JP2006241308A - Fiber-reinforced composite material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a resin transfer molding (RTM) fiber-reinforced composite material which has high compression strength after applying impact and excellent injury visibility. <P>SOLUTION: This RTM fiber-reinforced composite material prepared by injection-impregnating an epoxy resin composition which comprises a main agent comprising an epoxy resin and a curing agent containing a component capable of curing the epoxy resin and has a cured product tensile elongation of 3 to 10%, when thermally cured at 180°C for 2 hours, into a fiber-reinforced substrate containing carbon fibers or a preform prepared by laminating the fiber-reinforced substrates, is characterized in that a dent depth is ≥0.6 mm, after applying an impact energy of 20J per mm of the thickness of a test piece according to JIS K 7089 (1996) is given to a 4 to 5 mm-thick fiber-reinforced composite material obtained from the cross-laminated preform. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fiber reinforced composite material suitably used for aircraft members, spacecraft members, automobile members, ship members, and the like, and more particularly to a fiber reinforced composite material having excellent damage visibility.

  Conventionally, fiber reinforced composite materials composed of reinforced fibers such as glass fiber, carbon fiber, aramid fiber and thermosetting resins such as unsaturated polyester resin, vinyl ester resin, epoxy resin, phenol resin, cyanate resin, bismaleimide resin, Although it is lightweight, it has excellent mechanical properties and heat resistance such as strength, rigidity, impact resistance, fatigue resistance, and corrosion resistance. It has been applied to many fields. In applications that require particularly high performance, fiber reinforced composite materials using continuous reinforcing fibers are used. Carbon fibers are used as reinforcing fibers, thermosetting resins are used as matrix resins, and epoxy resins are especially used. Yes.

  When fiber reinforced composite materials are used as structural materials, compression properties and impact resistance are important. A particularly important physical property regarding both of these properties is post-impact compressive strength (hereinafter referred to as CAI). This is a phenomenon in which the compressive strength decreases due to delamination between the layers of the composite material even when there is no apparent damage due to the impact on the member due to the impact of a tool fall, pebbles, etc. Therefore, it is a characteristic that is particularly emphasized.

  In order to improve CAI, it is effective to increase the toughness of the resin and suppress internal damage such as delamination when subjected to impact, and it is effective to add a thermoplastic resin component as a component to increase toughness Therefore, in the prepreg method, which is one of the molding methods for fiber-reinforced composite materials, this problem has been solved by a method of laminating and curing prepregs provided with a thermoplastic resin. Various proposals have been made on the form of the thermoplastic resin applied to the prepreg as shown in Patent Documents 1 to 12.

  By the way, as a trend of recent fiber reinforced composite materials, resin transfer molding (resin transfer molding) in which a reinforced fiber base material is directly impregnated with a liquid thermosetting resin without passing through an intermediate such as a prepreg and cured. (Hereinafter abbreviated as RTM). Since the RTM method has the potential to reduce the molding cost, its application has been expanded. On the other hand, in the RTM method, there is a restriction on the resin design that the resin must be in a low-viscosity liquid when injected, and therefore the CAI generally tends to be lower than that in the prepreg method. A technique for greatly improving the CAI has been desired.

  Therefore, in the RTM method as well as the prepreg method, a method using a thermoplastic resin can be considered in order to increase the impact resistance. However, if the thermoplastic resin component is added directly to the injection resin, the viscosity is significantly increased, and the process Does not hold. Therefore, a method for applying a thermoplastic component to the substrate side is disclosed.

  As one of them, Patent Document 13 discloses a method in which at least a part of the surface of a reinforcing fiber base is coated with a thermoplastic resin having a glass transition temperature of 100 ° C. or higher, preferably 150 ° C. or higher. Examples of the coating method include a solution coating method and a melt coating method. Furthermore, Patent Document 14 discloses a method of applying a fiber made of a thermoplastic resin onto a substrate as a toughening component.

  In the RTM method, a small amount of binder (softened by heating) is added to the reinforcing fiber base in order to stabilize the form of the reinforcing fiber base and improve the processability and mechanical properties of the molded product prior to resin injection / impregnation. In many cases, a pre-forming step is included in which the resin is applied and shaped by applying heat and pressure. As binders, Patent Documents 15 and 16 disclose thermoplastic resins, Patent Document 17 discloses thermosetting resins not containing a curing agent, and Patent Document 18 discloses curable thermosetting resins.

  From the above, it is expected that both the effects of shaping and toughening can be realized by using an appropriate thermoplastic resin as the binder. However, in applications that require heat resistance, such as aircraft parts, if the composite material contains a thermoplastic resin with a low glass transition temperature or low melting point, the mechanical properties at high temperatures decrease, so the glass transition temperature or melting point is high. It is necessary to select a thermoplastic resin that is sufficiently higher than 100 ° C., which is the highest operating temperature of the aircraft, and preferably 150 ° C. or higher. However, when such a thermoplastic resin is used, the processing temperature in preforming becomes high, which is an economically disadvantageous process.

