Dielectric Non-Destructive Analysis of Adhesive Bonded Structures
Abstract
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.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 28, 2004
- Accession Number
- ADA426943
Entities
People
- Jovan Mijovic