. Conclusions
Tensile and flexural properties of plant fiber-reinforced hybrid
green composites containing kenaf, bamboo and coir fibers
with bio-based polymer (PLA) were assessed. Overall, hybrid
green composites of kenaf-coir/PLA (KCCK/PLA), bamboo-coir/PLA
(BCCB/PLA) and kenaf-bamboo-coir/PLA (KBCCBK/PLA) produced a
diverse range of results – the hybrid combinations (hybrid) compensated
for the inherent disadvantages ofthe individual materials.
Higher tensile strength was obtained from the combination of
kenaf, bamboo and coir fibers composites (KBCCBK/PLA), approximately
78% higher than that of KCCK/PLA and 20% higher than that
of BCCB/PLA while the differences in Young’s modulus of the three
composites weremoderate (2–25%).HighYoung’smodulus of kenaf
and bamboo fibers was found to contribute to better resist loads in
the outer layers of composites, while coir fibers showed high ductility,
counteracting the inherited properties of low elongation of
kenaf fibers in the composites. Kenaf and bamboo fibers enhanced
the stiffness of the composites due to their smaller cross-sectional
area. Even though the bamboo fiber bundles were measured as having
bigger diameter than coir and kenaf fibers, after wetting and
impregnation with PLA, the splitting of the bamboo fibers during
matrix impregnation produced fibers with a smaller cross-section
that contained far fewer defects than those with bigger diameter.
The images of composites fractures by optical microscopy showed
572 R.B. Yusoff et al. / Industrial Crops and Products 94 (2016) 562–573
that the untreated bamboo fibers led to poor interfacial adhesion
between fibers and PLA matrix, decreasing flexural and tensile
strength as well as stiffness of hybrid green composites. Interfacial
bonding was formed by matrix impregnation into the lumen in the
fibers, leading to interlocking between the fibers and the matrix,
thus preventing fracture of the cell walls. High flexural properties
were due to the selection of high strength and high modulus fibers
in the outer layers and the compatibility of kenaf and coir fibers
with PLA matrix, showing flexural modulus 70% higher than other
combinations. The combination of three types of plant fibers with
different mechanical properties shows potential to switch to 100%
plant fiber composites. These preliminary results will pave the way
to totally green composites instead of combining plant fibers with
synthetic fibers, which are costly and with damaging effect upon
the environment