BUCKLING ANALYSIS AND DESIGN OPTIMIZATION FOR GRID-STIFFENED COMPOSITE STRUCTURES

摘要

An improved smeared stiffener theory for a stiffened structure that includes skin-stiffener inter-action effects is presented. The skin-stiffener interaction is accounted for by computing the bending and coupling stiffness matrices due to the stiffener and the skin in the skin-stiffener region about a shifted neutral axis at the stiffener. The panel global buckling results obtained using the improved smeared theory compare well with results from finite element analysis. A design strategy developed using a discrete optimizer for optimal design of composite grid-stiffened panels and cylinders subjected to global and local buckling constraints developed is presented. The improved smeared stiffener theory is used for the global buckling analysis of the panels and cylinders and the local buckling of skin segments is assessed using a Rayleigh-Ritz method that accounts for material anisotropy and transverse shear flexibility. The design optimization process is applied to identify the lightest-weight grid-stiffened configuration and stiffener spacing for panels and cylinders subjected to combined inplane loading conditions.