Thick beam theory and finite element model with zig-zag sublaminate approximations

A new technical theory and associated finite element model is introduced for thick laminated and sandwich beams. The theory can be cast as a layerwise theory with high-order zig-zag sublaminate approximations, thus greatly reducing the number of degrees of freedom required to accurately describe the bending and transverse shear kinematics in thick laminates. Furthermore, the theory is adaptable, allowing the user to choose the number of sublaminate approximations to achieve the desired accuracy. Based on this theory, a simple, efficient, and robust finite element model is developed that has the nodal topology of a four-noded planar element yet has the advantages of beam-type kinematics and a special interpolation scheme that obviates locking. The element contains a single zig-zag sublaminate approximation. If desired, multiple elements can be used through the thickness of a laminate to increase accuracy.