A NATURAL TRIANGULAR LAYERED ELEMENT FOR BENDING ANALYSIS OF ISOTROPIC, SANDWICH, LAMINATED COMPOSITE AND HYBRID PLATES

A three-node layered triangular element constrained to comply with an assumed linear direct strain distribution across its thickness and including transverse shear deformation is presented for bending analysis of plates. The element, which bears the name LACOT, is of the facet type intended also as a first approximation for the structural analysis of shells, and is based on the theoretical foundation provided by the ASKA element TRUMP[5]. Concepts of the natural mode and matrix displacement methods together with decomposition and lumping ideas based on appropriate kinematic idealizations were combined to establish its natural and cartesian stifness matrices. The triangular element is free of shear locking, ensures zero strains under rigid body motion, and converges naturally to the true state of deformation. It is capable of analyzing layered structures including isotropic, sandwich, laminated composite and hybrid plates, and by treating such a spectrum of material systems provides an eloquent unification and generalization. Natural shear correction factors which are computed automatically adjust the plate's transverse shear stiffness and assist in the accurate computation of the through the thickness shear stresses. Numerical examples and comparisons with analytic or other available solutions indicate its accurate formulation and its potential for structural analysis of plates and shells.