Carbon fibres are industrially produced fibres with very high strength and stiffness, but low elongation at break. In general, carbon fibres are produced by carbonising polymer fibres, particularly polyacrylonitrile (PAN). All atoms except carbon are separated in a pyrolysis process. Carbon fibre are used as reinforcing fibres for heavy-duty plastics with very high stiffness. A very good bond between the fibre surface and the plastic (matrix) is crucial in order to achieve the optimal reinforcement function. By means of a plasma treatment, the wettability can be improved by the matrix.