Interfacial characteristics and fracture toughness of electrolytically Ni-plated carbon fiber-reinforced phenolic resin matrix composites

The electrolytic plating of metallic nickel on a carbon fiber surface has b een carried out in order to improve the interfacial adhesion and the mechan ical properties in carbon fiber/phenolic matrix composite systems. The surf ace and the mechanical interfacial properties of composites are characteriz ed by X-ray photoelectron spectrometry (XPS), surface free energy, and the critical stress intensity factor (K-IC). From the experimental results, it is clearly revealed that the oxygen functional groups and the metallic nick el on fibers largely affect the mechanical interfacial behavior of the comp osites, resulting in increased surface polarity, whereas the nitrogen funct ional groups have no effect. Also, a good correlation between surface oxyge n functional groups and mechanical interfacial properties and between wetta bility and K-IC is established and it is found that a 10 A m(-2) current de nsity is the optimum condition for this system. (C) 2001 Academic Press.