macroscopic level (regime A). Then, sacrificial bonds start to break exactly as predicted by the affine deformation. Here both the average stress concentration, $\langle\Lambda\rangle$, and its variance are zero (regime B). Upon further increasing the deformation, the variance of $\Lambda$ starts to grow indicating stress heterogeneity in the system, quickly followed by an increase of $\langle\Lambda\rangle$ indicating stress concentration (regime C). As a result strong sacrificial bonds also start to break and failure of weak sacrificial bonds is postponed or even prevented (see Supplemental Material [@supp]). Finally we arrive at a peak in $\langle\Lambda\rangle$, after which the $\langle\Lambda\rangle$ decreases until macroscopic failure is reached (regime D). We attribute this decrease to structural relaxation of the sacrificial network via the formation of microcracks, leading to loss of rigidity and eventually loss of percolation in the sacrificial network. It must be noted that the variance in $\langle\Lambda\rangle$ remains constant, indicating that heterogeneity in stress is present until the final failure event.

### Crack development and stress delocalization

![image](figure8.eps)

The development of stress heterogeneity and stress concentration during deformation, is the result of microscopic damage evolution in the sacrificial network: the nucleation and propagation of cracks. We also suggested that the development of 