Control of heat-deformation properties at high temperature of carbon fiber reinforced PEEK by crystallization

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Main purpose of this research is to develop a polymeric composite having high heat resistance. Polyether-ether Keton (PEEK) is well known as super-engineering plastic and this polymer has high strength and high heat resistance on mechanical properties. CFRP of PEEK shows very high performance at high temperature condition. But this can not escape from a visco-elastic deformation. In this project, we tried to control and to decrease the creep deformation by crystallization phenomena.It was found that PEEK had minimum crystallinity 24% just after Quenching and maximum crystallinity could rise up to 42% by DSC test. Two kinds of CFRP of PEEK were prepared. They were laminates, which were quasi-isotropic material ; [0, 90, 45, -45]s and injection molded CFRP. The fiber weight factions were 60% and 20% respectively. We researched bending creep phenomena and measured creep compliance at 80 to 150℃. For CFRP laminate, two crystallinities ; 24 and 42% were prepared and the crystallinities for injection-molded CFRP were 34%, 38% and 42%. The minimum crystallinity of laminates was smaller than injection molded CFRP. Creep compliance curves on each temperature were measured and a master curve of them was drawn by shifting them to horizontal direction until completely over-lap on each other. And the amount of the shifting was plotted on an Arrhenius type figure. For all materials, shift factor made a straight line. We concluded creep deformation was obeyed by the time temperature superposition. And all material shows the linear visco-elastic deformations. And increasing crystallinity, creep deformation was decreased. Finally, from these facts, we concluded that we can control the creep deformation at high temperature by crystallization treatment.