  As one proposal for enabling a preform to be processed at a relatively low temperature using a thermoplastic resin having a glass transition point or a high melting point, Patent Document 19 discloses a thermoplastic resin having a high glass transition temperature and curability. The binder composition which consists of the thermosetting resin of this, and softens at comparatively low temperature is disclosed. This method is an excellent method in that it uses both a high glass transition temperature thermoplastic resin as a toughening agent and economically advantageous processing at a relatively low temperature. Since the thermosetting resin was contained as a component, there was an unpreferable point in practical use. One of them is a shelf life problem that the softening temperature of the binder gradually increases during storage and eventually becomes unusable. The other is that it is difficult to use a preparation method with good productivity without using a solvent such as an extruder and a kneader because the binder composition cannot be produced at a high temperature.

  As described above, various methods have been proposed as methods for improving the CAI of a fiber-reinforced composite material by the RTM method by imparting a toughening material such as a thermoplastic resin. Furthermore, the improvement of CAI itself has not always been sufficient. Furthermore, none of the problems and solutions from the viewpoint of making only appearance damage conspicuous (that is, improving damage visibility) while keeping CAI high.

Among aircraft structural materials, the application of fiber reinforced composite materials to so-called primary structural materials such as main wings, tail wings, and fuselage is advancing. Primary structural materials are often made from unidirectional materials that have the reinforcing fibers aligned substantially in one direction from the standpoints of increasing mechanical properties and volume content of the reinforcing fibers and making it possible to reduce the weight of the member. . By using a base material in which reinforcing fibers are substantially aligned in one direction, a unidirectional material can be formed by the RTM method. In this case, however, CAI is particularly often a design constraint. For these reasons, it can be said that most primary structural materials are based on the prepreg method, and those based on the RTM method are extremely limited.
European Patent No. 0366979A2 Specification European Patent No. 0495518A1 Japanese Patent Laid-Open No. 01-320146 Japanese Patent Laid-Open No. 05-287091 European Patent No. 0274899A2 European Patent No. 0707032A1 US Pat. No. 4,874,661 European Patent No. 0488389A2 Japanese Patent Laid-Open No. 08-176322 Japanese Patent Laid-Open No. 02-032843 European Patent No. 0657492A1 Japanese Patent Application Laid-Open No. 08-048796 Japanese Patent Application Laid-Open No. 08-300395 International Publication No. 2000 / 58083A1 Pamphlet U.S. Pat. No. 4,470,862 US Pat. No. 4,998,469 US Pat. No. 4,992,228 International Publication No. 1994 / 26492A1 Pamphlet International Publication No. 1998 / 50211A1 Pamphlet

  In view of the background of such prior art, the present invention provides a fiber-reinforced composite material that is very excellent in damage visibility, has high post-impact compressive strength, and is particularly excellent as a member of an aircraft primary structure or the like. Is.

The present inventors have focused on the fact that, in an actual aircraft, the most frequent method for confirming damage to members is visual confirmation, and improving the visibility of damage leads to early detection of strength reduction. In the RTM molded member which is difficult to improve, it has been found that damage visibility can be improved by setting the resin elongation to an appropriate range, and further the strength after impact can be improved.
That is, the fiber-reinforced composite material of the present invention is composed of a main agent containing an epoxy resin and a curing agent containing a component capable of curing the epoxy resin, and a tensile elongation of a cured product obtained by thermosetting at 180 ° C. for 2 hours is 3 to 10. % Of a resin-transfer-molded molded fiber-reinforced composite material that is injected and impregnated into a reinforcing fiber substrate containing carbon fiber or a preform formed by laminating the reinforcing fiber substrate and heat-cured. With respect to the fiber reinforced composite material having a thickness of 4 to 5 mm obtained from the preform that is cross-laminated, after applying an impact energy of 20 J per 1 mm thickness of the test piece according to JIS K 7089 (1996) The dent depth is 0.6 mm or more.

  The fiber reinforced composite material of the present invention has a large dent (dent) depth when given a certain or higher impact energy, and is very excellent in damage visibility, and also has a residual compressive strength at the CAI. Therefore, it can be suitably used for structural members such as aircraft members, spacecraft members, automobile members, and ship members.

