This research proposal seeks support for an investigation of the fundamental aspects of preparation, characterization and durability of adhesive joints. The proposed research will focus on the use of dielectric relaxation spectroscopy (ORS) to study the pre-damage state in adhesive joints. It is expected that ORS will furnish fundamental information about the molecular mechanisms of various chemo-physical phenomena in adhesives during exposure to aggressive environments. This will elucidate the mechanism of pre-damage in the bondline that precedes microcracking, delamination and loss of adhesion. A wide frequency range will permit a fundamental insight into the various polarization events with varying time scales. Of particular interest will be the high frequency (>1MHz) events, where dipole reorientations take place. The change in dipole dynamics will provide a nondestructive measure of the pre-damage stage. Mechanical tests will be performed on bonded joints after exposure to various thermal~mechanical-enviror~twe1 cal conditions for different times to estimate the changes in bond strength. These results will be correlated with the NDI results obtained from dielectric and infrared measurements
