Effective Young鈥檚 Modulus of Bacterial and Microfibrillated Cellulose Fibrils in Fibrous Networks

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• 作者：Supachok Tanpichai ; Franck Quero ; Masaya Nogi ; Hiroyuki Yano ; Robert J. Young ; Tom Lindstr枚m ; William W. Sampson ; Stephen J. Eichhorn
• 刊名：Biomacromolecules
• 出版年：2012
• 出版时间：May 14, 2012
• 年：2012
• 卷：13
• 期：5
• 页码：1340-1349
• 全文大小：647K
• 年卷期：v.13,no.5(May 14, 2012)
• ISSN：1526-4602

文摘

The deformation micromechanics of bacterial cellulose (BC) and microfibrillated cellulose (MFC) networks have been investigated using Raman spectroscopy. The Raman spectra of both BC and MFC networks exhibit a band initially located at 1095 cm^鈥?. We have used the intensity of this band as a function of rotation angle of the specimens to study the cellulose fibril orientation in BC and MFC networks. We have also used the change in this peak鈥檚 wavenumber position with applied tensile deformation to probe the stress-transfer behavior of these cellulosic materials. The intensity of this Raman band did not change significantly with rotation angle, indicating an in-plane 2D network of fibrils with uniform random orientation; conversely, a highly oriented flax fiber exhibited a marked change in intensity with rotation angle. Experimental data and theoretical analysis shows that the Raman band shift rate arising from deformation of networks under tension is dependent on the angles between the axis of fibrils, the strain axis, the incident laser polarization direction, and the back scattered polarization configurations. From this analysis, the effective moduli of single fibrils of BC and MFC in the networks were estimated to be in the ranges of 79鈥?8 and 29鈥?6 GPa, respectively. It is shown also that for the model to fit the data it is necessary to use a negative Poisson鈥檚 ratio for MFC networks and BC networks. Discussion of this in-plane 鈥渁uxetic鈥?behavior is given.