裂纹-孔洞缺陷下PVC涂层织物类膜材的撕裂行为

膜结构节点和边界处往往需要通过膜面开孔来实现关键部位的连接，孔洞边缘的应力集中会影响膜面的撕裂行为。为探究聚氯乙烯(polyvinyl chloride, PVC)涂层织物类膜材中孔洞对裂纹扩展行为的影响，开展了含有裂纹-孔洞缺陷的PVC涂层织物类膜材的单轴拉伸试验，分析了裂纹扩展全过程和撕裂机理，提出了适用于含裂纹-孔洞多缺陷PVC涂层织物类膜材撕裂强度的预测模型，并验证了模型的适用性。研究结果表明：含裂纹-孔洞缺陷的PVC涂层织物类膜材在中心撕裂过程中存在裂纹端扩展和孔端再扩展两阶段；定义了裂纹端临界撕裂荷载、裂纹端峰值撕裂荷载、孔端临界撕裂荷载和孔端峰值撕裂荷载4项撕裂特征指标，以衡量含裂纹-孔洞缺陷膜材的抗撕裂性能；孔洞的存在导致试样在孔端再扩展阶段的承载力提升，但随着孔洞尺寸增大，孔端的承载力提升效应减弱，裂纹端峰值撕裂荷载逐渐变为控制试样破坏的极限荷载；所提出的二次函数-指数函数应力场模型能有效地预测膜材的裂纹端临界撕裂应力和孔端临界撕裂应力。

Tear behavior of PVC-coated fabric with crackhole defects

The hole at the joint and boundary is an important component of the membrane structures and plays a key role in connecting the relevant components. However, the stress concentration is easy at the edges of holes, which has a serious effect on tearing behavior of the coated fabric. To investigate the effect of holes in polyvinyl chloride (PVC) coated fabric on crack propagation behavior. Uniaxial tensile tests of PVC-coated fabric with cracks and holes were carried out. The whole process of tear propagation and tearing mechanism are analyzed. A prediction model for the tear strength of PVC-coated fabric with multiple defects is proposed and the applicability of the model is verified. The results show that there are two stages of crack-end expansion and hole-end re-expansion during the center tearing process of the PVC-coated fabric with cracks and holes. Four tear characteristic indicators are defined to measure the tear resistance of coated fabric with cracks and holes, namely, the critical tearing load at the crack-end and hole-end, the ultimate tearing load at the crack-end and hole-end. The existence of holes leads to the increase in the bearing capacity of the specimen at the re-expansion stage. However, with the size of the hole increasing, the bearing capacity enhancement effect of the hole-end weakens and the ultimate tearing load at the crack-end becomes the maximum tearing load. The proposed quadratic functionexponential function stress field model can effectively predict the critical tear stress at the crack-end and the critical tear stress at the hole-end of the coated fabric.