  First, the fiber reinforced composite material of the present invention comprises a reinforcing fiber base material composed of carbon fibers or an epoxy resin composition comprising a curing agent containing a main agent containing an epoxy resin and a component capable of curing the epoxy resin, or the reinforcing fiber base material. The fiber reinforced composite material having a thickness of 4 to 5 mm obtained by injection impregnation into a laminated preform and obtained from the cross-laminated preform is 20 J per mm of a test piece according to JIS K 7089 (1996). The dent depth after applying the impact energy is 0.6 mm or more, more preferably in the range of 0.8 to 3 mm. When the dent depth is less than 0.6 mm, the visibility of the damaged portion is remarkably deteriorated, and when the dent depth exceeds 3 mm, the residual compressive strength may be lowered.

  Further, the CAI after applying an impact energy of 20 J per 1 mm thickness of the test piece to the fiber reinforced composite material according to JIS K 7089 (1996) is preferably 160 MPa or more, and more preferably 180 MPa or more. When CAI is lower than the above range, the strength may be insufficient, and in particular, it cannot be used for structural members such as aircraft.

  In the present invention, the epoxy resin constituting the main agent is a so-called polyfunctional epoxy resin having two or more epoxy groups in one molecule, and is used alone or in a mixture of plural kinds. Such epoxy resins include bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, tetrabromobisphenol A diglycidyl ether, bisphenol AD diglycidyl ether, 2,2 ′, 6,6′-tetramethyl-4,4′-. Biphenol diglycidyl ether, N, N, O-triglycidyl-m-aminophenol, N, N, O-triglycidyl-p-aminophenol, N, N, O-triglycidyl-4-amino-3-methylphenol N, N-diglycidylaniline, N, N-diglycidyl-o-toluidine, N, N, N ′, N′-tetraglycidyl-4,4′-methylenedianiline, N, N, N ′, N ′ -Tetraglycidyl-2,2'-diethyl-4,4'-methylenedianiline, N, N, ', N'-tetraglycidyl-m-xylylenediamine, 1,3-bis (diglycidylaminomethyl) cyclohexane, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, hexamethylene glycol diglycidyl ether, neopentyl glycol di Glycidyl ether, sorbitol polyglycidyl ether, glycerol polyglycidyl ether, diglycerol polyglycidyl ether, phthalic acid diglycidyl ester, terephthalic acid diglycidyl ester, vinylcyclohexene diepoxide, 3,4-epoxycyclohexanecarboxylic acid-3,4-epoxy Diglycidyl of cyclohexylmethyl, bis-3,4-epoxycyclohexylmethyl adipate, 1,6-dihydroxynaphthalene Ether, diglycidyl ether of 9,9-bis (4-hydroxyphenyl) fluorene, triglycidyl ether of tris (p-hydroxyphenyl) methane, tetraglycidyl ether of tetrakis (p-hydroxyphenyl) ethane, phenol novolac glycidyl ether, Cresol novolac glycidyl ether, glycidyl ether of condensate of phenol and dicyclopentadiene, glycidyl ether of phenol aralkyl resin, triglycidyl isocyanurate, N-glycidyl phthalimide, 5-ethyl-1,3-diglycidyl-5-methylhydantoin, 1 , 3-Diglycidyl-5,5-dimethylhydantoin, oxazolide obtained by addition of bisphenol A diglycidyl ether and tolylene isocyanate Type epoxy resin, phenol aralkyl type epoxy and the like can be used.

  Components that can cure the epoxy resin that constitutes the curing agent undergo a quantitative reaction such as aliphatic polyamines, aromatic polyamines, dicyandiamide, polycarboxylic acids, polycarboxylic acid hydrazides, acid anhydrides, polymercaptans, polyphenols, etc. There are curing agents and curing agents that act catalytically, such as imidazoles, Lewis acid complexes, and onium salts. When a curing agent that performs a stoichiometric reaction is used, a curing accelerator such as imidazole, Lewis acid complex, onium salt, phosphine, and the like may be blended. In particular, when the purpose is to produce a structural material having excellent heat resistance, an aromatic amine is most suitable as a curing agent.

  In addition, plasticizers, dyes, organic pigments and inorganic fillers, polymer compounds, antioxidants, ultraviolet absorbers, coupling agents, surfactants, and the like are appropriately added as other components to the main agent and the curing agent. You can also.

  In this invention, the hardened | cured material of an epoxy resin composition is arbitrary time of the range of 0.5 to 10 hours at the arbitrary temperature of the range of 50-200 degreeC according to the activity of the hardening | curing agent which comprises this epoxy resin composition. Obtained by heat curing. The heating condition may be one stage or may be a multistage condition in which a plurality of heating conditions are combined.

  When the curing agent is an aromatic amine, a desired cured product can be obtained by heat curing at 180 ° C. for 2 hours.

