Electrical behavior of CNT epoxy composites under in-situ simulated space environments

Abstract

The properties of CNT composites are known to suffer changes when exposed to space conditions or simulated space environments. A more in-depth understanding of the magnitude of those changes could help improve the design of systems that contain them, produce more accurate predictions of their performance, or even open the possibility of new applications. In this study, the electrical properties of CNT epoxy composites containing low CNT loadings (less than 1%) were measured in-situ while the specimens were exposed to diverse simulated space conditions. A thermal vacuum chamber was employed to produce the low pressures and temperatures associated with low earth orbit. A solar simulator was used to replicate solar irradiance. A convection oven was used to determine the effects that could only be attributed to temperature variations. The changes in resistivity exhibited by the composite specimens are reported for each scenario along possible mechanisms that could explain the observed behavior. The microstructural and thermogravimetric characterization of the composites for the diverse loadings is also presented. Resistivity reductions of up to 40% were observed by the simultaneous application of high temperatures and low pressures, while the application of simulated sunlight with the concomitant surge in temperature, showed a maximum decrease of 58%. Outgassing and an increase in the number of charge carriers at the higher temperatures promoted by the simulated sunlight treatment, are believed to be responsible for the recorded reductions in resistivity. A qualitative analysis of the resistivity changes noted when the composites are exposed back to atmospheric conditions is included.