Mechanism study of atmospheric-pressure plasma treatment of carbon fiber reinforced polymers for adhesion improvement

Adhesive bonding is widely employed to join structural components. To improve the load resistance of joints, atmospheric-pressure plasma surface treatments are commonly performed to increase the adhesion of the bonding layers. It is known that the surface decontamination, roughness change and surface activation induced by plasma are main factors to increase the surface free energy and improve the adhesion. In this work, a large-area and low-temperature atmospheric-pressure plasma is used to improve the adhesion between carbon fiber reinforced polymers (CFRPs). It is found that the adhesion between CFRPs measured by lap-shear strength test seems to increase by increasing the plasma power and treatment time but start to reach a limit for excessive power and long treatment time as a result of the selective ablation of the resin covering the carbon fibers. Based on physical and chemical analyses of surfaces and plasmas, the effects of plasma treatment on CFRPs are discussed.