ORIENTATION EFFECTS ON THE FRACTURE OF POND (S1) ICE

The influence of structural anisotropy on the fracture toughness of S1 type freshwater ice was investigated by fabricating and testing three different fracture geometries from a single ice core. The ice was tes ted at -16 degrees C using the Chevron Edge Notch Round Bar in Bending (CENRBB), a Chevron Notched Tension (CNT) specimen and the Semi-Circu lar Bend (SCB) specimen. By this procedure, a complete anisotropic app arent fracture toughness (K-Q) characterization is possible from one c ore. The specimens can be prepared with very little machining. This ap proach is therefore suitable for both field and, as in this work, labo ratory studies. Three models are presented for computation of the stre ss-intensity-factor expressions for these specimens. There is a wide s catter in the K-Q results and the apparent fracture toughness was high er for cracks perpendicular, than for cracks parallel, to the c-axis a nd the columnar grains. Possible explanations for this ambiguous behav ior are discussed in terms of the microstructural influences and speci men size effects.