A hybrid stiffness matrix for orthotropic sandwich plates with thick faces

A stiffness matrix is derived for a rectangular orthotropic sandwich plate element with thick faces by the assumed stress hybrid approach. It will be demonstrated that an independent polynomial can be used for the internal forces of the sandwich plate by the membrane theory (assumption of thin faces) and also for the additional moments and shear forces of the faces. The boundary displacements are approached solutions of the homogeneous differential equation of a sandwich beam.