UNCERTAINTY ANALYSIS OF A CROSS-PLY COMPOSITE CYLINDER SUBJECT TO EXTERNAL PRESSURE BY CONVEX MODELING

摘要

Quite often the values of the elastic constants of composite materials can be estimated with some error due to manufacturing imperfections, defects and misalignments. This introduces some level of uncertainty in the computation of the buckling loads, frequencies, etc. In the present study an ellipsoidal convex model is employed to study the buckling of long cross-ply cylinders subject to external pressure with the material properties displaying uncertain-but-bounded variations around their nominal values. This approach determines the lowest buckling pressure and as such provides a conservative answer. Method of Lagrange multipliers is applied to compute the worst-case variations of the elastic constants and an explicit expression is obtained for the critical buckling pressure for a given level of uncertainty. Expressions for the relative sensitivities of the buckling pressure to uncertain elastic constants are derived.