This study is intended to develop a rationale for assessing the mechanical behavior and strength of composite tubes used in offshore applications. It is further intended to study the influence of geometric imperfections and material defects on the capacity of such tubes under combined loads. Emphasis is placed on the performance under external pressure although the effects of internal pressure and axial tension are also studied. A numerical procedure is developed for delamination buckling and growth analysis. A cross-section finite element having a partially-separated layer is proposed. Nonlinear geometry and material formulations are implemented. The accuracy of the model predictions is verified against available experimental data. Parametric studies of the effects of delamination buckling an growth are conducted. Reduction in collapse pressure occurs due to these phenomena. Critical combinations of delamination thickness and length are found to exist. Furthermore, a critical delamination location relative to the ovalization orientation is determined. Finally, the effect of thick delaminations on the collapse pressure is investigated.