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Fatigue Characterization of Fluorogold and Fluorogreen Polymers
MEDHAT AWAD EL-HADEK
The damage dissipated during fatigue crack propagation of uorogold and uorogreen polymeric materials has been studied using an automated data acquisition system (DAS). A low fatigue frequency of 1 Hz was performed under a tension-tension load-control fatigue test. All samples were notched with a notch-to-width ratio a/W of 0.1. Deformation, load, and hysteresis energy loops were measured continuously during the test and analyzed using the DAS. The calculations were based on the energy release rate J* and on the change in work expanded on damage formation and history-dependent viscous dissipative processes _
Wi. The modied crack layer (MCL) model was used for extracting material-related parameters including the specic energy of damagec and the coecient of energy dissipation b. The MCL theory was proven valid for describing the damage and cracking behavior of uorogold and uorogreen materials. The two parameters c and b are also suitable for the evaluation of the resistance to fracture and fatigue crack propagation.
DOI: 10.1007/s11661-013-1972-8 The Minerals, Metals & Materials Society and ASM International 2013
I. INTRODUCTION
AMONG various uorocarbon polymers, polytetra uoroethylene (PTFE), commercially known as Teon, is the most widely used. Due to the strong carbon carbon bond, it has been reported[1] that PTFE is serviceable over a wide temperature range from 5 K to 533 K (268 C to 260 C) without any appreciable change in the physical or mechanical properties. However, limited research can be found in the literature characterizing the mechanical properties of the uoro-carbon polymers. PTFE is a self-lubricating uorocarbon with an extremely low friction coecient below 0.1 that is used with or without llers for diversied application purposes.[2,3] Applications include lubricating high-pressure sealing, protective coatings for materials that are used in the building industry, airplane gaskets, bearings, and O-rings for exible lms.[3]
Furthermore, it has been reported to be used in electrical insulating,[1] microelectronics, microwave, and electro-optical industries due to its unique dielectric and optical properties.[4]
To improve the strength, stiness, and oil resistivity of PTFEs, reinforcements such as chopped berglass and carbon bers are added to PTFE materials. Fiber-glass is widely used as a reinforcement for PTFE to enhance the mechanical properties of PTFE with dierent weight fractions.[5] With the enhancement of the...