Acoustic emission under out-of-plane tearing of paper

Acoustic emission (AE) that occurred during the tearing of handsheets made from softwood or hardwood kraft pulp beaten to various degrees was measured and analysed to investigate the relationship between tear strength and the micro failures that occurred. Maximum amplitude distribution of the AEs correlated with the frequency of fibre failure and failures of strong and weak fibre bonds with an increase in beating degree. As a result, the increase in tear strength by lightly beating both pulps corresponded to increases in fibre failure and failure of strong fibre bonds. The decrease in tear strength with further beating of the softwood pulp corresponded to decreases in fibre failure and failure of strong fibre bonds. The marginal increase in tear strength by further beating the hardwood pulp corresponded to an increase in fibre failure and decrease in failure of strong fibre bonds.