Abstract
Testing was carried out to characterize and predict the long-term thermomechanical properties of various thermal insulation materials for use in nuclear-based space power systems. In particular, the high temperature compressive strength and stress relaxation behavior of these materials under vacuum or an inert atmosphere and up to 950°C were evaluated under either isothermal conditions or under various thermal gradients for test times of over two years. Several tests subjected to thermal gradient conditions were also evaluated for changes in strain due to cooling or heating events. Other testing of these materials included evaluation of their response to lateral (as opposed to axial) loads, their response to triaxial loading conditions, thermal shock behavior of these materials, and shrinkage effects in these materials due to elevated temperature exposure. Additionally, finite element and mathematical models were formulated to predict the mechanical behavior exhibited by these materials out to 35,000 hours (4 years) based on this testing. This paper will summarize the design and construction of unique test equipment to carry out this testing, along with the results of the testing and the subsequent modeling.
