Statistics of acoustic emission in paper fracture: precursors and criticality

Abstract

We present statistical analysis of acoustic emission (AE) data from tensile\nexperiments on paper sheets, loading mode I, with samples broken under strain\ncontrol. The results are based on 100 experiments on unnotched samples and 70\nsamples with a long initial edge notch. First, AE energy release and AE event\nrates are considered for both cases, to test for the presence of "critical\npoints" in fracture. For AE energy, no clear signatures are found, whereas the\nmain finding is that the event rate diverges when a sample-dependent "critical\ntime" of the maximum event rate is approached. This takes place after the\nmaximum stress is reached. The results are compared with statistical fracture\nmodels of heterogenous materials. We also discuss the dependence of the AE\nenergy and event interval distributions on average event rates.\n