Mechanical properties of cellulose Iβ crystal were studied using molecular dynamics. Firstly, mechanical properties of the cellulose Iβ crystal model offered by Nishiyama were calculated. By analyzing the mechanical parameters of cellulose Iβ crystal, it was found that the cellulose Iβ crystal was the anisotropic elastic material whose elasticity was much bigger in the direction of chains of cellulose molecules than other two directions and had good ductility. The Young's modulus also agreed with the data which was calculated by Tanaka. Subsequently, the mechanical properties of cellulose Iβ crystals were calculated under the transformer operating temperatures. The changes of mechanics parameters were not obvious under the transformer temperatures. The same law was also found when calculating the density of hydrogen bond in the crystals under different temperatures, but the standard deviation of the density of hydrogen bond became bigger when the temperature increased, reflecting the influence of temperature to the stability of cellulose crystals. Through analysis of density distribution in the direction of crystal layer, with the temperature increasing, the standardized crystal structure became weakened. Finally the movement of chains had been studied and found that the higher the temperature was, the more intensely the movement of chains were, which agreed with the result manifested by the density of hydrogen bond.%利用分子动力学,对纤维素Iβ晶体在不同温度下的熟力学性能进行了研究.采用Nishiyama等给出的纤维素Iβ晶体数据模型,计算了晶体的力学参数.数据表明,纤维素Iβ晶体具有良好的延展性,为各向异性弹性材料,在纤维素链方向的弹性较强;计算得到的杨氏模量与Tanaka等的计算值相符.在变压器运行温度下对纤维素Iβ晶体的力学性能的研究表明,不同温度下晶体的力学参数无明显变化,说明变压器运行的温度范围对纤维素Iβ晶体的力学性能并未构成实质性的影响,与老化实验中纤维素纸结晶度的变化规律相吻合;不同温度时晶体内氢键密度变化亦不明显,但晶体内氢键密度的标准差随温度的增加而变大,反映出温度对纤维素晶体稳定性的影响;晶体层间方向的密度随温度的升高,晶体结构的有序性被弱化.最后对纤维素的链运动进行了研究,发现温度越高,链运动越加强烈,与晶体内氢键密度的变化规律相对应.
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