Stamp forming of continuous glass fibre reinforced polypropylene

Abstract

Abstract A thermoforming technique, known as stamp forming, has been used to process unidirectional glass fibre reinforced polypropylene (PP). A novel hemispherical mould with built-in hold-down arrangement was designed. This mould was used at room temperature to form parts from pre-heated flat pre-consolidated laminates. Pre-consolidated laminates are heated by contact heating in an external heater above the melting temperature of the PP polymer matrix; they are then formed in the cold matched metal tool. Typical cycle times to process the pre-consolidated laminates (including pre-heating time of the pre-consolidated laminates) are in the range of 2 min. Useful processing conditions, such as stamping temperature, stamping velocity and hold-down pressure required for the stamp forming of this composite are determined. The effects of die geometries and laminate dimension on the `fibre buckling' are studied. Finally, the thickness distribution in stamped parts is investigated in relation to different directions of fibre orientation.