured adhesive on the cured CFRP prepreg surface layer exceeded the adhesive force between the cured matrix resin and the carbon fiber inside the cured CFRP prepreg. Thereby, at the time of a fracture | rupture, peeling occurred previously between the hardened matrix resin and carbon fiber, and this appeared as a low adhesive force. In other words, the adhesive strength between the surface of the metal alloy and the cured adhesive and between the cured adhesive and the cured matrix resin is extremely high, and the cured adhesive itself is extremely strong. The factor that determines the adhesive strength of CFRP is the adhesive strength between the carbon fiber and the matrix resin.

  From this, it is estimated that the improvement in the adhesion between the carbon fiber and the matrix resin directly contributes to the improvement in the adhesion between the metal alloy and CFRP. The present invention has been made based on such a background. The purpose of the present invention is to use CFRP with improved adhesion between carbon fibers and a matrix resin so that the CFRP and the adherend (CFRP) are used. Another object is to provide a bonded body in which a metal alloy) is firmly bonded.

  Although CFRP is super lightweight, it has toughness exceeding steel and is recognized as an extremely excellent structural material. Although it was expensive, it was initially used only as a tail material for fighters, but in recent years it has also been used for civilian products such as aircraft, golf clubs, tennis rackets, and fishing rods, and is recognized as a general structural material. It is being done. Under such circumstances, techniques relating to carbon fiber of CFRP prepreg, carbon fiber surface treatment method, matrix resin and the like have been established. However, as described above, as a result of the development of the “NAT” by the present inventors, it becomes possible to firmly bond the metal alloy and the one-part epoxy adhesive, and the one-part epoxy adhesive and the CFRP. The adhesion between carbon fiber and matrix resin in CFRP became a problem.

  As a method for improving the adhesion between the carbon fiber and the matrix resin, (1) selection of an optimal carbon fiber (focus on surface properties, not fiber strength), (2) improvement of the surface treatment method of the carbon fiber, and (3) The matrix resin can be improved. In the present invention, (1) is particularly focused. In recent years, various CFRP prepregs are commercially available from carbon fiber manufacturers. The catalog describes the type of carbon fiber yarn used (PAN (Poly-acrylonitrile) or PITCH), its tensile strength and tensile modulus.

  Among the PAN-based carbon fibers, those having the highest tensile strength of about 6 GPa have a cross section close to a perfect circle and a smooth fiber surface. On the other hand, among the PAN-based carbon fibers, those having a tensile strength of 3 GPa or less have a cross section close to an ellipse or rhombus, and a groove having a height difference (several tens of nm) is formed on the fiber surface. ing. In general, the CFRP prepreg based on the former is treated as a first-class product, and the CFRP prepreg based on the latter is treated as a second-class product. However, only high-performance carbon fibers having a tensile strength of 4 to 6 GPa have been produced recently, and it is difficult to obtain carbon fibers having a tensile strength of about 3 GPa.

  As described above, the use and price of the CFRP prepreg are generally determined by the carbon fiber, whereas the composition of the matrix resin is usually the same. That is, unlike carbon fiber, there is no difference in superiority or inferiority in matrix resin other than by use. Accordingly, it is considered that the use of a CFRP prepreg having a high tensile strength and a smooth fiber surface (a high-performance CFRP prepreg) usually produces strong adhesion to the adherend. On the other hand, however, the present inventors have estimated that CFRP prepregs based on those classified as lower in carbon fiber are more suitable in terms of adhesion between CFRP prepregs and adherends. . That is, although the tensile strength was low, it was regarded as an advantage that the surface area was large because the fiber surface was not smooth. As a result of conducting an adhesion experiment between CFRP and an adherend (CFRP or metal alloy) to prove this estimation, it was confirmed that the above estimation was correct.

The inventors observed the surface of carbon fiber “T800SC (manufactured by Toray Industries, Inc.)” having a tensile strength of 6 GPa and carbon fiber “TR30S (manufactured by Mitsubishi Rayon)” having a tensile strength of 4.4 GPa with an electron microscope. As a result, as shown in FIG. 16 and FIG. 17, “T800SC” had a cross section close to a perfect circle and a groove was observed on the surface, but the height difference of the groove was almost 50 nm or less and was smooth. On the other hand, as shown in FIG. 13 to FIG. 15, “TR30S” had many grooves with a height difference of 50 to 100 nm, although the cross section was almost a perfect circle. Generally, at least one groove having a height difference of 50 nm or more was present within a length of about 20 μm in the carbon fiber direction (surface area of 5 × 10 ⁻⁴ mm ² ). That is, “TS30S” having a tensile strength of 4.4 GPa has a good surface property compared to 3 GPa in the tensile strength, but clearly has a poor surface property compared to carbon fiber having a tensile strength of 6 GPa. .

  As described above, due to the difference in tensile strength, carbon fibers having a tensile strength of 6 GPa are treated as first-class products and those having a tensile strength of less than 6 GPa are treated as second-class products. In the experiment described below, a CFRP prepreg based on each carbon fiber was used to conduct an adhesion test, and the CFRP prepreg based on the carbon fiber classified as the second grade has a higher adhesive strength than the first grade. Confirmed that you can win. As the bonding method at this time, both the co-curing method and the co-bonding method were used. In either case, the effect of selecting the lower carbon fiber could be confirmed.

Hereafter, each element which comprises this invention is demonstrated in detail.
[CFRP prepreg]
A commercially available CFRP prepreg uses a thermosetting epoxy resin composition that is solid at room temperature as a matrix resin, and the CFRP prepreg is a solid sheet. Regarding the commercially available CFRP prepreg, since the specific composition of the matrix resin is not disclosed, the details are unknown, but the composition is generally as follows. The epoxy resin used as the matrix resin is a monomer type of bisphenol A type epoxy resin as a main component, and a multimeric type of bisphenol A type epoxy resin and a polyfunctional type epoxy resin having three or more epoxy groups. It is a mixture of about 3 to 5 types of different epoxy resins. An aromatic diamine or dicyandiamide is added to this mixture as a curing agent, and the mixture is kneaded while heating to form a matrix resin.

  When the curing agent is an aromatic diamine, the Tg (glass transition point) of the cured epoxy resin can be increased to 150 to 180 ° C., and the heat resistance of CFRP can be ensured. When aromatic diamine is used as the curing agent, the amount added is optimally based on the epoxy equivalent, and is usually 25 to 35 parts by mass with respect to 100 parts by mass of the epoxy resin. The most commonly used aromatic diamine as a curing agent is diaminodiphenyl sulfone (referred to as “DDS”), which is a solid. The epoxy resin mixture is a high-viscosity liquid, and the curing agent mixed therewith is a solid, and the amount of addition is large as described above. Therefore, mixing operation with a hardening | curing agent will be performed in the state which heated the epoxy resin mixture to 60-80 degreeC. Specifically, both are kneaded by a heating roll to form a sheet-like matrix resin. That is, the kneaded product becomes solid at room temperature. A CFRP prepreg is formed by sandwiching a carbon fiber bundle or a carbon fiber cloth between the two matrix resins formed into a sheet and heating it again to form a single layer by heating. The CFRP prepreg thus obtained is a hard and thin sheet-like material as a whole, and since the matrix resin is solid, there is no need for a cover film in principle, and an automatically controlled cutter can be used when cutting this. .

  On the other hand, when the curing agent is dicyandiamide, the Tg of the cured epoxy resin varies depending on the epoxy resin composition (Non-Patent Document 1). This Non-Patent Document 1 states that “the polymerization between epoxy resins is different between the case where an aliphatic polyamine or an aromatic diamine is used as a curing agent and the case where dicyandiamide is used as a curing agent. There is also catalytic polymerization. " As a basis for this, when dicyandiamide powder is used as a curing agent, the optimum addition amount is far less than the value based on the epoxy equivalent, and is 3 to 6 parts by mass with respect to 100 parts by mass of the epoxy resin. Therefore, when dicyandiamide is used as the curing agent, the matrix resin is only slightly increased in viscosity compared to the epoxy resin mixture before the addition of the curing agent, and is usually not a solid at room temperature but a high viscosity liquid.

  As described above, carbon fibers include PAN and PITCH. When the PAN-based carbon fiber and the PITCH-based carbon fiber are compared, there is a feature that the former is excellent in tensile strength while the latter is excellent in tensile elastic modulus. The surface properties of these carbon fibers will be described. Regarding the PAN-based carbon fiber, the fiber having a higher tensile strength has a fiber cross section closer to a perfect circle and a smooth fiber surface. Even with an electron microscope, a uniform surface is observed. It is known that carbon fibers having a low tensile strength have a fiber cross section that is not a perfect circle but is mostly an ellipse or rhombus, and grooves are formed in parallel to the fiber direction. In short, the carbon fiber with lower tensile strength has a lower surface property.

  On the other hand, the quality of the PITCH-based carbon fiber is determined by the tensile elastic modulus. In the PITCH-based carbon fiber, a high graphitization rate and a method of arranging graphite crystals parallel to the fiber direction cause high tensile elastic modulus. The manufacturing method is as follows. The highly purified PITCH is melted at a high temperature of several hundred degrees and spun through a small hole. The obtained fiber is melted again at a high temperature, so that it is infusible by oxidation or the like, and the infusible fiber is placed in an inert gas at a high temperature exceeding 1000 degrees to graphitize the carbon fiber. Since the raw material PITCH itself has a high carbon content, the decomposition gas generated during firing at high temperature (graphitization) is less than that of the PAN system described above. Therefore, the surface property is almost determined at the time of spinning and is generally good. When the purity of the raw material pitch is not good, it is considered that impurities are decomposed in the infusibilization or graphitization step after spinning to deteriorate the surface property. As described above, this is preferable from the viewpoint of improving the adhesion between the carbon fiber and the matrix resin, thereby improving the adhesion between the CFRP and the adherend. However, manufacturers of PITCH-based carbon fibers have a history of providing performance that is not inferior to that of PAN-based carbon fibers by improving the purity of the raw material PITCH and improving the graphitization process. Therefore, there is no idea of improving the adhesive force with the adherend by using carbon fiber having a poor surface property as required in the present invention.

  In catalogs of PAN-based carbon fibers and PITCH-based carbon fibers, tensile strength and tensile elastic modulus are usually displayed as physical property indicators. In PITCH-based carbon fiber, the correlation between these physical property indices and surface properties is low. On the other hand, the PAN-based carbon fiber shows a high correlation. Therefore, for PAN-based carbon fibers, selecting one having a low tensile strength and tensile modulus is directly connected to selecting one having an appropriate groove on the surface of the carbon fiber. “Adhesion is improved by deliberately selecting carbon fibers having a low rate”. Hereinafter, the CFRP prepreg based on the PAN-based carbon fiber will be described in detail. “T800SC (manufactured by Toray Industries, Inc.)” has the highest tensile strength as the current PAN-based carbon fiber. This has a tensile strength of 6 GPa and a tensile modulus of 300 GPa. There exists "T300 (made by Toray Industries, Inc.)" as a thing with lower tensile strength than this. This has a tensile strength of 3.6 GPa and a tensile modulus of 235 GPa. “TR30S (manufactured by Mitsubishi Rayon Co., Ltd.)” has a tensile strength of 4.4 GPa and a tensile elastic modulus of 234 GPa.

  CFRP prepreg based on the above “T800SC” is commercially available. The inventors decided to use a CFRP prepreg “Torayca 2255S-25 (manufactured by Toray Industries, Inc.)” having a thickness of 0.2 mm as a high yarn strength type prepreg. For comparison, a 0.2 mm thick prepreg “Pyrofil TR3523M (manufactured by Mitsubishi Rayon Co., Ltd.)” based on “TR30S” was used. This “Pyrofil TR3523M” was cut into small pieces, soaked in acetone to dissolve the matrix resin, the exposed carbon fiber “TR30S” was washed several times with acetone and dried, and the surface was observed with an electron microscope. It is shown in FIGS. It can be confirmed from FIG. 13 (2 000 times photograph) that a groove parallel to the fiber direction appears. FIG. 14 (2 000 times photograph) is an enlarged photograph of the most smooth part of the fiber surface, and the groove can also be confirmed in this range. From FIG. 15 (10,000 times photograph), it is understood that the unevenness constituting the groove is comparatively gentle and not steep. The surface characteristics obtained from the observation results were that at least one groove having a height difference of approximately 70 nm was present within a fiber length of 20 μm.

  On the other hand, the same process was performed on “Torayca 2255S-25”, and the result of observing the surface of the carbon fiber “T800S” with an electron microscope is shown in FIG. 16 (2,000 times photograph) and FIG. 17 (10,000 times photograph). Although the groove itself exists, the height difference is clearly small when compared with “TR30S”, which is 50 nm or less. In an experimental example to be described later, a CFRP member was created by laminating “Trekka 2255S-25” and “Pyrofil TR3523M”. In any of these, the matrix resin is a thermosetting epoxy resin composition. It was confirmed whether or not there was a difference in adhesive strength due to the difference in surface properties between the two.

