Super Wood Is Stronger Than Steel

SCIENCE

Densifying lumber can increase its strength tenfold. (Popular Mechanics)

Learn more about this eco-friendly renewable resource here.

Teachers, scroll down for a quick list of key resources in our Teachers Toolkit.

A new “densification” treatment can toughen soft woods like this pine to the strength of steel.
Photograph by David Boyer, National Geographic

Discussion Ideas

  • How have scientists created a “super wood” that is stronger and more durable than metal? Read through the great Popular Mechanics article for some help.
    • densification. Researchers used an innovative two-step process to increase the wood’s density.
      • First, scientists boiled different types of wood—oak, poplar, basswood, cedar, and pine—in a solution of sodium hydroxide and sodium sulfite for seven hours.
        • That treatment left the wood’s starchy cellulose mostly intact, but created more hollow space in the structure by removing components such as lignin, a substance that makes wood rigid and brown—what Popular Mechanics says “makes wood wood.”
      • Second, scientists pressed the block at 100° Celsius (212° Fahrenheit) in a process Nature likens to making “a panini sandwich.”
        • The process compresses the cellulose and shrinks the size of the wood, making it one-fifth its original thickness. It also removes defects like holes and knots.
        • The densified wood is 11.5 times stronger than untreated wood.
      • Other methods of densifying wood include applying higher temperatures, steaming the wood before treatment, and applying resins.

 

  • How did researchers test the densified wood’s strength? Take a look at the video above for some help.
    • They fired a gun! Three millimeters of the densified wood was able to halt a 46-gram steel projectile traveling at roughly 30 meters (98 feet) per second. Researchers compare this speed to the speed at which a car might be moving before a collision.
    • Researchers also tested the “scratch resistance” of the densified wood using a “linear reciprocating tribometer”, a diamond-tipped device that tests the hardness of a substance.
    • Other tests measured the densified wood’s ability to withstand moisture and the energy absorbed during the substance’s fracture.

 

 

 

TEACHERS TOOLKIT

Popular Mechanics: New Chemical Treatment Makes ‘Super Wood’ That Could Replace Steel

Nature: Crushed wood is stronger than steel

Nat Geo: Truly Alternative Energies: Biopower

Nat Geo: What is biomass energy?

(extra credit!) Nature: Processing bulk natural wood into a high-performance structural material

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