Optimization of plasma treatment variables for the improvement of carbon fibres/epoxy composite performance by response surface methodology

The purpose of the current work was to investigate the effect of oxygen plasma treatment of carbon fibre on the interfacial adhesion in carbon fibre/epoxy composites. The adhesion between the carbon fibre and matrix was examined by interlaminar shear strength (ILSS). It was observed that the composites prepared from plasma treated carbon fibre had higher ILSS compared with untreated fibres. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) were employed to study the changes in the surface morphology of carbon fibres and the fracture of carbon fibre/epoxy composite before and after plasma treatment. Attenuated total reflectance Fourier transform infrared (ATR-FTIR) analysis indicated that the plasma process created hydroxyl and carboxyl groups at the surface of carbon fibres. An experimental design with the identified process parameters namely, treatment time, power and flow rate of oxygen gas was followed. Experiments were performed according to the design in order to optimize the plasma variables by response surface methodology (RSM) using Box Behnken design. A second-order polynomial model was developed to predict the ILSS of carbon fibre composites in relation with the changes in plasma parameters. The process conditions were optimized with the quadratic model and the most efficient conditions were confirmed by the empirical results.