Buckling optimization of laminated cylindrical panels subjected to axial compressive load Hsuan-Teh Hu * , Jiing-Sen Yang Department of Civil Engineering and Sustainable Environment Research Center, National Cheng Kung University, 1 University Road, Tainan 701, Taiwan, ROC Available online 6 October 2006 Abstract The buckling resistance of fiber-reinforced laminated cylindrical panels with a given material system and subjected to uniaxial com- pressive force is maximized with respect to fiber orientations by using a sequential linear programming method together with a simple move-limit strategy. The significant influences of panel thicknesses, curvatures, aspect ratios, cutouts and end conditions on the optimal fiber orientations and the associated optimal buckling loads of laminated cylindrical panels have been shown through this investigation. Ó 2006 Elsevier Ltd. All rights reserved. Keywords: Buckling; Optimization; Laminated cylindrical panels; Finite element analysis 1. Introduction The use of fiber-reinforced laminated cylindrical panels in aerospace and mechanical industries has increased rapidly in recent years. The composite cylindrical panels in service are commonly subjected to various kinds of compressive loads which may cause buckling. Hence, structural instability becomes a major concern in safe and reliable design of the composite cylindrical panels. The buckling resistance of lam- inated cylindrical panels depends on end conditions, lamina- tion parameters such as ply orientations [1–6], and geometric variables such as thicknesses, curvatures, aspect ratios and cutouts [3,5–10]. Therefore, for composite cylindrical panels with a given material system, geometric shape and end con- dition, the proper selection of appropriate lamination to realize the maximum buckling resistance of the cylindrical panels becomes a crucial problem. Research on the subject of structural optimization has been reported by many investigators [11]. Among various optimization schemes, the method of sequential linear pro- gramming has been successfully applied to many large scale structural problems [12,13]. Hence, linearization of nonlin- ear optimization problems to meet requirements for itera- tive applications of a linear programming method is one of the most popular approaches to solve the structural opti- mization problem. In this investigation, buckling optimization of symmetri- cally laminated cylindrical panels with respect to fiber ori- entations is performed by using a sequential linear programming method together with a simple move-limit strategy. The critical buckling loads of composite cylindri- cal panels are calculated by the bifurcation buckling anal- ysis implemented in the ABAQUS finite element program [14]. In this paper, the bifurcation buckling analysis, the constitutive equations for fiber-composite laminate and the optimization method are briefly reviewed first. Then the influence of end conditions, curvatures, aspect ratios, thicknesses and cutouts on the optimal fiber orientations and the associated optimal buckling loads of composite cylindrical panel is presented. Finally, important conclu- sions obtained from this study are given. 2. Bifurcation buckling analysis In the finite-element analysis, a system of nonlinear alge- braic equations results in the incremental form: 0263-8223/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.compstruct.2006.08.025 * Corresponding author. Tel.: +886 6 2757575x63168; fax: +886 6 2358542. E-mail address: hthu@mail.ncku.edu.tw (H.-T. Hu). www.elsevier.com/locate/compstruct Composite Structures 81 (2007) 374–385