Thermomechanical Responses of Cryogenic Composite Pressure Vessels with Different Dome Aspect Ratios.

Large-scale metal-lined composite overwrapped pressure vessels are promising for cryogenic liquid oxygen storage, but their response is governed by the interaction among dome geometry, thermal mismatch and internal pressure. This study investigates the influence of dome aspect ratio (DAR), defined as the ratio of the major to minor semi-axis of an ellipsoidal dome, on vessel thermomechanical behavior. Six DAR values from 1.25 to 2.50 were analyzed using a three-dimensional finite element model with temperature-dependent properties of Type 304 stainless steel and T700-grade carbon/epoxy. Three loading conditions were considered including 1.0 MPa internal pressure at 293 K, cooling from 293 to 90 K, and pressurization at 90 K. At 293 K, increasing DAR intensified stress localization near the dome-cylinder transition. Cryogenic cooling produced incompatible free deformations between the liner and overwrap, generating substantial constrained thermal stresses after bonding. Subsequent pressurization further increased the liner stress but partly offset the cooling-induced compressive stress in the overwrap. Under cryogenic and combined loading, DAR had little influence on the central cylindrical section, but markedly changed the stress magnitude, sign and localization in the domes and transition regions. These findings indicate that dome shapes for cryogenic vessels should not be selected solely from room-temperature pressure-based conclusions, because thermal mismatch and cryogenic pressurization can fundamentally alter the structural response.