Geometrically nonlinear analysis of layered anisotropic plates and shells

A degenerated three-dimensional finite element based on the total Lagrangian, incremental, formulation of a three-dimensional layered anisotropic medium is developed, and its use in the geometrically nonlinear, static as well as dynamic, analysis of layered composite plates and shells is demonstrated via several example problems. For comparison purposes, a two-dimensional finite element based on the Sanders shell theory with the von Karman (nonlinear) strains is also presented. The elements have the following features:

• Geometrically linear and nonlinear analysis • Static and transient analyses • Natural vibration (linear) analyses • Plates and shell elements • Arbitrary loading and boundary conditions • Arbitrary lamination scheme and lamina properties

The element can be used, with minor changes, in any existing general purpose programs.

The 3-D dimensional degenerated element has computational simplicity over a fully three-dimensional element, and the element accounts for full geometric nonlinearities in contrast to the 2-dimensional elements based on the Sanders shell theory. As demonstrated via numerical examples, the deflections obtained by the 2-D shell element deviate from those obtained by the 3-D element for deep shells. Further, the 3-D element can be used to model general shells that are not necessarily doubly-curved. For example, the twisted plates can not be modeled using the 2-D shell element. Of course, the 3-D degenerated element is computationally more demanding than the 2-D shell theory element for a given problem. In summary, the present 3-D element is an efficient element for the analysis of layered composite plates and shells undergoing large displacements and transient motion.