A hybrid multibody model for aircraft occupant/seat cushion crashworthiness investigation

Abstract

Seat cushion is in the primary load path between the seat and the occupant, and the potential for injuries to an occupant in an accident highly depends on it. The seat cushion is able to dissipate the kinetic energy due to impact in a controlled manner. Wide varieties of energy absorbing materials are used in aircraft interiors for occupant safety and ergonomic purposes. Flexible polyurethane foams are one among those used in seat cushions. Although comfort and aesthetics play an important role in the seat cushion design, safety is among the top criteria. Studies on seat cushions have demonstrated that the seat cushions generally amplify the lumbar/pelvis transmitted load to the occupant, making the seat cushion design further complicated for crashworthy design. The certification of seat cushion requires that their performance be demonstrated by dynamic full scale sled testing. Due to the high costs involved in dynamic testing, a mathematical hybrid multi-body model is developed in this study to simulate the dynamic responses of a bare iron seat, the seat cushion and the occupant represented by crash test dummy. The model is utilized to predict the lumbar load sustained when subjected to the FAR Part 23 and 25 dynamic test conditions for transport and general aviation category aircraft. The model is also used to determine the relative displacement and velocity of occupant against the seat pan. The results from the dynamic model are validated with full-scale sled tests performed at the National Institute for Aviation Research (NIAR), and hence can be utilized as a design tool for the selection of proper seat cushions. Copyright © 2005 by ASME.