纳米金球—聚合物基体界面力学性能研究

发布时间：2018-06-30 19:42

本文选题：纳米金球 + 聚合物基体　；参考：《江苏大学》2017年硕士论文

【摘要】：近十年来,柔弹性导电复合材料因其高弹性、高导电性的优越性能而备受关注,在开发可弯曲和可拉伸的电子和光电子产品中起着不可或缺的作用。以金属橡皮为代表的柔弹性导电复合材料的出现,将极大地促进相关产业的技术革新与智能化发展。与传统复合材料的连续界面不同,纳米复合材料中第二相的纳米尺度效应使得纳米第二相与基体间的范德华作用增大,形成了独特的“纳米第二相-基体”纳观界面。这一界面构成了纳米第二相与基体之外的“第三相”,其对材料的纳观结构以及宏观材料的整体力学行为和性能都具有显著的影响,因此对于该纳观界面本构关系的建立、力学行为及性能的研究是准确表征该类纳米复合材料力学行为的关键点。目前对纳米金球-聚乙烯基体界面力学性能的理论分析,以及分子动力学模拟尚未见文献报道,对金属橡皮这一新型材料的纳观界面的研究仍具有很大的挑战性。本文采用多尺度模拟方法,一方面,基于连续力学方法和蒙特卡罗方法,建立“单个纳米金球+聚乙烯基体”和纳米金球复合材料两种模型,研究纳米复合材料中“纳米第二相-基体”界面的力学行为及性能;另一方面,利用分子动力学模拟,比较“纯聚乙烯”和“纳米金球-聚乙烯”这两种模型,研究纳观界面和环境变量对纳米复合材料整体性能的影响。主要研究成果如下:(1)基于Lennard-Jones势,首次推导出了“球形纳米填料-基体”界面的内聚能量和内聚应力的解析式。(2)基于上述解析式,研究发现随着金球半径的增大,界面的内聚能量(每单位面积)和内聚强度均提高。并且在较小半径下,曲率效应作用很强,随着半径的增大作用逐渐减弱,最后可忽略不计。(3)以往的研究均基于稀溶液假设,不考虑金球之间的相互作用。本文首次探讨了周围纳米复合材料中的金球对界面的影响,并且提出了稀溶液假设的适用范围。(4)基于分子动力学模拟,研究金球半径和体积分数、温度、应变速率对材料力学性能参数(杨氏模量、屈服应力/应变、断裂应力/应变)的影响,通过比较得出“纳米金球-聚乙烯”体系区别于“纯聚乙烯”体系的纳观特性。
[Abstract]:In recent ten years, flexible and elastic conductive composites have attracted much attention because of their excellent properties of high elasticity and high conductivity, which play an indispensable role in the development of flexible and extensible electronic and optoelectronic products. The appearance of flexible elastic conductive composites represented by metal erasers will greatly promote the technological innovation and intelligent development of related industries. Different from the continuous interface of the traditional composites, the nanoscale effect of the second phase in the nanocomposites increases the van der Waals interaction between the nano-second phase and the matrix, forming a unique "nano-second phase-matrix" nano interface. This interface constitutes the "third phase" outside the second phase and the matrix, which has a significant effect on the nano structure of the material, as well as on the overall mechanical behavior and properties of the macroscopic material. Therefore, the constitutive relationship of the nano interface is established. The study of mechanical behavior and properties is the key point to accurately characterize the mechanical behavior of this kind of nanocomposites. At present, the theoretical analysis of the interface mechanical properties of nano-gold ball and polyethylene matrix and the molecular dynamics simulation have not been reported in the literature, and the study of the nano interface of metal rubber, a new material, is still very challenging. On the one hand, based on the continuous mechanics method and Monte Carlo method, two kinds of models of "single gold ball polyethylene matrix" and nano-gold ball composite material are established by using multi-scale simulation method. The mechanical behavior and properties of the interface between "nano-second phase and matrix" in nanocomposites were studied. On the other hand, the two models of "pure polyethylene" and "nano-gold ball polyethylene" were compared by molecular dynamics simulation. The effects of nano interface and environmental variables on the overall properties of nanocomposites were studied. The main results are as follows: (1) based on Lennard-Jones potential, the analytical expressions of cohesive energy and cohesive stress of "spherical nano-filler matrix" interface are derived for the first time. (2) based on the above analytical formula, it is found that with the increase of the radius of gold sphere, The cohesive energy (per unit area) and cohesion strength of the interface are increased. Moreover, the curvature effect is very strong in a small radius, which weakens gradually with the increase of radius. (3) the previous studies are based on the assumption of dilute solution and do not consider the interaction between the gold spheres. In this paper, the influence of the gold ball in the surrounding nanocomposites on the interface is discussed for the first time, and the applicable range of the dilute solution hypothesis is proposed. (4) based on the molecular dynamics simulation, the radius, volume fraction and temperature of the gold sphere are studied. The effect of strain rate on the mechanical properties of materials (Young's modulus, yield stress / strain, fracture stress / strain) was studied.
【学位授予单位】：江苏大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB33;TB383.1

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