The nonlinear elastic response of filled elastomers: Experiments vs. theory for the basic case of particulate fillers of micrometer size
The nonlinear elastic response of filled elastomers: Experiments vs. theory for the basic case of particulate fillers of micrometer size
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DOI：
10.1016/j.jmps.2019.103781
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发表时间：
2020-02
影响因子：
5.3
通讯作者：
M. Leonard;Naibin Wang;O. Lopez-Pamies;Toshio Nakamura
中科院分区：
文献类型：
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作者：
M. Leonard;Naibin Wang;O. Lopez-Pamies;Toshio Nakamura
用于增强弹性体的宏观弹性的标准颗粒填料-最值得注意的是炭黑和二氧化硅颗粒-固有地具有纳米尺寸。因为它们的尺寸与包埋弹性体中交联之间的聚合物链段的典型长度相当，所以存在多种微观机制，通过这些微观机制，这种填料提供宏观增强。其中众所周知的是所谓的流体动力学效应，长期以来，人们一直认为随着填料的尺寸从纳米增加到微米或更大的长度尺度，流体动力学效应变得越来越占主导地位。本文报告了一项实验/理论研究，旨在通过隔离（即排除其他增强机制的存在，如界面和闭塞橡胶）并量化原型类颗粒填充弹性体增强非线性弹性响应背后的流体动力学效应，来严格检查这种信念：聚二甲基硅氧烷（PDMS）具有不同的交联密度，填充有各向同性分布的单分散微米尺寸的玻璃球形颗粒。在各种填充的PDMS弹性体的实验与基于最近开发的严格的均质化结果的预测之间发现的密切一致性证实了在添加玻璃颗粒后观察到的PDMS弹性体的非线性弹性响应的增强确实仅仅是由于流体动力学效应。除了填补填充弹性体的基本实验知识中的空白之外，本文报道的发现还对许多新兴的活性填充弹性体（例如磁流变弹性体）的建模具有直接的实际影响，其中铁填料颗粒（与标准填料相比）通常为微米尺寸。
Standard particulate fillers utilized to enhance the macroscopic elasticity of elastomers — most notably, carbon black and silica particles — are inherently of nanometer size. Because their size is comparable to the typical lengths of the polymer chain segments between crosslinks in the embedding elastomers, there is a plurality of microscopic mechanisms by which such fillers provide macroscopic enhancement. Well-known among these is the so-calledhydrodynamiceffect, which has long been thought to become increasingly dominant as the size of the fillers increases from nanometer to micrometer or larger length scales. This paper reports a combined experimental/theoretical investigation aimed at critically examining such a belief by isolating — that is, by excluding the presence of other enhancing mechanisms, such as interphases and occluded rubber — and quantifying the hydrodynamic effect behind the enhanced nonlinear elastic response of a prototypical class of particle-filled elastomers: polydimethylsiloxane (PDMS) featuring various cross-link densities filled with an isotropic distribution of glass spherical particles of monodisperse micrometer size. The close agreement found between the experiments for a variety of filled PDMS elastomers with the predictions based on recently developed rigorous homogenization results corroborate that the observed enhancement in the nonlinear elastic response of the PDMS elastomers upon the addition of the glass particles is indeed solely due to the hydrodynamic effect. In addition to filling a lacuna in the basic experimental knowledge of filled elastomers, the findings reported here also have direct practical implications on the modeling of a number of emerging active filled elastomers, such as for instance magnetorheological elastomers, wherein the iron filler particles — in contrast to standard fillers — are typically micrometer in size.