Abstract: A fiber-reinforced composite material can achieve dynamical properties at high levels, and can simultaneously improve Mode I interlaminar fracture toughness GIC and Mode II interlaminar fracture toughness GIIC. 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 GIC of not lower than 300 J/m2, and a GIIC of not lower than 1000 J/m2: (R1: 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).

Abstract: The purpose of the present invention is to inhibit a decrease in strength attribute to the interface between a simple-shape portion and a complicated-shape portion. This fiber-reinforced resin composite material comprises: a simple-shape portion formed from at least one sheet-shaped prepreg material obtained by impregnating reinforcing fibers with a resin; and a complicated-shape portion obtained by impregnating reinforcing fibers with a resin, the complicated-shape portion having been integrated with the simple-shape portion. The resin used for the preprg material comprised the same components as the resin used for the complicated-shape portion.

Abstract: Provided are a fiber-reinforced composite material capable of achieving excellent CAI, ILSS, and bending fracture toughness concurrently at high levels, and maintaining a high glass transition temperature of the resin material therein, and prepreg and a benzoxazine resin composition therefor. The composition contains, at a particular ratio, (A) a compound having in its molecule a benzoxazine ring represented by formula (1), (B) an epoxy resin, (C) a curing agent, (D) a toughness improver, and (E) polyamide 12 particles of a particular particle size, and component (D) is dissolved: (R1: C1-C12 chain alkyl group or the like, and H is bonded to at least one of Cs of the aromatic ring at o- or p-position with respect to the carbon atom to which the oxygen atom is bonded).

Abstract: The invention provides a benzoxazine resin composition having excellent resistance to heat and moisture and providing excellent handleability when made into prepreg, and prepreg and a fiber-reinforced composite material prepared from the composition. The composition contains (A) a compound having in its molecule a benzoxazine ring represented by the formula (1), (B) an epoxy resin, (C) a curing agent, and (D) a toughness improver: (R1: C1 to C12 chain alkyl group, etc., and H is bonded to at least one of C of the aromatic ring at o- or p-position to the carbon atom to which the oxygen atom is bonded).