Dielectric Non-Destructive Analysis of Adhesive Bonded Structures
Final rept. 1 Apr 2001-30 Jun 2004
POLYTECHNIC UNIV BROOKLYN NY
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An investigation was conducted aimed at developing dielectric spectroscopy as a non-destructive inspection tool to assess aging of adhesive bonded structures. Dielectric spectroscopy was found to be a sensitive tool capable of detecting defects and absorbed moisture in adhesive bonded structures. The highlights of the research performed are l The defects in adhesive joints decrease the real and imaginary dielectric permittivity in the frequency domain and induce additional peaks in the time domain spectra 2 The dielectric spectra of dry epoxy-amine networks are characterized by two Arrhenius-like local relaxations the beta process, associated with hydroxyl groups and the gamma process, associated with primary and secondary amine, and glycidyl ether groups 3 Dynamics of beta and gamma processes are affected by short time aging. New relaxation processes appear in both model and commercial epoxy-amine adhesives after long term exposure to moisture. 4 Time domain reflectometry TDR traces shift to longer time with water ingress in the early stages of aging, but this trend is reversed at some critical time, which is possibly a signature of disbonding.
- Adhesives, Seals and Binders
- Atomic and Molecular Physics and Spectroscopy