Crash analysis of an energy-absorbing subfloor during ground and water impacts

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Crash analysis of an energy-absorbing subfloor during ground and water impacts

Sareen, A.K. / Smith, M.R. / Hashish, E.

The crash-resistant subsystems designed for rigid surface impacts, such as landing gear or subfloors, are not as effective in water and soft soil since the structure undergoes a different loading mechanism. For water and soft soil impacts, the crash loads are distributed across the subfloor skins as opposed to hard surface impacts, which introduce concentrated loads into the stiffest structural members, such as keel beams and frames. As most potentially survivable crash impacts occur on soft soil or water, the energy-absorption behavior of subfloor concepts during both hard surface and water impacts need evaluation. This paper focuses on the evaluation and comparison of relative energy-absorption characteristics of an airframe subfloor design concept during water and hard surface impacts. Using a finite-element-based nonlinear transient dynamics analysis code, MSC/DYTRAN, vertical drop simulations were conducted for the subfloor structure on to hard surface and water. The resulting acceleration pulse at the seat location for hard surface and water impacts were compared with each other and compared with the test data.