The effect of loading rate on fracture toughness of ice has been investigated using sharply edge-notched specimens by bending at -10°C. The loading rate K_I ranged from 1 to about 10³kPam^1/2/s. The notch was made by molding a razor blade in the specimen in the ice growing process and removing it before the bending test. Two sizes of specimens, section sized 25×25mm (small size specimen) and 50×50mm (medium size specimen) respectively, were used. About thirty small size specimens or about ten medium size specimens were tested at each loading rate. The experimental results were as follows.
(1) The values of K_Ic were lower in the higher K_I range, and there was a transition in the range of K_I=10-100kPam^1/2/s.
(2) The effect of K_I was found to be very small in the range of K_I larger than 100kPam^1/2/s.
(3) The effect of loading rate on the minimum value of fracture toughness K_Ic was small in the whole range of K_I tested for both small and medium size specimens.
(4) The minimum K_Ic values of small and medium size specimens seem to coinside each other approximately. The maximum and the median K_Ic values of medium size specimens were smaller than those of small size specimens.
(5) It was found that a vinyl silicone impression material being used for dentistry was suitable to make replica of the fracture surface for macrofractography.