Thermal Expansion Coefficients of Unidirectional Carbon Fiber/PEEK Composite Made of Commingled Yarns

Abstract

Unidirectional carbon fiber (CF)/poly(ether‐ether‐ketone) (PEEK) composite was manufactured from the commingled yarns composed of CF and PEEK filaments (this composite is named ‘‘commingled composite’’). The thermal expansion coefficient (TEC) of the commingled composite was measured and compared with that of CF/PEEK unidirectional composite made of prepreg sheets (this composite is named ‘‘prepreg composite’’). The minimum value of TEC’s parallel to the fiber direction was observed at around 150 °C for both specimens which were not thermally treated. This minimum disappeared after the thermal treatment at 230 °C for 30 min or the repeating measurements (0 °C→230 °C, 0 °C→230 °C,...). While the TEC of the prepreg composite was almost independent of temperature, that of the commingled composite showed a remarkable decrease at temperatures above the glass transition temperature (Tg) of PEEK. This could be interpreted in terms of the orientation distribution of carbon fibers in the commingled composite. The ...