CF/EP composite laminates with carbon black and copper chloride for
improved electrical conductivity and interlaminar fracture toughness
Donghai Zhang
a,b
, Lin Ye
a,
⇑
, Shiqiang Deng
a
, Jianing Zhang
a
, Youhong Tang
a
, Yunfa Chen
b
a
Centre for Advanced Materials Technology, School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, NSW 2006, Australia
b
State Key Laboratory of Multi-phase Complex Systems, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, China
article info
Article history:
Received 28 July 2011
Received in revised form 2 December 2011
Accepted 3 December 2011
Available online 11 December 2011
Keywords:
A. Laminate
A. Particle-reinforced composites
A. Polymer–matrix composites (PMCs)
B. Electrical properties
B. Fracture toughness
abstract
An experimental study was conducted to improve the electrical conductivity of continuous carbon fibre/
epoxy (CF/EP) composite laminate, with simultaneous improvement in mechanical performance, by
incorporating nano-scale carbon black (CB) particles and copper chloride (CC) electrolyte into the epoxy
matrix. CF/EP laminates of 65 vol.% of carbon fibres were manufactured using a vacuum-assisted resin
infusion (VARI) technique. The effects of CB and the synergy of CB/CC on electrical resistivity, tensile
strength and elastic modulus and fracture toughness (K
IC
) of the epoxy matrix were experimentally char-
acterised, as well as the transverse tensile modulus and strength, Mode I and Mode II interlaminar frac-
ture toughness of the CF/EP laminates. The results showed that the addition of up to 3.0 wt.% CB in the
epoxy matrix, with the assistance of CC, noticeably improved the electrical conductivity of the epoxy
and the CF/EP laminates, with mechanical performance also enhanced to a certain extent.
Ó 2011 Elsevier Ltd. All rights reserved.
1. Introduction
Continuous carbon fibre/epoxy (CF/EP) composite laminates are
well known for their high ratios of stiffness and strength to weight.
These desirable characteristics of CF/EP composite laminates have
resulted in numerous applications of the materials in areas where
high performance and light weight of structures are essential [1,2].
However, the mechanical performance of composite laminates in
the out-of-plane direction is normally much lower than that in
the in-plane direction, which can result in interlaminar fracture
or delamination in composite laminates.
Much effort and many techniques have been applied to improve
the interlaminar performance of composite laminates. Examples in-
clude the use of a toughened matrix, interlaminar toughening
through the incorporation of organic and inorganic particles in
the matrix or the addition of toughened polymer layers (i.e. inter-
leaving) between prepreg layers, and interlaminar strength
enhancement achieved by through-thickness stitching, Z-pins or
three-dimensional weaving [3–5]. Moreover, unlike their metal
counterparts, polymer matrix-based fibre composite structures in
aircraft applications cannot readily conduct the extreme electrical
currents or transfer the electromagnetic forces generated by light-
ning strikes. Although carbon fibres are electrical conductors, the
electrical conductivity of the epoxy matrix is very poor, with resis-
tivity being over 10
14
ohm cm [6], which commonly reduces the
conductivity of these composites, especially in resin-rich areas be-
tween layers. Currently, therefore, lightning strike protection for
composite airframes must be addressed using methods such as
incorporating metal meshes on the exterior to produce conductive
pathways in order to give lightning-induced current an ample num-
ber of routes to safely exit the aircraft. The similar issues exist for
composite structures used in other applications, such as the com-
posite masts of maritime vessels and the composite wind turbines
in wind energy generators. It is clearly highly desirable that com-
posite structures be made more electrically conductive, to avoid
or reduce the use of lightning strike protection materials [7–9].
It has been reported that the addition of conductive carbon par-
ticles such as graphite and carbon nanotubes (CNTs) can greatly in-
crease the electrical conductivity of polymers [10,11], and the use
of nano-sized particles such as CNTs can also achieve improvement
in the interlaminar fracture toughness of CF/EP composites [12].In
particular, research has shown that the incorporation of carbon
black (CB) can efficiently reduce the resistance of epoxies, espe-
cially when combined with the use of copper chloride (CC) as elec-
trolyte [10]. The conductivity of CNTs is certainly better than that
of CB. But because of their large aspect ratio, CNTs can be filtered
by dense CF bundles, making it difficult to use them in advanced
liquid moulding processes.
In this study, continuous CF/EP laminates with CB and CC were
fabricated to improve both interlaminar fracture toughness and
electrical conductivity. Unidirectional CF/EP composite laminates
were prepared using a vacuum-assisted resin infusion (VARI)
technique. CB particles with CC were used to obtain a percolation
0266-3538/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.compscitech.2011.12.002
⇑
Corresponding author. Tel.: +61 2 93514798; fax: +61 2 93513760.
E-mail address: lin.ye@sydney.edu.au (L. Ye).
Composites Science and Technology 72 (2012) 412–420
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