New 'super wood' is 10 times stronger, could replace steel say scientists
February 9, 2018 | 2:10 pm CST
COLLEGE PARK, Md. -- University of Maryland (UMD) scientists have named it "super wood" and rightfully so, as they say it is over 10 times stronger and tougher than regular wood.
"This new way to treat wood makes it twelve times stronger than natural wood and ten times tougher," says Liangbing Hu, leader of the research team. "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."
The wood is reportedly just as strong as steel, but six times lighter in weight and five times thinner than the original piece. It takes 10 times more energy to fracture than real wood.
But how does it work?
The process begins by removing the wood's lignin. It is then compressed under mild heat, at about 150 degrees Fahrenheit. The cellulose fibers become tightly packed - crushing any potential defects like holes or knots together. Strong hydrogen bonds are formed. The treatment process is extended further with a coat of paint.
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.
“Softwoods 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,” Hu said.
“This 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, “ said Dr. Huajian Gao, a professor at Brown University, who was not involved in the study. “It is particularly exciting to note that the method is versatile for various species of wood and fairly easy to implement.”
“This kind of wood could be used in cars, airplanes, buildings – any application where steel is used,” Hu said.
“The two-step process reported in this paper achieves exceptionally high strength, much beyond what [is] reported in the literature,” said Dr. Zhigang Suo, a professor of mechanics and materials at Harvard University, also not involved with the study. “Given the abundance of wood, as well as other cellulose-rich plants, this paper inspires imagination.”
“The most outstanding observation, in my view, is 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, is the fact that that wood densification leads to both, increased strength and toughness, two properties that usually offset each other,” said Orlando J. Rojas, a professor at Aalto University in Finland.
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