Fracture of Functionally Graded Materials - Modeling, Synthesis and Experiments

9713798 Paulino根据该项目开发了可用于预测和优化FGM机械性能的物理模型。离散和连续的功能梯度材料分别使用边界积分方程和有限元方法进行了分析。通过数值模拟优化组成梯度为材料合成提供了相关的输入。 在合成过程中使用了一种称为场活化燃烧合成（FACS）的新技术。脆性FGM系统，MOSi 2/SiC，由两个层之间夹着一个成分梯度界面连接组成。 在不同的外加电场作用下，得到了不同的组成分布。 用电子探针分析了Mo和Si相浓度的空间分布。不同的样品，在梯度界面处的各种成分的配置文件，通过仔细地放置一个裂缝内的成分梯度。层进行测试。通过实验和数值模拟研究了裂纹面平行于和垂直于材料性能梯度的功能梯度材料的断裂行为。通过断裂力学实验对数值模型进行了标定。研究了在机械和/或热载荷作用下，组分分布函数对功能梯度材料的结构行为和裂纹萌生与扩展机理的影响。该研究有助于理解的机械行为和最佳（或接近最佳）的成分分布函数的MoSi，）/SiC和Ti 3SiC 2/SiC功能梯度材料，特别是，和FGMS的实际设计，一般。 ***

9713798 Paulino Physically based models which can be used to predict and optimize FGM mechanical performance are developed under this project. Discrete and continuous FGMs are analyzed using the boundary integral equations and the finite element methods, respectively. Optimization of the compositional gradient by means of numerical simulations provides relevant input for material synthesis. A novel technique known as Field- Activated Combustion Synthesis (FACS), is used in the synthesis process. Brittle FGM system, MOSi2/SiC, consisting of two layers joined by a compositionally graded interface sandwiched between the layers is used. With different applied electrical fields, different compositional profiles are obtained for this system. The spatial distribution of the phase concentrations of Mo and Si are determined from electron microprobe analysis. The distinct samples, with various compositional profiles at the graded interface, are tested by carefully placing a crack inside the compositionally graded.layer. The fracture behavior of FGMs with crack faces parallel and perpendicular to the property gradient are investigated both experimentally and numerically. The numerical models are calibrated by fracture mechanics experiments. The influence of compositional distribution functions on the structural behavior and the mechanics of crack initiation and propagation in FGMs under mechanical and/or thermal loads is studied. The study contributes to the understanding of mechanical behavior and optimal (or near optimal) compositional distribution functions of MoSi,)/SiC and Ti3SiC2/SiC FGMs, in particular, and to the actual design of FGMS, in general. ***