Energy Absorbing Honeycomb Structure Developed in US

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Energy Absorbing Honeycomb Structure Developed in US

 22nd Jun 2015

One of the biggest challenges that have faced the military since the application of firearms is how to keep fighting men and women protected from enemy fire. Earliest examples date back to the 16th Century (with limited success). During the English Civil War Oliver Cromwell’s Ironside cavalry were equipped with musket proof cuirasses (chest plate) which comprised of three layers of armour plate.

History is littered with attempts to develop an effective and affordable defence against ballistic weapons. The British Army Medical Services predicted that 75% of battle injuries sustained to servicemen during World War I could have been prevented by armour. By the end of World War II basic bulletproof vests were appearing in some numbers in the Pacific.

During Vietnam the US used a precursor to the modern body armour but its poor performance made it a bulky and awkward inconvenience rather than a life saving addition to the uniform.


Osprey MKIV Combat Armour currently used by the British Army - Image couresty of the Ministry of Defence

Since that time body armour has been developed and redeveloped each time refinements being made to improve protection, mobility and weight. Current body armour is capable of absorbing significant punishment from small arms but plates are compromised and must be replaced after impact.

Researchers from the Cockrell School of Engineering at the University of Texas in Austin have created a new honeycomb-like structure designed to withstand heavy impacts. Honeycomb structures in defence are nothing new: metal honeycombs are filled with sand or soil for use as barricades. It can also be found in armour plating in armoured fighting vehicles. They are capable of absorbing significant kinetic force but it still has the problem of one use.


Image courtesy of Cockrell School of Engineering at the University of Texas

Unlike this traditional honeycomb structure, the revolutionary negative stiffness (NS) honeycombs developed by the University of Texas have been engineered to provide protection from repeated impacts, returning to their original structure following compression. This not only has potential as body armour that could withstand concentrated and sustained fire, but could be used in helmets ­ civil and military, aviation, armour plating and safety features on automobiles such as bumpers.

Carolyn Conner Seepersad, Mechanical Engineering Professor, from the University of Texas was quoted: ‘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,

‘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 team’s research is focussed on cell geometry capable of elastic buckling; giving the negative stiffness honeycomb structures the ability to recover their energy-absorbing shape and properties after impact. Essentially the structure bounces back after impact.

This isn’t to say bullets will be bouncing off our men and women in uniform but it does dramatically increase their survivability against a concentrated attack i.e. multiple bullet impacts.

Cells can be formatted in a variety of sizes and materials making its applications far reaching. The material will have a direct impact on how durable the structure is which means next generation materials could create almost impervious structures.

Video courtesy of Cockrell School of Engineering at the University of Texas

The prototype made by the team at the University of Texas is made up of 3.5-inch honeycomb structures with a force threshold of 200 Newtons, which the researchers claim is enough to ‘absorb the energy of a baseball travelling at 100mph in 0.03 seconds’.

Negative stiffness honeycomb structures have also been developed from nylon using selective laser sintering for experimentation. Customised compression and drop tests have confirmed the NS honeycomb has behaved as expected.

The next stage of assessment will include ballistic testing, while a combat helmet prototype is expected to be completed later in the year.

There’s no indication from the University of Texas if they have any interest from the DoD or commercial backers but the potential is evident.

If you’re interested in a role in the defence industry or you’re looking for your next career move we’re actively recruiting for a range of positions. Register your details with us today.





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