Preliminary studies on single point incremental forming for composite materials

Abstract

This paper presents a preliminary investigation on applicability of Single Point Incremental Forming techniques (SPIF) to composite laminates. Initially the possibility of quickly and economically forming sheet metal moulds with complex geometry was evaluated. Then experimental tests were conducted to achieve the direct incremental forming of composite laminates. Different types of diaphragm were considered to avoid wrinkling and to improve the composite adhesion. The first results showed how this automated and flexible process is particularly suited for forming composite/metal hybrid materials. These laminates, consisting of alternating layers of thin metal sheet and composite, are used for their excellent damage tolerance properties, such as fatigue and impact resistance. In order to evaluate the possibility of simultaneously forming aluminium and composite sheets, different configurations of Fiber Metal Laminates (FML) were tested. Finally, compression tests were carried out to compare ductile fracture limits of the aluminium sheet and the FML. The preliminary experimental investigations reported in this paper show how moulds with complex geometry can be realized by SPIF. Choosing sufficiently stiff diaphragm and using vacuum to conform the composite materials, wrinkle-free parts can be formed in an incremental fashion, even if problems of non-uniform resin distribution still need to be solved. Moreover, FML with different configurations can be formed successfully, significantly improving the mechanical properties of sheet metal structures.