TEST DESIGN AND RESULTS OF INVESTIGATION OF THE EFFECTS OF SHORT DURATION HEAT TREATMENT OF PAN-BASED CARBON FIBERS AND DRY CARBON YARNS

摘要

With sights set on landing large masses on Mars and other bodies the need for understanding thermal protection systems (TPS) under entry trajectory conditions has increased. High temperature kinetics during planetary entry can have a major impact on the graphitization and properties of 3D woven TPS structures. This study focuses on the fiber graph itization and resulting property changes that occur when polyacrylonitrile (PAN) based carbon yarns are subjected to 2800°C (5072 °F) in inert atmosphere for various short durations. Southern Research performed the heat treatment for each fiber batch, conducted yarn electrical resistivity tests, and performed yarn tensile tests subsequent to 10, 25, and 40 second exposures. After the results of the initial exposures was examined, two shorter exposure times of 2.5 and 5 seconds were added to the data set. Testing showed that there was a near immediate property response to the temperature exposure. All properties examined - electrical resistivity, yarn tensile strength, and yarn tensile modulus -showed shifts in property at the 2.5 second mark and beyond with varying trends through the heat treat conditions.