An atomistic study on the mechanical behavior of bamboo cell wall constituents

Abstract

Although the bamboo material has excellent mechanical properties, the anisotropic mechanical properties across and along the bamboo culm hinder its use as the structural material. As the bamboo fibers are the source of the mechanical properties for bamboo, a fundamental understanding on the structure and mechanical behaviors of bamboo fiber and its constituents enables us to figure out the origin of the anisotropic mechanical properties. In this work, the mechanical response of the cellulose, hemicellulose, and lignin under uniaxial tensile at the strain rate of 108 s−1 is investigated by molecular dynamics simulation and the molecular conformational change under the tensile deformation is in situ captured. The breakage of the hydrogen bonds and slippage of the linear polymer chains are dominant for the failure of the cellulose. The normal stress dominated fracture mechanism is the key to the failure of the hemicellulose whereas the shear stress dominated fracture mechanism is the main failure mode for the lignin. The revealed relationship between the structure and mechanical properties of the cell wall constituents in bamboo fibers provides a guideline for assembling of the basic constituents and for modifying their structure to obtain a material that has isotropic mechanical properties and maintains the excellent mechanical properties of the bamboo.