Epoxy resin composition for fiber reinforced composite material

1. A fiber reinforced prepreg produced by combining a reinforcing fiber with the epoxy resin composition for a fiber reinforced composite material, serving as a matrix resin:

the epoxy resin composition for the fiber reinforced composite material comprising:

an epoxy resin (A) comprising an epoxy resin (a1) having a weight average molecular weight of up to 1,000 and an epoxy resin (a2) having a weight average molecular weight of 42,000 to 60,000 which contains at least 20% by weight of the basic skeleton of the epoxy resin (a1),

a thermoplastic resin (B), and

a curing agent (C),

wherein the basic skeleton of the epoxy resin (a1) is bisphenol F, and the basic skeleton in the epoxy resin (a2) is bisphenol F or a copolymer of bisphenol A and bisphenol F, and

wherein the thermoplastic resin (B) is polyethersulfone resin, and

wherein the cured composition has a co-continuous phase of the epoxy resin (A) and the thermoplastic resin (B) and the epoxy resin (a2) having smaller particle size compared to the epoxy resin (A) is dispersed in the continuous phase of the epoxy resin (A), and

the epoxy resin (a2) is added in an amount of 5 to 15 parts by weight in relation to 100 parts by weight of the epoxy resin (A) excluding the epoxy resin (a2).

2. The fiber reinforced prepreg according to claim 1 , wherein the matrix resin is included in an amount of 30 to 50% by weight of the fiber reinforced prepreg.

3. The fiber reinforced prepreg according to claim 1 , wherein the reinforcing fiber is at least one member selected from the group consisting of carbon fiber, glass fiber and aramid fiber.

4. The fiber reinforced prepreg according to claim 1 , wherein the epoxy resin (a1) is included in an amount of 7 to 70 parts by weight in relation to 100 parts by weight of the epoxy resin (A) excluding the epoxy resin (a2).