FIBER-REINFORCED COMPOSITE MATERIAL
A fiber-reinforced composite material can achieve dynamical properties at high levels, and can simultaneously improve Mode I interlaminar fracture toughness G IC and Mode II interlaminar fracture toughness G IIC . The fiber-reinforced composite material has a plurality of reinforcing-fiber-containing layers and an interposing resin layer between adjacent reinforcing-fiber-containing layers. The resin layer is composed of a cured product of a resin composition containing a compound having a benzoxazine ring of formula (1), epoxy resin, a curing agent, a toughness improver, and polyamide 12 powder. The composite material has a G IC of not lower than 300 J/m 2 , and a G IIC of not lower than 1000 J/m 2 : (R 1 : C1-C12 chain alkyl group; H is bonded to at least one of the carbon atoms of the aromatic ring at ortho- or para-position with respect to C to which the oxygen atom is bonded).
1 . A fiber-reinforced composite material comprising a plurality of reinforcing-fiber-containing layers and a resin layer in each interlaminar region between adjacent reinforcing-fiber-containing layers, said layers obtained by curing a laminate of a plurality of prepregs, wherein said resin layer consists of a cured product of a resin composition comprising (A) a compound having in its molecule a benzoxazine ring represented by formula (1):
wherein R 1 stands for a chain alkyl group having 1 to 12 carbon atoms, a cyclic alkyl group having 3 to 8 carbon atoms, a phenyl group, or a phenyl group substituted with a chain alkyl group having 1 to 12 carbon atoms or a halogen, and a hydrogen atom is bonded to at least one of the carbon atoms of the aromatic ring at ortho- or para-position with respect to the carbon atom to which the oxygen atom is bonded, (B) epoxy resin, (C) a curing agent, (D) a toughness improver, and (E) polyamide 12 powder,
wherein said fiber-reinforced composite material has a Mode I interlaminar fracture toughness G IC of not lower than 300 J/m 2 , and a Mode II interlaminar fracture toughness G IIC of not lower than 1000 J/m 2 .
2 . The composite material according to claim 1 , wherein said (B) epoxy resin is at least one epoxy resin selected from the group consisting of cresol novolak type epoxy resin, phenol novolak type epoxy resin, epoxy resin having a biphenyl skeleton, epoxy resin having a naphthalene skeleton, aromatic glycidyl ester type epoxy resin, aromatic amine type epoxy resin, resorcin type epoxy resin, and cyclic epoxy resin.
3 . The composite material according to claim 1 , wherein said (C) curing agent is at least one member selected from the group consisting of aromatic amines, monofunctional phenol, polyfunctional phenol compounds, or polyphenol compounds.
4 . The composite material according to claim 1 , wherein said (D) toughness improver is at least one member selected from the group consisting of inorganic fine particles, organic fine particles, a liquid resin having inorganic and/or organic fine particles dispersed therein, and a resin monomer having inorganic and/or organic fine particles dispersed therein.