人工制备冰雹的力学性能试验研究

人工制备的冰雹可用于多种航空附件冰撞测试。本文以ASTM F320—2010标准为基础，设计制作了多种冰雹，对冰雹的力学性能及影响冰雹力学性能的因素开展了研究。采用低温万能试验机对冰雹进行准静态试验，使用高速摄影技术深入分析冰雹破碎过程及特征，对比分析不同棉纤维种类、棉纤维特性和棉纤维含量下冰雹的力学性能。研究结果表明，含棉冰雹失效过程可分为3个阶段：线性增长阶段、屈服阶段和破碎阶段，失效过程中最大抗压强度出现在线性增长阶段末端。棉纤维的强度和弹性越好，冰雹破碎所需的加载力越大；棉纤维上附着的冰量越少，冰雹破碎所需的加载力越小。棉纤维含量增加可以加强棉纤维的连接作用，使含棉冰雹强度增加；但棉纤维含量到达15%时，继续增加棉纤维含量，冰雹抗压强度不会发生太大变化。亲水棉制成的冰雹抗压强度明显高于疏水棉制成的冰雹。研究结果可为中国民用大飞机适航符合性验证提供参考。

Experimental study on mechanical properties of artificial hail

The artificial hail can be used for ice collision test of various aviation accessories. Based on the ASTM F320—2010 standard, a variety of hailstones were designed and produced in this study. The mechanical properties of hailstones and the factors were investigated. A low-temperature universal testing machine was used to conduct quasi-static tests on hail. High-speed photography technology was adopted to analyze the hail crushing process and characteristics. The mechanical properties of hail under different cotton fiber types, cotton fiber characteristics, and cotton fiber content were analyzed. The results show that the cotton hail failure process can be divided into three stages: linear growth stage, yield stage, and crushing stage, with the maximum compressive strength during the failure process occurring at the end of the linear growth stage. The better the strength and elasticity of the cotton fiber, the larger the loading force required for hail breaking; the less the amount of ice attached to the cotton fiber, the smaller the loading force required for hail breaking. Increased cotton content can strengthen the connection of cotton fibers and increase the strength of cotton-containing hail; however, the hail compressive strength will not change much when the cotton content is larger than 15%. The compressive strength of hail made of hydrophilic cotton is significantly higher than that of hail containing hydrophobic cotton. The results of the study can provide reference for the verification of airworthiness compliance of civil aircraft in China.