Smart Foam Protects Skiers

The gates that dot a ski slalom course may give upon impact. But the gates don't feel so forgiving to the world-class skiers who sometimes strike them at 60 mph or more. Spyder, a maker of technical ski wear, recently found a way to take some of the sting out of gate contact by incorporating a novel impact absorbing material into the race suits worn by skiers on the U.S. and other national teams.

Made by d3o Lab, the impact-resistant material is a microcellular foam partly composed of a shear-thickening, or dilatant fluid. These materials increase in viscosity with increasing shear rates. In foams, the shear thickening translates to increased stiffness upon impact. The stiffening takes place in just a few milliseconds and increases the reactive force that counters an impact, explains Richard Palmer, d3o's CEO. When the impact event ends — and shear rates drop — the material returns to its more flexible state.

At this stage in the game, it's difficult to say just how much stiffer the materials become. Palmer points out that the dynamic stiffening of these foams is complex. It involves not just the rate at which impact force is applied, but also the pneumatic effects of the closed foam cells and the role of displacement. "Dynamic stiffening is a Ph.D.-level challenge," he says.

But it's a challenge d3o is working on with some help from Instron Corp. Palmer says the companies are developing "a bespoke set of test equipment and methods" that should allow them to quantify the dynamic stiffening of d3o's materials. In the meantime, the company has done some impact testing using standard methods from the footwear industry.

	Spyder’s ski racing suits are the first to incorporate an impact-resistant “smart foam” developed by d3o Lab.

Shear thickening materials, such as those used by d3o, are hardly new. "But they have to be encapsulated to be useful in real-world applications," says Palmer. "In the past, encapsulation spoiled the very material properties we're after."

That's where d3o's proprietary technology comes in. The company's scientists have figured out a way to encapsulate the shear thickening material in an elastomeric matrix that doesn't destroy the dilatant properties. The resulting composite material is suitable for casting into shapes that can be incorporated into a variety of products that require both flexibility and impact protection.

In Spyder's case, the d3o material has been placed at contact areas such as forearms and shins. d3o also has other sporting goods applications in the works, including skateboarding shoes, knee guards for polo players and gloves for soccer goalkeepers. And while, d3o is currently focused on sports applications, Palmer doesn't rule out military, industrial and even automotive applications in the future.

For more information on d3o's materials and manufacturing methods, visit www.d3olab.com.