Maryland Uni develops method to transform strength of wood to be comparable to composites

Wooden bicycle maker Renovo had a torrid time at Interbike’s Outdoor Demo in 2016.

Researchers at the University of Maryland have developed a technique to transform the properties of natural wood to create a material that is comparable in strength to some titanium alloys, as well as composites.

Use of natural woods and bamboo in bicycle manufacture is no new thing, with manufacturer’s achieving mixed results to date. The benefits from a manufacturer’s point of view have largely been cost related, however, given the artisan construction, retail prices haven’t always reflected that to the consumer. Benefits further include vibration absorption and stiffness in certain directions.

The latest breakthrough appears to have some differences, however. Dubbed ‘Super Wood’, the natural wood is put through a two-step process, beginning with a boiling process in a solution of sodium hydroxide (NaOH) and sodium sulfite (Na2SO3). Not too dissimilar from the process used to obtain the pulp used to create paper, this chemical process partially removes select natural polymers that stiffen a plant cell’s walls. The wood’s cellulose largely remains, explains researcher Liangbing Hu.

Secondly, the process compresses the wood until its cell walls collapse, before heating is applied. This combination of pressure and heat bonds hydrogen atoms with nanofibers of cellulose, vastly strengthening the material.

Having published their findings in Nature, Hu said in a press statement: “This new way to treat wood makes it twelve times stronger than natural wood and ten times tougher. 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.”

Could ‘Super Wood’ have bicycle applications?

The early findings seem to offer promise. The finished article is more than 50 times more resistant to compression, 20 times as stiff, more impact resistant and able to be molded into almost any shape. It’s also naturally moisture resistant, so carries less risk of deformation over time. Lab tests demonstrated a less than 10% swelling over five days of extreme humidity exposure. A coat of paint eliminated swelling.

Another enormous benefit is the obvious sustainability benefits, with composites much harder to recycle, though many do.

The team’s results “appear to open the door to a new class of lightweight materials,” says Ping Liu, a materials chemist at the University of California, San Diego.

Catch the findings in full here.

Related: How silkworms fed on graphene could assist in producing crash resistant smart fabrics for cycle wear.