Numerical analysis of collapse load and specific strength for moderate-walled Ti6Al4V-laminate composite submersible vessel under external hydrostatic pressure

The effects of geometrical imperfections on the collapse load and specific strength of moderate-walled submersible vessel made of Ti6Al4V-laminate composites and Ti6Al4V alloy, respectively, have been investigated in this study. Two kinds of imperfections, which are the initial ovality along cross -section direction and the winding-induced waves along longitudinal symmetric axis, are considered. Two numerical analyses including the non-linear finite element (FE) and elastic-plastic buckling analysis are performed by the commercial software MSC Marc/Mant 2005. The obtained results indicate that initial imperfections have an obvious influence on the collapse loads of both the Ti6Al4V-laminate composite submersible vessel and the Ti6Al4V one. The collapse load is mainly governed by the elastic-plastic buckling critical load, which is conservative and safe for a vessel to bear the admissible failure load under the deepwater. Moreover, the Ti6Al4V-laminate composite submersible vessel has a better capability to resist imperfections than the Ti6Al4V one.