Study On Quasi-static And Dynamic Compressive Mechanical Properties Of Cotton Fiber Ice

China is one of the countries where hail disasters frequently occur,and hail can cause great harm to basic buildings such as houses.Violent hail can damage roofs and walls,causing buildings to be damaged or collapse.In order to reduce the losses caused by hail disasters,it is necessary to carry out structural anti-hail design in the field of engineering.Since the mechanical properties of hail itself will significantly affect its impact damage mode,and thus affect the degree of structural damage.The compressive strength of hail is the main factor affecting the impact response of hail.Therefore,experimental research on the compressive mechanical properties of hail itself is the basis for structural anti-hail design.In experiments,artificially prepared hail is usually used to replace natural hail for testing.According to the American ASTM＿320-21 standard test for aerospace shell anti-hail performance,cotton fibers are added to water and frozen to simulate natural hail.On this basis,this paper first designed and prepared 5 kinds of cotton-containing ice specimens with cotton mass fractions of 0%,3%,6%,9%,and 12%,respectively,to simulate hail with different densities and toughness.And in order to prevent the influence of environmental temperature on the test results,corresponding insulation measures were added during the test process,and the operation process of the test was optimized.Then using a universal testing machine and a Hopkinson pressure bar device,quasi-static and dynamic compression tests were carried out respectively to explore the influence rules and damage modes of temperature and strain rate on the compressive strength of ice specimens with different cotton content.The main conclusions are as follows:(1)Freezing temperature will significantly affect the compressive strength of cotton-containing ice.In both quasi-static and dynamic tests,its compressive strength increases as the temperature decreases.Among them,the specimen with a cotton content of0% is most affected by temperature.As the cotton content increases,the influence of temperature on specimen strength will gradually decrease.(2)Cotton-containing ice has obvious strain sensitivity,and its strength under dynamic compression is greater than that under quasi-static compression.Under quasi-static compression,the compressive strength of specimens with a cotton content of 0% decreases as the strain rate increases.However,in dynamic compression,its compressive strength increases as the strain rate increases;specimens with a cotton content of 3% or more have an increase in compressive strength as the strain rate increases in both quasi-static compression and dynamic compression tests.(3)The addition of cotton fiber can enhance the deformation resistance of ice specimens.In quasi-static compression,0% and 3% cotton content specimens have small displacement at the final damage,which takes the form of splitting damage.However,6% and above cotton content specimens exhibit plastic damage,and maintain some load bearing capacity.In the dynamic compression experiments,the higher the cotton content,the greater the strain corresponding to the peak stress and the lower the strain rate at a given impact velocity.Therefore,0% and 3% cotton content specimens show a "double-peak" shape of stress-strain curve at lower impact velocities,which changes to a "single-peak" shape as the impact velocity increases.In contrast,when the impact speed increases,the stress-strain curve changes to a "single-peak" shape regardless of the cotton content.When the cotton content is constant,the damage form of the specimen is related to the strain rate.