IMPROVING DISTRIBUTION OF CRASH ENERGY ABSORPTION FOR CIVIL AIRCRAFT BASED ON PROGRESSIVE BENDING FAILURE MECHANISM

High level of civil aircraft crashworthiness is desired to provide as much protection as possible for occupant during a possible crash accident. This suggests the requirement inherent for assigning the energy absorption distribution in a fuselage structure according to design intention. Numerous works show that noticeable energy altering of component for conventional fuselage layout usually accompanies with unacceptable mass penalty and cost. In addition, it still remains significant difficulty to fulfill intended fuselage deformation mode. In this paper, the progressive bending failure mechanism of frame is employed to develop a crashworthy structure layout below the cabin floor. An appropriately constrained frame could be failure in a progressive manner under a transverse impact with moving contact surface, and then develops new deformation mode. Three energy absorption zones are formed naturally in the lower fuselage shell. The aim of the preliminary design study is to evaluate the crashworthiness aspects on fuselage section level. Finite element simulations for a two-frame fuselage section were performed at the vertical impact velocity of 7 m/s, and parameter analysis as well as comparison with a conventional counterpart were conducted. It was found that the level of energy absorption of the conventional fuselage is “high-mid-high” from the bottom zone to the top one, corresponding to the energy absorption percentages 35.0%, 25.3%, and 34.8%; whereas the presented fuselage is “mid-high-low”, corresponding to 11.5%-37.3%, 44.2%-63.1%, and 6.0%-10.5%. At two occupant-seats position, the peak acceleration values are reduced by 12.5%-45.7%, and 16.4%-58.0%, respectively, with one exceptional increasing by 0.4% of the former. For all parameters, only one yields W-type deformation in the lower fuselage, the others are U-type.