SU-8胶及其复合材料力学和阻尼特性的分子动力学模拟
发布时间：2019-04-19 18:07
【摘要】：近年来,聚合物材料的研究成为了当前国内外学者的研究重点,许多研究者致力于开发新的材料配方、改进已有材料,希望能够合成天然的、具有优异特性的仿生材料。因此,本文基于SU-8光刻胶在MEMS领域的广泛应用,运用分子动力学的研究方法,针对SU-8胶及复合材料的力学、热力学及阻尼性能等进行研究。不仅能够实现材料宏观性质的预测,还有助于从微观上认识和解析出材料宏观现象产生的机理。首先,本文结合分子力学和分子动力学的基本理论,分析了适合聚合物材料研究的分子动力学的力场、系综、边界等条件,提出了基于COMPASS分子力场,经过分子聚合、能量最小化和退火模拟等构建非交联和交联的SU-8光刻胶模型的方法。计算得到了SU-8胶在室温条件下的杨氏模量、泊松比等力学性能参数,并将模拟结果与实验结果对比证明了建立材料模型方法的可行性以及分子动力学算法的有效性。其次,建立SU-8胶和不同类型碳纳米管共混的复合材料模型,利用分子动力学的方法研究不同类型的碳纳米管对材料力学性能的影响,结果表明：碳纳米管可以极大的提高材料力学性能；随着碳纳米管管径增加复合材料杨氏模量逐渐减小；同时证明了相对于单壁碳纳米管而言,双壁碳纳米管更能显著改善材料力学性能。再次,利用分子动力学模拟研究了SU-8胶的玻璃化转变行为及其主要的影响因素,预测得到了非交联和交联SU-8胶的玻璃化转变温度分别为326.7K和494.8K。着重讨论了力场能量项对玻璃化转变温度的影响,得到非键能的改变是影响玻璃化转变的主要因素,有助于深入理解玻璃化转变过程的本质和研究材料阻尼性能的微观机理。同时,利用动态机械分析(DMA)实验测试得到了不同工艺参数的SU-8胶玻璃化转变温度。最后,计算了SU-8胶及复合材料的氢键、径向分布函数、自由体积分数和结合能等相关参数。通过计算复合材料界面结合能来得到碳纳米管和SU-8胶的结合强度；通过计算SU-8胶的氢键和径向分布函数,可知分子内和分子间的相互作用方式；通过复合材料自由体积的计算,结合自由体积的变化对玻璃化转变的影响,讨论了自由体积和氢键等参数对于材料阻尼性能的影响,为聚合物基阻尼复合材料的设计提供参考。
[Abstract]:In recent years, the study of polymer materials has become the research focus of scholars at home and abroad. Many researchers are devoted to the development of new material formulations, the improvement of existing materials, hoping to synthesize natural, excellent properties of biomimetic materials. Therefore, based on the extensive application of SU-8 photoresist in the field of MEMS, the mechanical, thermodynamic and damping properties of SU-8 adhesive and composites were studied by means of molecular dynamics. Not only can the prediction of macro-properties of materials be realized, but also the mechanism of macro-phenomena of materials can be understood and analyzed from the microcosmic point of view. Firstly, combining the basic theories of molecular mechanics and molecular dynamics, this paper analyzes the force field, ensemble and boundary conditions of molecular dynamics suitable for the study of polymer materials, and puts forward the molecular polymerization based on COMPASS molecular force field. Energy minimization and annealing simulation are used to construct non-crosslinked and cross-linked SU-8 photoresist models. The mechanical properties of SU-8 adhesive at room temperature, such as Young's modulus and Poisson's ratio, were calculated. The simulation results were compared with the experimental results to prove the feasibility of establishing the material model and the validity of the molecular dynamics algorithm. Secondly, the composite model of SU- 8 rubber and different types of CNTs was established, and the effects of different types of CNTs on the mechanical properties of the composites were studied by molecular dynamics. The results show that carbon nanotubes can greatly improve the mechanical properties of the materials. As the diameter of CNTs increases, Young's modulus of composites decreases gradually, and it is proved that compared with single-walled CNTs, double-walled CNTs can significantly improve the mechanical properties of the composites. Thirdly, the glass transition behavior of SU-8 adhesive and its main influencing factors were studied by molecular dynamics simulation. The glass transition temperatures of non-crosslinked and crosslinked SU-8 adhesive were predicted to be 326.7K and 494.8K, respectively. The effect of force field energy term on glass transition temperature is discussed emphatically. It is found that the change of non-bond energy is the main factor affecting glass transition, which is helpful to understand the essence of glass transition process and to study the micro-mechanism of damping properties of materials. At the same time, the glass transition temperature of SU-8 adhesive with different process parameters was obtained by dynamic mechanical analysis (DMA). Finally, the hydrogen bond, radial distribution function, free volume fraction and binding energy of SU-8 glue and composites are calculated. The bonding strength between CNTs and SU- 8 adhesive was obtained by calculating the interfacial bonding energy of the composites, and the intermolecular and intra-molecular interaction modes were obtained by calculating the hydrogen bond and radial distribution function of the SU-8 adhesive. Based on the calculation of free volume of composites and the influence of free volume on glass transition, the effects of free volume and hydrogen bond on damping properties of composites are discussed, which provides a reference for the design of polymer-based damping composites.
