Dottorato in INGEGNERIA AERONAUTICA E SPAZIALE

Titolo della tesi: Advanced materials for radiation shielding applications in support of human space exploration

The Thesis focuses on the development, characterization and FFF fabrication of advanced composite and nanocomposite materials. In particular, this research aims at finding a solution to the problem of the multifunctionality and of the fabrication of structures in space to enable future manned Mars missions. In fact, future manned missions beyond low-Earth orbit (LEO) cannot occur without long-term survival strategies that include the development of multifunctional materials having high radiation shielding capabilities and of in-situ resources utilization (ISRU) manufacturing technologies to limit Earth supplies. Polymer materials are rich in carbon, oxygen and hydrogen and therefore have desirable properties for space radiation protection. Among the polymeric materials, polyethylene (PE) is the solid material with the best shielding effectiveness, even though it does not have enough strength and thermal stability to be a structural material. Epoxy resins exhibit good mechanical strength and thermal stability, but they are dielectric polymers and degrade rapidly when irradiated. A solution to the poor multifunctionality of polymers is provided by carbon-based nanocomposite materials. Carbon nanoparticles such as graphene nanoplatelets (GNP) and carbon nanotubes (CNT), could lead to novel materials with potentially enhanced mechanical and functional properties: high electrical conductivity for static charge dissipation, high thermal conductivity, radiation hardness, and mechanical integrity. Interplanetary manned missions, for which cargo resupply is not possible, further require the development of in-situ resources utilization (ISRU) manufacturing technologies. Additive manufacturing (AM) is increasingly viewed as an interesting approach for the in-situ manufacturing of buildings and items, using regolith (RG) as a feedstock material. Among the AM techniques, fused filament fabrication (FFF) has been successfully used to fabricate components in a micro-gravity environment aboard the International Space Station (ISS), during the NASA Zero G Technology Demonstration Mission. FFF is characterized by low costs, design flexibility, high precision and dimensional accuracy and in contrast to other AM approaches, FFF-printed parts can be easily recycled, reducing the risks and logistics issues related to long duration space missions. In this Thesis, numerical and experimental analysis are carried out to investigate the potential use of epoxy and polyethylene composites and nanocomposites in future Mars missions. In particular, the studies performed in this Thesis on the multifunctional properties and on the FFF fabrication of these novel materials take us one step closer to the use and 3D printing of functional devices and structures in space.