Technology demonstrated by researchers at the National Composites Centre in Bristol promises to make it easier to dismantle, repair and recycle composite parts.
Developed in collaboration with a team from Oxford Brookes University, the technology – which involves the use of carefully modified structural adhesives – enables composite structures to be separated (or disbonded) quickly and cheaply using a simple heat source.

It is claimed that the research could have a transformational impact on the design, use and end-of-life recycling of products including cars, aircraft and wind turbines.
Project leader, NCC research engineer Lucy Eggleston, said that the group has explored the use of two specific off-the-shelf additives which can be added to any structural adhesive.
The first of these additives, expandable microspheres, have been explored before for disbonding applications, but never for industrial scale applications. These are effectively thermoplastic bubbles containing hydrocarbons with relatively low boiling points, explained Eggleston.
“When they’re exposed to heat the thermoplastic bubble becomes malleable and stretchable and the hydrocarbons boil and expand,” she said. “That causes the whole bubble to expand which, when used as part of a joint, causes two surfaces to push apart from one another and breaks apart an adhesive bond.”
The second additive, expandable graphite, which has never before been explored for this application, works in a slightly different way, she added.
“We use these stacks of graphite with really thin carbon layers between these graphite plates. When they’re exposed to heat those oxidise and that causes expansion. That expansion forces the joined parts apart from each other.”
During trials of the technology the team demonstrated potential applications on a battery box supplied by Williams Advanced Engineering.
“We designed three different features that would be industrially relevant, bonded them together and demonstrated that application of this technology by releasing all of those different parts,” said Eggleston.
A number of different heat sources were trialled, including a bespoke induction coil that could and also be used on a disassembly line, an infrared lamp, a heat gun and an oven. The induction coil method was able to disbond a joint in just six seconds, whilst the IR lamp and heat gun took slightly longer.
By enabling composite components to be easily repositioned and reused during manufacturing – and simplifying repair and recycling processes – the technology should, said Eggleston, lead to far more efficient use of composite materials.
“We’re seeing a greater emphasis on sustainability and end of life and being able to reuse what you’ve made, or repair what you’ve got, as opposed to just creating a new one and this is one of those enabling sustainable manufacturing technologies.”
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Carbon footprints: inside the National Composites Centre
She added that it could also help drive the increasing use of adhesives, which are attractive for a number of reasons but which still have drawbacks.
“We’re seeing a move away from bolted joints. They take a long time to put together, increase the weight of a structure, and if you want to take them apart at end of life they take a long time as well. Using a quick cure adhesive is a lot faster and more economically feasible than using bolts. But the problem with those permanent adhesives is that you can’t just take them apart if you get something wrong. With a technology such as this you get the best of both worlds.”
This, she added, could in turn have an impact on the design of composite components. “We’ve been talking to a number of customers and members about design for disassembly – and I think this is one of those key technologies that’s going to enable a lot of that. It’s going to expand the design envelope and give the designers a little bit more freedom when it comes to how they make sure something is structurally sound and reliable but also has this added bonus at end of life or during use.”
Run as part of NCC’s technology pull through programme – which is aimed at accelerating the commercialisation of promising university research projects – the composite disbonding initiative has already generated a high level of interest.
Eggleston said that NCC customers and members had already identified a range of potential applications including helping the auto industry meet the end of life vehicle directive and enabling the wind energy industry to segment turbine blades more easily.
“There’s a huge amount of applications, which is quite interesting for a single, quite simple technology,” she said.
Despite the range of potential applications, she added that use of the technology would clearly be limited to environments where operating temperatures are relatively low.
“If you’re sticking together bits of an engine you probably don’t want to be using this technology. But for external bits of a car, internal bits of aircraft, and bits of wind turbine…there are a number of applications that don’t see those sort of temperatures at which the use of these is perfectly OK.”
Eggleston and the team are now looking at taking the technology to the next step and investigating a number of specific applications.
“We’ve got a couple of customers who are looking to progress this further with us,” she said. “We’re looking to optimise the technology further for their specific applications and work with them to ensure that the technology can deliver everything they need it to.”
