Propagation energy rubber concentration

Craze Nucleation Theory. In various ways it has been suggested that the role of the rubber particles is that of stress concentrators. Thus, Schmitt and Keskkula (33) believe that the multiplicity of stress concentrators (i.e., a multitude of weak points) produce a large number of small cracks rather than a few large ones more energy is needed to propagate a large number of small cracks, and stress fields of the various... 

The first quantitative studies of fatigue in polmers, which concentrated on rubbers [150-152], applied the tearing energy concept of fracture proposed by Rivlin and Thomas to fatigue crack propagation. Thomas [150] showed that the fatigue crack growth rate could be expressed in the form of an empirical relationship... 

Cracks are less important for tough materials (e.g. rubber, plastics and metals) since excess strain energy is used in deformation of the material rather than crack propagation. Thus in ductile metals, for example the stress concentration at the top of a crack will cause deformation of the material around the crack tip, resulting in a larger tip radius and lower stress concentration. 

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