Anisotropic effects in the compression buckling of laminated composite cylindrical shells

This paper addresses two aspects of buckling relevant to design. The first describes the preliminary experimental results that validate the presence of a newly reported spiral buckling mode; whilst the second concerned the effects of extension/twist anisotropy on the buckling loads of cylindrical shells under compression. The influence of designing laminates with antisymmetric lay-ups in comparison with a symmetrical lay-up is also investigated. Antisymmetric quasi-isotropic laminates, based on 0, 90 and ±45° angles produces greater buckling loads than the equivalent symmetric lay-up. Whilst all anisotropic coupling effects appear to lower the buckling loads, a laminate that is 48 plies thick is necessary to eliminate them in thin-walled shells. Such a laminate is at least 6 mm thick. Many designs require thinner laminates, and in so doing, mitigate the need for guidelines on efficient anisotropic lay-ups. Neglecting the effect of prebuckling deformation, it is found that extension/twist coupling is less deleterious than flexural/twist coupling in this respect. Therefore, antisymmetric laminates appear preferable for initial buckling of quasi-isotropic laminates.