Formability assessment of press forming process for uncured metal-composite laminates

METAL-composite laminates, also known as fibre metal laminates (FMLs), which are made by alternating thin sheets of metal alloys and layers of fibre reinforced polymers, have attracted the interest of many scholars and researchers in the field of aerospace applications, including manufacturing. These hybrid materials are widely applied owing to their significant advantages ofweight reduction, superior specific strength, higher stiffness, and more fatigue resistance than monolithic metal sheets as well as the better impact strength and damage tolerance compared with the full composites. However, the manufacturing process of such laminates is difficult as various forming and curing stages are required in combination with the complex deformation and failure mechanisms. Hence to improve the manufacturabilty of these structures, it is crucial to develop a material forming method with optimized material compositions and process parameters.

The proposed press forming process, consists of an integral forming and curing cycle, is an innovative method formanufacturing small-to-mediumsized components. The cycle involves a laminate preparing and preheating process, forming of the uncured laminate, consolidation and (partial) curing in a same mould as well as cooling and removal of the component. The most critical aspect of the cycle is a proper control of the different deformation mechanisms in different layers. For that, during the preheating stage, temperature and time needs to be carefully controlled so that the inter-ply sliding at the metal-prepreg interfaces and the intra-ply shear within the prepregs can be greatly enhanced when the resin viscosity decreases. Then, the still uncured laminate is formed and subesequently cured under pressure, avoiding a separate curing system with pressure, which is time and cost-saving...