【作者】 姜勇；

【导师】 张平；

【作者基本信息】 湘潭大学 ， 一般力学与力学基础， 2009， 博士

【摘要】 聚合物基纳米复合材料是一种重要的新型材料,具有不同于宏观复合材料的许多优异性能,为新材料的研究和制备提供了新方向和新途径,倍受世界各国重视。由于聚合物基纳米复合材料增强相特征尺度在几十纳米量级,远小于长链高分子的链长,其内部结构(高分子单元结构、链结构和聚集态结构等)具有跨物质层次多尺度构筑特征,采用经典的细观力学、连续介质力学和流变学理论模型的描述受到局限,本文在聚合物基纳米复合材料制备的基础上,尝试使用多尺度均匀化理论对其力学性能进行研究。本文对聚合物基纳米复合材料的制备、性能及其相关力学问题进行了研究。主要研究内容和创新成果如下:1.制备了四氨基铜钛菁纳米粒子和二氧化硅纳米粒子,在此基础上,采用原位聚合法制备了尼龙6/二氧化硅纳米复合材料和尼龙6/四氨基铜钛菁纳米复合材料。描述并表征这两类纳米复合材料的微结构,实验分析了这两类材料的力学性能和部分功能性特性。实验结果表明,尼龙6/二氧化硅纳米复合材料中的纳米粒子含量为5%时,纳米复合材料的拉伸强度、拉伸弹性模量比纯尼龙6分别提高了41%和47%;当纳米粒子的含量为3%时,纳米复合材料的冲击强度和显微硬度分别比纯尼龙6提高了59%和32%。当尼龙6/四氨基铜钛菁纳米复合材料中的纳米粒子含量为0.8%时,纳米复合材料的拉伸强度、拉伸弹性模量和冲击强度比纯尼龙6分别提高了12%、24%和139%。四氨基铜钛菁纳米粒子的加入使得尼龙6/四氨基铜钛菁纳米复合材料的紫外滤光性、抗紫外老化能力以及红外蓄热、保温性得到了明显的提高。2.基于所制备的纳米复合材料的微结构特性及宏观力学性能,建立了基于微结构特性的多尺度力学模型,对每一层次都视为周期性结构,采用逐次双尺度均匀化方法,讨论了聚合物结晶度、聚合物结晶相弹性模量、纳米颗粒弹性模量和纳米颗粒体积分数等参数对聚合物基纳米复合材料等效弹性模量的影响,计算获得了材料的宏观等效力学参数。将理论计算结果与实验结果进行了对比,结果表明,在理论条件满足的前提下,即纳米颗粒分散均匀的情况下,两者基本吻合,从而验证了理论模型的正确性。3.多孔材料是一种轻质的结构材料,在其基体材料中添加纳米颗粒可以赋予其一定的功能性,但是同时也带来其结构中的多尺度问题。为了更好地了解纳米颗粒对多孔聚合物基纳米复合材料的影响,通过甲基丙烯酸甲酯本体聚合发泡的新方法,实验制备了多孔PMMA/二氧化硅纳米复合材料和多孔PMMA/二氧化钛纳米复合材料;对二氧化钛纳米颗粒的功能性进行了一些实验研究;对所得复合材料的力学性能进行了实验研究,分析了实验结果;实验结果表明,复合材料的压缩应力-应变曲线具有多孔泡沫材料明显的三阶段特征即线弹性段、塑性屈服平台段及致密段;随着复合材料中纳米颗粒含量的增加,材料的压缩弹性模量也随之增大;而对于同一纳米颗粒含量的复合材料来说,随着变形速率的增大,材料的抗压强度随之增大。4.采用多尺度逐次均匀化理论建立了多孔聚合物基纳米复合材料的理论模型,研究了复合材料的宏观等效弹性常数与聚合物基体材料以及纳米粒子的材料常数、纳米粒子的含量之间的关系;将理论计算结果与实验结果进行了对比,结果表明,理论结果偏大,而两者的增长趋势一致,这说明理论结果与实验结果吻合,从而验证了理论模型的正确性。更多还原

