EPOXY RESIN COMPOSITION FOR FIBER-REINFORCED COMPOSITE MATERIALS, PREPREG, AND FIBER-REINFORCED COMPOSITE MATERIAL

Provided are: a fiber-reinforced composite material which has mode I interlaminar fracture toughness, mode II interlaminar fracture toughness and compressive strength under heat and humidity conditions at the same time; an epoxy resin composition for obtaining the fiber-reinforced composite material; and a prepreg which is obtained using the epoxy resin composition. An epoxy resin composition for fiber-reinforced composite materials, which contains at least the following constituent elements (A), (B), (C) and(D). (A) An epoxy resin (B) Resin particles that satisfy the following conditions (bl)-(b3) and are insoluble in an epoxy resin (b1) The particle size distribution index is 1.0-1.8. (b2) The particle sphericity is 90 or more. (b3) The glass transition temperature of the particles is 80-180°C. (C) At least one elastomer component that is selected from among block copolymers containing a block having a glass transition temperature of 20°C or less and rubber particles (D) An epoxy resin curing agent