  Dust coagulation in protoplanetary disks is not straightforward and is
subject to several slow-down mechanisms, such as bouncing, fragmentation and
radial drift to the star. Furthermore, dust grains in UV-shielded disk regions
are negatively charged due to collisions with the surrounding electrons and
ions, which leads to their electrostatic repulsion. For typical disk
conditions, the relative velocities between micron-size grains are small and
their collisions are strongly affected by the repulsion. On the other hand,
collisions between pebble-size grains can be too energetic, leading to grain
fragmentation. The aim of the present paper is to study a combined effect of
the electrostatic and fragmentation barriers on dust evolution. We numerically
solve the Smoluchowski coagulation-fragmentation equation for grains whose
charging occurs under conditions typical for the inner disk regions, where
thermal ionization operates. We find that dust fragmentation efficiently
resupplies the population of small grains under the electrostatic barrier. As a
result, the equilibrium abundance of sub-micron grains is enhanced by several
orders of magnitude compared to the case of neutral dust. For some conditions
with fragmentation velocities $\sim 1$ m s$^{-1}$, macroscopic grains are
completely destroyed.
