Department of Aeronautics, Imperial College London, South Kensington Campus, London, SW7 2AZ, UK.
Sci Rep. 2020 Sep 17;10(1):15260. doi: 10.1038/s41598-020-72153-w.
Nanocellulose network in the form of cellulose nanopaper is an important material structure and its time-dependent mechanical response is crucial in many of its potential applications. In this work, we report the influences of grammage and strain rate on the tensile response of bacterial cellulose (BC) nanopaper. BC nanopaper with grammages of 20, 40, 60 and 80 g m were tested in tension at strain rates ranging from 0.1% s to 50% s. At strain rates [Formula: see text] 2.5% s, both the tensile modulus and strength of the BC nanopapers stayed constant at ~ 14 GPa and ~ 120 MPa, respectively. At higher strain rates of 25% s and 50% s however, the tensile properties of the BC nanopapers decreased significantly. This observed anomalous tensile response of BC nanopaper is attributed to inertial effect, in which some of the curled BC nanofibres within the nanopaper structure do not have enough time to uncurl before failure at such high strain rates. Our measurements further showed that BC nanopaper showed little deformation under creep, with a secondary creep rate of only ~ 10 s. This stems from the highly crystalline nature of BC, as well as the large number of contact or physical crosslinking points between adjacent BC nanofibres, further reducing the mobility of the BC nanofibres in the nanopaper structure.
纳米纤维素网络以纤维素纳米纸的形式存在，是一种重要的材料结构，其随时间变化的力学响应在许多潜在应用中至关重要。在这项工作中，我们报告了定量和应变速率对细菌纤维素（BC）纳米纸拉伸响应的影响。在应变率为 0.1% s 至 50% s 的范围内，对定量为 20、40、60 和 80 g/m 的 BC 纳米纸进行了拉伸测试。在应变速率 [Formula: see text] 2.5% s 时，BC 纳米纸的拉伸模量和强度分别保持在约 14 GPa 和约 120 MPa。然而，在应变率为 25% s 和 50% s 时，BC 纳米纸的拉伸性能显著下降。BC 纳米纸这种观察到的异常拉伸响应归因于惯性效应，在这种效应中，纳米纸结构中的一些卷曲的 BC 纳米纤维在如此高的应变率下失效之前没有足够的时间展开。我们的测量进一步表明，BC 纳米纸在蠕变下几乎没有变形，二次蠕变速率仅约为 10 s。这源于 BC 的高结晶性质，以及相邻 BC 纳米纤维之间大量的接触或物理交联点，进一步降低了纳米纸结构中 BC 纳米纤维的迁移率。
