Abstract: A prepreg is provided. The prepreg includes sizing agent-coated carbon fibers and a thermosetting resin composition (B) impregnated between the sizing agent-coated carbon fibers. The sizing agent includes a reactive component (A) having at least three reactive groups per molecule: (i) two or more first functional groups capable of reacting with the thermosetting resin composition (B), and (ii) at least one second functional group different from the two or more first functional groups (i). The second functional group includes at least one of amide, imide, urethane, urea, carbonyl, ester, sulfonyl, aromatic ring, or combinations thereof. The thermosetting resin composition (B) includes at least one thermosetting resin other than an epoxy resin and has a glass transition temperature of 220° C. or more after being cured.

Abstract: A fiber reinforced prepreg comprising reinforcement fibers; particles (D1) and (D2); and a thermosetting resin composition is provided. The resin includes maleimide compound (A), and co-monomer (B). Co-monomer (B) has least one of an alkenylphenol, an alkenylphenoxy, or a diamine group. Particles (D1) are smaller than (D2) and particles (D1) and (D2) are insoluble in the thermosetting resin. Particles (D1) range in diameter from 1 to 10 microns and have a mode on a volume basis from 3 to 6 microns and are present from 3 to 12 percent by volume of the thermosetting resin. Particles (D2) range from 10 to 100 microns diameter and a mode of 20 to 60 microns and are present from 1 to 6 percent by volume of the thermosetting resin composition. After cure, at least 90% by volume of particles (D1) and (D2) remain in the prepreg interlayers.