Tensile properties of as-received and surface-treated coir fibres and composites

Madueke, Chioma (2021). Tensile properties of as-received and surface-treated coir fibres and composites. University of Birmingham. Ph.D.

Preview

Madueke2021PhD.pdf
Text
Available under License All rights reserved.
Download (7MB) | Preview

Abstract

The primary aim of this research project was to characterise and to determine the tensile properties of as-received and surface-treated coir fibres prior to use in composites. The term “as-received” is defined here as where the coir fibres that were received from the supplier was cleaned using a vacuum device, washed thoroughly in tap water for 30 minutes and dries at 80 oC for two hours. The surface treatment of the as-received coir fibres in sodium hydroxide involved immersion at specified concentrations of 1, 5 and 20 % for 24, 48 and 72 hours at 30, 50 and 80 oC. The silanes used were (3-aminopropyl) trimethoxy silane and (3- glycidyloxopropyl) trimethoxy silane, where the NaOH concentrations studied were 0.5, 1 and 1.5 % in distilled water.

The heat treatment temperature was of particular interest because it is known that lignin can cross-link above 140 oC: it was anticipated that this would lead to an increase in the Young’s modulus. The heat treatment was carried out at 40, 60, 80, 120, 160, 180 and 200 oC in a vacuum oven and tube furnace in air. The vacuum oven was used to investigate the effect of temperature in the absence of air. A brief study was undertaken to investigate the effect of lateral compaction of the fibres on the tensile properties. This was undertaken to determine if the compaction of the intrinsic porosity in the fibres would influence the apparent tensile
properties.

Variability in the diameter of coir fibre along the length of randomly selected fibres was observed. The tensile strength was found to decrease as a function of the coir fibre diameter. Similar to the findings on the influence of diameter on the tensile properties, a steady decrease in the tensile strength but an increase in the Young’s modulus of coir as the gauge length increased was observed.

However, heat treatment of coir fibre in the absence of air led to a reduction in the tensile strength of the fibres especially above heat treatment temperature of 160 oC. A reduction of 12 to 27% in strength was observed for the vacuum oven heat-treated coir fibres and a reduction of 28 to 88% observed in the tube furnace (with air) treated fibres. Unidirectional arrays of coir fibres were hybridized with spread E-glass to manufacture a new class of hybrid composites. An improved tensile property was recorded for the E-glass hybridized coir fibres such as has not been reported in the literature.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):