Crank arm for a bicycle pedal crank system and a method for its production

A method for producing a crank arm for a bicycle pedal crank system, comprising the following steps:

• providing of an elongated, closed hollow core (30) made of a first fiber-reinforced plastic with a matrix made of a first thermoplastic material, wherein the hollow core (30) has a front face, a rear face opposed thereto and two axially convex side faces (102) which connect the front face and rear face with one another, said hollow core (30) having metallic shaft sleeves (20, 22) at its axial ends (104, 405), said shaft sleeves (20, 22) being oriented parallel to one another and to the side faces, for accommodating a bottom bracket shaft or a pedal axle;
• wrapping multiple times axially around the hollow core (30) a carbon fiber thread (50) that is encased in a thermoplastic material;
• inserting the wrapped hollow core (30) into a plastic injection molding tool (60);
• and
• overmolding the wrapped hollow core (30) in the plastic injection molding tool (60) with a fiber-filled, second thermoplastic material, wherein the temperature of the second thermoplastic material and/or of the plastic injection molding tool is set so that the surface of the hollow core (30) and of the encasing thermoplastic material fuses or melts during overmolding so that a bonded connection results.