Abstract: The plastic instability of laminated sheet metal when stretched is analyzed from the view of phenomenal mechanics. It is proved that the characteristic values of laminate at the instable point on hardening curve change monotonously with compound ratio between those of two components. The approximate formulas to determine the instable point of laminate have been given by which the uniform elongation and tensile strength of laminate can be predicted from corresponding parameters of two components. So the basis is provided to design and apply a new laminate.

Key words: Laminated sheet metal, Plastic instability, Prediction, Property