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总览 评价 胡恩来 ， 孙毅 * ， 曾凡林 （ 哈尔滨工业大学，航天科学与力学系，哈尔滨，150001； ） 摘要： 本文应用分子力学模拟方法研究了纯聚乙烯和POSS增强的聚乙烯在金刚石三棱锥压头作用下的纳米压痕试验。结果表明，加入POSS之后，聚乙烯材料的硬度由
胡恩来， 孙毅*， 曾凡林
（
哈尔滨工业大学，航天科学与力学系，哈尔滨，150001； ）
摘要：
本文应用分子力学模拟方法研究了纯聚乙烯和POSS增强的聚乙烯在金刚石三棱锥压头作用下的纳米压痕试验。结果表明，加入POSS之后，聚乙烯材料的硬度由0.337GPa变为0.715GPa，提高了112%；弹性模量由5.89GPa变为9.37GPa，提高了59.1%。本文计算了压头尖端附近的原子平均位移并从这个角度阐明了POSS对变形的抑制作用。通过对两根链模型的拉伸模拟，证明了滑移力所做的功相当于体系的能量损耗。从平均位移、应力分布和损耗能的角度研究了载荷-位移曲线中的载荷突降现象，分析了载荷突降的原因，发现滑移是载荷突降的主要原因。引入了滑移能密度的概念来比较变形过程中滑移的大小，结果显示，POSS抑制了PE分子链的滑移。
关键词：
纳米压痕；分子力学；载荷突降；滑移；平均位移
Hu Enlai， Sun Yi*， Zeng Fanlin
（
Dept. of Astronautic Science and Mechanics, Harbin Institute of Technology, Harbin, China, 150001； ）
Abstract：
In this paper, the nanoindentation tests on the two models of neat polyethylene (PE) and the polyethylene incorporated with 25wt% POSS (POSS-PE) are performed to reveal the reinforcing mechanism of the mechanical properties. The molecular mechanics method is adopted to eliminate the temperature effects. After the loading and unloading processes, the hardness and Young's modulus are calculated through the curve of loading versus displacement. Compared with PE, these mechanical properties of POSS-PE are improved dramatically. To interpret such enhancement effect, first we compare the average displacements of two models. The results show that the average displacement of POSS-PE is much smaller than that of PE, i.e., the deformation of PE is restrained by POSS unit. Utilizing the slipping models, we then analyze the relationship between loading drop phenomenon and slipping energy. From the simulation results, it is believed that the protrudent slipping energy is corresponding to the loading drop exactly, and the slipping between molecular chains is the main source of the loading drop. Furthermore, the average slipping energy of POSS-PE is smaller than that of PE, which implies that the slipping of PE is suppressed by POSS unit.
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