Temperature-variable Raman scattering study on micromechanical properties of the carbon fiber reinforced polyimide composite film

Temperature-variable Raman spectroscopy equipped with mapping function was used to investigate the micro-mechanical properties of a carbon fiber (CF) reinforced polyimide(PI)composite film using carbon nanotubes (3 wt%) dispersed in PI as the stress sensor. The stress distributions on CFs and the interface region during heating from 25 to 300℃ were mapped based on the stress sensitive Raman G' band (around 2679 cm^-1) shifts of CNTs. Results indicate that thermal motion of PI chain affect the mechanical properties when the CF/CNT-PI film was heated up to 300℃. Both CFs and interface region were compressively stressed below 200℃. The compressive stress decreased with temperature and was approximately eliminated at around 200℃. Tensile stress developed above 200℃ and increased with temperature, which was distributed mainly on CFs. Furthermore, the stress transfer between CFs and matrix was less than 100% due to the thermal stress hysteresis in the PI matrix.