Investigation of a crash concept for CFRP transport aircraft based on tension absorption

Abstract

Transport aircraft made of carbon fibre reinforced plastics (CFRP) have to provide an equivalent crashworthiness compared to today's aluminium aircraft designs. However, CFRP structures typically show brittle failure behaviour under complex loading conditions and little energy absorption, whereas aluminium structures provide comparably high energy absorption due to their ductile failure characteristics. Improved crashworthiness for CFRP fuselages can be obtained by the installation of special crash devices, which are designed for energy absorption by progressive failure in compression, tension or bending. The realisation of crashworthy CFRP fuselage designs with the focus on compression or bending absorbers is often associated with significant mass penalty compared to the purely static sizing of the corresponding fuselage structure. In this context, an alternative crash kinematics was developed and numerically investigated in which most of the kinetic energy is dissipated by tension absorption in the sub-cargo area of a fuselage structure. The numerical study was performed on the basis of a purely vertical impact with a two-bay fuselage section using the explicit finite element (FE) solver Abaqus/Explicit. The simulation results show for the developed crash kinematics several advantages, e.g. reduced mass penalty, with the tension absorption concept compared to crash concepts that use energy absorption by progressive crushing in the sub-cargo area.

Crashworthiness study on hybrid energy absorbers as vertical struts in civil aircraft fuselage designs

“…Detail of the lower aircraft structures.Windows were also added to the model with simplified right-angled corners and the associated frame stiffeners. Following other authors' approach, rivets and fasteners throughout the fuselage are modeled as rigid connectors in the software[5,27], not considering failure and damage in these elements. Other complex geometry and features, including cutouts, joints and doublers were excluded from the model, since their implementation would heavily increase the computational cost while not significantly affecting the overall behavior of the model.…”

Crash simulation of fuselage section in the rebound process and the secondary-impact process

“…There are also studies covering the whole aircraft crash simulations of fixed-wing aircrafts (Lu et al, 2015;Schwinn, 2015). With the application and development of composite materials in the fuselage structures, researchers carried out many impact simulations of fuselage using composite materials (Schatrow and Waimer, 2014;Heimbs et al, 2013). Studies on fuselage crashworthiness through simulations have been performed focusing on such aspects as the influence of skin materials, floor stiffness, strut configurations and the formation of plastic hinges and their positions (Ren and Xiang, 2011;Ren and Xiang, 2014).…”

Virtual Design Method for Controlled Failure in Foldcore Sandwich Panels

“…While the specific energy absorption of composite structures can exceed metal under compression, the brittle failure mode under bending loads limits their energy absorption capacity during bending failure. Crash studies highlighted the importance of the installation of kinematic hinges for a crashworthy CFRP fuselage concept; especially if the vertical acceleration loads of the passengers should not exceed values obtained for the metallic reference design [3][4]. Whilst experimental and numerical studies were already performed on CFRP frame segments [5][6][7], there is a limited understanding of the failure mechanisms of CFRP sandwich panels under crash relevant bending loads.…”