  In the present invention, in order to improve the impact resistance and the like of the fiber reinforced composite material, the tensile elongation of the cured product of the epoxy resin composition is cut out from a small 1 (1/2) type test piece in accordance with JIS K 7113 (1981). Measured to be 3 to 10%, preferably 4 to 8%. The present inventors have found that when the tensile elongation is less than 3%, the dent depth when an impact is applied to the obtained fiber reinforced composite material is reduced, damage visibility is lowered, and CAI is also lowered. It was. On the other hand, if it exceeds 10%, the impact resistance is good, but in most cases, the phenomenon that the flexural modulus decreases is caused. Therefore, the compression characteristics of the fiber reinforced composite material are lowered, and the CAI tends to be lowered.

  In order to obtain the necessary tensile elongation, it is effective to add 40 parts by weight or more of an epoxy resin having an epoxy equivalent of 150 g / eq or more in 100 parts by weight of the epoxy resin constituting the main agent, and in particular, an epoxy equivalent of 250 g / eq or more. When 5 parts by weight or more of the epoxy resin is blended, the effect is high. Examples of such epoxy resins include bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, glycidyl ether of a condensation product of phenol novolac and dicyclopentadiene, oxazolidone type epoxy resin obtained by addition of bisphenol A diglycidyl ether and tolylene isocyanate, A phenol aralkyl type epoxy resin etc. can be mentioned.

  Specific examples of the carbon fiber used in the present invention include acrylic, pitch, and rayon carbon fibers, with acrylic carbon fibers having high tensile strength being particularly preferred. As the form of the carbon fiber, twisted yarn, untwisted yarn, untwisted yarn or the like can be used. However, untwisted yarn or untwisted yarn is preferable because the balance between moldability and strength characteristics of the fiber reinforced composite material is good.

  The elastic modulus of the carbon fiber is preferably in the range of 200 GPa to 400 GPa from the viewpoint of the characteristics and weight of the molded member. If the elastic modulus is lower than this range, the rigidity of the member may be insufficient and weight reduction may be insufficient. Conversely, if the elastic modulus is higher than this range, the strength of the carbon fiber generally tends to decrease. Preferably, the elastic modulus is in the range of 250 GPa to 370 GPa, more preferably in the range of 290 GPa to 350 GPa.

  In the present invention, the reinforcing fiber base material is composed of carbon fibers alone or in combination with glass fibers, chemical fibers, and the like, and those in which the fiber directions are aligned substantially in the same direction, woven fabrics, knits, blades, mats, etc. In particular, a so-called unidirectional fabric in which carbon fibers are substantially oriented in one direction and fixed with glass fibers or chemical fibers is a fiber-reinforced composite material having high mechanical properties and a high volume content of reinforcing fibers. Since it is obtained, it is preferable. Moreover, the improvement effect of damage visibility by this invention is acquired notably especially in the case of a unidirectional fabric.

  Examples of unidirectional woven fabrics include strands made of carbon fibers arranged in parallel to each other in one direction, and weft fibers made of glass fibers or chemical fibers orthogonal to each other to form a plain weave structure, carbon It consists of a warp yarn composed of strands of fibers, an auxiliary warp yarn of a fiber bundle composed of glass fibers or chemical fibers arranged in parallel to this, and a weft yarn composed of glass fibers or chemical fibers arranged so as to be orthogonal thereto. There are non-crimp fabrics in which carbon fiber strands are integrally held to form a fabric by crossing the auxiliary warp yarn and the weft yarn.

  In the present invention, one in which a binder composition made of a thermoplastic resin or a thermosetting resin is attached to one side or both sides of a reinforcing fiber can be used. In particular, when a binder composition made of a thermoplastic resin is attached, it is possible to disperse a high-toughness thermoplastic resin in an epoxy resin composition with poor toughness, which occurs when an impact is applied to a fiber-reinforced composite material. It is preferable because the propagation of cracks inside, particularly between layers, can be suppressed and strength reduction can be prevented.

  Specific examples of the thermoplastic resin constituting the binder composition include polyimide, polyetherimide, polysulfone, polyethersulfone, polyamide, polyamideimide, polyarylene oxide, polyetherketone, and polyetherethersulfone. A resin belonging to the above is preferably used.

