Abstract
Direct-ink-write (DIW) 3D printing of dense composite inks is an attractive method of additive manufacturing for Lunar missions using in-situ derived resources. DIW offers a wide degree of freedom for formulation design with multiple methods for solidifying the inks post-extrusion. The use of UV-curing, however, poses certain complications when the loading of particles in the ink reaches levels above 50 vol% due to light scattering, absorption, and reflection. Herein, we investigate the curability of two Lunar regolith simulants, compared against a model system of glass microspheres, as particles in UV-curable inks. Photo-DSC is utilized to assess the degree of cure of the inks at a range of timescales. These results are tied to depth of cure experiments following the ISO 4049 method to verify cure depths meeting a target print layer height and to optimize the speed of printing while maintaining structural integrity. The extent of cure is verified both qualitatively through print shape fidelity and quantitatively through ATR-FTIR. This work not only highlights the importance of particle mineralogy for achievable UV-assisted solidification post-extrusion, but also presents test methods easily adapted to a design of experiment framework that require very little sample volume to identify successful formulations and printing parameters.
