Abstract: Disclosed is a plate-like carbon fiber-reinforced composite material comprising carbon fibers, wherein that the carbon fibers have a strain at compressive break of 1.7 to 5%, a tensile elastic modulus of 5 to 160 GPa, and a density of 1.5 to 1.9 g/cm3 and further in that the composite comprising said carbon fibers cause no delamination by an impact energy of less than 1.4 J/mm in the test of compression after impact in accordance with JIS K 7089.

Abstract: The resent invention provides a carbon fiber which enables a molded article produced from a fiber-reinforced composite material using the carbon fiber to exhibit excellent flexibility and to be freed from defects such as bending. According to the method of the present invention the carbon fiber is produced by a two-stage infusibilizing process, namely carrying out a first-stage infusibilization of a pitch-based fiber, which is obtained from mesophase pitch having a softening point of 200 to 400° C. and a true density of 1.30 to 1.38 g/cm3, in a mixed gas atmosphere having a nitrogen dioxide concentration of 1 to 5% by volume and an oxygen concentration of 5 to 50% by volume, the balance being an inert gas or steam, at a temperature between 100 and 200° C. and then carrying out a second-stage infusibilization of the product of the first-stage infusibilization in a mixed gas atmosphere having a nitrogen dioxide concentration of 0.

Abstract: A disk pad type brake comprises a rotor disk provided with a carbon-carbon composite material (a) as a friction member, and at least one pad provided with a carbon-carbon composite material (b) as a friction member, wherein the difference in thermal conductivity between the materials (a) and (b) is 30 to 450 W/m.multidot.K in the radial direction; and a multi-disk type brake comprises at least one rotor disk provided with a carbon-carbon composite material (c) as a friction member, and at least one stator disk provided with a carbon-carbon composite material (d) as a friction member, wherein the difference in thermal conductivity between the materials (c) and (d) is 30 to 450 W/m.multidot.K in the radial direction.

Abstract: A method for manufacturing a carbon preform comprising the steps of charging a container with pitch fibers obtained by melt spinning a carbonaceous pitch to fill therein during spinning, infusibilizing the thus filled pitch fibers, and calcining and molding the infusibilized pitch fibers under a uniaxial pressure, and a method for manufacturing a carbon/carbon composite material comprising densifying the carbon preform.

Abstract: A method for preparing a carbon/carbon composite material which is characterized in that a carbon preform is impregnated with a carbonaceous pitch exhibiting a densification parameter of 0.1 or more, said densification parameter being represented by the following formula (1), and then subjected to an isotactic compression at a pressure higher than the atmospheric pressure but not higher than 10 Kgf/cm.sup.2 and at a sintering temperature of 250.degree. to 3,000.degree. C., thereby densifying the carbon preform:Densification parameter={(Weight of a sintered carbonaceous pitch (hereinafter, referred to simply as a sintered product) to be obtained through a process where a carbonaceous pitch in an open-type container is heated from room temperature up to 1000.degree. C. at a rate of 2.degree. C./min., and then sintered for 2 hours at 1000.degree. C. under isotactic compression of 9.5 Kgf/cm.sup.2)}/(Weight of a carbonaceous pitch before being sintered).times.