[Create CFRP member]
A CFRP member is prepared by laminating the CFRP prepreg described above. The process of creating a CFRP member from a CFRP prepreg is as follows. A CFRP prepreg sheet is cut and a large number of prepreg pieces are produced. These prepreg pieces are cut so as to match the shape of each part of the CFRP member. The whole of the prepreg pieces is laminated with a jig, and the whole is put into an autoclave and heated while being evacuated. When the matrix resin is heated in an autoclave, it melts at 80 to 90 ° C. to become a highly viscous liquid material. Therefore, the matrix resin is depressurized to near vacuum and left in the air and the prepreg pieces. To eliminate air. The timing is further increased while the temperature is raised, and the autoclave is pressurized. By this pressurization, the voids after the air escapes are crushed, and the matrix resin goes to complete curing. The curing temperature is 140 to 180 ° C., and it is usually placed at this temperature for 1 hour or longer.

  Here, in the present invention, a CFRP prepreg based on a carbon fiber having a poor surface property (resulting in low tensile strength and tensile elastic modulus) is used for the purpose of improving the adhesion between the CFRP and the adherend. use. You may comprise a CFRP member only with such a CFRP prepreg. On the other hand, in CFRP members (CFRP prepreg laminates), carbon fibers having a high tensile strength and high tensile modulus may be used for CFRP prepregs other than the CFRP prepreg serving as a layer in contact with the adherend or the adhesive. Absent. Rather, it can be said that the CFRP prepreg other than the surface layer is preferably a carbon fiber having good performance in consideration of the strength of the entire CFRP member. As described above, only the CFRP prepreg located on the surface layer uses carbon fibers with poor surface properties, and other CFRP prepregs use those with good surface properties and high tensile strength and tensile elastic modulus. An example of creating is shown below.

  When a CFRP member having a thickness of 3 mm is prepared by laminating CFRP prepreg, a CFRP prepreg based on carbon fiber having a smooth surface (high tensile strength and high tensile modulus) is laminated to a thickness of 2.4 mm. . That is, if the CFRP prepreg is 0.2 mm thick, 12 sheets are laminated. Three CFRP prepregs having a thickness of 0.2 mm based on carbon fibers having a concavo-convex surface (low tensile strength and low tensile modulus) are laminated thereon. The thickness of the CFRP prepreg constituting the surface layer should be adjusted as appropriate. Many CFRP prepregs have a thickness of 0.05 to 0.2 mm, and there are a single layer type and a multilayer type. If only the thinnest 0.05 mm CFRP prepreg is used, only this CFRP prepreg constitutes a layer in contact with the adherend or adhesive. In this case, there is a case where the rigidity of the layer becomes a problem and the ease of peeling off from the CFRP prepreg constituting the lower layer may be a problem. Therefore, the thickness of the surface layer is appropriately adjusted.

In the adhesion experiment described later, CFRP prepregs having a thickness of 45 mm × 15 mm and a thickness of 3 mm were bonded to each other with an adhesion area of 0.5 to 0.6 cm ² and the shear breaking strength was measured. A tensile load of approximately ² to 4 kN is applied to the surface edge 0.5 to 0.6 cm ² of the CFRP prepreg. From past experiments, if the relationship between the adhesion area and the load in this range, the thickness of the CFRP prepreg (based on carbon fiber having low tensile strength and tensile modulus) constituting the surface layer should be about 0.6 mm. For example, peeling between the layer and the layer below it does not matter. If the adhesion area with respect to the size (45 mm × 15 mm) of the CFRP prepreg is smaller, the CFRP prepreg constituting the surface layer may be thinner.

[Preparation of joined body by co-bonding method]
A method for producing a joined body of a CFRP member and an adherend by the cobond method will be described. Fix the laminate of CFRP prepreg with a jig, put it in an autoclave, raise the temperature under reduced pressure, return to normal pressure after the temperature of the laminate rises to about 90 ° C, and further pressurize it to several atmospheres . Since the CFRP prepreg is once softened around 90 ° C., the air sandwiched between the layers of the CFRP prepreg is released at this point. Then, by applying pressure, the air gap after the air has escaped is crushed. Further, the laminate is heated to the curing temperature to be completely cured, the heating is stopped, and the laminate is taken out from the autoclave. This laminate is a CFRP member. Alternatively, the CFRP member is formed by cutting the laminate with a high-pressure water cutter as necessary. A bonded body is created by bonding the CFRP member and the adherend (CFRP member or metal alloy) with an adhesive.

[Creating a bonded body by the cocure method]
On the other hand, in the production of the bonded body by the co-curing method, the uncured CFRP member is not bonded to the adherend, but is heated and integrated in a state where the uncured CFRP prepreg and the adherend are conjugated. For example, when uncured CFRP prepreg laminates are integrated, they are fixed using a jig in a state in which a predetermined range of CFRP prepreg laminates is in close contact. And there exists a method of hardening the whole by putting in an autoclave in the state fixed with the jig | tool. This is an adhesion method between CFRP (a laminate of uncured CFRP prepregs) by a co-curing method. Here, a laminate of uncured CFRP prepregs may be bonded together via an epoxy adhesive. That is, an epoxy adhesive is applied to the predetermined range, and the CFRP prepreg matrix resin and the epoxy adhesive are cured at a time in an autoclave. This is also adhesion by the co-curing method. In the case where it is difficult to apply a tightening force from above and below to the contact surfaces of the CFRP prepreg laminates, it is preferable to use an epoxy adhesive.

  In addition, when the uncured CFRP prepreg laminate and the metal alloy are bonded, an epoxy adhesive is first applied to the bonding region on the surface of the metal alloy, and then a soaking process described later is performed. Thereafter, the metal alloy and the uncured CFRP prepreg laminate are brought into close contact with each other and fixed with a jig. This is placed in an autoclave and heated to cure the CFRP prepreg matrix resin and epoxy adhesive at a time. This is also adhesion by the co-curing method.

[Roughening of CFRP member]
When the CFRP member is bonded to the adherend, a stable adhesive force can be obtained by roughening the surface of the CFRP member. This surface can be polished with abrasive paper, and as a result of trial and error by the present inventors, 80-480, preferably 120-240, as specified in JIS R6252 A material obtained by polishing the surface of the CFRP member about 10 to 20 times was an adherend that stably exhibited high adhesive strength. In order to remove dirt (fine powder) adhering to the roughened surface, the CFRP member is immersed in an aqueous solution containing a detergent and then dried. Alternatively, the dirt on the roughened portion may be removed with a strong water flow, soaked in tap water or pure water, washed, and dried. In the experimental examples to be described later, abrasive paper is used, but the polishing member is not limited to abrasive paper. In the mass production process, sandblasting can be used instead of abrasive paper.

  Roughening to such an extent that a part of the carbon fiber is exposed from the surface of the CFRP member is preferable. This is because the adhesion between the carbon fiber and the one-component epoxy adhesive is generally superior to the adhesion between the carbon fiber and the matrix resin. When a commercially available one-component epoxy adhesive is used, the adhesion between the carbon fiber and the one-component epoxy adhesive is superior to the adhesion between the carbon fiber and the matrix resin at room temperature. However, at a high temperature of 100 ° C. or higher, the adhesive force between the commercially available one-component epoxy adhesive and the carbon fiber is sharply reduced, and breakage occurs between the one-component epoxy adhesive and the carbon fiber. That is, at a high temperature, not the adhesive force between the carbon fiber and the matrix resin in the CFRP prepreg used in the present invention, but a breakage is caused by a decrease in the adhesive force between the carbon fiber and the one-component epoxy adhesive.

  Based on this result, if it was possible to improve the adhesion between the carbon fiber and the one-component epoxy adhesive at high temperature, the CFRP member and the adherend were bonded extremely firmly from room temperature to high temperature. A joined body can be obtained. That is, since the adhesive force between the carbon fiber and the matrix resin becomes a problem at room temperature, the adhesive force between the two is improved by improving the carbon fiber (selecting the optimum carbon fiber). On the other hand, since the adhesive force between the carbon fiber and the one-component epoxy adhesive becomes a problem at high temperatures, an attempt was made to improve this adhesive force by improving the one-component epoxy adhesive. When the heat-resistant one-component epoxy adhesive developed by the present inventors is used, the adhesive force between the carbon fiber and the adhesive not only at room temperature but also at 100 to 150 ° C. Since it exceeds the force, it is possible to obtain a joined body in which the CFRP member and the adherend are bonded extremely firmly from room temperature to high temperature. This is because the one-component epoxy adhesive with improved surroundings of the exposed carbon fiber is covered, and as a result, the heat resistance as CFRP is improved. This adhesive will be described below.

[One-part epoxy adhesive]
In the present invention, the composition of the epoxy adhesive is not particularly limited. However, in order to secure a stable adhesive force from room temperature to high temperature and to enhance the adhesive force with the metal alloy material having the NAT conditions, it is preferable to use a material having an optimized composition. The following is known about a general one-component epoxy adhesive. That is, an aromatic diamine is often used as the curing agent. When aromatic diamine is used as the curing agent, the amount added is optimally based on the epoxy equivalent, and is usually 25 to 35 parts by mass with respect to 100 parts by mass of the epoxy resin. The most commonly used aromatic diamines as curing agents are 4,4'-diaminodiphenyl sulfone and 3,4'-diaminodiphenyl sulfone. On the other hand, dicyandiamide powder is used as the curing agent so that the adhesive that the present inventors consider preferable is low in the content of the curing agent.

  When dicyandiamide powder is used, the addition amount that maximizes the adhesive performance is only 3 to 6 parts by mass with respect to 100 parts by mass of the epoxy resin, and is as large as 15 to 25 parts by mass calculated based on the epoxy equivalent. Different. As a result of the inventors creating a one-component epoxy adhesive in which an epoxy resin and dicyandiamide powder (curing agent) are mixed and performing an adhesion experiment between metal alloys using this adhesive, 100 mass of epoxy resin is obtained. In particular, the addition of 3 to 6 parts by mass exhibited particularly high adhesive strength. In other words, when the addition amount of the dicyandiamide powder is larger than the above range with respect to 100 parts by mass of the epoxy resin (for example, when 15 parts by mass to 30 parts by mass), a tendency that a strong adhesive force cannot be obtained is found. It was.

  These results show that by using dicyandiamide powder as a curing agent, it may not comply with the theory of addition polymerization, which is a prerequisite for considering the epoxy equivalent, that is, it may act as a polymerization catalyst. Yes. In short, by using dicyandiamide powder instead of aromatic diamine as the curing agent for the one-part epoxy adhesive, the ratio of the curing agent in the one-part epoxy adhesive is reduced and the epoxy in the one-part epoxy adhesive is reduced. The base concentration can be increased. This is preferred for the present invention.

(Optimized one-part epoxy adhesive)
The composition of the one-component epoxy adhesive preferable for use in the present invention is as follows. When the total epoxy resin mixture constituting this one-component epoxy adhesive is 100 parts by mass, 60 to 75 parts by mass of bisphenol A type epoxy resin mainly composed of bisphenol A type epoxy resin monomer, and epoxy group It is a polyfunctional type having 3 or more and 25 to 40 parts by mass of an epoxy resin having an aromatic ring. This epoxy resin mixture has (1) 60 to 75 parts by mass of bisphenol A type epoxy resin monomer, (2) 0 to 15 parts by mass of bisphenol A type epoxy resin oligomer, and (3) many having three or more epoxy groups. What mixed 25-40 mass parts of epoxy resins which are functional types and have an aromatic ring is preferable. 3 to 6 parts by mass of dicyandiamide powder as a curing agent is added to 100 parts by mass of this epoxy resin mixture, and 3- (3,4-dichlorophenyl) -1,1-dimethylurea powder as a curing aid. Is added to 1 to 3 parts by mass. It is preferable to add the curing agent and the curing aid after adding the following filler to the epoxy resin and mixing them.

  In the one-component epoxy adhesive according to the present invention, a filler is added to the basic composition. Talc powder or clay powder having a particle size distribution center of 10 to 30 μm, aluminum powder having a particle size distribution center of 10 to 30 μm, and polyethersulfone with a hydroxyl group having a particle size distribution center of 10 to 30 μm Add resin powder. In particular, the adhesive force could be improved by using aluminum powder. In the past, the inventors conducted a bonding experiment using a one-component epoxy adhesive in which talc was added as an inorganic filler and a one-component epoxy adhesive in which aluminum powder was added as an inorganic filler. The adhesive strength of was high. These causes are presumed to be due to the fact that the surface of the aluminum powder is also a natural oxidation layer of aluminum, so that the affinity for the epoxy resin was better than that of talc.

  A polyethersulfone resin powder with a hydroxyl group was added for the purpose of improving impact resistance. Even when 5 to 30 parts by mass of a hydroxyl group-containing polyethersulfone resin powder having a particle size distribution center of 10 to 30 μm was added to 100 parts by mass of the total epoxy resin, the curing performance and the adhesion performance were not affected. Polyethersulfone resin (hereinafter referred to as “PES”) is a thermoplastic resin having a melting point of 300 ° C. or higher, and is sufficiently hard from room temperature to about 150 ° C., but it creeps and deforms when an excessive force is applied. Therefore, it gives impact resistance to the cured adhesive. The amount of filler added is 100 parts by mass of the total epoxy resin, 5 to 20 parts by mass of talc powder or clay powder, 10 to 60 parts by mass of aluminum powder, and polyethersulfone resin powder with a hydroxyl group. 5 to 30 parts by mass.

