Delamination buckling and postbuckling in composite cylindrical shells under external pressure

Composite cylindrical shells and panels are widely used in aerospace structures. These are often subjected to defects and damage from both in-service and manufacturing events. Delamination is the most important of these defects. This paper deals with the computational modelling of delamination buckling and postbuckling of laminated composite cylindrical shells subjected to external pressure. The use of three-dimensional finite elements for predicting the delamination buckling and postbuckling of these structures is computationally expensive. Here, the combined double-layer and single-layer of shell elements are employed to study the effect of delamination on the global load-carrying capacity of such systems under external pressure. It is shown that through-the-thickness delamination can be modelled and analysed effectively without requiring a great deal of computing time and memory. A parametric study is carried out to investigate the influence of the delamination size, orientation and through-the-thickness position of a series of laminated cylinders. The effects of material properties and stacking sequence are also investigated. Some of the results are compared with the corresponding analytical results. It is shown that ignoring the contact between the delaminated layers can result in wrong estimations of the critical buckling loads in cylindrical shells under external pressure.