Spacecraft experience minimal mechanical loads in space, but with the development of reusable spacecraft for interplanetary exploration and repeated landings, structures will be subjected to increased mechanical stress. The impact of the space environment on the aging of adhesive materials used in space structures over long-term applications is not well understood. This study investigates two commonly used adhesives in spacecraft assembly, namely Scotch-Weld™ EC-2216 and Scotch-Weld™ EC-9323-2, under two aging conditions: (1) high-energy electron irradiation using a Van de Graaf accelerator, and (2) thermal vacuum cycling. The research evaluates the evolution of intrinsic adhesive properties and adhesion to CFRP (carbon fiber-reinforced polymer) and aluminum adherents before and after exposure to these environmental conditions through tensile tests, peel tests, double-cantilever beam (DCB) tests, and dynamic mechanical analysis (DMA).@en

Spacecrafts are subjected to very few mechanical loads but in the future with reusable spacecraft designed for interplanetary explorations and with the repetition of landing and take off, structures will be subjected to significant mechanical loads. The degradation due to space aging conditions, of the adhesive materials used as joints in space structure is not known yet for such a reusable spacecraft on long term exploration. Two adhesives used in spacecraft structures were investigated: Scotch-Weld EC-2216 and Scotch- WeldTM EC-9323-2. Those adhesives were exposed to two aging conditions from a space environment point of view: (1) electron irradiation using a Van de Graaf particle accelerator and (2) thermal vacuum cycling. Change in the adhesives properties was assessed before and after space environment exposure to understand related effect on their mechanical performance using CFRP and aluminium adherents, including, tensile tests, peel tests, double cantilever beam (DCB) tests, as well as evolution of their intrinsic properties by mean of dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC) and fourier transformed infrared spectroscopy (FTIR). It has been found that electron irradiation accelerates the completion of the curing reaction in EC-2216 and reduces fracture toughness, peel load, Young’s modulus, tensile strenght for both adhesives, which degrade adhesion integrity. The effects of thermal vacuum cycling on adhesives and adhesion differ, with certain attributes being reduced as Young Modulus, tensile strength or glass transition temperature and others being increased as fracture toughness. Effects of space environment are visible and very significant on these adhesives. The results of this study form a preliminary basis for long term prediction of adhesive bond behaviour in space. @en

The purpose of this research was to investigate the suitability of the Fused Filament Fabrication (FFF) process for low pressure/vacuum environment. This included investigating the ability of an FFF printer to function in a vacuum and evaluation of the dimensional accuracy and mechanical properties of the manufactured components. For this purpose, a commercially available FFF printer using polycarbonate as raw material was placed in a vacuum environment of 10 mbar. Test components were then fabricated in vacuum with a control group fabricated in a normal atmosphere (1 bar). Test components were evaluated for dimensional and mass accuracy, quality and presence of defects. Flexural, tensile and compressive testing was carried out according to ASTM D790, D638 and D695 respectively. Dimensional analysis of components showed equivalent small deviation for both environments. Components fabricated in the vacuum environment had 5.4% higher tensile yield strength and 59% higher extension at break compared to components printed in a normal atmosphere indicating an increased strength and ductility. Components tested in compression had approximately 11.2% higher compressive strength when printed in a vacuum environment. No differences were observed during the flexural test. In space, due to the vacuum environment, polymers and organic material are susceptible to release molecules via an outgassing process. Assessment of the molecular organic contamination generate during the printing process in vacuum is low and seems to mostly originated from the components of the printer. The results provided demonstrated the possibility to use the FFF process in a vacuum environment to fabricate dimensionally accurate, high-quality polycarbonate components with a variety of geometries without loss of mechanical performance. This work provides a proof of concept that FFF can be used to develop out-of-earth manufacturing technologies (in orbit/in space/on planet) allowing part production for new maintenance and repair strategy or to potentially manufacture entire structure more efficiently overpassing launch constrain by using only raw material brought from earth.

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