[Soaking process]
(Metal alloy)
After applying a one-component epoxy adhesive to the surface of the metal alloy satisfying the first to third conditions that conform to NAT, the metal alloy is sealed in a container such as a desiccator, and the container is vacuumed. The pressure is once reduced with a pump or the like, and then returned to normal pressure. Specifically, the inside of the container is depressurized to about several tens of mmHg and left for a certain period of time (approximately several seconds to several minutes), and then air is returned to normal pressure (or pressure is increased to a pressure of several atmospheres or more). preferable. The time in which the pressure is reduced is adjusted according to the degree of penetration of the adhesive into the ultra-fine irregularities. This depressurization / return to normal pressure operation is preferably repeated several times. It is preferable that the container used for this decompression / normal pressure return operation, for example, a desiccator, is warmed to 50 to 70 ° C. before use. This is to reduce the viscosity of the applied adhesive so that it can easily penetrate into the ultra-fine irregularities on the surface. By setting the adhesive viscosity of the adhesive to 15 Pa seconds or less, preferably 10 Pa seconds or less, the ultra fine unevenness is caused to enter. The metal alloy soaked and treated is taken out of the container and placed in a hot air dryer to cure the adhesive.

  Here, when the viscosity of the adhesive to be applied to the surface of the metal alloy is low (for example, 10 Pa seconds or less), the adhesive penetrates into the ultra-fine irregularities without performing the above-described decompression / normal pressure return operation. There is a case. In this case, of course, the soaking process is unnecessary. Moreover, even if the viscosity of the adhesive to be applied is high, by warming the metal alloy, the viscosity of the adhesive may decrease after application and may enter into the ultra-fine irregularities. Even in this case, the soaking process is unnecessary. The heating and the soaking process of the metal alloy before application of the adhesive may be performed according to the degree of penetration of the adhesive into the ultra-fine irregularities.

(CFRP member)
After applying a one-component epoxy adhesive to a specified part of the roughened CFRP member, place it in a container such as a desiccator, seal it, and once depressurize the container with a vacuum pump, then return to normal pressure I do. Specifically, the inside of the container is depressurized to about several tens of mmHg and left for a certain period of time (approximately several seconds to several minutes), and then air is returned to normal pressure (or pressure is increased to a pressure of several atmospheres or more). preferable. The time for placing the pressure-reduced state is adjusted according to the degree of intrusion into the irregularities related to the roughened portion of the adhesive. The purpose of this operation is to allow the adhesive to penetrate into the irregularities on the surface of the CFRP member caused by the roughening. That is, the epoxy resin cured product obtained by curing the CFRP matrix resin is soaked with an adhesive as an epoxy adhesive. When the viscosity of the adhesive after mixing the curing agent is as high as several tens of Pa seconds or more, the container used for the soaking process is heated to 50 to 70 ° C. in advance. Thus, the viscosity of the epoxy adhesive is set to 15 Pa seconds or less, preferably 10 Pa seconds or less.

  Here, when the viscosity of the adhesive to be applied to the CFRP member is low (for example, 15 Pa seconds or less), it is not necessary to perform the above-described decompression / normal pressure return operation, and the adhesive is uneven on the roughened portion. May invade. In this case, of course, the soaking process is unnecessary. Even if the viscosity of the adhesive to be applied is high, by warming the CFRP member, the viscosity of the adhesive may decrease after application and may enter the irregularities of the roughened portion. Even in this case, the soaking process is unnecessary. The heating and soaking process of the CFRP member before application of the adhesive may be performed according to the degree of penetration of the adhesive into the unevenness.

  In the present invention, by selecting a carbon fiber having a low tensile strength and tensile modulus, the adhesion between the carbon fiber and the matrix resin in a CFRP prepreg based on the carbon fiber is improved. As a result, the CFRP member using the CFRP prepreg in the portion to be bonded and the adherend can be firmly bonded. When bonding is performed by the cobond method, and the adherend is a metal alloy that satisfies the three conditions of NAT, in the prior art, the adhesive force between the metal alloy and the one-component epoxy adhesive is the carbon fiber and the matrix. The adhesive strength with the resin was exceeded. Thereby, there existed a subject that the effect of the strong joining based on NAT was attenuated as the whole composite. However, this problem has been solved by the present invention. Also in the co-bond adhesion between the CFRP members, the adhesion force of the joined body was similarly improved by improving the adhesion force between the carbon fiber and the matrix resin. Further, when the CFRP member and the adherend (metal alloy or CFRP) are bonded by the co-curing method, the bonded body is stronger than before.

  The present invention is intended to realize strong bonding with a substrate by using a CFRP prepreg based on a PAN-based carbon fiber, which is generally classified as lower and has a low tensile strength. . Since the present inventors have already realized extremely strong adhesion between a one-component epoxy adhesive and a metal alloy satisfying the three conditions of NAT, or a CFRP matrix resin cured product and a metal alloy satisfying the three conditions of NAT. is there. As a result, there was a special case in which the entire bonded body was broken due to the adhesive force between the carbon fiber and the matrix resin when an extremely high shear breaking force (40 MPa or more at normal temperature) was given. Based on this particularity, the adhesion between the carbon fiber and the matrix resin is improved, and the bonding force between the CFRP member and the adherend (CFRP member or metal alloy) is further enhanced under such special circumstances. is there.

  Among the CFRP members, those other than the surface layer that is used for adhesion, the tensile strength of the CFRP member as a whole is improved by using a CFRP prepreg based on a PAN-based carbon fiber having a high tensile strength. That is, by using a lower CFRP prepreg only for the surface layer used for adhesion, it was possible to obtain a member having good adhesion performance and excellent tensile strength as the CFRP member itself. Further, by using the one-component epoxy adhesive developed by the present inventors, it was possible to produce a joined body that was not easily broken even at a high temperature of 100 ° C. or higher. The present invention can be easily implemented by general manufacturers other than carbon fiber and CFRP prepreg manufacturers, and is a technology that greatly contributes to the expansion of the CFRP member area.

FIG. 1 is an electron micrograph ((a): 10,000 times, (b): 100,000 times) of a surface obtained by chemically etching an A7075 aluminum alloy with a caustic soda aqueous solution and finely etching with a hydrated hydrazine aqueous solution. FIG. 2 is an electron micrograph ((a): 10,000 times, (b): 100,000 times) of a surface obtained by chemically etching an A5052 aluminum alloy with an aqueous caustic soda solution and finely etching with an aqueous hydrazine solution. FIG. 3 is a 100,000 times electron micrograph (100% magnification of (a) and (b)) of a surface obtained by chemically etching an AZ31B magnesium alloy with a citric acid aqueous solution and chemical conversion treatment with a potassium permanganate aqueous solution. FIG. 4 is an electron micrograph of a surface obtained by chemically etching a C1100 copper alloy with an aqueous solution of sulfuric acid and hydrogen peroxide and surface-treating with an aqueous solution of sodium chlorite ((a): 10,000 times, (b): 100,000 times) ). FIG. 5 is an electron micrograph ((a): 10,000 times, (b): 100,000) of a surface obtained by chemically etching a C5191 phosphor bronze alloy with sulfuric acid / hydrogen peroxide aqueous solution and surface hardening treatment with sodium chlorite aqueous solution. Times). Fig. 6 shows electron micrographs of the surface of KFC copper alloy chemically etched with sulfuric acid / hydrogen peroxide solution and surface hardened with sodium chlorite solution ((a): 10,000 times, (b): 100,000 times) ). FIG. 7 is an electron micrograph of a surface obtained by chemically etching a KLF5 copper alloy with sulfuric acid / hydrogen peroxide aqueous solution and surface-hardening with sodium chlorite aqueous solution ((a): 10,000 times, (b): 100,000 times) ). FIG. 8 is an electron micrograph ((a): 10,000 times, (b): 100,000 times) of a surface obtained by chemically etching a “KS40” pure titanium-based titanium alloy with an aqueous solution of 1 hydrogen difluoride ammonium. FIG. 9 is an electron micrograph ((a): 10,000 times, (b): 100,000 times) of a surface obtained by chemically etching a “KSTi-9” α-β titanium alloy with an aqueous solution of ammonium hydrogen difluoride. is there. FIG. 10 is an electron micrograph ((a): 10,000 times, (b): 100,000 times) of a surface obtained by chemically etching SUS304 stainless steel with a sulfuric acid aqueous solution. FIG. 11 is an electron micrograph ((a): 10,000 times, (b): 100,000 times) of a surface obtained by etching a SPCC cold rolled steel material with a sulfuric acid aqueous solution. FIG. 12 is an electron micrograph ((a): 10,000 times, (b): 100,000 times) of the surface of SPHC hot-rolled steel material etched with a sulfuric acid aqueous solution. FIG. 13 is a 2000 × electron micrograph of carbon fiber “TR30S (manufactured by Mitsubishi Rayon Co., Ltd.)”. FIG. 14 is a 2000 × electron micrograph of carbon fiber “TR30S (manufactured by Mitsubishi Rayon Co., Ltd.)”. FIG. 15 is a 10,000 times electron micrograph of carbon fiber “TR30S (manufactured by Mitsubishi Rayon Co., Ltd.)”. FIG. 16 is a 2000 × electron micrograph of carbon fiber “T800SC (manufactured by Toray Industries, Inc.)”. FIG. 17 is a 10,000 times electron micrograph of carbon fiber “T800SC (manufactured by Toray Industries, Inc.)”. FIG. 18 is a structural diagram of a firing jig for producing a joined body of CFRPs or a composite of a metal alloy and CFRP. FIG. 19 is an external view showing the shape of a composite of a metal alloy and CFRP, or a joined body of CFRP. FIG. 20 is a cross-sectional view showing a surface structure when a metal alloy and a one-component epoxy adhesive are joined. FIG. 21 is a structural diagram of a firing jig for producing a CFRP plate by laminating CFRP prepregs. FIG. 22 is an external view showing the shape of a reinforced metal alloy / CFRP composite.

(Metal alloy that meets NAT requirements)
In the following experimental examples, a metal alloy satisfying the three conditions “NAT” is used as the CFRP adherend. The metal alloy having a surface structure based on the above-described “NAT” is not particularly limited in theory. However, “NAT” can actually be applied to hard and practical metal alloys. The inventors of the present invention have confirmed that “NAT” can be applied to metal alloy types mainly composed of aluminum, magnesium, copper, titanium, and iron. Patent Document 1 describes an aluminum alloy. Patent Document 2 describes a magnesium alloy. Patent Document 3 describes a copper alloy. Patent Document 4 describes a titanium alloy. Patent Document 5 describes stainless steel. Patent Document 6 describes general steel materials. However, since “NAT” aims to improve the adhesive force by the anchor effect, it is not limited to at least these metal alloy types. Hereinafter, a surface treatment process for making the surface of the metal alloy into a surface structure conforming to the “NAT” condition will be described.

(Chemical etching)
The chemical etching in this surface treatment process is intended to produce a roughness on the order of microns on the surface of the metal alloy. There are various types of corrosion, such as general corrosion, pitting corrosion, and fatigue corrosion, but it is possible to select an appropriate etching agent by selecting a chemical species that causes general corrosion for the metal alloy and performing trial and error. According to literature records (for example, "Chemical Engineering Handbook (edited by Chemical Engineering Association)"), aluminum alloys are basic aqueous solutions, magnesium alloys are acidic aqueous solutions, stainless steel and general steel materials in general are hydrohalic acid such as hydrochloric acid, sulfurous acid, There is a record that the entire surface is corroded by an aqueous solution of sulfuric acid or a salt thereof.

  In addition, copper alloys with strong corrosion resistance can be corroded entirely by highly concentrated nitric acid aqueous solution or strongly acidic oxidizing acid such as hydrogen peroxide or oxidizer compound liquid, and titanium alloys are oxalic acid or hydrofluoric acid based It can be seen from technical books and patent literature that it can be totally corroded with a special acid. The metal alloys that are actually sold in the market, such as pure copper-based copper alloys and pure titanium-based titanium alloys, have a purity of 99.9% or more and are hardly called alloys. Included in the alloy. Most of the metal alloys that are actually used are mixed with a wide variety of elements in order to obtain characteristic physical properties, and there are few pure metal materials, and they are substantially alloys.

  That is, most metal alloys are alloyed from pure metal for the purpose of improving corrosion resistance without deteriorating the original metal properties. Therefore, depending on the metal alloy, even if the acid / base or a specific chemical substance is used, the target chemical etching is often not possible. In practice, appropriate chemical etching is performed by trial and error while devising the concentration of the acid / base aqueous solution to be used, the liquid temperature, the immersion time, and, in some cases, the additive.

  Regarding the chemical etching method, Patent Document 1 describes an aluminum alloy, Patent Document 2 describes a magnesium alloy, Patent Document 3 describes a copper alloy, Patent Document 4 describes a titanium alloy, and Patent Document 5 describes a stainless steel. And Patent Document 6 described general steel materials.

