Engineers at the University of Maryland have found a way to make wood more than 10 times stronger and tougher than before, creating a natural substance that is stronger than many titanium alloys.
“This new way to treat wood makes it twelve times stronger than natural wood and ten times tougher,” says Liangbing Hu, leader of the team that conducted the research, published in Nature.
“This could be a competitor to steel or even titanium alloys, it is so strong and durable. It’s also comparable to carbon fiber, but much less expensive.
“It is both strong and tough, which is a combination not usually found in nature,” says Teng Li, the co-leader of the team and the Samuel P. Langley professor of mechanical engineering at the University of Maryland. His team measured the dense wood’s mechanical properties.
“It is as strong as steel, but six times lighter. It takes 10 times more energy to fracture than natural wood. It can even be bent and moulded at the beginning of the process.”
The team’s process begins by removing the wood’s lignin, which is the part of the wood that makes it both rigid and brown in colour. It is then compressed under mild heat, at about 65°C. This causes the cellulose fibers to become very tightly packed. Any defects like holes or knots are crushed together, and the treatment process was extended a little further with a coat of paint.
The scientists found that the wood’s fibers are pressed together so tightly that they can form strong hydrogen bonds, like a crowd of people who can’t budge – who are also holding hands. The compression makes the wood five times thinner than its original size.
The team tested their new wood material and natural wood by shooting bullet-like projectiles at it. The projectile blew straight through the natural wood. The fully treated wood stopped the projectile partway through.
“Soft woods like pine or balsa, which grow fast and are more environmentally friendly, could replace slower-growing but denser woods like teak, in furniture or buildings,” says Hu.
“It is particularly exciting to note that the method is versatile for various species of wood and fairly easy to implement, says Huajian Gao, a professor at Brown University who was not involved in the study.
“This kind of wood could be used in cars, airplanes, buildings – any application where steel is used."
“Given the abundance of wood, as well as other cellulose-rich plants, this paper inspires imagination," says Zhigang Suo, a professor of mechanics and materials at Harvard University, also not involved with the study.