Low-Energy Seat Compression: Characterizing Stiffness in Different Vehicles

In rear-end collisions, occupants move rearward relative to the vehicle interior, while compressing the seatback. In low-energy impacts, the stiffness of the non-frame seat components may influence the kinematic response of an occupant. Previous research has reported seat stiffness from experiments for a limited number of seats. Because passenger vehicle seats have evolved, this current work reports a range of seat stiffnesses for modern passenger vehicles. A portable measuring device to characterize vehicle seat stiffness was built to accommodate a wide range of vehicle types. The device measured simultaneously the force applied to the seat and the displacement of the seat cushion. Seats of sedans, crossovers, sport utility vehicles, minivans, and pickup trucks for model years between 2016 and 2020 were tested using the device. For each seat, three measurements were taken for four different seat regions: upper seatback, lower seatback, aft seat bottom and fore seat bottom. The seat stiffness for each region was determined using a linear fit of the force-displacement curve generated during testing. The range of seat stiffness across all seat types was 3.13 kN/m to 23.32 kN/m. The average stiffness was 11.22 kN/m (SD 4.34 kN/m) for the upper seatback, 9.34 kN/m (SD 3.07 kN/m) for the lower seatback, 14.54 kN/m (SD 3.38 kN/m) for the aft seat bottom and 15.02 kN/m (SD 3.81 kN/m) for the fore seat bottom. Seat stiffness was significantly lower for all vehicle types for the lower seatback compared to aft seat bottom and fore seat bottom.