Compressive strength of carbon nanotubes grown on carbon fiber reinforced epoxy matrix multi-scale hybrid composites

The characteristics of interface between fiber reinforcement and matrix have a strong influence on the properties of a composite material. Multiwalled carbon nanotubes were grown on carbon fibers by catalytic decomposition of acetylene using thermal chemical vapor deposition technique at 700 °C to modify the fiber surface. Unidirectional multi-scale composites were fabricated using these carbon nanotubes grown fibers with epoxy matrix. As the nanotubes were directly grown on the fibers they get strongly attached with the fibers thus modifying their surface condition which in turn alters the fiber/matrix interface. Modification of the fiber/matrix interface is therefore expected to change the properties of composites. The compressive strengths of these composites were measured which showed a significant enhancement of 43% and 94% in the longitudinal and transverse compressive strengths respectively as compared to composites made of carbon fibers which underwent a similar thermal cycle but without carbon nanotubes growth. The morphology of CNTs grown on carbon fibers was examined at nano-level using HRTEM which showed growth of carbon nanotubes with different morphology and diameter ranging from 5–50 nm.