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Comfort performance has developed into a central theme of vehicle seating design due to the role of the seat as the interface between the vehicle and the human. These comfort performance requirements exercise considerable influence over the specifications of the polyurethane foam that serves as a primary load-bearing material in the seat assembly. Various test protocols have been established to measure and predict comfort performance for polyurethane foam. One of the most important test methods is the vibration transmissivity test, used to characterize the response of a material to vibration of varying frequency and energy. This test methodology measures the performance of polyurethane foam alone to the performance of a fully assembled seat in a vehicle driven on a road surface. As such, there are a variety of test conditions employed to characterize transmissivity performance.

Polyurethane foam is the premier material used in automotive seating. One of the primary reasons for its preeminent position is the ability of the foam to maintain its comfort performance during the life of the vehicle. The persistent properties of polyurethane foam are related to its ability to recover its performance after a short period of rest. In this paper, a specific methodology for quantifying the property response of polyurethane foam is presented with data for two different foam chemistries. The conditions for the test procedures are selected based on the simulated road conditions that can be expected during a three-hour drive. Creep phenomena are measured to determine the extent and nature of property changes.

A recent trend in vehicle seating design is the change in structure from a spring / foam composite to a foam and dead pan structure. For a composite design, the seat vibrational characteristics are tuned for the vehicle by adjusting the spring stiffness. In a dead pan design, however, foam dynamics solely dictate seat vibrational characteristics. Foam vibrational transmissivities measured by a laboratory test are compared with transmissivities measured with human subjects and road profiles. The in-vehicle vibrational performance of the foam has been quantified using the S.E.A.T. method for several vehicle categories. The role of foam dynamics has been quantified for full foam seats.