Post-buckling optimization of bending-induced variable stiffness composite cylinders considering worst geometric imperfections

Abstract

Variable stiffness (VS) composite cylinders have attracted much more attention in the aerospace industry, due to their significantly improved mechanical properties. Most of the existing studies on the optimization of VS composite cylinders are based on linear buckling analysis, without considering the imperfection sensitivity and ignoring the potential of the non-linear post-buckling bearing of cylindrical shells. Therefore, the imperfection sensitivity analysis of VS composite cylinders under bending load is performed in the non-linear post-buckling regime. It is illustrated that the optimized result based on the linear buckling analysis is not robust, if imperfections are taken into account. Moreover, an optimization framework considering imperfection sensitivity is established, wherein the Worst Multiple Perturbation Load Approach (WMPLA) is used to calculate the lower-bound limit moment of composite cylinders. The critical moment of the optimized result with the worst imperfections has an improvement of 13.81%, and the knockdown factor (KDF) is improved by 27.27%. It is demonstrated to be necessary to consider the imperfection sensitivity based on the non-linear post-buckling analysis during the optimization of VS composite cylinders, and the considerable performance with improved anti-imperfection ability can be realized by tailoring the fiber orientation of VS cylinders.