Brittle-to-quasibrittle transition in creep rupture of 2D disordered elastic materials

Models of disordered elastic materials are well known to produce a brittle-to-quasibrittle transition as a function of disorder or system size. In 1D disordered fiber bundle models, an analytical prediction of the toughness and damage variation with disorder in the quasibrittle regime has been recently proposed. We find that a similar scaling exists in a 2D random fuse model. In the case of subcritical rupture, where the applied stress is lower than the network critical threshold but the system breaks through thermally activated rupture events, we study to what extent the subcritical damage is determined by the underlying brittle-to-quasibrittle transition. Whether this transition corresponds to an actual phase transition valid for all system sizes remains an open issue. We also discuss how the brittle-to-quasibrittle transition could help understanding the brittle-to-ductile transition often observed during impact of heterogeneous polymer materials (semi-crystalline, rubber toughened or gels).