Research On Design And Evaluation Method Of Airframe Structural Crashworthiness Based On Occupants Survivability

Crashworthiness refers to the ability of an airplane to protect the safety of an occupant in the event of a crash.The two main design goals of the pendency are to limit the impact imparted to the occupant to ensure that the occupant’s load during the crash is less than its tolerated limit,and to maintain the integrity of the fuselage structure to ensure minimal safety space and safe evacuation.You can pay a smaller body structure weight cost to improve the occupants’ survivability significantly in the crash by improving the aircraft’s fuselage structure and cabin layout and internal facilities to improve the aircraft’s crashworthiness.Therefore it is of great theoretical significance and engineering application value to carry out the research on the crashworthiness design method of aircraft fuselage structure based on personnel survivability in the development stage of China’s large aircraft project.This thesis takes the crashworthiness design of a certain type of aircraft fuselage structure as the research background.Based on analysis of domestic and overseas related research results of crashworthiness,a thorough study on the meaning,the border settings,certification method,personnel injury assessment method of the aircraft’s fuselage structure of crashworthiness and airworthiness has been made.The personnel injury assessment method is combined with finite element analysis techniques.Personnel survivability is the design goals.From the aspects of the crashworthiness design,destruction mode control,structural optimization of the metal fuselage structural parts,and the crashworthiness modeling and evaluation of the composite fuselage structure,the systematic research on the crashworthiness of civil aircraft fuselage structure is carried out.The research work can be summarized as follows:Through the study of the airworthiness requirements,the Advisory Circulars(AC),interpretation clause and other technical documents related to the crashworthiness,the requirements of the airworthiness regulation and the injury indexes of the human body are analyzed.According to the concept of survivable accidents,the requirements of the transport aircraft design and verification are proposed.The selection method of the boundary conditions of the fuselage structure crash load is analyzed by combining the experimental research results in the fuselage crash test and the accumulative frequency distribution of the survivable accidents of civil aircraft.Based on the analysis of human injury index,considering overload and duration on the crew,the crashworthiness design and verification method of aircraft fuselage structure based on personnel survivability is proposed.By studying the nonlinear problem,material mechanics characteristics and modeling analysis method in the collision process,the basic principle and analysis method of modeling for the aircraft fuselage structure are summarized,and the simulation data processing method of the crash is summarized.According to the relevant numerical simulation platform,the common problems and processing methods of modeling for the aircraft fuselage structure including unit selection,meshing,contact setting,material model selection,unit system and boundary condition selection are expounded.The modeling and analysis method of the interior seat system of the fuselage structure,coupling function of the passenger seat restraint system and the fuselage with dummy are discussed.Taking the numerical simulation results of the crash of the fuselage with the dummy-seat system as an example,the assessing method of the crash performance is described in combination with the human injury index.According to the crashworthiness design requirements of a certain type of metal aircraft fuselage,the influence of the parameters such as the angle of the strut,the structure of the strut and the weight of the fuselage on the crashworthiness and the failure mode of the fuselage structure were investigated.Combined with the assessment index of crashworthiness and airworthiness damage,the damage of occupants under different crash conditions was evaluated.Based on the above research results,the design idea and the optimal design scheme of the crashworthiness design are put forward by changing the fuselage structure and human condition to improve the crashworthiness of metal aircraft fuselage.Aiming at the crashworthiness of composite fuselage structure,an anisotropic material constitutive model of fiber reinforced composites under the influence of strain rate was established by introducing strain rate strengthening factor.The validity of the model is confirmed by comparing with the test results of typical samples.Based on the material model,the numerical model of the typical composite fuselage is established.The crash performance influence of the fuselage crashworthiness of the composite material skin and the strut of the different ply / structure was studied respectively.The crashworthiness design scheme for composite fuselage is proposed.