ARTICLE This journal isExfoliated graphene oxide (GO) reinforced natural rubber (NR) composites were prepared by a simple and promising latex co-coagulation method. Latex co-coagulation realized the complete exfoliation and uniform dispersion of GO in NR matrix. The quasi-static fracture and dynamic fatigue behaviors of composites were investigated. Mechanical properties and J-testing were used to characterize the fracture resistance, and fatigue tests were carried out under cyclic condition of constant strains. Results revealed that with increase in GO sheet content, the mechanical properties, fracture initiation and propagation resistance were all highly improved. A much higher reinforcing efficiency of GO sheets than that of traditional fillers was realized. Fatigue crack growth resistance was remarkably enhanced with the incorporation of only 1 phr GO sheets. The relatively weak fatigue resistance of composites filled with 3 phr and 5 phr GO was attributed to their high hysteresis loss and tearing energy input. It revealed that GO sheets would be promising filler in preparation of rubber composites with high fracture and fatigue resistance at low filler content.

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The quasi-static fracture and dynamic fatigue behaviors of natural rubber composites reinforced with hybrid carbon nanotube bundles (CNTBs) and carbon black (CB) at similar hardness values were investigated on the basis of fracture mechanical methods. Mechanical measurement and J-integral tests were carried out to characterize the quasi-static fracture resistance. Dynamic fatigue tests were performed under cyclic constant strain conditions with single-edged notched test pieces. The results indicate that synergistic effects between CNTBs and CB on the mechanical properties, fracture, and fatigue resistance were obtained. The composite reinforced with 3-phr CNTBs displayed the strongest fatigue resistance. The synergistic mechanisms and dominating factors of quasi-static and dynamic failure, such as the dispersion state of nanotubes, hybrid filler network structure, strain-induced crystallization, tearing energy input, and viscoelastic hysteresis loss, were examined. The weakest fatigue resistance of the composite filled with 5-phr CNTBs was ascribed to its strikingly high hysteresis, which resulted in marked heat generation under dynamic fatigue conditions. V C 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42075.

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