Design and Buoyancy Compensation Performance of a Rigid-Flexible Composite Pressure Hull With a Sandwich Structure for Underwater Gliders

The pressure hull is the main buoyancy component of underwater gliders (UGs), and its volume change during upward and downward gliding has a great influence on the motion performance and endurance of UGs. To improve the buoyancy compensation ability of the pressure hull, this study designs a rigid-flexible composite pressure hull with a sandwich structure (simplified as sandwich hull), which consists of a rigid outer layer, a flexible middle layer, and a rigid inner layer. The differential equations for axial and radial deflections of the sandwich hull under external pressure are deduced based on the thin shell theory, and the distribution of deformation and pressure on the three layers is obtained. The objective function for the buoyancy change of the sandwich hull is established, and the hull parameters are optimized with the genetic algorithm and then verified by the pressure test. The optimized sandwich hull shows better buoyancy compensation performance than the traditional rigid one, with more than 19% reduction in the buoyancy change per unit volume. The designed sandwich hull is applied to the theoretical model of a “PETREL” UG to replace the traditional rigid hull, and the calculation results show that no other buoyancy compensation and attitude adjustment are required during the gliding process down to 1000 m.