An object of the present invention is to provide an epoxy resin composition excellent in elastic modulus and strength, and a prepreg and a fiber reinforced composite material with the epoxy resin composition. The present invention is the epoxy resin composition including the following components [A] to [C] and satisfying the following conditions (1) to (3): [A]: epoxy resin [B]: aromatic diamine [C]: a compound having a boiling point of 130° C. or more and a molecular weight m of 50 or more and 250 or less, the compound having no epoxy group in the molecule and having substantially no curing ability of an epoxy resin

(1): at least a part of the component [C] satisfies that the sum of the polar component and the hydrogen bond component in the Hansen solubility parameters is 10.0 or more.

(2): at least a part of the component [C] satisfies that the Hansen solubility parameter distance L to the component [A] is 20.0 or less.

(3): the ratio H/E between the amount by mole, E, of the epoxy group of the component [A] and the amount by mole, C, of the component [C] satisfying both the condition (1) and the condition (2) is 0.01 or more and 0.20 or less.

(4): the viscosity at 70° C. for 2 hours is 5.0 times or less the initial viscosity at 70° C.

An object of the present invention is to provide an epoxy resin composition that can be preferably used for prepreg and fiber reinforced composite material applications and is excellent in elastic modulus, strength, and pot life.

The present invention is the epoxy resin composition including the following components [A] to [C] and satisfying the following conditions (1) to (3): [A]: epoxy resin [B]: polyamine curing agent, and [C]: a compound having a boiling point of 130° C. or more and a molecular weight m of 50 or more and 250 or less, the compound having no epoxy group in the molecule and having substantially no curing ability of an epoxy resin, and (1): at least a part of the component [C] has two or more alcoholic hydroxyl groups in the molecule. (2): the ratio C/E of the amount by mole, E, for epoxy groups of the component [A] to the amount by mole, C, of the component [C] satisfying the condition (1) is 0.01 or more and 0.20 or less. (3): the viscosity at 70° C. for 2 hours is 5.0 times or less the initial viscosity at 70° C.

A composition for fiber-reinforced resin that provides a fiber-reinforced resin with sufficient mechanical strength. The composition for fiber-reinforced resin contains at least one resin (A) selected from the group consisting of rosin resins, petroleum resins, terpene resins, and hydrides of cyclic ketone-aldehyde resins, and the resin (A) has a softening point of 80° C. to 180° C.

An object of the present invention is to provide a fiber-reinforced composite material achieving both lightweight properties and mechanical properties, a laminate thereof, and a prepreg capable of easily molding a sandwich structure thereof. The present invention is a prepreg comprising a reinforced fiber substrate (B) impregnated with a resin (A), wherein the reinforced fiber substrate (B) exists in a folded state having a plurality of folds with a fold angle of 0° or more and less than 90° in the prepreg.

An epoxy resin mixture which contains an epoxy resin represented by Formula (1) below and an epoxy resin represented by Formula (2) below at a weight ratio of 1:5 to 1:0.2. (In Formula (1), plural R1's each exist independently and represent a hydrogen atom or a C1-10 alkyl group, n represent a real number of 1 to 10, and G represents a substituted or unsubstituted glycidyl group.) (In Formula (2), plural R2's and R3's each exist independently and represent a hydrogen atom or a C1-10 alkyl group, n represents a real number of 1 to 10, and G represents a substituted or unsubstituted glycidyl group.)

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The present invention provides a fiber-reinforced-resin composite molded article including: a rigid layer that is formed of a fiber-reinforced-resin material for a rigid layer; a shaping layer that is formed, at least on one side of the rigid layer, of a shaping-layer compound composed of a thermosetting resin and fibers that are shorter than fibers contained in the fiber-reinforced-resin material for a rigid layer; and a cured resin being formed of a liquid-state resin that is deposited on the surface of the shaping layer. The fiber-reinforced-resin composite molded article has a structure in which the fiber-reinforced-resin material for a rigid layer, the shaping-layer compound, and the liquid-state resin are cured under heat and pressure in a layered state.

The present invention provides a polyfunctional phenolic resin and a polyfunctional epoxy resin having low viscosity and having excellent mechanical properties and heat resistance of a cured product to be obtained, a curable resin composition containing these, and a cured product thereof. Specifically, provided are a polyfunctional phenolic resin formed with a naphthol structure optionally having a substituent on an aromatic ring and a catechol structure optionally having a methyl group as a substituent on an aromatic ring bonded together via a methylene group optionally having a substituent, a polyfunctional epoxy resin obtained by epoxidizing the polyfunctional phenolic resin, a curable resin composition containing any of these, and a cured product thereof.

A fiber reinforced thermoplastic resin molded article includes a thermoplastic resin [A] and carbon fibers [B], a content of the thermoplastic resin [A] being 50 to 95 parts by weight and a content of the carbon fibers [B] being 5 to 50 parts by weight per 100 parts by weight of a total of the thermoplastic resin [A] and the carbon fibers [B], the molded article having a bending elastic modulus of 30 GPa or more, an interfacial shear strength between the thermoplastic resin [A] and the carbon fibers [B] being 15 MPa or more, and a logarithmic decrement of the molded article calculated by Formula (1) of less than 3, wherein the carbon fibers [B] have a weight-average fiber length (L.sub.w) of 0.5 to 10.0 mm:

Logarithmic decrement δ=(1/n)×ln(α.sub.(1)/α.sub.(1+n))  (1).

A method for producing a sheet molding compound including impregnating a resin composition into carbon fibers. The method is characterized in that the bulkiness H.sub.o of the carbon fibers before an impregnation step is 3 mm or more, the compression ratio R.sub.c (H.sub.c/H.sub.o) of the carbon fibers in the impregnation step is less than 1, the thickness of the sheet molding compound is 10 mm or less, and the content Wc of the carbon fibers is 40% by mass or more. The method for producing a sheet molding compound can produce a sheet molding compound having the excellent impregnation property into carbon fibers and thus can be preferably used for exteriors, structures, and the like of an automotive member, a railroad vehicle member, an aerospace vehicle member, a ship member, a housing equipment member, a sport member, a light vehicle member, a civil engineering and construction member, an OA equipment.

Provided is a prepreg containing a urethane (meth)acrylate (A), an ethylenically unsaturated monomer (B), a polymerization initiator (C), and reinforcement fibers (D), characterized in that the urethane (meth)acrylate (A) is a reaction product of a polyisocyanate (a1) and a polyol (a2) having an ethylenically unsaturated group and an aromatic skeleton, and/or a reaction product of a polyisocyanate (a1), a polyol (a3) not having an ethylenically unsaturated group but having an aromatic skeleton, and a hydroxyalkyl (meth)acrylate (a4), and that the ethylenically unsaturated monomer (B) has a molecular weight of 320 or more and a weight reduction rate (%) of less than 2 when heated under atmospheric pressure at 150° C. for 3 minutes. The prepreg has excellent moldability and enables to produce a molded article having excellent physical properties such as flexural strength and interlaminar shear strength, and therefore the prepreg can be suitably used in automobile components and the like.