Sign change of Poisson's ratio for carbon nanotube sheets
Sign change of Poisson's ratio for carbon nanotube sheets
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DOI：
10.1126/science.1149815
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发表时间：
2008-04-25
期刊：
影响因子：
56.9
通讯作者：
Baughman, Ray H.
中科院分区：
文献类型：
--
作者：
Hall, Lee J.;Coluci, Vitor R.;Baughman, Ray H.
大多数材料在拉伸时会像橡皮筋一样横向收缩，因此它们的泊松比为正。同样，大多数材料在流体静力压缩时向各个方向收缩，拉伸时密度降低，因此它们具有正线性可压缩性。我们发现，通过混合单壁和多壁纳米管，碳纳米管片的面内泊松比可以从正到负。通过这种混合，密度归一化的板材韧性、强度和模数显著增加。一个简单的模型从纳米纤维弯曲和拉伸的相对容易程度预测了巴克纸的泊松比的符号和大小，并解释了为什么普通书写纸的泊松比是正的，而且要大得多。理论还解释了为什么负的面内泊松比与薄板厚度的大的正泊松比有关，并预测了静液压可以产生双向薄板膨胀。泊松比的这种可调性可用于板材衍生复合材料、人造肌肉、垫圈以及化学和机械传感器的设计。
Most materials shrink laterally like a rubber band when stretched, so their Poisson's ratios are positive. Likewise, most materials contract in all directions when hydrostatically compressed and decrease density when stretched, so they have positive linear compressibilities. We found that the in- plane Poisson's ratio of carbon nanotube sheets ( buckypaper) can be tuned from positive to negative by mixing single- walled and multiwalled nanotubes. Density- normalized sheet toughness, strength, and modulus were substantially increased by this mixing. A simple model predicts the sign and magnitude of Poisson's ratio for buckypaper from the relative ease of nanofiber bending and stretch, and explains why the Poisson's ratios of ordinary writing paper are positive and much larger. Theory also explains why the negative in- plane Poisson's ratio is associated with a large positive Poisson's ratio for the sheet thickness, and predicts that hydrostatic compression can produce biaxial sheet expansion. This tunability of Poisson's ratio can be exploited in the design of sheet- derived composites, artificial muscles, gaskets, and chemical and mechanical sensors.