QUALITATIVE ERRORS IN LAMINATED COMPOSITE PLATE MODELS

The presence of 'qualitative' errors, i.e. errors that misrepresent the sign or direction of deformation in a problem, is identified in laminated composite plate elements. The errors are found to be due to the presence of parasitic shear terms introduced when an element is formed using incompatible polynomials. Although these modelling errors can be removed from four-node elements with reduced order Gauss quadrature integration, they cannot be removed from eight-node elements by this method. However, procedures based on a physically interpretable notation are available to remove these errors from individual elements with any number of nodes. The procedures for correcting the laminated composite plate elements can be used to remove parasitic shear and spurious zero energy modes from other types of elements. Three examples are used to demonstrate the developments.