"It is challenging to experimentally determine the micro-friction mechanism of cotton fiber and metal in the sliding process. The influence of load and temperature on the interface behavior during dry friction between amorphous cotton fiber and chromium, the contact interface evolution and friction coefficient are studied using reactive molecular dynamics. The simulation results show that chromium–oxygen bonds are formed on the contact interface of the friction system during the sliding process. Furthermore, the relationship between friction coefficient, temperature, and load varies with the mechanical state of cotton cellulose. The relationship is positive when the cotton cellulose is in the glassy state. However, when cotton cellulose is in a highly elastic state, its friction coefficient is negatively related to the load. This study systematically evaluated the effects of temperature and load on the slip process from the atomic scale, provided a reason for the wear of the hard materials of the friction pair, and provided theoretical support for the study of this type of friction mechanism."

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At present, most high-performance cellulose matrix composites only use cellulose as reinforcement material, which is an obstacle to maximize the advantages of nanocellulose in structure and properties. The development of new functional nanocomposites with cellulose as the main component can better meet people’s needs for high-performance and degradable composites, which requires a comprehensive and thorough understanding of cellulose. Considering the limitations of physical experiments, we performed molecular dynamics simulation of the uniaxial tensile behavior of the cellulose system at three different strain rates (10−4/ps, 10−5/ps, and 10−6/ps), and the stress-strain responses of cellulose systems at different strain rates are obtained. The effect of the strain rate on the mechanical properties of amorphous cellulose system during the tensile processes is analyzed. The deformation mechanism of cellulose amorphous system during the tensile processes is characterized by the energy changes of the different terms including dihedral angle torsion term, bond tensile term, angle bending term, and nonbond term. Structural evolution of the cellulose crystal system during the tensile processes is used to explain the failure mechanism of cellulose. The kinetic simulation results show that the mechanical properties of the cellulose amorphous system increase with the increase of strain rate. Compared with the strain rate of 10−5/ps, the elastic modulus of the system increases by 6.73 GPa at the strain rate 10−4/ps. During the tensile processes, cellulose amorphous region adapts to the applied load mainly through the stretching of the cellulose macromolecular chains, i.e., the deformation of bond lengths and bond angles, without any breakage of the molecular chains. The main causes of chain lengthening at different strain rates are different. The failure of cellulose is caused by the slip and rearrangement of some molecular chains in the crystal structure.

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