Extreme anisotropy of graphite and single-walled carbon nanotube bundles

The anisotropic elastic properties of hexagonal crystals are examined in this letter. It is found that graphite possesses extreme properties with the highest anisotropy degree and the lowest shear modulus to Young’s modulus ratio compared with all other known hexagonal crystals. Further, single-walled carbon nanotube (SWNT) bundles, as a kind of hexagonal material, have higher anisotropy degree and lower modulus ratio than those of graphite. These extreme mechanical properties of graphite and SWNT bundles promise great application potentials in composites, sensors, and functional materials.