Université Grenoble Alpes, CNRS, Grenoble Institute of Technology, Laboratoire Sols, Solides, Structures, Risques, F-38000 Grenoble, France.
Université de Lyon, CNRS, Institut Lumière Matière, F-69622 Villeurbanne, France.
Proc Natl Acad Sci U S A. 2018 Jul 10;115(28):7260-7265. doi: 10.1073/pnas.1800098115. Epub 2018 Jun 20.
Cellulose microfibrils are the principal structural building blocks of wood and plants. Their crystalline domains provide outstanding mechanical properties. Cellulose microfibrils have thus a remarkable potential as eco-friendly fibrous reinforcements for structural engineered materials. However, the elastoplastic properties of cellulose crystals remain poorly understood. Here, we use atomistic simulations to determine the plastic shear resistance of cellulose crystals and analyze the underpinning atomic deformation mechanisms. In particular, we demonstrate how the complex and adaptable atomic structure of crystalline cellulose controls its anisotropic elastoplastic behavior. For perfect crystals, we show that shear occurs through localized bands along with noticeable dilatancy. Depending on the shear direction, not only noncovalent interactions between cellulose chains but also local deformations, translations, and rotations of the cellulose macromolecules contribute to the response of the crystal. We also reveal the marked effect of crystalline defects like dislocations, which decrease both the yield strength and the dilatancy, in a way analogous to that of metallic crystals.
纤维素微纤维是木材和植物的主要结构构建块。它们的结晶域提供了出色的机械性能。因此，纤维素微纤维具有作为结构工程材料的环保纤维增强材料的显著潜力。然而，纤维素晶体的弹塑性性质仍未得到很好的理解。在这里，我们使用原子模拟来确定纤维素晶体的塑性剪切阻力，并分析其基础原子变形机制。特别是，我们展示了结晶纤维素复杂而适应性强的原子结构如何控制其各向异性弹塑性行为。对于完美的晶体，我们表明剪切是通过局部带沿带有明显的膨胀发生的。根据剪切方向，不仅纤维素链之间的非共价相互作用，而且纤维素大分子的局部变形、平移和旋转都会对晶体的响应产生贡献。我们还揭示了类似于金属晶体的方式，晶体缺陷（如位错）对屈服强度和膨胀的明显影响。
