Interactive buckling in composite cylinders

A novel and computationally effective procedure for the study of overall and local instabilities in composite ring stiffened shells subjected to hydrostatic pressure is presented. The key feature of the formulation employed is a judicious combination of the amplitude modulation technique and the asymptotic procedure for the interactive buckling analysis. A potential energy function is formulated in terms of a comparatively small number of degrees-of-freedom, viz. the degrees-of-freedom depicting the amplitude modulating function and a scaling factor of the overall buckling mode. As a result of the amplitude modulation, there arise in the potential energy function, non-vanishing cubic interactive terms which control the process of mode interaction. Imperfection-sensitivity under coincident buckling is examined. It appears that a 50% reduction of the buckling capacity must probably be allowed for as a result of modal interaction under near-coincident buckling. The optimality under interactive buckling is also examined with the total volume of the material kept constant and the critical stress ratio varied.