Jan 2024
Abstract
There is a strong need for long life bearings and tribological surfaces for expanding the ability of NASA and other space companies and agencies to explore the deep atmosphere and surface of different planets and comets using long-lived (days or weeks) balloons and landers. The missions would experience extreme temperatures - ranging from cryogenic temperatures of -220°C on Europa to upwards of 462°C on Venus, which impede the use of traditional oil lubricants and greases, resulting in dry sliding conditions that generally have significant detrimental effects on component performance; with the addition of abrasive dusty environment in Mars, the complexity is further compounded. To address these challenges, high-performance polymers (HPPs) based on polyether ether ketone (PEEK), polytetrafluoroethylene (PTFE), polyimide (PI), and aromatic thermosetting co-polyester (ATSP) were developed for tribological experiments at extreme temperatures ranging from -196 to 300°C, simulating extreme operating conditions that bearing materials in space will encounter. ATSP polymer composite was shown to outperform the other groups of HPPs with low coefficient of friction and unmeasurable “zero” wear from cryogenic to high temperatures (-196°C to 300°C) under dry sliding conditions, expanding the application of the polymer to 500°C temperature range. In addition, polymer-on-polymer sliding significantly mitigated the sand and dust accumulation at the interface, which is advantageous for Lunar/Mars explorations.
Bio
Dr. Polycarpou received his Ph.D. from the State University of New York at Buffalo in 1994. Before joining the University of Tulsa is 2023, he was at Texas A&M University from 2012-2023 holding the James Cain Chair and serving as Department Head of Mechanical Engineering and Acting Dean of Dentistry. From 1999-2012 he was the Wilkins Professor at the University of Illinois Urbana-Champaign, and while on leave of absence, he had a short stint at Khalifa University in Abu Dhabi as founding department Chair. Dr. Polycarpou’s research interests include tribology, micro/nanotribology, nanomechanics, microtribodynamics, and advanced interface materials. Emphasis has been on micro/nanoscale contact problems with applications to micro-devices, as well as the tribology of devices for reduced energy and improved environmental-related impact. Polycarpou is the author of over 260 archival journal papers, numerous book chapters, volume proceedings, and two dozen patents. Polycarpou won numerous national and international awards, most recently the ASME Hersey Award, and the ASME Church Medal. Polycarpou is active in the tribology and mechanics communities, where he served in many posts, including Chairing the ASME Tribology Division, and ASME’s Department Heads Council.