Collapse behavior of egg-shaped external pressure vessels with sandwich structure

This study delves into the collapse behavior of egg-shaped vessels with a sandwich structure under external hydrostatic pressure. The pressure vessel is the most critical load-bearing structure of a submersible. The study presents an egg-shaped vessel with a sandwich structure that comprises two thin stainless-steel layers, a resin core, and two closed plates. The primary function of this structure is to withstand deep-sea hydrostatic pressure, thereby ensuring a safe operational environment underwater. Numerical simulations have been performed for collapse assessment and parametric analysis. A semi-analytical formula has also been derived to predict the vessel’s collapse load. The results reveal that the sandwich structure markedly increases the vessel’s collapse load and reduces its defect sensitivity compared with values observed for single-layer egg-shaped vessels. The real-scale vessel has then been manufactured and tested through geometric measurements, external hydrostatic tests, and numerical simulations. The experimental results are compared with theoretical and numerical results to validate the feasibility of the numerical model and semi-analytical formula. The fabricated vessel demonstrates favorable formation precision and compressive structural efficiency. These new findings are precursor to advanced design of safer and more resilient subsea structures.