Notch sensitivity and brittleness in fracture testing of S2 columnar freshwater ice

Abstract

Two loading configurations (four-point-bend, three-point-bend) were used in the laboratory at Clarkson to test for the fracture toughness of carefully grown S2 columnar freshwater ice. For one specific crack orientation and one grain size, the crack length was varied ranging from very short to very deep. The crack length effects were studied in this way for three specimen sizes (the in-plane dimensions of the specimen size were geometrically scaled; the specimen thickness was essentially constant). These crack length and specimen size tests are primarily directed towards designing fracture toughness tests for ice that both satisfy small scale yielding requirements and provide material properties (in the sense of (1)) — toughness values independent of the size and geometry of the specimen. Considerations of sufficient notch sensitivity in terms of brittleness numbers provide a means to determine the necessary specimen size. The results reported in this paper suggest that the specimen sizes used in testing S2 ice to date have largely been sub-size.