In this study, a tool was developed for incorporating crashworthiness into the preliminary design of grid-stiffened composite fuselage structures. The crash analysis of a fuselage structure was simplified through the development of a global-local procedure, which reduces the computational requirements of a crash simulation while facilitating the calculation of local stresses. The method was implemented in concert with a progressive failure model to model the entire crash sequence, including failure events and subsequent response. Several examples were used to validate this method. This method was then implemented, along with simple models for assessing the ability of a fuselage to meet other load requirements, into a genetic algorithm optimization procedure. The resulting preliminary design tool permits a designer to optimize a fuselage for minimum weight, maximum crashworthiness or any combination of these parameters. An illustrative example was utilized to demonstrate the use of the tool for an aluminum fuselage as well as a composite fuselage. Several designs were found for both materials that substantially increased crashworthiness without a significant penalty on structural weight. / Ph. D.