Enhanced anti-impact resistance of polyurethane foam composites with multi-phase shear thickening fluids containing various carbon nanofillers

Polyurethane (PU) foams are commonly used as impact-absorbing materials in various applications. However, the anti-impact performance of PU foams can be improved by incorporating non-Newtonian based smart fluids in their strudture. This study enhanced a open-cell based PU foam with multi-phase shear thickening fluids (M-STFs) containing three types of carbon nanofillers (carbon nanotubes, carbon nanofibers, and their mixture). M-STFs were prepared by adding 0.5, 1.0, 1.5, and 2.0 wt% of carbon nanofillers to the STF (55 wt% SiO2) and subsequently impregnating them into the structure of PU foams. Various configurations of PU foam composites were designed and evaluated for their impact resistance performance using a low-velocity drop tower system. The rheological behavior of fabricated suspensions were characterized using a rotational two plate-based system. The chemical structure and morphology of M-STF-treated PU foams were characterized by FTIR spectroscopy and SEM, respectively. The peak deceleration values in terms of G were measured after subjecting the designed samples to impacts at three different heights of 0.1, 0.2, and 0.3 m. The results indicated that the addition of nanofillers enhaced the initial and peak viscosity of the STF, and carbon nanotube had the most significant effect. The PUF-STF/CNT(1.5) sample exhibited approximately 62.7% to 73.0% reduction at different heights in peak deceleration compared to the clean PU foam sample. Moreover, to investigate the impact of filler content, drop height, and type of fillers on the peak deceleration of M-STF-treated PU foams, a response surface methodology analysis was utilized and the model provided insight into the optimal conditions for minimizing peak deceleration. This study highlights the potential of using M-STFs to enhance the anti-impact performance of PU foams.