  The points that are generally common in the work actually performed will be described. After shaping the metal alloy into a predetermined shape, the metal alloy is degreased by immersing it in an aqueous solution in which a degreasing agent for the metal alloy is dissolved and washed with water. This process is a process for removing most of the machine oil and finger grease adhering in the process of shaping the metal alloy, and it is preferably always performed. Then, it is preferably immersed in a thinly diluted acid / base aqueous solution and washed with water. This is a process that the present inventors have referred to as preliminary acid cleaning and preliminary base cleaning. In the case of a metal alloy that corrodes with an acid such as a general steel material, it is immersed in a basic aqueous solution and washed with water. Further, in the case of a metal alloy that is particularly rapidly corroded with a basic aqueous solution such as an aluminum alloy, it is immersed in a dilute acid aqueous solution and washed with water. These are processes in which a solution opposite to the aqueous solution used for chemical etching is attached (adsorbed) to the metal alloy in advance, and the subsequent chemical etching starts without an induction period, so that the reproducibility of the process is remarkably improved. . Therefore, the preliminary acid cleaning and preliminary base cleaning steps are not essential, but are preferably employed in practice. After these steps, a chemical etching step is performed.

(Fine etching and surface hardening treatment)
The purpose of the fine etching in the surface treatment step is to form ultra-fine irregularities on the surface of the metal alloy. Moreover, the surface hardening process in this invention aims at making the surface layer of a metal alloy into a thin layer of a metal oxide or a metal phosphate. Depending on the type of metal alloy, nano-order fine etching may be performed at the same time by performing the chemical etching, and ultra-fine irregularities may be formed. Furthermore, depending on the type of metal alloy, the natural oxide layer on the surface may be thicker than the original and the surface hardening process may be completed. For example, a pure titanium-based titanium alloy is only subjected to chemical etching, so that the surface has a roughness on the order of microns and ultra-fine irregularities are also formed. That is, fine etching is performed together with chemical etching. However, in many cases, it is necessary to perform fine etching or surface hardening treatment after forming a large uneven surface on the order of microns by chemical etching.

  Even at this time, we are often hit by unpredictable chemical phenomena. That is, when a metal alloy after chemical etching is reacted with an oxidizing agent or chemical conversion treatment for the purpose of surface hardening treatment or surface stabilization treatment, ultra fine irregularities may be formed on the resulting surface by chance. The surface layer that appears to be manganese oxide formed when a magnesium alloy is subjected to chemical conversion treatment with a potassium permanganate aqueous solution is a complex of rod-like crystals having a diameter of 5 to 10 nm that can be finally identified with a 100,000-fold electron microscope. Although this sample was analyzed by XRD (X-ray diffractometer), diffraction lines derived from manganese oxides could not be detected, but it is clear by XPS analysis that the surface was covered with manganese oxide. The reason why XRD could not be detected is that the crystal was a thin layer exceeding the detection limit. In short, the magnesium alloy was subjected to a chemical conversion treatment as a surface hardening treatment, so that fine etching was also completed.

  The same applies to copper alloys. When surface hardening treatment was performed to change the surface to cupric oxide by oxidation under basic conditions, the surface of pure copper-based copper alloys was covered with an elliptical hole opening. It becomes an ultra fine uneven surface. On the other hand, in the case of a copper alloy that is not pure copper-based, not a concave shape but a particle size or an indefinite polygonal shape having a diameter of 10 to 150 nm is continuous, and an ultrafine uneven surface in a form of being partially melted and stacked. Even in this case, most of the surface is covered with cupric oxide, and the hardening of the surface and the formation of ultrafine irregularities occur simultaneously.

  For general steel materials, although further verification is required, ultra-fine irregularities are often formed only by chemical etching to form micron-order roughness, and originally the surface layer (natural oxide layer) In some cases, the condition of “NAT” is provided without performing a surface hardening process or a fine etching process again. The problem at that time is that the corrosion resistance of the natural oxide layer is not sufficient, so that corrosion starts before the bonding step, and the adhesive strength is reduced in a short time depending on the environment after bonding. These can be prevented by chemical conversion treatment. For example, regarding a joined body in which general steel materials (SPCC: cold rolled steel materials) not subjected to chemical conversion treatment are bonded with a phenol resin adhesive, the adhesive strength rapidly decreased in a short period of 4 weeks. On the other hand, regarding the joined body in which the general steel materials (SPCC) subjected to the chemical conversion treatment were bonded to each other with the phenol resin-based adhesive, the initial adhesive force did not decrease during the same period.

  In addition, the present inventors have generally confirmed that when the thickness of a film (chemical conversion film) formed on the surface of a metal alloy by chemical conversion treatment is thick, the adhesive force often decreases. A strong adhesive force can be obtained when the thin layer is such that the diffraction line is not detected by XRD, such as the thin layer of manganese oxide adhered to the magnesium alloy. When metal alloys having a thick chemical conversion film are bonded to each other with an epoxy adhesive and subjected to a destructive test, most of the fracture surface is between the chemical conversion film and the metal alloy layer. In experiments conducted by the present inventors, the bonding force between the thick chemical conversion film and the cured epoxy adhesive was always stronger than the bonding force between the chemical conversion film and the metal alloy. That is, even with a general steel material, it is considered that the adhesive strength does not decrease for a long period of time if the chemical conversion treatment time is further increased to increase the thickness of the chemical conversion treatment layer. However, if the chemical conversion film is thickened, the adhesive strength itself is lowered. Therefore, the degree of balance depends on the purpose of use and application.

Embodiments of the present invention will be described below. The equipment used for measurement etc. is shown below.
(A) X-ray surface observation (XPS observation)
ESCA “AXIS-Nova (Kraitos (USA) / Shimadzu Corporation (Kyoto Prefecture, Japan))” in the form of observing constituent elements on a surface having a diameter of several μm in a depth range of 1 to 2 nm was used.
(B) Electron microscope observation Using SEM type electron microscopes “S-4800 (manufactured by Hitachi, Ltd.)” and “JSM-6700F (manufactured by JEOL Ltd. (Tokyo, Japan))” at 1-2 KV Observed.
(C) Scanning probe microscope observation “SPM-9600 (manufactured by Shimadzu Corporation)” was used.
(D) X-ray diffraction analysis (XRD analysis)
“XRD-6100 (manufactured by Shimadzu Corporation)” was used.
(E) Measurement of Bonding Strength of Composite Material Using a tensile tester “MODEL-1323 (manufactured by Aiko Engineering Co., Ltd. (Osaka, Japan))”, the shear breaking strength was measured at a pulling speed of 10 mm / min.
Next, the surface treatment of the metal alloy that is the adherend of the CFRP member will be described.

[Experimental Example 1] (Surface treatment of aluminum alloy (A7075))
A commercially available aluminum alloy sheet “A7075” with a thickness of 3 mm was obtained and cut to produce a large number of rectangular (45 mm × 18 mm) A7075 pieces. A commercially available degreasing agent for aluminum alloy “NE-6 (manufactured by Meltex Co.)” was added to the water in the tank to prepare an aqueous solution at 60 ° C. and a concentration of 7.5%. The A7075 pieces were immersed in this for 7 minutes and washed thoroughly with water. Subsequently, a 1% hydrochloric acid aqueous solution having a temperature of 40 ° C. was prepared in another tank, and the A7075 pieces were immersed in this for 1 minute and washed thoroughly with water. Next, a 1.5% strength aqueous caustic soda solution at 40 ° C. was prepared in another tank, and the A7075 pieces were immersed in this for 4 minutes and washed thoroughly with water. Subsequently, a 3% nitric acid aqueous solution at 40 ° C. was prepared in another tank, and the A7075 pieces were immersed in this for 1 minute and washed with water. Next, an aqueous solution containing 3.5% monohydric hydrazine at 60 ° C. was prepared in another tank, and the A7075 pieces were immersed in the solution for 2 minutes and washed with water. Next, a 5% aqueous hydrogen peroxide solution was brought to 40 ° C., and the A7075 pieces were immersed in this for 5 minutes and washed with water. Next, the A7075 pieces were put in a hot air dryer set to 67 ° C. for 15 minutes and dried.

  After drying, the A7075 pieces were wrapped together with aluminum foil, which was then sealed in a plastic bag. When one of the same treatment was observed with an electron microscope, it was found that it was covered with a recess having a diameter of 40 to 100 nm. A photograph when the electron microscope is observed at 10,000 times and 100,000 times is shown in FIG. The roughness data was obtained by scanning probe microscope. According to this, RSm was 3-4 μm, and Rz was 1-2 μm.

[Experimental example 2] (Surface treatment of aluminum alloy (A5052))
A commercially available 1.6 mm-thick aluminum alloy sheet “A5052” was obtained and cut to produce a large number of rectangular (45 mm × 18 mm) A5052 pieces. A commercially available degreasing agent for aluminum alloy “NE-6 (manufactured by Meltex Co.)” was added to the water in the tank to prepare an aqueous solution at 60 ° C. and a concentration of 7.5%. The A5052 piece was immersed in this for 7 minutes and washed thoroughly with water. Subsequently, a 1% concentration hydrochloric acid aqueous solution at 40 ° C. was prepared in another tank, and the A5052 pieces were immersed in this for 1 minute and washed thoroughly with water. Next, a 1.5% strength aqueous caustic soda solution at 40 ° C. was prepared in another tank, and the A5052 pieces were immersed in this for 2 minutes and washed thoroughly with water. Subsequently, a 3% concentration nitric acid aqueous solution at 40 ° C. was prepared in another tank, and the A5052 piece was immersed in this for 1 minute and thoroughly washed with water. Next, an aqueous solution containing 3.5% monohydric hydrazine at 60 ° C. was prepared in another tank, and the A5052 pieces were immersed in this for 2 minutes and washed with water. Next, the A5052 pieces were put in a warm air dryer set to 67 ° C. for 15 minutes and dried.

  After drying, the A5052 pieces were wrapped together with an aluminum foil, which was then placed in a plastic bag and sealed. When one of the same treatment was observed with an electron microscope, it was found to be covered with a recess having a diameter of 30 to 100 nm. A photograph when the electron microscope is observed at a magnification of 10,000 times and 100,000 times is shown in FIG. The roughness data was obtained by scanning probe microscope. According to this, RSm was 1-2 μm and Rz was 0.3-0.5 μm.

[Experiment 3] (Surface treatment of magnesium alloy)
A commercially available magnesium alloy plate “AZ31B” having a thickness of 1 mm was obtained and cut to produce a large number of rectangular (45 mm × 18 mm) AZ31B pieces. A commercially available magnesium alloy degreasing agent “Cleaner 160 (manufactured by Meltex)” was added to the water in the tank to prepare an aqueous solution at 65 ° C. and a concentration of 7.5%. The AZ31B piece was immersed in this for 5 minutes and washed thoroughly with water. Subsequently, a 1% hydrated citric acid aqueous solution at 40 ° C. was prepared in another tank, and the AZ31B piece was immersed in this for 6 minutes and washed thoroughly with water. Next, an aqueous solution containing 1% sodium carbonate and 1% sodium hydrogen carbonate at 65 ° C. was prepared in another tank, and the AZ31B piece was immersed in this for 5 minutes and washed thoroughly with water. Subsequently, a 15% caustic soda aqueous solution at 65 ° C. was prepared in another tank, and the AZ31B piece was immersed in this for 5 minutes and washed with water. Next, a 0.25% strength hydrated citric acid aqueous solution at 40 ° C. was prepared in another tank, and the AZ31B piece was immersed in this for 1 minute and washed with water. Next, an aqueous solution (45 ° C.) containing 2% potassium permanganate, 1% acetic acid, and 0.5% hydrated sodium acetate was prepared, and the AZ31B piece was immersed in this for 1 minute and washed with water for 15 seconds. Then, it was placed in a hot air dryer at 90 ° C. for 15 minutes and dried.

  After drying, the AZ31B pieces were wrapped together with aluminum foil, which was then placed in a plastic bag and sealed. When one of the same treatments was observed with an electron microscope, it was found that 5-10 nm diameter rod-shaped crystals were intricately entangled and their lumps gathered together with a diameter of about 100 nm, and the gathering formed a surface. There was a portion covered with fine irregularities. A photograph of the electron microscope observed at a magnification of 100,000 is shown in FIG. Further, when the roughness was observed by scanning with a scanning probe microscope, RSm was 2 to 3 μm and Rz was 1 to 1.5 μm.

[Experimental Example 4] (Surface treatment of copper alloy (C1100))
A tough pitch copper plate material “C1100”, which is a commercially available pure copper-based copper alloy with a thickness of 1 mm, was obtained and cut to create a large number of rectangular (45 mm × 18 mm) C1100 pieces. An aqueous solution (60 ° C.) containing 7.5% of a commercially available aluminum alloy degreasing agent “NE-6 (manufactured by Meltex Co.)” was prepared in a tank, and the C1100 pieces were immersed in this for 5 minutes and washed with water. Next, preliminary base washing was performed by immersing the C1100 piece in a 1.5% strength caustic soda solution at 40 ° C. for 1 minute and washing with water. Next, an aqueous solution containing 20% of an etching material for copper alloy “CB5002 (manufactured by MEC)” at 25 ° C. and 18% of 30% hydrogen peroxide was prepared, and the C1100 piece was immersed in this for 10 minutes and washed with water.

