MATERIALS | COMPOSITES
NEW JOINTS REVOLUTIONISE COMPOSITES
A revolutionary new
technology developed by
the National Composites
Centre (NCC) and Oxford
Brookes University means composite
structures can now be separated
(or disbonded) quickly and cheaply
using a simple heat source. By
making it easy to work with, repair
and disassemble composite parts,
this world-leading research could
have a transformational impact on the
design, use and end-of life recycling
of wide range of products, including
cars, aircraft and wind turbines.
Researchers at Oxford Brookes
University demonstrated that by
adding low-cost additives to off-theshelf
structural adhesives, composite
parts could be separated in as little as
six seconds by raising the temperature
of the joint to approximately 160°C.
The National Composites Centre has
now proved that the new approach
works at an industrial scale as part
of the Technology Pull-Through
Programme, designed to transition
new ideas from the lab to the
marketplace.
Small quantities of expandable
graphite (widely used for fire
protection) or thermal expandable
microspheres are added to adhesives
routinely used to bond composite
parts. The additives have minimal
impact on the performance of
components in normal operation,
but when heated to the required
temperature exert a force causing
components to ‘pop apart’. This
means, in the near future, composite
components may be easily
repositioned and reused during
manufacturing – reducing waste,
repaired in operation and recycled
more efficiently at the end of their
working life.
“This is a really exciting
development, especially with
sustainability being an increasingly
significant challenge for the industry,”
said Lucy Eggleston, Research
World-leading research into
‘rapid heat popping joints’
makes composite parts easy to
dismantle, maintain and recycle.
Engineer at the NCC. “Historically,
when a part is damaged or reaches
the end of its life, it would be classed
as waste and discarded. With this
technology, we can take these
structures apart to be repaired,
reconfigured, or used in different
ways. This could increase available
end of life strategies for components,
ultimately reducing their impact on the
environment.”
The automotive sector, for example,
is looking to increase its use of
composites and bonded (glued)
parts in order to reduce vehicle
weight. Vehicles also have to be 85%
recyclable to comply with end-oflife
directives. The new technology
would allow mechanics to swap
damaged parts using a simple heat
gun. Recyclers could put whole cars
through low-temperature ovens and
watch them dissemble themselves in
seconds.
Other sectors that could benefit
include aerospace and renewables.
600 commercial aircraft are scrapped
in a typical year, with more modern
versions making extensive use of
expensive carbon fibre – up to 50%
of the weight of the vehicle in some
instances. Despite the value of this
material, the limitations of current
recycling technologies make it
uneconomic to recover. The same is
true for wind turbine blades, which are
typically made up of glass-fibre skins
with balsawood cores and metal or
carbon-fibre spars. It is estimated that
decommissioning the UK’s offshore
turbine farms, when they reach the
end of their operational life, could
be as high as c. £3.64bn, with up to
10,000 tonnes of turbine blades to be
disposed of every year by 2035.
Professor James Broughton, Head
of Joining Technology Research
Centre at Oxford Brookes University,
added: “We’ve been looking at ways
to disbond structural adhesives for
about 10 years, and working with the
NCC through the Technology Pull-
Through programme has enabled
us to prove the technology readiness
of our research. We can now work
with industry to fully optimise the
technology for specific applications
and tailor it for them as required.” !
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