欧美伦理一区二区-91视频网页-国产高清在线视频-国产黄色在线-免费的黄色-日本精品视频在线观看

新聞動態
NEWS
Location:Chinese Academy of Sciences > NEWS  > News in field Carbon Nanotubes

Stochastic CNT waviness shows nanocomposites can become stiffer

Come: Chinese Academy of Sciences    Date: 2016-03-07 14:59:32


Orders-of-magnitude effective elastic modulus reductions in aligned carbon nanotubes (CNTs) and their architectures originate from their local curvature, commonly known as waviness. Pre-established theoretical frameworks are unable to adequately describe the three-dimensional morphology of CNTs, which leads to large over-predictions of their elastic response. Reporting in Nanotechnology, researchers at the Massachusetts Institute of Technology use a newly developed simulation framework capable of modeling > 105 CNTs with stochastic three-dimensional morphologies to quantify the impact of CNT waviness on the deformation modes that govern the stiffness of their polymer matrix nanocomposites.

While early reports of the high elastic modulus and low density of carbon nanotubes (CNTs) encourages their use in large-scale commercial composite structures, CNT composites manufactured on the centimetre to metre length-scales behave very differently from what early theoretical models originally predicted. This difference in behaviour is caused by CNT structural and morphological non-idealities, which are inevitable results of their synthesis process via highly scalable chemical vapour deposition techniques, but were not considered in the original theoretical studies. More recent work indicates that the local curvature of the CNTs, which is normally quantified using a non-dimensional waviness ratio that assumes a simple sinusoidal or helical functional form of the waviness, is a major factor contributing to the order of magnitude stiffness over-predictions of early models. However, due to the oversimplified descriptions of the CNT morphology used by these previous studies, little is known about the mechanics of wavy CNTs with realistic stochastic 3D morphology undergoing deformation, and how the complicated CNT morphology will evolve as a function of CNT packing proximity to lead to the observed stiffness enhancements in aligned CNT polymer matrix nanocomposites (A-PNCs).
 
CNTs with realistic morphology
CNTs with stochastic 3D morphologies are assembled as arrays of nodes in xyz space. The CNT waviness is applied using node displacements in the x and y directions via Gaussian distributions (see Figure 1), and is quantified by their tortuosity, a stochastic parameter that is evaluated using the arc length of each CNT. This CNT arc length is matched to the experimentally evaluated CNT waviness ratio, an analytical parameter, using the arc length of a sine wave. Arrays comprised of > 105 stochastic wavy CNTs are assembled in a layer-by-layer fashion, where each layer is comprised of the square root of the total number of CNTs in the simulation. This technique could enable CNT structures to be studied at true scale, where a CNT simulation comprised of > 106 stochastic wavy CNTs could have an area of 0.1 mm x 0.1 mm.
                    
 Using their intrinsic longitudinal (Y) and shear (G) moduli, the effective stiffness of the CNTs that reinforce the A-PNCs is evaluated (see Figure 2(a)). As Figure 2(a) illustrates, the effective reinforcement modulus of CNTs is diminished as their waviness increases, but this effect is not as pronounced when the ratio of Y/G is small. Using the effective stiffness of the CNTs, the elastic response of the A-PNCs in the longitudinal direction is also quantified and compared to experimental results and previous predictions by a finite element method assuming a constant waviness ratio (see Figure 2 (b)). Figure 2(b) shows that by more accurately describing the waviness of the CNTs and their evolution with the CNT volume fraction, which is controlled using Λ, the current method is able to explain the observed enhancements in the A-PNC modulus as a function of the CNT volume fraction. This implies that using representative descriptions of the CNT morphology, more accurate material property turning and prediction may become possible.
                     
More information about this research can be found in the journal Nanotechnology 27 035701.

< Previous Carbon nanotube template produces sub...New Technique Facilitates Isolation a... Next >

?
Tel:+86-28-85241016,+86-28-85236765    Fax:+86-28-85215069,+86-28-85223978    E-mail:carbon@cioc.ac.cn,times@cioc.ac.cn,nano@cioc.ac.cn
QQ:800069832    Technical Support ac57.com
Copyright © Chengdu Organic Chemicals Co. Ltd., Chinese Academy of Sciences 2003-2025. manage 蜀ICP備05020035號-3
主站蜘蛛池模板: 国产在视频线精品视频www666 | 色老久久 | 亚洲国产影院 | 亚洲第一大网站 | 人成免费a级毛片 | 亚州视频一区 | 一区二区三区日本视频 | 欧美一级色视频 | 国产亚洲欧美在线播放网站 | 中文国产成人精品久久无广告 | 亚洲欧美二区三区久本道 | 国产一区二区三区欧美精品 | 国产男女猛烈无遮档免费视频网站 | 日本在线不卡免 | 精品视频一区二区三区 | 国产毛片久久精品 | 日本一级特黄高清ab片 | 热99re久久精品2久久久 | 欧美亚洲一区 | 国产一区二区三区免费在线视频 | 女同日韩互慰互摸在线观看 | 亚洲在线视频一区 | 亚洲毛片免费看 | 久草在线视频资源站 | 日韩中文字幕视频 | 欧美精品一区二区三区免费观看 | 日本妞xxxxxxxxx69| 久久黄色一级视频 | 男女国产一级毛片 | 一区二区精品在线观看 | 一级毛片成人午夜 | 精品国产高清在线看国产 | japanese日本tube色系 | 特黄视频 | 色偷偷88欧美精品久久久 | 成人软件18免费 | 在线观看亚洲免费 | 日本一区二区在线 | 婷婷的久久五月综合先锋影音 | 美女18网站 | 精品无人区一区二区三区a 精品午夜国产在线观看不卡 |