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Two quadrilateral-shaped multilayer plate bending/stretching elements based on the assumed-stress hybrid finite-element model are presented. These elements may be applied to the analysis of fiber composite plates and shells composed of an arbitrary number of layers and arbitrary material properties and fiber direction within each layer. Both elements incorporate the effects of transverse shear by including the transverse shear stresses τ xz and τ yz , and by assuming independent rotations of the normals to the plate midsurface, so that normals to the midsurface in the undeformed state need not be normal to the midsurface after deformation.In the formulation of an element based on the assumed-stress hybrid model, the stress distribution in the interior of the element is expressed in terms of a finite number of stress parameters such that equilibrium is satisfied, and the displacement distribution on the boundary of the element is expressed in terms of generalized nodal displacements such that interelement displacement compatibility is maintained. The principle at MICHIGAN STATE UNIV LIBRARIES on June 13, 2015 jcm.sagepub.com Downloaded from 52 difference between the two elements presented is the level of approximation incorporated into the stress and displacement assumptions. For one element the stresses within each layer are related to a set of stress parameters within that layer, and the boundary displacement assumption allows for independent cross-sectional rotations within each layer (and is thus capable of modeling the severe cross-sectional warping often associated with thick laminated plates). For the other element, the stresses within each layer are related to a set of stress parameters associated with the entire laminate, and the boundarv displacement assumption allows for a uniform rotation of the cross section of the laminate (not necessarily normal to the plate midsurface).To assess the behavior of the two elements, two laminated composite plate example problems are considered, for which analytic solutions are available. The accuracy of predicted stress and displacement results obtained by using the two hybrid elements are compared with the exact solutions for cases involving both thick and moderately thick plates. Comparisons of the relative accuracy and computing efficiency of the two elements are presented, and the limitations on the use of each element are also discussed.

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