【作者】 杨伟；

【导师】 杜善义； 梁军；

【作者基本信息】 哈尔滨工业大学 ， 工程力学， 2006， 硕士

【摘要】 碳基复合材料广泛应用于航空航天等领域。作为一种先进的工程材料,碳基复合材料的性能很大程度上依赖于制备工艺。其制备工艺的核心又是致密化处理工艺,该工艺的周期长、成本高、工艺温度苛刻、工艺反应十分复杂。因此,对碳基复合材料的致密化工艺的研究一直以来都是碳基复合材料研制和应用的关键。本文建立了数学模型描述碳基复合材料“液相浸渍致密化工艺”过程,进而建立“工艺-微结构-材料性能”之间的关系以促进复合材料的设计、工艺与性能优化的一体化。本文把工艺过程中的碳基复合材料看作由增强纤维、液相浸渍剂、基体固化产物、碳化产物、石墨化产物和气体组分材料构成的六相系统,基于系统内物、化反应机理和阿伦尼乌斯方程,建立了该系统的热、质传递方程组描述各组分相间的相变反应,建立了修正的热传导方程描述工艺过程中复合材料内部的温度场。利用差分法求解了热、质传递微分方程组,数值模拟了各组分材料体积含量在整个制备工艺过程中的变化规律。通过沥青碳收率实验值与本文模拟结果和C/C复合材料石墨化度实验值与本文模拟结果的对比,得到的误差分布合理,分别验证了本文工艺模拟模型对致密化处理工艺和高温热处理工艺模拟的合理性和有效性。基于渐进均匀化思想,建立了基体的多层立方体壳单胞模型,推导出了含多相组分材料的基体体平均的等效弹性性能和强度解析式。基于多尺度方法计算了多层立方体壳单胞模型的弹性性能。理论与数值结果吻合较好。利用对C/C复合材料制备工艺模拟的结果,给出了C/C复合材料基体在工艺过程中弹性性能和强度的变化规律。进而,研究了增强纤维束中单根纤维丝的缺陷和弯曲对增强纤维束力学性能的影响。在此基础上,本文又考虑了编织复合材料增强纤维束的弯曲因素,预报了单向纤维束增强复合材料的力学性能。最后,基于上述综合结果,本文研究了编织复合材料在整个工艺过程中的弹性模量与强度的变化规律。初步建立了碳基复合材料“工艺-微结构-材料性能”之间的关系。更多还原

【Abstract】 Carbon-carbon composites are widely applied in the area of astronautics and aeronautics. As a kind of advanced composites, its properties are known to depend essentially on the technological regimes of its manufacturing processes. This present dissertation is devoted to the modeling of manufacturing processes of the composites and focuses on establishing the processing-microstructure-property relation to enable design of internal architecture to predict and optimize properties.Based on rational assumption, the C/C composite material is considered as a six-phase system (including carbon fiber phase, liquid pitch phase, solid pitch phase, solid residue phase of pyrolysis of the pitch matrix, gas phase and graphitized carbon phase of matrices) during all manufacturing processes. In view of the mechanism of chemical reactions and the Arrhenius law, phase transformations in a C/C composite under manufacturing processes are described by a group of non-linear differential equations of heat mass transfer and the temperature field within the composite material is characterized by the developed heat conduction equation. This dissertation provides the changes of volume concentrations of six components of the materials that occur during the technological cycles of manufacturing. With the comparison of our results and experiment data, it is showed that this paper’s modeling of manufacturing processes of C/C composites is reasonable and effective, and the precision is satisfied.With the concept of the asymptotic averaging theory, this paper shows the cubic model considering the periodic cell of matrix as hollow cubes with a cube of fluids inside and hollow cubes of other solid phases outside. Then we provides formulae of effective elastic properties and strength of the matrix with multi-phases. After comparing results from the cubic model with those via FEPG software based on multi-scale method, it is found that the present model of matrix is reasonable and effective. With the help of the numerical simulation of manufacturing processes of C/C composites, we makes the prediction of changes in mechanical properties of the matrix (such as elastic moduli, strength,更多还原