Conductivity and rupture in crack-deteriorated systems

2014 Experimental results on the conductivity and rupture properties of two-dimensional continuum crack deteriorated model systems are presented. Two different systems are considered. In case 1, cracks are randomly positioned on the bonds of a regular square lattice drawn on the continuous system. Our finite size systems barely reach the critical percolation regime. The results rather correspond to a mean field regime which may be described by effective medium theories. In case 2, crack positions and orientations are randomly chosen in the 2D continuum (« blue cheese »). In this case, strong screening effects allow us to obtain the critical regime and to measure the corresponding critical exponents. The measurements are compared with recent theoretical results which take account of the different modes of deformations occurring locally at the crack level. In particular, buckling in thin foils is found to be an important deformation mode which screens efficiently the stress enhancement at the tips of the cracks, thereby changing the critical exponents. J. Phys. France 51 (1990) 247-257 1 er FÉVRIER 1990,