  Next, an aqueous solution (65 ° C.) containing 10% caustic soda and 5% sodium chlorite was prepared as an oxidizing aqueous solution in another tank, and the C1100 piece was immersed for 1 minute and washed thoroughly with water. Next, the C1100 piece was immersed in the above-described etching bath for 1 minute and washed with water, and then immersed in the above-described oxidizing aqueous solution for 1 minute and thoroughly washed with water. Next, the C1100 piece was placed in a hot air dryer at 90 ° C. for 15 minutes and dried. After drying, the C1100 pieces were wrapped together with aluminum foil, which was then placed in a plastic bag and sealed. One of the same treatment was subjected to a scanning probe microscope. As a result, RSm was 3 to 7 μm, and Rz was 3 to 5 μm. Moreover, when observed with an electron microscope of 100,000 times, it was found that the average diameter or major axis and minor axis averaged from 10 to 150 nm, and the hole openings or recesses existed on the entire surface at irregular intervals of 30 to 300 nm. Was covered. A photograph when the electron microscope is observed at a magnification of 10,000 times and 100,000 times is shown in FIG.

[Experimental Example 5] (Surface treatment of copper alloy (C5191))
A commercially available phosphor bronze plate material “C5191” having a thickness of 0.8 mm was obtained and cut to prepare a large number of rectangular (45 mm × 18 mm) C5191 pieces. An aqueous solution (60 ° C.) containing 7.5% of a commercially available aluminum alloy degreasing agent “NE-6 (manufactured by Meltex)” is prepared as a degreasing aqueous solution in a tank, and the C5191 piece is immersed in this for 5 minutes. Degreased and washed well with water. Subsequently, an aqueous solution (25 ° C.) containing 20% of a copper alloy etching material “CB5002 (made by MEC)” and 18% of 30% hydrogen peroxide was prepared in another tank, and the C5191 piece was immersed in this for 15 minutes. Washed with water. Next, an aqueous solution containing 10% caustic soda and 5% sodium chlorite was prepared as an oxidizing aqueous solution (65 ° C.) in another tank, and the C5191 pieces were immersed in this for 1 minute and washed thoroughly with water.

  Next, the C5191 piece was again immersed in the above-described etching solution for 1 minute, washed with water, then again immersed in the above-described oxidizing aqueous solution for 1 minute and washed with water. Next, the C5191 piece was placed in a hot air dryer at 90 ° C. for 15 minutes and dried. Wrapped in aluminum foil and stored. FIG. 5 shows a photograph of the same treated piece observed with an electron microscope at 10,000 times and 100,000 times. An observation with an electron microscope at a magnification of 100,000 times shows that the projections having an average diameter or major axis and minor axis of 10 to 200 nm are mixed together and have an ultra-fine irregular shape that is present on the entire surface. The shape was completely different from the structure. Moreover, it applied to the scanning probe microscope. As a result, RSm was 1 to 3 μm and Rz was 0.3 to 0.4 μm.

[Experimental example 6] (Surface treatment of copper alloy (KFC))
A commercially available iron-containing copper alloy sheet “KFC (manufactured by Kobe Steel)” having a thickness of 0.7 mm was obtained and cut to produce a large number of rectangular (45 mm × 18 mm) KFC pieces. An aqueous solution (60 ° C.) containing 7.5% of a commercially available aluminum alloy degreasing agent “NE-6 (manufactured by Meltex)” is prepared in a tank, and the KFC pieces are immersed in this for 5 minutes and then washed with water. Preliminary base washing was performed by immersing in an aqueous 1.5% caustic soda solution at 40 ° C. for 1 minute and washing with water. Next, an aqueous solution (25 ° C.) containing 20% of an etching material for copper alloy “CB5002 (manufactured by MEC)” and 18% of 30% hydrogen peroxide was prepared, and the KFC piece was immersed in this for 8 minutes and washed with water. .

  Next, an aqueous solution (65 ° C.) containing 10% caustic soda and 5% sodium chlorite was prepared as an oxidizing aqueous solution in another tank, and the KFC pieces were immersed in this for 1 minute and washed thoroughly with water. Next, the KFC piece was immersed in the above-described etching tank for 1 minute and washed with water, and then immersed in the above-described oxidizing aqueous solution for 1 minute and thoroughly washed with water. Next, the KFC pieces were placed in a hot air dryer at 90 ° C. for 15 minutes and dried. After drying, the KFC pieces were wrapped together with aluminum foil, which was then put in a plastic bag and sealed. One of the same treatment was subjected to a scanning probe microscope. As a result, RSm was 1 to 3 μm and Rz was 0.3 to 0.5 μm. Further, when observed with an electron microscope of 100,000 times, the entire surface was covered with an ultra fine uneven shape in which convex portions having an average diameter or major axis and minor axis of 10 to 200 nm were mixed and present on the entire surface. A photograph when the electron microscope is observed at a magnification of 10,000 times and 100,000 times is shown in FIG.

[Experimental Example 7] (Surface treatment of copper alloy (KLF5))
A commercially available special copper alloy plate material “KLF5 (manufactured by Kobe Steel)” having a thickness of 0.4 mm was obtained and cut to create a large number of rectangular (45 mm × 18 mm) KLF5 pieces. An aqueous solution (60 ° C.) containing 7.5% of a commercially available aluminum alloy degreasing agent “NE-6 (manufactured by Meltex)” is prepared in a tank, and the KLF5 piece is immersed in this for 5 minutes and then washed with water. Preliminary base washing was performed by immersing in an aqueous 1.5% caustic soda solution at 40 ° C. for 1 minute and washing with water. Next, an aqueous solution (25 ° C.) containing 20% of an etching material for copper alloy “CB5002 (manufactured by MEC)” and 18% of 30% hydrogen peroxide was prepared, and the KLF5 pieces were immersed in this for 8 minutes and washed with water.

  Next, an aqueous solution (65 ° C.) containing 10% caustic soda and 5% sodium chlorite was prepared as an oxidizing aqueous solution in another tank, and the KLF5 pieces were immersed in this for 1 minute and washed with water. Next, the KLF5 piece was immersed in the etching tank described above for 1 minute and washed with water, and then immersed in the aqueous solution for oxidation described above for 1 minute and thoroughly washed with water. Next, the KLF5 pieces were placed in a warm air dryer at 90 ° C. for 15 minutes and dried. After drying, the KLF5 pieces were wrapped together with an aluminum foil, and further put in a plastic bag and sealed. One of the same treatment was subjected to a scanning probe microscope. As a result, the mean valley interval (RSm) in JIS was 1 to 3 μm, and the maximum height roughness (Rz) was 0.3 to 0.5 μm. In addition, when observed with an electron microscope at a magnification of 100,000 times, a shape in which a particle having a diameter of 10 to 20 nm and an indefinite polygon having a diameter of 50 to 150 nm are mixed and stacked, that is, a lava plateau slope-like ultra fine uneven shape is formed. Almost the entire surface was covered. A photograph when the electron microscope is observed at a magnification of 10,000 times and 100,000 times is shown in FIG.

[Experiment 8] (Surface treatment of pure titanium alloy)
A commercially available pure titanium type titanium alloy plate “KS40 (manufactured by Kobe Steel)” having a thickness of 1 mm was obtained and cut to produce a large number of rectangular (45 mm × 18 mm) KS40 pieces. An aqueous solution (60 ° C.) containing 7.5% of a commercially available aluminum alloy degreasing agent “NE-6 (manufactured by Meltex)” was prepared in the tank, and this was used as a degreasing aqueous solution. The KS40 pieces were immersed in this degreasing aqueous solution for 5 minutes to degrease and washed thoroughly with water. Subsequently, an aqueous solution (60 ° C.) containing 2% of a universal etching material “KA-3 (manufactured by Metalworking Technology Laboratories)” containing 40% ammonium bifluoride in a separate tank is prepared in another tank. The piece was immersed for 3 minutes and washed thoroughly with ion-exchanged water. Next, the KS40 piece was immersed in a 3% nitric acid aqueous solution for 1 minute, washed with water, and then placed in a warm air dryer at 90 ° C. for 15 minutes to dry.

  After drying, the KS40 pieces were wrapped together with aluminum foil, which was then stored in a plastic bag. One piece subjected to the same treatment was observed with an electron microscope and a scanning probe microscope. From observation with an electron microscope, curved continuous mountain-shaped projections having a width and height of 10 to several hundreds of nanometers and a length of 10 nm or more (mostly several hundreds of nanometers) stand on the surface at intervals of 10 to several hundred nanometers. It was found to have an ultra-fine irregular surface of the shape. A photograph when the electron microscope is observed at a magnification of 10,000 times and 100,000 times is shown in FIG. Moreover, RSm was 1-3 micrometers and Rz was 0.8-1.5 micrometers by observation with the scanning probe microscope. Further, from the analysis by XPS, a large amount of oxygen and titanium were observed on the surface, and a small amount of carbon was observed. From these, it was found that the surface layer was composed mainly of titanium oxide, and because it was dark, it was estimated to be a trivalent titanium oxide.

[Experimental Example 9] (Surface treatment of α-β type titanium alloy)
A commercially available α-β type titanium alloy plate “KSTi-9 (manufactured by Kobe Steel)” having a thickness of 1 mm was obtained and cut to produce a large number of rectangular (45 mm × 18 mm) KSTi-9 pieces. An aqueous solution (60 ° C.) containing 7.5% of a commercially available aluminum alloy degreasing agent “NE-6 (manufactured by Meltex)” was prepared in the tank, and this was used as a degreasing aqueous solution. The KSTi-9 pieces were immersed in this degreasing aqueous solution for 5 minutes for degreasing and thoroughly washed with water. Next, an aqueous solution (40 ° C.) having a caustic soda concentration of 1.5% was prepared in another tank, and the KSTi-9 piece was immersed in this for 1 minute and washed with water. Next, in another tank, an aqueous solution (60 ° C.) in which 2% by weight of a commercially available general-purpose etching reagent “KA-3 (manufactured by Metalworking Technology Laboratories)” was dissolved was prepared, and the KSTi-9 piece was immersed in this for 3 minutes. And washed thoroughly with ion-exchanged water. Here, since the black smut was adhered to the KSTi-9 piece, it was immersed in a 3% concentration nitric acid aqueous solution at 40 ° C. for 3 minutes, and then immersed in ion-exchanged water subjected to ultrasonic waves for 5 minutes. The smut was dropped and again immersed in a 3% nitric acid aqueous solution for 0.5 minutes and washed with water. Next, the KSTi-9 pieces were placed in a hot air dryer at 90 ° C. for 15 minutes and dried. The obtained KSTi-9 pieces were dark brown with no metallic luster.

  After drying, the KSTi-9 pieces were wrapped together with an aluminum foil, which was then placed in a plastic bag and sealed. One piece subjected to the same treatment was observed with an electron microscope and a scanning probe microscope. A photograph when the electron microscope is observed at a magnification of 10,000 times and 100,000 times is shown in FIG. In addition to the portion very similar to the electron microscopic observation photograph 8 of Experimental Example 8, many dead leaf-like portions that are difficult to express were seen. Moreover, according to the scanning analysis by a scanning probe microscope, RSm was 4-6 micrometers and Rz was 1-2 micrometers.

[Experimental Example 10] (Stainless steel surface treatment)
A commercially available stainless steel plate material “SUS304” having a thickness of 1 mm was obtained and cut to produce a large number of rectangular (45 mm × 18 mm) SUS304 pieces. An aqueous solution (60 ° C.) containing 7.5% of a commercially available aluminum alloy degreasing agent “NE-6 (manufactured by Meltex)” was prepared in the tank, and this was used as a degreasing aqueous solution. The SUS304 piece was immersed in this degreasing aqueous solution for 5 minutes to degrease and washed thoroughly with water. Next, an aqueous solution (65 ° C.) containing 1% ammonium difluoride and 5% sulfuric acid in 5% was prepared in another tank, and the SUS304 piece was immersed in this for 4 minutes and washed thoroughly with ion-exchanged water. Next, the SUS304 piece was immersed in a 3% nitric acid aqueous solution at 40 ° C. for 3 minutes, washed with water, and then placed in a hot air dryer at 90 ° C. for 15 minutes to be dried.

  After drying, the SUS304 pieces were wrapped together with aluminum foil, which was then placed in a plastic bag and sealed. One piece subjected to the same treatment was observed with an electron microscope and a scanning probe microscope. A photograph when the electron microscope is observed at a magnification of 10,000 times and 100,000 times is shown in FIG. In the observation with an electron microscope, the surface was covered with an ultra-fine uneven shape of a shape in which a particle having a diameter of 20 to 70 nm or an indefinite polygonal shape was piled up, that is, a lava plateau sloped surface. Moreover, in the scanning analysis of the scanning probe microscope, RSm was 1-2 μm and Rz was 0.3-0.4 μm. Another one was subjected to XPS analysis. From this XPS analysis, a large amount of oxygen and iron was observed on the surface, and a small amount of nickel, chromium, carbon, a very small amount of molybdenum and silicon were observed. From these, it was found that the surface layer was mainly composed of metal oxide. This analysis pattern was almost the same as SUS304 before etching.

