An energy-absorbing structure based on honeycombs could be used in the design and production of future vehicles and military gear to improve safety, says new research.

The technology called negative stiffness (NS) honeycombs has been developed by researchers at the Cockrell School of Engineering at the University of Texas (UT). The energy-absorbing structure is able to better withstand blunt and ballistic impact than conventional honeycomb structures and can be integrated into car bumpers, military and athletic helmets and other protective hardware.

The shortcoming of conventional honeycomb structures is that they lose their full protective properties after only one impact and after absorbing the force of one compression do not return to their original shape. However, research shows that the NS honeycomb structures are able to provide repeated protection from multiple impacts, offering more durability than existing honeycomb technology found in a range of products from automobiles to aircraft.

Carolyn Conner Seepersad, mechanical engineering professor at the university who led the work along with research scientist Michael Haberman, said: "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."

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 researchers manufactured 3.5-inch NS honeycomb structures, as well as miniature NS honeycomb cells, from nylon using selective laser sintering for experimentation. However, NS honeycombs can be made from a variety of materials to suit distinct applications.

The cell dimensions can also be customised to withstand different amounts of force for a variety of applications. The current 3.5-inch lab prototype has a force threshold level of 200 newtons - capable of absorbing the energy of a 100 mph ball in 0.03 seconds.

Researchers at UT have said that subsequent custom compression and drop tests, designed and fabricated at the university, have confirmed the NS honeycomb structures' predicted energy-absorbing behaviour and resilience.

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 autumn.