A laminated plate theory with first-order zig-zag sublaminate approximations is proposed. The inplane 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 obtained by satisfying the continuity of transverse shear stresses at layer interfaces. This in-plane displacement field assumption accounts for discrete layer effects without increasing the number of degrees of freedom as the number of layers is increased. The transverse normal strain predictions are improved by assuming a constant variation of transverse normal stress in each sublaminate. In the computational model, each finite element represents one sublaminate. The finite element is developed with the topology of an eight-noded brick, allowing the thckness of the plate to be discretized into several elements, or sublaminates, where each sublaminate can contain more than one physical layer. Each node has five engineering degrees of freedom, three translations and two rotations. Thus, this element can be conveniently implemented into general purpose finite element codes. The element stiffness coefficients are integrated exactly, yet the element exhibits no shear locking due to the use of an interdependent interpolation scheme and consistent shear strain fields. Numerical performance of the current element is investigated for a composite armored vehicle panel and a sandwich panel with low and high aspect ratios. Comparison of numerical results with elasticity solutions shows that the element is very accurate and robust.
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