Provided is a prepreg containing a urethane (meth)acrylate (A), a polymerization initiator (B), and reinforcement fibers (C), characterized in that the polymerization initiator (B) is an alkyl peroxy ester compound having a 10-hour half-life temperature of 60° C. or higher and lower than 70° C. The prepreg has excellent storage stability and excellent moldability, even under the low-temperature molding condition of 110° C. or lower, and enables to obtain a molded article having excellent physical properties such as interlaminar shear strength. Therefore, the prepreg can be suitably used in automobile components, railway vehicle components, aerospace craft components, ship components, housing equipment components, sporting components, light vehicle components, building and civil engineering components, and casings of OA equipment and the like.

A multiaxial fabric resin base material includes a multiaxial fabric base material laminate impregnated with a thermosetting resin (B), the multiaxial fabric base material laminate including fiber bundle sheets layered at different angles, the fiber bundle sheets including unidirectionally aligned fiber bundles stitched with stitching yarns composed of a thermoplastic resin (A), the multiaxial fabric base material laminate being penetrated in the thickness direction by other bodies of the stitching yarns, and being stitched with the other bodies of the stitching yarns such that the yarns reciprocate at predetermined intervals along the longitudinal direction, the thermoplastic resin (A) constituting the stitching yarns having a softening point, the softening point being higher than the resin impregnation temperature of the thermosetting resin (B).

A prepreg having at least one layer of fibres and a curable thermosetting resin system at least partly impregnating the at least one layer of fibres, wherein the curable thermosetting resin system includes a curable thermosetting resin including at least two epoxide groups, a curing agent that includes at least one amine group, and an accelerator that includes an azole group; wherein the curable thermosetting resin, the curing agent and the accelerator are provided in respective concentrations in the prepreg to provide that, after curing the thermosetting resin at a cure temperature of at least 140° C. for a period of from 1 to 6 minutes, (i) the cured thermosetting resin has a glass transition temperature Tg which is greater than the cure temperature and is within the range of from 150° C. to 180° C. and (ii) the cured thermosetting resin is at least 90% cured.

The present invention addresses the problem of providing a prepreg that has excellent short-time and low-pressure handling properties, during pasting and layering work. In order to solve the problem, this invention has the following configuration. The prepreg includes reinforcing fibers and an epoxy resin composition, has a fiber content of 90 mass % or less, and satisfies conditions (a) and (b) below. (a) When the average thickness of the prepreg is set as D (D being 3 μm or greater), the viscosity at 25° C. of the epoxy resin composition at a site (I) located at a depth of D/4 to 3D/4 from the surface on one side of the prepreg is 50,000 to 300,000 Pa.Math.s inclusive. (b) From among sites (II) located at a depth of up to 0.5 μm from each surface on both sides of the prepreg, the viscosity at 25° C. of the epoxy resin composition at least at a site (II) on the one side is 10,000 to 40,000 Pa.Math.s inclusive.

A curable composition including a first compound having a group represented by general formula (x) and an epoxy group and having a molecular weight of 1000 or less. In the general formula (x), Rf.sub.1 and Rf.sub.2 each independently represent a fluorine-containing alkyl group.

—C(Rf.sub.1)(Rf.sub.2)—OH  (x)

Pre-impregnated composite material (prepreg) that can be cured/molded to form aerospace composite parts. The prepreg includes carbon reinforcing fibers and an uncured resin matrix. The resin matrix includes an epoxy resin component, polyethersulfone as a toughening agent, a thermoplastic particle component, a nanoparticle component and a curing agent.

In an embodiment, an adhesive sheet has an expandable adhesive layer 2 on one side or both sides of a base 1, wherein the expandable adhesive layer 2 contains an epoxy resin including a polyfunctional epoxy resin, a phenol resin as a curing agent, an imidazole-based compound as a curing catalyst, and a temperature-sensitive foaming agent. The adhesive sheet has properties in good balance, such as fast curability, heat resistance, and adhesiveness, and also excellent properties such as thermal conductivity attributed to a good filling property.

Provided is a sheet-like prepreg that has both a low coefficient of linear thermal expansion and high flexibility and offers excellent anti-warpage performance and cracking resistance. The sheet-like prepreg according to the present invention includes a curable composition and a sheet-like porous support impregnated with the curable composition. The sheet-like porous support is made from a material having a coefficient of linear thermal expansion of 10 ppm/K or less. The sheet-like prepreg gives a cured product having a glass transition temperature of −60° C. to 100° C. The curable composition includes one or more curable compounds (A) and at least one of a curing agent (B) and a curing catalyst (C). The curable compounds (A) include an epoxide having a weight per epoxy equivalent of 140 to 3000 g/eq in an amount of 50 weight percent or more of the totality of the curable compounds (A).

The present invention provides a prepreg from which a fiber-reinforced composite article in which interlayer peeling at the time of a point impact is suppressed can be obtained; a fiber-reinforced composite article; and a manufacturing method thereof.

An epoxy resin represented by the following formula (1), in which in a total amount of an epoxy compound represented by n=1 in the epoxy resin of the above formula, a total content of an epoxy compound represented by the following formula (2) and an epoxy compound represented by the following formula (3) is 1 area % or more and less than 70 area % in HPLC area percentage.

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