Units: Mpa m1/2
Fractures occur when a solid ceramic is broken into pieces as a result of stress. Failure occurs first by crack formation and then by crack propagation. Brittle fracture cracks propagate quickly and without associated increases in the stress, they occur perpendicular to the stress direction. Cracks can propagate along crystallographic planes or through them (depending on a variety of factors eg. structural defects, crystal impurities). Fracture Toughness is ability of material to resist fracture, resist crack extension when a crack is already present.
ASTM-C1421 Fracture Toughness