Influence of surface treatment of carbon fibers on interfacial adhesion strength and mechanical properties of PLA-based composites

In the present study C/PLA composites with different fiber surface conditio ns (untreated and with nitric acid oxidation for 4 h and 8 h) were prepared to determine the influence of surface treatment on the interfacial adhesio n strength and mechanical properties of the composites. A chemical reaction at the fiber-matrix interfaces was confirmed by XPS studies. Nitric acid t reatment was found to improve the amount of oxygen-containing functional gr oups (particularly the carboxylic group, -COOH) on carbon fiber surfaces an d to increase the surface roughness because of the formation of longitudina l crevices. The treated composites exhibited stronger interface adhesion an d better mechanical properties in comparison to their untreated counterpart s. There was a greater percentage of improvement in interfacial adhesion st rength than in the mechanical properties. The strengthened interfaces and i mproved mechanical performance have been mainly attributed to the greater e xtent of the chemical reaction between the PLA matrix and the carbon fibers . The increased surface rough ness also has had a slight contribution. (C) 2001 John Wiley & Sons, Inc.