INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING Int. J. Numer. Meth. Engng 2004; 60:1237–1257 (DOI: 10.1002/nme.1005) A new triangular element to model inter-laminar shear stress continuous plate theory A. Chakrabarti 1 and A. H. Sheikh 2, ∗, † 1 Department of Civil Engineering, Jalpaiguri Government Engineering College, Jalpaiguri, West Bengal 735102, India 2 Department of Ocean Engineering and Naval Architecture, Indian Institute of Technology, Kharagpur, West Bengal 721302, India SUMMARY An efficient triangular element based on an inter-laminar shear stress continuous plate theory is developed and applied to the analysis of composite and sandwich plates under different situations to study the performance of the element. The plate theory represents parabolic through thickness variation of transverse shear stresses where the continuity condition of these stresses are satisfied at the layer interfaces. It also satisfies transverse shear stress free condition at the top and bottom surfaces of the plate. The most attractive feature of the plate theory is that the basic unknowns are same as those used in first-order shear deformation theory. The only problem lies with this elegant plate theory is found in its finite element implementation, as it requires C 1 continuity of transverse displacement at the element interfaces. This is a well-known problem of thin plate elements, which is also found in some other refined plate theories. Although there are some elements based on these refined plate theories but the number of such elements is very few and they possess certain drawbacks in general. Keeping these aspects in view, an attempt has been made in this study to develop a six-noded triangular element having equal degrees of freedom at each node. Copyright  2004 John Wiley & Sons, Ltd. KEY WORDS: composite and sandwich plates; continuous transverse shear stress; triangular plate element; refined higher-order shear deformation theory; inter-elemental continuity 1. INTRODUCTION The development of an appropriate mathematical model for the representation of the behaviour of fibre-reinforced composite laminates and its application has drawn a considerable amount of attention in the last two decades. One of the important features of this material is that it is weak in shear i.e. the value of shear modulus is sufficiently low compared to that of extensional rigidity. Owing to this, the effect of shear deformation becomes quite significant ∗ Correspondence to: A. H. Sheikh, Department of Ocean Engineering and Naval Architecture, Indian Institute of Technology, Kharagpur 721302, West Bengal, India. † E-mail: hamid@iitkgp.ernet.in Received 15 July 2002 Revised 24 September 2003 Copyright  2004 John Wiley & Sons, Ltd. Accepted 24 September 2004