In recent research, engineers at the University of Colorado Boulder and Sandia National Laboratories have developed a new pad design that can withstand huge impacts. The team's innovation can be printed on commercially available 3D printers and could one day be used in anything from shipping boxes to football pads that help protect fragile objects or the human body from life's knocks.

In laboratory tests, the newly designed pad (pictured on the right) outperformed more traditional technologies such as foam made from the same elastic material (pictured on the left). Source: Lawrence Smith

The team describes the technique in a paper recently published in the journal Advanced Materials Technology.

Robert MacCurdy, corresponding author of the study and assistant professor in the Paul M. Rady Department of Mechanical Engineering at CUHK-Boulder, said: "Impact mitigation is important everywhere. This material is found in highway crash barriers, knee and elbow pads, and packaging equipment."

This study takes a fresh look at something that most people encounter often but rarely notice: bubbles. They are soft materials filled with countless small holes and channels. Just like packing peanuts or stress balls. MacCurdy says foams absorb impact very well, but they have a big drawback: If you squeeze the foam too hard, it will eventually compress into a hard mass.

In laboratory experiments, engineers at CUHK-Boulder used 3D printing technology to print newly designed pads and then crushed them with a powerful machine. The team's creation withstood impact, absorbing several times more energy than traditional designs or foams made of the same materials. Source: Lawrence Smith

He and his colleagues thought they could do better. In the new study, the team wrote computer algorithms that carefully redesigned the internal structure of cushioning materials -- allowing them to fold when stressed, but only in carefully designed patterns. When the team tested their design in the lab, they found that their pad could absorb up to 25 percent more force than current state-of-the-art technology. "The materials used to absorb impact are important," MacCurdy said, "but what really matters is the geometry."

To understand why some cushions work well and others don't, for example, it's those little nooks and crannies that give a sponge its elasticity. When you squeeze the sponge, these gaps begin to close, absorbing energy.

Some engineers have gone beyond this basic design. Instead, they create the padding with a network of hexagonal towers or "lattice" that look a bit like honeycombs. If a defender hits this cushioning, the impact causes the honeycomb to collapse in a wave-like pattern. This is a more effective method of absorbing force.

But MacCurdy points out that researchers have long struggled to find pads that meet the gold standard — technology that can absorb not just a lot of force, but many different forces with the same skill.

"If you have a crash while riding your bike, you don't know if it was a low-speed impact or a high-speed impact. But regardless, you want the helmet to perform well," he said. "We are trying to develop a geometry that performs well in all these situations."

To create a more versatile mat, the engineer and his colleagues chose to rearrange the objects' internal structures, down to as small as a millimeter.

The team first laid out the cellular network using custom software, then tweaked it to add a few kinks, a bit like the bellows in an accordion. During impact, these kinks help guide the honeycomb downwards, allowing it to collapse more smoothly.

"When you start compressing these structures, they absorb a certain amount of force," MacCurdy said. "The best absorber designs maintain a constant force throughout the entire range of compression."

In other words, unlike foam, these pads will not change no matter how much you press them, or at least not beyond a certain maximum value.

The researchers also wanted to make sure their pads could withstand real-world knocks and bruises. They used a 3D printer to create small brick-sized pads from an elastic material called thermoplastic polyurethane. They then squeezed it with an impact testing machine.

The research team found that its blocks absorbed approximately six times more energy than standard foam made of the same material, and up to 25% more energy than other honeycomb designs. MacCurdy and his colleagues are currently working to further improve their structure. He added that engineers can make such designs out of many different types of materials, from flexible plastics to harder substances like aluminum.

Compiled source: ScitechDaily