Abstract
Thermoforming of unconsolidated and consolidated polypropylene/glass fibre fabrics was studied for two mould geometries, i.e. a square mould and a mould with three studs. The principal objective of this study was to evaluate the feasibility of direct thermoforming of unconsolidated fabrics in complex moulds, since this process offers the potential of reducing the cost of the raw material by eliminating the separate consolidation step performed prior to moulding. In this work, the unconsolidated and consolidated fabrics plies were heated in a convection oven and then quickly transferred to a press to be simultaneously conformed and (re-)consolidated using a rubber punch and a metal cavity. Results show that similar product quality (evaluated by the void content) can be obtained with unconsolidated and consolidated fabrics once conformation to the mould shape is achieved. A minimal forming temperature of 215 °C is required to achieve conformation to the mould shape, while minimal forming pressures of 2 and 3 MPa must be applied to achieve the same objective for the consolidated and unconsolidated fabric, respectively. Increasing the punch hardness, varying the fabric orientation and increasing the number of vents could reduce the pressure necessary to produce conformation to the mould shape.