Uniaxial tensile central tearing behaviors of ethylene tetrafluoroethylene foils
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摘要: 针对乙烯-四氟乙烯(ETFE)薄膜结构膜面存在因初始缺陷、飞致物刺穿等引发膜材撕裂而导致结构承载力衰减和破坏的安全性问题，结合数字图像相关(DIC)技术对ETFE薄膜进行了系列单轴中心撕裂试验，深入分析了切缝长度、切缝角度和切口样式对薄膜撕裂力学行为的影响。结果表明：ETFE薄膜的典型撕裂过程呈现出4个特征状态；局部缺陷会显著影响薄膜的面外屈曲和破坏形态；典型撕裂抗力-位移曲线可分为撕裂前段、撕裂抗力上升阶段和撕裂后段3个阶段；薄膜的极限撕裂强度随切缝长度的增大而减小，随切缝角度的增大而增大；切口样式使薄膜在完全破坏时表现出类脆性或类延性破坏特征；“一”形切缝和直角边缘切口易引发应力集中，导致薄膜承载性能的显著衰减。所得结论可为ETFE薄膜的撕裂力学性能研究和ETFE膜结构的安全性评估提供有益参考。Abstract: Aiming at the safety of ethylene tetrafluoroethylene (ETFE) foil structural membrane surface, which is caused by initial defects and puncture of flying objects, leading to the attenuation of structural bearing capacity and damage, a series of uniaxial central tearing tests were carried out on ETFE foils combined with the digital image correlation (DIC) technology, and the effects of slit length, slit angle and notch shape on the tearing mechanical behaviors of the foils were analyzed in depth. The results show that the typical tearing propagation process of ETFE foils exhibits four characteristic states. Local defects can significantly affect the locations of the out-of-plane warping and the failure modes of the foils. The typical tearing strength-displacement curve can be divided into three characteristic phases: the pre-tearing phase, the tearing resistance rising phase, and the post-tearing phase. The ultimate tearing strength of the foils decreases with the increase of slit length and increases with the increase of slit angle. The notch shapes cause the foils to exhibit brittle-like or ductile-like damage characteristics upon complete damage. The “one” shaped slit and the right-angle edge notch tend to cause stress concentration, leading to significant degradation of the foil's load-bearing properties. The conclusions obtained can provide useful references for the study of the tearing mechanical properties of ETFE foils and the safety assessment of ETFE membrane structures.
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Key words:
- ETFE foils /
- central tearing /
- strength /
- failure mode /
- digital image correlation technology
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图 1 含中心切缝的乙烯-四氟乙烯(ETFE)薄膜典型试件示意图
Figure 1. Schematic diagram of a typical specimen of ethylene tetrafluoroethylene (ETFE) foils with a central slit
图 2 含中心切缝的ETFE薄膜加载过程中的夹持示意图
Figure 2. Clamping schematic of ETFE foils with a central slit during loading
图 3 切缝角度和切口样式的切缝示意图(单位：mm)
Figure 3. Slit diagram of slit angles and notch shapes (Unit: mm)
图 4 不同工况下ETFE薄膜典型撕裂过程：(a)切缝长度、(b)切缝角度和(c)切口样式
Figure 4. Typical tearing process of ETFE foils under different conditions: (a) Slit length; (b) Slit angle; (c) Notch shape
图 5 不同工况下ETFE薄膜切缝邻域的εxy应变云图
Figure 5. εxy strain nephogram of ETFE foils in the neighborhood of the slit under different conditions
图 6 不同切缝长度的ETFE薄膜撕裂抗力-位移曲线及其典型撕裂曲线
Figure 6. Tearing strength-displacement curves and typical tearing curve of ETFE foils with different slit lengths
图 7 不同切缝角度的ETFE薄膜撕裂抗力-位移曲线
Figure 7. Tearing strength-displacement curves for ETFE foils with different slit angles
图 8 不同切缝角度的ETFE薄膜切缝尖端邻域的竖向应变场云图
Figure 8. Vertical strain field nephograms in the neighborhood of the slit tip of ETFE foils with different slit angles
图 9 不同切口样式的ETFE薄膜撕裂抗力-位移曲线
Figure 9. Tearing strength-displacement curves of ETFE foils with different notch shapes
图 10 典型撕裂试样损伤模式示意图：(a)“一”形切缝和(b)圆形切口
Figure 10. Schematic representation of typical damage modes of the tearing specimens: (a) “—” shaped slit ,and (b) circle notch
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