Single fibre pull-out tests and the elmendorf tear strength of paper

In this study, single fibre pull-out tests were used to evaluate the qualitative relationship between the energy consumed during fibre pull-out and that consumed during fibre fracture. Load-displacement curves for single fibres extracted from the paper network revealed that the load on the fibre typically dropped about 75% after it debonded from the network, but that there was a long tail region where the force decayed in proportion to the remaining embedded length. It was concluded that frictional forces do exist in the network, and that the energy associated with pulling the fibre out from the network can be substantial. However, the elastic energy stored in the fibre prior to failure was not insignificant, and the results suggest that a proper mechanistic model for tear strength should consider both fibre fracture energy and the effect of frictional pull-out.