OPTIMAL-DESIGN OF GENERAL STIFFENED COMPOSITE CIRCULAR-CYLINDERS FOR GLOBAL BUCKLING WITH STRENGTH CONSTRAINTS

A design strategy for optimal design of composite grid-stiffened cylin ders subjected to global and local buckling constraints and strength c onstraints was developed using a discrete optimizer based on a genetic algorithm. An improved smeared stiffener theory was used for the glob al analysis. Local buckling of skin segments were assessed using a Ray leigh-Ritz method that accounts for material anisotropy. The local buc kling of stiffener segments were also assessed. Constraints on the axi al membrane strain in the skin and stiffener segments were imposed to include strength criteria in the grid-stiffened cylinder design. Desig n variables used in this study were the axial and transverse stiffener spacings, stiffener height and thickness, skin laminate stacking sequ ence and stiffening configuration, where stiffening configuration is a design variable that indicates the combination of axial, transverse a nd diagonal stiffener in the grid-stiffened cylinder. The design optim ization process was adapted to identify the best suited stiffening con figurations and stiffener spacings for grid-stiffened composite cylind er with the length and radius of the cylinder, the design in-plane loa ds and material properties as inputs. The effect of having axial membr ane strain constraints in the skin and stiffener segments in the optim ization process is also studied for selected stiffening configurations . (C) 1998 Published by Elsevier Science Ltd. All rights reserved.