Abstract: A carbon fiber-reinforced composite material is capable of transmitting an electromagnetic wave in a low frequency band while having an electromagnetic wave shielding performance in a high frequency band. The carbon fiber-reinforced composite material has a ratio SEM300K/SEM1G of a value SEM300K (dB) at 300 kHz to a value SEM1G (dB) at 1 GHz of a magnetic shielding effectiveness measured by a KEC method is 0.50 or less.

Abstract: A carbon fiber mat has discontinuous carbon fibers dispersed in the form of monofilaments, wherein the orientation direction of the monofilaments of the discontinuous carbon fibers is random, number average fiber length (Ln) is at least 1.5 mm and up to 15 mm, and proportion in number (Pa) of the discontinuous carbon fiber monofilaments having a fiber length in the range of median fiber length (Lc)±20% is at least 40% and up to 99%.

Abstract: A preform includes: (A) a self-reinforced sheet comprising (a-1) a thermoplastic resin and (a-2) a fiber or tape made of a thermoplastic resin which is the same type as the thermoplastic resin (a-1), the self-reinforced sheet (A) being reinforced with the fiber or tape (a-2); and (B) a reinforced sheet comprising (b-1) a randomly-oriented mat of discontinuous carbon fibers and (b-2) a thermoplastic resin. The self-reinforced sheet (A) and the reinforced sheet (B) are laminated one on another. Each thermoplastic resin serves as a matrix resin of the preform.

Abstract: The present invention relates to a carbon fiber-reinforced polypropylene sheet which comprises carbon fibers having a weight-average fiber length of 1.5 mm to 20 mm and a matrix resin composed of a polypropylene and an acid-modified polypropylene, wherein the carbon fibers are dispersed in the form of single fibers and the interfacial shear strength between the carbon fibers and said matrix resin is 5.50 to 10.5 MPa. Provided is a carbon fiber-reinforced polypropylene sheet for obtaining a molded article having excellent mechanical properties and impact resistance, which carbon fiber-reinforced polypropylene sheet comprises discontinuous carbon fibers and a polypropylene, can be molded into a complex shape and has isotropic mechanical properties.

Abstract: The present invention relates to a carbon fiber-reinforced polypropylene sheet which comprises carbon fibers having a weight-average fiber length of 1.5 mm to 20 mm and a matrix resin composed of a polypropylene and an acid-modified polypropylene, wherein the carbon fibers are dispersed in the form of single fibers and the interfacial shear strength between the carbon fibers and said matrix resin is 5.50 to 10.5 MPa. Provided is a carbon fiber-reinforced polypropylene sheet for obtaining a molded article having excellent mechanical properties and impact resistance, which carbon fiber-reinforced polypropylene sheet comprises discontinuous carbon fibers and a polypropylene, can be molded into a complex shape and has isotropic mechanical properties.