What is the structure of carbon fiber? Wikipedia doesn't give much insight.
The atomic structure of carbon fiber is similar to that of graphite, consisting of sheets of carbon atoms (graphene sheets) arranged in a regular hexagonal pattern, the difference being in the way these sheets interlock. Graphite is a crystalline material in which the sheets are stacked parallel to one another in regular fashion. The intermolecular forces between the sheets are relatively weak Van der Waals forces, giving graphite its soft and brittle characteristics.
The Wikipedia description begs the question of how exactly are the sheets of graphene interlocked. Are there pi-stacking interactions?