Topological optimization of rotorcraft subfloor structures for crashworthiness considerations

The present paper discusses significant design issues in the sizing of rotorcraft structures for requirements of enhanced crash performance. The focus of the study is on topological design of the subfloor structure, defined as a crush zone under a more rigid floor structure. The topological design problem includes both an appropriate selection of an energy absorbing material (tailored load-deflection curve), and placement of this material at discrete locations under the main floor structure. A genetic algorithm based optimization approach was used in conjunction with a crash response analysis code (KRASH), which uses lumped masses, linear and nonlinear beam elements, and nonlinear spring elements to model the primary and secondary structure. The analysis problem is computationally demanding, and to alleviate these costs, approximate response models based on a multilayer perceptron neural network were developed and used in the optimization studies. (C) 1997 Civil-Comp Ltd and Elsevier Science Ltd.