Project Abstract: The objectives of the research proposed here are to further the understanding of the dynamic behavior of flexible polyurethane foam, and to significantly enhance the models of foam components incorporated in overall dynamic system models. The dynamic models of occupant-seat systems, which include foam components, can be used to predict occupant vibration which can, in turn, be translated into vibration comfort. Currently, spring-mass-dashpot type multi-degree-of-freedom models are used for vibration comfort studies. These models are linear and without memory (elastic), whereas foam is known to be highly nonlinear and displays memory (viscoelastic) effects. It is thus proposed to develop nonlinear, viscoelastic models of the components made with flexible polyurethane foam. They are to be based on the constitutive models of viscoelastic materials found in the literature and are expected to include linear exponential and fractional derivative relaxation models, as well as nonlinear extensions of these types of models. It is hypothesized that these detailed macroscopic mechanical models of foam components will be much more useful, than the linear models currently used, in the development of links between the microscopic structural and chemical composition of the foam and its mechanical properties. In addition to developing the most appropriate analytical model forms, the work is to focus on: the identification of structure models from experimental data, the development of experimental methods useful in revealing pertinent aspects of foam behavior, the development of robust parameter estimation methodologies, and the experimental validation of the vibratory response predictions based on seat-occupant models. While the simulations, identification, and experimental validations in this research are focused on car-seat foam, the system identification and parameter estimation techniques developed will be also useful in the identification of models for other viscoelastic materials.