  We investigate the fragmentation process of solid materials with crystalline
and amorphous phases using the discrete element method. Damage initiates inside
spherical samples above the contact zone in a region where the circumferential
stress field is tensile. Cracks initiated in this region grow to form
meridional planes. If the collision energy exceeds a critical value which
depends on the material's internal structure, cracks reach the sample surface
resulting in fragmentation. We show that this primary fragmentation mechanism
is very robust with respect to the internal structure of the material. For all
configurations, a sharp transition from the damage to the fragmentation regime
is observed, with smaller critical collision energies for crystalline samples.
The mass distribution of the fragments follows a power law for small fragments
with an exponent that is characteristic for the branching merging process of
unstable cracks. Moreover this exponent depends only on the dimensionally of
the system and not on the micro structure.
