ASTM C 1421 (C-1421) determines the fracture toughness, KIc, determination of advanced ceramics at ambient temperature. Fracture toughness is a measure of the resistance to crack extension in a brittle material. The methods determine KIpb (precracked beam test specimen), KIsc (surface crack in flexure), and KIvb (chevron-notched beam test specimen). The fracture toughness values are determined using beam test specimens with a sharp crack. The crack is either a straight-through crack formed via bridge flexure (pb), or a semi-elliptical surface crack formed via Knoop indentation (sc), or it is formed and propagated in a chevron notch (vb). This test method may be used in quality assessment, characterization, comparison, and research and development. TestResources provides machines, grips, equipment, and fixtures for testing in accordance with ASTM C1421.