[Experimental Example 11] (Surface treatment of general steel (SPCC))
A commercially available cold-rolled steel plate material “SPCC” having a thickness of 1.6 mm was obtained and cut to produce a large number of rectangular (45 mm × 18 mm) SPCC pieces. A hole was made at the end of each SPCC piece, a copper wire coated with vinyl chloride was passed through the hole, and the copper wire was bent and processed so that the SPCC pieces did not overlap each other, so that all could be hung at the same time. An aqueous solution (60 ° C.) containing 7.5% of an aluminum alloy degreasing agent “NE-6 (Meltex)” was prepared in a tank, and the SPCC piece was immersed in the solution for 5 minutes, and tap water (Ota, Gunma) City). Then, a 1.5% aqueous solution of caustic soda at 40 ° C. was prepared in another tank, and the SPCC piece was immersed in this for 1 minute and washed with water. Next, an aqueous solution (50 ° C.) containing 10% of 98% sulfuric acid was prepared in another tank, and the SPCC pieces were immersed in this for 6 minutes and sufficiently washed with ion-exchanged water. Next, the SPCC piece was immersed in 1% ammonia water at 25 ° C. for 1 minute and washed with water, and then 2% potassium permanganate, 1% acetic acid, 0.5% hydrated acetic acid. It was immersed in an aqueous solution containing sodium (45 ° C.) for 1 minute and thoroughly washed with water. Next, the SPCC piece was placed in a hot air dryer at 90 ° C. for 15 minutes and dried.

  FIG. 11 shows the observation results of the SPCC pieces treated in the same manner with a 100,000 times electron microscope. From this photograph, it can be seen that the entire surface is covered with an ultra-fine uneven shape having an infinite number of steps having a height and depth of 80 to 200 nm and a width of several hundred to several thousand nm. The pearlite structure is exposed and it can be seen that the chemical conversion layer is very thin. On the other hand, in the scanning analysis with the scanning probe microscope, the roughness of RSm of 1 to 3 μm and Rz of 0.3 to 1.0 μm was observed.

[Experimental example 12] (Surface treatment of general steel (SPHC))
A commercially available hot rolled steel plate material “SPHC” with a thickness of 1.6 mm was obtained and cut to produce a large number of rectangular (45 mm × 18 mm) SPHC pieces. A hole was made in the end of each SPHC piece, and a copper wire coated with vinyl chloride was passed through the hole, and the copper wire was bent and processed so that the SPHC pieces did not overlap each other, so that all could be hung at the same time. An aqueous solution (60 ° C.) containing 7.5% of an aluminum alloy degreasing agent “NE-6 (Meltex)” was prepared in a tank, and the SPHC pieces were immersed in this for 5 minutes, and tap water (Ota, Gunma) City). Next, a 1.5% aqueous solution of caustic soda at 40 ° C. was prepared in another tank, and the SPHC pieces were immersed in this for 1 minute and washed with water. Next, an aqueous solution (65 ° C.) containing 10% 98% sulfuric acid and 1% ammonium difluoride was prepared in another tank, and the SPHC pieces were immersed in this for 2 minutes and washed thoroughly with ion-exchanged water. . Next, the SPHC piece was immersed in 1% ammonia water adjusted to 25 ° C. for 1 minute and washed with water. Next, the SPHC piece was dissolved in an aqueous solution containing 55% 80% orthophosphoric acid, 0.21% zinc white, 0.16% sodium silicofluoride, and 0.23% basic nickel carbonate (55 ° C). ) And then thoroughly washed with water. Next, the SPHC pieces were placed in a hot air dryer at 90 ° C. for 15 minutes and dried.

  From the result of observation of the obtained SPHC piece with a 100,000 times electron microscope (FIG. 12), an ultra-fine uneven shape having a shape in which steps having a height and depth of 80 to 500 nm and a width of several hundred to tens of thousands of nm are infinitely continued. It was found that almost the entire surface was covered, and this was also a pearlite structure. On the other hand, in scanning analysis with a scanning probe microscope, roughness with RSm of 1 to 3 μm and Rz of 0.3 to 1.0 μm was observed.

[Experimental example 13] (Preparation of one-component epoxy adhesive)
An epoxy resin “JER828 (manufactured by Japan Epoxy Resin Co., Ltd.)” whose main component is a monomer type of bisphenol A type epoxy resin and a molecular weight of about 1600, an oligomer type bisphenol A type epoxy resin “JER1004” (Japan) Epoxy Resin Co., Ltd.) ”, multifunctional phenol novolac type epoxy resin“ JER154 (Japan Epoxy Resin Co., Ltd.) ”, aniline type trifunctional epoxy resin“ JER630 (Japan Epoxy Resin Co., Ltd.) ”, average grain Fine talc with a diameter of 8-12 μm “Hi-micron HE5 (manufactured by Takehara Chemical Co., Ltd.)”, clay (Kaolin) “Satinton 5 (manufactured by Takehara Chemical Industry Co., Ltd.)” with the same particle size, 16μm pure aluminum-based aluminum alloy powder for filler Aluminum powder (manufactured by Toyo Aluminum Co., Ltd.), fine powder type dicyandiamide “DICY7 (manufactured by Japan Epoxy Resin Co., Ltd.)” which is a curing agent for epoxy resin, 3- (3,4-dichlorophenyl)-used as a curing aid A 1,1-dimethylurea “DCMU99 (manufactured by Hodogaya Chemical Co., Ltd.)” and a PES powder with a hydroxyl group having a particle size distribution center of 20 μm “Ultrazone E2020P-SRMicro (manufactured by BASF)” were obtained.

  Take 65 parts by weight of “JER828”, 5 parts by weight of “JER1004”, 10 parts by weight of “JER154”, and 20 parts by weight of “JER630” in a beaker and leave it in a hot air dryer at 160 ° C. The solid type “JER1004” was melted and stirred at the same time to make the whole uniform. Then, it stood to cool and stored as an epoxy resin liquid.

  Next, in a mortar, 100 parts by mass of the mixture, 10 parts by mass of talc powder “Himicron HE5 (manufactured by Takehara Chemical Co., Ltd.)” having a particle size distribution center of about 10 μm, and aluminum powder “filler having a particle size distribution center of 16 μm. 40 parts by weight of “aluminum powder”, 20 parts by weight of a polyethersulfone resin powder with a hydroxyl group having a particle size distribution center of 20 μm “Ultrazone E2020P-SRMicro (manufactured by BASF)”, fine powder dicyandiamide “DICY7” as a curing agent “5 parts by mass, 2.5 parts by mass of 3- (3,4-dichlorophenyl) -1,1-dimethylurea“ DCMU99 (Hodogaya Chemical Co., Ltd.) ”were taken. The mortar contents were mixed with a pestle for 3 minutes and kneaded. The mixture was allowed to stand for 1 hour and then kneaded again with a pestle for 1 minute. This was taken in a polyethylene bottle and aged at room temperature for 1 day, and then stored in a refrigerator at 5 ° C.

[Experimental Example 14] (Cocure adhesion between CFRP and A7075 aluminum alloy piece)
Prepare a CFRP prepreg “Torayca 2255S-25 (manufactured by Toray Industries, Inc.)” with a thickness of 0.2 mm based on a high-strength carbon fiber with a tensile strength of 6 GPa. From this, a rectangular piece of 45 mm × 15 mm (thickness 0.2 mm) ) Was cut out. In addition, a CFRP prepreg “Pyrofil TR3523M (manufactured by Mitsubishi Rayon Co., Ltd.)” having a thickness of 0.2 mm based on carbon fiber having a tensile strength of 4.4 GPa, which is lower than the former, is prepared, and a rectangular piece (45 mm × 15 mm) A number of 0.2 mm thickness) was cut out.

  On the other hand, a NAT-treated A7075 aluminum alloy piece subjected to surface treatment by the method of Experimental Example 1 was obtained. The one-component epoxy adhesive obtained in Experimental Example 13 was applied to the end of the aluminum alloy piece up to 4 mm. A composite of CFRP and aluminum alloy pieces is prepared using the firing jig 1 shown in FIG. When the mold body 2 and the mold bottom plate 5 are combined, a mold recess is formed by the side wall of the mold body 2 and the upper surface of the mold bottom plate 5. A release film 17 having a thickness of 0.05 mm was laid so as to cover the mold recess. An aluminum alloy piece 11 is placed on the release film 17 with the adhesive-coated surface facing upward, and a gap between the aluminum alloy piece 11 and the side wall of the mold body 2 is made of polytetrafluoroethylene resin (hereinafter referred to as “PTFE”). It was filled with spacers 16 made of.

  Next, three “pyrofil TR3523M” pieces were laminated on the upper surfaces of the aluminum alloy pieces 11 and the spacers 16. Furthermore, 12 “Treka 2255S-25” pieces were laminated on this “Pyrofil TR3523M” piece. A laminate of these 15 CFRP prepregs is shown as CFRP prepreg laminate 12 in the figure. Here, the left end portion of the lower surface of the “pyrofil TR3523M” piece, which is the lowermost layer of the CFRP prepreg laminate 12 shown in FIG. 18, is in contact with the adhesive application region on the upper surface of the aluminum alloy piece 11. In order to fill the gap between the CFRP prepreg laminate 12 and the side wall of the mold body 2, a PTFE spacer 13 was installed, and a release film 14 was laid so as to cover them.

  A PTFE block 15 was placed on the release film 14, and a 10 kg weight 18 made of iron was placed on the block 15 and placed in a large autoclave. The lid of the autoclave was closed and the internal temperature was adjusted to about 80 ° C., and then the internal pressure was reduced to 10 mmHg or less with a vacuum pump. After heating at this temperature for 10 minutes, the temperature was raised and when it reached 135 ° C., air was introduced to return to normal pressure. Then, it heated at 135 degreeC for 40 minutes, and raised the temperature to 165 degreeC after that, and heated for 30 minutes, adjusting so that it might be around 165 degreeC. Thereafter, the heating was stopped and the mixture was allowed to cool for 30 minutes. The autoclave was opened and the firing jig 1 was disassembled to obtain a composite of CFRP (cured product of CFRP prepreg laminate 12) and aluminum alloy pieces. FIG. 19 shows the appearance of the composite 10. The aluminum alloy piece 11 and the CFRP 12 are joined via the adhesive application region 13. In this way, a large number of composites 10 were prepared.

[Experimental Example 15] (Cocure bonding of CFRP and A7075 aluminum alloy piece)
In the same manner as in Experimental Example 14, a composite of 15 laminates of CFRP prepreg consisting only of “Trekka 2255S-25” pieces and A7075 aluminum alloy pieces subjected to the surface treatment of Experimental Example 1 was prepared. That is, in Experimental Example 14, 12 “Trekker 2255S-25” pieces and 3 “Pyrofil TR3523M” pieces were laminated, but in this Experimental Example, 15 “Trekker 2255S-25” pieces were laminated, and the bottom layer thereof. What is located in is used for adhesion | attachment with the 1 liquid epoxy adhesive of the surface of A7075 aluminum alloy piece.

[Experimental Example 16] (Measurement of adhesive strength)
With respect to the composite of CFRP and A7075 aluminum alloy piece obtained in Experimental Example 14, one week later, 7 pairs were pulled and broken using a testing machine, and the shear breaking force was measured. These tests were performed at normal temperature, 100 ° C., and 150 ° C. The results (average value of 7 pairs) are shown in Table 1 (Experimental Example 16-1). Moreover, about the composite of the CFRP and A7075 aluminum alloy piece obtained in Experimental Example 15, one pair was pulled and ruptured using a testing machine after one week, and the shear breaking force was measured. These tests were performed at normal temperature, 100 ° C., and 150 ° C. The results (average value of 7 pairs) are shown in Table 1 (Experimental Example 16-2).

  Table 1 shows the average value of the shear breaking strength of 7 pairs of composites at room temperature, 100 ° C., and 150 ° C. The brackets indicate the minimum and maximum values of the shear breaking force measured for 7 pairs of composites (minimum value to maximum value). From this result, in the temperature range from room temperature to 100 ° C., the shear breaking force of the composite using “Pyrofil TR3523M” having a tensile strength of 4.4 GPa as an adhesive portion is “Treka 2255S-25” having a tensile strength of 6 GPa. Clearly exceeded the complex using "." The difference in shear breaking force was 10 MPa or more. From this result, under the condition that the strong adhesion between the adhesive and the adherend (here A7075 aluminum alloy) is ensured by the co-cure method, the surface is higher than the CFRP prepreg based on carbon fiber having high tensile strength. It was revealed that the CFRP prepreg, which has irregularities on the surface and the surface performance is not good, exhibits higher adhesion performance. That is, by using a CFRP prepreg classified as a low-grade product in the bonded portion, it was possible to achieve stronger adhesion to the adherend than a CFRP prepreg classified as a high-grade product. However, these effects disappeared at 150 ° C. Since this was not the case with the bonded metal alloy pieces of NAT treatment, the difference in linear expansion coefficient may have an influence on the fracture mechanism.

