The objective of the current study is to combine modeling and experimental efforts in fracture mechanics analysis to investigate causal phenomenon behind well-documented toughening effects in nanoparticulate reinforced polymers. Both modeling and experimental techniques are designed to operate on the micro and nano scales of active mechanisms which contribute to fracture property differences. The Extended Finite Element Method (XFEM) advanced fracture analysis technique has been employed. This node enrichment scheme for investigation of arbitrary-path crack propagation enables modeling of tortuous crack propagation with no required pre-knowledge of crack paths or locations. To overcome limitations of this method in investigation of inhomogeneous materials, cohesive interfacial elements have further been introduced, independent of the XFEM enriched domain. This overcomes arbitrary crack arrest issues at material interfaces and improves the critical consideration of the interface between reinforcing particles and the bonding polymer matrix phase with dedicated material properties and interphase treatment. A third method involving element deletion with a refined mesh has also been employed. Polycarbonate with silica inclusions has been computationally investigated. Fracture property assessment using the computational results has been performed. A parallel effort involving nano-scale experimentation under SEM observation has been designed to employ Mode I and Mode II fracture specimens prepared for direct observation of crack growth in a nanoparticulate-reinforced epoxy system.