  We study the mechanics of nematically ordered semiflexible networks showing
that they, like isotropic networks, undergo an affine to non-affine cross-over
controlled by the ratio of the filament length to the non-affinity length. Deep
in the non-affine regime, however, these anisotropic networks exhibit a much
more complex mechanical response characterized by a vanishing linear response
regime for highly ordered networks and a generically more complex dependence of
the shear modulus upon the direction of shear relative to the nematic director.
We show that these features can be understood in terms of a generalized floppy
modes analysis of the non-affine mechanics and a type of cooperative Euler
buckling.
