In situ self-sensing in epoxy-lunar regolith simulant composites with and without carbon nanotube inclusions under compression

Abstract The advent of the Artemis missions and emphasis on the creation of a sustainable Lunar surface presence is driving research into the creation of Lunar construction materials. Numerous methods of utilizing Lunar regolith as a structural composite material have been previously explored, including those which rely on thermal energy and those which require an added binder for fusing of particles into a cohesive material. Multifunctional composites are especially attractive because they have the potential to decrease the cost, complexity, and risk of deployed systems. Research has shown that structural health monitoring (SHM) capabilities can be achieved through the incorporation of multiwalled carbon nanotubes (MWCNTs) into the matrices of polymer composites, but to date the utility of this method when applied to polymer-bonded regolith composites (PBRCs) has not been explored. In this study, epoxy/regolith simulant PBRCs were created with a binder/filler weight ratio of 18/82, while binder MWCNT content was varied from 0-3% by weight. EPON 862 epoxy resin and EPIKURE Curing Agent W were mixed in a 100/26.4 weight ratio and combined with the applicable MWCNT concentration, after which this binder system was combined with LHS-1 Lunar regolith simulant. Electrodes were attached to ASTM D695 specimens of each material system, and initial electrical properties were gathered before compression testing utilizing an Instron uniaxial testing frame with a crosshead displacement rate of 1.3 mm/min. Concurrently, an inductance-capacitance-resistance (LCR) meter passed 2V AC at 10kHz through the attached electrodes. Normalized changes in resistance and reactance response were recorded and associated with specimen stress-strain behavior. Statistical, numerical and graphical analyses showed close correlations between multiple electrical and mechanical metrics, including detection of individual damage events, although the strengths of these correlations varied with composition.