Inkjet technology is noted for being innovative. This is hardly news. Neither are inkjet printed composites that possess self-healing properties, according to Dr Patrick Smith at the University of Sheffield. Although to me, the principle of being able to print something that can fix itself is staggering.
During a conversation with Patrick, I had to ask, what exactly does self-healing mean and what is meant by inkjet printed composites?
Inkjet printing is used to position droplets of polymer on a substrate of pre-preg. Pre-preg is a floppy sheet that is composed a woven carbon fibre mesh and an epoxy matrix. Stacks of pre-preg are baked to produce the tough carbon fibre composite that we are all familiar with.
However, although light and strong the carbon fibre composite is quite brittle and through use and by absorbing forces, it may fracture, forming small micro-cracks. If these microcracks are untreated they will grow leading to catastrophic failure of the bulk composite. The composite will simply break if it does not have self-healing properties. With the system developed at the University of Sheffield, the application of heat causes the printed polymer to flow and fill in the microcracks.
Ideally, the composite should be able to withstand forces, not forming microcracks in the first place. The system developed by Patrick and his colleague Professor Alma Hodzic results in a composite that has increased interlaminar fracture toughness (~30 – 50%) and that retains stiffness.
Up to now there has always been a trade off with producing a composite with self-healing properties, the introduction of self-healing systems, such as micro-beads that rupture and heal the fracture, into the composite material increases the weight of the composite.
”One of the key values of the inkjet printed composite is that its light weight is retained, it is lighter and beneficial for an array of applications.”
And according to Patrick and his colleagues Professor Alma Hodzic at the University of Sheffield, this composite is now feasible. It retains its self-healing characteristics but it does not require heavier micro beads to be introduced.
Imagine what this could mean to the production of cars, planes, trains? This could dramatically reduce weight whilst enhancing the strength and safety of a vehicle, reducing fuel consumption and increasing sustainable performance.
Additionally, the applications have tremendous value for the elderly as exoskeleton structures can be created, to suit a specific body shape providing elderly people with the support they need in order to remain mobile.
The European Office of Aerospace Research & Development has been behind this exciting breakthrough from the start for inkjet printing, principally for aeroplane and automobile production – but the applications are potentially widespread and game-changing.
So we look forward to seeing this develop into the future and perhaps seeing and hearing about it at the InPrint Show.
For further information contact: Dr. Patrick J. Smith PhD (Cantab). BSc MRSC MInstP
Telephone: +44 (0)114 222 7738