Distribution of strain to failure of single wood pulp fibres

The single-fibre composite test has been applied to characterize the distri bution of strain to failure of individual fibres from unbleached softwood k raft pulp. The fibre was moulded into a thermoset matrix which is subjected to a tensile test, whereupon the fibre fragmented with increasing applied strain. The measurements of mean fragment lengths and corresponding strain levels were used to determine the Weibull parameters of the distribution of strain to failure of the fibres by a least squares method. Three groups of fibres of the same kind were tested, which have been exposed to increased beating. The beating process in a PFI mill made the variability of strain t o failure decrease, whereas the average value remained constant until it dr opped rapidly for over-beaten fibres. This can be interpreted as a result o f interfibrillar debonding induced by beating.