Epoxy resin composition, fiber-reinforced composite material, and method for producing the same

Abstract

Disclosed herein are an epoxy resin composition for fiber-reinforced composite materials which has low viscosity, high Tg, high elastic modulus, and excellent fracture toughness and a fiber-reinforced composite material using such an epoxy resin composition which has excellent thermal properties, compressive strength, impact resistance, fatigue resistance, and open-hole tensile strength and which is suitable for producing structural parts of aircraft and the like. The epoxy resin composition comprises at least a given bifunctional epoxy resin as a component (A), a liquid aromatic diamine curing agent as a component (B), and core-shell polymer particles as a component (C), wherein the core-shell polymer particles as the component (C) contain epoxy groups in their shell and have a volume-average particle size of 50 to 300 nm.

1 . An epoxy resin composition comprising at least the following components (A), (B), and (C):
 (A) at least one bifunctional epoxy resin represented by any one of the following formulas (I), (II), and (III):   
       
         
           
           
               
               
           
         
         wherein R 1  to R 17  are each independently a substituent selected from among hydrogen, halogens, and C1 to C4 alkyl groups; 
         (B) a liquid aromatic diamine curing agent; and 
         (C) core-shell polymer particles, wherein the core-shell polymer particles as the component (C) contain epoxy groups in their shell and have a volume-average particle size of 50 to 300 nm. 
       
     
     
         2 . The epoxy resin composition according to  claim 1 , which contains the component (A) in an amount of 15 to 60 parts by mass with respect to 100 parts by mass of a total epoxy resin. 
     
     
         3 . The epoxy resin composition according to  claim 1 , further comprising a tri- or higher-functional aromatic epoxy resin as a component (D) in an amount of 30 to 70 parts by mass with respect to 100 parts by mass of the total epoxy resin. 
     
     
         4 . The epoxy resin composition according to  claim 1 , wherein the component (B) is at least one represented by any one of the following formulas (IV) to (VI): 
       
         
           
           
               
               
           
         
         wherein R 18  to R 29  are each independently a substituent selected from among hydrogen, halogens, and C1 to C4 alkyl groups. 
       
     
     
         5 . The epoxy resin composition according to  claim 4 , which contains 40 to 90 parts by mass of any one of liquid aromatic diamine curing agents represented by the formulas (IV) to (VI) or a mixture of two or more of them and 10 to 40 parts by mass of diaminodiphenylsulfone with respect to 100 parts by mass of a total amine curing agent. 
     
     
         6 . The epoxy resin composition according to  claim 5 , wherein the diaminodiphenylsulfone is a mixture of 3,3′-diaminodiphenylsulfone and 4,4′-diaminodiphenylsulfone. 
     
     
         7 . The epoxy resin composition according to  claim 1 , wherein a core of the component (C) is composed of a polymer obtained by polymerization of a monomer containing butadiene. 
     
     
         8 . The epoxy resin composition according to  claim 1 , which contains the component (C) in an amount of 1 to 12 parts by mass with respect to 100 parts by mass of the total epoxy resin. 
     
     
         9 . The epoxy resin composition according to  claim 1 , wherein a cured product obtained by curing the epoxy resin composition at 180° C. for 2 hours has a glass transition temperature different from that of the core of the component (C) by 210° C. or more and a fracture toughness (GO at −54° C. of 120 J/m 2  or higher. 
     
     
         10 . A fiber-reinforced composite material comprising at least a cured product of the epoxy resin composition according to  claim 1  and a fiber substrate composed of reinforcing fibers. 
     
     
         11 . A fiber-reinforcing composite material comprising at least a cured product of the epoxy resin composition according to  claim 1  and a fiber substrate composed of carbon fibers. 
     
     
         12 . The fiber-reinforced composite material according to  claim 11 , wherein the fiber substrate composed of carbon fibers is a non-crimp fabric comprising warps each of which is composed of one or more strands of the carbon fibers, auxiliary warps each of which is a glass fiber bundle or a chemical fiber bundle and which are arranged in parallel with the warps, and wefts each of which is composed of one or more glass fibers or chemical fibers and which are arranged perpendicularly to the warps and the auxiliary warps and interlaced with the auxiliary warps to integrally hold the carbon fiber strands. 
     
     
         13 . A method for producing a fiber-reinforced composite material comprising: placing a fiber substrate composed of reinforcing fibers in an inside of a mold; impregnating the fiber substrate with the epoxy resin composition according to  claim 1 ; and thermally curing the epoxy resin composition. 
     
     
         14 . A method for producing a fiber-reinforced composite material comprising: placing a fiber substrate composed of carbon fibers in an inside of a mold; impregnating the fiber substrate with the epoxy resin composition according to  claim 1 ; and thermally curing the epoxy resin composition. 
     
     
         15 . A method for producing a fiber-reinforced composite material comprising: placing, in an inside of a mold, a non-crimp fabric comprising warps each of which is composed of one or more strands of carbon fibers, auxiliary warps each of which is a glass fiber bundle or a chemical fiber bundle and which are arranged in parallel with the warps, and wefts each of which is composed of one or more glass fibers or chemical fibers and which are arranged perpendicularly to the warps and the auxiliary warps and interlaced with the auxiliary warps to integrally hold the carbon fiber strands; impregnating the non-crimp fabric with the epoxy resin composition according to  claim 1 ; and thermally curing the epoxy resin composition. 
     
     
         16 . A method for producing a fiber-reinforced composite material comprising: placing, in an inside of a mold, a non-crimp fabric comprising warps each of which is composed of one or more strands of carbon fibers, auxiliary warps each of which is a glass fiber bundle or a chemical fiber bundle and which are arranged in parallel with the warps, and wefts each of which is composed of one or more glass fibers or chemical fibers and which are arranged perpendicularly to the warps and the auxiliary warps and interlaced with the auxiliary warps to integrally hold the carbon fiber strands; impregnating the non-crimp fabric with the epoxy resin composition according to  claim 1  by evacuating the inside of the mold; and thermally curing the epoxy resin composition.