Fracture Toughness of Silicon Carbide Evaluated Using Pre-cracked Specimens

Abstract

Silicon carbide plate specimens with through-thickness crack of which stress intensity can be calculated by the two-dimensional stress analysis, are prepared by a new method developed in the present work for conducting fracture toughness tests. The specimen geometry is quite similar to that of ASTM standard compact tension specimens. A compressive load is applied on the upper and lower surfaces of the specimen, with a narrow slit crack-starter to produce a tensile stress near the notch root and a compressive stress far from it. The loading points is changed by the required crack length. Then, the specimen is loaded by a 20μs bending moment at the notch root. The obtained fracture toughness value from the specimen is almost constant, in the range of the crack length between 0.4 and 0.7 in its ratio to the specimen width. It is also independent of the specimen thickness between 3.0 and 9.5 mm.