Dielectrometer Monitored Adhesive Bonding.
Technical rept. Jun 70-Oct 71,
DAYTON UNIV OHIO RESEARCH INST
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An automatic dielectrometer is investigated as a means for monitoring the cure of a structural adhesive during an in-press bonding operation. The instrument is found to be sensitive to changes occurring within the adhesive, as indicated by relative values of the dielectric constant and the dissipation factor, during the bonding of metallic adherends. Insulation and shielding techniques are developed to obtain relatively noise-free dielectrometer traces while operating in the electrically noisy environment of a heated platen, hydraulic press. Definitive curves are obtained on both an epoxy type and a polyimide type adhesive system under a constantly increasing temperature cure cycle. These traces are used to design an experiment to determine the effect upon resultant joint strength of varying the point at which full bonding pressure is applied to polyimide adhesive bonded tensile lap shear joints. Author-PL