The effect of imperfect boundary conditions on the collapse behavior of anisotropic shells

A rigorous solution is presented for the case of sti€ened anisotropic shells with general imperfections under combined axial compression, internal or external pressure and torsion. Donnell type equations are used to describe the behavior of the layered composite shell. The sti€eners are represented by smeared theory and for the discrete end rings, CohenÕs ring equations are used. The circumferential dependence is eliminated by a truncated Fourier series. The resulting 2-point boundary value problem is solved numerically via the ``parallel shooting methodʹʹ. The nonlinear collapse behavior is studied using di€erent combinations of axisymmetric and asymmetric imperfections. Comparison with Koiter type imperfection predictions display the range of validity of the asymptotic results. It is shown that besides initial geometric imperfections also nonuniform harmonically varying boundary conditions can have severe degrading e€ect on the load carrying capacity of anisotropic shells.