The Influence Of The Ectrochemical Grafting On Interfacial Properties Of Carbon Fiber Composites

The excellent mechanical properties of carbon fiber composites benefit from its good interface structure.When the composites are affected by external loads,the interface plays an important role in transmitting loads.With the continuous improvement of the requirements for the comprehensive performance and the compression properties of carbon fiber composites,higher requirements have been put on the interface structure and performance of composite.The hydrophobicity and chemical inertness of the carbon fiber surface lead to the weak bonding strength between fiber and resin in carbon fiber resin-based composites,which affects the performance of isotropic properties and compression performance of fiber-reinforced composites.Therefore,improving the interfacial properties of carbon fiber composites by modifying the surface properties of carbon fibers is an important way to improve the comprehensive performance of carbon fiber reinforced resin-based composites.In this paper,glyceryl methacrylate(GMA)was grafted onto the surface of carbon fibers by electrochemical grafting to form a graft polymer(PGMA)to improve the interfacial properties of carbon fiber composites.Firstly,the electrochemical grafting reaction of GMA monomer on the surface of carbon fiber was studied.The connection state of carbon fiber and GMA after electrochemical grafting and the optimal electrolyte required for electrochemical grafting were analyzed.Then the effects of different grafting conditions(electrolyte concentration,current intensity and reaction time)on the electrochemical graft polymerization of GMA on the surface of carbon fibers were explored.At the same time,the effects of diferent chemical structures on the fiber surface on the electrochemical graft polymerization of GMA were explored,including the content of different COOH oxygen-containing functional groups and the graphite structure on the fiber surface.Finally,the effect of electrochemical graft polymerization on the surface of carbon fibers on the interfacial properties of carbon fiber composites was analyzed.By investigating the electrochemical grafting experiments on the surface of carbon fibers,it was found that GMA graft polymers were formed on the surface of carbon fibers and the optimal electrolyte in the electrochemical grafting experiments was aluminum trichloride.When aluminum trichloride is used as the electrolyte,as the concentration of aluminum trichloride increases,the grafting rate of the carbon fibers surface will gradually increase and stabilize.With the increase of the current intensity,the grafting rate on the surface of the carbon fiber will increase first and then decrease.With the extension of reaction time,the grafting rate of carbon fiber surface will continue to increase,but the rising rate will gradually decrease.It was found that the grafting rate of GMA on the surface of carbon fiber will increase with the increase of COOH content.Graphite fibers with inert surfaces can only form PGMA graft polymers on the surface of the fibers after pre-anodizing to produce COOH oxygen-containing functional groups.From the experimental results,it can be inferred that the reaction mechanism of electrochemical grafting on the carbon fiber surface is divided into two steps:first,the surface of the carbon fiber will be oxidized to generate oxygen-containing functional groups,and then the COOH oxygen-containing functional group on the carbon fiber surface will first lose electrons and then remove carbon dioxide to generate carbon free Radicals,carbon radicals will attack the carbon-carbon double bonds in the GMA monomer to initiate polymerization to form the graft polymer.The dynamic contact angle test and the characterization results of interfacial shear strength proved that the interfacial properties of carbon fiber composites have improved after electrochemical grafting.