Fiber orientation effects on the buckling behaviour of imperfect composite cylinders

A theoretical and numerical investigation on the influence of the fibre orientation on the buckling behaviour of composite cylinders is presented. Composite cylinders with different laminations and subject to axial compression are examined. The results show the great influence of fibre orientation on the buckling load and highlight the presence of a high number of almost coincident buckling modes in the cases of quasi-isotropic lay- up or of a particular value of the fibre angle. In the latter case the initial slope of the post-buckling branch has a very high negative value and the cylinders consequently result to be very imperfection sensitive. This confirms the fact that any optimisation process should include an imperfection sensitivity parameter.