Fracture and Fatigue Analysis of 15% Chopped Glass Fiber Reinforced PTFE

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Abstract
The fracture and fatigue behavior of 15% chopped glass fiber reinforced PTFE was studied. Two fracture regions were observed with the static tensile failure of this material. Torn ligament bundles, pulled out fibers and microfibrillation are the fracture surface features associated with the first region. These features were responsible for the initial slow crack observed during tensile loading. The second region was characterized by a smoother surface with little damage associated features resulting in an unstable crack propagation. The Modified Crack Layer Model was used to analyze the fatigue crack propagation behavior of the material. The fatigue fracture surface of the 15% glass fiber reinforced PTFE showed three distinct regions. These regions were comparable in location with the three stages of fatigue crack propagation (FCP) kinetics of this material. A large number of torn fracture ligaments and long fibrils were observed in the first region, which is associated with the threshold state of FCP. Extensive random fibrillation was found in the second fracture region which was associated with the second stage of FCP kinetics (stage of reduced acceleration). Undrawn matrix, very little fibrillation and a smooth surface were the fracture surface features of the third region. This region was associated with the third stage, unstable crack propagation, of FCP kinetics.