Thermal and Mechanical Behavior of PAN-based Carbon Fiber/Epoxy Composite with Hexagonal Boron Nitride Particles

Abstract

This study proposes a high thermal conductivity PAN-based carbon fiber/epoxy composite with hexagonal boron nitride (hBN) particles known for their superior thermal conductivity. To disperse hBN in epoxy, hBN was added to acetone at a mass ratio of 1:15. Epoxy was then added to the mixed solution and stirred at 70℃ to evaporate the acetone. Afterward, a hardener was added to the solution, and stirred, and then the hBN-dispersed epoxy was obtained through sintering in a vacuum oven. Using this method, epoxy samples with 0 wt% (control), 10 wt%, 20 wt%, and 30 wt% hBN were prepared and the thermal and mechanical properties were compared with the hBN particle size and content. These different epoxy samples were used to lay up 8 plies of PAN-based carbon fabric (CF). The laminated plates were cured using an autoclave process with a curing cycle set to 130℃, 6 atm, for 2 hours, producing CF-hBN/Epoxy composite panels. Density, specific heat, and thermal diffusivity were determined to measure the fabricated composite specimens' thermal conductivity. Apparent density was calculated from the weight and volume of the composites, and specific heat was measured using the DSC-4000 equipment. In-plane and through-thickness thermal diffusivity were measured using the LFA-467 equipment, following ASTM E1461 standards. The thermal conductivity was derived from the specimens' measured density, specific heat, and thermal diffusivity. The thermal conductivity measurements showed that both in-plane and through-thickness thermal conductivities increased the most for the 20 wt.% hBN specimens compared to the Control. Heat transfer pathways formed through adjacent hBN particles within the epoxy, enhancing thermal conductivity up to 20 wt.%. However, at 30 wt.%, thermal conductivity decreased, indicating that increased hBN content does not linearly enhance thermal conductivity, and 30 wt.% hBN is inefficient in forming effective heat transfer pathways within the composite. This is attributed to the formation of thick hBN layers, which reduce mechanical properties. The proposed CF-hBN/epoxy composite in this study showed a maximum increase in thermal conductivity with increasing hBN content up to a critical point, beyond which the thermal conductivity decreased. The mechanical properties tended to decrease with increasing hBN content. Future work will involve dispersing hBN and metal particles in epoxy and performing a stitching process to enhance in-plane and through-thickness thermal conductivity. This research aims to develop high thermal conductivity PAN-based carbon fiber composites for thermal management applications.