  It is preferable that a binder composition comprising a thermoplastic resin is mixed with an appropriate plasticizer component to adjust the glass transition temperature as a binder to an appropriate range, specifically 50 to 70 ° C. Here, for the plasticizer component, it is necessary to select a compound that can react with the epoxy resin composition. As such a plasticizer component, an epoxy resin is particularly preferable. The epoxy resin used as the plasticizer component is not particularly limited. Specific examples include bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, tetrabromobisphenol A diglycidyl ether, bisphenol AD diglycidyl ether, 2,2 ′, 6,6. '-Tetramethyl-4,4'-biphenol diglycidyl ether, N, N, O-triglycidyl-m-aminophenol, N, N, O-triglycidyl-p-aminophenol, N, N, O-tri Glycidyl-4-amino-3-methylphenol, N, N-diglycidylaniline, N, N-diglycidyl-o-toluidine, N, N, N ′, N′-tetraglycidyl-4,4′-methylenedianiline N, N, N ′, N′-tetraglycidyl-2,2′-diethyl 4,4'-methylenedianiline, N, N, N ', N'-tetraglycidyl-m-xylylenediamine, 1,3-bis (diglycidylaminomethyl) cyclohexane, ethylene glycol diglycidyl ether, propylene glycol di Glycidyl ether, hexamethylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, sorbitol polyglycidyl ether, glycerol polyglycidyl ether, diglycerol polyglycidyl ether, phthalic acid diglycidyl ester, terephthalic acid diglycidyl ester, vinylcyclohexene diepoxide, 3,4-epoxycyclohexanecarboxylic acid-3,4-epoxycyclohexylmethyl, bis-3,4-epoxycyclohexylmethyl adipate, 1 Diglycidyl ether of 6-dihydroxynaphthalene, diglycidyl ether of 9,9-bis (4-hydroxyphenyl) fluorene, triglycidyl ether of tris (p-hydroxyphenyl) methane, tetraglycidyl of tetrakis (p-hydroxyphenyl) ethane Ether, phenol novolac glycidyl ether, cresol novolac glycidyl ether, glycidyl ether of condensate of phenol and dicyclopentadiene, triglycidyl isocyanurate, N-glycidyl phthalimide, 5-ethyl-1,3-diglycidyl-5-methylhydantoin, 1 , 3-Diglycidyl-5,5-dimethylhydantoin, bisphenol A diglycidyl ether and tolylene isocyanate are added to obtain an oxazolidone type ester Poxy resin and phenol aralkyl type epoxy can be mentioned.

  As the plasticizer component, polyphenol, polyamine, polycarboxylic acid, polycarboxylic anhydride, polyacrylate, sulfonamide and the like are preferably used other than the epoxy resin.

    For example, examples of polyphenols include 4-tert-butylcatechol, 2,5-di-tert-butylhydroquinone, bisphenol obtained by condensation of one molecule of limonene and two molecules of phenol.

  An example of the polyamine is diethyltoluenediamine.

  An example of the polycarboxylic acid is 5-tert-butylisophthalic acid.

  Examples of the polycarboxylic acid anhydride include methyl phthalic acid anhydride, methyl hexahydrophthalic acid anhydride, and nadic acid anhydride.

  An example of the polyacrylate is tris (2-acryloyloxyethyl) isocyanurate.

  Examples of the sulfonamide include benzenesulfonamide and toluenesulfonamide.

  Such reactive plasticizers can be used in combination of a plurality of types. In that case, it is necessary to select a similar compound, for example, an epoxy resin, a combination that does not react with each other, or an epoxy resin and a polyacrylate. Combinations that react easily such as epoxy resins and polyamines are not preferred because the reaction proceeds and the glass transition temperature of the binder rises when stored for a long period of time, making it unusable as a binder.

The amount of binder composition applied to the surface of the reinforcing fiber base material is preferably attached at least one side of 5 to 50 g / m ² basis weight, further preferably ranges from 10~35g / m ^2. If the basis weight is less than the above range, the effect of fixing the form and increasing the toughness is small, and if the basis weight is large, the impregnation property of the epoxy resin composition that is injected and impregnated into the preform formed by laminating the reinforcing fiber base becomes poor. Such disadvantages may occur.

In the present invention, the fiber reinforced composite material preferably has a carbon fiber volume content of 50 to 65%, more preferably 53 to 60%. If the volume content is less than the above range, the weight of the fiber reinforced composite material becomes heavy, and the strength tends to decrease due to the effect of stress concentration. It is not preferable because defective portions such as unimpregnated portions and voids are generated in the reinforced composite material so much that physical properties may be deteriorated.

As a preferable molding method in the present invention, an epoxy resin composition is injected at an arbitrary temperature of 25 to 90 ° C. into a preform composed of a reinforcing fiber base disposed in a mold. Therefore, the initial viscosity of the epoxy resin composition is preferably 500 mPa · s or less at an arbitrary temperature of 25 to 90 ° C. More preferably, the initial viscosity is 300 mPa · s or less. When the initial viscosity is higher than the above range, the impregnation property of the epoxy resin composition may be insufficient.

  In the present invention, the mold used for the RTM molding may be a closed mold made of a rigid body, and a method using a rigid open mold and a flexible film (bag) is also possible. In the latter case, the reinforcing fiber base is placed between the rigid open mold and the flexible film.

