多维力载荷下陶瓷基复合材料的力学性能及失效机理研究

Ceramic matrix composites (CMCs) are ideal materials to replace superalloys to manufacture the parts that work in the hot section of aero engines. Until now, the research on mechanical behavior and failure of the CMC under complex stress states is still inadequate. This project aims at studying the mechanical property and failure mechanism of the CMC under multi-axis loads; this could supplement the theoretical support for lightweight design. The nonlinear constitutive model of the CMC under tension-bending-torsion combined loads could be derived by the bridging model of the micromechanics, which could explain the mechanic behavior of the CMC. A multi-axis loading material testing machine will be proposed based on a hybrid mechanism to exert multi-axis loads to the CMC specimens. This could simulate the complex loading condition of the CMC parts and benefit accurately measuring the mechanical property of the CMC. The experimental data could be utilized to identify the parameters in the constitutive model and prove its accuracy. The micro morphology of the failed specimens will be observed to deduce the failure model; and how the mechanical properties of the fiber, matrix and interface affect the failure behavior of the CMC will be also analyzed. These will help to discover the failure mechanism of the CMC under complex stress states. Through the aforementioned studies, a new multi-axis loading method for testing the CMC is expected to be generated, and a new approach will be discovered to analyze the mechanical property and failure mechanism of the CMC under complex stress states...The research findings of this project will enrich the mechanical and failure theories for analyzing the composites, and motivate the innovations in applying the CMCs in the hot section of aero engines.

陶瓷基复合材料(CMC)是一种可替代高温合金用于制造航空发动机热端部件的理想材料。目前关于复杂应力下CMC的力学行为和失效研究仍不充分，本申请拟研究多维力载荷下CMC的力学性能和失效机理，为轻量化设计提供更多理论支撑。基于细观力学建立CMC在拉力-弯矩-扭矩多维力载荷下的非线性本构模型，解析表达其力学行为。研制混联式多维力加载试验机，对CMC试件施加多维力载荷以模拟真实的复杂受力环境，更准确地测试其力学性能，实验数据可用于参数辨识和模型验证。观测断口微观形貌，推断失效形式，分析纤维、基体和界面的力学性能对宏观失效的影响规律，探索多维力载荷下CMC的失效机理。通过本项目的研究，构建用于CMC的多维力加载实验新方法，结合细观力学探索复杂应力下CMC力学性能和失效分析的新思路。..项目研究成果对丰富和完善复合材料力学和失效分析理论，指导CMC在航空发动机热端的创新应用具有积极意义。

陶瓷基复合材料较高温合金更耐高温且密度较低，是制造航空发动机热端部件的理想材料之一。由于航空发动机叶片在工作时通常需承受拉力-弯矩-扭矩复合的多维力载荷，掌握材料在实际载荷环境下的力学性能和失效机理是保障结构安全服役和轻量化的关键手段。目前，关于复杂应力下复合材料力学行为和失效研究仍有诸多问题亟待解决且缺少复杂载荷模拟方法。本项目基于桥联模型建立纤维增强复合材料的细观力学模型，考虑了材料在承受复杂载荷时的应力集中问题，引入应力集中指标，可更为准确地预测单向纤维复合材料的多向抗拉极限应力，横向抗拉极限预测误差降低40倍。基于6-UPS并联机构研制多维力加载材料试验机，实现了50kN轴向力、10kN侧向力、1kNm弯矩和2kNm扭矩的多维力复合加载，同时引入串联扭矩加载轴构建混联机构，解除机构固有约束实现多周扭矩加载，完成试验机理论分析和样机制造，研制具备应力感知与调节能力的智能工装夹具，建立复合材料多维力加载通用材料实验平台。研究多维力加载试验机的误差建模、测量与标定技术，补偿制造装配引入的系统误差，最大平移和姿态误差分别达到0.02mm和0.021°，有效提升试验机加载精度。研究了材料应力的非接触测量技术，分析了不同制备工艺下金属材料残余应力随深度的分布规律。开展多种金属和复合材料的多维力加载材料试验，发现了多维力载荷对金属屈服过程的影响，以及多维力构成和加载序列对钛合金和复合材料失效行为的不同改变。使用扫描电子显微镜观测单向复合材料板断口的微观形貌，发现横向失效主要以基体裂纹萌生和扩展为主，裂纹首先沿纤维方向在基体中产生，纤维受损较少，而应力集中进一步降低了基体强度，失效行为与细观力学模型分析结果基本一致。本项目的成果丰富了复合材料细观力学和失效分析的理论体系，构建了模拟复杂服役载荷的多维力加载实验新方法，为航空发动机叶片等关键部件的精准轻量化提供更准确的数据参考和理论支撑。