Fibre entanglement provides the structural integrity in mechanically-bonded nonwovens by frictional restraints, such as that produced by hydro entanglement. Unlike many nonwoven assemblies, fibre segment orientations occur in three dimensions and this is a defining parameter of the structure of mechanically-bonded nonwovens. Hydroentangled fabrics can be produced in single- and multi-layer configurations. This study aims to characterise the dimensional, mechanical and structural characteristics of bi-layer hydroentangled carrier fabric. A 2⁴ full-factorial experimental design was followed to study the effect of four key hydro entangling process variables (water jet pressure, conveyor speed, nozzle diameter and number of injectors) on fabric structure and properties. Fabric tensile properties were characterized in three principal directions (machine-, cross- and thickness-direction) and linked to process variables by analysis of covariance. The regression models were constructed for key properties and an approach to select process variables for minimal consumption of specific energy was presented. An adapted testing method was developed for the characterisation of fabric tensile strength in the thickness-direction. Difficulties in applying standard methods of measuring resistance to delamination occurred because of the nature of inter-layer bonding in hydroentangled fabrics, where there is an absence of a discrete interface between two layers. The developed testing method was found suitable for a variety of nonwoven structures. The subject of fibre orientation distribution in nonwovens has generally been limited to in-plane characterisation but out-of-plane orientations cannot be ignored in mechanically-bonded assemblies. Based on an existing algorithm, fibre segment orientation distribution was determined in- and out-of-plane. The results were validated by physical testing of key dry-laid structures (parallel-, cross- and air-laid), followed by extension to selected bi-layer materials from the 2⁴ design to determine the relationships between process, structure and properties. Topological methods were utilised for direct and non-destructive estimation of fibre entanglement. An algorithm was presented to calculate splitting number which in relation to the total number of fibre crossings enabled an estimate of the degree of fibre entanglement. The approach was successfully demonstrated on simulated nonwovens assemblies and a preliminary investigation using real assemblies was also carried out.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:581958 |
| Date | January 2013 |
| Creators | Tausif, Muhammad |
| Publisher | University of Leeds |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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