  As the rigid material, various existing materials such as metal (steel, aluminum, etc.), FRP, wood, and plaster are used. Nylon, fluorine resin, silicone resin, or the like is used as the material for the flexible film.

  When a rigid closed mold is used, it is usually performed by pressurizing and clamping and then injecting the epoxy resin composition under pressure. At this time, it is also possible to provide a suction port separately from the injection port and connect it to a vacuum pump for suction. It is also possible to inject the epoxy resin composition only at atmospheric pressure without performing any special pressurizing means.

In the case of using a rigid open mold and a flexible film, suction and injection by atmospheric pressure are usually used. In order to achieve good impregnation by injection at atmospheric pressure, it is effective to use a resin diffusion medium. Furthermore, it is also preferable to apply a gel coat to the rigid surface prior to installation of the reinforcing fiber substrate or preform.
After the installation of the reinforcing fiber base or preform is completed, mold clamping or bagging is performed, and then thermosetting resin is injected, and then heat curing is performed. The temperature of the mold at the time of heat curing is usually selected to be higher than the mold temperature at the time of injection of the liquid thermosetting resin. The mold temperature during heat curing is preferably 80 to 180 ° C. The heat curing time is preferably 1 to 20 hours. After the heat curing is completed, the mold is removed and the fiber reinforced composite material is taken out. Thereafter, post-curing may be performed in which the obtained fiber-reinforced composite material is heated at a temperature higher than the curing temperature. The post-curing temperature is preferably 150 to 200 ° C., and the time is preferably 1 to 4 hours.

  The fiber-reinforced composite material of the present invention is light because the volume content of the reinforcing fiber is high, and is excellent in impact resistance, particularly compressive strength after impact, and is highly visible when it is damaged by applying strong damage energy. Because it is good, quality inspections do not miss damaged parts, fuselage, main wing, tail wing, moving blade, fairing, cowl, door, seat and interior materials such as aircraft parts, motor case and main wing spacecraft members, It is suitably used for many structural materials such as artificial satellite members such as structures and antennas, outer members, automobile members such as chassis, aerodynamic members and seats, railway vehicle members such as structures and seats, and ship members such as hulls and seats. it can.

  Hereinafter, the present invention will be described more specifically with reference to examples. The unit “part” of the composition ratio means part by weight unless otherwise specified.

<Method for measuring tensile elongation of cured resin>
The epoxy resin composition obtained in the example was poured into a predetermined mold, heated from room temperature to 130 ° C. by 1.5 ° C. per minute in a hot air oven, then held at 130 ° C. for 2 hours, Next, the temperature was raised to 180 ° C. by 1.5 ° C. per minute and then held at 180 ° C. for 2 hours to produce a 2 mm thick cured plate.

  From the obtained cured plate, a small 1 (1/2) type test piece was cut out according to JIS K 7113 (1981), and the tensile elongation was measured.

<Manufacture of carbon fiber fabrics>
The carbon fiber fabric used in the examples was produced as follows.

Carbon fiber T800S-24K-10C (manufactured by Toray Industries, Inc.) was used as warp yarns, and glass fibers ECE225 1/0 1Z (manufactured by Nittobo Co., Ltd.) were used as weft yarns so that the carbon fibers were substantially arranged in one direction. A plain weave fabric was prepared. The warp yarn density was 7.2 yarns / 25 mm, and the weft yarn density was 7.5 yarns / 25 mm. The carbon fiber basis weight of the woven fabric was 190 g / m ² .
<Manufacture of binder composition>
The binder composition used in the examples was prepared as follows.
60 parts of polyethersulfone (“Sumika Excel” PES5003P, manufactured by Sumitomo Chemical Co., Ltd.), 4 parts of triglycidyl isocyanurate (TEPIC-P, manufactured by Nissan Chemical Co., Ltd.), liquid bisphenol F type epoxy resin (“Epicoat” 806) , Japan Epoxy Resin Co., Ltd.) 23 parts and Phenol Aralkyl Type Epoxy Resin (NC-3000, Nippon Kayaku Co., Ltd.) 13 parts were kneaded at 210 ° C. with a twin screw extruder. The binder composition having an average particle diameter of 100 μm (equivalent sphere diameter) was obtained by freeze pulverization.

<Dent depth of fiber reinforced composite material and method for producing CAI specimen>
The fiber reinforced composite materials used in the examples below were produced by the RTM molding method.
A reinforced fiber base material having a carbon fiber longitudinal direction of 0 ° and repeated three times based on [+ 45 ° / 0 ° / −45 ° / 90 °] is laminated symmetrically to prepare a preform.

