Plasma surface treatments on carbon fibers. II. Mechanical property and interfacial shear strength

Carbon fiber are surface treated by oxygen, argon, and styrene plasma to study the effects on fiber strength and interfacial shear strength with PPS resin. Interfacial shear strength between carbon fiber and high melting temperature thermoplastic resins is successfully measured with the microbond pull-out test with the help of scanning CO₂ laser beam which solved the difficulties in preparing PPS microspheres. Tensile tests show that etching by oxygen plasma and deposition with plasma–PS increase strength of the fibers in some cases. ESCA spectra deconvolutions demonstrate that the improved interfacial strength is strongly related to the hydroxyl, ether, or aromatic groups on the surface. On the other hand, hydrocarbon segments are detrimental to the interface. Surface area and roughness have little influences on the interfacial strength of carbon fiber/PPS composites.