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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.

Nonwovens form a significant and rapidly growing sector of the textiles industry. The nonwovens sector originally set out to provide economical alternatives to traditional textiles for functional product components such as interlinings and carpet backings. Through constant growth and development nonwovens are now considered as sophisticated engineered fabrics that economically meet specific functional needs. Since the 1970's, however, the potential to use nonwoven fabrics and technologies within design has been under consideration by textile researchers, textile artists and fashion and textile designers and makers. The resulting fabrics have found application in mass marketable products such as gift and flower wrap and as one-off designer products such as scarves. In comparison to traditional sectors of the textile industry such as woven textiles, however, in regard to design there seems to be little middle ground between these two production contexts. Further to this, the range of nonwoven technologies that have been explored by textile designers, makers and artists is relatively limited and focuses predominantly on the needle-punching method of manufacture to produce felt-like fabrics. This situation presents a potentially missed opportunity within the nonwovens sector of textile manufacture. The research presented in this thesis aims to identify and explore the undeveloped opportunities to design nonwoven materials from an aesthetic perspective using a specific range of production processes and materials. The work is set within the context of designer maker practice and as such considers both industrial and craft perspectives on the design and manufacture of nonwovens. In doing so the relationship between craft and industry within the sphere of nonwovens is brought into question and the opportunities and limitations of working as a designer maker within this sphere are explored. The development of textile products for niche, high-end markets is of growing importance within the European textiles industry. This research explores the potential to develop design-led nonwovens for high-end markets. The work was conducted using a practice led research approach which revolved around the development of innovative new fabrics suitable for high-end markets. The work focuses on the use of carding, needle-punching and thermal bonding technologies that utilize heat and pressure and subsequent decorative finishing processes including devore, embossing and laser cutting. The ability to design nonwoven fabric structures specifically for use in these processes formed a central part of the contribution to knowledge made within the work. In particular, the development of devore and laser techniques for nonwovens made from contrasting fibre layers or with decorative materials embedded within them. The fabrics produced evidence new design concepts within the sphere of nonwovens. The suitability of the designs for production within different manufacturing contexts was assessed through a series of interviews with nonwoven manufacturers and their suitability for the high-end markets was evaluated through a series of focus groups and interviews with textile and product designers. The qualitative nature of the analysis made provides a new perspective on the design value of nonwovens. The results of the research confirmed the aesthetic appeal of certain fabrics within the collections produced and their suitability for high-end markets. The findings identified key factors in regard to how value is attributed to nonwovens within this market and suggested that further research into developing high-value nonwovens is required. The work identified key issues that designers working with nonwoven technologies need to be aware of to enable designs that are relevant for commercialization to be developed.

L’objectif de la thèse est l’étude et le développement de médias fibreux avec des fibres ultrafines à travers l’utilisation de la technologie nano-meltblown ainsi que de l’utilisation de fibres bicomposantes îles-en-mer. Cette approche implique un double travail, à la fois sur l’obtention de fibres ultrafines et sur l’homogénéité des médias fibreux. En effet, pour chaque technologie, l’élaboration d’un média fibreux induit une certaine hétérogénéité. L’origine de cette hétérogénéité est multiple : distribution des diamètres des filaments, variation locale de l’épaisseur, de compacité ou de la masse de fibres. Ce qui nous a conduit à mener, en parallèle des travaux d’élaboration de médias, une étude et une modélisation des performances de filtration afin de mieux comprendre l’impact des fibres ultrafines et de l’hétérogénéité des médias fibreux en filtration de l’air. La majorité des modèles de filtration (perméabilité et efficacité) considèrent, en effet, un média fibreux idéal avec des fibres monodisperses et une répartition de matière homogène au sein du média fibreux. Or, en réalité, ces conditions sont rarement réunies, ainsi comprendre l’influence des différentes hétérogénéités sur les performances de filtration peut s’avérer un enjeu important pour améliorer les performances des médias filtrants. La modélisation de cette hétérogénéité se fonde sur la correction des modèles d’efficacité de la littérature à partir des données expérimentales / The goal of the thesis is the study and development of fibrous media with ultrafine fibers through the use of nano-meltblown technology as well as the use of bicomponent islands-in-sea fibers. This approach involves dual work, both on obtaining ultrafine fibers and on the homogeneity of fibrous media. Indeed, for each technology, the elaboration of a fibrous media induces heterogeneities. The origin of this heterogeneity is multiple: distribution of filament diameters, local variation in thickness, packing density or basis weight. This led us to carry out a study and a modeling of the filtration performance in order to better understand the impact of ultrafine fibers and the heterogeneity of fibrous media in air filtration. Most of filtration models (permeability and efficiency) consider an ideal fibrous media with monodisperse fibers and a homogeneous distribution of matter within the fibrous media. In reality, these conditions are rarely met, so understanding the influence of different heterogeneities on filtration performance can be an important issue to improve the performance of filtering media. The modeling of this heterogeneity is based on the correction of the models of effectiveness of the literature from the experimental data