Mechanical Performance of Graphite- and Aramid-Reinforced Composites at Cryogenic Temperatures

Abstract

Advanced structural composites reinforced with boron, graphite, or aramid fibers have unique mechanical, thermal, and electrical properties that make them attractive alternatives for metals in many cryogenic applications. A most promising application is the structure of the central solenoid of the poloidal field system in Tokamak magnetic fusion energy (MFE) devices.¹ Depending on the flux rise time of a particular design, energy loss due to generation of eddy currents in metallic structures might place an excessive burden on the refrigeration system. Here, a replacement of the metallic structure with advanced composites could suppress eddy currents while providing strength and stiffness equal to that, of steel. The low thermal conductivity of graphite-reinforced epoxy laminates in the 77–4 K range combined with high strength and modulus suggests the possibility of fabricating more efficient thermal isolation supports than heretofore available.