To show the dynamic mechanical behavior within a wide

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to show the dynamic mechanical behavior within a wide range of temperatures and obtain the viscoelastic properties for calculating the tearing energy. Significant reduction in the fatigue crack growth rate was reported by adding a small amount of OMt to the natural rubber composites in a pure shear fatigue test under the cyclic loadings. Moreover, they plotted the tearing energy against the crack growth rate in the log–log scale figure to compare the strength of different composites. (Kim and Jeong) experimentally evaluated the fatigue life and fracture morphology of natural rubber compounds filled with three types of carbon black, N330, N650, and N990. Moreover, they compared the critical J-value, the fracture morphology, and the hysteresis among the aforementioned types of natural rubbers. It was concluded that the fatigue life of natural rubber with N650 is shorter than that of others, due to the existence of large carbon black agglomerates, which could be separated from the rubber matrix easily. In addition, the
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P a g e | 11 hysteresis or critical J-value increased with the rise in the small-scale roughness value. (Wu et al.) Suggested the addition of Nano-dispersed clay into the carbon black-filled SBR in order to increase the fatigue life. They found out that Nano-dispersed clay layers could blunt the crack when they are distributed over carbon black. Hence, the tearing energy and hysteresis increased when the amount of clay increased. Fatigue crack growth prediction in rubber-based materials has been also explained by the theoretical results. (Lindley) proposed a theoretical method in comparison with the experimental data to consider the effective crack tip diameter in the analysis. They observed the extension and retraction stress–strain curves in order to express a condition at which the crack growth resistance was increased. Finally, (Schubel et al.) pointed out a relationship between the fatigue crack growth rate and tearing energy in notched-edge tire rubber specimen, which was a blend of natural rubber and polybutadiene filled with carbon black. They described the methods by which the tearing energy could be determined and expressed a power law relationship between the crack growth rate and tearing energy. Tearing energy is the energy release per unit area of crack surface growth. Hence, they could fit the power law relationship to the experimental data so that the variables in the relationship could be obtained. Switching the power law equation into a logarithmic one, the comparison between the linear curves of tearing energy could be depicted with respect to the crack growth rate. They explained that the higher slope of the curves will lead to rise in the crack growth rate value, quickly. The tearing energy was expressed in terms of the crack length.
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P a g e | 12 Furthermore, the crack length could be written as a function of number of cycles and they defined a critical value for the tearing energy at which the specimen will fail with a specific - number of cycles.
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