Stress softening of carbon black filled SBRs submitted to various large strain uniaxial tension cycles

Two carbon black filled SBRs were submitted to various uniaxial tension cyclic tests, including stretch-control tests and stresscontrol tests. Stress relaxation and stretch creep were measured according to the number of cycles. Results show a strong dependence of the material softening to the maximum loading applied and the number of cycles. After a few cycles (around 40), the softening evolves linearly according to the logarithm of the number of cycles. The cyclic softening is also shown to be locked by a low number (5) of overload cycles. More interestingly, the material softening appears to be unaffected by the loading cycle amplitude. This study aims at defining the parameters to include in a subsequent cyclic stress-strain model.