JEC COMPOSITES MAGAZINE - Special Issue Smart Cities - November 2019 - 10

PROCESSING structural power composites
damage influence electrochemical
performance?), provide a tool for parametric studies and, ultimately, support
certification of structural power components.
A promising strategy for structural supercapacitors is to combine traditional
reinforcing fibres with nanostructured
fibres. With an electrical conductivity
superior to that of carbon fibre (≈105
S/m) and roughly 1000x more specific
surface area, unidirectional non-woven fabrics of carbon nanotube fibres
(CNT) can simultaneously perform
electric double-layer capacitive storage and current collector functions
(Figure 3). Structural supercapacitors
can be produced by integrating CNT
fibre fabrics, a polymer electrolyte and
a conventional fibre fabric, followed
for example by vacuum bag resin infusion. To adjust the balance between
structural and energy-storing functions, the electrochemical double-layer capacitor layer is pre-patterned using designs optimised via mechanical
simulations of interlaminar properties.
By monitoring the electrochemical
properties during mechanical testing,
complete tolerance against large deflections (Figure 3) is observed, with
capacitance remaining stable after
fatigue tests compared with a 50% reduction in performance for reference
embedded devices (i.e. a multifunctional structure). The mechanical and
electrochemical robustness of these
composites is a consequence of the
multifunctional material approach
used, whereby materials and interfaces
are designed to favour interfacial stress
transfer and reduce interfacial electrical resistance.
Industrial outlook
and closing remarks
Throughout the development of
structural power materials, the
SORCERER team cooperated with
industry to produce demonstrators
to pull through this technology. For
example, the STORAGE project [7]

Fig. 4: a) Volvo S80 composite bootlid with four stacks of four structural supercapacitors within;
b) fuselage C-beam multifunctional demonstrator replacing a supercapacitor bank

developed a multifunctional boot lid
for a Volvo S80, which contained four
stacks of four structural composite supercapacitors (Figure 4a). In addition
to providing electrical power, this led
to a weight reduction from 13 kg (conventional boot lid) to 5.2 kg. In the
current SORCERER project, the team
is developing several demonstrators,
including a multifunctional C-section
fuselage beam that will replace an existing supercapacitor bank in the aircraft cabin (Figure 4b).
However, considerable hurdles still
need to be overcome for structural
power to be fully adopted by industry. Fundamental challenges include
improved understanding of the interaction between electrical and mechanical behaviour, performance at temperature extremes and durability. Practical
issues, such as accessibility, replaceability, sensing and battery management, will also have to be addressed.
A particular challenge associated with
aerospace is addressing the certification of structural power materials
such that they are deemed airworthy.
Ultimately, current developments of
structural power composites represent
the first steps in an exciting vision in
which equipment, transportation and
infrastructure will contain their own
energy supply as their mechanically
load-bearing structure.
More information:
e.greenhalgh@imperial.ac.uk
References
[1] Kjell M.H., Jacques E., Zenkert D.,

jec composites magazine / SPECIAL ISSUE Smart Cities / November 2019

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[6] Nguyen S., Anthony D., Qian H.,
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[7] https://cordis.europa.eu/project/
rcn/93371/factsheet/en

https://cordis.europa.eu/project/rcn/93371/factsheet/en

JEC COMPOSITES MAGAZINE - Special Issue Smart Cities - November 2019

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