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The design of deep submersible pressure hull's structural is one of the core technologies of submersible development of human history. Submersible pressure hulls with fiber-reinforced multilayer constructions have been developed in the recent years as substitutes for classical metallic ring-stiffened pressure hulls; strength and stability are its top priority. This paper investigates the optimum design of a composite elliptical deep-submerged pressure hull under hydrostatic pressure to minimize the buoyancy factor of the submersible pressure hull under constraints on the failure criteria and the buckling strength of the hulls to reach the maximum operating depth. The thickness and the fiber orientation angles in each layer, the radii of the ellipse, and stringers dimensions were taken as design variables and determined in the design process. The optimization procedures are performed using commercial finite element analysis software ANSYS. Additionally, a sensitivity analysis is performed to study the influence of the design variables on the structural optimum design. Results of this study provide a valuable reference for designers of underwater vehicles.

The pressure hull is the primary element of submarine, which withstands diving pressure and provides essential capacity for electronic systems and buoyancy. This study presents a numerical analysis and design optimization of sandwich composite deep submarine pressure hull using finite element modeling technique. This study aims to minimize buoyancy factor and maximize deck area and buckling strength factors. The collapse depth is taken as a base in the pressure hull design. The pressure hull has been analyzed using two composite materials, T700/Epoxy and B(4)5505/Epoxy, to form the upper and lower faces of the sandwich composite deep submarine pressure hull. The laminated control surface is optimized for the first ply failure index (FI) considering both Tsai–Wu and maximum stress failure criteria. The results obtained emphasize an important fact that the presence of core layer in sandwich composite pressure hull is not always more efficient. The use of sandwich in the design of composite deep submarine pressure hull at extreme depths is not a safe option. Additionally, the core thickness plays a minor role in the design of composite deep submarine pressure hull. The outcome of an optimization at extreme depths illustrates that the upper and lower faces become thicker and the core thickness becomes thinner. However, at shallow-to-moderate depths, it is recommended to use sandwich composite with a thick core to resist the shell buckling of composite submarine pressure hull.

Pressure hulls are one of the keys in the design of submarines. In order to improve the accuracy and efficiency of pressure hull structure, methods of optimizing it were studied. In the present study, an overview of the multi-objective optimization of intersecting cross elliptical pressure hulls (ICEPH) with and without the core layer under hydrostatic pressure was investigated in order to maximize buckling load capacity (λ) and minimize the buoyancy factor (B.F) of the ICEPH according to the design requirements. Five models were built, four composite models constructed from boron/epoxy (B(4)/5505) and carbon/epoxy composite (USN-150) with and without core layer. The fifth is a reference metallic model constructed from HY100. Criteria regarding failure for both composite and metal shells are considered as indications of optimization. Both Tsai-Wu and maximum stress failure criteria were employed to check the composite failure. The modeling and the multi-objective optimization were performed using ANSYS parametric design language (APDL) in order to determine mass, critical buckling load, and failure criteria. The results illustrated that carbon fiber-epoxy composite (USN-150) with a core layer is preferred for obtaining minimum weight, with an improvement ratio (IR) 64.314 % superior to that of a metallic pressure hull. By contrast, (boron/epoxy B(4)/5505) without a core layer is preferred to obtain a maximum buckling load.