Effect of Microstructure on Fracture

Porosity has a major effect on the fracture of materials. There are two ways by which pores influence fracture strength  

Presence of porosity decreases the cross-sectional area on which the load is applied. 

A ductile phase in a multiphase ceramic is found to increase the fracture strength. An example to cite is the case of cemented carbide. This composite contains cobalt as the ductile phase. In this material, cracks tend to originate 

Microstructure of a triaxial whiteware composition. (From W. D. Kingery et al.. Introduction to Ceramics, 2nd Edn., John Wiley, 1976, pp. 783-812.) 

Dugdale, Yielding of steel sheets containing slits, /. Mech. Phys. Solids, 

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