Combined effects of nanotube aspect ratio and shear rate on the carbon nanotube/polymer composites
Combined effects of nanotube aspect ratio and shear rate on the carbon nanotube/polymer composites
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DOI：
10.1016/j.polymer.2012.07.045
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发表时间：
2012-09-12
期刊：
影响因子：
4.6
通讯作者：
Bauhofer, W.
中科院分区：
文献类型：
--
作者：
Eken, A. E.;Tozzi, E. J.;Bauhofer, W.
我们使用纤维级模拟研究碳纳米管（CNT）的纵横比和剪切速率的CNT/聚合物复合材料的微观结构和电性能的综合影响。在我们以前的研究中，我们研究了在恒定剪切速率下长径比的影响以及恒定长径比下剪切速率的影响。在这项研究中，CNT/聚合物复合材料的电性能和微观结构的变化（如团聚/解聚，网络强度，纳米管取向）进行了研究，在不同的剪切速率下的不同的纵横比。当剪切速率增加时，我们观察到由于解聚和流动诱导取向，电导率降低和各向异性因子增加。增加长径比使电导率与剪切速率的曲线向较大值移动，并且使各向异性与剪切速率的曲线向较低值移动，这表明当使用高长径比纳米管时存在管团聚的趋势。另一方面，当使用低纵横比纳米管时，导电网络可能更容易被剪切力破坏，因为由低纵横比纳米管形成的网络具有比由高纵横比纳米管形成的网络更低的强度。我们的研究结果表明，电导率是各向异性的较大分量的流动方向。临界剪切速率被定义为剪切速率，其中导电网络被破坏，并且复合材料的所有组分的导电性降低到基体导电性，当纵横比增加时，向较高的值移动。减少的对齐和增加的缠结是这种减少的原因。(C)2012爱思唯尔有限公司保留所有权利。
We use fiber-level simulations to investigate the combined effects of carbon nanotube (CNT) aspect ratio and shear rate on the microstructure and electrical properties of CNT/polymer composites. In our previous studies, we studied the effects of aspect ratio at a constant shear rate as well as the effects of shear rate for a constant aspect ratio. In this study electrical properties and microstructure changes (e.g. agglomeration/deagglomeration, network strength, nanotube orientation) of CNT/polymer composites are investigated for varying aspect ratios at different shear rates. When shear rate is increased, we observe a decrease in the electrical conductivity and an increase in the anisotropy factor due to the deagglomeration and flow induced orientation. Increasing aspect ratio shifts the conductivity vs. shear rate curve to larger values and anisotropy vs. shear rate curve to lower values showing that there is a tendency for tube agglomeration when high aspect ratio nanotubes are used. On the other hand when low aspect ratio nanotubes are used, conductive networks can be more easily destroyed by the shear forces because networks formed by low aspect ratio nanotubes have lower strength than those formed by high aspect ratio nanotubes. Our results show that electrical conductivity is anisotropic with a larger component in the flow direction. The critical shear rate defined as the shear rate where the conductive network is destroyed and all components of the composite conductivity decrease to the matrix conductivity, shifts to higher values when the aspect ratio is increased. Reduced alignment and increased entanglement are the reasons of this decrease. (C) 2012 Elsevier Ltd. All rights reserved.