Stronger-than-steel ‘superwood’ created in US lab

SuperWood: Liangbing Hu (left) and Teng Li, a professor in mechanical engineering, worked together to create a material known as ‘superwood’.

Engineers at the University of Maryland have found a way to make wood 10 times stronger and tougher than before, creating a natural substance that is stronger than many titanium alloys.

The processed wood is as strong as steel, but six times lighter and takes 10 times more energy to fracture than natural wood. It can even be bent and moulded at the beginning of the process.

“This new way to treat wood makes it 12 times stronger than natural wood and 10 times tougher,” said Mr Liangbing Hu, associate professor of materials science and engineering member of the Maryland Energy Innovation Institute and leader of the team that did the research.

Hu felt that this product could be a competitor to steel or even titanium alloys as it was strong and durable and also comparable to carbon fibre, but much less expensive.

The research team even felt that soft woods like Pine or Balsa, which grow fast and are more environment-friendly, could replace slower-growing but denser woods like teak in furniture or buildings.

The process provides a highly promising route to the design of lightweight, high performance structural materials, with tremendous potential for a broad range of applications where high strength, large toughness and superior ballistic resistance are desired.

The method is versatile for various species of wood and fairly easy to implement. This kind of wood could be used in cars, aircraft, buildings or any application where steel is used.

Orlando J. Rojas, a professor at Aalto University in Finland felt that the most outstanding fact was the existence of a limiting concentration of lignin, the glue between wood cells, to maximize the mechanical performance of the densified wood.

Too little or too much removal lower the strength compared to a maximum value achieved at intermediate or partial lignin removal. This reveals the subtle balance between hydrogen bonding and the adhesion imparted by such polyphenolic compound.

Moreover, of outstanding interest, was the fact that that wood densification led to both, increased strength and toughness, two properties that usually offset each other, he observed.

Hu’s research has explored the capacities of wood’s natural nanotechnology. His team previously made a range of emerging technologies out of nano-cellulose related materials: super-clear paper for replacing plastic; photonic paper for improving solar cell efficiency; a battery and a super-capacitor out of wood; and transparent wood for energy efficient buildings.

These  wood-based emerging technologies are being commercialised through a university spinoff company, Inventwood LLC.

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