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 ...
Molecular aspects of chemical and physical changes in adhesively bonded joints caused by absorbed moisture were investigated. The focus was on the pre-damage stage that precedes the formation of voids and microcracks. Dielectric relaxation spectroscopy was used as a non-destructive tool to characterize he molecular level changes in the adhesive when exposed to hygrothermal environments. Three adhesive types, a commercial epoxy-amine formulation (FM73U), a model epoxy formulation consisting of diglycidyl ...
This is the final report on AFOSR #F49620-93-1-0603 entitled: "Fiber Optic Infrared Spectroscopy for "Smart" Processing". The report is divided into six sections. An Introductory paragraph contains a brief description of the background and the objectives. In-situ real time monitoring of chemical and physical changes during processing of reactive materials, polymer-forming and non polymer-forming alike, is of crucial importance to scientists and engineers engaged in efforts to optimize processes and ...
The fundamental concepts of dielectric behavior of polymers and the utilization of dielectric measurements for in situ monitoring of cure of polymers and composites are discussed. information is presented on currently used dielectric sensors and the procedure for calculation of dielectric parameters from the monitored signal. the review is written to accommodate both the fundamental and the pragmatic aspects of dielectric monitoring cure in the final part of the review, ...
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