Minimum Weight Design of Laminated Composite Plates for Postbuckling Performance

Minimum-weight design of simply-supported, symmetrically laminated, thin, rectangular, specially orthotropic laminated plates for buckling and postbuckling strength is investigated. The postbuckling analysis is based on an Marguerre-type energy method extended to generally orthotropic plates with a special consideration of the mode change in the postbuckling load regime. The failure load of laminates is calculated by the maximum strain failure criterion based on the in-plane strains. Design variables are individual layer thicknesses with specified fiber orientations and assumed to take only discrete values corresponding to multiples of the lamina thickness. The optimization with discrete valued design is achieved by introducing additional penalty terms, in the form of a sine function, to the regular pseudo-objective function of sequential unconstrained minimization technique (SUMT). The proposed optimization technique is applied to the design of rectangular laminates made up of 0, ± 45, 90 degree laminae with various aspect ratios loaded by axial compressive loads.