Flexing characteristics of three varieties of thermoplastic polyurethane (TPU) coated high strength fabrics (nylon 6,6, polyester and kevlar) have been evaluated by subjecting them to 5000 cycles in a De-Mattia flex tester. The flexing damage is assessed in terms of % loss of strength by evaluating the residual tensile strength of flexed fabrics. Statistical analysis has been carried out at 95% significance level for assessing the influence of flexing cycles and variation in thermoplastic polyurethane concentration on the residual strength of coated kevlar fabrics. Accordingly, the specific trend exhibited is established. The study shows that the coated kevlar fabric has suffered with maximum strength loss, while nylon and polyester show excellent flex damage resistance with negligible strength loss. Further, the sensitivity to damage of kevlar fabric has been studied by varying the number of flex cycles from 1000 to 5000 and the extent of damage that happened within the structure is thoroughly analyzed using field emission scanning electron microscope. Finally, the possible mean of improving strength retention (22%) of coated kevlar fabric subjected to repeated flexing by the application of a proprietary high viscosity polymer coating has been proposed.

中文翻译：

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高强度涂层织物的弯曲行为

通过在De-Mattia挠曲测试仪中对三种热塑性聚氨酯（TPU）涂层的高强度织物（尼龙6,6，聚酯和芳纶纤维）进行了5000次循环，对其挠曲特性进行了评估。通过评估挠曲织物的残余抗张强度，以％强度损失的形式评估挠曲损伤。已在95％的显着性水平上进行了统计分析，以评估弯曲周期和热塑性聚氨酯浓度变化对芳纶纤维涂层织物残留强度的影响。因此，确定了所显示的特定趋势。研究表明，涂覆的凯夫拉纤维织物遭受了最大的强度损失，而尼龙和聚酯则表现出优异的抗挠曲破坏性，而强度损失可忽略不计。进一步，通过将挠曲循环数从1000更改为5000，研究了凯夫拉纤维织物损坏的敏感性，并使用场发射扫描电子显微镜彻底分析了结构内发生的损坏程度。最后，已经提出了通过施加专有的高粘度聚合物涂料来改善经受反复弯曲的凯夫拉纤维织物的强度保持率（22％）的可能手段。