Increasing mechanical strength retention rate of carbon/carbon composites after graphitization by grafting straight carbon nanotubes radially onto carbon fibers

Straight carbon nanotubes (CNTs) were grafted radially onto carbon fibers and they were used to enhance mechanical strength retention rate (i.e. the percentage of mechanical strength after graphitization as that before graphitization) of laminated carbon/carbon (C/C) composites after graphitization. Results show that out-of-plane compression strength and interlaminar shear strength retention rates of C/C composites increase from 34.7% and 42.1% to 76.2% and 84.9% after adding CNTs, showing 120% and 102% improvements. Analyses demonstrate that these great improvements are the result of simultaneous reinforcements to the fiber/matrix (F/M) interface and the matrix provided by the radially grafted CNTs, which can effectively inhibit the microstructure defects such as F/M interface debonding and matrix annular cracking occurred around carbon fiber during graphitization and then greatly increase the mechanical strength of graphitized C/C composites.