Approximate bifurcation load of short thin-walled laminate plate structures with imperfection

The bifurcation buckling load can be determine solving a linear eigenproblem of buckling. If the structure is not perfect, the effect of bifurcation doesn’t occur. So, how to estimate a value of the lowest buckling load of the real structure? A methodology for determination of the lowest buckling load of a real structure with initial imperfection using a post-buckling path is presented. The investigation is performed for a Z-column made of carbon-epoxy laminate. The amplitude of initial imperfection is small less than half of the walls thickness. The column is simply supported on both ends. All calculations are performed by the finite element method and Koiter’s method. A plate model of the thin-walled structure has been applied. First, an eigenvalue buckling problem is solved to determine bifurcation loads. Next, post-buckling equilibrium paths for the plate structures are determined to calculate the lowest approximate bifurcation loads by the P-w and P-w2 methods, the inflection point method and the Koi...