碳纳米管／环氧树脂复合材料高低温弹性模量的分子模拟与实验研究

发布时间：2018-06-22 03:50

本文选题：碳纳米管 + 环氧树脂　；参考：《北京化工大学》2016年硕士论文

【摘要】：航空航天用碳纤维/树脂基复合材料,由于其应用环境的温度变化范围大,所以在工程应用中必须掌握树脂基体在不同温度条件下力学性能的变化趋势以及与微观交联结构的联系。研究表明,纤维增强体与树脂基体之间存在一个模量过渡区域,当纤维的种类和体积分数一定时,提高基体的模量,可以有效地减小复合材料界面处的剪切应力集中系数,从而能够提高复合材料的层剪、弯曲等性能。碳纳米管(CNTs)因其出色的力学性能,被用于提高树脂基体高低温环境下的弹性模量,探究这一提高作用的微观机理是指导设计优异力学性能环氧树脂基复合材料的关键。针对上述问题,本文采用计算机分子模拟和实验相结合的方法分析了不同交联结构的环氧树脂基体的弹性模量随温度的变化,以及碳纳米管对环氧树脂高低温弹性模量的影响,并用模拟软件从微观角度对实验结果进行了解释,建立起微观结构与宏观弹性模量的联系,为设计高性能环氧树脂基体复合材料提供理论基础。具体工作如下：通过模拟软件构建了DDM/E51和DDS/E51不同交联结构的树脂基体模型,通过分子动力学模拟与实验相结合的方法研究了各树脂体系的玻璃化转变温度(Tg)和从低温环境到Tg范围内的一系列温度点的弹性模量。发现树脂基体的弹性模量随着温度升高而减小,模拟值与实验值结果较为一致。这主要是由于随着温度的升高,树脂基体的内聚能密度和链段堆砌密度不断减小,而链段运动能力和自由体积分数不断变大等微观因素导致的。构建SWCNTs/DDM/E51和SWCNTs/DDS/E51单壁碳纳米管改性的环氧树脂交联结构模型,模拟和实验的结果均发现单壁碳纳米管提高了树脂基体的Tg和每个温度点的弹性模量,并降低了体积热膨胀系数。主要是因为单壁碳管增强了基体的刚性,限制了分子链段的运动能力,减小了自由体积分数,提高了基体的内聚能密度和链段堆砌密度。单壁碳管对链段堆砌密度的提高效果在各温度点基本一致；对自由体积分数和链断运动能力的减小效果在低温环境下可忽略,但在室温以上非常明显,从而提高了树脂基体的耐高温性能。
[Abstract]:Carbon fiber / resin matrix composites for aerospace applications have a large range of temperature variations in its application environment, so it is necessary to master the change trend of the mechanical properties of the resin matrix under different temperature conditions and the connection with the microscopic cross-linking structure in the engineering application. When the type and volume fraction of the fiber are fixed, the modulus of the matrix can be improved, and the shear stress concentration coefficient at the interface of the composite can be reduced effectively, thus the laminar shear and bending properties of the composite can be improved. Because of its excellent mechanical properties, carbon nanotube (CNTs) is used to improve the projectile under the high and low temperature environment of the resin matrix. The key to the design of epoxy resin matrix composites with excellent mechanical properties is the micromoduli, which is the key to the design of the enhanced mechanical properties of epoxy resin matrix composites. The influence of the elastic modulus of epoxy resin at high and low temperature was explained, and the experimental results were explained from the micro angle with the simulation software. The relationship between the microstructure and the macro modulus of elasticity was established. It provided a theoretical basis for the design of high performance epoxy resin matrix composites. The specific work is as follows: the DDM/E51 and DDS/E51 are constructed by the simulation software. The elastic modulus of the glass transition temperature (Tg) and a series of temperature points from the low temperature environment to the Tg range are studied by the method of molecular dynamics simulation and experiment. It is found that the elastic modulus of the resin matrix decreases with the increase of temperature, and the simulation value and the experimental value are the same. The results are the same. This is mainly due to the increase of temperature, the decreasing of the density of the polymer matrix and the density of the chain section, the movement capacity of the chain segments and the increasing free volume fraction. The structure of the epoxy resin crosslinked structure model of the modified SWCNTs/DDM/E51 and SWCNTs/DDS/E51 single wall carbon nanotubes is modeled. It is found that the single wall carbon nanotube improves the Tg of the resin matrix and the modulus of the elastic modulus at each temperature point, and reduces the volume thermal expansion coefficient, mainly because the single wall carbon tube strengthens the rigidity of the matrix, restricts the movement ability of the molecular chain, reduces the free volume fraction, and improves the cohesive energy density and chain of the matrix. The increase of the density of the single wall carbon tube is basically the same at the temperature points, and the reduction effect on the free volume fraction and the chain breaking ability can be ignored in the low temperature environment, but it is very obvious at the room temperature, thus improving the high temperature resistance of the resin matrix.
【学位授予单位】：北京化工大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TQ323.5;TB332

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