An experimental investigation of microgravity conditions on FDM-based in-space polymer additive manufacturing

In-orbit additive manufacturing (AM) has the potential to overcome limitations imposed by current launch vehicles, such as restrictions on payload size and weight. Fused Deposition Modeling (FDM), one of the predominant AM techniques used in space, operates in a microgravity environment where interactions between temperature, load, and motion are complex and not well-known. In FDM, surface tension and gravity significantly influence layer deposition, affecting mechanical properties and interlayer bonding. Previous research indicates that gravity may strongly impact layer height and bonding strength during FDM-based AM. This study explores the influence of gravity on interlayer fusion and global mechanical properties by printing specimens at various angles (0 degrees-90 degrees) relative to the gravitational direction. The 0 degrees angle simulates a microgravity environment, while the 90 degrees angle represents Earth-like conditions. Tensile and compressive test specimens were fabricated and evaluated through stress-strain analysis. Tensile tests revealed a decrease in ultimate tensile strength, fracture stress, and strain with increasing print angle from 0 degrees to 75 degrees, followed by a recovery at 90 degrees, likely due to a shift in failure mode at the micro level. Compression tests showed substantial improvements in ultimate compressive strength and modulus between 0 degrees and 15 degrees, with ductility remaining stable across all angles. Dimensional analysis indicated reduced specimen dimensions at higher print angles. The findings suggest that while zero-gravity conditions weaken interlayer bonding, the overall mechanical performance of materials in microgravity is less compromised than under Earth-like conditions. These insights are valuable for optimizing polymer-based AM processes for in-space manufacturing applications.