Characterizing failure behavior of ductile glassy polymers

To improve the mechanical characteristics of existing and upcoming polymers, particularly sustainable polymers, we need to understand how polymers resist crack propagation.  In contrast to brittle polymers where fracture mechanics has been routinely applied to gather phenomenology, a subject addressed elsewhere by our coworker (C. Gupta), ductile polymers are more challenging to rank.   While work fracture (the area under the stress-strain curve) is effective to quantify toughness, it does not indicate how a ductile polymer deforms in presence of a crack, e.g., single-edge notch.  In this work, we apply concepts familiar fracture mechanics, e.g., stress intensification ahead of crack, and show how ductile glassy polymers shows brittle response when the combination of nominal load and crack size defines a threshold toughness.   This condition is different from one under which they respond in a ductile manner in presence of smaller cracks.  We explore this interesting phenomenon to provide new insight into what a fracture mechanical and chain-network picture of polymer deformation can provide in terms of prediction and explanation.   We will explore a potential correlation between this newly defined toughness and work of fracture.