Evaluation of interfacial properties of atmospheric pressure plasma-treated CNT-phenolic composites by dual matrix fragmentation and acoustic emission tests

A novel process of atmospheric pressure plasma treatment was performed, on powdered carbon nanotube (CNT) in water, to modify reinforcing effects and interfacial adhesion in carbon fiber reinforced CNT-phenolic composites. The change in chemical functional groups, as result of the plasma-treatment, was analyzed using Fourier transform infrared (FT-IR) spectroscopy. A significant enhancement in the wettability of plasma-treated CNT was also confirmed by static contact angle measurements. The advancing contact angle indicated a change in the surface from hydrophobic to hydrophilic. The interfacial adhesion between the carbon fibers and the plasma-treated CNT-phenolic matrix also improved, as evidenced by an increase in the apparent modulus. Due to the brittle nature of the phenolic matrix, dual matrix composites (DMC) were used in a modified fragmentation test. The different microfailure modes (phenolic matrix cracking and carbon fiber breaking) were investigated by acoustic emission and electrical resistance measurements.