Assessment of a Crashworthy Fuel Tank Finite Element Model for Ground Impact Analysis

Statistics show that the fire, as a consequence of the ground impact of a helicopter in an emergency, is the first cause of death among the helicopter occupants. In view of that, severe requirements for fuel tank certification were established and now the fuel tank crashworthiness is the first concern in the helicopter fuel system design. In this research work, a numerical model capable to capture the complex impact dynamics of a fuel tank impacting the ground is introduced. Experimental ground impact tests were performed using fuel tank simulacra and the data acquired were used to validate a fuel tank finite element model. Furthermore, in effort to achieve an accurate description of the event tests were carried out to characterize the impact behavior of the sandwich panels used to realize the fuel tank structure, the fuel bag and the failure mechanism of the riveted and bolted joints. Experimental tests were numerically reproduced and, eventually, a good numerical-experimental correlation was achieved. The latter showed that the numerical approach is actually a valuable tool for the development of crashworthy structures. The experience collected during this research work contributed to achieve the certification of the modified configuration of an actual fuel tank, whose original configuration had been previously certified by test.