Effect of CNT orientation on the mechanical property and fracture mechanism of vertically aligned carbon nanotube/carbon composites

The effect of carbon nanotube (CNT) orientation on the mechanical properties and fracture mechanisms of a vertically aligned CNT/C composite was studied in this work by a combination of nanoindentation and micropillar compression techniques. The results suggest stronger response of the composite when loading parallel to the CNT orientation. This led to higher Young's modulus and hardness (approximate to 34 GPa and approximate to 3.75 GPa) at this direction than those at perpendicular direction (approximate to 19 GPa and approximate to 2.6 GPa). The mechanical anisotropy led to fracture mechanisms that were also dependent on the CNT orientation. At 0 degrees direction, the composite was fractured into segments by splitting of the micropillar. While at 90 degrees direction, the composite was much brittle and was fractured by dual shearing, implying a strong CNT/C interface.