Plasma Treatment of a Carbon/Epoxy Prepreg and Its Effect on the Durability of Carbon/Epoxy Laminated Composites

For the present study, a carbon/epoxy prepreg was plasma-treated with oxygen gas and the effect of plasma treatment on the durability of the carbon/epoxy laminated composite was investigated. In order to perform the shear and the residual strength tests, we fabricated shear and tensile fatigue specimens with either untreated prepregs or plasma-treated prepregs by stacking 8-ply prepregs unidirectionally ([0(0)](8)). X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) analyses were used to investigate the changes in the polar functional groups on normal and fractured surfaces with plasma treatment. The shear tests showed that the shear strength of the plasma-treated carbon/epoxy composites was similar to 9 % greater than that of the untreated carbon/epoxy composites. The residual strength tests showed that the residual strength decreased with increasing fatigue cycles for both specimens. However, the residual strength and the elastic modulus of the plasma-treated carbon/epoxy composites were about 5 % and 10 % greater than those of untreated carbon/epoxy composites at 100,000 cycles. The XPS analysis showed that carbonyl, carboxyl and amide functional groups were formed on the surface of the prepreg after an oxygen plasma treatment. The SEM analysis showed that more epoxy adhered to the fibers for the plasma-treated specimen than for the untreated specimen.