Author(s)

P. Stephani, P. Middendorf & Ch. Leß

Abstract

The vulnerability of a CFRP integral tank against HRAM (hydrodynamic ram) is analysed. The geometry of the tank is based on a generic MALE (Medium Altitude Long Endurance) UAV (Unmanned Aerial Vehicle). Several designimprovements are to be analysed. HRAM occurs if a high-energetic object penetrates a fluid filled structure (e.g. a fuel tank below its fill level). Pressure waves, originating from the impactor, cause severe pressure loads on the walls. This can lead to the destruction of the tank and in case of an integral tank, to the failure of structural necessary components. One segment of the integral tank from the generic MALE-wing is simulated using the explicit finite element code LS-DYNA with Fluid-Structure-Interaction. The analysed design-solutions include spars with holes in it that should work as pressure outlets and a redesign of the outer spar. Keywords: HRAM, hydrodynamic ram, UAV, MALE, integral tank, LS-DYNA, CFRP, FSI, fluid structure interaction. 1 Introduction HRAM poses a significant threat to modern military aircraft, since the fuel tanks represent the largest exposed area of all vulnerable components. Data from \“Desert Storm” shows that 75% of all aircraft losses can be traced back to the fuel system (Addessio [1]). These losses can be attributed to three main effects: fire, explosion and HRAM. Statistics indicate that HRAM is by far the most lethal of these three. This is especially true for highflying UAVs, having a large wing area because of aerodynamic requirements. These aircraft-types feature

Keywords

HRAM, hydrodynamic ram, UAV, MALE, integral tank, LS-DYNA, CFRP, FSI, fluid structure interaction.