Post-buckling behavior of composite laminated plates under end shortening and pressure loading, using two versions of finite strip method H.R. Ovesy * , S.A.M. GhannadPour, G. Morada Aerospace Engineering Department, Amirkabir University of Technology, Hafez Avenue, Tehran 15875-4413, Iran Available online 8 June 2006 Abstract Two different versions of finite strip method, namely spline and semi-analytical methods, are developed for analyzing the geometri- cally non-linear response of rectangular composite laminated plates of arbitrary lay-up to progressive end-shortening in their plane and to pressure loading. The plates are assumed to be thin so that the analysis can be carried out based on the classical plate theory. The in- plane lateral deflection t is allowed at the loaded ends of the plate, whilst the lateral expansion of the unloaded edges is either free or completely prevented. Geometric non-linearity is introduced in the strain–displacement equations in the manner of the von Karman assumptions. The formulations of the finite strip methods are based on the concept of the principle of the minimum potential energy. A number of applications involving isotropic plates, symmetric and unsymmetric cross-ply laminates are described to investigate the effects of pressure loading. The comparison between the two sets of results obtained by different finite strip methods is very good. The study of the results revealed that the response of the laminates is significantly influenced by the application of the normal pressure loading. Particularly, the response of unsymmetric laminates is strongly affected by the sign of the normal pressure loading. Ó 2006 Elsevier Ltd. All rights reserved. Keywords: Geometric non-linear; Post-buckling; Pressure load 1. Introduction Prismatic plates and plate structures are increasingly used as structural components in various branches of engi- neering, chief of which are aerospace and marine engineer- ing. These structures are often employed in situations where they are subjected to in-plane compressive loading. Thus, it is important to accurately predict the buckling and post-buckling behavior of such structures. In aero- space, in particular, the quest for efficient, light-weight structures often leads to allowing for the possibility of local buckling and post-local-buckling at design load levels. The post-local-buckling behavior of elastic plates or plate struc- tures is a geometric non-linear problem. The finite strip method [1] (FSM) is well suited to the accurate and efficient analysis of both single rectangular plates and complicated prismatic plate structures. In the field of linear buckling and vibration analysis, the method has been developed extensively by Dawe and co-workers [2–6] for the analysis of complicated plate structures formed of composite lami- nated material having very general material properties. Such development relates to analyses based on the use of both classical plate theory (CPT) and first-order shear deformation plate theory (SDPT). In the context of CPT, and for homogeneous materials only, the finite strip method has been employed in geometrically non-linear analyses by Graves-Smith and Sridharan [7,8] and Han- cock and Bradford [9,10]. These works are concerned with the prismatic plate structures as well as single plates, and have concentrated on post-local-buckling behaviour. Aziz- ian and Dawe [11,12] have included through-thickness shear effects in geometrically non-linear finite strip analysis 0263-8223/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.compstruct.2006.04.006 * Corresponding author. Tel.: +98 21 66405032/64543011; fax: +98 21 66959020. E-mail address: Ovesy@aut.ac.ir (H.R. Ovesy). www.elsevier.com/locate/compstruct Composite Structures 75 (2006) 106–113