Comparison of crash response between fuselage section and full-scale civil aircraft

The crashworthiness of an aircraft is the focus of its structural safety design and evaluation, and the relationship between the fuselage frame segment and the full-aircraft structure in terms of crash response has been one of the unresolved issues. In this paper, a vertical drop test with a fuselage frame segment with cabin door and a typical full-scale civil aircraft were conducted, and the results were compared. Then, a dynamic model of the full-aircraft crash was established and validated based on the experimental data from the full-aircraft crash. Furthermore, the model trimming method was used to obtain the crash dynamics models of the fuselage frame segment with a cabin door, the forward fuselage, and aft fuselage, and simulations were conducted under the experimental conditions. Based on the simulation results, differences between the crash responses of different fuselage frame segments and the full-aircraft structure were explored. The results show that the established full-aircraft crash dynamics model has high predictive accuracy, the predicted dynamic response of the structure is consistent with the experimental, and the deformation and movement process of the structure are consistent the experimental results, proving the accuracy of the model trimming method. The deformation of the floor structure and the floor acceleration of the fuselage frame segment with a cabin and the aft fuselage are less than those of the full-aircraft structure, the maximum deviation of the acceleration peak is 13.6%, and the damage modes are significantly different. For forward fuselage, the deformation is greater than that of the full-aircraft structure, but the floor acceleration is still less than that of the full-aircraft structure, with a maximum deviation of the acceleration peak reaching 17.2%. This reveals that the boundary conditions and energy input of the full-aircraft and the fuselage frame segment experiment pieces are fundamentally different, leading to significant differences in crash response. the verification and evaluation of aircraft crashworthiness, different verification methods and objects should be used for different verification targets. Using the full-aircraft structure for crashworthiness verification provides the most realistic results, while using the fuselage frame segment can verify the crash simulation model to support the simulation-based aircraft crashworthiness assessment. Additionally, fuselage segment with a cabin door and the aft fuselage are greatly affected by the contraction of the aircraft's nose and tail during a crash, and thus are not suitable as verification objects for aircraft crashworthiness. When using the forward fuselage as the verification object for aircraft crashworthiness, the end frame of the experiment needs to be strengthened to simulate actual boundary stiffness conditions as closely as possible.