Wenjin Luo

Date of Award

2007

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science in Mechanical Engineering (MSME)

Department

Mechanical Engineering

Advisor

Zhihe Jin

Second Committee Member

Michael Peterson

Third Committee Member

Donald A. Grant

Abstract

This thesis uses a thermal fracture mechanics model to study the thermal shock fracture behavior of functionally graded ceramics (FGC). The specimen used in this study is a FGC strip with an edge crack on one surface. A severe thermal shock is applied on the cracked surface. The temperature field in a thermally shocked FGC strip is evaluated first using a closed form solution. Thermal stresses, thermal stress intensity factors (TSIF) and critical thermal shocks are evaluated using a thermomechanics and fracture mechanics approach. The effective thermal properties of the FGC specimens are estimated using micromechanics models for conventional composites. Some numerical results of critical thermal shocks are provided for FGC specimens with constant elastic material properties and graded thermal properties in the thickness direction of the strips. Also, examples of thermal stresses and thermal stress intensity factors (TSIFs) are provided. The results show that the components gradation of the FGC composites has significant influence on the specimens' thermal shock behavior. When the volume fraction of the FGC strip is changed rapidly, the critical thermal shock is changed dramatically.

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