Dr. Stephen Tsai, professor research emeritus in the Department of Aeronautics & Astronautics at Stanford University, suggested an invariant-based method for accelerating aerospace certification testing. He identified trace (the sum of three components of stiffness, plus that of shear) as the one and only property of composites that can make composites easier to understand, and design and testing of composites simple and straightforward. Can we use this method to study vibration behaviour of laminated plates?