We first analyze thermal stresses and thermal cracking in a strip of a functionally graded material (FGM) subjected to sudden cooling. It is assumen that the shear modulus of the material decreases hyperbolically with the higher value occurring at the surface exposed to the thermal shock and that thermal conductivity varies exponentially. It is shown that the maximum tensile thermal stress induced in the strip is substantially reduced by the presumed thermal conductivity gradient. Thermal stress intensity factors (TSIFs) are also calculated for an edge crack at the surface exposed to the thermal shock and results show that while the TSIF is relatively insensitive to the shear modulus gradient, it is significantly reduced by the thermal conductivity gradient. The crack growth resistance curve of a ceramic-metal FGM is also studied and it is found that the FGM exhibits strong R-curve behavior when a crack grows from the ceramic-rich region into the metalrich region. Finally, the thermal shock resistance of FGMs is discussed.
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