Research on the Crash Response of Blended-Wing-Body Civil Aircraft at Different Vertical Velocity

Significant differences in structure and layout exist between the Blended Wing Body (BWB) civil aircraft and conventional cylindrical fuselage metal aircraft. As a result, the impact resistance characteristics of the non-circular fuselage structure and the injury mechanisms for occupants remain unclear. A 460-seat BWB aircraft model was developed based on the Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) proposed by National Aeronautics and Space Administration (NASA). The aircraft has 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 meters. Three typical loading conditions—critical maneuvering loads (2.5g overload and -1.0g overload) and cabin pressurization loads (Double the cabin pressurization load)—were used as input conditions to evaluate the strength and stiffness of the BWB structure. Through iterative structural design optimization, the model was confirmed to meet the typical loading requirements and demonstrated sufficient safety margins. The model included all major structural components of the BWB configuration, such as skin, frames, stringers, cargo floor, cabin floor, support columns, and fuselage ribs. In the finite element modeling process, from the perspective of reducing the amount of calculation, the part of the crash response that had less influence was reasonably simplified, such as the outer wings and engines were simplified as concentrated mass points. The cabin seats and passengers were also modeled as concentrated masses and fixed to the seat rails. The primary structural components of the BWB aircraft model, including 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 26 ft/s to 30 ft/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 show that the cabin area of the lift-body fuselage remains largely intact under 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 BWB frames is relatively small, and the upward bulging is not significant, making it difficult to form effective plastic hinges. During the crash, the acceleration load distribution of the blended wing body-integrated aircraft shows 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 in various cabin positions fall within the serious but acceptable and safe regions. Regarding structural energy absorption, the frames serve as the primary energy-absorbing structures, followed by the fuselage ribs. However, the cargo pillars do not effectively crush and absorb energy. For the future crashworthiness design of BWB civil aircraft, the cargo structure should be a key consideration.