Aircraft crashworthiness: modelling of fuel inside a conformable tank

Abstract

With the aid of modern computing systems and commercial finite element (FE) codes, the expensive and non-repeatable experimental crashworthiness testing of complex fuselage sections can be simulated accurately. However, some key problems associated with the virtual drop tests have yet to be resolved. One such example is the vertical impact test of the fuselage section with an onboard auxiliary fuel tank, which contains a large amount of fuel inside the fuel tank, where an inevitable fluid-structure interaction (FSI) takes place during crashworthiness. Despite this fact, to date, the researchers have adopted mass distribution techniques where fuel modelling is excluded to avoid the FSI and the total mass of the fuel is distributed over the fuel tank surfaces. Therefore, in this present study, an effort is made to evaluate the importance of FSI over mass distribution techniques to model the fuel adopting the FE code Ansys Explicit. Investigated crash outcomes of the fuselage section based on plastic energy dissipation, plastic deformation, and seat track acceleration responses suggest that in the case of mass distribution techniques, the tank body behaves as rigid, which eventually limits the fuel tank from absorbing much less plastic energy compared to FSI. This also leads to a different failure mechanism for the ribs, which are mainly crashing for mass distribution techniques, while plastic hinge failure occurs for FSI. Finally, after a detailed comparison and discussion, it is concluded that the FSI method is more suitable to represent fuel inside an auxiliary fuel tank.