【Abstract】 Polymeric nanocomposite is an important new material. It has many excellent properties which being differ from macroscopical composite materials, and gives new direction and approach to research and prepare new materials. Therefor, it gets much regard in the world. The characteristic scale of the polymeric nanocomposite’s reinforcement is a few decades nanometer levels, which less than the cable length of the long-chain macromolecule. The inner structures(the cell strutures of the macromolecule, chain structures, aggregative state structures etc.) of the polymeric nanocomposite have multiscale build characteristics of spanning matter layers. Adopting classical micromechanics, continuity mechanics and rheology theory models to describe them had been localization. In this paper, basing on the preparation of the polymeric nanocomposite, we tried to study their mechanics properties by using multiscale homogenization theory.In this paper, the preparation, properties and related mechanics issues of polymeric nanocomposites have been studied. Main research contents and creative results as follows:1. Basing on the preparation of (NH2)4PcCu and SiO2 nanograins, the PA6/SiO2 nanocomposites and the PA6/(NH2)4PcCu nanocomposites were prepared by in-situ polymerization. Their microcosmic structure characteristics were described and their mechanics and functional properties were studied. The results indicated that when the content of the SiO2 nanograins is 5%, the tensile strength and elastic module of the PA6/SiO2 nanocomposites increase 41% and 47% than pure PA6; when the content of the SiO2 nanograins is 3%, the impact strength and microhardness of the nanocomposites increase 59% and 32% than pure PA6. When the content of the (NH2)4PcCu nanograins is 0.8%, the tensile strength, elastic module and impact strength of the PA6/(NH2)4PcCu nanocomposites increase 12%, 24% and 139% than pure PA6. The ultraviolet filtration, anti-ultraviolet aging and the infrared thermal storage retardation of the PA6/(NH2)4PcCu nanocomposites had obviously improved with the addition of the (NH2)4PcCu nanograins.2. Basing on the microcosmic structure characteristics and mechanics properties of the nanocompsities, the multiscale analysis model was built. The influences of the model’s parameters including the polymer crystallinity, the elastic module of the polymer crystal, the elastic modulus of the nanograin and the nanograin’s fraction on the equivalent elastic modulus of the polymeric nanocomposite were discussed by the multiscale homogenization method. We had compared the experiment results with the theory results, the results indicated that the experiment results basically tallied with the theory results, on the premise of the theory coming into existence, i.e., in case of nanograin dispersing evenly. Therefor, the validity of the model was validated.3. Porous materials are a sort of lightweight structural materials. The accession of the nanograins in its matrix material could endow it with definite functionality, and brought the multiscale questions in its structure. For better understanding the influence of the nanograins on the porous polymeric nanocomposites, the PMMA porous material, the porous PMMA/SiO2 nanocomposites and the porous PMMA/TiO2 nanocomposites were prepared by MMA itself polymerization foaming method. We studied the functionality of the TiO2 nanograins initially. Their mechanics properties were studied and the experiment results were analyzed. The results indicated that the compressive stress-strain curves of the nanocomposites had obvious three phases characters of the porous foams, i.e., linear elastic phase, plastic yield flat phase and compact phase. Along with the nanograins content of the nanocomposites increasing, the compressive elastic modulus of the nanocomposites augmented. The nanocomposites that which had the same nanograins content, with the transfiguration speed increasing, their compressive strength added.4. The theory model of the porous polymeric nanocomposite was built by the multiscale successive homogenization theory. The relations between the macroscopical equivalent elastic constant of the nanocomposites and the material constant of the polymeric matrix materials and the nanograins and the nanograins content were studied. We had compared the experiment results with the theory results, the results indicated that the former was a little less than the latter in magnitude, but both of their increase trends were accordantly. Thus it shown that the experiment results were accorded with the theory results, the validity of the model was validated.更多还原