平流层飞艇蒙皮材料I型裂纹研究

 飞艇在平流层环境中受高低温交变、臭氧、紫外辐射等恶劣工况的影响。为研究平流层飞艇蒙皮材料I 型裂纹特性，在单轴向拉伸载荷下，分析了含有初始裂纹的蒙皮材料撕裂裂纹尖端区域变形场的测试方法和裂纹扩展特征。通过初始长度均为20 mm 的单边切口人工模拟预制裂纹试样，采用数字散斑相关方法试验，分别获得I 型裂纹尖端和垂直裂纹尖端的位移场和应变场分布，结合散斑变形图进行相关计算，发现撕裂裂纹扩展过程为近似的脆性断裂特征，垂直于撕裂裂纹扩展方向的材料试样裂纹尖端变形场呈现为离散阶跃变化特征。研究结果表明：该方法可以测量平流层飞艇蒙皮用的柔性层压织物的I 型裂纹尖端变形场，揭示裂纹尖端初始裂纹的扩展规律和演化特征，获得的大范围屈服裂尖长度的裂纹尖端的变形值曲线，可为平流层飞艇蒙皮材料的撕裂损伤变化分析和裂纹尖端变形场测试提供有效的方法。

Mode I Crack Tip Deformation Field for Stratopheric Airship Envelope

The stratospheric airship is affected by the alternating high and low temperatures, the ozone, the ultraviolet radiation and other harsh conditions in the stratosphere environment. This paper studies the crack tip opening displacement (CTOD) fields and the strain distribution test method for the strain field in the stratospheric airship envelope material by uni-axial tensile experiments and the digital speckle correlation method (DSCM). For tearing tests of single edge notched (SEN) specimens, the initial weft crack is prefabricated to a length of 20 mm, and the typical brittle fracture is observed during the crack propagation process and the material specimen deformation field varies in a manner of steps. The calculation results of the displacement and the strain of the weft and warp fibers show that the mode I crack tip deformation field is accurately evaluated by the DSCM, which also displays the initial crack propagation law and the crack evolution characteristics of an SEN crack tip. The crack tip deformation curves for a large scale yielding length is obtained for the design and the deformation test of the high performance stratospheric airship envelope material.