The effect of flexural/twist anisotropy on compression buckling of quasi-isotropic laminated cylindrical shells

It is widely recognised that the optimal lay-up to resist classical local buckling of a laminated shell subject to compression loading is one that is quasi-isotropic in nature. This ideal is difficult to achieve in practice due to manufacturing and additional design constraints. The minimum number of unidirectional layers, based on 0°, 90°, ±45° angles, is 48 - an example lay-up is shown. Balanced and symmetric laminates, that exhibit quasi-isotropic properties in-plane, are shown to give reduced buckling capacity depending on two factors. The first concerns the overall homogeneity of the laminate whilst the second is a function of the amount of flexural/torsional coupling. The former is shown to have the greater influence. In the absence of closed-form solutions these effects have been numerically quantified using finite element (FE) analysis techniques. Practical design guidelines are deduced.