The objective of the current study is to employ precise and detailed nano-scale investigation to determine the physical mechanisms that contribute to the mechanical performance benefits of nano-particulate inclusions in polymer and polymer composite materials. A significant amount of work by the research community has experimentally illustrated the effective property benefits of nano-inclusions, thus the current work has elucidated some of the phenomenological causes behind these enhancement observations in a controlled fashion through a combination of micromechanical modeling and nano-scale experimentation under SEM observation. Nano-scale Mode I and Mode II fracture specimens have been designed to allow direct observation of crack growth in a nanoparticulate-reinforced epoxy system. Modeling employing the X-FEM node enrichment scheme for investigation of arbitrary-path crack propagation has been performed. Considerations critical to the accuracy of representation as well as the tractability of computation have been developed.