||Light-Curing Structural Tape for In-Space Repair
||Proc. 2007 SAMPE Fall Tech. Conf. and Exhib.
||Allred, R. E.; Hoyt Haight, A. E.; Wesley, T.
||This program was undertaken to prove the feasibility of using light-curing fiberglass tape for in-space repairs. Substrates were limited to aluminum and carbon/epoxy composites and surface preparation to sanding and alcohol wipes. A 380 nm UV wavelength, which is available in high power LEDs, was chosen for curing. Formulations of cationic epoxy and free radical epoxy acrylate resins and hybrids of both were successfully cured as tapes using UV LEDs. A sensitizer was identified for the cationic epoxies that preferentially absorbed at 380 nm, thereby allowing these systems to be cured with LED illumination. Methods for adducting the epoxies were developed for viscosity control. The hybrid resin systems offer advantages in that they attain rapid strength buildup through the acrylate resin and adhesion and longer term strength from the epoxy phase. Poly (ethylene terephthalate) backing films were shown to pass the needed 380 nm light and, with corona treatment, adhere to the cured tape. The backing film is needed for the tape in the dispenser to prevent the tape from sticking to itself. By bonding into the repair patch, the backing film does not create a disposal problem. A prototype tape dispenser based on a design similar to a 35-mm film canister was fabricated and confirmed the validity of that concept for further development. Peel tests confirmed generally good adhesion to aluminum substrates. Finally, numerous demonstrations of repairs were made, including bonding pipes of various materials together, patching burst pipes, and patching punctures. A one inch patch over a half inch diameter hole was pressurized to 120 psi without failure or delamination. Overall, the demonstration repairs showed the versatility and utility of the “structural duct tape” concept for in-space repair.
||repair technology, rigidization, UV cure, UV LED cure, rapid cure resin, light-curing resin, sensitizer, structural repair tape, in-space repair