Cellulose crystals plastify by localized shear

Area of Science:

• Materials Science
• Biomaterials
• Computational Modeling

Background:

• Cellulose microfibrils are key structural components in plants and wood.
• Their crystalline domains offer excellent mechanical properties, suggesting potential as sustainable reinforcements.
• The elastoplastic behavior of cellulose crystals is not well understood.

Purpose of the Study:

• To investigate the plastic shear resistance of cellulose crystals using atomistic simulations.
• To analyze the atomic mechanisms governing deformation in cellulose crystals.
• To understand how cellulose's atomic structure influences its anisotropic elastoplastic properties.

Main Methods:

• Atomistic simulations were employed.
• Plastic shear resistance was determined.
• Atomic deformation mechanisms were analyzed.

Main Results:

• Shear in perfect cellulose crystals occurs via localized bands with significant dilatancy.
• Anisotropic elastoplastic behavior is controlled by the cellulose crystal's atomic structure.
• Noncovalent interactions, chain translations, and rotations influence crystal response to shear.
• Crystalline defects, such as dislocations, reduce yield strength and dilatancy, similar to metals.

Conclusions:

• The study elucidates the atomic-level deformation mechanisms in cellulose crystals.
• Understanding these mechanisms is crucial for utilizing cellulose as a reinforcing material.
• Defects significantly impact the mechanical properties of cellulose crystals.