OPTIMIZATION OF STAMP FORMING OF THERMOPLASTIC COMPOSITE BENDS

This paper describes an experimental study on the development of a two-dimensional stamping method for the processing of unidirectional fiber reinforced composites with thermoplastic matrices, in which an angle mold (90 degrees) and a mechanical press are used. Materials investigated were carbon fiber reinforced polypropylene, polyamide 12, pory(ether ether ketone) and glass fabric woven reinforced polyetherimide. Preconsolidated laminates were heated in a separate heating press, employing a contact heating method, to above the melting temperature of the corresponding matrix and then immediately transported into the cold mold and thermoformed. The processing conditions, e.g. the thermoforming temperature, time, rate and pressure, required to give high-quality right-angle parts were established. A processing window for stamping is generated, which describes the correlation between processing parameters and the final part geometries. Finally, a finite element analysis method was employed to simulate the thermoforming process (for simplicity only under isothermal conditions). This technique gives more detailed information about the conditions under which the interply slip process between individual plies can occur in order to guarantee optimum laminate deformation during the stamp forming process.