Enhanced crack detection sensitivity of carbon fiber composites by carbon nanotubes directly grown on carbon fibers

The ability of highly conductive hybrid carbon–fiber/carbon nanotube loaded epoxy composites to sense matrix cracking damage in situ is demonstrated. Multi-walled carbon-nanotubes (MWCNTs) are grown perpendicular to and on the surface of a woven carbon–fiber fabric using a chemical vapor deposition process. An increase in sensitivity of resistance change under interlaminar fracture is shown through a series of double cantilever beam (DCB) tests on samples prepared with MWCNTs grown on both sides of carbon–fiber fabric lamina placed at the top and bottom surfaces of an 8-layer test panel whereas samples with MWCNTs inside the samples did not show much increase in sensitivity of resistance change compared with the baseline samples without MWCNTs. The results suggest that the addition of surface positioned hierarchical carbon-nanotube lamina on composite structures has the potential for autonomic sensing of internal matrix damage.