M.S. Thesis Presentation by Benjamin Findley
Friday, August 16, 2002

(Dr. W.S. Johnson, advisor)

"Permeability of Impacted Coated Composite Laminates"

Abstract

Future generations of reusable launch vehicles (RLVs) may have composite fuel feedlines in order to help reduce the weight of the vehicle. A great deal of concern exists about low energy impact events during which the composite may suffer sufficient damage for fuel permeation to result. Thus, a series of coating materials were investigated to see how effectively they improve the impact resistance of the composite. Additionally, some of the sample feedlines produced have been found to have leaks prior to any impacts whatsoever, so it is vital to determine if coatings can be used to repair the leaking composite. Specimens with both preexisting leaks and without leaks were coated and then impacted using a drop weight impact machine and then tested for leaks using a leak detection apparatus designed in house. Those specimens that were found to have leaks were then subsequently tested to quantify the rate of permeation. Because cryogenic feedlines will experience a wide range of service temperatures, thermal cycling of the coated specimens was also performed ranging from 77K (-321 oF) to 250 oF. The effects of aging the coatings were also considered as part of this research.