Assessing the Space-Worthiness of Additively Manufactured Liquid Crystal Polymers

Abstract

As space exploration advances toward colonization missions on the Moon and Mars, there is an increasing need for lightweight, recyclable, and space-worthy materials. These materials must optimize payload and sustainability by integrating 3D printing and recycling mechanisms, minimizing the need to transport bulky construction materials from Earth and reducing space debris. Additive manufacturing, particularly Fused Filament Fabrication (FFF), offers significant design flexibility, ideal for zero/low gravity environments. However, the relatively low material properties and durability of polymers in space restrict their potential compared to metals. Liquid Crystal Polymers (LCPs) show promise due to their high crystallinity, flame retardancy, and thermotropic properties. Yet, their behavior in space environments remains underexplored. The goal of this research is to evaluates the performance of Vectra A950, an LCP, under electron beam radiation and thermal vacuum (TVAC) exposure, as well as its recyclability after FFF processing.

The study examines the mechanical strength, thermal stability, and crystallinity of 3D-printed LCP under space-like conditions. Samples were subjected to three levels of electron beam radiation and TVAC. Electron irradiation induced annealable color centers, manifesting as a green hue that intensified with higher radiation doses, which could be reversed by annealing for 20 minutes at 200°C. The findings indicate that while exposure to electron beam radiation and TVAC has a measurable impact on the mechanical properties of LCP, the changes are not significant enough to compromise its structural integrity. For irradiated samples, no substantial variations were observed in Young’s modulus or ultimate tensile strength (UTS) across different radiation fluences, even after TVAC exposure. However, when exposing unirradiated samples printed at low printing temperatures (295°C and 310°C) to TVAC, slight reductions in Young’s modulus were observed with no significant impact on UTS. Thermal analysis revealed that electron beam radiation modestly shifted the β-peak temperature, while TVAC increased the glass transition temperature by 5°C in irradiated samples. Samples exposed to high fluence displayed a permanent decrease in melting temperature by over 7°C, suggesting irreversible changes to the polymer structure.

The study also explored the effects of electron beam radiation, annealing and FFF processing on the recyclability of LCP. Results indicate that while these processes alter thermal and mechanical properties, the effects of annealing and FFF are potentially thermoreversible. FTIR analysis revealed no chemical modifications to the polymer structure, confirming that FFF does not chemically alter LCP, reinforcing its potential for in-situ recycling during planetary exploration. While LCP shows promising recyclability under various conditions, further research is needed to fully understand the reversibility of these changes and their implications for in-situ recycling in space environments.

Overall, the study concludes that, LCP demonstrates mechanical and thermal stability under moderate radiation and thermal vacuum exposure, making it suitable for long-term use in space. Its potential for recyclability, combined with the design flexibility of FFF, supports its viability for space missions, particularly in optimizing sustainability and resource utilization.