RIB MARKS AND KINETICS OF JOINT PROPAGATI ON - AN ANALOG MODEL IN POLYMETHYLMETHACRYLATE (PMMA)

Joint surfaces often show fractographic features such as plumose struc tures, rib marks and hackles. Experiments in an analogue material (PMM A) are developed in order to test the different hypotheses proposed in literature for rib mark formation. Loading conditions are varied in o rder to correlate various fracture kinetic behaviours with rib mark mo rphologies. This modelling shows two different types of rib marks: one poorly marked corresponding to strong velocity discontinuities, the o ther with crest corresponding to stop and restart conditions. The same morphological and mechanical distinctions can be made on natural join t surface features.