Compressive Mechanical Property of Artificial Hail Under Intermediate Strain Rates

Hail in nature is stronger than pure ice, and cotton fibers are usually added to imitate the mechanical properties of hail in nature. In this paper, distilled water and absorbent cotton were used to prepare different types of ice. The compression tests of pure water ice, ice containing cotton particles fiber, and ice containing long cotton fibers at strain rates of 0.2 s−1, 2 s−1 and 20 s−1 were carried out by using a high-speed hydraulic servo material testing machine, and the influences of cotton fiber distribution mode and content on the mechanical properties of ice were studied. To reduce the effects of data discreteness bias, multiple repeatability tests were conducted, and statistical parameters were regarded as the test results under each strain rate condition. The results showed that at the strain rate of 0.2 s−1, the stress peaks of ices containing 1.2% and 4.8% cotton particles and ices containing 1.2% and 4.8% long cotton fibers were 3, 5.5, 3.9 and 8.7 times of the pure water ice, respectively. The addition of cotton fiber changed the failure mode of pure water ice, which significantly improved the stiffness and breaking strength of ice, and the adhesion of long cotton fibers was stronger than that of cotton particles fiber, so its break strength and toughness were higher. As the strain rate increased, all types of ices presented more apparent brittle characteristics. Pure water ice and ice containing 1.2% cotton particles fiber showed overall positive correlation with strain rate, while ice containing 4.8% cotton particles fiber, ice containing 1.2% and 4.8% long cotton fibers showed a negative correlation with strain rate. The breaking capacity of ice containing less cotton particles fibers increased with the increasing of the loading speed, and the required external force work increased. Therefore, the compressive strength increased with the increase of strain rate. However, when the cotton particles fiber content was higher, or long cotton fibers was mixed with the ice as a whole, the cotton fiber to some extent prevented the mobility of ice, and the break strength decreased with the increase of strain rate within the range of intermediate strain rates, which was only limited to a specific strain rate range behaving the same failure mode.