拉剪耦合应力对经编织物类膜材双轴撕裂破坏影响机制

Biaxial Tearing Behaviors and Mechanisms of Warp-Knitted Fabric Membranes Under Combined Shear and Tensile Stresses

为探讨拉剪共存应力下织物膜材面内撕裂力学及强度规律,针对典型的经编织物膜材,结合试验与细观数值方法,进行了系列应力比、应力水平、增强膜样式及耦合应力下膜材撕裂破坏特征及强度规律研究,重点挖掘了行为拉剪耦合应力对撕裂强度及破坏特征的影响机制。结果表明不同切缝角度及应力比下,可形成3类膜材裂口:“一”、“十”及“Z”型,而破坏模式均为经或纬纱断裂,未出现两向杂糅;经纬应力存在相互协同作用,且对撕裂强度影响显著,不同切缝参数下破坏强度分布曲线在应力空间中差异明显且存在向1∶1强化的特征。增强膜配合应力状态可明显干扰膜材撕裂破坏模式及裂口位置,且增强膜补强效果因应力比高低存在稍许差异。另外撕裂过程中拉剪应力存在耦合关联性,且以拉应力效应为主,而剪应力对裂纹延展及演变的影响不明显。所得结论可为织物膜材局部裂纹止裂及膜结构的安全性评估提供参考。

In order to explore the in-plane tearing behaviors and strength characters of fabric membranes under combined shear and tensile stresses,experimental and mesoscale numerical studies were conducted on a typical warp-knitted fabric membrane.Its specific tearing behaviors and strength characters under a series of stress ratios and stress levels,reinforced film types and coupled stresses were obtained,and the tearing mechanisms and failure behaviors of the material affected by shear-tension coupling stresses were analyzed.Results show that the fabric membranes could produce three kinds of appearance in terms of the orientation of the tear:line-shaped,cross-shaped,and Z-shaped opening,which is depended on the crack orientation and stress states imposed on them,and the corresponding damage directions of yarns could belong to either warp or weft mode,instead of mixed modes.The stress states in warp and weft directions show the synergistic effect to offer the resistance to tear propagation,which affects the tearing strength obviously and leads to significant differences of tearing strength curves for different crack parameters in the stress space,resulting in the occurrence of stress strengthening at the stress ratio 1∶1.The stress state combined with reinforced film can obviously interfere with the tearing damage modes and crack position of membrane material,and the reinforcing effect varies depending on the stress ratios.In addition,during the tea-ring process,there is a coupling relationship between the tensile and shear stresses,and the tensile stress effect is the main one,while the shear stress has no obvious effect on the crack propagation and evolution.The research findings could provide references for the localized crack arresting of fabric membrane materials and safety assessment of membrane structures.