A NONLINEAR-THEORY FOR SANDWICH SHELLS INCLUDING THE WRINKLING PHENOMENON

This paper presents (on the base of the classical and some additional sandwich assumptions) a geometrically nonlinear theory for sandwich shells with seven kinematic degrees of freedom which is capable to describe the global as well as the local (load singularities, wrinkling) structural behaviour. For the kinematic specification a position vector is used to describe a point of the geometrical middle surface and a corresponding director (no unit vector) as well as a further scalar degree of freedom which could be explained as the linear part of the transversal strain. According to the definition of Green-Lagrangian strains and second Piola-Kirchhoff stress resultants, the nonlinear field equation of force equilibrium with pertinent boundary conditions will be gained from the principal of virtual work. Finally, the equation according to the first order theory for plane structures will be mentioned as a simple special case.