PRODUCTION OF SHARP CRACKS IN CERAMIC MATERIALS BY 3-POINT BENDING OFSANDWICHED SPECIMENS

An easy procedure for precracking ceramic specimens is proposed in thi s paper. The method is based on the three-point bending of a sandwich formed by a ceramic beam inserted between two steel beams. Theoretical features of this procedure are analyzed on the basis of beam theory a nd fracture mechanics arguments. Crack length can be controlled by the initial saw cut length and by the relative stiffnesses of the ceramic and metal beams. This precracking procedure was applied to two differ ent alumina ceramics. Straight-through sharp cracks with controlled le ngth were proved to be easily introduced and the obtained crack length s were in good agreement with theoretical predictions. (C) 1998 Elsevi er Science Ltd. All rights reserved.