Enhanced Compression Properties of Open-Cell Foams Reinforced with Shear-Thickening Fluids and Shear-Stiffening Polymers

Open-cell PU foams have a wide range of industrial applications due to their excellent cushioning, impact protection, packaging, thermal insulation, and sound reduction benefits. The foams absorb impact energy while deforming under compressing and are ideal for applications with severe and repeated loading conditions. Enhancing and improving their compressive durability is a vital area of ongoing research. We investigated the effect of incorporating shear-stiffening polymers (SSPs) and shear-thickening fluids (STFs) on the compression properties of open-cell foams. Rheological properties of STFs and SSPs prepared for incorporation into the foams confirmed the shear-thickening and shear-stiffening characteristics. Quasi-static compression tests performed at different speeds (6, 60, 120, 180, and 240 mm/s), as well as load-unload compression tests (6 and 24 mm/s), showed that the SSP-filled foam exhibited the most pronounced improvement in the elastic, plateau, and densification regions compared to the neat foam. While the STF-filled foam also improved performance over the neat foam, its advantages over the SSP-filled foam were less pronounced. The performance of the SSP-filled foam improved with increasing compression speeds, while the performance of the STF-filled foam remained relatively stable between 60 and 240 mm/s of load-unload tests. Post-test compression evaluations showed that neat and STF-filled foams quickly regained their original shape, while SSP-filled foams required more time before recovery. This research shows that combining SSP and STF smart materials with open-cell foams substantially improves their compressive performance, especially at high compression rates and load-unloading scenarios, increasing their functional life.