  The resulting preform is injected and impregnated with an epoxy resin composition at 80 ° C., and then heated to 130 ° C. at 1.5 ° C. per minute and pre-cured at 130 ° C. for 2 hours. After removing the precured product from the RTM mold, it was cured in a hot air oven at 180 ° C. for 2 hours to obtain a test specimen.

<Measurement of dent depth and CAI of fiber reinforced composite material>
From the specimen obtained by the above method, a rectangular specimen having a length of 150 mm and a width of 100 mm was cut out with the longitudinal direction of the specimen being a carbon fiber orientation angle of 0 °, and the thickness of the specimen was measured according to JIS K 7089 (1996) at the center of the specimen. After applying a falling weight impact of 20 J per 1 mm, the largest dent depth of the portions dented by the impact was obtained with a micrometer, and the residual compressive strength was measured according to JIS K 7089 (1996).

<Example 1>
An epoxy resin composition was obtained by the following formulation.
・ "Araldite" MY-721 (epoxy resin manufactured by Huntsman Advanced Materials Co., Ltd.)
: 30 parts AK-601 (Nippon Kayaku Co., Ltd. epoxy resin)
: 20 parts "Epicoat" 825 (epoxy resin manufactured by Japan Epoxy Resin Co., Ltd.)
: 20 parts "Epiclon" HP7200L (Epoxy resin manufactured by Dainippon Ink & Chemicals, Inc.)
: 30 parts "Epicure" W (Aromatic amine manufactured by Japan Epoxy Resin Co., Ltd.)
: 18 parts ・ SumiCure S (Aromatic amine manufactured by Sumitomo Chemical Co., Ltd.)
: 7 parts, 3,3'-DAS (Aromatic amine manufactured by Mitsui Chemicals, Inc.)
: 7 parts · TBC (t-butylcatechol (curing catalyst) manufactured by Ube Industries, Ltd.)
1 part The viscosity of this epoxy resin composition at 80 ° C. was measured with an E-type viscometer, and found to be 190 mPa · s.

  Further, a cured product was produced by the above method for this epoxy resin composition, and the tensile elongation was measured. As a result, it was 5.4%.

Furthermore, using this epoxy resin composition, a fiber-reinforced composite material having a volume content of reinforcing fibers of 58% was obtained by the above method. As a result of applying an impact energy of 20 J per 1 mm thickness of the test piece according to the above method to the obtained fiber reinforced composite material, the dent depth was 1.1 mm, the visibility of the damaged part was good, and the CAI was as high as 190 MPa. Value.
<Example 2>
An epoxy resin composition was obtained by the following formulation.
・ "Araldite" MY-721 (epoxy resin manufactured by Huntsman Advanced Materials Co., Ltd.)
: 50 parts "Elysis" GE-20 (CVC Specialty Chemicals epoxy resin)
: 20 parts "Epicoat" 807 (epoxy resin manufactured by Japan Epoxy Resin Co., Ltd.)
: 30 parts "Epicure" W (Aromatic amine manufactured by Japan Epoxy Resin Co., Ltd.)
: 21 parts "SumiCure" S (Aromatic amine manufactured by Sumitomo Chemical Co., Ltd.)
: 5
・ 3,3'-DAS (Aromatic amine manufactured by Mitsui Chemicals, Inc.)
: 5 parts · TBC (Ube Industries, Ltd. t-butylcatechol (curing catalyst))
1 part The viscosity of the epoxy resin composition at 80 ° C. was measured with an E-type viscometer, and it was 43 mPa · s.

  Further, a cured product was prepared by the above method for this epoxy resin composition, and the tensile elongation was measured and found to be 5.0%.

Furthermore, the epoxy resin composition and the carbon fiber woven fabric are reinforced with a binder-bonded fiber reinforced by spraying the binder composition with a basis weight of 30 g / m ² and heating to 170 ° C. using a far-red heater. Using the base material, a fiber-reinforced composite material having a volume content of reinforcing fibers of 58% was obtained by the above method. As a result of applying an impact energy of 20 J per 1 mm thickness of the test piece according to the above method to the obtained fiber reinforced composite material, the dent depth is 1.4 mm, the visibility of the damaged part is good, and the CAI is as high as 260 MPa. Value.
<Comparative Example 1>
An epoxy resin composition was obtained according to the following formulation.
・ "Araldite" MY-721 (epoxy resin manufactured by Huntsman Advanced Materials Co., Ltd.)
: 40 parts "Epicoat" 630 (Japan Epoxy Resin Co., Ltd. epoxy resin)
: 40 parts · GAN (Nippon Kayaku Co., Ltd. epoxy resin)
: 20 parts "Epicure" W (Aromatic amine manufactured by Japan Epoxy Resin Co., Ltd.)
: 41.7 parts · TBC (t-butylcatechol (curing catalyst) manufactured by Ube Industries, Ltd.)
1 part The viscosity of the epoxy resin composition at 80 ° C. was measured with an E-type viscometer, and found to be 20 mPa · s.

