Rigid Flexible Composites are used as important components in lightweight constructions in many cases. The application of these composites is limited by the bond strength, i. e. the adhesion between the components. A new method to determine the bond strength as a material parameter is proposed. Metal Plastic Hybrids are studied with the Peel Test (90°). The adhesion energy can be separated from all other energy contributions by extrapolation to very small thicknesses of the flexible component.