Dynamic Epoxy Concrete Composites for Lunar Habitats

Thermoset polymer glasses are promising material candidates for use in the harsh environmental conditions relevant to aerospace and space applications because of their robust thermomechanical properties, chemical resistance, and low mass density; however, these polymeric materials can suffer from brittleness and sensitivity to some forms of radiation due to their highly crosslinked structure and chemical constituents. Thermoset polymers and their composites also tend to be unrecyclable because of the covalent crosslinks present in these network materials. In recent years, the incorporation of dynamic covalent bonds into thermosets has been utilized to improve their recyclability, leading to the development of a class of polymers known as vitrimers or covalent adaptable networks (CANs). Recent work has shown that the inclusion of dynamic, aromatic disulfide bonds in high-performance epoxy glasses not only endows these materials with reprocessability (improving sustainability and material lifetime), but also can be used to improve material toughness without sacrificing strength [1-3]. This work investigates the use of these healable and mechanically robust polymers as matrices in highly filled composites for use as structural materials for lunar habitats via <i>in situ</i> regolith utilization (ISRU). Specifically, a series of dynamic, disulfide-containing epoxies and composite concretes with 80-90 wt% lunar regolith simulant have been fabricated to study their fracture and mechanical properties over the broad temperature range relevant to the lunar surface. Additional multi-functional fillers being used to improve the composite resistance to various forms of radiation and demonstrations of the reprocessability of the materials will also be discussed. The structure-property relationships developed will be used to optimize materials for structural integrity, radiation resistance, and reprocessability, while minimizing the weight of polymer matrix needed to save costs for lunar missions.<br/><br/>References<br/>[1] Ruiz de Luzuriaga, A. et al., <i>Materials Horizons</i>, (<b>2016</b>), 3, 3, 241-247.<br/>[2] Takahashi, A.; Ohishi, T.; Gosecki, R.; Otsuka, H., <i>Polymer</i>, (<b>2016</b>), 82, 319-326.<br/>[3] Lewis, B. L.; Dennis, J. M.; Shull, K. R., <i>ACS Appl. Polym. Mater.</i> (<b>2023</b>), 5, 4, 2583-2595.