Contribution to an improved crash design for a composite transport aircraft fuselage—development of a kinematics model and an experimental component test setup

Crashworthiness research for transport aircraft fuselage structures is important particularly with regard to the increasing ratio of carbon fibre reinforced plastic (CFRP) in primary structures. Although today’s aluminium fuselage structures offer sufficient crashworthiness purely due to the ductile behaviour of metal, the brittle behaviour of a CFRP fuselage structure implicates the need for special crash devices to avoid uncontrolled failure with little energy absorption. Hence, a specific crash design has to be developed for a CFRP fuselage structure. A numerical methodology was developed to investigate potential crash concepts on fuselage section level and to design appropriate crash devices. The essential of this so-called kinematics model is the potential to define the behaviour of structural crash devices by characteristic input curves using macro elements in the frames, vertical struts and the sub-cargo structure. By varying the load–deformation characteristics of the crash devices, different crash scenarios, in the sense of alternative crash sequences, can be defined, assessed and compared to each other. Different potential crash scenarios for narrow-body fuselage structures were analysed using this modelling approach. The final output characteristic of the macro elements in the frame structure represents the basis for an experimental investigation of energy absorbing frame bending mechanisms. A test setup for four point flexural test configurations was developed to investigate such concepts on the generic frame level. The setup was used to analyse the failure behaviour of frame components made of pure CFRP as well as hybrid CFRP/titanium laminates. Four quasi-static as well as four dynamic frame bending tests were conducted to investigate the energy absorbing failure mechanisms of such hybrid frame structures.