Fracture toughness, K IC, which measuresthe resistance tocrack propagation initiation of a pre-cracked body, is oneof the most importantpropertiesof ceramic materials. The main problemis to selectthe most appropriate methodto determinethis property,since there areseveral ones, each of them with its own characteristics. Normally, for convenience, the indentationmethod is chosen. It is the IF (Indentation Fracture) method, which measures the cracksizeat the verticesof the indentation. However, that methodhas many drawbacks, especially ifthe ceramic material isporous, since itisvery difficulttoidentify the extent of the propagated crack. Themost suitable methodformeasuring fracture toughnessis the SEVNB(Single Edge V NotchBeam). This paper describesK ICresultsfor threedifferent materials: silicon carbide, SiC, alumina, Al2O3, and a clay based ceramics, ceramic tile, with distinctporosities.The results indicate that thevalues of K ICare higherwhen theIF method is used, and the moreporous theceramicsis,the more difficult it is to applythis method. On the other hand, the SEVNB method, regardless porosity, can be applied successfully.The K ICvaluesmeasuredby the SEVNBmethodwere3.8 MPa.m½, 2.5 MPa.m½ and0.4 MPa.m½forSiC, Al2O3and ceramic tile, respectively.
ceramics; notch; fracture toughness; IF; SEVNB
