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The aim of this work was to establish a range of suitable process parameters which can be utilized to produce needlepunched nonwoven fabrics for geotextile applications. Nonwoven fabrics were produced from 100% PP, a blend of 50/50% PP/kenaf and 100% kenaf fibres. The depths of needle penetration of 4, 7 and 10 mm, stroke frequencies of 250, 350 and 450 strokes/min and mass per unit area of 300, 600 and 900 g/m2 were utilized for producing the fabrics, on a Dilo loom. The effect of depth of needle penetration, stroke frequency and mass per unit area on the fabric properties, namely, tensile strength, puncture resistance, pore size, water permeability and transmissivity were analysed. In addition, the effect of chemicals, namely, 10% ammonium hydroxide (NH4OH), 10% sodium chloride (NaCl) and 3% sulphuric acid (H2SO4) solutions on degradation of the fabric was also studied. The results have shown that density, thickness and nominal weight of the needlepunched nonwoven fabrics were related to each other and they were influenced by stroke frequency, depth of needle penetration and feed rate of the needlepunching process. The increase in nominal weight of the fabrics also increases thickness and density of the fabrics. The tensile strength and puncture resistance of the fabrics increased with the increases in stroke frequency, depth of needle penetration and fabric mass per unit area. However, lower tensile strength and puncture resistance were achieved in the fabrics produced at lower stroke frequency, lower depth of needle penetration and lower mass per unit area. Bigger pores were resulted in the fabrics produced at lower stroke frequency, lower depth of needle penetration and lower mass per unit area, however, pore size decreased with increases in stroke frequency, depth of needle penetration and mass per unit area. Water permeability depends on the pore size, properties of the fibres, stroke frequency, depth of needle penetration and mass per unit area. Higher tensile strength and higher puncture resistance were achieved in the needlepunched nonwoven fabrics produced from 100% PP fibres, therefore, they are suitable for some load-bearing geotextile applications, such as reinforcement and separation. However, higher water permeability was achieved in the fabrics produced from 100% kenaf fibres, therefore, they are ideal for geotextile applications where good water permeability is required. Higher values for transmissivity were obtained in the fabrics produced from a blend of 50/50% PP/kenaf fibres, therefore they are suitable for drainage applications. The fabrics produced from a blend of 50/50% PP/kenaf fibres achieved better values of tensile strength, puncture resistance, pore size and water permeability in comparison to that produced from 100% PP and 100% kenaf fibres. However, better tensile strength and puncture resistance were achieved in the fabrics produced from 100% PP fibres and bigger pore size and higher water permeability were achieved in the fabrics produced from 100% kenaf fibres. Therefore, it can be suggested that the nonwoven fabrics produced from a blend of 50/50% PP/kenaf fibres can fulfil almost all requirements of geotextile applications, such as, filtration, separation, reinforcement and drainage. The fabrics produced from 100% PP fibres were not damaged or deteriorated when treated with all the three chemicals due to chemical inertness of polypropylene. However, the fabrics produced from a blend of 50/50% PP/kenaf and 100% kenaf fibres were damaged and deteriorated when treated with H2SO4.

The shear strength of unidirectional glass-epoxy composites was determined experimentally by three standard shear tests. The tests consisted of short beam interlaminar shear tests, saw-cut shear tests, and torsion tests on circumferentially wound cylinders. Test results show that the short beam interlaminar shear tests and the torsion tests of circumferentially wound cylinders give approximately the same maximum shear stress. Test results also showed that the saw-cut shear test is not a good interlaminar shear test because of stress concentrations at the base of the saw cuts and high tearing stresses normal to the plane of shear. The shear strength determined by the beam and torsion tests is approximately 10 ksi, whereas the average shear strength for the saw-cut specimens is approximately 2.5 ksi. / Master of Science

Changes in nylon 6.6 and polyester filament yarns were determined after heat treatment with dry heat at various temperatures under constant length conditions. An attempt was made to relate structural changes and changes in physical properties due to heat setting. Density, obtained by the density gradient column technique, was used to calculate the degree of crystallinity as a structural parameter. Filament tensile strength and elongation at break were measured on a constant-rate-of-extension machine, and then toughness of the sample was obtained from the load elongation curve. The amount of dye uptake was estimated spectrophotometrically. Degree of crystallinity increased significantly as temperature increased for both nylon 6.6 and polyester fibers. Tenacity decreased substantially for nylon 6.6 and increased marginally for polyester. Elongation and toughness at break decreased for both nylon 6.6 and polyester. Tenacity of nylon 6.6 decreased despite an increase in degree of crystallinity. This suggests degradation of the fibers. Therefore, degree of crystallinity appeared to be of little importance as a contributor to change in tensile strength for degraded nylon 6.6. Tenacity of polyester was well predicted by degree of crystallinity. As crystallinity increased, tenacity of polyester increased. Elongation and toughness of both nylon 6.6 and polyester decreased as degree of crystallinity increased, but the relationship to crystallinity for polyester was not significant. Dyeability of both nylon 6.6 and polyester was well predicted by degree of crystallinity. In both cases, the amount of dye uptake decreased as crystallinity increased. This research suggests that determinations for structural changes such as degradation and orientation might be utilized in addition to crystallinity to predict tenacity of nylon 6.6 and elongation and toughness of polyester. / Ph. D.

The material properties of fibre networks and fibre reinforced composites are strongly influenced by fibre-fibre interactions. Stress transfer between load bearing elements in such materials is often dictated by the nature of the fibre-fibre interface. Inter-fibre bonding is solely responsible for internal cohesion in paper, because all stresses transferred between fibres operate through fibre-fibre bonds. . The future development of cellulosic fibre materials will require an improved understanding of the fibre-fibre interface. Fluorescence resonance energy transfer (FRET) was proposed as a new tool for the study of fibre interfaces. A protocol for covalent linkage of fluorophores to natural and regenerated cellulosic fibres was developed and the absorptive and emissive properties of these dyes were characterized. The fluorescent response of these dyed fibres in paper sheets was studied using steady-state fluorescence spectroscopy. Fluorescence micrographs of fibre crossings on glass slides were analyzed using the FRETN correction algorithm. Energy transfer from coumarin dyed fibres to fluorescein dyed fibres at the interface was observed. The FRETN surfaces for spruce and viscose rayon fibre crossings were distinctly different. The FRET microscopy method was able to detect statistically significant differences in spruce fibre interface development when fibre fraction and wet pressing were varied. The coalescence of natural cellulosic fibre interfaces during drying was also observed with the technique. Polysaccharide films were employed as model systems for the natural and regenerated cellulose fibre interfaces. It was found that pressing cellulose films did not result in significantly increased FRETN either due to resistance to deformation or the inability to participate in interdiffusion. Conversely, xylan films demonstrated a drastic increase in the FRETN signal with increased wet pressing. These results support the previously observed differences between regenerated cellulose fibres and natural wood fibres. The results of the FRETN analysis of the polysaccharide film model systems suggest that lower molecular weight amorphous carbohydrates are likely to be significant contributors to fibre interface development.