The Honeycomb structure. Source: UT News Researchers at the University of Texas, Austin, (UT) have developed an energy-absorbing structure called negative stiffness honeycomb to better withstand blunt and ballistic impact. The honeycombs bounce back or return to their original shape after impact. Conventional honeycomb structures typically lose their full protective properties after one impact.

The new structure can be integrated into car bumpers, military and athletic helmets, and other protective hardware, possibly improving safety.

The cell dimensions can be customized to withstand different amounts of forces. The current 3.5-inch lab prototype, for instance, has a force threshold level of 200 newtons—capable of absorbing the energy of a 100 mph fastball in 0.03 seconds.

The prototype was manufactured from nylon using selective laser sintering for experimentation. However, the negative stiffness (NS) honeycombs can be made from a variety of materials. Subsequent custom compression and drop tests, designed and fabricated at UT Austin, have confirmed the NS honeycomb structures’ predicted energy-absorbing behavior and resilience.

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