Graphite Is Soft in One Direction and Strong in Another, At Once
Graphite's mechanical properties depend entirely on which direction you measure, a real, extreme anisotropy that traces directly to its layered structure.
Most materials on this site have mechanical properties that, to a first approximation, are the same no matter which direction you test them. Graphite is a genuine, striking exception, a direct mechanical consequence of the layered structure covered on this material’s materials science page.
Extreme anisotropy, not a simplification
Within a graphite sheet, the strong covalent bonds give the in-plane direction real stiffness, comparable to some structural ceramics. Between sheets, the weak van der Waals bonding gives almost no resistance to shear at all, a real, measured difference of roughly two orders of magnitude between the in-plane and through-plane elastic modulus of a single graphite crystal.
Why this is useful, not just a curiosity
Graphite’s largest single use by the dashboard’s own figures, refractories and steelmaking at roughly 26%, relies on a different mechanical fact entirely: graphite tolerates extreme thermal cycling without cracking, because its thermal expansion is also highly anisotropic, and because the weak interlayer bonding lets internal stresses relieve through sheet sliding rather than building up to the point of fracture. The same softness that makes graphite a poor structural material in tension makes it an excellent one under thermal shock.
Sources: anisotropic mechanical and thermal properties draw on standard carbon materials references (ASM Handbook); production context references the demand data elsewhere on this site.