Experimental Characterization and Fracture Behavior of Graphene Nanocomposites

Abstract

This work investigates the structural scaling of polymer/graphene nanocomposites. Fracture tests were conducted on geometrically scaled Single Edge Notch Bending (SENB) specimens with varying contents of graphene. It was shown that while the scaling of the pristine polymer follows Linear Elastic Fracture Mechanics (LEFM), this is not the case for nanocomposites, even for very low graphene contents. In fact, small specimens had a more pronounced ductility with limited scaling and a significant deviation from LEFM whereas larger specimens behaved in a more brittle way, with scaling of nominal strength closer to the one predicted by LEFM. This behavior is due to the significant size of the Fracture Process Zone (FPZ) compared to the specimen size which affects the overall fracturing behavior. This latter aspect needs to be taken into serious consideration since it is shown that, for the specimen sizes investigated in this work, neglecting the non-linear effects of the FPZ can lead to an underestimation of the fracture energy as high as 113%, this error decreasing for increasing specimen sizes. These findings were applied to previously published literature data, where it was shown that most of the specimens tested belonged in the transitional region between ductile and brittle behavior. As a result, the greatest deviation found between LEFM and SEL models was 156%.