Patent ID: 8137786

Claim:
An epoxy resin composition for fiber-reinforced composite materials, comprising: an epoxy resin (A); a thermoplastic resin (B); fine solid resin particles (C); and a curing agent (D), wherein, in a morphology of the epoxy resin composition after being cured, the epoxy resin (A) and the thermoplastic resin (B) form co-continuous phases, and the fine solid resin particles (C) are dispersed in at least the continuous phase of the epoxy resin (A) in the co-continuous phases and completely dissolved in the epoxy resin (A) at the time of heat curing of the epoxy resin composition, wherein the epoxy resin composition contains, with respect to 100 parts by weight of the epoxy resin (A), 30 to 50 parts by weight of the thermoplastic resin (B) and 2 to 20 parts by weight of the fine solid resin particles (C); wherein the fine solid resin particles (C) is made of a resin having a molecular weight of from 10,000 to 100,000; wherein a fracture toughness value measured according to ASTM D5045-91 after curing of the epoxy resin composition is 1.8 MPa·√m or larger.