Branching in constrained brittle layers

The branching mechanism in constrained layers was studied experimentally and, in particular, the effect of bridging on the branching mechanism was rationalized. The behavior of an unconstrained thin alumina specimen together with specimens with constrained layers indicated that as the interfacial shear strength increases, the branching phenomenon decreases. The SERR for an unconstrained plate increases at a high rate as the crack advances and branching takes place to dissipate the increasing energy. In contrast, at infinite interfacial shear strength the SERR reaches a low steady state value, when the crack advances as a tunneling crack. For this case branching should be avoided. This behavior is important for the practical application of layered structures.