Natural structures have long inspired human innovations. The bee honeycomb structure, for example, has been applied to products as varied as car bumpers and athletic helmets to absorb impact.

The only drawback to the honeycomb has been its inability to maintain its unique structure after just one hit. The material buckles and doesn’t bounce back.

To solve this problem, researchers in the Cockrell School of Engineering developed a groundbreaking honeycomb-inspired energy-absorbing structure to better withstand blunt and ballistic impact. It’s called a negative stiffness (NS) honeycomb, and it could have huge implications for the design and production of future vehicles, military gear and athletic equipment.

In short, NS honeycombs bounce back when other honeycombs do not.

“Whether you’re serving our country in uniform, playing in a big game, or just driving or biking to work, the potential for multiple collisions or impacts over time — however big or small — is a reality,” says Carolyn Conner Seepersad, professor of mechanical engineering, who led the work along with UT Austin research scientist Michael Haberman.

“We believe that this technology, when constructed in future helmets and bumpers, could reduce or even prevent many of the blunt-force injuries we see today.” —Carolyn Conner Seepersad

The UT Austin team’s research on the innovative structure was published in Integrated Materials and Manufacturing Innovation.

The researchers devised a cell geometry capable of elastic buckling, giving NS honeycomb structures the resilience to recover their energy-absorbing shape and properties after impact. The cell dimensions can be customized to withstand different amounts of force, translating to a variety of versatile applications.

In 2014, the research team received a Small Business Innovation Research Grant from the U.S. Department of Defense. That funding and additional collaboration with the Maritime Applied Physics Corporation, an engineering company that frequently partners with the U.S. military, helped support the advancement of NS honeycomb technology.

The next phase of assessment will include ballistic testing. The researchers are also building a lab prototype of an enhanced combat helmet with NS honeycomb cells integrated that will be completed this fall.

Honeycomb-inspired design. Impact-absorbing tech. Protecting our soldiers and athletes. That’s how we change the world!