Non-Woven Fabrics. Part VI

Abstract

Measurements of lateral contraction in the plane of the sheet and of changes in thickness were made on cross-laid and random-laid bonded-nber fabrics subjected to a tensile stress either parallel or at right angles to the machine direction. From these measurements, the corresponding changes in volume were derived. The results show a large lateral contraction accompanied by an even larger percentage increase in thick ness, giving a resultant increase in volume on extension. All these changes were non-linear functions of the tensile strain. For the study of the mechanical anisotropy of cross-laid fabrics, composite fabrics were prepared by bonding together two sheets of random-laid web, with varying angles between the machine directions of the components. From tensile tests on samples cut from the composite sheet, polar diagrams representing the variation of Young's modulus and rupture strength with direction were obtained. The results were in close agreement with theoretical values calculated on th assuption that the properties of the composite sheet in a given direction are the average of the properties of the two constituents in the corresponding direction.