Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 115, Issue 28, Pages 7260-7265Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1800098115
Keywords
crystalline cellulose; nanoscale plasticity; shear bands; dislocations; molecular mechanics simulation
Categories
Funding
- Laboratoire d'Excellence [Labex Tec21, Agence Nationale de la Recherche (ANR)] [ANR-11-LABX-0030]
- Laboratoire d'Excellence Institute for Multiscale Science and Technology (Labex iMUST, ANR) of Universite de Lyon (ANR) [ANR-10-LABX-0064, ANR-11-IDEX-0007]
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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.
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