Page 711 - Polymer-based Nanocomposites for Energy and Environmental Applications

654 Polymer-based Nanocomposites for Energy and Environmental Applications

1.2

1.0 (B)

0.8 (C)
G IC (KJ/m 2 ) 0.6

0.4
(A)
0.2

0.0
40 50 60 70 80 90 100
Crack length, a (mm)
Fig. 24.7 Fracture toughness and crack length relation of composites: (A) untoughened,
(B) toughened by PSF nanofibers, and (C) toughened by PSF films.
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.

(Fig. 24.7). The reason behind this increase is the homogeneous distribution of PSF
spheres in interleaves of laminates [67].
Zhang et al. [66] produced polyetherketone cardo (PEK-C) nanofibers by using
electrospinning technique to increase the interlaminar fracture toughness of compos-
ites. PEK-C nanofibers were used as interlayers to toughen carbon fiber/epoxy com-
posite. PEK-C nanofibers were directly electrospun to one side of the dry carbon
fabric. The influences of nanofiber diameter and loading thickness on the mode
I delamination fracture toughness, flexure properties, and thermal mechanical prop-
erties were examined. By depositing PEK-C nanofibers with weight loading of just
0.4 wt%, interlaminar fracture toughness has been increased. The finer the nanofibers,
the more stable the crack propagation and better mechanical performance under flex-
ural loadings. Fracture toughness improved with increasing nanofiber interlayer thick-
ness. However, flexure performance compromised. Carbon fiber-reinforced thermoset
matrix composites are in use as structural components for various applications like
automotive, aerospace, and marine industries. Low velocity and fatigue are significant
cases for these types of high-performance composites. The big challenge for these
types of thermosetting composites to be used for long term faithfully is the delamina-
tion resistance and fracture toughness [66].
Carbon fabrics with one side deposited with PEK-C electrospun nanofibers were
laid up with epoxy resin (epoxy/carbon 1:1, wtto wt). The composite laminates
[0/90] 4 were finally cured in a hot press at 175°C for 3 h. As a control, a composite
laminate without electrospun nanofiber interlayers was prepared using the same
process. To achieve 0.44% weight fraction of PEK-C nanofibers in the composite
laminates, the electrospinning time for different polymer concentrations varies.