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Co-consolidation in press forming process to realize integral components with local reinforcements

Due to their unique chemical behaviour in exposition to heat, continuous fiber reinforced thermoplastics open up new paths in fast processing in order to reduce cycle times and manufacturing costs. Molecules that slide past each other instead of crosslinking during curing process enable welding and moulding processes. In this first feasibility study, the joining process of two thermoplastic laminates by means of co-consolidation at panel level is investigated. A typical possible application is the integration of local reinforcements in press forming to manufacture integral components in one-shot-processes.

Both joining partners consist of the same laminate, which is eleven layers of UD carbon fibre (AS4) reinforced polyether ether ketone (APC-2). Partner A is manufactured in automated tape laying process with partial consolidation, whereas the counterpart, partner B, is a fully consolidated organic sheet, processed in autoclave. Since partner B represents a local reinforcement for partner A, it is smaller in size. Placed in a pocket tool, partner B is heated above melting temperature on the upper surface by an IR radiator field that is sliding inside the press. Simultaneously, partner A is melted throughout the whole laminate thickness in an IR radiator field, positioned next to the press. When both partners have reached the molten state, partner A is co-consolidated with partner B by press-forming.

The benchmark for this process is given by specimens, co-consolidated in an autoclave process. Object of interest is the adhesion of both joining partners, which is validated in double cantilever beam tests (DCB-test), where specimens are loaded on peel failure. Results reveal more than 10 % higher mode I fracture toughness and maximum peel force for the press-formed specimen. Based on this, it can be concluded that an adhesive bond between both partners can be achieved by means of co-consolidation in press forming. In subsequent studies, three dimensional forming shall be conducted.

Julian Weber
Institut für Verbundwerkstoffe GmbH (IVW)