基于声发射的C/SiC陶瓷基复合材料高温损伤机制研究

As the physical information dissipated from the internal change of materials, acoustic emission (AE) provides a direct method to describe the failure mechanism of engineering materials. Especially for C/SiC composite materials, which are mainly used at elevated temperature exceeding 1000 centigrade℃, AE is nearly the only choice to realize the on-line damage monitoring and characterization and provides an experimental foundation to study the damage mechanism of C/SiC at elevated temperature. Unfortunately, due to the complex coupling effect among thermal, stress and chemical process, the failure process of C/SiC composites involves complex evolution of several microscopic fracture mechanism, which leads to significant complexity and variety of AE signals. This brings great challenge to the on-line damage monitoring and characterization utilizing AE technique. It is necessary to establish the mapping relation between the AE signal and the internal damage, through the detail investigation of the AE generation mechanism and parameter features of various damage modes, as well as AE pattern recognition methods..In this project, the elevated temperature damage characterization method based on AE technique will be investigated, by utilizing damage mechanics, elastic wave theory, signal processing theory, etc. The research will be emphasized on the following topics: (1) establishing the AE parameter spectrum of typical damage modes. (2) presenting an exact description on the damage mechanism and damage evolution of C/SiC composites under elevated temperature, on the basis of establishing the AE signal processing and pattern recognition methods. (3) investigating the influence of manufacturing flaws on the performance under elevated temperature, by establishing the stochastic correlation model among distribution of manufacturing flaws, AE parameters and service life. The scientific works will provide a theoretical foundation for describing the damage process and establishing the theoretical framework of damage characterization and life prediction of C/SiC composites at elevated temperature.

由于陶瓷基复合材料在高温服役条件下存在热、力以及化学过程的耦合作用，呈现多种微观断裂机制的复杂演化过程，给其损伤表征和寿命预测带来巨大的挑战。项目面向C/SiC陶瓷基复合材料，基于材料高温损伤过程的在线声发射监测，利用损伤力学、弹性波、信号处理与模式识别等理论，重点开展以下研究工作：（1）典型高温损伤模式声发射机制的分析与建模，构建声发射特征参数图谱；（2）建立有监督和无监督相结合的材料高温损伤声发射模式识别方法，确立声发射与材料损伤之间的映射关系，揭示材料高温损伤机制及演化规律；（3）建立制备缺陷、声发射与服役寿命的随机关联模型，研究制备缺陷对高温服役性能的影响。项目将为揭示C/SiC复合材料的高温损伤机理，预测C/SiC复合材料的高温服役性能，构建材料高温损伤表征理论与方法体系奠定理论基础，推动寿命预测、在线监测和服役安全评价技术的发展。

声发射是材料内部变化释放出来的物理信息，并且声发射信号特征和断裂机制有关，因此声发射技术为材料损伤的在线监测和表征提供了有效的手段。但由于陶瓷基复合材料在高温服役条件下存在热、力以及化学过程的耦合作用，呈现多种微观断裂机制的复杂演化过程，给其损伤表征和寿命预测带来巨大的挑战。本项目以连续碳纤维增韧碳化硅陶瓷基复合材料（C/SiC复合材料）为主要对象，通过高温环境下的材料损伤过程的声发射监测试验和典型损伤模式复现试验，结合损伤微观机制、声发射信号模式识别以及高温性能的协同分析，构建高温损伤过程声发射信号的模式识别方法，建立材料各种微观损伤机制与声发射信号的映射关系，研究C/SiC复合材料典型损伤模式的声发射特性及其演化过程，揭示高温损伤机制与服役寿命之间的关联关系，采用机器学习方法建立应力氧化剩余寿命预测模型，形成基于声发射的C/SiC复合材料高温损伤表征理论与方法体系，为揭示C/SiC复合材料高温损伤机理，描述C/SiC复合材料高温损伤演化过程，预测C/SiC复合材料的高温服役性能和使用寿命奠定了基础。研究成果已应用于航天飞行器热结构地面试验的损伤评估，推动了陶瓷基复合材料服役在线监测、寿命预测和服役安全评价技术的发展。