Central tearing mechanical behavior of warp-knitted fabric materials considering high temperature of summer-photovoltaic effect

Under the high-temperature environment caused by solar radiation and heat transfer from photovoltaic components, the membrane material in photovoltaic membrane structures tends to experience defect propagation and tearing failure under external loads. To elucidate the tearing mechanism at elevated temperatures, high-temperature uniaxial central tearing tests were performed on PVDF-coated warp-knitted fabric materials. The effects of temperature and off-axis angle on the tearing behavior were analyzed using digital image correlation (DIC) techniques. Results indicate that the tearing process and the load-displacement response of the PVDF material can be divided into four distinct stages, with a pronounced strain concentration observed at the notch tip. High temperatures weaken the interaction between the coating and fibers, leading to a significant reduction in material stiffness. Specifically, at 100℃, the elastic stiffness decreases by 72.1% compared with that at 25℃, and the failure mode transitions from “gradual” to “abrupt”. The off-axis angle significantly affects the tearing response, with the critical tearing resistance exhibiting a “W-shaped” variation, peaking at 45° and decreasing to approximately 30% of the maximum value near 30° and 60°. The peak displacement displays an inverted “V-shaped” trend. This study elucidates the tearing characteristics of fabric membranes under high-temperature conditions, providing valuable insights for the safety assessment of photovoltaic membrane systems.