Toughening of graphene-based polymer nanocomposites via tuning chemical functionalization
F Najafi and GR Wang and S Mukherjee and T Cui and T Filleter and CV Singh, COMPOSITES SCIENCE AND TECHNOLOGY, 194, 108140 (2020).
Previous experiments on the mechanics of graphene-based polymer nanocomposites report their mechanical properties far below theoretical predictions. A critical factor in this regard is the nature and strength of nanofiller/matrix interfacial bonding. Herein, beneficial effects of chemical functionalization on the interfacial mechanical properties of graphene-based polymer nanocomposites are investigated using complementary experiments and molecular dynamics (MD) simulations. We report that by tuning the extent and chemistry of the functionalized species, (approximately 10%), graphene-PMMA nanocomposites can achieve superior mechanical properties by improving the interfacial load transfer. Compared to pure PMMA, an increase of 46% in Young's modulus and 119% in energy absorbed per unit volume during fracture, respectively, were achieved for 10% functionalized nanocomposites. Such an increase in energy absorbed was caused by a transition in crack propagation mechanism from interfacial slippage to crack arresting behavior, owing to the enhanced interfacial bonding. MD simulations revealed that such a change in mechanism is caused by the formation of both hydrogen bond networks and physical entanglements at the interface. While the methodology can be applied for different nanocomposite systems, the present results may provide an avenue for more efficient design of graphene-based nanocomposite structures.
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