Prestressed Cryopipe for Rocket Engine Lines/Ducts

"This research strikes at two barriers to using polymer matrix composites (PMC) for rocket lines and ducts, (1) delamination and (2) tension micro cracks. The objectives are to cut both launch weight and cost by half by replacing heavy, expensive alloypipe.Prestressed composite cryogenic piping (US Patent 6,325,108 issued 4Dec01) adds a layer of circumferential prestress to cured PMC pipe. Prestress induces a compression that eliminates the tension stresses that cause micro cracks and delamination. This wasfirst observed as a byproduct of cryogenic testing on BMDO00-013 Phase I in November of 2000 for Dynamic Polymer Composite (DPC) connectors.Most polymers exhibit increased stiffness at cryogenic temperatures. Stiffness limits the polymer's ability to distribute loads to the high-modulus fibers. For composites experiencing multiple thermal shocks, prestress is the key to structural integrityand longevity.Phase I will model, fabricate, cure, prestress and comparatively test cylindrical composite lines in a cryogenic environment. A foil liner system will be studied. Using aerospace qualified materials, Phase II will develop and test prototype rocket enginecryopipe in a cyclical, cryogenic environment. Design software will facilitate insertion for Phase III flight tests. Boeing will use this research for improving their rocket engine performance. A large composite pipe producer is a commercial partner for use in cryogenic process plants