纳米陶瓷基复合材料有效热—力学性能的有限元分析

发布时间：2018-09-05 08:10

【摘要】：陶瓷材料有优良的综合力学性能,但脆性大是它的最大缺点,为了解决脆性问题,碳纳米管和纳米颗粒补强是陶瓷材料增韧强化的重要途径。本文拟利用热力学和多尺度连续介质力学理论,对碳纳米管、纳米颗粒及其双相混和增强陶瓷基复合材料的热力耦合性能展开分析和研究,分别讨论碳纳米管、纳米颗粒及其协同作用对陶瓷材料补强增韧效果的影响。首先,发展球状纳米颗粒随机生成和投放的技术,并扩展运用到随机碳纳米管情况,建立不同体积比的碳纳米管、纳米颗粒及其混合随机分布二维和三维有限元模型。考虑温度变化并结合热力学理论,分析陶瓷基复合材料的热膨胀系数和热残余应力等热力学性能,将结果与经典理论方法结果比较,证明所建模型的可靠性。基于上述随机生成和投放技术建立的模型,用多尺度渐近均质化法分析无损情况下碳纳米管增强陶瓷基复合材料和纳米颗粒增强陶瓷基复合材料的力学性质,分别讨论增强相体积比和弹性模量变化对复合材料有效力学性能的影响,并用经典的Mori-Tanaka理论验证均质化法的有效性。考虑含界面脱粘损伤的情况,利用同样方法分析碳纳米管增强陶瓷基复合材料的力学性质,讨论界面脱粘长度对复合材料有效力学性能的影响。随后,进一步分析陶瓷基复合材料降温冷却过程中的热力学性能。利用弹性力学方法推导出碳纳米管增强陶瓷复合材料特征体积单元的径向、切向和轴向热残余应力的理论计算方法,并和有限元结果进行对比,均能较好吻合;利用经典理论方法预测复合材料的有效热膨胀系数,对比验证所建模型的可靠性;分别讨论碳纳米管的热膨胀系数、弹性模量、体积分数、长径比和温度差等因素的变化对复合材料热残余应力和有效热膨胀系数等热力学性能的影响,为陶瓷基复合材料的设计提供一定的依据。最后,综合运用断裂力学和损伤力学理论,用ANSYS建立含界面损伤碳纳米管增强陶瓷基复合材料的内聚力模型。分析存在界面损伤时复合材料的界面损伤曲线和应力分布状况,分别讨论最大法向接触拉伸应力和裂纹最大张开位移对复合材料界面损伤过程的影响。
[Abstract]:Ceramic materials have excellent comprehensive mechanical properties, but the brittleness is its biggest disadvantage. In order to solve the problem of brittleness, carbon nanotubes and nanoparticles reinforcement is an important way to toughen and strengthen ceramic materials. The thermo-mechanical coupling properties of matrix composites are analyzed and studied. The effects of carbon nanotubes, nanoparticles and their synergistic effects on the toughening and reinforcing effect of ceramic materials are discussed. Two-dimensional and three-dimensional finite element models with random distribution of nanoparticles and their mixtures are developed. The thermal expansion coefficients and thermal residual stresses of ceramic matrix composites are analyzed by considering temperature variations and combining with thermodynamic theory. The results are compared with those of classical theory and method, and the reliability of the model is proved. The mechanical properties of carbon nanotube reinforced ceramic matrix composites and nano-particle reinforced ceramic matrix composites under nondestructive loading were analyzed by the multi-scale asymptotic homogenization method. The effects of volume ratio of reinforcing phase and elastic modulus on the effective mechanical properties of the composites were discussed respectively. The classical Mori-Tanaka theory was used to test the mechanical properties of the composites. Considering the interfacial debonding damage, the mechanical properties of carbon nanotube reinforced ceramic matrix composites are analyzed by the same method, and the effect of interfacial debonding length on the effective mechanical properties of the composites is discussed. The theoretical calculation methods of radial, tangential and axial thermal residual stresses of the characteristic volume units of carbon nanotube reinforced ceramic composites are derived by elastic mechanics method, and the results are in good agreement with those of finite element method. The effects of the thermal expansion coefficient, elastic modulus, volume fraction, aspect ratio and temperature difference of carbon nanotubes on the thermal residual stress and effective thermal expansion coefficient of the composites were discussed, which provided a basis for the design of ceramic matrix composites. In this paper, the cohesion model of carbon nanotube reinforced ceramic matrix composites with interfacial damage is established by ANSYS. The interfacial damage curve and stress distribution of the composites with interfacial damage are analyzed.
【学位授予单位】：华南理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB332

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