[Experimental Example 17] (Creation of CFRP piece)
A CFRP prepreg “Trekka 2255S-25” having a thickness of 0.2 mm based on a high-strength carbon fiber having a tensile strength of 6 GPa was prepared, and a large number of 220 mm × 220 mm square pieces (thickness 0.2 mm) were cut out therefrom. . Also, a 0.2 mm thick CFRP prepreg “Pyrofil TR3523M” based on carbon fiber having a tensile strength of 4.4 GPa lower than the former is prepared, and a 220 mm × 220 mm square piece (thickness 0.2 mm) is prepared from this. A large number were cut out. A firing jig (FIG. 21) having the same basic structure as that of the firing jig used in Experimental Examples 14 and 15 but different in size is used to produce a CFRP plate made of a laminate of these CFRP prepregs. When the mold body 2 and the mold bottom plate 5 are combined, a mold recess is formed by the side wall of the mold body 2 and the upper surface of the mold bottom plate 5. A release film 17 having a thickness of 0.05 mm was laid so as to cover the mold recess.

  On the release film 17, 12 pieces of “Treka 2255S-25” pieces of 220 mm × 220 mm that had been cut were laminated. Further, three “Pyrofil TR3523M” pieces were laminated on this “Torayca 2255S-25” piece. A laminate of these 15 CFRP prepregs is shown as a CFRP prepreg laminate 22 in the figure. A release film 14 was laid so as to cover the CFRP prepreg laminate 22.

  A PTFE block 15 was placed on the release film 14, and a 10 kg weight 18 made of iron was placed on the block 15 and placed in a large autoclave. The lid of the autoclave was closed and the internal temperature was adjusted to about 80 ° C., and then the internal pressure was reduced to 10 mmHg or less with a vacuum pump. After heating at this temperature for 10 minutes, the temperature was raised and when it reached 135 ° C., air was introduced to return to normal pressure. Then, it heated at 135 degreeC for 40 minutes, and raised the temperature to 165 degreeC after that, and heated for 30 minutes, adjusting so that it might be around 165 degreeC. Thereafter, the heating was stopped and the mixture was allowed to cool for 30 minutes. The autoclave was opened and the firing jig 1 was disassembled to obtain a CFRP plate (cured product of the CFRP prepreg laminate 22). The CFRP plate was cut with a high-pressure water cutter to produce a large number of CFRP pieces of 45 mm × 15 mm and a thickness of 3 mm. The same process was repeated to produce a large number of CFRP pieces.

  The end portion 5 mm of the “Pyrofil TR3523M” surface of the CFRP piece thus produced was firmly polished 10 times with a 120th polishing paper defined by JIS R6252 to roughen the surface. Next, an aqueous solution (60 ° C.) containing 7.5% of an aluminum alloy degreasing agent “NE-6” is prepared in a tank provided with an ultrasonic wave transmitting end, and the surface is roughened by applying ultrasonic waves thereto. The CFRP piece was immersed for 5 minutes. Thereafter, this CFRP piece was washed with water and dried in a hot air dryer set at 80 ° C. for 15 minutes.

[Experiment 18] (Creation of CFRP piece)
A CFRP piece consisting of only the “Torayca 2255S-25” piece was prepared in the same manner as in Experimental Example 17. That is, in Experimental Example 17, 12 “Torayca 2255S-25” pieces and 3 “Pyrofil TR3523M” pieces were laminated, but in this Experimental Example, 15 “Torayca 2255S-25” pieces were laminated to form a CFRP plate. Obtained. Furthermore, many CFRP pieces were produced from this CFRP plate by the same method as in Experimental Example 17.

  The surface end portion 5 mm of the CFRP piece thus prepared was firmly polished 10 times with a 120th polishing paper defined by JIS R6252 to roughen the surface. Next, an aqueous solution (60 ° C.) containing 7.5% of an aluminum alloy degreasing agent “NE-6” is prepared in a tank provided with an ultrasonic wave transmitting end, and the surface is roughened by applying ultrasonic waves thereto. The CFRP piece was immersed for 5 minutes. Thereafter, this CFRP piece was washed with water and dried in a hot air dryer set at 80 ° C. for 15 minutes.

[Experimental Example 19] (Cobond bonding of CFRP piece and A7075 aluminum alloy piece)
The one-component epoxy adhesive obtained in Experimental Example 13 was applied to the end of 4 mm of the A7075 aluminum alloy piece obtained in Experimental Example 1. Further, the same one-component epoxy adhesive was applied to the roughened portion at the end of the CFRP piece obtained in Experimental Example 17. Similarly, the same one-component epoxy adhesive was applied to the roughened portion at the end of the CFRP piece obtained in Experimental Example 18. Thus, the A7075 aluminum alloy piece which apply | coated the adhesive agent, the CFRP piece obtained in Experimental example 17, and the CFRP piece obtained in Experimental example 18 were put into the desiccator. This desiccator was previously warmed by placing it in a warm air dryer at 67 ° C. for 15 minutes. Next, the inside of the desiccator was depressurized with a vacuum pump, maintained at a low pressure of 10 mmHg or less for about 3 minutes, and then returned to normal pressure. After this decompression / normal pressure return operation (soaking process) was performed a plurality of times, the A7075 aluminum alloy piece, the CFRP piece obtained in Experimental Example 17, and the CFRP piece obtained in Experimental Example 18 were taken out from the desiccator.

The adhesive application region of the A7075 aluminum alloy piece and the adhesive application region of the CFRP piece obtained in Experimental Example 17 were brought into close contact to form a pair of shapes shown in FIG. 19 and fixed with clips. Similarly, the adhesive application region of the A7075 aluminum alloy piece and the adhesive application region of the CFRP piece obtained in Experimental Example 18 were brought into close contact to form a pair having the shape shown in FIG. The adhesion area (shaded portion 13 in FIG. 19) was set to about 0.5 cm ² . These were put into a hot air dryer set at 90 ° C., heated to 135 ° C. and heated for 40 minutes. Then, after heating up to 165 degreeC and heating for 30 minutes, the power supply was turned off and it stood to cool.

  For the A7075 aluminum alloy / CFRP ("Trekka 2255S-25" and "Pyrofil TR3523M") composite obtained in the above-described manner, 7 pairs were pulled and broken using a testing machine after 1 week. The shear breaking strength was measured. These tests were performed at normal temperature, 100 ° C., and 150 ° C. The results (average values of 7 pairs) are shown in Table 2 (Experimental Example 19-1). In addition, the A7075 aluminum alloy / CFRP ("Trekka 2255S-25") composite obtained in the above-described manner was pulled and ruptured 7 weeks later using a testing machine, and shear ruptured. The force was measured. These tests were performed at normal temperature, 100 ° C., and 150 ° C. The results (average value of 7 pairs) are shown in Table 2 (Experimental Example 19-2).

  From this result, in all temperature ranges of normal temperature, 100 ° C., and 150 ° C., the shear breaking force of the composite using “Pyrofil TR3523M” having a tensile strength of 4.4 GPa as an adhesive portion has a tensile strength of 6 GPa. It clearly exceeded the complex using “Torayca 2255S-25”. In particular, the shear breaking strength at normal temperature and 100 ° C. was high. From this result, under the condition that strong adhesion between the adhesive and the adherend (here A7075 aluminum alloy) is ensured by the cobond method, the surface is higher than the CFRP prepreg based on carbon fiber having high tensile strength. It was revealed that the CFRP prepreg, which has irregularities on the surface and the surface performance is not good, exhibits higher adhesion performance. This is the same as the Cocure method.

[Experimental Example 20] (Cobond adhesion between CFRP pieces)
The same one-component epoxy adhesive was applied to the roughened portion at the end of the CFRP piece obtained in Experimental Example 17, and placed in a desiccator. This desiccator was previously warmed by placing it in a warm air dryer at 67 ° C. for 15 minutes. Next, the inside of the desiccator was depressurized with a vacuum pump, maintained at a low pressure of 10 mmHg or less for about 3 minutes, and then returned to normal pressure. After this pressure reduction / normal pressure return operation (soaking process) was performed a plurality of times, the CFRP piece was taken out of the desiccator.

The adhesive application areas of the two CFRP pieces soaked and treated were brought into close contact with each other to form a pair of shapes shown in FIG. 19 and fixed with clips. The adhesion area (shaded portion 13 in FIG. 19) was set to about 0.5 cm ² . These were put into a hot air dryer set at 90 ° C., heated to 135 ° C. and heated for 40 minutes. Then, after heating up to 165 degreeC and heating for 30 minutes, the power supply was turned off and it stood to cool. The composite obtained as described above was subjected to tensile rupture using a tester after one week, and the shear rupture force was measured. These tests were performed at normal temperature, 100 ° C., and 150 ° C. The results (average of 5 pairs) are shown in Table 3 (Experimental example 20).

[Experimental example 21] (Co-bond adhesion between CFRP pieces)
Instead of the CFRP piece obtained in Experimental Example 17, the same experiment as in Experimental Example 20 was performed using the CFRP piece obtained in Experimental Example 18. The results (average of 5 pairs) are shown in Table 3 (Experimental example 21).

  Also from this result, in the temperature range of room temperature and 100 ° C., the shear breaking force of the joined body using “Pyrofil TR3523M” having a tensile strength of 4.4 GPa as an adhesive portion is “Treka 2255S- Clearly exceeded the conjugate using 25 ". The shear breaking strength at room temperature and 100 ° C. was generally higher than 10 MPa. That is, in co-bond bonding between CFRPs, CFRP prepregs, which have surface irregularities and have poor surface performance, have higher bonding performance than CFRP prepregs based on carbon fibers with high tensile strength. It became clear to show. The results at 150 ° C. were almost the same as the data in Table 1 and the adhesive strength value was slightly low, and the difference between the two was almost eliminated. Since these adhesives are CFRP pieces, there is no difference in linear expansion coefficient. The results were somewhat difficult for the inventors to understand.

[Experimental example 22] (Cocure adhesion between CFRPs)
Prepare a CFRP prepreg “Torayca 2255S-25 (manufactured by Toray Industries, Inc.)” with a thickness of 0.2 mm based on a high-strength carbon fiber with a tensile strength of 6 GPa. From this, a rectangular piece of 45 mm × 15 mm (thickness 0.2 mm) ) Was cut out. In addition, a CFRP prepreg “Pyrofil TR3523M (manufactured by Mitsubishi Rayon Co., Ltd.)” having a thickness of 0.2 mm based on carbon fiber having a tensile strength of 4.4 GPa, which is lower than the former, is prepared, and a rectangular piece (45 mm × 15 mm) A number of 0.2 mm thickness) was cut out.

  A bonded body in which CFRPs are bonded to each other by a co-curing method is created using the firing jig 1 shown in FIG. When the mold body 2 and the mold bottom plate 5 are combined, a mold recess is formed by the side wall of the mold body 2 and the upper surface of the mold bottom plate 5. A release film 17 having a thickness of 0.05 mm was laid so as to cover the mold recess. On this release film 17, 12 “Trekka 2255S-25” pieces were laminated, and further 3 “Pyrofil TR3523M” pieces were laminated thereon. A laminate of these 15 CFRP prepregs is shown as CFRP prepreg laminate 11 in the figure. The space between the CFRP prepreg laminate 11 and the side wall of the mold body 2 was filled with a spacer 16 made of polytetrafluoroethylene resin (hereinafter referred to as “PTFE”).

  Next, three “Pyrofil TR3523M” pieces were laminated on the upper surfaces of the CFRP prepreg laminate 11 and the spacer 16. Furthermore, 12 “Treka 2255S-25” pieces were laminated on this “Pyrofil TR3523M” piece. A laminate of these 15 CFRP prepregs is shown as CFRP prepreg laminate 12 in the figure. Here, the left end portion of the lower surface of the “pyrofil TR3523M” piece that is the lowermost layer of the CFRP prepreg laminate 12 shown in FIG. 18 is in contact with the “pyrofil TR3523M” on the upper surface of the CFRP prepreg laminate 11. In order to fill the gap between the CFRP prepreg laminate 12 and the side wall of the mold body 2, a PTFE spacer 13 was installed, and a release film 14 was laid so as to cover them.

  A PTFE block 15 was placed on the release film 14, and a 10 kg weight 18 made of iron was placed on the block 15 and placed in a large autoclave. The lid of the autoclave was closed and the internal temperature was adjusted to about 80 ° C., and then the internal pressure was reduced to 10 mmHg or less with a vacuum pump. After heating at this temperature for 10 minutes, the temperature was raised and when it reached 135 ° C., air was introduced to return to normal pressure. Then, it heated at 135 degreeC for 40 minutes, and raised the temperature to 165 degreeC after that, and heated for 30 minutes, adjusting so that it might be around 165 degreeC. Thereafter, the heating was stopped and the mixture was allowed to cool for 30 minutes. The autoclave was opened and the firing jig 1 was disassembled to obtain a joined body of CFRP (cured product of CFRP prepreg laminate 11) and CFRP (cured product of CFRP prepreg laminate 12). FIG. 19 shows the appearance of the joined body 10. A cured product of “Pyrofil TR3523M” of CFRP11 and a cured product of “Pyrofil TR3523M” of CFRP12 are joined. In this way, a large number of joined bodies 10 were produced.

