Energy absorption of expanded polyurethane under cycling compression and impact

Based on quasi-static compression and drop hammer impact tests, the mechanical property and energy absorption of expanded polyurethane (EPU) were analyzed, and the stress-strain curve and energy absorption diagram were obtained at low and intermediate strain rates. The effects of different initial strain rates and of cycling compression and impact tests on cushioning properties of EPU were investigated. The stress and energy absorption of EPU increase obviously when the initial strain rate increases from 2.56×10-3 s-1 (quasi-static) to 4.01×101s-1, 5.08×101s-1 and 5.68×101s-1. Compared with the lowest initial strain rate, the stress increases respectively by 54.34%, 79.35% and 114.49%, and the energy absorption by 18.98%, 30.09% and 65.74% when the strain is 0.4. Five times of cycling quasi-static compression or drop hammer impact tests were carried out on each sample. Compared with the first test, the stress and energy absorption of EPU in the second to fifth tests decline obviously. When the strain is 0.4, the static stress declines respectively by 18.48%, 32.97%, 36.59% and 39.49%, the dynamic stress by 20.81%, 28. 48%, 34.75% and 34.75%, the energy absorption in quasi-static compression by 24.54%, 37.50%, 40.74% and 43.52%, and the energy absorption in drop hammer impact by 15.30%, 24.20%, 30.25% and 30.96%. The effects of strain rate and of cycling compression and impact on cushioning property of EPU are obvious at low and intermediate strain rates. After certain times of cycling quasi-static compression or drop hammer impact, the cushioning properties of EPU turn to remain unchanged. So, cushioning packaging with EPU can be designed according to the data resulted. ©, 2015, Chinese Vibration Engineering Society. All right reserved.