The Effect of Fibre Orientation on the Zero-span Testing of Paper

Abstract

In this study, a new technique for producing almost fully aligned paper sheets was developed, and the resulting sheets were used to test the validity of the theory most commonly used to relate zero-span tensile strength to individual fibre strength. The standard theory predicts that a zero-span test of a sheet with randomly oriented fibres should yield a breaking load equal to 3/8 of the load that would be observed if all the fibres were aligned in the direction of loading. It is widely used, in spite of the fact that the underlying assumption of affine deformation is questionable under true zero-span conditions. The results obtained here suggest that the fibre strength may be overestimated because inclined fibres in a zero-span grip actually contribute more than the theory predicts. However, the results also suggest that this effect may be confounded because other factors lead to a variable contribution of individual fibres to the zero-span strength of the sheet.