Page 710 - Polymer-based Nanocomposites for Energy and Environmental Applications

Carbon nanotube-based nanocomposites for wind turbine applications 653

toughening of the entire resin layer. Depositing nanofibers on preimpregnated com-
posite prepreg surface could cause incomplete toughening of the entire resin
layer [66].
Beckermann and Pickering [64] investigated the effects of interleaved nanofiber
veils on the mode I and mode II interlaminar fracture toughness (ILFT) of autoclave
cured unidirectional carbon/epoxy composite laminates. Various electrospun
nanofiber veils consisting of a range of different polymer types, fiber diameters,
and veil architectures were placed in the laminate midplanes that were subsequently
subjected to double cantilever beam and end-notch flexure tests. It was found that the
polymer type and veil areal density were the most important factors contributing to
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laminate performance. A 4.5 g/m PA66 veil provided the best all-around perfor-
mance with fracture toughness improvements of 156% and 69% for mode I and mode
II, respectively [64].
Li et al. [67] worked on the improvement of mode I fracture toughness for carbon
fiber/epoxy composites that include 60% carbon fiber and 40% resin. Polysulfone
(PSF)-based nanofibers with an average diameter of 230 nm were produced via
electrospinning technique and then directly spun onto composite laminates as seen
in Fig. 24.6.
PSF films were produced via solvent technique and compared with PSF nanofibers
with regard to morphology and toughening effect. SEM images showed that PSF
spheres that are obtained during curing process because of phase separation are dis-
tributed homogeneously in interleaves of carbon fiber/epoxy laminates that is not the
same with PSF film. The addition of 5.0 wt% PSF nanofibrous mat through interleaves
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of laminates increased the mode I fracture toughness (G IC ) to 0.869 kJ/m , which is
140% and 280% higher than toughened by PSF films and untoughened, respectively

Fig. 24.6 Schematic diagram of production procedure of PSF nanofiber-toughened carbon
composite: (A) carbon fiber/epoxy prepreg, (B) PSF nanofiber onto prepreg, (C) stacking of
prepregs, (D) composite molding, and (E) ILFT test specimen.
Courtesy of Li G, Li P, Yu Y, Jia X, Zhang S, Yang X, et al. Novel carbon fiber/epoxy composite
toughened by electrospun polysulfone nanofibers. Mater Lett 2008;62(3):511–4.