First-order zig-zag sublaminate plate theory and finite element model for laminated composite and sandwich panels

A refined laminated plate theory and three-dimensional finite element based on first-order zigzag sublaminate approximations has been developed. The in-plane displacement fields in each sublaminate are assumed to be piecewise linear functions and vary in a zig-zag fashion through-the-thickness of the sublaminate. The zig-zag functions are evaluated by enforcing the ontinuity of transverse shear stresses at layer interfaces. This in-plane displacement field ssumption accounts for discrete layer effects without increasing the number of degrees of reedom as the number of layers is increased. The transverse displacement field is assumed to ary linearly through-the-thickness. The transverse normal strain predictions are improved by ssuming a constant variation of transverse normal stress in each sublaminate. In the omputational model, each finite element represents one sublaminate. The finite element is eveloped with the topology of an eight-noded brick, allowing the thickness of the plate to be iscretized into several elements, or sublaminates, where each sublaminate can contain more han one physical layer. Each node has five engineering degrees of freedom, three translations nd two rotations. Thus, this element can be conveniently implemented into general purpose inite element codes. The element stiffness coefficients are integrated exactly, yet the element hibits no shear locking due to the use of an interdependent interpolation scheme and consistent hear strain fields. Numerical performance of the current element is investigated for a omposite armored vehicle panel and a sandwich panel. These tests demonstrate that the lement is very accurate and robust.