Uniaxial tensile central tearing behaviors of ethylene tetrafluoroethylene foils

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.