Length-Scale Effect on Fracture Behavior Of Nano-Composites

Abstract

It has been recently observed that addition and dispersion of a few weight percent of nanoscale particles in polymer matrix composites have reduced brittleness and microcracking of polymer matrices and improve their strain to failure and fracture toughness without incurring weight penalty. This paper aims at using molecular dynamics to study length scale effects at the nanoscale, identifying the existence of a lower bound on flaw-size that marks the transition from brittle to ductile failure in nanocomposites, thereby causing deviations from linear elastic fracture mechanics (LEFM) predictions. Crack-tip bond-order based prediction of critical far-field stress and stress intensity factor is also addressed in this work. The MD predictions are observed to deviate from LEFM predictions below a certain length-scale. This study on nanoscale fracture of crystalline (graphene) lays the foundations for the future atomistic predictions of fracture in amorphous (polymer) nanocomposite systems.