Small-Scale Mechanical Testing of Space-Exposed Fluorinated Ethylene Propylene Film Obtained From the Hubble Space Telescope

Small-scale materials testing techniques were employed to characterize the mechanical response of aluminized Teflon fluorinated ethylene propylene (Al-FEP) from the outer layer of thermal insulation from the Hubble Space Telescope.  This material was retrieved from the telescope in May 2009 during servicing mission IV and has been exposed for over 19 years to the damaging environmental effects of radiation, solar wind, thermal cycling, space debris, and atomic oxygen. The Al-FEP, initially 130 microns thick, exhibited varying degrees of reduced thickness and erosion of the vapor deposited aluminum layer.  The specimens for mechanical testing came from three unique regions of the telescope based on different levels of space environmental exposure.  In addition to the space-exposed material, pristine Al-FEP was tested as a control.  Due to the limited amount and degraded nature of the exposed material, small-scale tensile tests were performed to assess the mechanical properties while minimizing the impact of cracks and defects on the test results.  The three sets of space-exposed material in this study show progressively lower levels of ultimate strength with increased exposure to the space environment.  Averages of the elastic moduli also suggest a decline with increased exposure, though variability within the data leaves this trend indefinite.  This presentation will discuss the measured tensile strengths, moduli, and strain to failure for Al-FEP test specimens collected from select regions of the exterior of the Hubble Space Telescope during service mission IV.