Fatigue Characteristics of Vulcanized Natural Rubber for Automotive Engine Mounting (Characteristics of Composition and Mechanical Properties)

In order to investigate fatigue characteristics of vulcanized natural rubber (NR), fatigue tests were carried out under various R and variable loadings. In this paper, an indicator for the material design are shown with detailed observation of the fatigue process and it makes rubber more durable against crack initiation. We found that the fatigue crack initiated from the vicinity of CaCO3 by the observation of the fatigue process. Then fatigue tests were conducted using specimens which the content of CaCO3 inclusions were controlled. As a result, the fatigue life has improved in test pieces without the CaCO3 inclusions. The effect of the CaCO3 content on the fatigue life is related only to crack initiation, and the crack propagation was not affected. The continuous observation of the fatigue damages and the measurement of crack growth rate were conducted, and the change of the fatigue process caused by CaCO3 content is discussed by these results.