RIA: Mechanisms of High Temperature Subcritical Crack Growthin Ceramic-Matrix Composites

陶瓷材料耐高温和恶劣环境的能力为化学加工、发电和工业废物回收应用中高温部件的设计性能的潜在重大改进提供了巨大的前景。然而，它们作为结构材料的使用受到限制，主要是因为它们的断裂韧性差，缺乏损伤容限。虽然过去的研究在陶瓷的低温增韧，特别是第二相增强方面取得了重大进展，但这些低温增韧机制中的大多数在高温下失效。本研究将研究三类陶瓷基复合材料高温亚临界裂纹扩展的基本微观机制，以反映不同的主要室温增韧机制，即裂纹偏转、裂纹捕获和裂纹桥接。方法将是1)在半导体陶瓷中开发一种可行的高温裂纹生长监测技术，ii)确定阻碍这些复合材料在高温下裂纹发展的显著机制，iii)根据裂纹与复合材料成分之间的相互作用来检查这些机制的微观结构起源。Iv)记录这些机制的增韧作为微观结构参数的函数，以及v)建立描述增韧机制对微观结构依赖的物理模型。

The ability of ceramic materials to withstand high temperature and hostile environments offers great prospect for potential major improvements in the design performance of high temperature components in chemical processing, power generation and industrial waste recovery applications. Their use as structural materials, however, has been limited primarily because of their poor fracture toughness and lack of damage tolerance. Although research in the past has resulted in major advances in the low temperature toughening of ceramics especially be second phase reinforcements, the majority of these low temperature toughening mechanisms become ineffective at high temperatures. In this research the fundamental micromechanisms of high temperature subcritical crack growth in three classes of ceramic-matrix composites, chosen to reflect different primary room temperature toughening mechanisms, namely crack deflection, crack trapping and crack bridging, will be examined. The approach will be 1) to develop a viable high temperature crack growth monitoring technique in semiconducting ceramics, ii) to identify salient mechanisms impeding crack advances in these composites at high temperatures, iii) to examine the microstructural origins of these mechanisms in terms of the interaction between the crack and the constituents of the composite, iv) to document the toughening from these mechanisms as a function of the microstructural parameters, and v) to establish physical models describing the microstructural dependence of the toughening mechanism.