闭孔EVA泡沫类静态缓冲性能的研究

目的 研究密度与应变率对闭孔EVA泡沫材料类静态缓冲性能的影响规律。方法 基于包装用缓冲材料静态压缩试验法和能量吸收图法，对密度为80、95、106、124和180kg/m³的闭孔EVA泡沫试样在不同应变率下进行类静态压缩试验，得到应力-应变曲线，基于此进一步处理得到相应的单位体积能量吸收、能量吸收效率、缓冲系数和最大比吸能等曲线，同时绘制试样类静态压缩过程中的能量吸收图。结果 闭孔EVA泡沫材料的密度越高，密实化应变越小，最大单位体积能量吸收越大；在压缩应变相同时，应变率越大，应力、单位体积能量吸收、能量吸收效率、最大比吸能越大；得到了5种密度闭孔EVA泡沫材料的本构方程和闭孔EVA泡沫材料的能量吸收图及其斜率与应变率的关系式；通过分析密实化应变与相对密度的关系，得到相关拟合公式。结论 密度与应变率对闭孔EVA泡沫材料的缓冲性能有着非常大的影响，在一定的应力水平下会有一个最佳的密度使得刚好能吸收完能量，并保护产品不破损，该最佳密度受应变率的影响，因此可以通过能量吸收图进行相关的缓冲包装优化设计。

Quasi-static Cushioning Properties of Closed-cell EVA Foam

The work aims to study the effect of density and strain rate on the quasi-static cushioning properties of closed-cell EVA foam. Based on the static compression test for cushioning materials and the energy absorption diagram method used in packaging, closed-cell EVA foam samples with densities of 80, 95, 106, 124, and 180 kg/m³ were subject to quasi-static compression tests at different strain rates, and the stress-strain curves were obtained. Based on further processing, the corresponding curves of energy absorption per unit volume, energy absorption efficiency, chushioning coefficient and maximum specific energy absorption were obtained. Simultaneously, an energy absorption diagram during the static quasi-compression process of the sample was drawn. The results showed that, the higher the density of closed-cell EVA foam, the smaller the densification strain and the larger the maximum energy absorption per unit volume; At the same compression strain, the larger the strain rate, the greater the stress, energy absorption per unit volume, energy absorption efficiency, and maximum specific energy absorption; The constitutive equations of five density closed-cell EVA foam materials, the energy absorption diagram of closed-cell EVA foam materials and the relationship between slope and strain rate were obtained; By analyzing the relationship between densification strain and relative density, relevant fitting formulas were obtained. The density and strain rate have a great impact on the cushioning performance of closed-cell EVA foam materials. Under a certain stress level there is an optimal density that can right absorb energy and protect the product from damage. The optimal density is affected by the strain rate, so the design of relevant cushioning packaging can be optimized with the energy absorption diagrams.