Self-healing composites inkjet printed
Simon Frost talks to Dr Patrick Smith about a new advance in self-healing materials.
Inkjet printing and composite materials are being combined to improve the structural integrity of lightweight, self-healing materials by researchers at The University of Sheffield. A team led by Professor Alma Hodzic and Dr Patrick Smith has developed a process that involves depositing low-viscosity thermoplastic microdroplets onto fibre-reinforced epoxy pre-pregs, before curing and solidification. These microdroplets form a self-healing agent that is arrested between composite plies, preventing direct contact with neighbouring microdroplets. The material’s self-healing properties are activated by external heat to re-fuse the composite layers. Dr Smith explains, ‘Carbon fibres are increasingly being looked at as structural components for their light weight to high strength. The downside is that the material is very brittle, so by adding these polymer agents we’re able to improve some of the mechanical properties’.
The study is being sponsored by the US Air Force Office of Scientific Research. The primary application of the material is for structural components in aircraft structures and automobiles, but Dr Smith describes a more unusual potential use for the technology. ‘One application is in exoskeletons. That might sound a little sinister, but a soldier, for example, carries an awful lot of weight. If they had an exoskeleton, they would have a system that would actually help them carry the weight and protect them.’ This use could cross over into the civilian realm, too. ‘With an ageing population, exoskeletons could help elderly people look after their partners. If one is less nimble, the other might have to do some carrying. Some sort of exoskeleton to wear for such applications could offer a better quality of life.’
Dr Smith expects work on this study to continue for the next three to four years, and research in the new field of composites in inkjet printing could go on for much longer. ‘Because we’re using an additive manufacturing technique, we’re not tied to just printing the same pattern in specific regions all over the pre-preg. We can start to select the pattern so we can toughen some regions and leave others un-toughened, and maybe we can start to direct crack propagation.’