Seminars

The overarching objective of this seminar is to investigate the validity of application of continuum-based linear elastic fracture mechanics (LEFM) methodology, which is often employed by researchers to model fracture processes at the “discrete” atomic scale. The potential sources of error in the application of LEFM at the nanoscale are: (a) Length-scale effects, (b) non-local effects due to long range inter-atomic forces, and (c) entropic effects due to random thermal motion of atoms.
The first material selected for this study is crystalline monolayer graphene, primarily because extensive data, both experimental and analytical, already exist for this material in the literature for model validation. Furthermore, the atomistic J-integral is implemented as a nano-scale fracture metric to investigate flaw-tolerance at the nanoscale reported by many researchers, and to develop a methodology to actually predict the initiation fracture toughness of the material.
The second material system used in this study is amorphous carbon reinforced with graphene platelets (GNP). This is because it is now well documented in the literature that the inclusion of nanoparticles, such GNP in matrix materials, has resulted in significantly improved fracture toughness in mode I and mixed-mode. One of the mechanisms postulated to increase the effective crack initiation fracture toughness is the crack tip shielding effect due to nanoparticles in the fracture process zone. The effect of GNPs on the shielding of the crack tip, with varying orientation and location relative to the crack is investigated using detailed virial stress plots, the atomistic J-integral, and deviations from linear elastic fracture mechanics based (LEFM) results are presented and discussed.