Improved Vibration Characteristics of Flexible Polyurethane Foam via Composite Formation

Abstract

Flexible polyurethane (PU) foam is used as cushioning material in automotive seating for load bearing. Owing to the demand for more comfortable compartments, seat cushions are now designed for better ride comfort, which is linked to the damping of seating foam. In this paper, PU polymer was mixed with short treated coir fibers (F) and recycled tires (P) to enhance damping and improve the vibrational characteristics of seating foam. Five samples with 2.5wt% filler loading were developed. The vibration characteristics of foam composites were examined by transmissibility tests generated at 1 and 1.5 mm peak amplitude in the frequency range of 2–20 Hz, using a shaker, shaking table, and a foam-block system. The foam-block system was fabricated by simulating the seat/occupant system in an automobile. The damping properties of foam composites were calculated from the transmissibility data obtained. The results showed that more vibration was dissipated by the developed foam composites after the fillers were added. System inserts with PU+2.5wt%P gave the lowest resonance peak: 2.460 and 2.695 at 1 and 1.5 mm base excitation, respectively, compared with 2.788 and 2.878 obtained from system inserts of pure PU foam. This is because a higher damping ratio (ξ foam) was found in PU+2.5wt%P, which is 36.47% and 19.23% higher than pure PU foam. In addition, other composites, such as PU+2.5wt%F, PU+2.5wt% (50F50P), PU+2.5wt% (80P20F), and 2.5wt% (80F20P) also showed favorable vibration and damping characteristics in the experiments. When compared with the conventional seat cushions used in the Proton car, foam composites could offer better vibration dampening at resonance.