Statistics of acoustic emission in paper fracture: precursors and criticality

Abstract

We present statistical analysis of acoustic emission (AE) data from tensile experiments onpaper sheets, for loading mode I, with samples broken under strain control. The results arebased on 100 experiments on unnotched samples and 70 samples with a long initial edgenotch. First, AE energy release and AE event rates are considered for both cases,to test for the presence of ‘critical points’ in fracture. For AE energy, no clearsignatures are found, whereas the main finding is that the event rate diverges whena sample-dependent ‘critical time’ of the maximum event rate is approached.This takes place after the maximum stress is reached. The results are comparedwith statistical fracture models of heterogeneous materials. We also discuss thedependence of the AE energy and event interval distributions on average event rates.