Abstract: A laminated composite bar of rectangular cross section consists of a middle portion of one material as well as upper and lower identical cover plates of another material. Couples formed by linear bending stresses act in the middle portion at the ends of the bar (Fig. la) to cause bending. Interlaminar stresses are to be found showing how the forces are transmitted through the glued surfaces to the cover plates.

Key words: Birkhoffian systems, symplectic structure, self-adjointness, Poincaré-Cartan integral invariants