SBIR-STTR Award

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 alloy pipe. 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 was first 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 integrity and 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 engine cryopipe in a cyclical, cryogenic environment. Design software will facilitate insertion for Phase III flight tests. Anticipated Benefits/Commercial Applications: 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 and oil/gas fields ($300,000 commitment.)

Keywords:
cryopipe, prestress, micro-cracking , composites, delamination, rockets, lines and ducts

This stress-profiling research is an important component for weight savings on the MDA funded Airborne Laser. Both deployable and airborne systems are candidates. The objectives are to cut piping weight and cost by half. Prestressed composite cryogenic piping (US Patent 6,325,108) adds a layer of circumferential prestress to cured PMC pipe. Prestress induces compression in the interior surface to prevent delamination and tension micro cracks. This was observed as a byproduct of prior cryogenic testing and further demonstrated in Phase I. 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 and chemical attack, prestress is the key to structural integrity and longevity. Beyond the patented cryopipe this proposal includes supportive innovations in high compression, low creep, chemically resistant and low permeable polymers. Phase II will model, fabricate, cure, prestress and comparatively test cylindrical composite sections in antagonistic chemical and cyclical cryogenic environments. Both commercial and aerospace qualified materials will be used. A foil liner system will be studied. Design software will provide structured accessibility to the stress-profiling technique and facilitate technology transfer for Phase III flight tests.

Keywords:
Cryopipe, Micro-Cracking, Delamination, Airborne Laser, Prestress, Composites, Chemical Compatibility, Weight Savings