Page 695 - Polymer-based Nanocomposites for Energy and Environmental Applications

Carbon nanotube-based nanocomposites for wind turbine applications 639

CNTs have superior properties compared with other carbon-based materials such as
carbon fiber, fullerene, graphite, and diamond such as good mechanical properties,
electric properties, and thermal properties as seen in Table 24.1. CNTs reach excellent
values in thermal, electric, and mechanical (tensile modulus or tensile strength) prop-
erties. For an instant, carbon fiber and CNT’s have a tensile modulus of 100–500 and
1000 GPa, respectively. Another crucial point is CNT content in a matrix material for
composite structure can be <0.5 wt% and for carbon fiber contents is higher than
10 wt% [4].
Having subnanodiameters, SWCNTs and MWCNTs are generally 0.8–2 and
5–20 nm, respectively. They can find an important place in different composite appli-
cation areas such as wind turbine industry, as a reinforcement material. In the past
decade, CNT-based commercial production has started to grow most extensively from
the time of 2006 CNT production capacity. Therefore, the increase in CNT production
capacity is 10-fold [15].
Firstly, CNTs were used as electrically conductive materials in polymers with very
low weight percent (0.01 wt%). Nearly 1 wt% CNT in epoxy resin shows an enhance-
ment in stiffness and fracture toughness by 6% and 23%, respectively [18]. CNTs’
diameter, alignment, dispersion, and interfacial interaction are the key parameters
to provide the improvement in structure properties [15]. The potential application
of polymers with CNTs in automotive, aerospace, defense, electronics, and energy
industry has been considered by Kingston et al. [19]. Due to its low density and
high-aspect ratio, adding CNTs to the thermoset polymers such as epoxy, polyester,
and vinyl ester exceptionally enhances the final mechanical properties [4]. In thermo-
plastic materials, the major target is to obtain high toughness and higher plastic elon-
gation to break with great stiffness and strength. In some excellent research [17,20],
CNT/polymer nanocomposites’ mechanical properties have been studied, and these
studies showed that CNT can enhance the modulus, strength, and toughness of poly-
meric materials. Commercially, fiber-reinforced polymers (FRPs) are used to fabri-
cate wind turbine blades. FRP is a composite material that consists of continuous
fibers and a polymer matrix. Fracture toughness and stiffness of blade materials
depend on polymer matrix [4]. In recent days, epoxy resin composites have become
prominent in wind energy application for manufacturing the larger wind blades due to
its low fracture toughness and fatigue resistance. Prepregs and vacuum-assisted resin
transfer molding (VARTM) processes are two techniques that are being used for
manufacturing the wind turbine blades [19]. CNT and epoxy mixing ration for
improving the elastic modulus, strength, and fracture toughness of CNT/epoxy
nanocomposites are reported as 24%, 20%, and 60%, respectively, by Geng et al.
[21]. Creating larger blades with long fatigue life, higher strength, and higher stiffness
is the aim of researchers and producers. The larger size of blades can harvest more
energy because of the swept area and high-power output obtains. Ma and Zhang
[4] have emphasized two ways including CNTs to improve the performance of blades
from FRPs composite. First, one involves adding CNTs into polymeric resin via suit-
able dispersion and processing, so the newly composed matrix will show better prop-
erties. The second one is the deposition of CNTs on the fiber surface. Because the
nanomaterials exhibit larger surface area, the high-interfacial interactions between