A critical local energy release rate criterion for fatigue fracture of elastomers

摘要

Using Digital Image Correlation on high-resolution images, the full strain field near the tip of a crack propagating under cyclic loading in an elastomer was characterized. We show unambiguously, and for the first time, the existence of a strongly localized and highly oriented process zone close to the crack tip and propose a simple physical model introducing a local energy release rate g_(local) = W_(unloading)H_0, where W _(unloading) is the unloading strain energy density in uniaxial tension at the maximum strain measured at the crack tip, and H_0 is the undeformed size of the highly stretched zone in the loading direction. Remarkably, the crack growth rate under cyclic loading is found to fall on a master curve as a function of g_(local) for three elastomers with different filler contents and crosslinking densities, while the same crack growth rate as a function of the applied macroscopic energy release rate G, differs by two orders of magnitude for the same three elastomers.