Controlled RE-induced material damage experiments in DIII-D [1,2] have provided a sound empirical basis for the development of an advanced model for the thermo-mechanical response of ATJ graphite. In our previous work [3], a KORC-Geant4-COMSOL workflow was demonstrated to be capable of predicting the onset of brittle failure within one-way coupled linear thermo-elasticity and Rankine's failure theory. Here, we report on recent modelling advances [4], which enabled one-of-a-kind simulations of the final nonlinear phase that is characterized by material fragmentation and debris ejection. This is achieved by employing the Johnson-Holmquist damage model and by combining finite-element modelling with the smooth particle hydrodynamics approach in LS-DYNA. The new thermomechanical model is benchmarked against the results of the 2023 [1] and 2024 [2] DIII-D experimental campaigns. [1] E. M. Hollmann, C. Marini, D. L. Rudakov et al., Plasma Phys. Control. Fusion, 67 (2025) 035020. [2] E. M. Hollmann, D. L. Rudakov, C. Marini et al., Nucl. Fusion (accepted). [3] S. Ratynskaia, P. Tolias, T. Rizzi et al, Nucl. Fusion 65 (2025) 024002. [4] T. Rizzi, A. Kavroulakis, S. Ratynskaia et al., Nucl. Fusion (to be submitted).