SUMMARYFormulation and numerical evaluation of a shear-flexible triangular laminated composite plate finite element is presented in this paper. The element has three nodes at its vertices, and displacements and rotations along with their first derivatives have been chosen as nodal degrees-of-freedom. Computation of element matrices is highly simplified by employing a shape function subroutine, and an optimal numerical integration scheme has been used to improve the performance. The element has satisfactory rate of convergence and acceptable accuracy with mesh refinement for thick as well as thin plates of both homogeneous isotropic and laminated anisotropic materials. The numerical studies also suggest that reliable prediction of the behaviour of laminated composite plates necessitates the use of higher order shear-flexible finite element models, and the proposed finite element appears to have some advantages over available elements.

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In this paper we describe a method for the optimum design of fiber reinforced composite laminates for strength by ranking. The software developed based on this method is capable of designing laminates for strength; which are subjected to inplane and/or bending loads and optionally hygrothermal loads. Symmetric laminates only are considered which are assumed to be made of repeated sublaminate construction. Various layup schemes are evaluated based on the laminated plate theory and quadratic failure criterion for the given mechanical and hygrothermal loads. The optimum layup sequence in the sublaminate and the number of such sublaminates required are obtained. Further, a ply-drop round-off scheme is adopted to arrive at an optimum laminate thickness. As an example, a family of 0/90/45/ -45 bi-directional lamination schemes are examined for different types of loads and the gains in optimising the ply orientations in a sublaminate are demonstrated.

A new curved triangular thin-shell finite element. based on nonconforming displacement fields, has demonstrated its effectiveness in a variety of numerical examples.R The patch test is applied to that element in the present paper. The element formulation is outlined, the special characteristics of the patch test for curved thin-shell elements are described, and that test is performed for the conditions of the inextensional bending, membrane stretching and rigid body displacements. Excellent results are obtained for element subtending angles up to 16 degrees.

A triangular cylindrical shell element based on discrete Kirchhoff theory is developed. It is a three-node, 27-degrees-of-freedom element using cubic polynomials for the tangential and normal displacement interpolations. The normal rotations are independently interpolated by quadratic polynomials. The formulation is capable of modelling general anisotropy representative of multi-layered, multi-directionally oriented composite construction. The numerical results indicate that the solution for 'displacements and stresses of cylindrical shells converge monotonically and rapidly to those based on deep shell theory.