循环压缩和冲击下聚氨酯发泡塑料的能量吸收

摘要

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 ×10 1 s -1 ,5.08 ×10 1 s -1 and 5.68 ×10 1 s -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.%基于聚氨酯发泡塑料的准静态压缩和落锤冲击试验，分析其在中低应变率下的力学性能和能量吸收性能，得到了该材料的应力－应变曲线和能量吸收图，研究了不同应变率和循环静动态试验对该材料缓冲性能的影响。随着初始应变率由2．56×10－3 s －1（准静态）增加至4．01×101 s －1、5．08×101 s －1和5．68×101 s －1，材料的应力和能量吸收明显增大，应变为0．4时动态应力分别比静态应力增加了54．34％、79．35％和114．49％，所吸收的能量分别比静态增加了18．98％、30．09％和65．74％。对同一试样先后进行五次循环准静态压缩或落锤冲击试验，与首次试验相比第二、三、四、五次试验应力和能量吸收明显下降，应变为0．4时静态应力分别下降了18．48％、32．97％、36．59％和39．49％，动态应力分别下降了20．81％、28．48％、34．75％和34．75％，准静态压缩能量吸收分别下降了24．54％、37．50％、40．74％和43．52％，落锤冲击能量吸收分别下降了15．30％、24．20％、30．25％和30．96％。中低应变率下，聚氨酯发泡塑料的应变率效应十分明显，循环准静态压缩和落锤冲击效应同样十分明显。循环试验达到一定次数后，材料缓冲性能基本保持不变，可用此数据作为缓冲包装设计的依据。研究结果对于聚氨酯发泡塑料的合理缓冲包装设计有指导意义。