Comparison of thermal insulation performance of fibrous materials for the advanced space suit.
The current multi-layer insulation used in the extravehicular mobility unit (EMU) will not be effective in the atmosphere of Mars due to the presence of interstitial gases. Alternative thermal insulation means have been subjected to preliminary evaluation by NASA to attempt to identify a material that will meet the target conductivity of 0.005 W/m-K. This study analyzes numerically the thermal conductivity performance for three of these candidate insulating fiber materials in terms of various denier (size), interstitial void fractions, interstitial void media, and orientations to the applied temperature gradient to evaluate their applicability for the new Mars suit insulation. The results demonstrate that the best conductive insulation is achieved for a high-void-fraction configuration with a grooved fiber cross section, aerogel void medium, and the fibers oriented normal to the heat flux vector. However, this configuration still exceeds the target thermal conductivity by a factor of 1.5.
Highly elastic graphene oxide–epoxy composite aerogels via simple freeze-drying and subsequent routine curing
In this study, highly elastic graphene oxide–epoxy composite aerogel (GEA) was fabricated by a facile method, in which the mixed suspension of the thermoset epoxy precursors and graphene oxide sheets was freeze-dried, followed by a routine curing process. The resulting GEA with a three-dimensional network structure not only exhibits a high decomposition temperature (286 °C), excellent mechanical strength (0.231 MPa) and extremely low density (0.09 g cm−3), but also achieves high elasticity, as it recovers from a large compressive strain without significant permanent deformation. The exceptional properties of our obtained GEA provide the potential for a range of practical applications in energy-absorbing and durable insulation materials, and the convenient synthetic approach could also be utilized in the fabrication of other organic–inorganic composite aerogels with outstanding mechanical properties.
Effective thermal conductivity of fibrous insulations
This paper addresses the applicability of the heat-transfer model proposed by the authors in a previous paper was examined by comparing the theoretical values of the effective thermal conductivity with experimental values for two types of fibrous insulations, one formed in bulk (fiber orientation is isotropic) and the other in blanket (fiber orientation is random in planes). The model equations satisfactorily explained the experimental results for both insulations at room temperature under various experimental conditions in which both the air pressure and packed density were varied.