| dc.description.abstract | This abstract summarizes the results of a research work
done by Cyrus Concellor Muthuri Kirima, for a master of
science degree thesis entitled "AN INVESTIGATION INTO THE
MECHANICAL PROPERTIES OF COMPOSITE MATERIALS REINFORCED
WITH THE LOCALLY OBTAINED NATURAL FIBRES". A thesis
submitted in partial fulfilment for the award of a master
of science degree of the University of Nairobi, in
December, 1993.
The physical and mechanical properties of coconut fibre
were investigated. The results obtained for the physical
properties were; cross-sectional area, 8.0 x 10-8 m", and
density, 5.3 X 10-8 kgm-2• The cross-sectional area of the
fibre varied between individual fibres and along its
length. The following mechanical properties were obtained;
tensile strength 159.30 MNm-2
, Yield stress 70.53 MNm-2
,
Modulus of Elasticity 4.02 GNm-2 •.. and an elongation at
failure of 24.20%
Sisal fibre was used to reinforce the cement mortar matrix
in two forms; parallel aligned and chopped randomly
aligned. The coconut fibre reinforced the matrix only in
chopped form, randomly distributed in the matrix. The
resulting composite was tested In flexure, (4-point
bending) and direct tensi6n to establish' the effect of
fibre reinforcement on the physical and mechanical
properties.
viii
Fibre reinforcement improved some mechanical properties of
the composite. A linear increase in flexural and tensile
strength with fibre volume fraction was obtained for
parallel aligned sisal fibres. The increase in strength
attained maximum values of 9.46 MNm-2 for flexure at 7.5%
fibre reinforcement volume fraction and 3.98 MNm-2 in
tension at 7% fibre volume fraction. Chopped sisal and
coconut fibres generally increased the flexural and
tensile strengths of the composite, but the maximum values
obtained were low compared to the parallel aligned sisal
fibre reinforcement. The maximum flexural strength occurred
at 6% fibre volume fraction of 4.74 MNm-2 for sisal fibre
reinforced composite and 4.24 MNm-2 at 8% volume fraction
for coconut fibre reinforcement respectively. The maximum
tensile strength values obtained were 2.94 MNm-2 for sisal
fibre reinforcement and 2.09 MNm-2 for coconut fibre
reinforcement. These occurred at 7% and 6% fibre volume
fraction for sisal and coconut respectively. On the other
hand, fibre reinforcement resulted into a linear decrease
in the composite Modulus of Elasticity. Based on the above,
the results obtained were therfore valid for the range of
study.
Fibre addition into the cement mortar matrix gave a
decrease in the composite density, while the amount of
voids present increased. The interfacial bond strength ,
between sisal fibre and the cement mortar matrix decreased
with increase .in fibre volume fraction. The calculated
value tends to a mean value above a fibre volume fraction
of 4%. | en |
