Fabrication And Study Of PEK-c/Carbon Fiber Composites

Carbon fiber-reinforced thermoplastic(CFRP) composites gained a lot of attention due to their good engineering properties, including high strength and stiffness combined with low density, fatigue endurance, impact resistance, damage tolerance, rapid manufacturing cycles, and recycling possibility. They are hopeful to be used as substitutes for the widely used thermosetting composites in aerospace and automobile applications. Thus far, fiber-reinforced engineering plastics, such as poly(ether ether ketone), polyimide(PI), and poly(phenylene sulfide) have been extensively researched due to their excellent mechanical properties, heat stability, and chemical resistance. However, there are few published reports on the effects of molecular weight on the properties of composites, and these works focused mostly on the effect of temperature, additional modifiers, and aging on the mechanical and thermal properties. Molecular weight is one of the most important and representative parameters of polymers; thus, its effects on the properties of thermoplastic composite cannot be ignored.In this work, in order to improve the solubility of poly(aryl ether kitone) which can’t be processed by solution, a Phenolphthalein Poly(aryl ether ketone)-- PEK-C was synthesized. CF fabric-reinforced PEK-c composites were prepared by impregnating solution-processed prepreg with resins of different molecular weights. The appropriate processing conditions were determined to obtain the appropriate fiber content and excellent composite laminates. The effects of molecular weight on the properties of CF/PEK-c composites properties were systematically investigated through DMA and ILSS. The scanning electron microscopic(SEM) images of composite laminates cross sections were also evaluated to further research on it.The experimental results indicated that the molecular weights of the prepared PEK-c resins as determined by GPC were in accordance with the designed molecular weights, indicating that the prepared PEK-c resins had the expected chemical structure and narrow molecular weight distribution. SEM images showed that uniform fiber distribution and sufficient fiber wetting were achieved. The composites were found to have excellent storage modulus; the storage modulus and Tg increased slightly with the increasing molecular weight. Similarly to the loss modulus, the tan δ also showed a lower peak value and a higher Tg value, indicating the better interfacial adhesion of composite of higher molecular weight. Furthermore, the double-peak phenomenon in tan δ curve was found to represent the glass transition and viscous state transition, respectively. The ILSS improved with increasing molecular weight, suggesting better interfacial interaction in the composite when the molecular weight is higher. In summary, based on the premise of good fabrication, composites with higher molecular weights have better thermal and mechanical properties.