Thermal shock of layered ceramic structures with crack-deflecting interfaces

In this paper the influence of crack-deflecting interlayers on the thermal shock behavior of a ceramic body has been studied. It is observed that the presence of such interlayers inhibits the penetration of cracks into the bo dy and that the magnitude of this effect is much greater than that of inter nal stresses or of possible increases in fracture energy of the layers, bec ause cracking occurs in a manner different from that expected. A finite dif ference model has been used to estimate the temperature distribution in the body, from which the crack driving force and its variation with time and p enetration into the body have been calculated. It is shown that these obser vations are consistent with quantitative predictions, if continued crack gr owth in the laminate requires that the stress in the outermost intact layer is equal to the failure strength of that layer, rather than the crack driv ing force for the overall penetrating crack being equal to the fracture ene rgy of the material.