To understand the relationship between fragmentation and energy dissipation in copper-bearing ore rock subjected to impact loading, a split Hopkinson pressure bar (SHPB) testing apparatus was employed to study the mechanical properties and energy transfer mechanisms of copper-bearing tuff under varying impact loads. Additionally, fractal theory was used to establish the correlation between dissipated energy and rock fragmentation. Utilizing the finite discrete element method (FDEM), numerical simulations of crack propagation within the rock were conducted. The results indicate that as the incident energy increases, the distribution patterns of the transmission energy, dissipated energy and reflection energy remain consistent, which are characterized by transmission energy, dissipated energy and reflection energy decreased successively. Furthermore, significant variations in fragment size distribution are observed with changes in dissipated energy. Specifically, as dissipated energy increases from 19.52 J to 105.72 J, the average fragment size decreases from 27.98 mm to 16.94 mm, while the fractal dimension increases by 26.43%. This suggests that higher dissipated energy results in more extensive macroscopic fragmentation, an increase in the number of fragments, smaller particle sizes and enhanced uniformity. As the impact load intensifies, the time to crack initiation decreases, and the proportion of tensile cracks relative to total cracks increases. The application of the FDEM offers new insights into the fracture and failure characteristics of rocks.