【学位授予单位】：大连理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ317;TB33
[Abstract]:In recent years, the study of polymer materials has become the research focus of scholars at home and abroad. Many researchers are devoted to the development of new material formulations, the improvement of existing materials, hoping to synthesize natural, excellent properties of biomimetic materials. Therefore, based on the extensive application of SU-8 photoresist in the field of MEMS, the mechanical, thermodynamic and damping properties of SU-8 adhesive and composites were studied by means of molecular dynamics. Not only can the prediction of macro-properties of materials be realized, but also the mechanism of macro-phenomena of materials can be understood and analyzed from the microcosmic point of view. Firstly, combining the basic theories of molecular mechanics and molecular dynamics, this paper analyzes the force field, ensemble and boundary conditions of molecular dynamics suitable for the study of polymer materials, and puts forward the molecular polymerization based on COMPASS molecular force field. Energy minimization and annealing simulation are used to construct non-crosslinked and cross-linked SU-8 photoresist models. The mechanical properties of SU-8 adhesive at room temperature, such as Young's modulus and Poisson's ratio, were calculated. The simulation results were compared with the experimental results to prove the feasibility of establishing the material model and the validity of the molecular dynamics algorithm. Secondly, the composite model of SU- 8 rubber and different types of CNTs was established, and the effects of different types of CNTs on the mechanical properties of the composites were studied by molecular dynamics. The results show that carbon nanotubes can greatly improve the mechanical properties of the materials. As the diameter of CNTs increases, Young's modulus of composites decreases gradually, and it is proved that compared with single-walled CNTs, double-walled CNTs can significantly improve the mechanical properties of the composites. Thirdly, the glass transition behavior of SU-8 adhesive and its main influencing factors were studied by molecular dynamics simulation. The glass transition temperatures of non-crosslinked and crosslinked SU-8 adhesive were predicted to be 326.7K and 494.8K, respectively. The effect of force field energy term on glass transition temperature is discussed emphatically. It is found that the change of non-bond energy is the main factor affecting glass transition, which is helpful to understand the essence of glass transition process and to study the micro-mechanism of damping properties of materials. At the same time, the glass transition temperature of SU-8 adhesive with different process parameters was obtained by dynamic mechanical analysis (DMA). Finally, the hydrogen bond, radial distribution function, free volume fraction and binding energy of SU-8 glue and composites are calculated. The bonding strength between CNTs and SU- 8 adhesive was obtained by calculating the interfacial bonding energy of the composites, and the intermolecular and intra-molecular interaction modes were obtained by calculating the hydrogen bond and radial distribution function of the SU-8 adhesive. Based on the calculation of free volume of composites and the influence of free volume on glass transition, the effects of free volume and hydrogen bond on damping properties of composites are discussed, which provides a reference for the design of polymer-based damping composites.
【学位授予单位】：大连理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ317;TB33
【共引文献】
相关期刊论文 前10条
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4 陈，
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