Electrophoretic deposition of carbon nanotubes onto carbon fiber felt for production of carbon/carbon composites with improved mechanical and thermal properties

• CNTs had complicated effect on microstructure of pyrocarbon in CNT-C/C composites.
• Compressive strength and modulus of CNT-C/C composites were increased by 37% and 19%.
• CTE of CNT-C/C composites in Z direction was decreased by 30%.

Carbon nanotubes (CNTs) were introduced into carbon fiber felts by electrophoretic deposition (EPD) and then pyrocarbon (PyC) was infiltrated in the felts by thermal gradient chemical vapor infiltration using methane as precursor to prepare carbon nanotube (CNT) reinforced carbon/carbon composites (CNT-C/C composites). The effects of CNTs by EPD on microstructure, mechanical and thermal properties of carbon/carbon (C/C) composites were investigated. Results showed that CNTs had complicated effects on the microstructure of PyC in CNT-C/C composites: PyC next to carbon fiber (CF) was isotropic texture and PyC far from CF showed medium texture, while PyC in C/C composites without CNTs (REF-C/C composites) presented low texture. Compared with REF-C/C composites, compressive strength and modulus of CNT-C/C composites were increased by 37% and 19%, respectively, and fracture mode of the composites changed from pseudo-plastic fracture to brittle fracture; coefficient of thermal expansion of CNT-C/C composites in the direction perpendicular to carbon fiber plies was decreased by 30%.