Egg–shaped Type V composite hydrogen vessels: Buckling and first burst assessment for deep–sea applications

Egg-shaped shells offer superior hydrodynamic performance and lower imperfection sensitivity than spherical shells, yet their burst behavior under internal pressurization has never been assessed. This study evaluates egg-shaped Type V composite hydrogen storage vessels for deep-sea service under external hydrostatic pressure (worst-case buckling) and internal pressure (hydrogen storage operation). Ten configurations (SI = 0.5–0.95) were modeled in ABAQUS with three composite materials and four symmetric layups. Under external pressure, Carbon T-700/Epoxy with [0 3 /90 3 ]s achieved 72.24 MPa at SI = 0.95, with collapse depths up to 6515 m. Under internal pressure — assessed here for the first time for egg-shaped vessels — burst capacity increased by 18.3% from SI = 0.5 to 0.9, reaching over 90% of the sphere's burst capacity and exceeding the cylinder by up to 20%, confirming competitive burst performance alongside the geometry's known buckling advantage over cylinders. The best-performing layup reverses between loading conditions, requiring dual-load design. • First burst assessment of egg–shaped composite vessels under internal pressure. • Buckling pressure increases monotonically with Shape Index up to 72.24 MPa. • Egg at SI = 0.9 reaches 90% of sphere burst while exceeding cylinder by 20%. • Best-performing layup reverses between external and internal loading conditions. • SI = 0.9–0.95 recommended as dual–loading design window for hydrogen AUVs.