Low-temperature plasma treatment of carbon fibre/epoxy resin composite

To gain insight into bonded repairs, which are commonly applied to damaged composites, we herein investigate the effects of low-temperature plasma treatment on the surface properties of a carbon fibre/epoxy resin composite, revealing that this treatment enhances the bonding strength between the patch and damaged surface. Moreover, we probe the water contact angle, chemical composition, tensile-shear strength, and morphology of composite surfaces, showing that under optimal conditions, plasma treatment decreases the water contact angle from 78 degrees to 35.5 degrees, increases the surface energy by a factor of similar to 2.3, and induces the formation of surface-bound oxygen-containing groups, increasing the O/C ratio by similar to 70%. Compared to that of the untreated composite, the tensile-shear strength of the plasma-treated composite initially increases and subsequently decreases with increasing treatment time, with the maximum increase reaching 117%. Finally, the obtained experimental data allow the above-mentioned plasma treatment to be modelled by a four-stage process.