  About the joined body of CFRP obtained as described above, 5 pairs were pulled and ruptured using a testing machine after one week, and the shear breaking strength was measured. These tests were performed at normal temperature, 100 ° C., and 150 ° C. As a result, the shear breaking strength (average of 5 pairs) was 50.3 MPa at room temperature, 38.8 MPa at 100 ° C., and 16.5 MPa at 150 ° C. There was no significant difference from Experimental Example 20. However, a one-component epoxy adhesive is not used in the production of this joined body. It is the matrix resin of CFRP prepreg that is used for adhesion.

[Experimental Examples 23 to 33] (Co-bond adhesion of CFRP pieces and various metal alloys)
A composite in which various metal alloys and CFRP pieces were bonded by a cobond method was prepared in the same manner as shown in Experimental Example 19-1. In Experimental Example 19-1, an A7075 aluminum alloy piece subjected to the surface treatment of Experimental Example 1 was used as the metal alloy, but in Experimental Examples 23 to 33, the surface treatments of Experimental Examples 2 to 12 were performed, respectively. Metal alloy pieces were used. That is, A5052 aluminum alloy (Experimental example 23), AZ31B magnesium alloy (Experimental example 24), C1100 copper alloy (Experimental example 25), C5191 phosphor bronze alloy (Experimental example 26), KFC copper alloy (Experimental example 27), KLF5 copper Alloy (Experiment 28), “KS40” pure titanium-based titanium alloy (Experiment 29), “KSTi-9” α-β titanium alloy (Experiment 30), SUS304 stainless steel (Experiment 31), SPCC cold They are a rolled steel plate (Experimental Example 32) and an SPHC hot-rolled steel plate (Experimental Example 33). In these composites, the CFRP piece is formed by laminating three “Pyrofil TR3523M” pieces and 12 pieces of “Trekka 2255S-25” pieces thereon, and the end of the bottom “Pyrofil TR3523M” piece. The part is bonded to the surface of various metal alloy pieces via a one-component epoxy adhesive.

  Here, when the thickness of the metal alloy piece is thin, at the time of the tensile fracture test, due to the bending stress, when the metal alloy piece originally breaks (for example, when the thickness of the metal alloy piece is 3 mm like the A7075 aluminum alloy piece) Shear fracture occurs before the time of fracture. Therefore, A5052 aluminum alloy, AZ31B magnesium alloy, C1100 copper alloy, C5191 phosphor bronze alloy, KFC copper alloy, “KS40” pure titanium-based titanium alloy, “KSTi-9” α-β-based titanium with thin metal alloy pieces Regarding the alloy and SUS304 stainless steel, a 1.6 mm thick SPCC cold-rolled steel sheet piece was bonded to the surface opposite to the bonding surface with a one-component epoxy adhesive for reinforcement. In particular, a thin KLF5 copper alloy (thickness 0.4 mm) was reinforced with a 3.2 mm thick SPCC cold-rolled steel sheet piece. FIG. 22 shows the appearance of the composite 10. Various metal alloy pieces 11 and CFRP 12 are joined via an adhesive application region 13. The bottom side of the metal alloy 11 is reinforced by SPCC cold-rolled steel plate pieces 14.

  About the various composites obtained as described above, 5 pairs were each pulled and broken using a testing machine, and the shear breaking strength was measured. These tests were performed at normal temperature and 100 ° C. The results (average values of 5 pairs) are shown in Table 4 (Experimental Examples 23 to 33).

  From the results of Table 4, for all metal alloys except titanium alloys (“KS40” pure titanium-based titanium alloy, “KSTi-9” α-β-based titanium alloy), approximately 50 to 60 MPa at room temperature and 100 ° C. It showed an extremely high shear breaking force of 40-50 MPa. When metal alloys conforming to the three conditions of NAT are bonded with a one-component epoxy adhesive, the shear breaking strength is usually 60 to 70 MPa at room temperature, 50 to 55 MPa at 100 ° C., and 35 to 40 MPa at 150 ° C. Indicates. By using a CFRP prepreg having a low tensile strength in the range used for bonding CFRP, it was possible to approach this value. The composite of titanium alloy and CFRP also showed a shear breaking force of 40 to 45 MPa at room temperature and 38 to 40 MPa at 100 ° C. This is a clearly high adhesive force when compared with the prior art, and showed extremely high heat resistance.

DESCRIPTION OF SYMBOLS 11 ... Metal alloy 12 ... CFRP prepreg laminate 13 ... Adhesion range 22 ... CFRP board 40 ... Metal alloy 41 ... Ceramic layer 42 ... Adhesive hardened material layer

Claims (15)

A CFRP member in which a first CFRP prepreg based on a first PAN-based carbon fiber having a tensile strength of 5 GPa or less and a second CFRP prepreg based on a second PAN-based carbon fiber having a tensile strength higher than 5 GPa are laminated;
A bonded body with an adherend that is CFRP or a metal alloy,
The joined body, wherein the first CFRP prepreg in the CFRP member is mainly used for joining with the adherend. The joined body according to claim 1,
The bonded body according to claim 1, wherein the first PAN-based carbon fiber has a tensile strength of 4.4 GPa or less. A joined body according to claim 2,
The surface of the first PAN-based carbon fiber has one or more grooves with a height difference of 50 nm or more within a length of 20 μm in the carbon fiber direction or within a surface area of 5 × 10 ⁻⁴ mm ² of the surface. The joined body. The joined body according to claim 1 selected from claims 1 to 3,
The adherend is a CFRP adherend that is a laminate of CFRP prepregs,
The CFRP adherend is a laminate of a third CFRP prepreg based on a third PAN-based carbon fiber having a tensile strength of 5 GPa or less and a fourth CFRP prepreg based on a fourth PAN-based carbon fiber having a tensile strength higher than 5 GPa. Yes,
The joined body, wherein the first CFRP prepreg and the third CFRP prepreg are joined by a curing reaction of a matrix resin of the first CFRP prepreg and a matrix resin of the third CFRP prepreg. The joined body according to claim 1 selected from claims 1 to 3,
The adherend is a CFRP adherend that is a laminate of CFRP prepregs,
The CFRP adherend is a laminate of a third CFRP prepreg based on a third PAN-based carbon fiber having a tensile strength of 5 GPa or less and a fourth CFRP prepreg based on a fourth PAN-based carbon fiber having a tensile strength higher than 5 GPa. Yes,
The joined body, wherein the first CFRP prepreg and the third CFRP prepreg are joined together via a one-component epoxy adhesive. The joined body according to claim 1 selected from claims 1 to 3,
The adherend is a metal alloy,
The metal alloy is any one selected from an aluminum alloy, a magnesium alloy, a copper alloy, a titanium alloy, stainless steel, and a steel material,
The surface of the metal alloy has a roughness on the order of microns in which the average length (RSm) of the contour curve element is 0.8 to 10 μm and the maximum height (Rz) is 0.2 to 5 μm, and the roughness In the plane having a degree, ultrafine irregularities with a period of 5 to 500 nm are formed, and the surface layer is a thin layer of metal oxide or metal phosphate,
The joined body, wherein the first CFRP prepreg and the metal alloy are joined together via a one-component epoxy adhesive that has penetrated into the ultra-fine irregularities. The joined body according to claim 6,
The one-component epoxy adhesive is a bisphenol A-type epoxy resin mainly composed of a bisphenol A-type epoxy resin monomer when the total epoxy resin mixture constituting the one-component epoxy adhesive is 100 parts by mass. 60 to 75 parts by mass, a polyfunctional type having 3 or more epoxy groups and 25 to 40 parts by mass of an epoxy resin having an aromatic ring,
In addition, 3 to 6 parts by mass of dicyandiamide powder is added as a curing agent, and 1 to 3 parts by mass of 3- (3,4-dichlorophenyl) -1,1-dimethylurea powder is added as a curing aid. Said joined body characterized by the above-mentioned. The joined body according to claim 7,
The one-component epoxy adhesive is (1) 60 to 75 parts by mass of a bisphenol A type epoxy resin monomer when the total epoxy resin mixture constituting the one-component epoxy adhesive is 100 parts by mass. (2) 0 to 15 parts by mass of a bisphenol A type epoxy resin oligomer, (3) 25 to 40 parts by mass of an epoxy resin having a polyfunctional type having 3 or more epoxy groups and having an aromatic ring Said joined body characterized by the above-mentioned. It is a manufacturing method of the joined object according to claim 4,
Meanwhile, the first CFRP prepreg and the second CFRP prepreg are laminated,
On the other hand, the third CFRP prepreg and the fourth CFRP prepreg are laminated,
And an overall laminating step for bringing a predetermined range of the first CFRP prepreg and the third CFRP prepreg into close contact with each other;
By heating the first CFRP prepreg, the second CFRP prepreg, the third CFRP prepreg, and the fourth CFRP prepreg at the same time after the entire laminating step, the respective matrix resins are cured at a time, whereby the CFRP member and the An overall curing step to integrate the CFRP adherend;
The manufacturing method of the conjugate | zygote characterized by including. It is a manufacturing method of the joined object according to claim 5,
A first curing step in which the first CFRP prepreg and the second CFRP prepreg are laminated and heated to cure the respective matrix resins to create the CFRP member;
A second curing step in which the third CFRP prepreg and the fourth CFRP prepreg are laminated and heated to cure the respective matrix resins to create the CFRP adherend;
A first roughening step of roughening the surface of the first CFRP prepreg of the CFRP member that has undergone the first curing step;
A second roughening step of roughening the third CFRP prepreg surface of the CFRP adherend that has undergone the second curing step;
A first application step of applying a one-component epoxy adhesive to the roughened range of the CFRP member that has undergone the first roughening step;
A second coating step of applying a one-component epoxy adhesive to the roughened range of the CFRP adherend that has undergone the second roughening step;
The CFRP member and the CFRP adherend are bonded to each other by heating the adhesive application regions of the CFRP member that has undergone the first application step and the CFRP adherend that has undergone the second application step. An adhesion process,
The manufacturing method characterized by including. It is a manufacturing method of the joined object according to claim 10,
The CFRP member that has undergone the first application step is sealed in a sealed container, and further includes a first soaking step that pressurizes the inside of the sealed container once after depressurization,
Sealing the CFRP adherend that has undergone the second application step in a sealed container, and further includes a second soaking step that pressurizes the sealed container after depressurization.
The said manufacturing method characterized by performing the said adhesion process after the said 1st soaking process and the said 2nd soaking process. It is a manufacturing method of the joined object according to claim 6,
On the surface of the metal alloy, a roughness on the order of microns having an average length (RSm) of the contour curve element of 0.8 to 10 μm and a maximum height (Rz) of 0.2 to 5 μm is generated, and the roughness A surface treatment step of performing surface treatment for forming ultrafine irregularities with a period of 5 to 500 nm in a plane having a degree and forming a surface layer as a thin layer of metal oxide or metal phosphate;
An application step of applying a one-component epoxy adhesive to the surface of the metal alloy that has undergone the surface treatment step;
A laminating step of laminating the first CFRP prepreg and the second CFRP prepreg and bringing the first CFRP prepreg and the adhesive application region of the metal alloy that has undergone the applying step into close contact with each other;
A curing step of integrating the CFRP member and the metal alloy by simultaneously heating the first CFRP prepreg, the second CFRP prepreg, and the one-component epoxy adhesive after the lamination step;
The manufacturing method of the conjugate | zygote characterized by including. It is a manufacturing method of the joined object according to claim 12,
The metal alloy that has undergone the coating step is sealed in a sealed container, and further includes a soaking step in which the inside of the sealed container is once pressurized after being decompressed,
The said manufacturing method characterized by performing the said lamination process after the said impregnation process. It is a manufacturing method of the joined object according to claim 6,
A first curing step in which the first CFRP prepreg and the second CFRP prepreg are laminated and heated to cure the respective matrix resins to create the CFRP member;
A first roughening step of roughening the surface of the first CFRP prepreg of the CFRP member that has undergone the first curing step;
A first application step of applying a one-component epoxy adhesive to the roughened range of the CFRP member that has undergone the first roughening step;
On the surface of the metal alloy, a roughness on the order of microns having an average length (RSm) of the contour curve element of 0.8 to 10 μm and a maximum height (Rz) of 0.2 to 5 μm is generated, and the roughness A surface treatment step of performing surface treatment for forming ultrafine irregularities with a period of 5 to 500 nm in a plane having a degree and forming a surface layer as a thin layer of metal oxide or metal phosphate;
A second application step of applying a one-component epoxy adhesive to the surface of the metal alloy that has undergone the surface treatment step;
An adhesion step of bonding the CFRP member and the metal alloy by closely contacting and heating the adhesive application regions of the CFRP member having undergone the first application step and the metal alloy having undergone the second application step; ,
The manufacturing method characterized by including. It is a manufacturing method of the joined object according to claim 14,
The CFRP member that has undergone the first application step is sealed in a sealed container, and further includes a first soaking step that pressurizes the inside of the sealed container once after depressurization,
The metal alloy that has undergone the second application step is further sealed in a sealed container, and further includes a second soaking step in which the inside of the sealed container is once pressurized after being decompressed,
The said manufacturing method characterized by performing the said adhesion process after the said 1st soaking process and the said 2nd soaking process.