Sandwich manufacturing with foam core and coversheets out of aluminum - a new process without rolling: Presentation held at CellMAT 2016, 4th International Conference on Celluar Materials, Dresden, December 7 to 9, 2016

Sandwiches with aluminum foam core have been established as lightweight construction material during the last years. These semi-finished products are used particularly in the fields of engineering, construction, shipbuilding and commercial vehicle design. Commonly steel cover sheets are used for the sandwich creation because of their high stiffness and the ability to carry heavy loads. In the manufacturing process the two cover sheets are placed and fixed in a foaming mold realizing the desired spacing. A foamable precursor based upon aluminum and a foaming agent is inserted in between these cover sheets followed by a heat treatment up to the melting temperature of the Aluminum base alloy. During the foaming process a metallurgical bonding is created resulting in a rigid sandwich called SAS (steel – aluminum foam – steel).The manufacturing process of sandwiches with aluminum cover sheets with the method described above (SAS) is rather difficult. For the foaming process the required heat has to be introduced from the outside of the cover sheets to melt the internal precursor. Even through a skillful choice of alloys, the melting of the aluminum cover sheets and the foaming of the inserted aluminum precursor usually occurs at the same time. As a result, the desired semi-finished sandwich is not accomplished. That’s why another approach is needed for the sandwich preparation and proved to be feasible. The foamable material is placed in between two aluminum sheets. Afterwards the loose bond is rolled to a single composite with metallic bond. Therefore the heat transfer inside the composite is very good. By choosing alloys of different melting temperature it is possible to foam the inner precursor before the cover sheets start to melt. So the foaming process can successfully be completed. For this technological process the term AFS (Aluminum Foam Sandwich) has been established. One necessary step for the production of these foamable composite is the rolling, a process that is complex and expensive. Therefor alternative production methods needed to be considered as well. The already successfully tested approach of the SAS production was revisited, to manufacture small sandwiches with aluminum cover sheets according to the SAS process