Study Of Armos Fiber Surface Modification And Composite Interfacial Properties

In this paper,one kind of novel thermoplastic resin with excellent thermal resistance and solubility-Poly(phthalazinone ether sulfone ketone)(PPESK) and Armos fiber were chosen as the matrix and the reinforcement of advance thermoplastic composites,respectively.Oxygen cold plasma treatment was applied to modify the Armos fiber surface.Different treatment time and discharge power were chosen during plasma treating process.The changes of Armos fiber surface topography were observed by scanning electron microscopy(SEM) and surface roughness was determined by atomic force microscopy(AFM).The changes of surface chemical composition of Armos fibers were characterized by X-ray photoelectron spectroscopy(XPS).Fiber wettability was analyzed by dynamic contact analysis system (DCAA).Results showed that oxygen plasma can introduce a large number of oxygencontaining functional groups onto the fiber surface,which may increase the polarity of fiber surface;In addition,it also has the etching effect on the surface.With increasing plasma-treated time and discharged power,surface morphology changed significantly,and surface roughness increased,however,excessive plasma treatment(long time or over-high power) will make the fiber surfaces melting or peeled off,caused the serious damage of the fiber bulk and decrease of surface roughness.Meantime,the surface energy analyzed by DCAA tests increased firstly and then decreased,reaching the maximum when the plasma condition is set at 10min,200W.The composite interfacial adhesion property was evaluated by interlaminar shear strength(ILSS),and indirectly illustrated by the water absorption measurements and composite fracture mechanism was analyzed by the morphology of interlaminar shear ruptures of composite observed by SEM.Due to the increase of polar groups,roughness and surface energy of Armos fiber sur- face,the interracial adhesion between the fiber and the matrix was enhanced,and the ILSS value increased from 59.5MPa(untreated) to 68.8MPa (treated at 10min,200 W),with an increase of 15.6%.Composite fractured SEM photographs confirmed that the primary failure mode of composites varied from interface failure to matrix failure after oxygen plasma treatment with improvement of interfacial bond strength between fiber and matrix.The water absorption of composite decreased after plasma treatment also indirectly showed that oxygen plasma treatment improved the interfacial adhesion. The effects of plasma treatment with different process parameters on Armos fiber surface and composite interfacial properties were significant.The plasma aging effect was evaluated by the changes of Armos fiber surface characteristics and composite interfacial properties as a function of the storage time in air.It was found that the plasma-treatment effect was greatly reduced with prolonging the aging time.So,the effective way of avoiding the aging effect is preparing the composite as soon as possible.