Crash responses of a blended-wing-body civil aircraft at different vertical velocities

Significant structural and layout disparities exist between the blended wing body (BWB) civil aircraft and conventional cylindrical fuselage metal aircraft. These differences render the impact resistance characteristics of the non-circular fuselage structure and the injury mechanisms for occupants unclear. To address this, a 460-seat BWB aircraft model was developed based on the pultruded rod stitched efficient unitized structure (PRSEUS) proposed by the National Aeronautics and Space Administration (NASA). The aircraft features a wingspan of 80 meters, a range of approximately 16,000 km, a cruising Mach number of 0.85, and a cruising altitude of 11 000 m. Three typical loading conditions were employed to evaluate the strength and stiffness of the BWB structure: critical maneuvering loads (2.5g positive overload and −1.0g negative overload) and cabin pressurization loads (double the cabin pressurization load). Through iterative structural design optimization, the model was confirmed to meet these typical loading requirements while demonstrating sufficient safety margins. The model incorporated all major structural components of the BWB configuration, including skin, frames, stringers, cargo floor, cabin floor, support columns, and fuselage ribs. In the finite element modeling process, elements with minimal influence on the crash response were reasonably simplified to reduce computational complexity. For instance, the outer wings and engines were simplified as concentrated mass points, and the cabin seats and passengers were modeled as concentrated masses fixed to the seat rails. The primary structural components, such as the skin, stringers, floor, and floor beams, were constructed from AS4 carbon fiber composite laminates and modeled using shell elements. The pultruded rods were made of AS4 carbon fiber composite and modeled using beam elements. The foam core of the frames and fuselage ribs were made of Rohacell-110-WF foam material and modeled using solid elements. The remaining structures were made of 7075 aluminum alloy and modeled using shell elements. The final model had a total mass of 162.87 tons and consisted of 2 679 991 elements. Five vertical impact velocities ranging from 7.92 to 9.14 m/s were selected to analyze the cabin space integrity, acceleration response of the cabin floor, and the impact characteristics of the primary load-bearing structures. The results indicate that the cabin area of the lift-body fuselage remains largely intact under the different impact velocities. The primary damage occurs below the cabin floor, with compressive damage concentrated in the lower structures of the middle and aft fuselage. The survivable space is preserved. Compared to a round-section fuselage, the deformation of the BWB frames is relatively small, and upward bulging is not significant, making it challenging to form effective plastic hinges. During the crash, the acceleration load distribution of the blended wing body-integrated aircraft exhibits a decreasing trend from the central aisle to the sides of the fuselage, with peak acceleration loads being higher at the central aisle. Under all five crash conditions, passenger injury levels at various cabin positions fall within the serious but acceptable and safe regions. Regarding structural energy absorption, the frames are identified as the primary energy-absorbing structures, followed by the fuselage ribs. However, the cargo pillars do not effectively crush and absorb energy. For future crashworthiness design of BWB civil aircraft, the cargo structure should be a key consideration.