Abstract
Atmospheric plasma treatment (APT) has been used on a number of composite systems as an effective surface preparation technique for adhesive bonding. Recently, a new class of siloxane-modified polycyanurate resin systems (TC410) has been developed for use as a matrix material in composites utilized for space applications. The effect of APT on a TC410/M55J fiber composite was evaluated. Contact angle measurements exhibited a sharp reduction in wetting angle with exposure. An increase in the polar surface energy component with treatment coincides with Fourier transform infrared and X-ray photoelectron spectroscopy (XPS) results, which verify the formation of an oxidized carbonate species formed on the composite surface. A solvent rinse removes the majority of the oxidized species and results in an increase in contact angle, due to the removal of a fine ash. XPS and energy-dispersive x-ray spectroscopy verify the distribution of a siloxane component throughout the resin, which was oxidized during APT and forms a silicate. A 24% increase in bond strength was realized after six passes in comparison to abraded specimens. Higher treatment levels resulted in a decrease in strength; however, a solvent rinse of the APT surface gave rise to some recovery in strength due to the removal of the weakly bonded interlayer.
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