| The exceptional mechanical and physical properties demonstrated for carbon nanotube, make it an excellent candidate for rubber composite reinforcement. However, little attention has been paid to the fatigue behavior of rubber reinforced by CNT at the state of art, though the fatigue properties of rubber components is directly related to its durability, reliability and security of rubber products used under dynamic conditions. Thus, this research subject was aimed at exploring the fatigue properties and mechanism of natural rubber filled with CNTs. In view of the above research goal, the main work and results are as follows:1. The fatigue resistance properties of CNT/NR composites filled with different loading CNT (i.e.,1,3 and 5phr) were examined at wide strain ranges (i.e.,20-100%), which was studied by using the crack growth approach. The results were compared with those of carbon black (i.e.,10,20 and 35phr) reinforced NR composites, which were of similar hardness with corresponding CNT/NR, respectively. Fatigue tests were carried out on one edge-notched specimens under cyclic tension loading. The results showed that the crack growth of CNT/NR composites had two opposite behavior. At lower strain ranges (20%-40%) and lower CNTs loading (not exceeding 3 phr), the crack growth resistance of CNT/NR composites is better than the similar hardness CB/NR composites; but the fatigue resistance advantage of CNT/NR composites is not obvious at higher strain ranges (40%-100%). Moreover, under high hardness, the fatigue life of CNT/NR composites is shorter than the similar hardness CB/NR composites, the gap between which more obvious with the increasing of hardness. From the perspective of tearing energy, the relationship between crack growth rate and tearing energy is different in CNT reinforced NR system and CB reinforced NR system. With the loading of CNTs increasing, the crack growth rate of CNT/NR composites increased with the tearing energy increasing. However, with the loading of CB increasing, the crack growth rate of CB/NR composites decreased with the tearing energy increasing. In order to further clarify the reason of above results, the research analyzed the effects caused by the filler in detail, including crystallization, hysteresis, crack blunting and deviation.2. This research was then focused on the fatigue performance of CNT/CB/NR composites. In the system of CB/NR system, keeping the total filler content in a fixed value,1,2,3,4,5phr CNT replaced the same amount of CB, respectively. Pre-cut strip specimens, dumbbell specimens and flex fatigue specimen were used to study the fatigue properties of CNT/CB/NR composites. It was found that the composites performed the best fatigue properties in the ratio of CNT/CB being 1/19. With increasing the ratio of CNT/CB, the fatigue properties of composites decreased. |
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