Research On Crashworthiness Of Composite Material Civil Aircraft Fuselage Section

Composite materials are widely used in new civil aircraft.But there are some undesirable characteristics of composite structure such as large initial peak load of crushing,minor average crushing load and low load efficiency,which may have a negative impact on the crashworthiness of aircraft with composite materials.Crash test is one of the primary means to study the crashworthiness of civil aircraft.However,test methods have some shortcomings,such as the process is not repeatable,high cost,time-consuming and most importantly,the energy changes of structures and components is not available during the process.With the development of computer simulation technology,the numerical method represented by finite element method has been widely used in the field of aircraft design.The numerical simulation method is repeatable,low cost,short cycle and able to capturing the details of the crash process.Therefore,the study of the crashworthiness of typical civil aircraft and the influence of composite materials on the crashworthiness of the fuselage section by finite element method has guiding value for the design of composite fuselage.This paper is based on the "building block" crash test plan and the domestic large civil aircraft R&D project.And finite element method is employed to study the crashworthiness of metal material fuselage and of various composite skin fuselage sections respectively.The influence of composite skin angle on the crashworthiness of fuselage sections is also investigated.The main research results are shown as follows:1.The civil aircraft crash tests in recent years are summarized.Combining with the mechanical characteristics and the failure modes of aircraft structure during crash,the simplification and modeling principles of typical civil aircraft fuselage are established.The finite element model of typical metal civil aircraft fuselage is created by using the finite element method and then the crash test process is simulated.The reliability of the modeling criteria and the finite element analysis method is verified by comparing the simulation results with the crash test results.2.The finite element modeling method of composite skin is proposed.The reliability of the method is verified by experimental results.The crash responses of the skin fuselage of T300/QY8911,T800/QY8911 and GLARE laminate composite systems are compared and analyzed.The failure mode,acceleration response and energy absorption process of the fuselage are considered comprehensively.The results show that the order of their crashworthiness is: GLARE laminate skin fuselage,T800/QY8911 skin fuselage,T300/QY8911 skin fuselage.3.Three kinds of GLARE laminate skins with different laying modes are designed.According to the principle of single variable,three fuselage models with the same design except the ply angle of skin are created and crash tests are simulated.The failure modes,acceleration responses and energy absorption characteristics of fuselage during crash are analyzed.The results show that the crashworthiness of fuselage section of the three layers is not significantly different.Overall,+45/-45 layers are better than 0/90 layers,and the more +45/-45 layers in the skin,the better the crashworthiness of fuselage section.