Abstract: A fiber reinforced composite material having high interlaminar toughness and compressive strength under wet heat conditions, as well as an epoxy resin composition for production thereof and a prepreg producible from the epoxy resin composition is described. The prepreg includes at least constituents [A], [B], and [C] as specified below and reinforcement fiber, wherein 90% or more of constituent [C] exists in the depth range accounting for 20% of the prepreg thickness from the prepreg surface: [A] epoxy resin; [B] epoxy resin curing agent; and [C] polymer particles insoluble in epoxy resin.

Abstract: Provided is an epoxy resin composition with improved heat resistance and resin elongation. Further provided is a fiber-reinforced composite material which uses the epoxy resin composition and thereby excels in compression strength in high-temperature environments and interlaminar toughness. The epoxy resin composition comprises the constituents [A], [B] and [C], 8-40 mass % of [B] is contained in the epoxy resin composition. The number of moles of active hydrogen contained in [C] is 1.05-2.0 times the number of moles of epoxy groups contained in the entire epoxy resin composition, in a cured resin formed by curing the epoxy resin composition and having a degree of curing of at least 90% obtained by DSC (differential scanning catorimetry), [A], [B] and [C] form a monolayer structure, or a phase separation structure of less than 500 nm. The rubber state modulus of elasticity Y (MPa) and glass transition temperature X (° C.) obtained by DMA (dynamic mechanical analysis) of the cured resin satisfy formula (1).

Abstract: The invention provides a prepreg that can give a fiber-reinforced composite material exhibiting stable and excellent interlaminar fracture toughness and impact resistance under wide molding conditions. The prepreg includes at least a reinforcement fiber [A], a thermosetting resin [B], and the following component [C] wherein 90% or more of the material [C] is present inside a region of the prepreg that extends from any surface of the prepreg to a prepreg site having, from the surface, a depth of 20% of the thickness of the prepreg. The component [C] satisfies requirements that (i) the storage elastic modulus G? of the material constituting the particles is more than 1 MPa, and 70 MPa or less at 180° C., and that (ii) the ratio of the storage elastic modulus G? of the material constituting the particles at 160° C. to the storage elastic modulus G? of the material at 200° C. ranges from 1 to 5; and is insoluble in the thermosetting resin [B].

Abstract: A two-pack type epoxy resin composition for fiber-reinforced composite materials includes components [A] to [D], with component [D] being a liquid at room temperature or a solid having a melting point of 130° C. or less: [A] an epoxy resin; [B] an acid anhydride; [C] a compound that has an average of 2.5 or more hydroxyphenyl structures in each molecule; and [D] an organic phosphorus compound or imidazole derivative.

Abstract: The invention provides a prepreg that can give a fiber-reinforced composite material exhibiting stable and excellent interlaminar fracture toughness and impact resistance under wide molding conditions. The prepreg includes at least a reinforcement fiber [A], a thermosetting resin [B], and the following component [C] wherein 90% or more of the material [C] is present inside a region of the prepreg that extends from any surface of the prepreg to a prepreg site having, from the surface, a depth of 20% of the thickness of the prepreg. The component [C] satisfies requirements that (i) the storage elastic modulus G? of the material constituting the particles is more than 1 MPa, and 70 MPa or less at 180° C., and that (ii) the ratio of the storage elastic modulus G? of the material constituting the particles at 160° C. to the storage elastic modulus G? of the material at 200° C. ranges from 1 to 5; and is insoluble in the thermosetting resin [B].

Abstract: A two-pack type epoxy resin composition for fiber-reinforced composite materials includes components [A] to [D], with component [D] being a liquid at room temperature or a solid having a melting point of 130° C. or less: [A] an epoxy resin; [B] an acid anhydride; [C] a compound that has an average of 2.5 or more hydroxyphenyl structures in each molecule; and [D] an organic phosphorus compound or imidazole derivative.

Abstract: The invention provides a fiber reinforced composite material having high interlaminar toughness and compressive strength under wet heat conditions, as well as an epoxy resin composition for production thereof and a prepreg producible from the epoxy resin composition. The prepreg comprises at least constituents [A], [B], and [C] as specified below and reinforcement fiber, wherein 90% or more of constituent [C] exists in the depth range accounting for 20% of the prepreg thickness from the prepreg surface: [A] epoxy resin [B] epoxy resin curing agent [C] polymer particles insoluble in epoxy resin and falling under any of the following [Cx] to [Cz]: [Cx] polymer particles insoluble in epoxy resin and giving a particle diameter distribution chart meeting the following requirements from (x-i) to (x-iii): (x-i) the chart has at least two peaks, (x-ii) the particles giving the two highest peaks have a diameter ratio in the range of 1.