Potentiality of Hot Drape Forming to produce complex shape parts in composite material

Abstract

The diffusion of prepreg composite material parts is hampered by high cost of both raw material and manufacturing process. As for this latter, it is due to the manual ply-on-ply layering carried out by skilled workers. A technology that can be used to preform prepreg plies on the mould is Hot Drape Forming that is a particular thermoforming process in which a prepreg stack is heated and preformed on the mould in a single step, pressing it through an elastic membrane and vacuum. This process is suitable for complex shape parts, however it must be analysed and optimized to fulfil the stringent specifications of aeronautical industry. The aim of this work was to introduce the Hot Drape Forming (HDF) process in the production cycle of complex shape parts; in particular, an unsymmetrical L-shape part, made of carbon/epoxy prepreg, was considered as case study. After a first production test in conformity with parameter suitable for simple shape parts, some general model were considered and adapted for HDF simulation to redesign the process and to obtain a part without defects, as wrinkles, resin-rich zones and thickness irregularity. Finally, some parts were produced to confirm the validity of process optimization.