# Regolith-Rich PEEK Composite Bricks: Steps Towards Space-Ready Lunar Construction Materials
## 5 Conclusions  
This study explored regolith-based composites with minimal thermoplastic binders, selecting PEEK as the binder after a thorough trade-off analysis of manufacturing and environmental constraints. The manufacturing process involved compacting regolith grains and binder powders in molds, heating to melt the binder, and cooling to solidify the composite. The effects of binder content and compaction on compression and bending properties were evaluated under varying conditions, including vacuum and different temperatures. The results demonstrated the feasibility of producing standardized components with mechanical properties compatible with or exceeding equivalent lunar construction requirements:  
* A binder content of 5 wt% met and exceeded equivalent compression strength requirements for lunar applications, including building and paving bricks. * The compression strength needed for lunar concrete applications, such as basement walls, slabs, and reinforced beams, was achieved with 5 wt% binder. * At 10 wt%, the composite satisfied strength requirements for similar Earth-based structures. * Bending strength results mirrored these trends, with 5 wt% meeting the equivalent performance for conventional and reinforced concretes on the Moon, and 10 wt% ensuring compliance for Earth-based requirements. Figure 11: Compression strength: comparison of the requirements for different brick applications [18; 19; 20; 63] against experimental data. The black dots show the bending strengths of DoE samples (cured in air, tested at +20 °C); the additional points associated with run 8 (same compaction pressure and binder percentage) represent samples cured in vacuum and tested at various temperatures. * Vacuum curing significantly enhanced mechanical properties, enabling compatibility with all lunar and most Earth-based requirements. * Binder weight percentage and powder compaction positively influenced all mechanical properties. The minimal binder content and low pressures used in the process underscore its scalability for larger structures. Despite these promising results, several limitations must be overcome before this formulation can be effectively adapted for applications on the lunar surface:  
* Thermal and Mechanical Constraints: The performance of PEEK-based composites under the combined extreme thermal cycling and radiation exposure on the Moon requires further validation. Current tests only partially replicate lunar conditions, and additional experimentation under representative environments will be crucial. * Processing Efficiency: Achieving vacuum processing on a medium to large scale with precise temperature control poses significant engineering challenges, especially given the limited power and mass budget of lunar missions. * Material Availability: While regolith is abundant on the Moon surface, ensuring the uniformity of particle size and composition for consistent performance remains a logistical and processing challenge at the time. To build on the findings of this study, several avenues for future research are here proposed:  
* Environmental Testing: Conduct extended experiments under conditions that more accurately mimic the lunar environment, including prolonged exposure to high vacuum, thermal cycling, and micro-meteoroid impacts. To address these added issues in the real environment, novel solutions could be proposed such as the integration of additional fillers or external coatings to improve radiation resistance, and mechanical toughness. * Automation and In Situ Adaptability: Develop autonomous systems for regolith collection, material processing, and construction to align with lunar mission constraints. * Multi-functional Applications: Investigate the feasibility of these composites in multifunctional roles, such as structural components that also serve as radiation shielding or thermal insulation.