The Most Welcome Mat Ever—Blast Mat Absorbs 70% of the Impact of Roadside Bombs

SKYDEX fashions an infinite number of solutions to with materials and design for impact mitigation.

A troop carrier outfitted with a blast mat to protect against the shock of an IED explosion. (Picture courtesy of SKYDEX.)

Roadside bombs, aka IEDs (improvised explosive devices) were used by insurgents against military vehicles in Iraq and Afghanistan with devastating results. Soldiers resorted to “hillbilly armor,” welding scrap steel onto their vehicles for protection. It wasn’t enough. Troops that survived the blasts seemingly intact complained of an excruciating pain in their feet. They couldn’t walk, stand, much less run, making them useless for future missions and disabled for the rest of their lives. Many found the pain so unbearable that they opted to have their feet amputated.

Military doctors were scratching their heads … until they remembered sailors in World War II encountering somewhat similar effects from torpedo explosions.

The explosions that occurred underneath ships resulted in impact to the sole of the sailors’ feet, immediately and most forcefully felt by calcaneus, aka, the heel bone, one of the 26 bones in the human foot. Directly under the tibia and bearing the full weight of a standing person and a significant portion of the leg weight of a sitting person, the bone feels the impact to the foot most severely.

An engineer seeing a heel bone will perhaps question its design. You would have designed it with a flat bearing surface on the bottom to distribute the load—not a rounded tip. You know that stresses between a round hard surface and a flat one—a steel deck, for example—will approach infinity. Your heel bone would push all soft tissue aside, literally pop through your skin the first time you put weight on it. What prevents this from happening? Enter a part of your anatomy that you never knew you had: the fat pad.

If you have not heard of a fat pad, you are lucky. A fat pad will only make you aware of its existence if it is in distress. Fat pads are encapsulated adipose tissue, but unlike any fat you know. Unlike the firm fat that you trim from your steak (visceral fat) or the semiliquid subcutaneous fat that is removed by liposuction, fat pads are dense and tough. In the foot, the calcaneal fat pad, the toughest of all your fat pads, works like a felt pad you would use under metal table legs so they don’t scratch your wooden floor.

Fat pads exist in several places in your body. You have fat pads behind your kneecaps (infrapatellar fat pad). [Ed. note: unless you have foolishly worn them away with many marathons.] You will generally not be aware of fat pads unless they become damaged, either from wear or direct impact. Until then, fat pads rest in obscurity, routinely ignored even in medicine. Their display faintly like ghosts in X-rays. Nursing students dissecting cadavers discard fat pads as detritus on their way to naming bones, nerves, organs, blood vessels, and so on.

The fat pad in the heel of the foot can accommodate quite a bit of repeated shock, even the harsh pounding from running on pavement, but it is no match for the blast of a roadside bomb. An IED blast has proven to be more severe than torpedo blasts, and more likely to result in fractures of the calcaneus (45% of the cases vs 25% with torpedo blasts).

Inflamed heel fat pad syndrome or inflammation. (Picture courtesy of Sumer’s Radiology Blog.)

The U.S. military, in response to injuries to service members’ feet and backs from roadside bombs, commissioned SKYDEX to make blast mats to mitigate the impact from these blasts. The blast pads that resulted are now standard equipment in troop carriers.

A SKYDEX layer and twin-hemispheres before and after an impact. (Picture from Computational Modeling of the Crushing Behavior of SKYDEX Material, from paper by Binhui Jiang, et Al., June 2013, courtesy of Elsevier.)

A look at the internal structure of a blast mat reveals multiple shapes and materials. Most of the thickness is taken by gray thermoplastic polyurethane shapes that look like egg cups joined at their small ends. The shape of the egg cups withstands normal loading, such as troops walking and sitting. But the blast from a 6 Kg (13 lb) of TNT will register forces of over 3700 N (830 lbf) on the floor, according to one study, and will crush at least of the egg cups, absorbing as much as 70 percent of the force from a blast. After experiencing a blast, service members’ ears may still be ringing and their bodies might be bruised, but thanks to the blast mat, they can walk into their next mission, or civilian life, without pain.

The troops that can walk without pain after a blast owe this company one big “thank you” for developing the blast pad.

We talked to Alvaro Vaselli, the CEO of SKYDEX. Vaselli earned a bachelor’s degree in production and mechanical engineering from Faculdade de Engenharia Industrial and a master’s degree in marketing from Escola Superior de Propaganda e Marketing, both in São Paulo, Brazil.

Alvaro Vaselli, CEO of SKYDEX. (Image courtesy of Thrive Global.)

Vaselli has been named in our Engineers Who Mattered in 2020 for his role in safeguarding our soldiers and athletes.

Alvaro, can you tell us about your engineering background?

