碳陶摩擦材料制动盘在热-机械耦合环境下的疲劳行为及损伤演变机理

Carbon fibre reinforced carbon and silicon carbide dual matrix composites (C/C-SiC) is a new generation of high performance brake materials after carbon/carbon composites. In comparison to the traditional brake materials, C/C–SiC brake composites exhibit low density, high thermal shock resistance, longer service life, especially lower sensibility to surroundings and temperature for a silicon carbide share of at least 20% in mass. With the modern transportation and power machinery become more speed and lower weight, The demand for reliability and safety of C/C-SiC become more and more urgent. But the fatigue behavior and thermal cracks are the key scientific problems that constrained the life and reliability of C/C-SiC. This project is based on the similarity theory, and with the methods of step simulation and successive approximation, combine with finite element analysis, non-destructive testing and bench testing, for investigating the damage evolving and failure mechanism of C/C-SiC brake composites based on the complicated thermo-mechanical coupling condition. The preform was prepared by needling method, and carbon matrix were prepared by chemical vapor infiltration, and finally made use of liquid silicon infiltration to prepare the silicon carbide and obtained the modified C/C-SiC composites. The properties base on only heat load and fatigue behavior of C/C-SiC under thermal cycling will be investigated, as well as the tribological properties and mechanism of subscale and full-size piece C/C-SiC brake discs at different brake conditions. The friction interface behavior and crack initiation and dynamic expansion will be proven. The theoretical model of composite crack initiation and dynamic expansion will be established, and failure mechanism and preventive measures will be obtained. The failure behavior and damage evolving mechanism of C/C-SiC based on the complicated thermo-mechanical coupling condition will be explored. We will optimal design and get a full-size C/C-SiC brake disc with optimum performance base on the above researches, which lay the theoretical and methodological basis for the further development and application of C/C-SiC brake discs.

碳陶摩擦材料是继碳/碳材料之后的新一代制动材料，是现代交通运输工具和动力机械向高速高能载发展的重要保障，疲劳行为及热裂是制约碳陶制动盘可靠运行和寿命提高的关键科学问题。本项目基于相似理论，采用仿真模拟和台架试验相结合的方法，构建适合不同制动工况的热-机械耦合场数学模型，探讨碳陶制动盘的疲劳行为和损伤演变机理。以碳纤维整体毡为预制体，分别采用化学气相渗透法和熔融渗硅法制备碳和碳化硅基体获得碳陶摩擦材料。研究碳陶摩擦材料在单一热负荷下的性能和热循环下的热疲劳行为；探明缩比件和全尺寸碳陶制动盘在不同工况下的摩擦性能变化规律和摩擦机理；阐述摩擦界面行为及材料裂纹萌生和动态扩展的规律；揭示碳陶摩擦材料制动盘在热-机械复杂耦合环境下的疲劳行为和损伤演变机理；并提出控制裂纹扩展的方法及预防措施。在此基础上优化设计并获得最佳性能的全尺寸碳陶制动盘，为进一步实现碳陶制动盘的开发及应用奠定理论和方法基础。

碳陶摩擦材料是继碳/碳材料之后的新一代制动材料，是现代交通运输工具和动力机械向高速高能载发展的重要保障，疲劳行为及热裂是制约碳陶制动盘可靠运行和寿命提高的关键科学问题。本项目采用仿真模拟和台架测试相结合的方法，构建了适合不同制动工况下的热-机械耦合场数学模型，探讨了碳陶制动盘的疲劳行为和损伤演变机理。碳陶材料预疲劳试样的残余拉伸强度（RTS）随疲劳应力的增大而呈现上升趋势，在58.2 MPa和69.3 MPa的疲劳应力下分别循环10万次后，预疲劳试样的RTS分别增加到85.8 MPa和92.5 MPa。探明了研究碳陶摩擦材料在不同制动参数和不同环境下的摩擦磨损特性，随着制动初速度的增大平均动摩擦系数减小，磨损率增大。摩擦界面第三体由磨屑及其氧化物混合压实而成，当其形成速度与破坏速度达到动态平衡，摩擦面形成光滑、致密的摩擦膜，有助于稳定摩擦系数、减少磨损量。.研究了碳陶摩擦材料在不同速度和不同压力下制动的温度场和压力场，制动速度越高或制动压力越大，温度升高的越快，摩擦面最高温度均出现在外径附近，且径向温度梯度小于轴向温度梯度；制动过程中热应力出现两次峰值，分别出现在摩擦面和试环固定端附近，且最大热应力出现在摩擦面中径附近。.揭示了基体裂纹萌生与扩展、界面脱粘与滑动、纤维性能衰退与纤维断裂、层间开裂等多种损伤模式可以以单独作用的方式或耦合作用的方式来影响材料的微观结构与力学性能。在疲劳加载过程中，当基体裂纹张开后，纤维在界面脱粘区域相对基体的滑移是产生疲劳迟滞现象的主要原因。.本项目揭示了碳陶摩擦材料制动盘在热-机械复杂耦合环境下的疲劳行为和损伤演变机理，形成了具有高可靠性的碳陶制动盘及其结构设计原型，为进一步实现碳陶制动盘的开发及应用奠定了理论和方法基础。