Mechanical properties of Teflon FEP retrieved from the Hubble Space Telescope

摘要

Teflon FEP (fluorinated ethylene propylene) surfaces on the Hubble Space Telescope (HST) have experienced significant degradation in mechanical properties during nearly ten years of exposure in the low Earth orbit (LEO) environment. This paper describes results of mechanical properties testing of Teflon PEP materials exposed on HST for 9.7 years between launch and the third servicing mission (SM3A) and for 2.8 years between the second servicing mission (SM2) and SM3A. Results of tensile testing, bend testing and microscopic examination of crack morphology are described. Effects of post-retrieval heating and air vs. vacuum storage on the mechanical properties of PEP surfaces are described as they significantly affect interpretation of results regarding the durability of FEP on HST. This paper provides comparisons of the properties of PEP surfaces retrieved during SM3A to previously reported results for FEP materials retrieved during the first servicing mission (SM1) and SM2. Results will be discussed in consideration of the environmental exposure conditions for the HST exposed materials.