Search

Linerless composite tanks, using continuous-graphite-fiber reinforcement and a polymeric-resin matrix will enable significant mass savings and increased payload capacity in future launch vehicles. The critical application for which linerless composite tanks show the greatest impact to system performance is in the upper stages of future expendable launch vehicles. Many of these tanks will operate at cryogenic temperatures. The key technical challenge in developing these tanks will be to choose and/or design the material to resist microcracks that may lead to leakage. Microcracks are known to form in the matrix of a composite due to thermal and mechanical stresses transverse to the reinforcing fiber direction. The toughness of the matrix material has the most pronounced impact of all factors on microcracking. This paper presents an approach for characterizing a resin’s “microcracking fracture toughness,” or the resistance of the resin to form microcracks, at cryogenic temperatures. It describes an effort to develop new, toughened materials for linerless composite tanks, a unique testing methodology for determining the microcracking fracture toughness of the materials at cryogenic temperatures, and some preliminary test results. The performance of some new toughened composite materials is compared to that of industry-standard materials used traditionally in cryogenic tanks. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR] more...

Future magnet designs for fusion devices and particle accelerators will require cost-effective, radiation-resistant materials. The use of hybrid inorganic/organic composite insulation systems will improve the lifetime, reliability, and performance of these systems. Previously, Composite Technology Development, Inc. (CTD) developed a highly-radiation-resistant, hybrid inorganic/organic insulation system, CTD-1012PX, which can be co-processed with the magnet’s Nb3Sn superconductor. This process allows the coil to be wound and insulated prior to heat treatment. However, the cost of the CTD-1012PX insulation system is generally higher than organic insulations due to the higher prices of the ceramic fibers and ceramic-matrix precursor materials. Recently, CTD demonstrated the potential for significantly reducing the cost of hybrid ceramic/organic insulation through the development of a lower-cost inorganic-matrix system and the use of lower-cost reinforcement fibers. Without accounting for the cost of a yet-to-be-developed fiber/matrix interface material, the new insulation system costs approximately 16 percent of the currently used CTD-1012PX system. This paper summarizes an on-going effort to develop this new low-cost, hybrid inorganic/organic insulation system. The options evaluated for cost reduction, as well as mechanical test results showing the effects of these changes on the properties of the insulation system, are presented.. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR] more...