Realizing the synergy of carbon nanotubes and matrix microstructure for improved flexural behavior of laminated carbon/carbon composites

Carbon nanotubes have been electrophoretically deposited on carbon fibers to improve the flexural performance of laminated carbon/carbon composites. The synergy effect between carbon nanotubes and different textured pyrocarbon matrix has been investigated. Mechanical testing results showed that after introducing nanotubes into low-texture-matrix and high-texture-matrix composites, their flexural strength increased by 13.9% (up to 197 MPa) and 89.6% (up to 309 MPa), respectively. Excessively strong interface bonding in low texture matrix C/C resulted in the deterioration of the in-situ fiber strength and the strengthening effect provided by CNTs. While the fiber-pyrocarbon interface in high-texture-matrix composites was relatively weak, the introduction of CNTs showed a better strengthening effect because of the optimization of the fiber-matrix interface. Additionally, CNTs indirectly induced the formation of protuberance structure in the layered matrix, which improved the cohesion of high texture matrix and relieved the matrix stress concentrations as confirmed by Raman stress analysis. It is clearly demonstrated that the synergy of nanotubes and high-texture matrix is a promising strategy to improve the flexural behavior of carbon/carbon composites.