Electrical Behavior of Carbon Fiber/Phenolic Composite during Pyrolysis

Carbon fiber reinforced carbon (CFRC) composites, also called carbon/carbon (C/C) composites are materials with superior characteristics such as low density, good thermal shock resistance, high strength and low ablation under severe environments. Due to their properties, CFRC composites are ideal candidate in the high temperature fields. By pyrolysis process, carbon fiber phenolic resin composites are converted in C/C composites. The phenolic resin is a non-conductor (electrical resistivity of 10¹²Ω.m) and during heat treatment of carbon fiber phenolic resin composite, it is converted to a carbon matrix (a conductor). This conversion was accomplished by electrical resistivity measurements using four-probe method according to ASTM C611-98 with final electrical resistivity of 0.04 mΩ.m. Microstructure of carbon fiber phenolic resin composite was assessed by using optical microscopy and image analysis. Pore volume was evaluated and the results were compared with thermal gravimetric analyses. The values of activation energy (Ea) during pyrolysis were 1.153kJ.mol^–1 and 10.860kJ.mol^–1.

Keywords:
carbon carbon composites; pyrolysis; phenolic resin; electrical resistivity; four-probe method; activation energy