A PARTIAL HYBRID DEGENERATED PLATE/SHELL ELEMENT FOR THE ANALYSIS OF LAMINATED COMPOSITES

A degenerated plate/shell element based on the combined energy variational principle and the equivalent single-layer model is proposed. It is derived from the 3-D continuum equation by imposing one constraint on the 3-D isoparametric solid element: a straight line normal to the mid-surface before deformation remains straight but not normal after deformation. The continuities of interlaminar stresses are satisfied at the interlaminar surface and the number of degrees of freedom per node is independent of the number of layers. In this work, the combined energy variational principle is used to overcome transverse stress continuity limitations of single-layer models. The traction-free conditions are satisfied on the upper and lower surfaces of a laminate by assuming the transverse stress components independently. The transverse normal strain is taken into account in order to consider the full 3-D effect in a laminated composite. The iso-function method and the classification method of the stress modes are used to construct the assumed stress field which contains a minimum number of stress modes and guarantees no zero energy mode in the element stiffness matrix. Three examples are presented to illustrate the efficiency and accuracy of the element