Crystallization Mechanism in PEEK/Carbon Fiber Composites

The non-isothermal crystallization kinetics of PEEK in the presence of carbon fibers are investigated for PEEK/carbon composites made from both prepreg and commingled systems. The crystallization kinetics under non-isothermal conditions are studied over a wide range of cooling rates, varying from 0.5°C/min to 160'C/min and compared with the pure PEEK matrix resin. For the composite materials as well as for the PEEK resin, the mechanism of crystallization is found to undergo two transitions, at about 5°C/min and 40'C/min. While the presence of carbon fibers affects the temperature and the rate of crystallization of the PEEK matrix, it does not seem to alter the basic crystallization mechanisms. The results are in agreement with some reported morphological studies on PEEK/carbon composites, suggesting that the transcrystalline structure resulting from epitaxial growth of the PEEK matrix at the carbon fiber surface constitutes a small element in the global crystallinity of the PEEK matrix in the molded composite.