Matt Malusky

Date of Award

January 2025

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Mechanical Engineering

First Advisor

Surojit Gupta

Abstract

This research examines polymer wear behaviors across polyether-etherketone (PEEK) and polylactic acid (PLA) composites in varying environmental conditions. Tribological investigations of ceramic and intermetallic coatings are explored in the context of material selection for lunar operation. In the first study, PEEK composites incorporating ternary nanolaminate ceramics, termed MAB and MAX phases, were tested in varying temperature environments above and below their expected glass transition temperatures to evaluate their tribological performance in comparison to a non-reinforced PEEK substrate. Results showed that under ambient conditions, both MoAlB (MAB phase) and Cr2AlC (MAX phase) ceramics stabilize the friction coefficient compared to pure PEEK, although friction is slightly increased due to the presence of ceramic reinforcements. In a 100°C environment, the addition of these ceramics provides less frictional stabilization than at ambient conditions. In a 200°C environment, a low-friction lubricating tribofilm develops for the pure PEEK and 10 vol% Cr2AlC containing samples. However, in 10 vol% MoAlB composites, an unstable high-friction response was observed. A 20 vol% MoAlB concentration showed a reduction in wear and stabilization in friction response, suggesting a critical concentration between 10 and 20 vol% MoAlB reinforcement. The second study explored the friction response and wear performance of ceramic-reinforced PLA composites in the context of lunar surface materials (materials already present or that can be produced from materials already present). Reinforcements included basalt moon dust, zirconium silicate, borosilicate, and silicon carbide. Understanding these tribological behaviors may inform the sintering potential of in-situ resource utilization (ISRU) materials. The results showed that the tribological behavior of PLA-composites is dependent on factors including porosity and particle embedment. For more porous PLA composites, wear performance is reduced with the reduction in mechanical properties. PLA-Zirconium-silicate showed the lowest porosity and best wear performance. Spherical borosilicate reinforcements demonstrated the second-lowest porosity and second-best wear performance. Basalt moon dust showed the highest relative porosity and the worst wear performance. The purpose of the third study was to characterize the effects of a particular lunar highland simulant on various alloys and ceramic coating systems to evaluate the friction and wear performance of these materials in an extreme tribological environment. Results indicated that chromium-carbide containing coatings performed most notably, effectively stabilizing friction response and providing a significant reduction in wear rate as compared to uncoated aluminum and titanium alloy substrate materials.

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