Influence of Environmental Temperature on Fatigue Reliability at Elevated Temperature for Carbon-Fiber-Reinforced PEEK : On the Growth Mechanism from Mesocracks to Macrocracks

Abstract

In this paper, the influence of environmental temperature on fatigue reliability for advanced carbon-fiber-reinforced-thermal-plastic PEEK was examined. Attention was focused on the mechanism of growth from mesocracks to macrocracks at elevated temperature. The main results were as follows, (1)The fatigue life at elevated temperature was arranged by the fatigue strength of CF15 and gf30 materials decreased with increasing environmental temperature. Further, the strength of CF15 material was superior to that of gf30 material. (2)The influence of stress and environmental temperature was represented by the N_f -1/T diagram and S-T(C+log t_r)diagram. Therefore, it was suggested that high-cycle fatigue life could be estimated from these parameters. (3)From the results of fractography using SEM, the fracture surface of CF15 material was ductile, on the other hand, that of gf30 material was brittle. (4)It was appeared that the temperature rise in the fatigue damage zone was closely related to the mesocrack formation process. (5)It was thought that the difference of mesocrack formation between CF15 material and gf30 material was reflected in the difference of the activation energy.