Sandwiched-beam procedure for precracking brittle materials

A technique for precracking brittle materials is presented. This procedure, which is called the sandwiched-beam (SB) technique, allows the production of sharp through-thickness cracks with predetermined length in specimens wi th a rectangular section, A bar, in which an initial notch is produced by u sing a conventional saw, is inserted between two supporting beams and the s andwich assembly is loaded in three-point bending, Conditions can be define d that allow the stable propagation of a sharp flaw from the notch as the a pplied load is increased. Then, the cracked bar can be used to determine th e fracture toughness. The SB technique is applied to different brittle mate rials, including soda-lime-silica glass, alumina, Si3N4, a SiCw-Si3N4 compo site, graphite, a Ti-Al intermetallic, and Carrara marble.