Preparation And Properties Of Continuous Carbon Fiber Reinforced Poly(Ether Ether Ketone) Composites

The matrix material of a composite can be mainly classified into two categories:thermoset resins and thermoplastic resins. Thermoplastic composites usually havemany advantages over thermoset composites. The molecule chain of thermoplastic istypically linear with high toughness and good impact resistance. Besides, thermoplasticresin can be characterized by low moisture absorption, resistance to high temperature,short molding cycle and suitable for mass production. Polyether ether ketone (PEEK),as a representative of high performance semi-crystalline thermoplastic resin, hasexcellent mechanical properties, moisture and heat resistance and corrosion resistance.PEEK has been widely used in aerospace, electronic information, energy and medicalfields. However, due to the high melt viscosity of PEEK and almost insoluble in anysolvent, short carbon fiber reinforced PEEK composites dominate the PEEKcomposites. Continuous carbon fiber reinforced PEEK composites with high strengthand modulus have a greater potential in many ways. This thesis focuses on thefabrication of continuous carbon fiber reinforced PEEK composites.Virtually, the high viscosity and excellent solvent resistance of PEEK make it hardto impregnate into the carbon fibers. To overcome the problem, hybrid yarns wereprepared by cowrap method using the self-made PEEK fibers in our laboratory andcarbon fibers. Unidirectional plain cloth was knitted to facilitate post-hot press moldingusing hybrid yarns as warp fibers and neat PEEK fibers as weft fibers. The plain fabricswere stacked and then hot pressed to prepare the continuous carbon fiber reinforcedPEEK composites. Due to the crimp nature of cowrapped yarn, unidirectional plainfabric was pre-pressed under certain tension to fix the orientation of carbon fibers.Molding pressure, holding time and molding temperature were optimized during themolding process. Unidirectional continuous carbon fiber reinforced PEEK composites with excellent mechanical properties were successfully fabricated. The results showedthat PEEK fibers and carbon fibers did not distribute homogeneously in the hybrid yarns,and therefore large molding pressure and high molding temperature was adopted topromote the impregnation effects. At higher molding temperature, PEEK experienceda small amount of thermal oxidative degradation and caused slight decrease in thermalstability. At the same time, high temperature also resulted in the decrease of meltviscosity of PEEK. And the decrease of melt viscosity of PEEK promoted theimpregnation of PEEK resin into carbon fibers and dictated the excellent mechanicalproperties of the composites.The correlative properties of the composites prepared with optimization conditionswere evaluated. Specially, humidity and heat resistant performance was discussed in-depth. The results showed that the composites had outstanding mechanical propertiesand excellent high temperature performance. The composites could still maintain highmechanical properties after being placed at a humid environment both at roomtemperature and high temperature.