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.

The aerospace sector continues to drive innovations in high-performance materials. These materials however, tend to have energy intensive and emission heavy manufacturing processes. One of the most commonly used materials in aircrafts today are polymer matrix composites consisting of reinforcement fibers and a matrix. While the fibers provide the most strength to the composite, the matrix holds the fibers together and transfers the loads to them. The most commonly used matrix material today is made of BADGE (Bisphenol A Diglycidyl Ether), a material which is toxic to humans and comes from fossil-based products.

This thesis investigates the viability of a vanillin-derived bio-based alternative, VDE (Vanillyl Alcohol Diglycidyl Ether), to be used in high-performance composites for aerospace applications. VDE monomer is derived from vanillin, which is obtained from lignin, a material present in 35% of woody plants. The VDE-DDS resin system, when cured, exhibited comparable thermal and physical properties, such as glass transition temperature and heat deflection temperature, to traditional aerospace resins like BADGE-DDS. Mechanical testing, including tensile, flexural, and fracture toughness, demonstrated promising results, with VDE-DDS showing higher strength and modulus than BADGE-DDS. The flexural strength was considerably higher in particular. However, its hydrophilic nature led to higher water absorption, a challenge for long-term durability. For further testing, composite specimens were prepared using an autoclave.

Composite specimens reinforced with VDE-DDS displayed greater stiffness and strength under mechanical testing compared to BADGE-DDS in tests of in-plane shear strength, compression and inter-laminar shear strength tests, though BADGE-DDS composites outperformed in low-velocity impact resistance. The impact testing also revealed that BADGE-DDS samples had a higher damage initiation energy while VDE-DDS samples had a higher bending stiffness. Overall, VDE-DDS offers comparable, if not better, thermal and mechanical characteristics to BADGE-DDS. VDE, in summary, presents a compelling case as a potential bio-based alternative for structural aerospace applications.

Shape Memory Alloys (SMAs) are a class of metallic multi-functional materials which possess sensing and actuation capabilities, thanks to their unique ability to couple thermal and mechanical fields. NiTi-based Shape Memory Alloys exhibit properties which guarantee their high performance in adverse environments and, with the added benefit of two functionalities, the Shape Memory Effect and Superelasticity, these materials have become ideal candidates for a variety of applications. Spatial orientation of the NiTi crystals is crucial for achieving the superelastic functional response. According to studies on NiTi single crystals, when the grains adopt a [001] orientation along the direction of compression, slip is inhibited in the austenite phase and recoverable transformation strains similar to the theoretically estimated values of 5.3% are possible, defining the benchmark for superelastic responses. Additive Manufacturing techniques, due to their inherent thermal processing conditions, have created unprecedented opportunities for fabrication of NiTi-based Shape Memory Alloys so that the thermomechanical behaviour of the material can be tailored to any application is intended for. During Laser- Powder Bed Fusion, the scanning strategy influences the thermal processing to which the alloy is subjected, affecting its solidification process as well as the heat fluxes and temperature gradients that arise during manufacturing. Meanwhile, it can play a decisive role in achieving epitaxial solidification of columnar grains extending over multiple deposition layers. In this study, five different scanning strategies were employed during Laser-Powder Bed Fusion (L-PBF) of a Ni-rich NiTi alloy and were evaluated with respect to the grain morphology and crystallographic texture that developed, as well as the superelastic response of the samples produced. It was found that a 67° interlayer rotation of the scanning vector promotes the fusion of neighbouring melt pools, resulting in columnar grains that solidify epitaxially along the build direction (BD) of the sample. Meanwhile, a strong ⟨001⟩ fibre texture emerges along the BD. The superelastic response was stabilised at 4.5% recoverable strain with 74.2% recovery ratio after 16 cycles of axial compression loading. When an island scanning pattern was incorporated into the 67° rotation scanning strategy, the crystallographic texture strengthened and the superelastic response improved, (5.0% stabilised recoverable strain and 84% recovery ratio). Furthermore, an increase in the volumetric energy density, achieved by using a flat top laser beam, produced a nearly single-crystalline microstructure, with the highest intensity of the ⟨001⟩∥BD texture. The superelasticity in this case was stabilised at 5.5% recoverable strain with 91.5% recovery ratio. The effect of the loading direction on the superelastic response was also investigated, as was the nature of the residual strain left in the samples after their superelasticity stabilised. Therefore, this study successfully demonstrated that the scanning strategy can be a vital tool in designing the crystallographic texture and the grain morphology of NiTi parts fabricated by L-PBF, and this way, effectively tailor the superelastic functional behaviour to specific requirements of potential applications.

he radiation shielding capabilities of polymers and Martian regolith simulant MGS-1 are analysed by means of the dose reduction of the absorbed dose radiation quantity. MGS-1 is an analog for Martian surface material while polymers are generally an effective radiation shielding material because of its high hydrogen content. Scenarios of a radiation shield and simplified Martian habitat are defined and simulated in FLUKA. The source of the radiation is a selection of radiation particle types from Galactic Cosmic Rays (GCR) in the Martian environment during a solar minimum, when GCR contributions are largest. Secondary radiation neutrons are substantially the largest contributor to the total flux on Mars, followed by protons, helium and heavy ions.

The density of the MGS-1 shield was found to have a significant influence on the dose reduction while the influence of a polymer layer in a thick MGS-1 shield did not yield beneficial gains in dose reduction. Using a simplified Martian habitat with a 250 cm thick shield resulted in a dose reduction of the selected particles of more than 90%.