  Further, the tensile elongation of this epoxy resin composition was measured in the same manner as in Example 1, and the result was 1.3%.

Furthermore, using this epoxy resin composition, a fiber-reinforced composite material having a volume content of reinforcing fibers of 58% was obtained in the same manner as in Example 1. As a result of applying an impact energy of 20 J per 1 mm thickness of the test piece to the obtained fiber reinforced composite material in the same manner as in Example 1, the dent depth was 0.4 mm, and the visibility of the damaged portion was poor. Was a low value of 140 MPa.
<Comparative example 2>
An epoxy resin was obtained by the following formulation:
"Epicoat" 630 (Japan Epoxy Resin Co., Ltd. epoxy resin: 70
・ GAN (Nippon Kayaku Co., Ltd. epoxy resin)
: 20 parts “Epicoat” 828 (epoxy resin manufactured by Japan Epoxy Resin Co., Ltd.): 10 parts “Kayahard” AA (aromatic amine manufactured by Nippon Kayaku Co., Ltd.)
: 59.4 parts TBC (t-butylcatechol (curing catalyst) manufactured by Ube Industries, Ltd.)
1 part The viscosity of the epoxy resin composition at 80 ° C. was measured with an E-type viscometer, and it was 15 mPa · s.

  Moreover, it was 1.1% as a result of producing hardened | cured material about this epoxy resin composition by the said method, and measuring tensile elongation.

Furthermore, the epoxy resin composition and the carbon fiber woven fabric are reinforced with a binder by spreading the binder composition with a basis weight of 3 g / m ² and fusing by heating to 170 ° C. using a far red heater. Using the base material, a fiber-reinforced composite material having a volume content of reinforcing fibers of 58% was obtained by the above method. As a result of applying an impact energy of 20 J per 1 mm thickness of the test piece to the obtained fiber reinforced composite material according to the above method, the dent depth was 0.4 mm, the visibility of the damaged part was poor, and the CAI was as low as 110 MPa. Value.

  As described above, the present invention can be suitably used for structural materials such as spacecrafts, aircrafts, railway vehicles, automobiles, ships, etc., but also in the fields of leisure industries such as tennis rackets, golf shafts, fishing rods, and construction. Can also be applied.

Claims (8)

An epoxy resin composition comprising a main agent containing an epoxy resin and a curing agent containing a component capable of curing the epoxy resin, and a cured product obtained by thermosetting at 180 ° C. for 2 hours, having a tensile elongation of 3 to 10% is a carbon fiber. A resin transfer molding molded fiber reinforced composite material which is injected and impregnated into a preform formed by laminating the reinforcing fiber substrate or heat-cured by a preform laminated with the reinforcing fiber substrate, and the cross-laminated The fiber-reinforced composite material having a thickness of 4 to 5 mm obtained from the reforming has a dent depth of 0.6 mm or more after applying an impact energy of 20 J per 1 mm thickness of the test piece according to JIS K 7089 (1996). A resin-transfer molding-reinforced fiber reinforced composite material. The fiber reinforced composite material having a thickness of 4 to 5 mm obtained from the cross-laminated preform has a residual compressive strength of 160 MPa after applying an impact of 20 J per 1 mm thickness of the test piece according to JIS K 7089 (1996). The resin transfer molding molded fiber reinforced composite material according to claim 1, which is as described above. The resin transfer molding molded fiber reinforced composite material according to claim 1 or 2, wherein the curing agent contains an aromatic amine. The resin transfer molding molded fiber reinforced composite material according to any one of claims 1 to 3, wherein the volume content of the reinforcing fibers is in the range of 50 to 65%. The resin-transfer molding-formed fiber-reinforced composite material according to any one of claims 1 to 4, wherein the reinforcing fibers constituting the reinforcing fiber substrate are oriented substantially in one direction in each layer. Resin transfer molding shaped fiber-reinforced according to claim 1, the binder composition is deposited in the range of 5 to 50 g / m ² comprising a thermoplastic resin on one or both surfaces of the reinforcing fiber substrate Composite material. The resin transfer molding molded fiber reinforced composite material according to any one of claims 1 to 6, which is obtained by heating and impregnating an epoxy resin composition obtained by mixing the main agent and a curing agent into the preform. The resin transfer molding molded fiber reinforced composite material according to any one of claims 1 to 7, wherein an initial viscosity of the epoxy resin composition before molding is 500 mPa · s or less at an arbitrary temperature of 25 to 90 ° C.