Effect of Notch-Root Radius on the Fracture Toughness of Composite Si<SUB>3</SUB>N<SUB>4</SUB> Ceramics

Abstract

In-situ silicon nitride and a whisker-reinforced silicon nitride-silicon nitride composite, densified via gas pressure sintering and hot pressing, respectively, were evaluated using the single-edge V-notched beam (SEVNB) fracture toughness technique. The mean value ofK IC for each material was 5.7 and 7.9 MPa·m1/2, respectively, and the toughness was influenced by the presence of the elongated Si3N4 grains in the microstructure. The notch radius was observed to have the same effect as a sharp crack when notch-root radius was smaller than 10 µm, which was considered to be a realK IC for these materials.