This project relates to the study of the dynamics of a crack front propagating through a weak plane of a transparent block made of two Plexiglass (PMMA) plates annealed together. The main goal of the project is to study in a systematic and controlle d way, both experimentally and by simulations and theory, mode II and mode 1 fractures along the weak interface of the Plexiglas block. We are in particular interested in the mode II fracture but will also study the fracture front line move ment in mode I under the slow creeping motion observed just after the external displacement is turned off.
A high resolution set-up with an ultra fast CCD camera has recently been realized by support from NFR and the University of Oslo and has permitted us to follow interfacial crack front propagation. We have observed in mode I that the crack front dynamics is driven by local and irregular bursts whose size and velocity are power-law distributed.However, so far, no systematic studies have been performed to study this problem in mode 2 -which is the one relevant for e.g. earth quake dynamics. The experimental work will be performed in parallel to theoretical
investigations and will in particular be compared to numerical models of o ur experimental system.