Atmospheric Pressure Plasma Surface Modification Of Carbom Fibers And Numerical Simulation Of The Discharge

Atmospheric pressure plasma is booming in decades. Recently, much attention has been paid to atmospheric pressure plasma for its not requiring a vacuum, energy conservation and environmental protection. Especially in the material surface modification, atmospheric pressure plasma can make material surface rough, and introduce hydrophilic functionalities such as—OH,-C=O, etc. It can increase the surface energy of the materials. The modified surface shows good wettability and bondability.Carbon fiber and its composites have been widely used in aerospace, weapon manufacture, automobile parts and many other fields, because of its high strength, high modulus and excellent fatigue performance. Carbon fibers without any surface treatment can limit the composites' properties due to the low surface energy. In this work, we study the surface characteristics of carbon fibers modifield by atmospheric pressure plasma and the discharge physics by numerical simulation.The continuous coaxial atmospheric pressure dielectric barrier discharge plasma system (PLA-PLA) was used to research the discharge under different applied power and gas composition. Electrical and optical characterizations of plasma have been analysis firstly. The plasma discharge current-voltage characteristics and discharge images show that the discharge is mainly composed of a number of filament discharge. As increased of applied power, the discharge filaments tend to focus on. From the emission spectrum, the optical emission intensities is proportional with the power supply at wavelengths of 309 nm,763nm and 777 nm, as representation of dominating species of OH, Ar and O in discharge respectively. But the emission spectrum intensities will be reduced when increasing oxygen.Then the PLA-PLA system was applied to modify the PAN-based carbon fibers. The influence of the processing parameters on the surface of carbon fibers was investigated with respect to gas flow ratio, applied power and treatment time. The surface morphologies of carbon fibers before/after plasma processing were determined by scanning electron microscope (SEM), and the surface chemical composition of the fabric samples was analyzed by Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). The contact angle and tensile strength of the carbon fibers were also tested to investigate their wettability and mechanical properties. The results indicated that as the increase of the applied power and treatment time, more and more oxygen polar functional groups were introduced into the carbon fibers surface and at the same time the surface of carbon fibers appears a lot of tiny pit by plasma etching effect. The oxygen/argon mixture gas has more effect of modified carbon fibers surface. However, for a longer treatment time, strength of carbon fibers was decreased gradually. So we must control the treatment time of the plasma to prevent carbon fibers from being damaged.In this work, one-dimensional model was developed to simulate atmospheric pressure argon plasma. The results show that the electron density increased when the discharge frequency raise. The calculated and experimented results indicate that the etching effects of atmospheric pressure plasma to the carbon fibers surface are mainly caused by the high energy electron impact.