Dynamic fragmentation of granite for impact energies of 6–28 J

The dynamic fragmentation of granite at impact energies of 6–28 J is examined in this paper. Results indicate that more dense materials, or those with a higher quartz content, produce less fractured mass, and have larger dominant fragment sizes and smaller aspect ratios in their fragment probability distributions. Values of the peaks in fragment size distributions are in agreement with theoretical predictions. Examination of the fracture surfaces reveals information concerning transgranular cracking, crack bifurcation mechanisms and evidence of comminution of sub-micron K-feldspar and plagioclase fragments. Fractal dimensions of the cumulative distribution of fragment sizes were ≃2, indicating that comminution was a dominant fragmentation mechanism in these tests. Peaks in the probability distributions of sub-micron fragments on fracture surfaces reveal a limit of coherent fragments of approximately 0.60 μm for plagioclase and K-feldspar. The smallest fragments found on the surfaces were approximately 0.30 μm and this is considered to be the comminution limit for these materials.