Stamp forming analysis of a Fibre Metal Laminate system consisting of a Glass fibre reinforced composite

In an effort to reduce greenhouse gas emissions from fuel combustion generated by the transportation sector, the use of lightweight materials such as composites is currently being intensively explored. The projected improvement in fuel-economy for passenger vehicles is 6-7% for every 10% of weight reduction. Fibre Metal Laminate (FML) systems are a class of composite materials comprised by alternating aluminium sheets and fibre reinforced composites. The resulting synergy of material behaviour gives FML systems superior mechanical properties when compared with those of their individual constituent materials. FML systems based on thermoplastic composites have been shown to possess better fracture toughness, shorter processing times, good impact and localised blast resistance compared to metals. These structures have been successfully employed in the aerospace industry. However, the widespread use of these material systems is restricted by the current manufacturing processes required to create components. For the better utilisation of FML systems, it is necessary that the thermal properties of the materials be used in addition to conventional processing. This would involve the heating of the FML prior to forming. However, a successful approach that includes both metal forming processes and the composite forming process is essential to maintain the high manufacturing volumes currently required for industry. It is likely that this approach would be similar to the stamp forming process used in sheet metal manufacturing with an included pre-heat stage. In this work, results will be presented for FML systems consisting of aluminium/Glass fibre reinforced thermoplastic/aluminium configuration. A Design of Experiments (DOE) methodology was adopted to elucidate the effect of process parameters that included blank holder force, pre-heat temperature and feed rate on dome forming studies. A real time strain measurement system was used to monitor the strain evolution during forming. An open die configuration was adopted to facilitate the strain evolution during forming. Three points of interest were chosen to study the different forming modes exhibited at different locations in the FML system. The results indicate that the presence of the composite layer modify the forming behaviour of the FML system compared to forming of monolithic aluminium alloy.