Then along comes real life; have they thought about inadvertent application of heat to bonds during operations, or deliberate action to break through by bad people, and so on? A car body delaminating as you are driving along could be interesting for spectators, but not so good for you.
As mentioned in the article this has been considered
Quite ingenious incorporation of thermoplastics.
But would it not be better to go the whole hog and go for thermoplastic composites? Which would allow easier forming (and re-forming) and repair-ability – not to mention recycling (easier to separate a thermoplastic from its reinforcement – rather than a glue or thermoset, which the rest of the structure would still be?)
The HAWT is the wrong design choice for offshore installations. Two maxims, ‘prevention is better than cure’ and KISS should apply to composite blades no less than to Covid-19.
“A successful circular economy can only exist if it relies solely on renewable energy sources. The adoption of resilient business models and the consequent redesign of legislation in all sectors are essential to ensure sustainable economic growth.” A total installed capacity 3x peak demand is not a viable business model. An offshore service life of 25 years, which entails blade repairs, can never be a sustainable O&M model and 10MW turbines have no future.
“Composite materials are used in wind turbines due to their excellent mechanical properties and low weight, but the recycling technologies are limited.” The inherent high load reversals on HAWT (cantilevered) blades get worse as they get bigger; ergo, switch to low c of g floating VAWTs with cheap, extruded aluminium blades. (The close spacing of VAWTs enhances energy harvest too.)
“Wind turbines are often erected in remote areas, in order to exploit better wind conditions. The cost of failures and repairs can be substantial. Ensuring the lightning performance of the turbines and especially of the blades has become very important.” The current cost of blade repairs and O&M is substantial, not to mention the failures in vulnerable HV installations at sea.
EU and UK (neoliberal) governance is at fault for ‘designing’ the market interventions (rigging) that have created the expensive problems of an unsustainable electricity supply system.
https://www.theengineer.co.uk/competition-mitigate-windfarm-radar-risk/
I offered the ‘preventive’ solution to NG’s 2009 consultation on “The Impact of Intermittency “. It featured a hybrid of these two VAWTs:-
https://wwwdotyoutubedotcom/watch?v=cYh7jR4vLQg
National Grid – “The Power of Action.” – In actual fact we see; The Consequences of Inaction. . .
Operating the Electricity Transmission Networks in 2020.
Follow Up Report. February 2010:-
Question 38: Are there further aspects of storage or other storage technologies we should consider when looking forward to 2020? – Page 27 of 28.
“One respondent commented that investment would be stimulated if NG identified a requirement for storage. Another argued strongly that storage could be integrated into intermittent generation installations thus ELIMINATING a range of issues raised within the consultation document.”
“We will continue to discuss provision of Balancing Services from different storage technologies with parties interested in developing storage facilities.” Don’t forget, NG excuses itself from R&I in energy storage – UK legislation forbids it from generating electricity! (That doesn’t apply to EDF.)
While the ‘experts’ were only concerned about ‘back-up’ for when the wind’s not blowing, nobody realised the opposite scenario – when supply exceeds demand – is just as problematic!
https://www.theguardian.com/business/2020/apr/16/low-demand-for-power-causes-problems-for-national-grid
With Before-Generator Energy Storage, thousands of kilometres of sub-sea cable are redundant.
Ofgem takes NO action on energy storage, but they said the use of single radial links from wind farms to land won’t be “economical, sensible or acceptable.” – SSE plough on regardless!
https://renews.biz/59673/sse-unveils-roadmap-for-40gw-offshore/
“Some offshore wind projects have taken a decade to develop.” In the case of Hywind, 2 decades – wasted on the wrong design! “These timelines will absolutely not work for the ramp up in offshore wind needed. Our roadmap set outs 9 actions needed to ensure we don’t look back with regret in 2030 to see that we didn’t take the steps needed to achieve the 40GW target.”
7 out of 9 of those actions will “absolutely not work”. Without energy storage 40GW is the wrong target (over-capacity), grid operation is inefficient and the “market design” is broken. The circular economy will “absolutely not work” using composite blades offshore – period.