Parameters Influencing Fatigue Characteristics of Tyre Tread Rubber Compounds

Tyre acts as a linkage between a vehicle and road. Out of many functions a tyre must perform in its service life, durability is one of them. In service, a tyre is exposed to all kinds of road hazards (sharp asperities, pot holes, nails, etc.) and this may cause cuts on different parts of a tyre, viz. tread, sidewall, etc. These cuts propagate during subsequent loading and tyre may fail on reaching a critical crack length. To ensure tyre durability, knowledge of fatigue crack propagation is essential. In a tyre, majorly Natural rubber (NR), Butadiene rubber (BR) and Styrene butadiene rubber (SBR) are used. In this work, fatigue crack growth (FCG) characteristics of these rubbers and their blends using a Tear & Fatigue Analyser (TFA, Coesfeld GmbH & Co. KG, Germany) are studied in detail. This study emphasized on capturing the influence of material composition (rubber, rubber blend and filler) and operational conditions (temperature, waveform and R ratio) on FCG resistance of tyre rubber compounds. It has been observed that rubber blends have shown superior FCG resistance over single rubber compounds up to a certain tearing energy level. The influence of filler on FCG resistance has varied effect on crystallized and non-crystallized rubbers. In addition to filler, much higher property enhancement is observed in non-crystallized rubber compared to crystallized one. FCG resistance found to be increased with decrease in carbon black particle size. Temperature has a deleterious effect on FCG resistance and this effect is more prominent in blend compounds. Gaussian pulse load form exhibited higher FCG rate compared to sine loading. Positive R ratio exhibited superior FCG resistance, especially in NR compound. It has also been observed that advantage of positive R ratio effect in terms of superior FCG resistance diminished due to increase in measurement temperature. Fractured surface micrographs of NR compounds are distinctly different from BR and SBR compounds and reflected as higher root mean square roughness parameter.