EFFECTS OF FABRIC ARCHITECTURE AND ALKALI TREATMENT ON THE MECHANICAL PROPERTIES OF COTTON FABRIC-REINFORCED UNSATURATED POLYESTER COMPOSITES
EFFECTS OF FABRIC ARCHITECTURE AND ALKALI TREATMENT ON THE MECHANICAL PROPERTIES OF COTTON FABRIC-REINFORCED UNSATURATED POLYESTER COMPOSITES
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Date
2014-07
Authors
ACHUKWU, Okechukwu,
Emmanuel.
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Abstract
The effects of fabric architectures and alkali treatment on the properties of cotton fabricreinforced
unsaturated polyester composites have been studied. The problems of low
mechanical properties of textile composites from natural origin have been a source of
concern for researchers; insufficient utilization of cotton fibres has further reduced the
economic returns of cotton growers. In this work, four different yarns of known count were
twisted (plied) to obtain a single strand which was woven and knitted into fabrics of
different architectures. The cotton fabrics were subjected to chemical modifications using
20% sodium hydroxide for 1 and 2 minutes and its influence on some mechanical
properties were analyzed. The fabrics were used to reinforce unsaturated polyester resin as
matrix, applying both single layer and two layers of fabrics to form different 2-ply laminate
configurations. The tensile and flexural strength, tensile and flexural modulus, impact
strength and hardness of the textile composites were compared. Alkali treatment improved
the tensile strength and breaking extension of the fabrics by 10-30% and 31-56%
respectively requiring a certain percentage concentration and duration of treatment, going
by the fact that the close treatment times of 1 and 2 minutes with 20% concentration of
sodium hydroxide gave inconsistent tensile strength and breaking extension. Fabric
architecture was found to have great influence on the breaking strength of the fabrics. The
tensile strength of the fabrics was found to decrease in this order: Plain woven fabric >
twill fabric > knitted fabric when untreated, but when treated, twill fabric > plain fabric >
knitted fabric. Composites reinforced with twill fabrics generally had better tensile strength
and modulus as well as flexural strength and modulus than those reinforced with plain and
knitted fabrics either when the reinforcing fabrics were untreated or treated with sodium hydroxide with an increase of 72–119%. The flexural strength of composite with twill,
plain and knitted fabrics are 62.32%, 56.75% and 52.68% respectively and increased by
65%, 60% and 37% when treated with 20% NaOH. Results also showed that increase in the
volume of reinforcement (increase in fabric layer) gave a corresponding increase in the
mechanical properties of the composites; however, the increase was not proportional with
respect to those composites reinforced with single fabric samples. The mechanical
properties tested were optimized by the plying effect carried out on the yarns. The impact
strength of the unsaturated polyester was improved by about 105% when reinforced with
the fabrics. Composites reinforced with knitted fabrics showed better resistance to impact
forces than other fabrics with good energy absorbing characteristics. There was an increase
in the Rockwell hardness of polyester resin composite for both single and double layer
reinforced laminates. Composites with twill fabrics gave highest hardness number (25.9)
than those of other fabrics (plain, 24.4 and knitted, 22.2) for the single ply and same for 2-
ply (twill-twill, 30.6; plain-plain, 29.9 and knitted-knitted, 25.6). Much variation in
hardness numbers were not recorded for the various reinforcements. The behaviour of other
hybrid composites reinforced with two layers of fabrics was seen to follow the properties of
the fabrics reinforcing them.
Description
A THESIS SUBMITTED TO THE SCHOOL OF POSTGRADUATE
STUDIES,
AHMADU BELLO UNIVERSITY, ZARIA
Keywords
FABRIC ARCHITECTURE ,, ALKALI,, TREATMENT,, THE MECHANICAL,, PROPERTIES,, COTTON FABRIC-REINFORCED,, UNSATURATED ,, POLYESTER COMPOSITES.