Design and Validation of Test Structures for Space Additive Manufacturing

Space debris has grown to over 25,000 known human-made objects that congest satellite orbits and pose a threat to the safety of astronauts and future missions. Much of this waste is composed of metals with the potential to be recycled for sustainable in-space manufacturing. Additive manufacturing is ideal for space applications because existing debris can be processed into feedstock to create new parts, maximizing efficiency while producing near zero waste. Nonetheless, qualification of AM parts remains a challenge in space due to environmental constraints of earth-based testing. The development of standards for in-space additive manufacturing is an essential first step toward safe and sustainable human activities in space. For this purpose, the objective of this work is to design, manufacture, and validate test structures for destructive and nondestructive mechanical characterization. Maraging steel test samples were successfully printed on a build plate with Laser Powder Bed Fusion. From this plate, cube, cylinder, and dogbone samples were selected for evaluation from various print orientations, to account for discrepancies in position and observed performance. Nondestructive ultrasound wave speed and backscatter tests as well as X-ray CT scans were collected to identify microstructural features that may affect material behavior. Destructive mechanical tests produced stress-strain curves to inform material properties and potential weaknesses correlated with microstructural defects and grain patterns inherent to Laser Powder Bed Fusion, and identified through nondestructive methods. Finally, these grain patterns and pore defects are visually observed and characterized via optical microscopy. The results from these evaluations will be applied to the development and validation of finite element models, a critical step toward predicting the behavior of regolith-metal products composed of space-debris. Such models are essential to understand the macroscopic behavior of additively manufactured parts in a space environment and inform nondestructive and destructive space-viable test protocols and ground demonstrations.