Font Size: 

Toughening mechanism for ceramic-based nanocomposites will be presentedbased on residual stresses around second-phase nano-particles dispersed in matrix grains.The residual thermal stresses around a spherical particle within a concentric sphere of amatrix grain were analyzed to clarify the effects of residual stresses on the tougheningmechanism in the frontal process zone. An indirect estimation technique for assessing acritical size of the frontal process zone in ceramics was also proposed using a SEVNB(Single-Edge V-Notched Beam) technique. A three-point flexure test was carried out fornanocomposites and monolithic materials with various depths of a sharp V-shaped notch,and then a critical local stress was calculated at a distance from the notch tip. The frontalprocess zone size at the beginning of crack propagation, namely, the critical frontal processzone size, was determined as the distance from the notch tip to the point where the localstress has the same value as the flexural strength of the material. The results revealed thatboth the strength and the critical frontal process zone size must be increased forenhancement of the fracture toughness of ceramics.