Fig. 6.

Qualitative theoretical explanation of the observed behavior. (A) Illustration of the two-dimensional fibrillar system considered. A semi-infinite crack extends along the interface between a fibrillated semi-infinite elastic body and a terminal film. (B) Illustration of the geometry of the repeating unit cell within the fibrillar strip and its associated geometric variables. (C) Variation of the local energy release rate available to the crack tip, G_L, as a function of the crack length, l. This example assumes a constant, remotely supplied energy release rate, G_R, and a sinusoidal variation due to the absorption and expulsion of energy by the fibrillar strip. The Xs indicate stable equilibrium crack positions; the Os indicate unstable ones. Note that when the crack propagates between unstable equlibria, G_R > W_ad.