Differences in Dynamic Performance of Molded Polyurethane Foam as a Function of Pad Thickness and Supported Load

Abstract

Comfort and durability have evolved into essential performance requirements for the polyurethane foam used in automotive seating. A great variety of tests have been developed in an attempt to measure and predict these properties, both for the foam and the assembled seat. However, the results from these various tests can be quite different depending on the test conditions employed. Furthermore, most tests measure comfort properties at some standard deflection, or pressure, which is nominally designed to represent the average population that will be riding on the seat.

Missing from these tests is a recognition that foam comfort properties are not the same at all deflections, and thus performance and perceived comfort will change as a result of the size and shape of the person riding the seat. This research presents information demonstrating the dependence of comfort properties, such as vibrational transmissivity and quasi-static hysteresis, on foam thickness and foam chemistry. In addition, the effect of pressure is demonstrated using various masses for the transmissivity testing. This work will be analyzed and discussed from the perspective that comfort properties may need to be defined relative to the sitting pressure of the person riding on the vehicle seat.

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