The properties of the Poisson’s ratio of microcellular foams with low porosity: non-stationary, negative value, and singularity
The properties of the Poisson’s ratio of microcellular foams with low porosity: non-stationary, negative value, and singularity
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DOI：
10.1007/s11043-007-9025-6
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发表时间：
2007-05
影响因子：
2.5
通讯作者：
John Chen;J. Zhu;J. Wang;M. Yuan;H. Chu
中科院分区：
文献类型：
--
作者：
John Chen;J. Zhu;J. Wang;M. Yuan;H. Chu
研究了气孔内压低孔率微孔泡沫的泊松比特性。最感兴趣的是基质蠕变对泡沫变形的影响，以及根据泊松描述，这种影响如何影响材料后来的变形特征。首先，回顾了单轴应力下微孔泡沫的泊松比的定义。其次，利用EShelby等效夹杂方法分析了微孔洞在内压作用下的变形情况。其次，利用Mori-Tanaka方法推导了微孔泡沫材料的宏观应变公式，并在此基础上得到了材料的泊松比表达式。此外，还计算了材料的泊松比。数值结果表明，微孔泡沫的泊松比是一个随时间变化的参数。文中还讨论了由于孔洞内部压力的影响，整体泊松比可能为负。在远距离压缩载荷作用下，微孔泡沫的泊松比可能是无界的。最后，借助于数值计算，讨论了加载速率、聚合物基质材料的泊松比和松弛时间、微孔洞的孔隙率和压力对泊松比的影响。这些分析结果表明，单轴拉伸下的泊松比不同于单轴压缩下的泊松比。
The properties of the Poisson’s ratio of microcellular foams with an internal pressure in the voids and low porosity are investigated. Of prime interest is the effect of the matrix creep on the deformation of the foam and how this effect influences the later deformation characteristics of the material in terms of a Poisson description. First, the definitions of Poisson’s ratio for the microcellular foams under uniaxial stress are reviewed. Second, the deformation of the microvoids under the influence of the internal pressure is analyzed by means of Eshelby’s equivalent inclusion method. Next, the formula of the macroscopic strain of the microcellular foams is derived by using Mori–Tanaka’s scheme, and based on this formula, the expression of the Poisson’s ratio of the material is obtained. Further, the calculation of the Poisson’s ratio of the material is then carried out. Numerical results show that the Poisson’s ratio of the microcellular foams is a time-dependent parameter. It is also discussed that because of the effect of the internal pressure in the voids, the global Poisson’s ratio may be negative. Under the action of remote compressive load, the Poisson’s ratio of the microcellular foams may be unbounded. Finally, the effects of the loading rate, the Poisson’s ratio and the relaxation time of the polymeric matrix material, the porosity, and the pressure in the microvoids on the Poisson’s ratio are discussed with the aid of numerical estimates. These analytical results indicate that the Poisson’s ratio under uniaxial tension is different from that under uniaxial compression.