Effects of thermal aging on uniaxial ratcheting behavior of vulcanised natural rubber

Vulcanised natural rubber (NR) tends to be hardened and lose damping capability as it is used at high temperature for a long period of time. Therefore, the thermal aging effects on the cyclic response of vulcanised NR need to be considered. In the present work, vulcanised NR sheets were thermally aged in an oven at a temperature ranging from 60 degrees C to 100 degrees C for aging time ranging from 24 h to 96 h. Subsequently, a series of uniaxial ratcheting tests were conducted on thermally aged vulcanised NR at room temperature. The thermal aging effects on the ratcheting behavior were experimentally investigated. The ratcheting strain can be restrained in thermally aged rubbers. The ratcheting strain decreases as the aging time or aging temperature increases. The reduction of ratcheting strain in thermally aged rubbers is attributed to the restrained ratcheting strain in the first cycle. Moreover, higher mean stress and stress amplitude cause faster ratcheting strain accumulation. Furthermore, the prior higher mean stress and stress amplitude can restrain the ratcheting strain in the subsequent cycles with lower ones. However, the loading rate has little influence on the ratcheting behavior of thermally aged rubbers.