Analysis Design and Optimization of Non-cylindrical Fuselage for Blended-Wing-Body (BWB) Vehicle

Initial results of an investigation towards finding an efficient non-cylindrical fuselage configuration for a conceptual blended-wing-body flight vehicle were presented. A simplified 2-D beam column analysis and optimization was performed first. Then a set of detailed finite element models of deep sandwich panel and ribbed shell construction concepts were analyzed and optimized. Generally these concepts with flat surfaces were found to be structurally inefficient to withstand internal pressure and resultant compressive loads simultaneously. Alternatively, a set of multi-bubble fuselage configuration concepts were developed for balancing internal cabin pressure load efficiently, through membrane stress in inner-stiffened shell and intercabin walls. An outer-ribbed shell was designed to prevent buckling due to external resultant compressive loads. Initial results from finite element analysis appear to be promising. These concepts should be developed further to exploit their inherent structurally efficiency. Introduction In revolutionary Blended-Wing-Body (BWB) megatransport concepts with non-cylindrical liftingbody fuselage and in conformal shaped propellant tanks of reusable launch vehicles, the pressurized structure must be designed to resist internal pressure and compression due to overall bending. These loads combine in a nonlinear manner to induce severe deformation, and high stresses, that might necessitate significant structural weight penalty. In addition, resulting deformation of aerodynamic surface could significantly affect performance advantages provided by lifting body. This problem was investigated for Airbus type elliptic-section composite fuselage as well as for BWB and X33 with special sandwich composite skin and metal honeycomb core. • In previous BWB studies, effects of cabin shape, and volume were investigated, from a baseline configuration using an aerodynamic based optimization scheme, but structural design with internal pressure or • Associate Fellow, **Fellow, AIAA buckling issues were not addressed. In another conceptual structural analysis, several promising non-cylindrical fuselage configurations were identified but no optimization study was conducted. This paper presents additional sizing, analysis, design and optimization results towards finding an efficient non-cylindrical BWB configuration, considering both internal pressure and compressive load including buckling stability. Initially four idealized deep sandwich and ribbed shell configurations were analyzed and optimized with stress and buckling constraints. These panels represented a critical upper surface panel section, as shown in Fig. 1.