This study systematically investigates the indentation deformation behavior of polytetrafluoroethylene (PTFE) membranes used for water purification. The examined PTFE membrane has micron-sized pores with an open cell structure. The pore structure is anisotropic in shape owing to its fabrication via the stretching method. A uniaxial tension demonstrates the membranes undergo elastic and plastic deformation with significant anisotropy (as the deformation behavior differed between the longitudinal and transverse directions). To clarify the microscopic deformation mechanism, in-situ SEM observations were carried out during uni-axial tensile loading. It was found that the anisotropic deformation behavior appeared due to the inherent pore structure. Next, to investigate the indentation deformation behavior, small punch (SP) tests using a spherical indenter were carried out. The membrane underwent both elastic and plastic deformations. Finally, a crack nucleated around the indenter contact area and the indenter completely penetrated through the membrane. It was also found that the membrane demonstrates an anisotropic out-of-plane deformation behavior. To clarify these mechanisms, an FEM computation was carried out, with the experimental results of the force–displacement curve and the out-of-plane deformation behavior agreeing with the computational results. The present FEM model enables the prediction of the deformation behavior of the membrane under indentation loading.

本研究系统地研究了用于水净化的聚四氟乙烯（PTFE）膜的压痕变形行为。检查的PTFE膜具有微米大小的孔，具有开孔结构。孔结构由于通过拉伸方法制造而形状各向异性。单轴张力表明膜经历了显着的各向异性的弹性和塑性变形（因为变形特性在纵向和横向之间有所不同）。为了阐明微观变形机理，在单轴拉伸载荷过程中进行了原位SEM观察。发现由于固有的孔结构而出现各向异性变形行为。接下来，研究压痕变形行为，使用球形压头进行小冲孔（SP）测试。膜既发生弹性变形又发生塑性变形。最终，裂纹在压头接触区域周围成核，并且压头完全穿透了膜。还发现该膜表现出各向异性的面外变形行为。为了阐明这些机理，进行了有限元计算，力-位移曲线和平面外变形行为的实验结果与计算结果一致。本有限元模型能够预测压痕载荷作用下膜的变形行为。裂纹在压头接触区域周围成核，并且压头完全穿透了膜。还发现该膜表现出各向异性的面外变形行为。为了阐明这些机理，进行了有限元计算，力-位移曲线和面外变形行为的实验结果与计算结果一致。本有限元模型能够预测压痕载荷作用下膜的变形行为。裂纹在压头接触区域周围成核，并且压头完全穿透了膜。还发现该膜表现出各向异性的面外变形行为。为了阐明这些机理，进行了有限元计算，力-位移曲线和面外变形行为的实验结果与计算结果一致。本有限元模型能够预测压痕载荷作用下膜的变形行为。力-位移曲线和平面外变形行为的实验结果与计算结果一致。本有限元模型能够预测压痕载荷作用下膜的变形行为。力-位移曲线和平面外变形行为的实验结果与计算结果一致。本有限元模型能够预测压痕载荷作用下膜的变形行为。