Page 96 - Template Tesis UTM v2.0

that the peak stress and stiffness were higher in the in-plane direction. Moreover, it

was found that the peak stress and stiffness were highly dependent on the applied strain
rates, whereby the higher peak stress and stiffness were recorded at higher strain rates.

In addition, thicker laminate exhibited higher peak stress and stiffness in comparison
with thinner one.

Haque and Ali [121] investigated of S2-glass/vinyl ester on the compressive

properties and failure analysis using SHPB equipment. The comparison was also done
between dynamic and quasi-static properties of compressive strength, compressive

strain to failure and elastic modulus. During the quasi-static test, for unidirectional
laminate, loads were applied in fibre and transverse directions and only in fill direction

for plain-weave. The ultimate failure stress, failure strain and modulus were higher in
fibre direction with value of 201 MPa, 0.032 mm/mm and 6 GPa in comparison with

transverse direction of 80 MPa, 0.030 mm/mm and 2.5 GPa, respectively. For plain

weave S2-glass/vinyl ester, the ultimate failure stress, failure strain and modulus were
188 MPa, 0.036mm/mm, and 5 GPa respectively. When the applied load is parallel

with fibre direction, the dominant failures are the shear mode of microbuckling and
kink band formations in localized areas. These kind of failure modes were also

observed in plain weave laminates. However, when the load is in a transverse direction,
the failure started with matrix cracking which caused debonding and delamination.

However, it is interesting to note that fibre fracture did not occur at all, only resin

dominant failure modes. Both UD and plain weave specimens are strain rate dependent
with the higher failure strength and strain were recorded when the higher strain rates

applied.

Shaker et al. [108] used SHPB apparatus to investiagte the high strain rate

compression properties of aramid and ultra-high molecular weight polyethylene

(UHMWPE) composites in the out-of-plane direction at four different pressures of 2,4,
6 and 8 bar (to get the variation of strain rates). Both hybrid and non-hybrid specimens

exhibited the strain rate sensitivity. Initially, the stress showed a nearly linear increase
with strain and become non-linear at the later stage of deformation with further

increase in the strain. It was found that flow stress increased with the increasing
pressure as can be seen when the stress-strain curves go up gradually. In addition, the

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