Crack tip damage in rubber compounds

The application of the crack layer theory to fatigue crack propagation (FCP) in rubber compounds is discussed. A crack tip damage evolution coefficientμ is employed to assess the extent of damage as a fraction of the damage associated with critical crack propagation. The results can be expressed in the form $$frac{{da}}{{dN}} = frac{{beta {rm T}^2 }}{{mu T_c - T}} ,$$ where da/dN is the rate of FCP,T is the tearing energy (energy release rate) whose critical value isT _c, andβ is a phenomenological constant. Experimental data for two rubber compounds, previously obtained by other workers, have been analyzed using the crack layer approach. Although damage, sometimes, cannot be easily detected in the case of rubber samples,μ increases during stable crack propagation. The value of the damage coefficientμ evolves differently for each compound approaching unity at catastrophic failure.