Fatigue testing of polymer membranes

Abstract This paper presents a new impression method for fatigue testing polymer membranes that circumvents many of the problems associated with traditional uniaxial testing of thin, compliant films. The proposed test geometry subjects the polymer membrane to a biaxial stress state by displacing the center of a clamped circular specimen with a spherical indenter. The initiation of fatigue cracks in the membrane is monitored using optical and/or infrared sensing. Finite element and non‐linear membrane theory models, which take into account large‐displacement kinematics, non‐linear material behavior and friction between the indenter and membrane, are used to establish connections between the applied indenter displacement, or load, and the stress in the film. A key result is a closed‐form relationship between applied load and membrane stress, which can be used for a wide range of friction and material response. The broadly applicable approach is demonstrated using two types of laminated polymer membranes. Polym. Compos. 25:442–450, 2004. © 2004 Society of Plastics Engineers.