Multiscale Observation of the Fatigue‐Induced Damage Mechanisms in Carbon‐Black Filled Styrene‐Butadiene Rubber

Filled rubber materials exhibit a complex macroresponse characterized by stress softening, hysteresis, and dissipative heating when they are cyclically loaded. The relationship of these inelastic features to the microstructure changes is far from being fully established. This paper deals with the damage mechanisms in sulfur‐vulcanized styrene‐butadiene rubber (SBR) specimens in the diablo form reinforced with carbon‐black (CB) and zinc‐oxide (ZnO) fillers, and submitted to tension cyclic loading at room temperature. The microstructure alteration is characterized at different relevant scales and at different zones of the diabolo specimen by means of various technologies in the aim to report valuable insights about the mechanisms responsible for the macroresponse of this rubber‐filler material system. IR absorption spectra reveal that increasing filler content induces more interfacial interaction between CB and SBR chains. The environmental scanning electron microscopy (ESEM) observations show relevant altered morphologies of elastomeric chains with a predominant effect of both CB and ZnO fillers. A mesoscale observation of material density variation is presented using X‐ray computed tomography and the results are compared with those issued from ESEM. The macroscopic cyclic response of SBR‐CB‐ZnO composites implies microstructure changes with a significant influence of both CB and ZnO fillers. The various damage mechanisms are meticulously analyzed at different relevant scales and regions in the tested samples by means of complementary physical characterization techniques (X‐ray CT Scanner, ATR‐FTIR and ESEM).