1 Introduction 1.1 Background of Report The demand for bigger, faster and lighter moving vehicles, such as ships and trains has increased the demand for efficient structural arrangements. In principle two approaches exist to develop efficient structures: application of new materials or new structural design. These approaches are usually interactive so that application of new material also requires new structural solutions. Figure 1 illustrates the two possible approaches to obtain lighter structures. The structural arrangements can be kept the same while the normal strength steel is changed to high strength steel or aluminium. When applying the composites also the structural arrangements have to be changed. Sandwich panels form one type of efficient structures enabling the use of steel, aluminium or composites for the constructions. (Kujala et al., 1995).