An overall view of laminate theories based on displacement hypothesis

With the use of a recursive technique, this paper presents an overall comparison of laminate theories based on displacement hypothesis. A generalized polynominal form is used to unify the displacement hypothesis. Both theories available in the literature and inferable from the existing theories-are addressed. Firstly, Shear Deformation Theories are recognized to give good results for in-plane stresses but poor results for interlaminar stresses. However, Layerwise Theories give excellent results for both global and local distributions of displacement and stress (both in-plane and out-of-plane). A compromising theory, the Generalized Zigzag Theory, is presented. Due to its success in laminate analysis, a series of Quasi-layerwise Theories are presented. Unfortunately, a physical impossibility - coordinate dependency - takes place. It then requires a Global-Local Superposition Technique to formulate the laminate theories. By examining the results of Superposition Theories, it is concluded that the completeness of the terms is very important. Based on a Hypothesis for Double Superposition, this study presents three Double-Superposition Theories. They are verified to give excellent numerical accuracy, along with computational efficiency, when compared with elasticity solutions.