I’m an engineer by education. I have a passion for engineering and for innovation. I spent quite a bit of time with R&D as part of a two-year rotation. And then I ended up doing sales and marketing. And I really liked the business part and business development.

How did SKYDEX start?

The company has been around for 20 years. It really started with one pattern for thermoplastic urethane combined with geometry for impact mitigation in footwear. We were sought by the government to help with impact mitigation for explosive blasts for military vehicles during the Iraq War. Big trucks were being blown up, and people are getting injured.

You’re talking about the deck slap injuries? (mentioned earlier)

SKYDEX vehicle decking reduced the blast force transmitted through the floor by 71 percent in live fire testing. (Picture courtesy of SKYDEX.)

Absolutely. That is the key reason why the government ended up contacting us. Again, people were getting injured a lot. As our company had been founded based on energy absorption and impact mitigation with thermoplastic urethane, they asked us to develop some prototypes quickly to be tested. We were able to mitigate over 70 percent of the impact. All that energy that had been transferred to the lower part of your body and was creating a lot of injuries was mitigated with our blast mats. Immediately, the company became a key partner for the government to supply those for several years.

But the military is not your only market, correct?

Correct. As I said, we started in sports and the technology quickly moved into the military. And for several years, the military was the focus of the company. That was all we were doing. When the Iraq War ended, demand basically dried up. We were still supplying blast mats, with over 125,000 total shipped, but the big demand dried up. We went back to our origin.

You went back to sports with the technology developed to help the military? Anything else?

Yes. We asked ourselves, How do we leverage the same type of technology to approach different market sectors? That’s when we started revisiting sports and a few other sectors.

Can you tell us how the material and geometry mitigate the shock?

SKYDEX material used in bomb suits. (Picture courtesy of SKYDEX.)

We used our blast and ballistics knowledge for bomb suits and helmet pads. You’ll find our products in plates for body protection. We also got into marine use, specifically impact mitigation for boats. If you watch the movie Hurt Locker, our product is in that bomb suit. I cannot disclose our customer who makes the bomb suit, but our plate goes inside that bomb suit that went into the movie.

We also got into helmets. We supplied millions of helmet pads for the armed forces over the years. The pads go inside the helmet for protection and comfort. They use a similar technology in our knee and elbow pads, protecting against one big impact or multiple impacts.

What material is used in the blast mats and pads?

We are basically working with a thermoplastic polyurethane. Forming that material into specific geometries makes it suited for a specific type of impact. The material variation combined different shapes gives us an infinite number of possible solutions. That’s the secret sauce for our company. We listen to a customer to understand what their issue is, what kind of impact are they trying to mitigate. Most point back to one impact. We determine the forces they’re dealing with. Then we go back and engineer a solution, which is based on the specific resin, all of that combined with a geometry designed specifically for that application.

Polyurethane has infinite combinations by itself. Different types of resins that you can use, different types of thicknesses, different types of hardnesses. If the product doesn’t need to be comfortable or soft, like a blast mat, we’re going to use a much harder, much firmer polyurethane to be able to absorb the impact. If a pad is wearable, the pad needs to have a comfort level. So, we select the type of film or the type of resin to use based on the application, then depending on the shape that you need to design that solution, we vary the hardness of the material.

Various geometries of blast plates. (Picture courtesy of SKYDEX.)

And then, ultimately, it will be up to the geometry to really deflect or absorb the impact. You can see (picture above) the types of geometries that we have. When you look at those pictures, you might think they are static shapes, but they are dynamic. They are each designed to be able to take the impact and mitigate it or deflect it.

Can your designs take repeated shocks, or are they damaged by shock and have to be replaced?

Some are disposed of. Like the blast mats on military vehicles. Or bulletproof vests. But you’re a runner, so you’ll appreciate our material in shoes that will take multiple impacts, hundreds of thousands of impacts. The durability of this type of product is tremendous. I mean, it basically overdelivers compared to any other alternative material for impact mitigation.

The helmet pads are purely for the armed forces?

Yes, not just the U.S. Army but international armed forces. We have made more than 4 million helmet pads for the armed forces.

The military continues to be the biggest market sector?

It is, but we are taking a special interest in sports now. Our products are in high school 7-on-7 football helmets. We call them soft shell helmets. These are taking a lot of attention. We’re working with several players in that space. Also, we work with other types of helmets, like ski and snowboard helmets … anything that really exposes the user to a potential impact, our technology can play a key role.

Thanks for your time, Alvaro. We’ll be glad to tell our readers of your role in safeguarding our soldiers and athletes. The troops who can walk without pain after a blast owe your company one big “thank you” for developing the blast pad. And good luck in your company’s transition to civilian and sporting life.

Alvaro has been named in our Engineers Who Mattered in 2020 for his role in safeguarding our soldiers and athletes.