Page 60 - Polymer-based Nanocomposites for Energy and Environmental Applications

38 Polymer-based Nanocomposites for Energy and Environmental Applications

From the stiffness point of view, an average increase of 11.63% is observed with the
addition of the 3.5% of I30E, with respect to the nanostructured laminate total weight.
It is also demonstrated that, the indentation power law is also applicable to the
nanocomposite studies. When the low-velocity impact results are analyzed, they show
an increase in the energy absorption close to 48% for low energies, 20 J, 15% increase
for medium-high energies, 60 J, and 4% for high energy, 80 J. Also, impact response
of the composite laminates is analyzed by force-displacement history as shown in
Fig. 2.11. Finally, the presence of intercalated nanoclays into laminates leads to
not only an enhancement on stiffness but also an increase on impact resistance/frac-
ture toughness and it changes into failure mechanisms, that is, from interlaminar to
intralaminar. However, a competing mechanism between stiffness and fracture tough-
ness is noticed, as the 10% nanoclay content laminate and the 5% condition does not
perform. As the amount of intercalated nanoclay content has varied from 0% to 10%,
the optimum condition for low-velocity impact seems to be around 5%.
Zhu et al. [27] have reported the processing of a glass fiber-reinforced vinyl ester
composite with nanotube integration and have examined the reinforcement potential
on interlaminar shear strength. They have used several sidewall-functionalized nano-
tube, and the derivatives have also prepared in order to obtain high dispersion and
matrix bonding. Carbon nanotube has enhanced the vinyl ester/glass fiber composites,
which are fabricated by a vacuum-assisted resin transfer molding process. They have
found that, the overcoating the glass fiber weave with nanotubes and processing mod-
ification have led to the enhancement of the interface properties. A maximum of 45%
increase in the shear strength over control sample has been observed on several types
of nanotubes with a very small amount of nanotubes (0.015 wt%) coated in the
midplane ply. Nanotube-reinforced composites show remarkable promise to improve
the Z-axis mechanical properties of composite laminates. The results from the short
shear tests of the composites with several types of nanotubes coated on the glass fibers

2400

2200
Max force (N) 2000 Nano 0%

1800
Nano 1%
Nano 2%
1600 Nano 5%
Nano 10%
1400
8.0 8.5 9.0 9.5 10.0 10.5 11.0 11.5 12.0
Displacement at F max (mm)
Fig. 2.11 Force-displacement plot for 40, 60, and 80 J [26].